Failure analysis of compression-after-impact of CFF/PEEK thermoplastic composites subjected to double-position impact based on DIC and Micro-CT techniques

Compared to single-position impacts (including both single and multiple impacts), multi-position impacts on fiber-reinforced polymer (FRP) composites are more common in engineering applications, yet this scenario is often overlooked in existing research. Moreover, evaluating the load-bearing performance of FRP composites after impact is of great significance. Therefore, this study focuses on the compressive behavior of CFF/PEEK thermoplastic composites subjected to double-position impacts. Utilizing digital image correlation (DIC) and micro-CT scanning techniques, the effects of impact energy and impact spacing on the mechanical response, damage evolution, and failure morphology of compression-after-impact (CAI) are extensively analyzed. The results indicate that the strength of CAI is mainly dominated by impact energy, which significantly decreases with increasing impact energy, but is weakly affected by the impact spacing. And the local buckling load and stiffness of CAI are sensitive to impact energy and impact spacing. The failure mode of CAI is primarily influenced by the level of impact energy; however, the deformation evolution process of CAI depends on both impact energy and impact spacing. The failure morphology of CAI is primarily associated with the impact energy level. For low impact energy level events, the transverse failure morphology is continuous penetrating delamination, and the longitudinal failure morphology is dominated by shear fracture; whereas for high-impact energy level events, the transverse failure morphology is multi-segmented delamination, and the longitudinal failure morphology involves a combination of shear and delamination failure modes. This study provides a technical idea for investigating the CAI behavior of FRP composites subjected to multi-position impacts.