Modelling toughening of composites with interleaved chopped fibres

This paper presents a micromechanical model for the toughening of continuous carbon fibre composites with interleaved layers of chopped fibres. Toughening results from a bridging process, involving chopped fibres that are almost parallel to the crack plane. This process can be divided into two stages - in plane cracking or spalling (matrix fracture following by separation of fibre away from the matrix) and fibre pullout. In the early stages of fibre bridging, the matrix surrounding the chopped fibres offers little resistance to fibre bending, so that in plane cracking occurs. In the later stages of fibre bridging. with a reduction in the embedded fibre length and an increase in the tensile stress on the fibres, fibre pullout occurs. The proposed model deals with both in plane cracking and fibre pullout. (C) 2002 IoM Communications Ltd.