FAILURE BEHAVIOUR OF LAMINATED COMPOSITE PLATES UNDER ANTICLASTIC BENDING

In this study, failure behaviour of laminated composite plates subjected to anticlastic bending is investigated. Anticlastic bending is a special case of bi-axial out-of-plane loading that applies predominantly twisting moment. A unique test fixture is designed to achieve anticlastic loading condition. Carbon-fibre-reinforced epoxy is selected as the material of the specimens. Totally nine different layup configurations are chosen and at least four specimens are tested for each configuration. Acoustic emission monitoring (AEM) is utilized to detect the first-ply-failure load and the progressive failure behaviour of the laminates. In this method, sound signals resulting from initiation and progression of damage within the material are detected, and then the signal data are processed to identify the failure modes and determine their time of occurrence. An energy-based method is employed to detect the first-ply-failure. The time of the first signal that yields the peak energy is considered as the first-ply failure initiation time. An FE model is developed to simulate the anticlastic bending test. A code is developed using ANSYS parametric design language to obtain the first-ply failure predictions using maximum stress, maximum strain, Tsai-Wu, Tsai-Hill, Hashin, Hoffman, and quadric surfaces failure criteria. The experimental and numerical results are then compared. Relative strengths and weaknesses of the failure criteria in estimating failure of laminated composite plates under anticlastic bending are discussed.