Fracture Behaviour and Deformation Mechanisms of Polyimide/Silica Hybrids

Films of particulate polyimide-silica hybrids were produced by a sol-gel process and were examined in terms of morphological structure and fracture properties at different temperatures, varying from 20 to 250 °C. The fracture toughness characteristics were studied by the Essential Work of Fracture method using double edge-notched specimens of different ligament lengths. The results showed that the fracture toughness, expressed through the essential (we) and non-essential work of fracture (wp) parameters increased when submicron silica particles were dispersed in the polyimide matrix. In particular, it was found that both we and wp increased with temperature to a larger extent than the parent polyimide. This enhancement in the fracture toughness was attributed to extensive cavitations and shear yielding originating at the particle interface and within the matrix.