Size effects on the tensile and compressive failure of notched composite laminates

An experimental and analytical investigation of the effect of size on the strength of composite laminates with central holes loaded in tension and compression is presented. Specimens with different hole sizes and with constant width-to-diameter ratios were tested in tension and compression under quasi-static loading and the strength reduction for increasing sizes was quantified for two lay-ups and for the two loading conditions. The first-ply failure load of the outer ply was identified using a new method that post-processes the displacement field obtained using the digital image correlation technique. The accuracy of the available strength prediction methods (point and average stress methods, inherent flaw model, semi-analytical cohesive zone model and finite fracture mechanics) to simulate the effect of size on the strength of notched composites is discussed. It is shown that the finite fracture mechanics model is the most accurate method.