Characterisation of damage development in single shear bolted composite joints

Experiments have been performed to study the force-deflection and damage development characteristics of bolted joints in carbon-epoxy composite materials, in the presence of variable bolt-hole clearance. Single lap, single bolt joint configurations, sized to induce bearing failure, were used. An initial set of tests involved loading joints up to ultimate failure. The primary failure mode was bearing failure. The secondary failure mode was bolt failure for the lower clearance joints, while the larger clearance joints exhibited large displacements without bolt failure. A further series of tests were then performed up to a load level corresponding to the first significant change of slope in the load-deflection curve of the larger clearance joints. These specimens were examined using optical microscopy and SEM to compare the damage in specimens with different levels of clearance. The joints with the largest clearance were found to exhibit the most damage.