Fastener effects on mechanical behaviors of double-lap composite joints

Experimental and numerical studies were carried out to reveal the effect mechanisms of different fasteners on mechanical behaviors of composite bolted joints. Double-lap composite joints joined by protruding head or countersink fasteners were focused on and their mechanical behaviors were characterized. Differences in the joint strength, stiffness and failure mode between protruding head joint and countersink joint were depicted experimentally. Further comprehensive understanding of the fastener effects was provided by FE analyses, which embraced net-fit, clearance-fit and clearance-fit with preload cases and considered the influences of contact models. For composite joints with protruding head or countersink fasteners, the changes of contact area, fastener bending, local deformation and stress distributions around fastener hole were detailedly analyzed based on the numerical results. According to the combined investigation of experimental and numerical analysis, some useful conclusions have been deduced, which are helpful for the design of composite bolted joints.