Bearing strength of carbon fibre/epoxy laminates: effects of bolt-hole clearance

The bearing strength of carbon fibre epoxy laminates manufactured from non-crimp fabric from heavy tow yarn has been investigated. The effects of laminate stacking sequence and geometry on the bearing strength have been determined experimentally together with the effect of initial bolt-hole clearance on the bearing strength at 4% hole deformation and at ultimate load. Significant reduction in bearing strength at 4% hole deformation was found for both pin-loaded and clamped laminates as a result of bolt-hole clearance. It was concluded that the effect of bolt-hole clearance is significant with regard to the design bearing strength of mechanically fastened joints. A three-dimensional non-linear finite element model was developed to investigate the effects of bolt-hole clearance on the stress field in the laminate adjacent to the hole. The magnitude and distribution of stress at the hole was found to be significantly dependent on the level of clearance.