Impact load spreading in layered materials and structures: concept and quantitative measure

We demonstrate a potentially new concept to enhance the resilience of structures to withstand rapid impulsive loading. The basic idea is to use a high wave speed layer to rapidly spread (μs time scales) the locally applied impact load. We also propose a quantitative measure based on normalized dissipative energy density (NDE) to characterize load spreading. Using this measure, we have studied numerically the effects of wave speed, layering geometry (thickness and configuration), and mechanical properties (impedance and strength) of the layer and substrate on load spreading. The numerical calculations make a good case for the load spreading concept. The NDE measure may also serve as a useful tool to examine the general response of layered composites to impact loading.