Fracture Toughness of Reinforced and Unreinforced Reaction Injection Moulded Polyurethane Elastomers

Abstract

A study has been made of the notch sensitivity and fracture behaviour of unreinforced and reinforced RIM polyurethane elastomers under tensile stresses. Sharp notches of various lengths were incorporated within the material both edge wise and from the surface and the applicability of fracture toughness tests was examined. The appearance of microcracks and the different skin–core morphology, together with the cellular nature of these materials, underline the complex fracture mechanism in these elastomers. Evidence is presented showing that there are residual stresses within the material after moulding and these tend to split up into tensile stresses in the core of the material and compressive stresses on the surface. Graphical representations, together with the micrographs of fracture surfaces, are presented.