Experimental Investigation of Multi-Walled Carbon Nanotube Effects on Vibration and Damping Characteristics of Delaminated Carbon Fiber Composite Laminates

Abstract

Carbon fiber reinforced polymer (CFRP) composites have gained widespread adoption in aerospace, automotive, marine, and civil engineering applications owing to their exceptional specific strength and stiffness. However, the structural integrity and dynamic performance of CFRP laminates are significantly compromised by delamination defects, which are inevitable during manufacturing and service life. This study presents a comprehensive experimental investigation into the synergistic effects of functionalized multi-walled carbon nanotube (f-MWCNT) reinforcement on the vibration and damping characteristics of delaminated CFRP laminates. The research systematically examines the influence of CNT weight fractions (0%, 0.25%, 0.5%, and 1.0%), delamination sizes (10–40 mm), delamination locations, stacking sequences, and boundary conditions on modal frequencies and damping ratios. CFRP laminates were fabricated using VARTM techniques with f-MWCNTs uniformly dispersed through ultrasonication. Controlled delaminations were introduced using Teflon inserts. Modal testing employed impact hammer excitation and accelerometer measurements. Results demonstrate that f-MWCNT reinforcement enhances fundamental natural frequencies by 12–18% at 1.0 wt.% CNT loading and improves damping ratios by 25–35%. Delamination causes frequency reductions of 8–25%, but CNT reinforcement recovers 55–65% of these losses. The findings reveal that f-MWCNTs effectively suppress vibration amplitudes and enhance resistance to delamination-induced degradation, offering pathways for next-generation composite structures with improved durability and dynamic stability.