The Relationship Between the Extent of Indentation and Impact Damage in Carbon-Fibre Reinforced-Plastic Composites after a Low-Velocity Impact

The present paper investigates the low-velocity impact behaviour of carbon-fibre reinforced-plastic (CFRP) composite panels and the damage incurred when they are subjected to a single impact. The relationship between the depth of permanent surface indentation that results and the associated area of interlaminar delamination damage is investigated for two different thicknesses of composite panels. In particular, the delamination damage area increases with impact energy for both thicknesses of composite panel that were studied. Likewise, the indentation depth also increases with increasing impact energy, again for both thicknesses of CFRP panels. It is shown that the indentation depth, at the centre of the indentation, may be used to provide an indication of the extent of delamination damage within the CFRP panel after impact. Indeed, from plotting the indentation depth versus the interlaminar delamination normalised by the thickness of the panel area there is shown to be a unique ‘master’ relationship, with a positive intercept indicating that the indentation damage seems to result before delamination damage initiates. Thus, for both thicknesses of CFRP panels, it is suggested that the indentation process is a precursor to interlaminar delamination damage.