Experimental investigation of the double impact position effect on the mechanical behavior of low-velocity impact in CFRP laminates

Composite structures are frequently subjected to repeated, low-velocity impacts, and these impacts usually occur at different positions of the same component, which is very common in daily use but lack of in-depth research. In the present paper, two positions at the same distance from the center of a carbon fiber reinforced polymer (CFRP) test specimen were impacted once with the same energy, respectively, and the mechanical responses during the impact and the various damages resulting from the impact were recorded. Then, the changes of the mechanical response curves were analyzed according to the damage characteristics, which revealed the influence of the four impact distances between the two impact positions and the three impact energies. The experimental results demonstrated that the impact behaviors and damage modes of the laminates were affected by the impact distance and energy in different ways. The coincidence degree of the same mechanical response curve and the separation degree of the damage region both directly indicated the correlation between the two impacts. Moreover, the maximum displacement of the specimen during the first impact reflected the difficulty level of the specimen deformation which had an important influence on the damage shape and area on the specimen. The characteristics of the critical separation distance between the two impacts were dissimilar in the case of different impact energies. Finally, semi-empirical relationships between the impact parameters and other parameters were obtained.