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INTERLAMINAR FRACTURE TOUGHNESS OF MULTI-LAYER WOVEN SILK FIBRE/POLYESTER COMPOSITES

The effect of the number of layers of woven silk fibre on the interlaminar fracture toughness of silk/polyester composites which is a measure of the resistance of the material to delamination crack propagation has been studied. The multi-layer woven silk fibre/polyester composites were produced by compression moulding technique with increasing layers of silk of between 8 and 14 layers in thermoset polyester. The composite panels have been tested for mode I interlaminar fracture using double cantilever beam specimens (DCB) testing method. It was found that the interlaminar fracture toughness, GIC of the composite increases as the number of silk fibre layers increases. Stable crack propagation is observed during the tests and the crack propagation areas showed all the fibres were bare with no matrix covering them as were seen at 100x and 500x magnification using SEM. Failure occurred at the fibrematrix interface with no fibre bridging observed between the two fracture surfaces. The smooth clean surface of the silk fibres is the result of poor interfacial debonding and the increases in interlaminar fracture toughness is also due to improve strength of the composites panel.