Re-evaluation of mode i bridging traction modelling for z-pinned laminates based on experimental analysis

This paper re-evaluates the crack bridging traction analysis used to calculate the mode I interlaminar fracture toughness of z-pinned fibre-polymer laminates. Existing bridging traction models use several simplifying assumptions about the physical condition and failure mode of z-pins embedded within laminates which compromises their numerical accuracy. Microstructural analysis and z-pin bridging traction tests revealed that misalignment of z-pins, interfacial cracking around z-pins, porosity within z-pins, and failure mode of z-pins each affect the traction properties, albeit in different ways. The mode I bridging models have been modified to account for these factors. The accuracy of traction loads calculated using the modified model compare favourably against experimental loads measured for fibrous z-pins in carbon-epoxy laminate.