Multiscale modeling of strain rate effects in FRP laminated composites

Abstract

Fiber reinforced polymer composites are increasingly used in impactresistant devices, automotives, and aircraft structures due to their high strengthtoweight ratios and their potential for impact energy absorption. Dynamic impact loading causes complex deformation and failure phenomena in composite laminates. Moreover, the high loading rates in impact scenarios give rise to a significant change in mechanical properties (e.g. elastic modulus, strength, fracture energy) and failure characteristics (e.g. failure mechanisms, energy dissipation) of polymer composites. In other words, both mechanical deformation and failure are strainrate dependent. The contributing mechanisms can be roughly classified as viscous material behavior, changes in failure mechanism, inertia effects and thermome chanical effects. These effects involve multiple length and time scales. In experiments it is difficult to isolate single mechanisms contributing to the overall ratedependency. Therefore, it is difficult to quantify the contribution of each mechanism at different scales. The aim of this thesis is to establish a multiscale numerical framework in which three of the contributing mechanisms, i.e. the viscous material behavior, changes in fracture mechanisms and inertia effects, can be investigated at different scales. The research in this thesis is divided into four parts, one related to the macroscale, where the composite material is treated as homogeneous, and three on exploring possibilities to include microscale information, taking into account the microstructure of fibers and matrix.