In this work, the effect of heat treatment on the fracture toughness of glass fibre reinforced polypropylene was studied. Polypropylene blended with short glass fibres was injection-moulded. The moulded parts were heat treated at 150°C for 30 min. The crack growth resistance curve (R-curve) was measured to evaluate the effect of heat treatment on the fracture toughness, and to determine the stress intensity factor at the point of instability, KR(ins). The fracture surface was examined using scanning electron microscope to analyze the fracture mechanism. The results show that the stress intensity factor at the unstable fracture point KR(ins) increases with the initial crack length.
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