Drop-Weight Impact of Composite Laminates: Modelling the Effect of a Round-Nosed Versus a Flat-Ended Impactor

The present study investigates the effect of the impactor geometry on the impact performance, at relatively high impact energies, of carbon fibre-reinforced polymer (CFRP) laminates with a cross-ply configuration of [0₂/90₂], which were manufactured using unidirectional (UD) carbon-fibre epoxy-matrix plies. Drop-weight impact tests were performed using both round-nosed and flat-ended rigid impactors. White light interferometry (WLI), ultrasonic C-scan and scanning electron microscopy (SEM) were employed to assess the relationship between the indentation profile, the delamination footprint and the fracture morphology along the fracture plane. This study focusses on the coupling between the extent of indentation, the loading responses and the associated damage caused in the CFRP. This damage involved both intralaminar damage, including matrix cracking and fibre-kinking and fracture, and interlaminar, i.e. delamination, damage. This paper studies in more detail the finding that the flat-ended impactor only caused significant damage to the CFRP panel when an impact energy of 25 J and above was attained, which was previously observed by Y. Ding. J. Liu, Z.E.C. Hall. R.A. Brooks, H. Liu, A.J. Kinloch and J.P. Dear, “Damage and energy absorption behaviour of composite laminates under impact loading using different impactor geometries”, Composite Structures 321 (2023) 117259. At an impact energy of 25 J, a compressive kink-band fracture plane occurred around the periphery of the flat-ended impactor near the front surface of the laminate. A previously published numerical model has been extended to account for these experimental observations. The modelling accurately predicts the damage features observed for the two types of impactor geometry with indentation playing a significant role on the threshold for damage and the distribution of damage.