12 - Design and failure analysis of composite bolted joints for aerospace composites

Abstract

This chapter presents an experimental and numerical study on the design and failure analysis of composite bolted joints. The primary geometrical variable under investigation is bolt-hole clearance, and is chosen as it induces significant three-dimensional stresses into the joint, and significantly alters the bolt-load distribution in multibolt joints, and so provides a rigorous test case. It is shown that the increases in bolt-hole clearance lead to higher stresses at the bolt-hole, and this, in turn, causes both matrix and fiber damage to occur earlier in the loading history. Hence, for limit load design, or design that requires no fiber damage, clearance should be considered an important design parameter. However, it was found that bolt-hole clearance did not have a significant effect on the ultimate failure load of joints, which was due to the extensive bearing damage that takes place in the joints, which masks any initial clearance effect and redistributes loads to other fasteners in the multibolt joints.