Thermal failure mechanism and failure threshold of SiC particle reinforced metal matrix composites induced by laser beam

Abstract

The failure of particulate-reinforced metal matrix composites (MMCs) induced by laser beam thermal shock is experimentally and theoretically studied. It is found that the initial crack occurs in the notched-tip region, wherein the initial crack is induced by void nucleation, growth and subsequent coalescence in the matrix materials or interface separation. However, crack propagation occurs by fracture of the SiC particle and it is much different from the crack initiation mechanism. The damage threshold and complete failure threshold can be described by a plane of applied mechanical load σ max, and laser beam energy density E J. A theoretical model is proposed to explain the damage/failure mechanism and to calculate the damage threshold and complete failure threshold. This model is based on the idea of stress transfer between a reinforced-particle and the matrix, as well as the calculation of the applied mechanical stress intensity factor and local thermal stress intensity factor. In order to check the validity of the theoretical model, the finite element simulations are carried out for the temperature field induced by laser heating, the stress fields induced by the combined laser heating and applied mechanical tensile load. Both the theoretical model and the finite element simulation can explain the experimental phenomenon. The theoretical model can predict the damage threshold and failure threshold. The failure of MMCs induced by laser thermal shock and applied mechanical load is non-linear.