Search results for " Flax"
showing 10 items of 21 documents
Evolution of the bearing failure map of pinned flax composite laminates aged in marine environment
2020
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…
A simplified predictive approach to assess the mechanical behavior of pinned hybrid composites aged in salt-fog environment
2020
Abstract Aim of this paper is to assess the predictive capabilities of a simplified theoretical approach on the failure load of aged pinned hybrid composites. In particular, the mechanical performances of glass-flax hybrid epoxy laminates exposed to salt spray fog environment, were used as input data in order to address the analytical model. Preliminarily, the relationship among mechanical performances, failure mechanisms, joint geometry and ageing time, was evaluated by double-lap joint tests on pinned samples at varying joint geometry and ageing time. The bearing and shear out limit stress of samples aged for 60 days under the salt-fog environment underwent a reduction of about 20% compar…
Effect of glass fiber hybridization on the durability in salt-fog environment of pinned flax composites
2021
The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned laminates were exposed to a salt-fog environment for up to 60 days. Double-lap pinned joint tests were performed to assess the pin-hole joints performances at varying the laminate stacking sequence. In order to better discriminate the relationship between the mechanical behavior and the fracture mechanisms of joints at increasing the aging time, different geometries (i.e., by varying both the hole diameter D and the free edge distance…
An Innovative Treatment Based on Sodium Citrate for Improving the Mechanical Performances of Flax Fiber Reinforced Composites
2021
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 …
Mechanical Behaviour of a Green Sandwich Made of Flax Reinforced Polymer Facings and Cork Core
2015
Abstract This work investigates the flexural behavior of a composite sandwich made of flax fibers reinforced skin facings and an agglomerated cork core, to be employed as an eco-friendly solution for the making of structural components of small sailing boats. An experimental mechanical characterization of the strength and stiffness flexural behavior of the proposed sandwich is carried out, providing a comparison of performances from three implemented assembling techniques: hand-lay-up, vacuum bagging and resin infusion. Sandwich beams have been tested under three point bending (TPB) at various span lengths. A procedure is also proposed and implemented to consider the potential influence of …
Durability of flax-basalt hybrid composites for marine applications
2015
The aim of the present work is to evaluate the influence of external layers of mat basalt on the durability behaviour and performances of flax/epoxy laminates. To this scope, long-term aging tests were performed to evaluate the durability of the two different laminates in critical environmental conditions. In particular, Flax composites were constituted by ten layers of bidirectional flax fabric whereas hybrid laminates (i.e. Flax-Basalt) were produced by replacing four external layers of bidirectional flax with four layers of basalt mat. Both laminates had a total average thickness equal to 3 mm. The samples were exposed to critical environmental conditions following the ASTM B 117 standar…
Flax–Glass Fiber Reinforced Hybrid Composites Exposed to a Salt-Fog/Dry Cycle: A Simplified Approach to Predict Their Performance Recovery
2023
Despite natural fibers gaining significant attention in recent decades, their limited performance and poor durability under humid environments cannot allow them to fully replace their synthetic counterparts as reinforcement for structural composites. In such a context, this paper aims to investigate how exposure to a humid/dry cycle affects the mechanical response of epoxy laminates reinforced with flax and glass fibers. In particular, the main goal is to assess the performance evolution of a glass–flax hybridized stacking sequence in comparison with the full glass and flax fiber reinforced composites. To this end, the investigated composites were first exposed to salt-fog for 15 or 30 days…
Failure mechanisms of flax/epoxy laminates with open hole: a failure map
2017
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…
Effect of sodium bicarbonate treatment on mechanical properties of flax-reinforced epoxy composite materials
2017
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 ∼…
Creep Behavior of Poly(lactic acid) Based Biocomposites
2017
Polymer composites containing natural fibers are receiving growing attention as possible alternatives for composites containing synthetic fibers. The use of biodegradable matrices obtained from renewable sources in replacement for synthetic ones is also increasing. However, only limited information is available about the creep behavior of the obtained composites. In this work, the tensile creep behavior of PLA based composites, containing flax and jute twill weave woven fabrics, produced through compression molding, was investigated. Tensile creep tests were performed at different temperatures (i.e., 40 and 60 °C). The results showed that the creep behavior of the composites is strongly inf…