TORQUE TRANSMISSION CAPABILITIES OF BONDED POLYGONAL LAP JOINTS FOR CARBON-FIBER EPOXY COMPOSITES

Although carbon fiber epoxy composite materials have excellent properties for structures, the joint in composite materials often reduces the efficiency of the composite structure because the joint is often the weakest area in the composite structure. In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed. From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints.