Scaling effects in the low velocity impact response of CFRP laminates

Scaling effects in the impact response of a carbon fibre-reinforced polymer (CFRP) composite have been investigated through experimental tests conducted on an instrumented drop-weight tower at five different impact energies, including an impact energy just greater than that is required to perforate the CFRP laminates. An examination of the tested composite panels highlighted that the predominant failure mechanism was fibre fracture extending away from the centre of the panel in warp and weft directions. In addition, it has been shown by analysing the load-displacement traces that the elastic response obeys a simple scaling law, whereas impact damage does not scale in accordance with simple scaling laws, with damage becoming more severe in the large panels. Such effects, i.e. the presence of increased severity of damage in the larger scale sizes, has been explained from the perspective of the normalised projectile displacement in the fibre fracture phase, the normalised crack length and the absorbed energy in the impact event. It is argued that the energy absorbed in fibre fracture phase does not scale in the expected manner, leading to greater levels of fibre damage in the larger plates. Further, the "unexpected" lower level of fibre fracture in the scaled panels subjected to the impact energy higher than the perforation energy threshold has been explained a result of the development of some degree of matrix crushing failure and delamination during the impact event.