Investigating low velocity impact and compression after impact behaviors of carbon fiber/epoxy composites reinforced with helical multiwalled carbon nanotubes

Pre-damage and undetected micro-defects in fiber-reinforced polymer (FRP) composites are significant challenges compromising the integrity and mechanical performance of composite structures in aerospace applications. To address this challenge, this experimental study investigated the low velocity impact (LVI) and compression after impact (CAI) behaviors of carbon fiber/epoxy (CF/E) reinforced with 0.0 (control sample), 0.2, and 0.4 wt% helical multiwalled carbon nanotubes (HMWCNTs). The LVI test results showed that the control samples, with epoxy as the predominant phase, registered the lowest peak force compared to the 0.2 wt and 0.4 wt% HMWCNT/epoxy composite laminates. The CAI test results showed a decrease in strength with increased impact energy and an increase in the weight percent of HMWCNTs. Consequently, the 0.4 wt% HMWCNT ladened composites could withstand higher load without undergoing significant deformations, exhibiting the highest impact resistances due to the presence of CNTs, which function as load-bearing material. The HMWCNT interleaved CF/E composite laminate samples subjected to 25 J of impact energy achieved a higher maximum force of 9870.25 N compared to 8527.26 N for the damaged samples at the same level of impact energies. This fact indicates that the damaged samples could not withstand sufficiently high impact forces due to local instability arising from existing damages. The results strongly suggest a high potential for HMWCNTs CF/epoxy laminate composites in making structural and substructural components in aircraft and automobiles due to their proven superior properties.