Experimental testing of BMI laminates with stress concentrations and the evaluation of SIFT to predict failure

An experimental investigation was conducted to determine the failure mechanism of notched-composite laminates subjected to tension, compression and shear. The experimental data were used to assess the applicability of point-failure criteria, i.e., strain invariant, for failure prediction. The assessment was achieved by firstly using the finite element method to determine the stress and strain distribution around stress concentrators representative of those encountered in the manufacturing, assembly and operation of composite structures of modern aerospace vehicles, for instance the sharp notches that may arise from impact events. Strength was then predicted using preliminary strain invariant failure theory (SIFT) analyses. Coupons that represented these features were manufactured and tested. Finally the test results were compared to the SIFT predictions.