A physically-based model for the notched strength of woven quasi-isotropic CFRP laminates

Abstract

Damage growth and fracture at circular holes in quasi-isotropic CFRP laminates loaded in tension has been studied. The laminates were based on two weave types and of three different thicknesses. A notch edge damage analysis was performed on a layer by layer basis after decomposition of the matrix. It was shown that near the notch edge, damage in the form of fibre tow failure occurred in the tows orientated at 0°, whilst the tows oriented at 45° within the damage area remained intact to loads just below the maximum load. The well known semi-empirical point and average stress criteria resulted in accurate notched strength predictions with the average stress criterion being better than the point stress criterion. A recently developed critical damage growth model, requiring as input parameters the unnotched strength and fracture toughness of the laminate which were measured from independent experiments, yielded accurate notched strength predictions, while being easy to implement. The resilience of the critical damage growth model was investigated and it was found that a variation in both the input parameters of the model by 10% result, even in the worst case, in a 10% variation in the notched strength predicted by the model.