Application of bridging-law concepts to short-fibre compositesPart 2: Notch sensitivity

This is the second paper in a series of four where notch sensitivities, fracture energies and bridging laws are studied in short-fibre polymer composites. Estimates based on an order-of-magnitude criterion indicate that previous notch sensitivity studies on short-fibre composites are limited to small notch sizes in the ductile region. For this reason, centre-hole notch sensitivity is studied experimentally as a function of relatively large notch diameters in the range 15-60 mm. The materials have different matrices, glass-fibre content and fibre lengths. The onset of notch sensitivity is observed for all materials (glass-mat thermoplastics, sheet-moulding compounds and chopped-strand-mat laminates), although large notch sizes are required. The reasons for this are discussed as well as the influence of different material parameters. On the basis of the material bridging law and laminate Young's modulus, it was possible to rank different short-fibre composites with respect to notch sensitivity.