Modelling of geometrical microstructures and mechanical behaviour of constituents

In addition to the macroscopic component geometry, a morphological microstructure model and material models for all individual phases of the material are required as input data to apply multi-scale methods. However, the advantage is that complicated mechanical coupon tests on the composite material can be avoided. This chapter explains the computation of morphological and material parameters on the example of short glass fibre reinforced polymers. The fibre orientation is the most important geometrical micro-structural parameter which has to be computed from µCT scans, whereas other micro-structural parameters (e.g. fibre length distribution and diameter) are a priori known. State-of-the-art methods for estimating local fibre orientations based on 3D image data are used to determine this essential microstructure feature depending on the sample position w.r.t. the flow front. After that the generation of virtual microstructures with the same morphological parameters as the µCT scans is considered. In the second part of this chapter, the identification of the material parameters is described for the polymer polybutylene terephthalate (PBT). All necessary parameters of a rate-independent elastoplastic model with damage are computed from cyclic tensile tests with increasing load amplitudes. Finally, the validation of the morphological and material models are illustrated by using an FFT-accelerated pseudo-spectral method as micro-scale solver.