Interfacial failure in poly(p-phenylene benzobisoxazole) (PBO)/epoxy single fibre pull-out specimens

The pull-out behaviour of poly(p-phenylene benzobisoxazole) fibres from an epoxy resin has been shown to follow that predicted by the elastic stress t ransfer shear-lag model at low applied strains, but at higher matrix strain s a partial debonding model was more suitable. Debonding of the fibre/matri x interface led to interfacial failure where only friction resisted fibre e xtraction. Raman spectroscopy was able to quantify this level of friction a nd together with in situ optical microscopy proved an excellent method for the close monitoring of the frictional pull-out process. The effect of fibr e surface treatment was also studied. The interfacial shear stress values f rom the heat-treated and corona-treated fibres showed only small difference s. The failure processes were examined further using scanning electron micr oscopy and clean fibre pull-our was observed with the heat-treated fibre wh ereas fracture of the for fibre occurred with the corona-treated fibre. (C) 2001 Elsevier Science Ltd. All rights reserved.