Damage Tolerance in CFRP Structures - Numerical and Experimental Analysis of Low Energy Near Edge Impacts

This work aims towards contributing to the better understanding of the behaviour of the primary composite aeronautical structure after near-edge impacts which are inevitable during the service life of an aircraft. Following the experimental work on near edge impacted CFRP specimens, presented by the authors at ICAF2015, a numerical model relative to near edge impacts was developed and calibrated using the obtained experimental data. The size and the shape of near-edge impacted zone (dent) in the thin specimen was considered to be in direct correlation with the delaminated area of the specimen and this assumption is made based on data presented in open literature. The FEM model relative to the tested specimens has been developed and tuned for near edge impacts of CFRP structure, based on material data for CFRP pre-preg and lamina interface available in the literature, and on experimental measurement of size and shape of the impacted zone in the tested specimens. By correlating the numerical model for the thin specimens with the size and shape of the impacted area, it is possible, for different configurations and energy levels, to predict the extension of a delamination in a CFRP structure and to estimate its residual static strength using a very simple but robust technique.