Layering Concept for Wave Shaping and Lateral Distribution of Stresses During Impact

摘要

The overall objective of this research program was to examine the use of layered targets for distributing dynamic loads in high velocity impacts. Numerical simulations were carried out to address the research objectives. To explore the layering concept, we first used numerical simulations to demonstrate the feasibility of load spreading and wave shaping by layered structures. After the proof of concept, we devised a measure based on normalized dissipative energy density (NDE) to quantitatively characterize load spreading. Using this measure, we were able to gain considerable insight into the mechanisms governing load spreading and the behavior of layered structures to impact. The target properties examined included layering configuration, deformation and fracture behavior of layer materials, and interface properties. Three different approaches were used to treat the interface, namely a thin epoxy later, a slide line, and an interface element governed by irreversible cohesive law. Finally, to correlate load spreading with penetration resistance, we also developed a new energy approach to study the time dependence of the penetration process. The two major contributions from this research program are the demonstration of a potentially useful concept for developing resilient structures to withstand rapid impulsive loading, and the development of a new method to characterize the response of composite targets to such loading.