Optimization of Progressive Failure Response for Elucidation of Failure Mechanisms, Mode Interactions, and Sensitivity to Geometry, Material and Model Parameters

摘要

This paper investigates the progressive failure response in composite bolted joints under pure bearing loads. The paper demonstrates the use of optimization to maximize the sensitivity of the failure response. The optimal design for maximum energy dissipation and peak load were obtained using the edge distance and width (E/D, VV/D ratio when normalized by the pin diameter D) of a single bolt bearing test specimen geometry and ply angles of the laminate as design variables. The peak load and energy dissipated in progressive failure up to peak load were used as objective functions for the identification of optimal designs. The optimal designs were subjected to random variations to geometry, material and model parameters. Comparison of the statistics for the energy dissipation and peak load corresponding to the optimum design with the baseline design indicate maximization of energy dissipated leads to design with high sensitivity to perturbations (low robustness). The investigation of the evolution of the damaged material volume for the extreme designs identified from parameter perturbations show that the optimization leads to coalescence of failure modes and introduction of competing load paths. The increased sensitivity of the failure response to parameters in the optimization makes it easier to elucidate the contribution of failure mechanisms, their interactions and the resulting competing load paths on the failure response of a composite bolted joint.