EFFECT OF FIBER SURFACE-TREATMENT ON YIELDING AND FRACTURE-BEHAVIOR OF GLASS-FIBER POLYPROPYLENE COMPOSITE

Two parallel studies of the mechanical properties of composites based on modified polypropylene is presented. The fillers used were either uncoated-glassy fibres or glassy fibres coated with aluminium. The tensile properties and fracture behaviour are investigated as a function of filler content over a range of temperatures and strain rates. The measured elastic modulus, tensile strength, and fracture parameters, G(c) and K(c), showed dependencies on filler content. The observed enhancement is found to be remarkable in the case of composites containing uncoated surface treated glass fibres. The tensile yield stress of all the composites prepared showed strain rate and temperature dependence. Stress activation volume and activation energy of single-activated yielding processes are determined. The observed fracture morphology could explain the reinforcement behaviour of the measured mechanical properties.