Fatigue characteristics of the bolted joints for unidirectional composite laminates

When composites are employed as structural materials, joining of composites to other materials is necessary because manufacturing structures with composites only is not generally feasible. Although the maximum static strength of the composite bolted joint is frequently realized by quasi-isotropic patterns, these patterns are seldom used in structural members under general load, such as bending, compressive, and tensile load. To increase the efficiency of whole structures with the composite bolted joints, the laminate with stacking sequence of [±θ/08]S was proposed in this work. The fatigue characteristics of the [±θ/08]S laminate bolted joint were investigated with respect to the angle θ and the bolt clamping pressure and compared with the result of the [02/±453/902]S laminate, which was proposed as one of the optimum stacking sequence under the static load. From the experiments on the bolted joints, it has been found that the laminates whose major plies are stacked in the axial direction can be used for the bolted joint structures under fatigue load when an appropriate clamping pressure is applied to the bolted joint.