The mechanical properties of woven composites can be predicted by using a multiscale modelling approach. The starting point to its application is the microscale (the level of fibres, matrix and interfaces), that allows the computation of the homogenised behaviour of the yarn. The aim of this work was to predict the yarn-level behaviour of a thermoplastic-based woven composite in order to allow the formulation of a representative constitutive model that can be used to predict ply properties at the mesoscale. To accomplish this purpose, an insitu characterisation of the microconstituents was carried out. This served to generate inputs for three different representative volume element (RVE) models that allowed predicting the yarn longitudinal, transverse and shear responses. These mechanical characteristics allowed the determination of homogenised yarn constitutive behaviour which was found to be characterised by significant nonlinearity until failure, specially in transverse and shear directions.
This experimental work is aimed at the influence of seawater immersion in low impact energy behavior of a novel Colombian fique fiber reinforced bio-resin laminate. Such material was manufactured by vacuum infusion. The specimens were immersed in seawater during a bioactivity period of six months. Low energy impact tests were performed in order to obtain the penetration and perforation threshold according to energy profiles. The damage extent was characterized by means of Ultrasonics. Tensile stress tests were also performed and the breaking surfaces were analyzed by Scanning Electron Microscopy. The results revealed that the new biocomposite, after seawater immersion, has higher penetration and perforation thresholds than the biocomposite without immersion. Tensile test results show stiffness lost and increase of elongation at break. This behavior of the immersed biocomposite is due to a plasticization process of the material.
The improvement of engines is one of the ways to diminish the fuel consumption in civil aircrafts, and Open Rotors engines are one of the best promises in order to achieve a sensible efficiency increment. These engines have large composite blades that could, in the event of failure, impact against the fuselage, totally or partially. In this case, composite fragments could behave as impactors. In order to design fuselages for this event and adopt these new engines in the future, it is necessary to understand the impact behaviour of a composite fragment against a deformable structure. To this end, unidirectional and woven composites fragments were impacted at high velocity (up to 150 m/s) against aluminium panels at different impact velocities. The composite fragments were made using AS4/8552 (UD) and AGP-193PW (woven) prepregs manufactured by Hexcel Composites, both using AS4 fibres and 8552 epoxy matrix. High speed video cameras were used to record the impact process and to measure both the impact and the residual velocity and hence the energy absorbed.
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