The Effect of Crystallinity on the Impact Properties of Advanced Thermoplastic Composites

A range of thermoplastic matrix carbon fibre composites with varying degrees of crystallinity has been subjected to falling weight impact tests. Tests performed at excess energies, sufficient to cause total penetration, indicate that the thermoplastic composites are superior to toughened epoxies in terms of energy absorbed. After low energy impacts, the thermoplastic composites absorb less energy then epoxies with this difference being attributed to a reduction in the amount of microcracking. PEEK based composites are shown to be superior to PPS based composites and amorphous systems superior to crystalline equivalents. The generation of a plastic dent on the surface of a thermoplastic composite at an early stage of the impact event is thought to modify the deformation behaviour of thermoplastics relative to thermosets.