Abstract
To study brittle fracture of ductile polymers, tensile tests were conducted on cylindrical bars of polycarbonate, poly (vinyl chloride) and polyethylene with a circular round notch. The notchless specimens of these polymers fractured in a ductile manner after necking, but when the plastic constraint due to local yielding at the notch root became above a critical value they showed brittle fracture. Morphological observations revealed that the fracture origins were a microvoid for polycarbonate and poly (vinyl chloride) and a number of microcracks for polyethylene. They were considered to be nucleated by a hydrostatic stress component caused by plastic constraint ahead of the fully developed plastic deformation zone at the notch section.
