An experimental investigation into the use of inserts of enhance the static performance of thin composite bolted lap joints

摘要

The aim of this program was to investigate the use of interference fit and bonded inserts in thin 8 ply quasi-isotropic composite mechanically fastened single lap joints. The static behaviour of the joint was evaluated with various insertconfigurations. Bearing tests were also undertaken in order to evaluate the bearing behaviour of the laminate with the various insert configurations. Results from the bearing tests showed slight improvement in the bearing strength for press-fit straightinserts. A significant increase, up to 100%, in bearing strength was observed for the bonded top-hat insert compared to the no inserts case. The failure mode for the bolted joint specimens, without the inserts, appeared to be predominantly pull through of the fastener, even though the specimens were designed to fail in bearing. The pull-through type failure was caused by the secondary bending in the specimen which resulted in high severe pull-through stresses by the fastener head and collar. The top-hatinserts assisted in reducing the high pull-through stress exerted by the fastener head and collar and in some cases was so successful that the failure mode changed from pull-through to bearing with a corresponding 30% increase in the load carryingcapacity of the joint.