Combined bearing/pull-through failure envelope of composite joints: Experimental setup and numerical validation

The failure envelope of composite fastened joints under combined bearing and pull-through loading conditions is obtained by developing, testing and validating a new experimental procedure. The new device proposed here is compatible with standard testing machines and captures the critical interactions between the two loading mechanisms for pull-through to bearing ratios ranging from 0.2 up to 0.8, allowing the characterization of the behaviour of composite joints under realistic loading scenarios. High-fidelity finite element simulations are used to support the validation of the test methodology: the ability of the fixture to maintain a constant mixed load ratio during the whole test was numerically confirmed and a detailed analysis of the failure modes provided further insights into the main degradation mechanisms occurring during the experiments. A very good agreement between the predicted and experimental failure load was obtained for the entire failure envelope, indicating the effectiveness of both the proposed test method and modelling strategy.