Effect of Carbon Nanotube Embedding on the Mechanical Properties of Delaminated Carbon Fiber Reinforced Polymer Composite Plates

Abstract

Carbon fiber reinforced polymer (CFRP) composites are widely employed in aerospace, automotive, and civil infrastructure applications owing to their exceptional specific stiffness and strength. Delamination is one of the critical parameter in composite materials. However, interlaminar delamination remains the predominant failure mode critically undermining structural integrity. The present study investigates the influence of multi-walled carbon nanotube (MWCNT) reinforcement, introduced via matrix-level dispersion, on the mechanical response of CFRP laminates with pre-existing circular delaminations of varying diameters (10, 20, and 30 mm) at the mid-plane. Quasi-isotropic [0/45/−90/−45]ₛ laminates (nominal thickness 4 mm) were fabricated by vacuum-assisted resin infusion. Three MWCNT weight fractions (0, 0.3, and 0.5 wt.%) were examined. Specimens were characterised by tensile, compressive, short-beam shear, mode-I double-cantilever beam fracture, and compression-after-impact tests. Digital image correlation was employed to map full-field strain distributions. Incorporation of 0.3 wt.% MWCNTs increased ILSS by 18.3%, mode-I Gᴵc by 34.4%, and compression-after-impact strength by 22.0% relative to neat CFRP with equivalent delamination. At 0.5 wt.%, agglomeration effects partially offset these gains. Fractographic SEM revealed carbon nanotube pull-out, crack bridging, and matrix micro-crack deflection as operative toughening mechanisms. These findings demonstrate that low-concentration MWCNT doping constitutes an effective strategy for mitigating delamination-induced degradation in CFRP structural panels.