## 4 Discussion
These specimens retained approximately 96% of their initial peak strength after re-impact and exhibited an additional 17% increase following thermal treatment, resulting in more than a 40% improvement in load-bearing capacity compared to the untreated virgin specimens. This performance surpasses that of the single-modified systems. Although the absorbed energy of the hybrid specimens decreased by \(\sim\)10% relative to the untreated virgin specimens, this was accompanied by the lowest permanent indentation and superior resistance to initial damage. This behavior suggests a favorable balance between stiffness and toughness. For the thermally treated hybrid specimens, a notable increase of \(\sim\)17% in absorbed energy was recorded relative to its untreated counterpart, marking the first such enhancement within this group. The overall improvement in performance can be attributed to the synergistic functions of the two modifiers: PAN nanofibers act as crack-bridging and delamination-resistant reinforcements, while polyethylene serves as a thermally responsive healing phase capable of flowing into damaged regions and restoring interfacial continuity under moderate heating conditions at 150 \({}^{\circ}\)C for 30 min. SEM analysis supported these findings. In the hybrid samples, a continuous PE-rich film was observed infiltrating along the nanofiber network, correlating with the smooth, bell-shaped force-time profiles and minimal permanent indentation measured during testing. Compared to the virgin and single-modified laminates, the hybrid structure exhibited more cohesive energy dissipation, reduced force oscillations, and restored load-bearing pathways--indicative of effective healing and improved structural integrity. Energy-based evaluations further highlighted the advantages of the hybrid system. Unlike the virgin laminates, which predominantly absorbed energy through brittle matrix failure, or the PE-modified specimens, which relied on viscoelastic mechanisms, the hybrid laminates demonstrated both high energy absorption and elastic recovery. Although they absorbed slightly less total energy than some single-modified samples, this was accompanied by the lowest residual indentation, suggesting a more efficient balance between stiffness and toughness. Despite these favorable outcomes, some trade-offs were noted. The PAN mat, while beneficial for damage suppression, caused a reduction in stiffness after thermal exposure; possibly due to interfacial relaxation or thermal expansion mismatch. In contrast, the addition of PE improved post-impact healing but introduced time-dependent viscoelastic effects that may affect long-term dimensional stability. The hybrid configuration effectively balanced these opposing tendencies, but its performance remained sensitive to the proportion and distribution of each modifier. Small deviations in PE content or fiber mat uniformity could lead to variability in mechanical response. While the inclusion of PE offers substantial functional benefits, it also presents limitations that must be considered. The tensile strength of PE-modified laminates was reduced, likely due to the disruption of epoxy network continuity and the formation of weaker interfacial regions. Additionally, the use of thermoplastics increases processing complexity and material costs, potentially hindering large-scale application. Nevertheless, PE's ability to restore mechanical performance through moderate thermal activation and its contribution to ductile energy dissipation justify its use in scenarios where repairability and impact durability are prioritized over maximum tensile performance. When used in conjunction with PAN nanofibers, these drawbacks are mitigated by the mechanical robustness and damage-controlling effects of the interleaf, resulting in a net gain in performance. In light of these findings, the hybrid modification strategy presents a promising and scalable approach for the development of advanced GFRP laminates with improved impact performance and thermal restorability.