Notch sensitivity and bridging laws in glass mat composites

Abstract: The fracture behaviour of polymeric random glass mat reinforced composites was investigated. Such materials exhibit very large damage zones with fibre bridging. The damage zone sizes are often comparable with the specimen dimensions, which precludes the use of linear elastic frac-ture mechanics (LEFM). Instead, methods based on crack bridging concepts were applied. Ma- terials with different matrix and different reinforcement structures were studied. The investiga-tions covered measurements of notch sensitivity, microscopic studies, measurements of fracture energy and bridging laws by a DCB test, speckle measurements, and finite element modeling. The materials were found to exhibit low notch sensitivities. At low temperature the notch sen-sitivity decreased further. Differences in notch sensitivity were explained based on mi-cromechanical observations. The investigated materials had softening bridging laws. Based on the measured bridging laws notch sensitivities were predicted and a good correlation with the experimental observations was obtained.