Nonlinear progressive damage model for woven patch-repaired laminate composites

Abstract

Laminated fiber-reinforced composite materials are vulnerable to damages arising due to impact events like accidental tool drops, bird strikes, etc., which significantly reduce the structural integrity of these materials. Therefore, one of the popular adhesively bonded repair techniques, i.e. patch repair is employed in this work. The present work focuses on developing a three-dimensional energy-based gradual degradation model for patch-repaired laminates, including the effects of shear non-linearity under tensile load. The model utilizes modified Hashin failure criteria for plain woven laminate and maximum shear stress criteria for the adhesive. Using the nonlinear model, the failure strengths for different pristine, drilled and repaired specimens with double-sided patches of [0]2 and [45]2 are studied. Tensile experiments in accordance with ASTM-D3039/D3039M are performed using Digital Image Correlation (DIC) and Acoustic Emission (AE) to validate numerical results. The simulated results based on the proposed model and experimental observations are used to compare the damage mechanisms of pristine, drilled, and patch-repaired laminates. It is observed that matrix cracking is majorly responsible for damage initiation. Subsequently, fiber–matrix debonding and fiber breakage account for the ultimate failure of pristine, drilled and repaired specimens. The developed model is used for studying the effect of different patch sizes of repaired specimens under tensile load.