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 (w_e) and non-essential work of fracture (βw_p) parameters increased when submicron silica particles were dispersed in the polyimide matrix. In particular, it was found that both w_e and βw_p 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.