The dynamic behavior of metal-matrix composites under low-velocity impact

This study has observed that the dynamic behavior of metal-matrix composites (MMCs) varies with impact velocity. MMCs with 15 vol% of fibers were fabricated by the squeeze-casting method. AC8A aluminum alloy was used as the matrix, and alumina and carbon fibers were used as reinforcements. Tensile and vibration tests were conducted to obtain the tensile failure stress and elastic modulus of the MMCs. A low-pass filter and instrumented impact test machine were adopted to study the dynamic behavior of the MMCs at various impact velocities. Stable impact signals were obtained by using the low pass filter. As the impact velocity increases, the impact energy absorbed by each material increases but its dynamic fracture toughness does not change much. To show the relationship between crack initiation energy and dynamic fracture toughness, a simple model is proposed which uses the strain energy and stress distribution at a notch. The crack initiation energy is proportional to the square of dynamic fracture toughness and inversely proportional to elastic modulus.