Experimental studies on the interfacial shear-transfer mechanism in discontinuous glass-fibre composites

Interfacial stress/strain distributions in discontinuous glass-fibre/epoxy composites have been determined experimentally for the first time by the si multaneous use of tensile deformation measurements and Raman spectroscopy. Model single-fibre composites were used and the glass fibres were coated wi th a diacetylene-urethane copolymer which was thermally cross-polymerised. During composite deformation, the stress-induced band shifts of C=C in the polydiacetylene phases of the coating were used to map the strain distribut ion along a fibre as a function of overall matrix strain up to fibre fractu re. Measured strain distributions in fibres were analysed by using classica l shear-lag theory to determine interfacial shear-stress distributions. Fib re fragmentation was monitored in detail up to saturation, and the limiting value of interfacial shear stress is shown to be determined by the shear y ield stress of the matrix. (C) 2000 Elsevier Science Ltd. All rights reserv ed.