Impact and Post-Impact Properties of Carbon Fiber Fabric Laminates Reinforced With Carbon Nanofibres

Abstract

The use of carbon fiber reinforced polymers (CFRPs) is limited by their susceptibility to low-velocity impact (LVI) damage. This study investigates the effect of incorporating 0.75 wt.% carbon nanofibres (CNFs) into the epoxy matrix of carbon fiber fabric laminates on their impact performance and post-impact mechanical properties. LVI tests were performed with energies ranging from 1 to 9 J, followed by an evaluation of residual bending strength, stress relaxation, and creep properties. At an impact energy of 9 J, the CNFs-enhanced laminates exhibited a 9.2% higher maximum impact load and a 9.0% lower maximum displacement compared to the control laminates with neat matrix. Elastic energy restored after impact was also considerably higher, with an improvement of 21.06% at 9 J. Consequently, the addition of CNFs increased the laminate's penetration threshold by 9.4%, from 12.94 to 14.15 J. Following impact, the residual bending strength and stiffness of the nano-reinforced laminates were consistently higher than the control group; at an impact energy of 9 J, both properties were 5.3% greater. Impact damage was found to accelerate viscoelastic effects, with a 9 J impact increasing the creep displacement by 2.4 times compared to unimpacted samples. While CNFs did not substantially alter the inherent viscoelastic behavior of the material, they mitigated damage by creating bridging mechanisms that delay crack propagation. This resulted in a slight reduction in stress relaxation for impacted samples. The findings confirm that incorporating CNFs is an effective strategy for enhancing the damage tolerance and structural integrity of composite laminates.