Crack closure and fibre bridging during delamination growth in carbon fibre/epoxy laminates under mode I fatigue loading

The effects of crack closure and fibre bridging on delamination growth in carbon fibre/epoxy laminates under mode I fatigue loading have been experimentally investigated and are reported in this paper. The effect of crack closure has been investigated using a compliance based technique. The effect of fibre bridging has been investigated by comparing results of two sets of tests; one containing active fibre bridging while in the other fibre bridging was removed by cutting fibres during the fatigue tests. The effects of crack closure and fibre bridging are analysed by comparing the test data with the crack resistance surface obtained from the two-parameter model for the selected material. The results show that crack closure only influences the minimum load in tests with low stress ratios. Fibre bridging decreases both the minimum and maximum loads, but it keeps the stress ratio constant.