Failure of thick-skinned stiffener runout sections loaded in uniaxial compression

The weakest parts of a composite laminate structure are often the joints. Hence the need to design reliable and efficient load-carrying joints has become increasingly important and the effects of stacking sequence and clamping force on joint strengths have to be clarified. In this study, the effects of stacking sequence and clamping force on delamination bearing strength and ultimate bearing strength of mechanically fastened joints (pinned and bolted) in carbon/epoxy composite laminates were examined using the acoustic emission (AE) technique. Two orthotropic and three quasi-isotropic laminate lay-up configurations and four clamping forces were examined. Based on the experiments, the effects of stacking sequence and clamping force on joint strengths were systematically investigated. Guidelines for effective stacking sequences and maximum clamping forces for mechanically fastened joints in composite laminates are suggested based on delamination bearing strength and ultimate bearing strength.