Self-healing CFRP laminates with CNT-EMAA thermoplastic System: Experimental and quantitative characterization

Abstract

To address the interlaminar damage commonly initiated in carbon fiber reinforced polymer (CFRP) structures, this study developed a self-healing system using carbon nanotubes (CNT)-modified poly (ethylene-co-methacrylic acid) (EMAA). Three CFRP specimen groups (S35, S40 and S45) with varying EMAA content (35 wt% to 45 wt%) and healing agent grid width (4.5–5.5 mm) were fabricated. Sequential bending loading–healing cycle tests were carried out to evaluate the healing performance of CNT-modified EMAA healing systems and quantitatively characterize their healing efficiency. The results demonstrate that all healed specimens retain their original stress-strain behavior characteristics while simultaneously achieving both improved initial cracking strain and high healing efficiencies ${\phi }_i$ ranging from 96 % to 246 %. Across three healing cycles, the cracking stress increases by 13.4 %–80 %, with Group S35 showing the largest improvement, followed by S40 and S45. The initial healing cycle predominantly contributes to the pronounced healing efficiencies, while subsequent cycles maintain stable multiple healing effectivity. Both healing agent grid width and content significantly influence these healing characteristics. The self-healing CFRP specimens exhibits stage-wise real-time resistance behaviors that correlate with internal damage evolution. Specifically, sudden resistance surge consistently corresponds to structural crack initiation and propagation. A strong correlation exists between resistance-based healing efficiency ($H_i)$ and stress-based healing efficiency (${\phi }_i$). Continuous resistance monitoring enables intelligent CFRP structural health and healing efficiency evaluation.