The effect of heterogeneity on plane wave propagation through layered composites

When laminated composites are subjected to impact loading, the material response is critically determined by the interactions of multiple waves generated at the laminate interfaces. Due to the high complexity arising from the architectural details of composites, layered heterogeneous materials have been studied as the model system to understand the impact behavior of engineering composites. Previously, the present authors have developed an analytical solution to the problem of plate impact of layered systems; plate impact test is a standard boundary value problem used to study high velocity impact behavior both in the elastic and shock wave regimes. In this paper, we examine the various heterogeneity factors that affect the impact response of the laminated composite systems. We have identified three different heterogeneity factors (impedance mismatch, interface density and thickness ratio) and examine their effects on wave scattering. These effects are then used to explain some outstanding experimental observations in terms of shock wave structure (arrival time, sloping rise, peak stress and oscillatory pulse duration). It is shown that though the results pertain to layered systems, the observations can be qualitatively extended to real composites.