Test MethodEssential work of fracture analysis of glass microsphere-filled polypropylene and polypropylene/poly (ethylene terephthalate-co-isophthalate) blend-matrix composites

The essential work of fracture (EWF) concept was successfully applied to the fracture toughness characterization of ductile glass microsphere-filled polypropylene (PP)-matrix composites. Injection-moulded PP and PP/poly(ethylene terephthalate-co-isophthalate) (PET) blend-matrix composites filled with both untreated and silane-treated glass beads (50 wt%) were studied to ascertain the influence of the material composition on the EWF parameters. In addition, the effect of the specimen thickness was also studied on deeply double-edge notched (DDENT) specimens of nominal thickness 1, 2 and 3 mm. The results indicated that the EWF methodology could be applied to this kind of particulate-filled composites whenever high plasticity is developed in the crack tip front before the fracture propagation. PET addition markedly reduced both fracture toughness and plastic work of fracture in untreated and mercaptosilane-treated glass beads, attributed to glass embedding by PET. Concerning specimen dimensions, a noticeable drop in fracture toughness was found in thicker samples, whereas plastic work of fracture showed the opposite trend.