Static and fatigue behaviours of a bolted GFRP/steel double lap joint

To provide a safe and reliable connection using bolts for glass fibre-reinforced polymer (GFRP)/metal hybrid structures in civil engineering, the static and fatigue behaviours of a bolted GFRP/steel double-lap joint (DLJ) with a clamping force of 10 N m were investigated experimentally under monotonic tensile loading and repetitive tensile loading with a load ratio of R = 0.1, respectively. The dominant failure modes, fatigue life and stiffness degradation law were obtained for the bolted DLJ. The fatigue damage evolution of the bolted DLJ was also clarified. The F-N curve and a non-linear stiffness degradation model were obtained from the experimental results for the bolted GFRP/steel DLJ. Finally, a comparison between the fatigue behaviour of the bolted GFRP/steel DLJ and that of a GFRP/GFRP DLJ was performed to identify the differences. The results indicated that the stiffness degradation law of the bolted GFRP/steel DLJ could be accurately characterized by the non-linear stiffness degradation model. The GFRP/steel DLJ exhibited a longer fatigue life than the GFRP/GFRP DLJ because the compressive stresses in the inner surface of the bolt-hole of the outer GFRP laminates were much smaller in the bolted GFRP/GFRP joint than the bolted GFRP/GFPR DLJ under the same applied maximum load. The stiffness degradation rate of the GFRP/steel DLJ under fatigue loading was almost the same as that of the GFRP/GFRP DLJ during their service lives.