The prediction of tensile failure in titanium-based thermoplastic fibre-metal laminates

The tensile properties of a titanium-based fibre-metal laminate have been investigated at quasi-static rates of strain. Initial attention focused on investigating the effect of varying the fibre orientation, theta, on the tensile modulus and strength of a range of [Ti, +/- theta](s), carbon-fibre/PEEK FMLs. Here, as expected, increasing the offset angle, theta, resulted in a decrease in the tensile properties of the FMLs. The failure mechanisms in the hybrid laminates were investigated through a series of cyclic tensile tests on a number of edge-polished samples. An examination of the specimen edges indicated that failure in laminates whose fibres were oriented at angles between 0 degrees and 15 degrees occurred as a result of fracture of individual carbon fibres. At offset angles greater than 15 degrees, initial failure took the form of localised debonding at the fibre-matrix interface. In addition to this debonding, laminates with values of 0 between 15 degrees and 45 degrees exhibited delamination between the composite plies. First ply failure (FPF) as well as the tensile strength of the FMLs was predicted using a number of simple failure criteria. Here, it was shown that the onset of damage under tensile loading conditions can be successfully predicted over a wide range of offset angles. (c) 2005 Elsevier Ltd. All rights reserved.