New Polylactic Acid Composites Reinforced with Artichoke Fibers

In this work, artichoke fibers were used for the first time to prepare poly(lactic acid) (PLA)-based biocomposites. In particular, two PLA/artichoke composites with the same fiber loading (10% w/w) were prepared by the film-stacking method: the first one (UNID) reinforced with unidirectional long artichoke fibers, the second one (RANDOM) reinforced by randomly-oriented long artichoke fibers. Both composites were mechanically characterized in tensile mode by quasi-static and dynamic mechanical tests. The morphology of the fracture surfaces was analyzed through scanning electron microscopy (SEM). Moreover, a theoretical model, i.e., Hill's method, was used to fit the experimental Young's modu…

Manufacturing of sandwich structures: manual lay up vs vacuum bagging

A review on basalt fibre and its composites

Abstract In recent years, both industrial and academic world are focussing their attention toward the development of sustainable composites, reinforced with natural fibres. In particular, among the natural fibres (i.e. animal, vegetable or mineral) that can be used as reinforcement, the basalt ones represent the most interesting for their properties. The aim of this review is to illustrate the results of research on this topical subject. In the introduction, mechanical, thermal and chemical properties of basalt fibre have been reviewed. Moreover, its main manufacturing technologies have been described. Then, the effect of using this mineral fibre as reinforcement of different matrices as po…

Characterization of blends of polypropylene with a semirigid liquid-crystal copolyester

Abstract Blends with a liquid-crystal polymers (LCP) as one component show, in general, very interesting properties. Reduction of shear viscosity and improvement of mechanical properties are very remarkable. High melting temperatures and high costs of the LCP limit the use of these blends. A new class of thermotropic LCPs with flexible spaces, with relatively low melting temperatures, can overcome the first problem. In this work, rheological and mechanical properties of blends of polypropylene with low contents of this LCP are presented. Torque during extrusion and viscosity decrease with LCP content. Elastic modulus is remarkably increased when the LCP phase is oriented.

The effect of a liquid CTBN rubber modifier on the thermo-kinetic parameters of an epoxy resin during a pultrusion process

Abstract Rheo-kinetic behaviour of an epoxy resin, coupled with an anhydride hardener, with different CTBN liquid rubber concentration (0–15 phr), used in fibre reinforced plastics, was analysed comparing experimental data with theoretical models. The modelling of technological pultrusion process for thermoset matrix composites, developed through a numerical code realised with MATLAB, is reported, too. The model includes conduction and cure heat, degree of cure and viscosity evolution during the curing within the die. Considerable differences in process condition, using different rubber amount, are obtained. The numerical modelling of process conditions shows that the CTBN rubber presence i…

Modelling of phase transitions and residual thermal stress of CTBN rubber modified epoxy resins during a pultrusion process

Abstract The implicit finite difference and fourth order Runge-Kutta method are used both to solve the heat transfer problem in the pultrusion reaction and to calculate the temperature and conversion distributions within a thermoset composite profile. The aim of our work is to study the influence of a rubbery phase added to the epoxy matrix in production conditions. The results have shown that the rubber modified systems have a low exothermic temperature peak value, so that neither the amount of cured resin nor the final product properties are limited. First of all we will show that the phase transition (gelation and vitrification) zones within the die change as the amount of rubber varies …

Bending test for capturing the fractional visco-elastic parameters: theoretical and experimental investigation on giant reeds

In this paper attention is devoted on searching a proper model for characterizing the behavior of giant reeds. To aim at this, firstly, meticulous experimental tests have been performed in the Laboratory of structural materials of University of Palermo. Further, the novel aspect of this paper is that of using an advanced Euler-Bernoulli model to fit experimental data of bending tests. Such a model of continuum beam takes into account different constitutive laws of visco-elasticity, being real materials visco-elastic.

Simulazione del trasferimento di calore e della cura nel processo di pultrusione di una resina termoindurente

Shear characterization of CaCO3-filled linear low density polyethylene

Shear properties of CaCO3-filled linear low density polyethylene have been determined over a wide range of filler loading. The viscosity rises with the filler loading especially at low shear rates and a yield value appears for CaCO3-contents larger than 5%. The decrease of the die-swell ratios of the filled samples indicates a reduction of the melt elasticity.

Salt spray fog ageing of hybrid composite/metal rivet joints for automotive applications

Abstract The present experimental investigation aims to investigate the effect of salt-fog exposition on the mechanical behaviour of composite/metal riveted joints. To this aim, two kinds of joint were exposed to salt-fog environmental conditions according to ASTM B117 standard, for fifteen weeks. In particular, two composite laminates (i.e. glass fibre and carbon fibre/epoxy composites) were used as composite substrate joined with the metal substrate (i.e. aluminium alloy Al 6060). Single-lap shear tests were carried out in order to evaluate the evolution of the mechanical performances and the damage mechanisms of the riveted joints during the ageing exposition. The results evidence that t…

Evaluation and application of Opuntia ficus-indica insulation panel

Today the attention to the building sustainability issue is increasingly important, because of the major responsibility of the buildings field in the environmental degradation: both in terms of energy consumption from non-renewable sources and the raw materials impoverishment. In addition, the level of comfort required by users are growing and the thermal insulation of buildings becomes the key element in the reduction of energy consumption and C02 emissions, both in the case of new construction and existing ones. The thermal insulation of buildings is the key element in the reduction of energy consumption and C02 emissions due to the cooling of building interiors, both in the case of new c…

COMPARISON OF CRIMSON FOUNTAINGRASS AND DISS FIBRES AS AGGREGATES FOR CEMENT MORTARS

The use of natural fibres in cement composites is an expanding research field as their use can improve the mechanical and thermal behavior of cement mortars and reduce their carbon footprint. In this paper two different wild grasses, i.e. Pennisetum Setaceum, also known as crimson fountaingrass, and Ampelodesmos Mauritanicus, also called diss, are used as source of natural fibres for cement mortars. The principal aim is to evaluate the possibility of using the more invasive crimson fountaingrass in place of diss inside cement based vegetable concrete. The two plants’ fibres have been characterized by means of electron microscopy, helium picnometry; moreover, the thermal conductivity of fibr…

Failure map of composite laminate mechanical joints

Sub-micron structured Polymethyl Methacrylate/Acrylonitrile-Butadiene rubber blends obtained via gamma radiation induced “in situ” polymerisation

The morphology and properties of PMMA/rubber blends, obtained through gamma radiation induced “in situ” polymerization of methyl methacrylate (MMA) in the presence of small quantities of an acrylonitrile–butadiene based rubber (ABN), are presented. Different systems have been obtained by irradiating at a fixed irradiation dose rate and temperature, varying the integrated dose. All the blends obtained were characterized with respect to their melt state and solid state dynamic-mechanical response and mechanical tensile properties. In particular, the effect on the blend properties of prolonging the irradiation time was investigated. Furthermore, a morphological characterization through atomic …

Torsional shear strength and elastic properties of adhesively bonded glass-to-steel components

Nowadays glass is widely used in building applications and coupled to steel through adhesive joining. Reliable mechanical characterization of these joints is necessary to design and predict the final structure performance.In this framework, the aim of this paper is to measure the pure shear strength and elastic modulus for design and modelling of adhesive joined glass-to-steel structures.Torsional shear strength and elastic properties of an adhesively bonded glass-to-steel component were measured on several joined steel-to-steel and steel-to-glass samples.An epoxy resin-based adhesive was used as joining material for AISI304 steel and soda-lime glass.The same steel and adhesive were used to…

Submicron structured polymethyl methacrylate/acrylonitrile-butadiene rubber blends obtained via gamma radiation induced ?in situ? polymerization

The morphology and properties of PMMA/rubber blends, obtained through gamma radiation induced “in situ” polymerization of methyl methacrylate (MMA) in the presence of small quantities of an acrylonitrile–butadiene based rubber (ABN), are presented. Different systems have been obtained by irradiating at a fixed irradiation dose rate and temperature, varying the integrated dose. All the blends obtained were characterized with respect to their melt state and solid state dynamic-mechanical response and mechanical tensile properties. In particular, the effect on the blend properties of prolonging the irradiation time was investigated. Furthermore, a morphological characterization through atomic …

Effect of areal weight and chemical treatment on the mechanical properties of bidirectional flax fabrics reinforced composites

Abstract In this paper several bidirectional flax fibers, usually used to made curtains, were employed as reinforcement of an epoxy matrix. Four different laminates were made by a vacuum bagging process, with varying both the areal weight and the treatment of the fabric. These structures were mechanically investigated carrying out both tensile and three point flexural tests. In order to evaluate the effect of the identified variables on the mechanical parameters (i.e. Young modulus and maximum stress) a statistical analysis was performed. Finally, by comparing the flax composite with a glass one, the convenience of the replacement of glass fiber was investigated in term of cost, weight and …

Elongational behavior of low density/linear low density polyethylenes

Rheological data have been collected in isothermal elongational flow for three different types of blends, made from one low density polyethylene and three linear low density samples. In addition to the transient curves, elongation at break data are also reported. The influence of the composition and of the molecular weight of the linear low density polyethylene is discussed.

Natural Fiber-Reinforced Composites

Over the last decade, composites of polymers reinforced with natural fibres have received increasing attention, both from the academic world and from several industries. There is a wide range of natural fibres which can be applied as reinforcements or fillers thanks to their properties and availability; i.e. flax, hemp, jute, kenaf and sisal. Natural fibres are mainly attractive for the following reasons: specific properties, price, health advantages and recyclability. Particularly, industry is getting more and more interested in environment-friendly products and therefore the research on natural fibre based on composite materials is gaining importance. Some of the benefits linked to the us…

Introduzione al volume Economia e gestione dell'innovazione nelle PMI.Percorsi tematici ed esperienze formative del Master EGI

Epoxy resins as a matrix material in advanced fiber-reinforced polymer (FRP) composites

Abstract: This chapter discusses the epoxy resins which, thanks to their good and versatile properties, can be considered nowadays the most important class of thermosetting polymers. In particular the chapter first reviews both the epoxy resins commonly available on the market, including a new class of bio-derived epoxy resins, and the most-used curing agents. it then describes the principal characteristics of the epoxy resins and how it is possible to enhance them by adding several fillers to the epoxy system. Finally, the chapter analyzes the main engineering fields in which epoxy resins find application today and their possible future utilization.

Structural performances of pultruded GFRP emergency structures – Part 1: Experimental characterization of materials and substructure

Abstract This paper presents an experimental study in the field of structures made of pultruded fiber reinforced polymers (FRP) elements to be used for emergency purposes. A preliminary design of a 3D pultruded glass fiber reinforced polymer structure is presented with the mechanical characterization of the constituting elements. The axial and flexural properties of laminate and I-shaped GRFP profiles are discussed considering the short term creep. In a companion paper, the benefits, the limits and the reliability of the structure analyzed for emergency applications are discussed. In details, the numerical structural analysis of the full-scale 3D model is described followed by the experimen…

PLA based biocomposites reinforced with Arundo donax fillers

Abstract In this work, for the first time, a natural and almost inexpensive filler obtained by grinding the culms of Arundo donax was used to prepare PLA based biocomposites. The composites were prepared by melt compounding PLA with A. donax filler (ADF). The influence of the content and size of ADF on the morphology and on the mechanical and thermal properties of PLA–ADF composites was evaluated. Moreover, ADF was extracted from composites to evaluate the effect of processing on morphology and dimensions of the incorporated filler. Furthermore, the experimental elastic moduli of the biocomposites have been fitted, employing two theoretical models, i.e., Hill and Halpin–Tsai. The results sh…

Shear and nonisothermal elongational characterization of a liquid crystalline polymer

A commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240–350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal-nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die-swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low te…

Induced Modification of Flexural Toughness of Natural Hydraulic Lime Based Mortars by Addition of Giant Reed Fibers

Abstract Nowadays, there is a growing need to reduce the environmental impact generated by the use of inorganic materials for building applications. The aim of this work is to investigate the bio-lime based mortar flexural toughness improvement due to the addition of common reed fibers (Arundo donax L.) in order to evaluate their possible application as ductile eco-compatible prefabricated bricks or laying and joint mortars for masonry. Different sets of specimens were tested by varying the fiber weight content and the fiber length. Moreover, chemical treatments with Linseed Oil and Polyethylene glycol (PEG) were performed to improve the physical and mechanical properties of the fibers as w…

Indentazione statica di sandwich compositi per tavole da windsurf

Effectiveness of sodium acetate treatment on the mechanical properties and morphology of natural fiber-reinforced composites

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron micro…

Ottimizzazione di strutture sandwich per applicazioni nautiche

Structural adhesives resins properties for composites joint in marine applications

Rheological properties and morphology in LLDPE and PC based blends

Abstract During an interlaboratory project on polymer blends (Technical Working Party-Polymer Blends-VAMAS), the rheological characteristics of some samples of blends of polycarbonate with linear low density polyethylene have been evaluated with the aid of a capillary rheometer. Some morphological observations on the extruded samples have also been performed through SEM and an attempt has been made to correlate the macroscopic and microscopic results.

Prestress and experimental tests on fractional viscoelastic materials

Creep and/or Relaxation tests on viscoelastic materials show a power-law trend. Based upon Boltzmann superposition principle the constitutive law with a power-law kernel is ruled by the Caputo’s fractional derivative. Fractional constitutive law posses a long memory and then the parameters obtained by best fitting procedures on experimental data are strongly influenced by the prestress on the specimen. As in fact during the relaxation test the imposed history of deformation is not instantaneously applied, since a unit step function may not be realized by the test machine. Aim of this paper, it is shown that, the experimental procedure, and in particular the initial ramp to reach the constan…

Failure mechanisms of flax/epoxy laminates with open hole: a failure map

Aim of this paper is the investigation of the pin/hole contact stress and failure mechanisms of flax/epoxy composite laminates underwent to tensile bearing tests. In particular, the maximum loads and failure modes are evaluated at varying joint geometry. In order to optimize the use of composite materials in structural applications, an experimental failure map, identifying main failure modes of mechanically fastened joints, is obtained by evaluating failure modes (i.e., net tension, shear out, cleavage and bearing) as a function of the pin diameter and the position of the hole from the free edge of the laminate. Main goal of this paper is give a simple experimental methodology to support th…

Constant stretching rate experiments on low density polyethylene

A simple apparatus for elongational test of molten polymers is presented. Its realiability is demonstrated by means of stress growth in constant stretching rate experiments and relaxation test on a low density polyethylene sample.

Caratterizzazione di pannelli sandwich al variare del materiale costituente il core

Sandwich compositi per tavole da windsurf,proprietà a confronto / Sandwich composite for windsurf boards,properties compared

Static indentation on Windsurf-board sandwich panels

Experimental design of the bearing performances of flax fiber reinforced epoxy composites by a failure map

Abstract This paper represents the first effort aimed to the investigation of the pin/hole contact stress and failure mechanisms of epoxy composites reinforced with woven flax fabrics, underwent to tensile bearing tests. In particular, the maximum loads and failure modes are evaluated at varying the laminate geometrical configuration. In order to optimize the use of polymer composites reinforced with flax fibers in structural applications, an experimental failure map, identifying main failure modes of mechanically fastened joints, is obtained as function of hole diameter, distance of the hole from the free edge of the laminate and laminate width. Moreover, a theoretical approach based on th…

Effect of external basalt layers on durability behaviour of flax reinforced composites

Abstract Aim of this work is to evaluate the influence of external layers of basalt-mat on the durability behaviour of flax reinforced epoxy composites. To this scope, long-term ageing tests were performed on two different laminates in critical environmental conditions. The first laminate, named Flax, was constituted by stacking ten layers of bidirectional flax fabrics. The second one, named Flax–Basalt, was produced by replacing two external flax layers with two layers of basalt mat for each side of the laminate. Both laminates were exposed to salt-fog environmental conditions, according to ASTM B 117 standard, for 60 days. Five samples per laminate were removed from salt-fog spray chamber…

Inverse response of polypropylene to gamma radiation under vacuum

Abstract The effect of gamma radiation under vacuum on polypropylene is analysed on the basis of a simple kinetic model. The influence of the irradiation parameters, total absorbed dose and dose rate, on the rates of the main reactions occurring during irradiation, i.e. β-scission, addition to double bonds and termination, is studied. Using kinetic equations, and free radical and double bond balance relationships, we show that it is possible to rationalize the response of polypropylene to gamma radiation. In particular, on the basis of the mathematical solutions of these equations, we obtain the equation of an ‘inversion curve’, implicit function of the irradiation parameters, which gives t…

Dependence of geometrical configuration on mechanical behaviour of GFRP composite sandwiches

Shear viscosity of polybutyleneterephthalate/liquid crystal polymer blends

Viscosity measurements have been carried out on blends of polybuty-leneterephthalate (PBT) and a liquid crystalline copolyesteramide (LCP). The flow curves of the blends with LCP content larger than 20%, show a behavior similar to that of the pure LCP, with a rapid rise of the viscosity at low shear rates. The viscosity-composition curves exhibit a deep minimum at low LCP content which may be mainly attributed to the lack of interactions between the two phases.

A new eco-friendly chemical treatment of natural fibres: Effect of sodium bicarbonate on properties of sisal fibre and its epoxy composites

Abstract Several researchers have shown how sisal fibres possess remarkable tensile properties that yield them good candidates as reinforcement in biocomposite materials. This work aims to evaluate the effect of an eco-friendly and cost effective surface treatment method based on the use of commercial sodium bicarbonate (i.e. baking soda) on properties of sisal fibre and its epoxy composites. In particular, raw sisal fibres were treated with a 10%w/w of sodium bicarbonate solution for different periods (24, 120 and 240 h), at room temperature. Changes occurring in sisal fibres were characterized through scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric…

Gamma radiation of EVA-AA/MMA swollen systems to obtain mechanically improved blends

In this work a "new" way to obtain "compatibilised" blends of rubber-glassy thermoplastic components is presented. Polyethylen-vinyl acetate acrylic acid terpolymer is swollen by methylmetacrylate and the system is irradiated through gamma rays in order to induce polymerisation of the monomer. Solubility and dynamic mechanical tests indicate the formation of a two phase system, even though in presence of strong interactions between the two components. Mechanical tensile behaviour is that of a ductile material with appreciable modulus values.

Molecular modifications—Mechanical behaviour relationships for gamma irradiated LLDPE/PA6 blends

Abstract The molecular modifications, due to γ radiation under vacuum, of linear low density polyethylene/polyamide 6 blends are presented and related to their mechanical behaviour. Solubility and melt viscosity tests indicate that in blends the polyethylene component undergoes mainly crosslinking phenomena, whereas the main effect on polyamide is chain branching. According to these molecular modifications, the most relevant effect is the increase of the tensile modulus for the polyethylene rich blends and the increase of the impact strength for the polyamide rich blends.

Pull-off adhesion of hybrid glass-steel adhesive joints in salt fog environment

The aim of this paper was to evaluate the durability behaviour of glass/steel adhesive joints exposed to salt fog environmental conditions for ten weeks, according to ASTM B117 standard. To this scope, pull-off mechanical tests were carried out in order to evaluate the performances evolution and damage phenomena of the adhesive joints during the ageing exposition. Two different types of adhesives were compared (i.e. epoxy and polyurethane ones). Moreover, the effects of the glass surface condition and the presence of a basalt mat layer within the adhesive thickness were evaluated. The mechanical performances were related with the occurred failure mechanisms. Epoxy-based joints showed higher…

Aging resistance of bio-epoxy jute-basalt hybrid composites as novel multilayer structures for cladding

Abstract Aging resistance of jute reinforced laminates is compared with two jute/basalt hybrid laminates prepared with different stacking sequences (i.e., sandwich and intercalated configuration). To this aim, composites are exposed to cyclic conditions comprising hygrothermal stress and UV radiation to promote an accelerated aging, for a period of 84 days. Specimens of each laminate are tested after 14, 28, 56 and 84 days, respectively. Quasi-static flexural tests, Charpy impact tests and dynamic mechanical tests are performed according to international ASTM and ISO standards. Furthermore, scanning electron microscopy and differential scanning calorimetry are used to evaluate the morpholog…

Influence of long chain branching on the elongational behaviour of different polyethylenes and their blends

Elongational data on a series of polyethylenes with different structure and on their blends are presented in order to correlate the extensional behaviour with the long chain branching degree.

Failure Map of Composite Laminate Mechanical Joint

The aim of this research is to investigate the pin/hole contact stress of a composite laminate and failure modes when submitted to tensile bearing tests. The limit loads and failure modes are evaluated as a function of pin diameter and hole position. Analyzing the joint geometry effect on the fracture mechanisms, a failure map is obtained, identifying three regions of typical failure modes of mechanically fastened joints. A theoretical approach is proposed to identify the field of each fracture mode to obtain a simple experimental methodology to support the design of a particular joint laminate. In addition, a simplified numerical model is proposed to evaluate near the hole the stress/stra…

Flow properties of low density/linear low density polyethylenes

Rheological data have been collected both in shear and non-isothermal elongational flow on three different types of blends, made from one low density polyethylene sample and three linear low density polyethylene samples. In addition to the flow curves, data are presented on the extrudate-swell phenomenon, on the instability arising in capillary flow and on the tensile behavior in the molten state.

Viscoelastic Behavior of an Epoxy Resin Modified with Recycled Waste Particles Analyzed through a Fractional Model

It is well-known that the addition of randomly dispersed particles in polymers influences their linear viscoelastic behavior and dynamic mechanical properties. The aim of this study was to describe the viscoelastic behavior of an epoxy resin modified by waste glass and rubber particles using the linear fractional spring-pot model. Unlike complex classical exponential models, fractional models, being only two-parameter dependent, make it easier to characterize the viscoelastic behavior of materials. Isothermal relaxation and single frequency sweep temperature dynamic tests were carried out in a dynamic mechanical analyzer DMA150 by varying the content of the particles from 0 to 20% by weight…

Physical and structural characterization of blends made with polyamide 6 and gamma-irradiated polyethylenes

Abstract Morphological, calorimetric and rheological results of blends made with polyamide 6 and polyethylene gamma irradiated in air are presented. The polar oxidized groups grafted in the poliolefin chains through gamma-radiation induce “compatibilization” effects in the blends with a more uniform and finer distribution of the polyethylene “phase” in the polyamide matrix, with respect to blends made with the unirradiated polymer. This effect, observed with polyethylenes of different molecular structure, i.e. low density, linear low density and high density, was attributed to the presence of interactions among the functional oxidized groups of the polyethylene chains and the polyamide. Tes…

Shear flow characterization of blends containing liquid crystal polymers

A simple phenomenological approach is proposed in order to predict the presence of minima in the viscosity-composition curves of blends of thermoplastic with liquid crystal polymer (LCP). When the viscosity of the liquid crystal polymer is larger than that of the thermoplastic matrix, a minimum is observed. A possible explanation of the presence of yield stress in the flow curves of these blends is also given.

Embedding Monitoring Systems for Cured-In-Place Pipes

This paper proposes a non-intrusive electrical measurement system for monitoring some relevant parameters in pipeline systems. Temperature and flow-rate are monitored, using MEMS sensors. The flow-rate is evaluated by measuring pipe vibration, with a 3 axis accelerometer, induced by turbulence when fluid flows within the tube. The sensors are embedded, during the curing process of the cured-in-place pipes, in the pipes wall making the system suitable to be installed in renewed or new pipeline. The first experimental results show that it may be possible to obtain, at low-cost, a fully monitored distribution network.

Effect of water absorption on thermal and mechanical properties of thermosetting resins for marine applications

Bearing failure prediction: an experimental versus numerical approach

Influence of resin viscosity and vacuum level on mechanical performance of sandwich structures manufactured by vacuum bagging

The choice of process parameters is critical in optimizing the mechanical properties of sandwich structures produced using the vacuum bagging technique. The aim of this paper is to analyze how the viscosity of the resin/curing agent system and the vacuum level influence the morphology and the mechanical behavior of sandwich beams with composite faces (epoxy resin and glass fiber fabric named COMBI 900) and a PVC foam core. Four different sandwich structures were produced by varying the viscosity of the epoxy resin/curing agent at constant maximum vacuum pressure. Three further structures were manufactured by varying the strength of the vacuum with the resin viscosity maintained constant at …

Effect of sodium bicarbonate treatment on mechanical properties of flax-reinforced epoxy composite materials

This paper deals with the evaluation of the effect of an eco-friendly and cost-effective surface treatment based on the use of sodium bicarbonate on the mechanical properties of flax-reinforced epoxy composites. To this aim, unidirectional fabrics were soaked for five days in 5 and 10% in weight of sodium bicarbonate solution at 25℃. Quasi-static and dynamic mechanical tests were performed and the fracture surfaces of the composites were analyzed through scanning electron microscopy. Results evidenced that this treatment improves the fiber–matrix adhesion thus increasing the performances of the composites. Treating the fabrics with 10% w/w of bicarbonate solution leads to improvements of ∼…

Ottimizzazione delle prestazioni di tangoni in composito in fibra di carbonio/Better performance for carbon fibre composite spinnaker poles

Effect of silane coupling treatment on the adhesion between polyamide and epoxy based composites reinforced with carbon fibers

The increasing efforts aimed to design structures with reduced weight and better mechanical performances has led in recent years to a growing use of fiber reinforced polymer materials in several fields such as marine. However, these materials can be composed of chemically very different elements and, hence, may be difficult to joint. This research aims to improve the adhesion between a thermoplastic matrix of polyamide reinforced with short carbon fibers (PA12-CR) and a carbon fiber reinforced epoxy matrix (CFRP). Two different silane coupling agents, (3-Aminopropyl)trimethoxysilane (AM) and (3-Glycidyloxypropyl)trimethoxysilane (EP), were applied, through the spray deposition method, on th…

Macro-oriented network of liquid-crystalline polyesters: crosslinking induced by g-irradiation and thermally activated reaction.

Abstract The synthesis of a macro-oriented network from liquid-crystalline polymers, bearing pendant groups with unsaturations, is reported. Virgin polymers are processable to obtain oriented samples, e.g. fibres, which may be crosslinked through thermal activation and/or exposure to γ-radiation. The liquid-crystalline state is “frozen” and the macroscopic anisotropy is preserved even at high temperatures. Compared to virgin fibres, irradiated samples show an enhancement of tensile performances, thus indicating that the main effect of irradiation is crosslinking without significant degradation phenomena.

Blends of polyamide 6 and linear low density polyethylene functionalized with methacrylic acid derivatives

Abstract Morphological, calorimetric, rheological, dielectric and mechanical behaviour of blends made with polyamide 6 (PA6) and linear low density polyethylene (PE) are presented. The PE was functionalized grafting ester and alcohol groups in a Brabender mixer with methacrylic acid derivatives. These groups induce “compatibilization” effects in the blends with respect to blends made with the unfunctionalized polyethylene. The difference effects on the behaviour of the blends of the various functional groups are shown. In particular, the interactions at the interface change depending on the chemical nature of the grafted groups. Ethyl and isobuthyl-methacrylate essentially cause dipolar int…

Caratterizzazione di resine adesive per la realizzazione di giunti compositi

Mechanical behavior of carbon/flax hybrid composites for structural applications

In this work, the influence of an unidirectional carbon fabric layer on the mechanical performances of bidirectional flax fabric/epoxy composites used for structural applications was studied. Two different bidirectional flax fabrics were used to produce flax fabric reinforced plastic (FFRP) laminates by a vacuum bagging process: one is normally used to make curtains; the other, heavier and more expensive than the previous one, is usually used as reinforcement in composite structures. In order to realize hybrid structures starting from FFRP, an unidirectional UHM carbon fabric was used to replace a bidirectional flax fabric. Tensile and three-point bending tests were performed to evaluate t…

Arundo Donax particles as reinforcement for PLA based composites

Aim of this work was to use particles obtained by grinding the culms of Arundo Donax used as reinforcement for PLA based composites. The influence of the content (10 wt% and 20 wt%) and size (150-300 μm and 300-500 μm) of Arundo Donax filler (ADF) on the morphology and on the properties of PLA-ADF composites was evaluated. The composites were prepared by melt compounding the PLA with ADF using a co-rotating modular twin screw extruder. For comparison, neat PLA was processed under the same conditions. Both the neat PLA and the composites were characterized by SEM, DSC, tensile and flexural measurements.

Blends of polyamide 6 and bisphenol-A polycarbonate. Effects of interchange reactions on morphology and mechanical properties

Blends of polyamide 6 (PA6) and polycarbonate (PC) were prepared in a Brabender mixer, at 240°C, applying long mixing time, for 45 min. It was observed that the morphology and the mechanical properties tend to resemble those of a homogeneous material as the mixing time and PA6 concentration increase. This is attributed to chemical reactions taking place between the two homopolymers. Acidolysis, amidolysis, and aminolysis, catalyzed by the terminals and the amide groups of the polyamide, should in principle be possible. Our results indicate that the aminolysis is the main process, inducing simultaneously scission of PC chains and formation of PC-PA6 copolymer chains. The latter act as interf…

On the mechanical behavior of BFRP to aluminum AA6086 mixed joints

The aim of this work is to analyze the possibility to join aluminum alloy AA6086 and composite laminates reinforced with basalt fibers, an innovative material which use is growing in several applications as an alternative to glass fibers. To this goal, three joining techniques were investigated: mechanical by Self Piercing Riveting (in the next called SPR), adhesive by co-curing technique and mixed in which the joining techniques (i.e. adhesive and mechanical) were combined. Two manufacturing technologies (i.e. hand lay-up and vacuum bagging) were used both to produce composite substrates and to realize co-curing adhesion between the substrates to be joined. Mixed joints were realized by in…

On the response of flax fiber reinforced composites under salt-fog/dry conditions: Reversible and irreversible performances degradation

Abstract Despite their scarce resistance to humid or wet conditions, natural fiber reinforced composites (NFRCs) seem to be able to partially recover their performances under discontinuous exposition to marine environment. To investigate this peculiarity, flax fiber reinforced composite was at first subjected to salt-fog spray condition at 35 °C for 15 and 30 days, respectively, and then stored in ‘‘dry” condition (i.e., 50% R.H. and 22 °C) between 0 and 21 days. The performances evolution was evaluated through flexural tests, water uptake and contact angle measurements. Moreover, the morphology of fractured mechanical samples was examined by using 3D optical microscope and scanning electro…

Pinned hybrid glass-flax composite laminates aged in salt-fog environment: Mechanical durability

The aim of the present paper is to study the mechanical performance evolution of pinned hybrid glass-flax composite laminates under environment aging conditions. Hybrid glass-flax fibers/epoxy pinned laminates were exposed to salt-spray fog environmental conditions up to 60 days. With the purpose of assessing the relationship between mechanical performances and failure mechanisms at increasing aging time, single lap joints at varying joint geometry (i.e., hole diameter D and hole distance E from free edge) were characterized after 0 days (i.e., unaged samples), 30 days, and 60 days of salt-fog exposition. Based on this approach, the property&ndash

Characterization of a new natural fiber from Arundo donax L. as potential reinforcement of polymer composites.

Abstract The aim of this paper is to study the possibility of using of Arundo donax L. fibers as reinforcement in polymer composites. The fibers are extracted from the outer part of the stem of the plant, which widely grows in Mediterranean area and is diffused all around the world. To use these lignocellulosic fibers as reinforcement in polymer composites, it is necessary to investigate their microstructure, chemical composition and mechanical properties. Therefore, the morphology of A. donax L. fibers was investigated through electron microscopy, the thermal behavior through thermogravimetric analysis and the real density through a helium pycnometer. The chemical composition of the natura…

Indentazione statica su sandwich compositi per tavole da surf/Static indentation on Windsurf-board sandwich panels

Physical and mechanical properties of sustainable hydraulic mortar based on marble slurry with waste glass

This paper aims to propose and characterize a sustainable hydraulic mortar entirely obtained by the reuse of waste materials, with marble slurry coming from quarries in the north-western Sicily and glass powder coming from a waste collection plant in Marsala (Province of Trapani). The first was used as raw material to produce the mortar binder by a kilning and slaking process, while the second was used as a pozzolanic additive. The chemical and morphological characterization of the marble slurry was done by XRD, FTIR, STA and SEM analyses. Glass powder was analyzed through particle size distribution measurements, XRD and standard pozzolanic tests. Hydraulic mortars constituted by slaked lim…

Structure and properties of nylon 6 modified by ?-irradiated linear low density polyethylene

In this work, structure and properties of blends of nylon 6 with 10% linear low density polyethylene γ-irradiated in air at different integrated doses are presented. More particularly, Molau tests, DSC, SEM, and mechanical tests have been performed. Results show that positive morphological changes with respect to the blend with unirradiated linear low density polyethylene are well evident, especially in the blend with polyethylene irradiated at 50 KGy. This blend also shows an enhancement of the elongation at break and of the impact properties.

Windsurf board sandwich panels under static indentation

Characterization of ultra-high-molecular-weight polyethylene (UHMWPE) modified by ion implantation

Abstract Surface modification of ultra high molecular weight polyethylene (UHMWPE) is induced by ion implantation of different ions at 300 keV energy. The aim of this work was the chemical, physical and mechanical characterization of the modified material in order to know deep inside about the effect of the ion beam upon the polymer. The irradiated surfaces are investigated by Raman spectroscopy, infrared absorption and micro-hardness analysis, scanning electron microscopy. Pin on disc measurements valuated the wear of the UHMWPE against a stainless steel probe; wear resistance increases of about 76% after the ion implantation. This result can be attributed to the ion bombardment inducing a…

ECO-FRIENDLY MATERIALS FOR THE ENERGY RETROFIT OF EXISTING BUILDINGS

Today is widely recognized that the main cause of CO2 production and of non-renewable energy consumptions in Europe is due to the building field. For this reason, to improve the energy performance of existing houses through an energy retrofit action (adapting their performances to those required by regulations) is an important strategy to reduce energy consumptions since they are much more than new ones, also representing an economic opportunity. In particular, an important approach in the reducing energy needs consists in the thermal insulation of the envelope, through the application of innovative technologies and materials. The paper will present the result of a research about the possib…

Mathematical modelling of the pultrusion process of polyester-glass fibre composites

Liquid crystal polymer-based blends: “Universal grade” polymers?

Polymeric materials can be easily processed with different processing operations thanks to suitable rheological properties. Melt flow index, or grade, which is a measure of the fluidity of the polymers, is the most commonly parameter used to characterize the polymers from the point of view of their melt viscosity. Injection molding requires high grade materials, whereas low grade values are best suited for extrusion. Of course, it would be no doubt of interest if single “universal grade” materials could be used for all processing operations. In this paper it is demonstrated that the blends of low grade polymers with small amounts of liquid crystal polymers can be conveniently used for all p…

Effect of Sheep Wool Fibers on Thermal Insulation and Mechanical Properties of Cement-Based Composites

The use of sheep wool as a filler of cement in order to produce mortar or plaster involves several advantages for environment and energy. Moreover, it is considered as a waste and, therefore, its use is characterized by low cost. The aim of this paper is to evaluate the influence of wool fibers on thermal conductivity and mechanical properties of cement. The samples were prepared using wool fibers, obtained from a breed of Sicilian sheep, with three different lengths (i.e., 1, 6, and 20 mm). Furthermore, in order to evaluate the influence of fiber content, the samples were prepared by varying the fiber weight fraction. The thermal conductivity of the samples was analyzed by using a heat flo…

Experimental assessment of the improved properties during aging of flax/glass hybrid composite laminates for marine applications

The investigation for natural fibers composites in terms of performance, durability, and environmental impact for structural applications in marine environments is a relevant challenge in scientific and industrial field. On this context, the aim of this work is to assess the durability and mechanical stability in severe environment of epoxy/glass–flax hybrid composites. For the sake of comparison, also full flax and glass epoxy composites were investigated. All samples were exposed to salt–fog environmental conditions up to 60 aging days. Wettability behavior during time was compared with water uptake evolution to assess water sensitivity of hybrid composite configurations. Moreover, quasi-…

Structuring of polymer blends in simple shear flow

A simplified model for the formation of steady state structure of discrete domains in polymer blends is established for simple shear flow. It is assumed that the domain size distribution, which results from an equilibrium between breakup processes and coalescence processes, may be divided in small and stable spherical domains and large and unstable ellipsoidal domains. Based on simplified rate balances and an expression for domain deformation rate the volume fraction of large domains and the large and small semiaxes of the ellipsoids are expressed as functions of volume fraction and shear rate/shear stress. The ability of the model to simulate actual behaviour is tested against quantitative…

Crystallization kinetics of LDPE/Ny6 blends

The crystallization behaviour of low density polyethylene/nylon 6 blends has been investigated as a function of the composition. The melting points of the polymers are almost uninfluenced by the presence of the other homopolymers except for blends with a nylon content of 75–90%. Blends with 10% nylon content do not exhibit the crystallization peak during the cooling step probably because of the low concentration and high viscosity of the low density polyethylene matrix. The crystallinity degree of the polyethylene is independent of the composition, while some variations are shown by the polyamide. Finally the rate of nucleation is strongly affected by the composition, in particular for the …

Three-Point Flexural Behaviour of GFRP Sandwich Composites: A Failure Map

In this work, the failure mechanisms of GFRP/PVC foam core sandwich structures subjected to three-point bending are analysed. By varying the skin thickness (t ) and the span length between supports (l), experimental tests were carried out in order to find the relationship between the geometrical configuration of the sandwiches and the failure mechanism. By plotting failure mechanism on a graph of l against t , a failure map was created identifying the three typical failure mode regions of these sandwiches. The graph clearly shows the failure mode corresponding to each combination of l and t . To help optimise the use of these sandwich beams as structural elements, a theoretical failure mode…

Experimental and numerical evaluation of sandwich composite structures

The main problem working with sandwich composite structures is their intrinsic anisotropy and non-homogeneity that does not allow their correct modelling. Nowadays the available data on mechanical properties of complex structures, necessary to allow a correct and reliable design, are not sufficient. The aim of the present work is to extend the knowledge of mechanical properties both on single components and on complete structures, focusing on the effects induced by different kind of skin arrangements (Kevlar, glass and carbon fibres). Compressive, shear and flexural tests were performed for a complete static mechanical characterisation of the sandwich structure both on each single component…

Melt spinning and mechanical properties of semirigid liquid-crystal copolyesters

Melt-spinning and mechanical properties of fibers of a new class of semirigid thermotropic liquid-crystal polymers are presented. These copolyesters are synthesized from 4-4′-dihydroxybiphenyl (B), 4-hydroxybenzoic acid (H), and flexible units provided by aliphatic diacids. The flexible units depress the melting temperature without strongly depressing the mechanical properties. These liquid-crystal polymers can be easily spun at high draw ratios. Indeed, unlike rigid liquid-crystal polymers, relatively high draw ratios are needed to attain high mechanical strength. Tensile moduli of about 28 GPa and tensile strengths of about 350 MPa are obtained. © 1993 John Wiley & Sons, Inc.

Effects of natural fibres reinforcement in lime plasters (kenaf and sisal vs. Polypropylene)

Nowadays the tendency to realize environment-friendly products is becoming more widespread to ensure sustainable and smart development. The synthetic fibres, frequently used, are harmful to the environment because they are non-degradable and non-renewable. Their use has resulted in an increase of oil consumption. Therefore, the possibility of replacing them with natural fibres becomes increasingly concrete confirmed by the researches and investigations carried out. In this work three lime based plasters were prepared and analysed to evaluate the influence on their performance of different fibres used as reinforcement. In particular each plaster was realised by adding to the mortar the same …

Effect of UD carbon on the specific mechanical properties of glass mat composites for marine applications

In this work the influence of a uniaxial carbon fabric layer on the mechanical performances of a glass mat/epoxy composite used for marine applications has been studied. All the structures have been made, at room temperature, by vacuum bagging technique. Tension and flexural tests have been carried out in order to evaluate the specific mechanical properties of the composite and to compare these with those of the marine aluminium alloy 6016-T4. The glass composites have higher specific strength but lower specific modulus than aluminium alloy. To increase the specific modulus of the composites, each layer of glass mat has been replaced with a layer of uniaxial carbon fabric. In addition, a s…

Better performance of carbon fibre composite spinnaker

Behavior in compression of concrete cylinders externally wrapped with basalt fibers

Abstract This paper gives additional information on the use of new class of composites constituted by Basalt Fiber Reinforced Polymer (BFRP) bonded with epoxy resin to concrete specimens as an alternative confinement material for compressed concrete members with respect to carbon or glass fibers. From the experimental point of view, concrete cylinders are wrapped with continuous fibers, in the form of sheets, applying both full and partial discrete wrapping with BFRP straps, and then tested in compression. For comparison, few other concrete cylinders are wrapped with Carbon Fiber Reinforced Polymer (CFRP) sheets and tested in compression. The number and type of plies (full or partial wrappi…

Liquid crystal polymers (LCP) as processing aids and reinforcing agents. A study of nylon 6/LCP blends

Influence de petites quantites d'un copolyesteramide thermotropique sur les proprietes mecaniques et la mise en œuvre du polyamide 6

On the influence of the initial ramp for a correct definition of the parameters of fractional viscoelastic materials

Creep and/or Relaxation tests on viscoelastic materials show a power-law trend. Based upon Boltzmann superposition principle the constitutive law with a power-law kernel is ruled by the Caputo's fractional derivative. Fractional constitutive law posses a long memory and then the parameters obtained by best fitting procedures on experimental data are strongly influenced by the prestress on the specimen. As in fact during the relaxation test the imposed history of deformation is not instantaneously applied, since a unit step function may not be realized by the test machine. Usually an initial ramp is present in the deformation history and the time at which the deformation attains the maximum …

Reactive dual-component compatibilizers for polycarbonate/high-density polyethylene blends

Enhanced compatibility for blends of polycarbonate with high-density polyethylene has been achieved with the addition of 5 wt% compatibilizers composed of 1 : 1 mixtures of phenoxy and the sodium ionomer of an ethylene methacrylic acid copolymer at two different levels of neutralization. Both components of the compatibilizer have been found to be capable of reacting with the polycarbonate phase to produce branched polymer chains. These impart a degree of compatibilization in polycarbonate/high-density polyethylene blends, however at higher levels of sodium in the compatibilizer the polycarbonate phase undergoes crosslinking reactions, causing severe embrittlement. Compatibilization effects …

Controlling Thermal Flows through Natural Materials in Building Construction Sector

Nowadays, the attention about the building sustainability is increasingly emerging, because of the major responsibility of the building field on the environmental degradation: both in terms of energy consumption from non-renewable sources and the raw materials impoverishment. In addition, the level of comfort required by users is growing and the thermal insulation of buildings becomes the key element for the reduction of energy consumption and CO2 emissions, both in the case of new construction and of the existing ones. The heat load of a building depends on the presence of insulating material which defines the performance of the building envelope. The main purpose of this work is both to i…

Effects of anodizing surface treatment on the mechanical strength of aluminum alloy 5083 to fibre reinforced composites adhesive joints

Abstract In this study, the anodizing process based on the use of tartaric sulfuric acid solution (TSA) was carried out on metal substrate to evaluate for the first time its effect on the adhesion strength and corrosion resistance of aluminium alloy (i.e., AA5083) to fibre (i.e., basalt or glass) reinforced composite adhesive joints for nautical applications. Furthermore, some TSA anodized samples were soaked in a NaOH solution to investigate the influence of this post-immersion step on the joint performances. With the aim to improve the fibre-matrix adhesion in the composite substrate thus further increasing the overall mechanical response of the joint, glass and basalt fibres were treated…

Metal to composite joining through adhesives

Mechanical and Thermal Properties of Insulating Sustainable Mortars with Ampelodesmos mauritanicus and Pennisetum setaceum Plants as Aggregates

The use of natural fibers in cement composites is a widening research field as their application can enhance the mechanical and thermal behavior of cement mortars and limit their carbon footprint. In this paper, two different wild grasses, i.e., Ampelodesmos mauritanicus, also called diss, and Pennisetum setaceum, also known as crimson fountaingrass, are used as a source of natural aggregates for cement mortars. The main purpose is to assess the possibility of using the more invasive crimson fountaingrass in place of diss in cement-based vegetable concrete. The two plant fibers have been characterized by means of scanning electron microscopy (SEM), helium picnometry and thermogravimetric an…

Mechanical properties of basalt fiber reinforced composites manufactured with different vacuum assisted impregnation techniques

Abstract This work describes an experimental mechanical characterisation campaign on composites made out of a quasi-unidirectional basalt fabric. In order to evaluate the ability of commercial basalt fabrics and their composites to meet the potentials of basalt fibers, the work has used raw materials from commercial catalogs with no further modification. Two common manufacturing techniques for medium performance composites have been adopted: vacuum assisted resin infusion, and hand-impregnated vacuum bagging. Two panels, one for each technique, have been fabricated, able to provide a sufficient number of samples for a comprehensive stiffness and strength characterization through Tensile, Fl…

Bending test for capturing the vivid behavior of giant reeds, returned through a proper fractional visco-elastic model

Abstract This paper presents results of experimental investigations made to evaluate the vivid behavior of giant reed Arundo donax. In particular, attention was paid to the relationship between visco-elastic properties and moisture content, which is widely recognized as one of the key factor that influences the mechanical properties of all wood-based materials. To this aim, after a controlled drying treatment on samples of reed, stress relaxation tests in three point bending configuration were performed to evaluate the effects of moisture content on visco-elastic behavior of the giant reed. Further, the novel aspect of this paper is that of using an Euler–Bernoulli model embedded with an ad…

Environmentally Friendly Composites and Surface Treatments for Metal-to-Composite Hybrid Joints for Marine Application

In this study, the use of natural fibres (flax and basalt) in combination with a recyclable epoxy matrix based on cleavable amines is suggested for improving the sustainability of marine industry. In addition, a new and eco-friendly anodizing process based on tartaric sulfuric acid solution (TSA) and a pore widening step in a NaOH aqueous solution was carried out on aluminium alloy (AA5083) to evaluate its effect on the adhesion strength and damage tolerance after low velocity impact of co-cured adhesive joints with a basalt fibre reinforced and recyclable laminate. The durability in marine environment was simulated by exposing samples to salt-fog spray conditions over a period of 90 days. …

Mechanical behaviour and failure modes of metal to composite adhesive joints for nautical applications

In this paper, the influence of several parameters on the mechanical behaviour and failure modes of hybrid bonded joints aluminium/composite was investigated. Particularly, the effects of metallic surface condition, adhesive properties and thickness on single-lap joint resistance were analysed. To these aims, two adhesives were used and, for each adhesive, two different adhesive thicknesses (0.5 and 1.5 mm) have been investigated. Furthermore, two sets of joints for each adhesive kind and thickness were investigated: the former was obtained using aluminium blanks which were previously mechanically treated with sandpaper (P60) and the latter using aluminium treated with sandpaper and with pr…

Effect of plasma treatment on the properties of Arundo Donax L. leaf fibres and its bio-based epoxy composites: A preliminary study

Abstract A preliminary investigation about the effect of plasma treatment on the properties of natural fibres extracted from the leaf of the giant reed Arundo Donax L. and their compatibility with a bio-based epoxy resin is performed. To this aim, the influence of plasma treatment on the functional groups and on the thermal behaviour of fibre were investigated using Fourier transform infrared spectroscopy and thermogravimetric analysis. Moreover, the mechanical characterization of fibres was performed through fibre tensile tests. Short randomly oriented fibres/bio-based epoxy composites were manufactured by hand lay-up method followed by compression moulding, varying both fibres weight cont…

Failure maps to assess bearing performances of glass composite laminates

Aim of this article is the assessment of the bearing mechanical performances of pin-loaded glass laminates as function of their geometrical configuration. To this concern, 32 specimens having different hole diameter (D), laminate width (W), and hole center to laminate free edge distance (E) have been tested under bearing conditions. The maximum bearing stress and the stress-displacement curves were analyzed as function both of hole to laminate free edge distance E and hole diameter D. Moreover, an experimental 2D failure map was created by placing the experimental results (i.e., the kind of failure mechanism occurred for each geometrical configuration) in the plane E/D versus W/D ratios. In…

Structural and Mechanical Modification Induced by Water Content in Giant Wild Reed (A. donax L.)

Giant wild reed Arundo donax L. is an aggressive agricultural species with remarkable features such as fast-growing, untapped economic potential, eco-friendliness, and high specific properties (e.g., high strength/weight and modulus/weight ratios). Here, the bending properties of giant reed were studied at a molecular level to evaluate the effect of the conditions used during the preparation for their applications (also referred to as treatment conditions). The aim was to achieve new information potentially useful to suggest new possible applications of A. donax L. for structural applications in modern buildings. In this study, green reeds collected in a Sicilian plantation were dried for 2…

Bearing strength and failure behavior of pinned hybrid glass-flax composite laminates

Abstract The aim of the present work is to evaluate the influence of external layers of glass woven fabric on the pin-hole strength of flax/epoxy laminates. Single lap bearing tests were carried out to evaluate the fastened joint performances depending on laminate stacking sequence. In order to better identify the mechanical behavior of the hybrid laminate, full glass and flax laminates were also compared. In particular, bearing stress and failure mechanisms were investigated at varying joint geometry. Furthermore, an experimental failure map, clustering main failure modes of pinned hybrid composite laminate, was used to better clarify the relationship between mechanical failure and geometr…

Modellazione del processo di pultrusione di un profilato composito a “C” composto da resina poliestere e fibra di vetro

Effect of Plasma Treatment on Mechanical and Thermal Properties of Marble Powder/Epoxy Composites

The aim of this work was to study the effect of the plasma treatment on the behavior of composite structures reinforced with marble powder, obtained as processing waste in the “Custonaci” basin. Moreover, different filler amounts (i.e. 10%wt, 20%, 30% in weight) were investigated. For the mechanical characterization, tensile and flexural quasi-static tests, Charpy impact test, and dynamic mechanical thermal analysis (DMTA) were performed. For the thermal stability, thermogravimetric analysis was carried out. Finally, real density and fraction of voids were measured. It was observed that untreated marble powder, on one hand, increases tensile and flexural stiffness and improves thermal stabi…

A DIC-based study of flexural behaviour of roving/mat/roving pultruded composites

Abstract This paper reports a study of the flexural behaviour and resultant failure modes in E-glass/polyester pultruded composites. The digital image correlation (DIC) method is used to estimate the effect of fibre orientation on failure behaviour in thick beams, taking into account the presence of continuous filament mat layer (CFM) in the stacking sequence. In particular, the tests were carried out for specimens with off-axis angle of 0°, 7.5°, 15°, 30°, 45° and 90°. The crack initiation and the failure mechanisms depend on the mutual interaction between the stiffness properties of different areas in the stacking sequence. An influence index (I) was introduced to evaluate the magnitude o…

Effects of aging in salt spray conditions on flax and flax/basalt reinforced composites: Wettability and dynamic mechanical properties

Abstract In the last years, the industrial policies are more attentive to issues concerning sustainability, recycling and environmental care. Therefore, the use of natural fibres in composite materials has spread more and more. This paper deals with flax and basalt fibres within an epoxy matrix by investigating the wettability and the dynamic mechanical properties of the resulting composites, subjected to long-term aging tests in critical environmental conditions. The first laminate was constituted by stacking ten layers of bidirectional flax fabrics. The second one was produced by replacing two external flax layers with two layers of basalt mat, for each side of the laminate. Both laminate…

Static and dynamic mechanical properties of Arundo Donax fillers-epoxy composites

Abstract Aim of this work is to investigate the feasibility of using a natural and inexpensive filler obtained by grinding the culms of Arundo Donax as reinforcement of epoxy resins. The effect of the content and size of Arundo Donax fillers on static and dynamic mechanical properties was evaluated showing that the composites exhibit higher tensile moduli, comparable flexural moduli and lower strength properties in comparison to the neat resin. Moreover, changes in the storage and the loss moduli only above the glass transition temperature (i.e. in the rubbery region) were found while neither significant shifts of tan δ peaks to higher temperatures nor reductions in the peak height of the c…

An aging evaluation of the bearing performances of glass fiber composite laminate in salt spray fog environment

The aim of the present paper is to assess the bearing performance evolution of pinned, glass-composite laminates due to environmental aging in salt-spray fog tests. Glass fibers/epoxy pinned laminates were exposed for up to 60 days in salt-spraying, foggy environmental conditions (according to ASTM B117 standard). In order to evaluate the relationship between mechanical failure mode and joint stability over increasing aging time, different single lap joints, measured by the changing hole diameter (D), laminate width (W) and hole free edge distance (E), were characterized at varying aging steps. Based on this approach, the property-structure relationship of glass-fibers/epoxy laminates was a…

Glass/basalt hybrid sandwiches for nautical applications

A comprehensive experimental study of the rheological behaviour of HDPE.

Extensional properties of four high density polyethylenes with different molecular weights and molecular weight distributions are presented. The samples have already been well characterized in shear and non-isothermal extensional flow. The data were collected at 180 °C for elongational rates between 3 · 10−1 and 10−4s−1. Some qualitative and quantitative generalizations of the results are given.

The durability of basalt fibres reinforced polymer (BFRP)

The technology of dry assembly for the production of multi-layer panels has evolved over the past 30 years, becoming an efficient alternative to traditional systems. The direction taken by the market has been increasingly drawn to eco-sustainable systems and in this way, the interest in the use of laminated composite panels for cladding, basalt fibres based. Basalt is a natural rock, silica based, which is produced through a variety of industrial processes into filaments, wool, chopped strands and fabrics. It is characterized by high resistance in chemically aggressive environments, high fire resistance, high mechanical resistance to compression and bending. The study focuses on two types o…

Influence of molecular parameters on the elongational behaviour of different polyethylenes and their blends

Elongational data on a large number of polyethylene samples with different structures and their blends are presented in order to evaluate the influence of the molecular weight and molecular weight distribution for a given degree of long chain branching. The elongational viscosity rises with the number of branch points and also with molecular weight and molecular weight distribution. Simple relationships between elongational viscosity at a given deformation and molecular parameters are presented.

The Transverse Crack Tension test revisited

Several problems arise when measuring the mode II interlaminar fracture toughness using a Transverse Crack Tension specimen; in particular, the fracture toughness depends on the geometry of the specimen and cannot be considered a material parameter. A preliminary experimental campaign was conducted on TCTs of different sizes but no fracture toughness was measured because the TCTs failed in an unacceptable way, invalidating the tests. A comprehensive numerical and experimental investigation is conducted to identify the main causes of this behaviour and a modification of the geometry of the specimen is proposed. It is believed that the obtained results represent a significant contribution in …

On the compatibilization of PET/HDPE blends through a new class of copolyesters

Polyethyleneterephthalate (PET) and polyethylene are incompatible polymers and their blends show, in general, poor properties. Compatibilization is then a necessary step to obtain blends with good mechanical and barrier properties. In this work different compatibilizing agents were used, i.e. a maleic anhydride elastomer and some new products containing graft-copolymers having polyester segments grafted onto polyethylene backbone chains. Both the functionalized elastomer and the new products drastically improve the morphology and the ductility of the blend. In the case of the modified elastomer the compatibilizing action has been attributed to the formation of H-bonds whereas the copolymers…

Biocompositi a base di PLA rinforzati con cariche lignocellulosiche ricavate dalla canna comune

Effect of CTBN rubber inclusions on the curing kinetic of DGEBA–DGEBF epoxy resin

Abstract The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA–DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0–10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calori…

FORMULATION OF LIME MORTARS BASED ON NATURAL FIBERS AND WASTE MATERIALS FOR MORE SUSTAINABLE BUILDINGS

Nowadays sustainability is one of the main concept in building construction, both considering energy saving buildings and life cycle assessment of building materials. According to these considerations, in this work the use of recycled and waste materials to produce a binder and the use of a natural fiber as reinforcement are investigated to obtain a sustainable mortar. Particularly, lime is obtained by kilning waste marble slurry from marbles quarries in western Sicily; pozzolanic aggregate is obtained by grinding glass powder from urban waste collection; natural fibers come from a widespread grass: Ampelodesmos Mauritanicus also known as diss. Scanning electron microscopy and helium picnom…

An Innovative Treatment Based on Sodium Citrate for Improving the Mechanical Performances of Flax Fiber Reinforced Composites

The goal of this paper is to evaluate the effectiveness of a cost-effective and eco-friendly treatment based on the use of sodium citrate (Na3C6H5O7) on the mechanical properties of flax fiber reinforced composites. To this scope, flax fibers were soaked in mildly alkaline solutions of the sodium salt at different weight concentration (i.e., 5%, 10% and 20%) for 120 h at 25 °C. The modifications on fibers surface induced by the proposed treatment were evaluated through Fourier transform infrared analysis (FTIR), whereas scanning electron microscope (SEM) and helium pycnometer were used to obtain useful information about composites morphology. The effect of the concentration of the treating …

Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer

Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrilla…

Structural Performances of Composite Pultruded GFRP Emergency Structures

The use of composite FRP pultruded elements in civil constructions is nowadays widely accepted as a valid alternative to classic materials. In the case of emergency applications (as for temporary shelter after earthquakes, floods and all disastrous), the lightness, ease of transport, assembly, safety of use, possibility of disassembly and reuse are key aspects that composite FRP structures can provide easily.

Theoretical and experimental analysis of viscoelastic behavior of biomaterials

Comparisons of processing and strength properties of two adhesive systems for composite joints

Abstract In the present study rheological, static and impact tests are carried out on two adhesive resins usually employed in marine applications; then single lap joint tests are conducted on composites joints evidencing the effect of the curing time of both resins on the mechanical properties of the joint. The applicability and workability conditions of the adhesive resins are determined evaluating the curing evolution by a preliminary rheological analysis; then the relation of curing properties with the mechanical performances of the resins themselves and with ones of the composite joints is estimated. Static flexural and Izod impact tests are performed on the resins at increasing time af…

Influence of morphology and chemical structure on the inverse response of polypropylene to gamma radiation under vacuum

Abstract In this work the influence of the chemical structure and of the morphology on the gamma-radiation effects on polypropylene based polymers is studied on the basis of a previously discussed kinetic model [1] . For this aim an isotactic polypropylene and a random ethylene–propylene copolymer were irradiated under vacuum at one dose rate and several absorbed doses after well defined solidification conditions. We show that the model is reliable varying both the chemical structure and the morphology of the polypropylene based polymer. An inversion of the response of the material to gamma radiation under vacuum is always observed, and the inversion conditions depend on the irradiation par…

The assessment over time of the performance of jute-basalt hybrid composites for cladding panels

The technology of dry assembly to produce multi-layer panels is an efficient alternative to traditional systems. Eco-sustainable systems are increasingly studied, particularly fiber reinforced composites for external cladding, based on natural fibers. Nevertheless, durability data on these composites are still lacking, being this is a really actual theme, especially for their potential use in outdoor applications. In this way, hybridization of natural fibers with mineral fibers as basalt ones appears promising. In the present paper, the performance of jute-reinforced laminate was compared with those of two jute/basalt reinforced hybrid laminates. The laminates were manufactured by means of …

Glass-basalt/epoxy hybrid composites for marine applications

Abstract The aim of this work is to evaluate the influence of uniaxial basalt fabric layers on the mechanical performances of a glass mat/epoxy composite used for marine applications. Polymer composites, reinforced by glass mat (GFRP), and hybrid ones, reinforced by glass mat and unidirectional basalt fabric, have been produced by vacuum bagging technique. Three points bending and tensile tests have been carried out in order to evaluate the effect of number and position of basalt layers on the mechanical properties of the investigated structures. The experimental tests have showed that the presence of two external layers of basalt involves the highest increase in mechanical properties of hy…

In situ monitoring of moisture uptake of flax fiber reinforced composites under humid/dry conditions

The use of green materials such as natural fiber-reinforced composites represents an increasingly stringent prerogative in the future planning of industrial and non-industrial production. The optimization of these materials is the main aim of the current research, focused on the evaluation of the behavior of flax fiber reinforced composites exposed to isothermal adsorption and desorption cycles, at varying the partial pressure of water vapor (P/P0). For this purpose, the moisture uptake and the morphology changes of the composite material and their constituents were in situ monitored through a measurement protocol, by using a dynamic vapor sorption (DVS) analysis, coupled with an environmen…

Rheological behavior of a semirigid liquid crystal polymer

The rheological behavior of liquid crystal polymers is still far from completely clarified from both experimental and theoretical points of view. In this paper, the shear flow and the non-isothermal elongation flow behavior of a semi-rigid liquid crystal copolyester is discussed. The viscosity strongly decreases when the test temperature is increased above the crystal-nematic transition temperature; below this temperature the viscosity is very high. The thermal history strongly affects the shear viscosity. The elongational flow behavior depends also on temperature. Above the crystal-nematic transition temperature and the mesophase is easily spinnable, whereas below this temperature, the spi…

Evaluation of the temperature effect on the fractional linear viscoelastic model for an epoxy resin

The paper deals with the evolution of the parameters of a fractional model for different values of temperature. An experimental campaign has been performed on epoxy resin at different levels of temperature. It is shown that epoxy resin is very sensitive to the temperature.

INDUCED MODIFICATION OF FLEXURAL TOUGHNESS OF BIO-LIME BASED MORTARS BY ADDITION OF GIANT REED FIBERS

Fibers are often used as reinforcement of brittle materials, like mortars, in order to modify their mechanical behavior; particularly the modification in post-cracking toughness, induced by low elasticity modulus fibers in the artificial stone material, is the main goal in natural fibers mortar manufacturing. In this work Arundo donax L. fibers are used to reinforce lime mortars according to the characteristics of this plant, very commonly available and with high mechanical properties, similar to bamboo, traditionally used in buildings in Spain. Influence of fibers’ length and weight ratio is studied. Particularly, three different fibers’ lengths, 4, 8 and 12 centimeters, and three weight r…

Micro‐tomographic characterization of composite recycled glass‐silicone foams for applications in civil engineering

Noninvasive X‐ray micro‐computed tomography was applied for a complete quantitative and qualitative analysis of the cellular structure of composite foams constituted by a silicone matrix and a glass production waste filler. Composite foams with different glass filler weight content in the range 0–80% were synthesized and characterized. The tomographic analysis was employed in order to assess the structural heterogeneities, void fraction values, and bubble size distribution for all composite foams. The 3D micro‐CT images analysis, performed at different cross‐sections, highlighted heterogeneous cell growth or more elongated cells in the case of low and high filler content foams, respectively…

Effect of curing time on the performances of hybrid/mixed joints

Abstract The aim of this work is the study of a mixed method used for the joining of aluminum alloys with glass reinforced polymer’s substrates (in the next GFRP). In particular, the technique of self-piercing riveting (in the next SPR) was applied on a co-cured joint in order to evaluate the influence of the time of inserting the rivet on the mechanical behavior of the mixed joints. Three different joints were realized: adhesive by co-curing technique, mechanical by self piercing riveting (in the next SPR) and a mixed one in which the joining techniques (i.e. adhesive and mechanical) were combined. In particular, to determine the optimum time to insert the rivet, three different times from…

Characterization of blends with polyamide 6 and ethylene acrylic acid copolymers at different acrylic acid content

In this work the morphological, calorimetric, rheological and mechanical behaviour and fourier transmission infrared analysis of blends made with polyamide 6 (PA6) and ethylene acrylic acid copolymers (EAA) containing different amount of acrylic acid were investigated. The results observed from the sample characterizations evidenced as acrylic acid cause a compatibilizing effect between polyethylene and polyamide components with modifications of blends morphology and mechanical behaviour. These effects are enhanced with increase of the acrylic acid content in the copolymer and they were attributed generally to hydrogen bond interactions among the acrylic acid group and the functional groups…

Rheology-morphology relationships in nylon 6/liquid-crystalline polymer blends

Extrusion measurements have been carried out on blends of nylon 6 and a liquid-crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.

Performances Recovery of Flax Fiber Reinforced Composites after Salt-Fog Aging Test

In the present paper, the performance recovery under conditions of discontinuous exposure to a marine environment of a natural fiber-reinforced composite (NFRC) reinforced by flax fibers was assessed. In particular, this laminate was initially exposed to salt-fog for 15 and 30 days, and then stored in a controlled air condition for up to 21 days. The flax fiber-reinforced composite showed coupled reversible and irreversible aging phenomena during the wet stage, as well as evidencing a significant mechanical recovery during the dry stage. Unlike the stiffness, the laminate showed a noticeable recovery of its flexural strength. This behavior affected the composite material toughness. A simpli…

Geometry and stacking sequence effect on composite spinnaker pole’s stiffness: experimental and numerical analysis

Composite materials are widely employed in sailing sports, a possible application is for the mast pole or other sail poles. In the paper the attention is focused on the spinnaker poles mechanical performances; in particular the focus is on axial and ring compressive properties of three different carbon fibre/epoxy resin spinnaker poles, to investigate both the diameter and stacking sequence effect on the mechanical performance of the structure. Starting from the stacking sequence used in the production of a particular spinnaker pole, the effect of a lamina at 0- in the middle of wall thickness is investigated with the purpose to obtain a more stiff structure. Moreover to test the proposed s…

Structural performances of pultruded GFRP emergency structures – Part 2: Full-scale experimental testing

Abstract This paper presents an experimental testing of a pultruded glass fiber reinforced polymer (FRP) structure used for emergency applications continuing the discussion presented in a previous paper (part 1) where the study of the characteristics of material and elements are presented. First, the design of the composite structure and components and the evaluation of the structural behavior by means of numerical and analytical approach according to current regulatory codes are described. In this frame, the global and local response was observed according to load paths deriving from the design loads at limit states. Then, the experimental test on a full-scale 2D model is presented at diff…

Blends of nylon 6 with a polyethylene functionalized by photooxidation

An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved b…

Thermal and rheological characterisation of a thermoset matrix for filament winding modelling

Rheo-kinetic behaviour of an epoxy resin, coupled with an aliphatic polyamines hardener, used in fibre reinforced plastics, was analysed comparing experimental data to theoretical models. Then the modelling of technological filament winding process for thermoset matrix composites, developed through a numerical code realized with MATLAB, is reported. The model includes winding and curing phase decoupling the manufacturing process into sub-models. Four sub-models are used: fibre motion, thermal, kinetic and rheological model. Considerable differences are obtained in process condition, using several thermal treatments. The numerical modelling helps to detect the process conditions to optimise…

Evolution of the bearing failure map of pinned flax composite laminates aged in marine environment

Abstract Aim of the present paper is to evaluate how the bearing behavior of pinned flax composites can be influenced by their exposition to critical environment such as marine one. To this scope, flax fibers/epoxy pinned laminate was exposed up to 60 days to salt-fog environment, according to ASTM B 117 standard. In particular, samples having different hole diameter (D), laminate width (W), and hole center to laminate free edge distance (E) have been tested under single lap bearing tests at varying the aging exposition time. Following this procedure, an experimental 2D failure map clustering main failure modes was created by placing the experimental results in the plane E/D versus W/D rati…

Modellazione del processo di pultrusione per un composito a matrice poliestere

Artichoke (Cynara cardunculus L.) fibres as potential reinforcement of composite structures

Abstract The aim of this paper is to examine the use of artichoke fibres as potential reinforcement in polymer composites. The fibres are extracted from the stem of artichoke plant, which grows in Southern Sicily. In order to use these lignocellulosic fibres as potential reinforcement in polymer composites, it is fundamental to investigate their microstructure, chemical composition and mechanical properties. Therefore, the morphology of artichoke fibres was investigated through electron microscopy, the thermal behaviour through thermogravimetric analysis and the real density through a helium pycnometer. The chemical composition of the natural fibres in terms of cellulose, lignin, and ash co…

Evaluation of aging behavior under salt-fog spray conditions of green sandwich structures

In this paper, the aging resistance of sandwich structures made with cork agglomerate as core and flax-reinforced polymeric laminates as face sheets was investigated for the first time. In order to evaluate their durability in a hostile environment, a sandwich plate was manufactured by vacuum bagging technique and aged under salt-fog spray conditions, according to ASTM B 117 standard. The evolution of the sandwich mechanical properties during the aging exposition was analyzed by carrying out quasi-static flexural tests and Charpy impact tests both on unaged specimens and on specimens aged for 10, 25, and 60 days, respectively. The quasi-static experimental results showed that despite the sa…

Polymer blends can undergo, during processing, degradation phenomena because of the presence of both temperature and mechanical stresses. With respect to pure homogeneous polymers, the degradation of polymer blends shows distinct features because of the possible interaction between the different chemical species. These interaction can give rise to both a faster degradation or to the formation of copolymers which act as stabilizing agents. This latter phenomena is particularly important in the processing of condensation polymers

Artichoke fibres as potential reinforcement of composite materials: mechanical and thermal characterization

Structural induced modifications in blends of polyamide with gamma irradiated low density polyethylene

Abstract Blends of gamma irradiated and unirradiated low density polyethylene and polyamide 6 were made in order to study possible modifications induced by this irradiation. Results indicate that blends with gamma irradiated polyethylene have structure and properties significantly different with respect to blends made with the unirradiated one. This difference has been ascribed to the formation of functionalized groups in the polyethylene chains, which interact with polyamide.

SISTEMA LEGANTE IDRAULICO PER L’EDILIZIA DA MATERIALI DI SCARTO

A Study of Polycarbonate-Liquid Crystal Polymer Blends

BThe morphologican and mechanical properties of blends of bisphenol-A polycarbonate (PC) with a wholly aromatic liquid crystal copolyesteramide (Vectra-B) are discussed with reference to the conditions used for their preparation. The blends made by extrusion behave as mixtures of incompatible polymers. THe behaviour of the blends prepared in a batch mixer depends strongly on mixing time. A slight decrease in the mechanical properties accompanies the morphological changes associated with a progressive improvement in the compatibility of the two polymers

Studio sperimentale dell’effetto dei parametri geometrici e di processo sulle performance meccaniche di sandwich compositi

Processing and properties of blends with liquid crystal polymers

Experimental data on the processing behavior and on the rheological and mechanical properties of blends with a liquid crystal polymer as one component are presented. The blends with low amounts of LCP show easier processability and lower viscosity than the thermoplastic matrix. The elastic modulus is also improved. The reduction of viscosity has been attributed to the lower pressure entry, due to the formation of fibrils and to the immiscibility of the two phases.

Nonisothermal elongational behavior of blends with liquid crystalline polymers

Measurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity-temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.

Influence of the irradiation parameters on the molecular modifications of an isotactic polypropylene gamma-irradiated under vacuum

Isotactic polypropylene was irradiated under vacuum in a complete set of experimental conditions. The influence of the irradiation parameters, total absorbed dose, D, and dose rate, I, was analysed in order to verify the theoretical predictions of a simple kinetic model, already presented (Sarcinelli L, Valenza A, Spadaro G. Polymer 1997;38:2307), based on the rates of the main reactions occurring during irradiation, i.e. β-scission, addition to double bonds and termination. The concentration of free radicals and double bonds formed during irradiation is detected together with a comparison to their dependence on the irradiation parameters. A quantitative determination of the “inversion curv…

Long-term thermomechanical degradation of molten polystyrene

Abstract Rheological data on polystyrene samples processed for long periods under various mechanical stresses are presented. The data indicate that thermomechanical degradation occurs and that the rate of thermal degradation is increased by the applied stress. Moreover degradation does not reach a limiting value even at high processing times.

Radiation grafting functionalization of poly (vinylidene fluoride) to compatibilize its blends with polyolefin ionomers

Blends of a crystalline vinylidene fluoride copolymer (PVDF) and a polyolefin ionomer were produced by melt mixing and characterized by a variety of techniques to examine the effect of increasing the level of salt formation on morphology. The PVDF component was also grafted with methacrylic acid by irradiating the polymer powder and subsequently treating it with an aqueous monomer solution. The effect of neutralizing the acid in both polymer components to produce the corresponding zinc salt was also investigated. Compatibilization was accomplished by the addition of zinc acetyl acetonate (ZnAcAc) to the mixture. This increased the viscosity of the polyolefin ionomer phase, comparable to tha…

The durability of basalt fibres reinforced polymer (BFRP) panels for cladding

The study focuses on two basalt composite laminate panels for cladding, produced by means of vacuum bagging technique. In particular, unidirectional and random basalt fabrics, with different areal weights, using epoxy resin as matrix, were used. According to the ISO 15686 methodology for the evaluation of durability, samples were subjected to cycles of artificial aging in climatic chamber and outdoor exposure, carrying out mechanical (i.e. quasi-static and dynamic) and calorimetric tests. The results show the effectiveness over time of produced basalt composite laminates and the initial increase of the mechanical performances after the first steps of accelerated aging.

Mechanical properties-structure relationship in blends of polyamide 6 with γ-irradiated LDPE

Blends of γ-irradiated and unirradiated low density polyethylene with polyamide 6 were made in order to study possible modifications induced by this irradiation. Blends with γ-irradiated polyethylene show structure and properties significantly different with respect to blends made with the unirradiated polyethylene. In this paper data on mechanical properties (tensile and impact) of these blends are presented. Results are related to the different morphologies in the blends.

Visco-elastic behavior through fractional calculus: an easier method for best fitting experimental results

In capturing visco-elastic behavior, experimental tests play a fundamental rule, since they allow to build up theoretical constitutive laws very useful for simulating their own behavior. The main challenge is representing the visco-elastic materials through simple models, in order to spread their use. However, the wide used models for capturing both relaxation and creep tests are combinations of simple models as Maxwell and/or Kelvin, that depend on several parameters for fitting both creep and relaxation tests. This paper, following Nutting and Gemant idea of fitting experimental data through a power law function, aims at stressing the validity of fractional model. In fact, as soon as rela…

The effect of alkaline treatment on mechanical properties of kenaf fibers and their epoxy composites

Abstract In this work, kenaf fibers were pre-treated in a NaOH solution (6% in weight) at room temperature for two different periods (48 and 144 h). The chemical treatment of kenaf fibers for 48 h allowed to clean their surface removing each impurity whereas 144 h of immersion time had detrimental effect on the fibers surface and, consequently, on their mechanical properties. Untreated and NaOH treated kenaf fibers (i.e. for 48 h) were also used as reinforcing agent of epoxy resin composites. The effect of the stacking sequence (i.e. using unidirectional long fibers or randomly oriented short fibers) and the chemical treatment on the static mechanical properties was evaluated showing that t…

INFLUENCE OF CORK POWDER GRAINSIZE IN THERMAL AND MECHANICAL PROPERTIES OF CORK-NHL MORTARS

Cork is a unique material, characterized by small closed cell structures, high insulating properties, very low density, high fire resistance and a very good durability after simple thermal treatment. The main use of cork in the production of stopper and insulating panels obtained with cork grains and a polymeric resin. Usually cork grains used in panel production have a grainsize around 1-2 mm. In this work cork grains have been used as aggregates for natural hydraulic lime mortars by reducing grainsize distribution. Cork grainsize has been reduced by means of a knife mill and divided in three different distributions, i.e. 1, 0.5 and 0.25mm. Mortars have been prepared according to NHL to co…

Gamma radiation induced maleation of polypropylene using supercritical CO 2 : preliminary results

Abstract The charging of maleic anhydride (MA) and dicumyl peroxide (DCP) into polypropylene matrices has been carried out by CO2 in supercritical conditions. The grafting of MA into polymer chains was done through gamma irradiation in CO2 atmosphere (0.1 MPa, 25°C). The grafting was successful and the amount of grafted anhydride was dependent on the amount of MA and DCP charged into the polypropylene matrix. The presence of grafted succinic anhydride was shown by FT-IR spectroscopy and its amount was determined through a calibration curve derived from standard samples. The effect of swelling due to supercritical CO2, maleic anhydride grafting and gamma irradiation on the molecular structur…

High energy radiation cure of resin systems for structural adhesives and composite applications

Abstract Radiation cure polymerisation of a commercial diglycidyl ether of bisphenol F epoxy resin has been achieved using a 60Co irradiation source, compounding the monomer with few percentage of an onium salt catalyst. The cure process has been monitored by a gamma-calorimetric technique and systems irradiated at doses corresponding to different positions in the gamma-calorimetric curve have been characterised via solubility tests and dynamic mechanical torsion analysis. Changes in both the measured gel fractions and tan δ values were associated with the progress of polymerisation and crosslinking reactions and these were dose dependent. Furthermore, systems irradiated at lower doses exhi…

Rheological behavior and thermal stability of poly(phenylene sulfide)/vectra-B950 blends

Blends of polyphenylene sulfide (PPS) with a commercial, wholly aromatic, liquid crystalline polymer (LCP), Vectra-B950, have been prepared by melt-blending. Their rheological behavior has been studied in order to determine if the LCP displays a processing aid ability, and under what conditions it gives rise to potentially reinforcing fibrils dispersed in the PPS matrix. The problem of the thermal stability of PPS/LCP blends, which has been considered by some authors as the main obstacle to the production of usable materials due to the evolution of gaseous substances during processing, has been discussed. © 1994 John Wiley & Sons, Inc.

Experimental assessment of the shield-to-salt-fog properties of basalt and glass fiber reinforced composites in cork core sandwich panels applications

Abstract In this paper, the effect of salt-fog exposition on the mechanical behavior of sandwich panels having cork agglomerate core was investigated. In particular, the aim of this research work is to assess the shield function of unidirectional basalt and E-glass reinforced polymer on the aging and failure mechanism of the core when such class of material are destined to operate in hostile environments (e.g., marine environment). To do this, the manufactured sandwich panels were exposed up to 60 days to salt-fog environment, according to ASTM B 117 standard. Unaged and aged specimens were analyzed through three point bending tests after aging time of 10, 25 and 60 days. Digital Image Corr…

Properties and morphology of PMMA/ABN blends obtained via MMA in situ polymerisation through γ-rays

Abstract Methylmethacrylate polymerisation in the presence of 4 wt% butadiene-acrylonitrile rubber was carried out at fixed dose-rate and temperature. The effect of irradiation was investigated with respect to the mechanical and dynamic-mechanical properties in the solid state. A general increase of the “compatibilisation” on irradiation is obtained. In fact both rubber and polymethylmethacrylate glass transition temperatures, determined through dynamic-mechanical analysis, reveal the presence of strong interactions between the components. Furthermore an improvement of the mechanical tensile properties of the blends is observed when irradiation is continued after polymerisation, at least un…

Analisi reologica di una resina epossidica utilizzata come adesivo per giunzioni miste

Study of Snowboard Sandwich Structures

The aim of the present research is to extend the knowledge of mechanical properties both on single components and on complete structure employed for snowboard. Flexural and torsion tests are performed to acquire important comparison parameters between snowboard sandwich structures that differ for the core material employed (wood, PVC foam core). A simplified FEM model is proposed to simulate the flexural tests of the sandwich structure showing good predictive capability.