Search results for "progettazione"
showing 10 items of 581 documents
Experimental analysis and micromechanical models of high performance renewable agave reinforced biocomposites
2017
Abstract The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the m…
Effect of hydrothermal ageing on the thermal and delamination fracture behaviour of CFRP composites
2014
Abstract This work investigates the hydrothermal ageing behaviour of a carbon fibre reinforced laminate and its epoxy matrix in bulk conditions. A model DGEBA epoxy is employed, and water uptake and dynamic mechanical thermal (DMTA) analyses have been performed on both the composites and bulk resin. Fracture toughness of the bulk resin has been measured, evidencing a substantially unmodified critical stress intensity factor KIC, although the evidence of plasticisation effects given by DMTA. Interlaminar Mode I fracture toughness of the composite showed a variable trend towards slight decreases or slight increases, according to the prevailing toughening or embrittling mechanisms activated by…
Parameters influencing the stiffness of composites reinforced by carbon nanotubes – A numerical–analytical approach
2014
Abstract Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes may strongly reduce the reinforcing effect of the carbon nanotubes when added to a matrix to create composites. Here the effects of carbon nanotube waviness and the interaction with the matrix on the stiffness of the composite are investigated. Using a mixed numerical–analytical model, a parametric study of the waviness and volume fraction influence of CNTs on the elastic behavior of the nanocomposite is presented. The m…
Novel non-destructive evaluation technique for the detection of poor dispersion of carbon nanotubes in nanocomposites
2019
Abstract A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference …
Detection and characterisation of disbonds on Fibre Metal Laminate hybrid composites by flying laser spot thermography
2017
Abstract In this work a novel data collection and processing is proposed for the Infrared Non-Destructive Testing (IR-NDT) of interlaminar disbonds on Fibre Metal Laminate (FML) hybrid composites. The adopted active IR-NDT scheme uses a pointwise laser heat source that is moved along a raster scanning trajectory over the object surface. A Focal Plane Array IR camera is employed to acquire the thermal field generated by the moving heat source. Disbonds defect signatures are then searched by analysing the perturbations of the temperature distribution over a reference area following the heat source. The proposed methodology has been implemented on a GLARE sample, since this class of FMLs has g…
Deformation analysis of ATHENA test filters made of plastic thin films supported by a mesh under differential static pressure
2019
Within ESA Cosmic Vision 2015-2025 Science Program, ATHENA was selected to be a Large-class high energy astrophysics space mission. The observatory will be equipped with two interchangeable focal plane detectors named X-Ray Integral Field Unit (X-IFU) and Wide Field Imager (WFI). In order to optimally exploit the detector sensitivity, X-ray transparent filters are required. Such filters need to be extremely thin to maximize the X-ray transparency, that is, no more than a few tens of nm, still they must be able to sustain the severe stresses experienced during launch. Partially representative test filters were made with a thin polypropylene film, coated with Ti, and supported by a thin highl…
Effects of Nylon 6,6 Nanofibrous Mats on Thermal Properties and Delamination Behavior of High Performance CFRP Laminates
2014
none 8 no Nylon 6,6 electrospun nanofibrous membranes interleaved in Carbon Fibre Reinforced Plastic (CFRP) laminates have been proposed as a means to provide a higher threshold value to delamination on structural sites where composites are more prone to develop such failure. A model, highly crosslinked thus inherently brittle, epoxy matrix was selected for its high Young’s modulus and glass transition temperature exceeding 250 °C. The influence of the Nylon 6,6 nanofibres on the curing behaviour of the matrix and on the thermal and dynamic mechanical properties of the cured resin was investigated. These properties were related to the features of the epoxy resin and of the resin impregnated…
A methodology for the rapid characterization of Mode II delamination fatigue threshold in FRP composites
2019
Abstract A new methodology to measure the Mode II interlaminar fracture in fatigue for FRP composites is developed. The proposed methodology uses a Modified Transvers Crack Tensile (MTCT) specimen and is able to characterize the near threshold behavior in a robust, easier and significantly faster way than standard procedures. Analytical formulae, able to link the crack growth rate to the load or strain amplitudes, were found and verified, and their importance was explained, in particular, for what concerns the characterisation of the near threshold behavior. Experiments were performed both in load and strain control, while the delamination growth was monitored using different techniques inc…
New concept in bioderived composites: Biochar as toughening agent for improving performances and durability of agave-based epoxy biocomposites
2021
Biocomposites are increasingly used in the industry for the replacement of synthetic materials, thanks to their good mechanical properties, being lightweight, and having low cost. Unfortunately, in several potential fields of structural application their static strength and fatigue life are not high enough. For this reason, several chemical treatments on the fibers have been proposed in literature, although still without fully satisfactory results. To overcome this drawback, in this study we present a procedure based on the addition of a carbonaceous filler to a green epoxy matrix reinforced by Agave sisalana fibers. Among all carbon-based materials, biochar was selected for its environment…
AN ACCURATE METHOD TO PREDICT THE STRESS CONCENTRATION IN COMPOSITE LAMINATES WITH A CIRCULAR HOLE UNDER TENSILE LOADING
2007
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups; in particular, the experimental results have shown that a combined …