Application of bridging-law concepts to short-fibre composites Part 3: Bridging law derivation from experimental crack profiles

This is the third paper in a series of four where notch sensitivity, fractu re energy and bridging laws are studied in short-fibre polymer composites. Here, bridging laws are derived from experimental crack-opening profiles in centre-hole notched tensile specimens. The materials studied are three typ es of commercial glass-mat composites with different reinforcement structur es and matrices. The materials have softening bridging laws and the calcula ted fracture energies from bridging laws are in good agreement with values determined directly by experiment. The calculated maximum local bridging st ress is found to be higher than the uniaxial tensile strength. An outline o f a failure criterion for notched specimens based on the crack-bridging app roach is presented. (C) 2000 Elsevier Science Ltd. All rights reserved.