Abstract
The fracture and fatigue behaviours of reaction injection moulded (RIM) polyamide block copolymers (NBC) without and with milled glass fibres (GF) were studied using the fracture mechanics concept at ambient temperature. The static fracture toughness determined according to the ASTM E 399 standard ( K Q) aand its maximum value computed from the maximum load ( K Q,max) decreased with increasing polyol (soft segment) content and proved to be unaffected by GF filling. Increasing the deformation rate, including high-speed impact bending tests, resulted in higher fracture toughness ( K d) values, closely matched to K Q,max. The resistance to fatigue crack propagation (FCP) deteriorated with increasing soft segment and GF filler content. This was explained by differences in the molecular build-up and porosity of the NBC and related composites caused by moulding. The lower and upper bounds of the stable FCP range were found at K Q and K Q,max, respectively.
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