May it be for environmental or economic reasons, mass reduction has become one of the main goals of mechanical conceptions. Short fiber Thermoplastics composites is an interesting possibility since they present a good compromise between relatively easy process and mechanical properties. The aim of this work is to estimate and model the viscoelastic behavior at small strain of PC Lexan/Glass fiber composites.To meet this goal, a full field homogenization method based on solving the boundary problem through FFT is used. Virtual DMA experiments are used to build the master curve of the composite. They are later used to identify a macroscopic model for transverse isotropic short fiber composites. Finally, a meta-model is built to estimate the behavior of the composite at any given fiber volume ratio.
Modelling the damage of composite materials is not an easy task because different modes of ruins coexist: Fiber matrix decohesion,matrix cracks, delamination, and fiber cracks. In the case of laminated composites, the matrix cracks have the particularity to remain parallel to the fibers. As a consequence of the orientation of this crack network, only shear and transverse moduli in the plane of the ply are degraded in proportion to the increase of the crack density. The main point of this work is to characterize the relation linking transverse and shear damage with respect to the crack density. Following this objective, full field calculations are run using CraFT, a software developed at the LMA. The modeling is done in two steps: first the undamaged composite is homogenized, then, as a second step, the damaged behavior is determined by introducing cracks into the healthy composite. The behavior is calculated from an optimal size of RVE (Representative Volume Element) in order to determine numerically the relation between transverse and shear moduli variables.
The aim of this work consists to estimate and model the viscoelastic behavior at small strain of KetaSpire® KT-880 PEEK fiber composites reinforced with short glass fibers. The viscoelastic behaviour of the PEEK matrix is identified from a series of DMA tests at different temperatures. The principle of time-temperature superposition is used to build a master curve in order to identify the parameters of a generalized thirteen-branches Maxwell model. The composite's master curves are constructed by using virtual DMA experiments. These master curves are used to identify a generalized, transversely isotropic Maxwell spectral law. The modulus of each branch of the model are linked to the characteristic time of the branch by a normal distribution function (spectral law), which allows to drastically reduce the number of material parameters. Finally, a meta-model is
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