Tensile behavior of the bolt-jointed GFRP after low-velocity impact

Bolt joint is one of the most commonly used methods for fiber-reinforced polymers (FRP) structures whose mechanical properties are quite sensitive to both the stacking sequence and the low-velocity impact loading. For this reason, herein, we conducted an experimental method with the self-designed clamp to evaluate the influence of low-velocity impact (LVI) at the compressed area nearby the bolt hole on the residual tensile properties of bolt joint GFRP laminates with various stacking sequences. After comparing the displacement-force curves and failure modes of different bolt joints in tensile tests after LVI loading, the effect of LVI and the failure mechanism subjected to post-impact loading are discussed in depth. Tensile properties show that the damage caused by impact has a significant effect on the performance of the composite. Under the condition of incident energy of 9 J and distance of 6 mm from the center of the bolt hole to the impact point, the ultimate tensile value of Ply-A, Ply-B, and Ply-C samples are reduced by 32.3%, 34.6%, and 50%, respectively. This influence can also be confirmed by observing the failure morphology, describing the interlaminar behavior of the specimens varying stacking sequence, where a more serious interlaminar damage was identified at Ply-C specimens. In addition, we also utilized the VIC-2D device to record and analyze the strain of different ply stacking sequence specimens in the failure process. The result shows that all types of cases have the same initial failure mode of bearing, but various final failure modes.