Damage assessment studies in CFRP composite laminate with cut-out subjected to in-plane shear loading

Abstract

The present work focuses on the damage assessment of carbon fiber reinforced polymer (CFRP) panels subjected to in-plane shear loading undergoing large deformation. Experimental investigations are carried out to understand the buckling, post-buckling and collapse behavior of quasi-isotropic CFRP panels with and without cut-out under the shear loading. A special picture frame fixture is designed and fabricated in-house for applying shear load over the CFRP test panels with clamped plate boundary conditions. In this work, the presence of a circular cut-out and its counter effects on the structural performance, associated damage mechanisms are monitored by an integrated use of digital image correlation (DIC) and acoustic emission (AE) techniques. The whole-field displacement and strain data over the test panels are monitored in-situ using the DIC technique, and later they are used for predicting the buckling and post-buckling response. Further, the surface strain data obtained from DIC are used to study the damage initiation and propagation zones in the test panels. AE technique is employed to identify the initiation and propagation of various damage mechanisms including classification in the buckling and post-buckling regime. A detailed micrographic study is also carried out on the fractured panels to support the damage assessments done by the AE technique. Additionally, finite element modeling is done to study the post-buckling behavior of CFRP panels with and without cut-out under shear loading conditions. The finite element results are compared with the experimental observations, and the accuracy of the numerical model is validated. This study gives a better understanding of the collapse mechanism of CFRP panels under shear loading and assists in designing damage tolerant composite structures.