Intrinsic Self-Healing of Polyamide 6/Carbon Fiber Thermoplastic Laminates

This study investigates the self-healing capabilities of continuous carbon fiber (CF)-reinforced thermoplastic laminates, prepared via film stacking using an optimized polyamide 6 (PA6)/cyclic olefinic copolymer (COC)/ethylene glycidyl methacrylate (E-GMA) self-healing matrix (66.5/28.5/5 wt%) coupled with bidirectional CF fabrics. The self-healing composite demonstrates comparable porosity (2.3–2.7 vol%) to neat PA6/CF laminate (3.6–4.4 vol%) and exhibits enhanced tensile properties, with 43 % higher ultimate tensile strength (534 MPa vs. 374 MPa), likely due to improved fiber–matrix interaction through E-GMA compatibilization. However, the flexural strength decreases by 17 % (498 MPa vs. 599 MPa) for the self-healing system compared to the neat PA6/CF laminate, attributed to both the lower fiber volume fraction and the reduced tensile strength and stiffness of the PA6/COC/E-GMA matrix relative to neat PA6. The most significant finding is the exceptional self-healing performance, evaluated through short-beam shear (SBS) testing, which creates matrix-dominated damage while preserving fiber integrity. After thermal mending, the self-healing composite achieves complete damage restoration and full recovery of the interlaminar shear strength (ILSS), while neat PA6 composite shows minimal healing capability (14 %). Microstructural analysis confirms that the compatibilized COC effectively flows and fills the matrix cracks and delaminated regions during thermal mending. This work demonstrates for the first time the successful integration of intrinsic self-healing capabilities into continuous CF thermoplastic laminates below the matrix softening temperature by integrating intrinsically and thermally mendable copolymers, thus providing a foundation for damage-tolerant structural applications where autonomous repair capabilities and extended service life are critical.