Buckling, propagation and stability of delaminated anisotropic layers

Previously, the authors have developed a modelling methodology that establishes a threshold strain below which damage propagation will not occur in laminates subject to Compression After Impact (CAI). In order to validate this methodology, a number of quasi-istropic coupons each containing a circular artificial delamination have been tested in axial compression. These coupons had 0o, ±45o and 90o dominated thin sublaminates placed above the delamination in order to prove the applicability of the model to sublaminates with high anisotropy. Results indicate the model can predict both the strain at which delaminations in the coupons with 0o and ±45o dominated sublaminates propagate from their original sites and the stability with which propagation occurred. Analysis of the coupon with a 90o dominated sublaminate was inconclusive due to an unexpected experimental propagation mode. For all coupons delamination propagation was in the direction of the dominant fibre direction in the sublaminate. The established methodology is shown to be suitable for assessing the damage tolerance of composite laminates.