Critical stress criteria for interfacial cavitation in MMCs

Density measurements and microstructural examinations have been used to follow the formation, growth and coalescence of cavities during tensile loading of metal matrix composites (MMCs). Finite element modelling has been used to predict the stress states around reinforcements of various shapes. The positions of peak hydrostatic and normal stress components at the interface have been compared with the microstructural sites where voids were found to form experimentally in aluminium reinforced with alumina particles or fibres. It is concluded that cavities form when a critical hydrostatic stress is reached.