Development of novel cost effective hybrid ply carbon-fibre composites

A carbon-fibre/epoxy hybrid material has been developed which comprises ultra-high-performance fibres in the principal load-bearing direction and standard carbon fibres in the secondary orientations. The effect of stacking sequence on mechanical properties, including impact damage tolerance, has been studied and the results compared with non-hybrid data. By optimising the stacking sequence the hybrid material exhibited a mechanical performance similar to that of the ultra-high-performance material and a performance superior to the standard material. The energy absorbed during low velocity impact was analysed in terms of an initiation and propagation energy. The energy absorbed through delamination initiation was increased by placing 45 degrees fibres in the surface plies and by placing ultra-high-performance fibres in the 0 degrees plies. The energy absorbed during delamination growth was independent of the fibre type and determined solely by the matrix material. On the basis of current pre-preg prices the hybrid material corresponds to a significant cost saving of 12% through the use of lower cost standard fibres in the secondary stressed layers. (C) 1996 Published by Elsevier Science Limited