The pull-out and failure of a fiber bundle in a carbon fiber reinforced carbon matrix composite

The interfacial failure is examined for a unidirectionally reinforced carbo n fiber/carbon matrix composite. A novel tensile test is conducted which re alizes the processes of interfacial debonding and subsequent pull-out of a fiber bundle from the surrounding composite medium. The critical stress at the onset of delamination cracking is related to the fracture energy (the c ritical energy release rate for mode II cracking). A force-balance equation of a fiber bundle, which is quasi-statically pulled-out of the composite s ocket, is formulated in terms of the inter- and intra-laminar sheer strengt hs of the composite. This equation is successfully used to estimate the del amination crack length along the debonded fiber bundle, as a function of th e stress applied to the bundle. (C) 2000 Elsevier Science Ltd. All rights r eserved.