The response of metal-matrix composites subjected to quasi-static and shock-wave deformation

The mechanical response and substructure evolution of three composites (Al-Li alloy reinforced with 55 vol.% A1₂O₃ long fibers, P/M aluminium alloy X7091 reinforced with 30 vol.% B₄C particulates, and Ti-6Al-4V alloy reinforced with 42 vol.% B₄C-coated B long fibers) subjected to shock loading (strain rate>10⁶ s^-1) and quasistatic compression or tension (strain rate ≈ 10^-3 s^-1) were examined. The as-received materials were first characterized in terms of both the phase identification of the interfacial reaction products and the measurement of basic lowrate mechanical properties. The materials were shock-loaded using a gas launcher to a peak shock pressure of nominally 5 GPa. Post-shock reload tests at quasi-static strain rates were then applied to the shock prestrained composites in order to trace the mechanical response due to shock loading. The dynamic deformation behavior was compared to that during quasi-static deformation. The results showed that the passage of a shock wave can produce appreciable damage to composites, especially for fiber-reinforced materials. This damage is attributed to the fact that tensile waves are induced whenever the shock wave encounters a ceramic/metal interface in a composite, owing to the shock impedance mismatch. Finally, the substructure evolution and deformation/fracture behavior of the composites after dynamic and quasi-static loading are compared and discussed in light of singlephase material response to shock-loading.