Impact Damage Visualization of Heterogeneous Two-layer Materials Subjected to Low-speed Impact

摘要

A systematic experimental investigation of the generation and subsequent evolution of impact damage in heterogeneous two-layer materials is presented. Model layered specimens involving a compliant polymer layer bonded with a metal layer were designed and subjected to impact loading to simulate failure mechanisms in real time. High-speed photography and dynamic photoelasticity were utilized to visualize the nature and sequence of dynamic failure modes. A series of complex failure modes was documented. Interlayer crack growth (inter-facial delamination) is the dominant dynamic failure mode. These cracks appear to be shear dominated and might proceed with intersonic speeds. Intralayer cracking always occurs in a local Mode I crack inside the weak layer. Both impact speed and interfacial bonding strength have significant influence on the impact failure. High-impact loading leads to high interlayer crack speeds. Specimens featuring ductile and weak bonds subjected to high-impact speeds are shown to feature intersonic cracks with clearly visible shear shock wave (Mach lines) emitted from the crack tips.