## 3 Results
### Energy-Time  
The energy-time graphs confirm the trends observed in the force-time curves and offer additional insight into how each laminate architecture stores and dissipates the 11 J of impact energy. For the virgin specimens (Figure 6a), the absorbed energy curves for the first-impact specimens (V1, V2) exhibit an almost linear increase followed by a plateau, indicating that nearly all of the input energy is absorbed through damage formation and plastic deformation. Upon re-impact (V1U), the curve reaches its peak slightly earlier, implying that the tip rebounds from a now more compliant, damage-weakened target. Thermal conditioning (V2T) shifts the entire trace rightward without increasing the peak value, confirming that heating does not restore structural stiffness but merely delays energy uptake by alleviating residual stresses. Despite the observed degradation in force resistance, the virgin specimens continue to absorb comparable amounts of total energy, albeit over a longer time span. This suggests that energy absorption shifts from instantaneous to more time-dependent mechanisms, likely involving progressive matrix yielding and interfacial failures. In the nanofiber-interleaved specimens (Figure 6b), all four curves converge almost precisely at the same final energy value. The near-identical energy profiles, regardless of whether the specimens were damaged or thermally conditioned, underscore the role of PAN nanofibers as structurally robust, non-thermoplastic bridging elements. Their ability to suppress delamination and bridge developing cracks enables consistent and uniform energy dissipation across all conditions. Notably, the second impacts exhibit slightly increased energy absorption, which is likely attributed to the concurrent development of additional matrix and fiber cracks along with progressive damage to the nanofiber mat itself. The PE-modified specimens (Figure 6c) demonstrate a distinct energy absorption profile. The untreated specimens (P1, P2) absorb energy more rapidly than their virgin counterparts, a behavior attributed to viscoelastic deformation and frictional sliding at the PE/epoxy interfaces prior to rebound. This early dissipation indicates that pre-existing microcracks within the PE-modified matrix allow energy to be released earlier, while also permitting partial elastic recovery. After thermal treatment, the curve for the treated specimen (P2T) approaches the original plateau but begins to decline earlier, suggesting that molten PE reduces matrix viscosity, thereby enabling limited crack closure. However, this softening also facilitates time-dependent flow, which vents a portion of the stored energy during unloading. Overall, the incorporation of PE contributes to energy absorption through viscoelastic damping and plastic deformation. Heating further softens the PE domains, helping the thermally treated specimens retain favorable energy uptake behavior under repeated impact. The hybrid specimens (Figure 6d) demonstrated the most advantageous behavior. Both untreated specimens (H1, H2) rapidly absorbed energy, and their energy-time curves decayed smoothly as rebound energy was recovered, which provided evidence that the structure not only stored but also released energy in a controlled, elastic manner. The re-impact of the first specimen (H1U) reproduced this profile with a 4% reduction in peak force, confirming superior damage tolerance. Moreover, the treated specimen (H2T) maintained a  
Figure 6: Energy-time graphs of (**a**) virgin, (**b**) nanofiber-layered, (**c**) PE-modified, (**d**) and hybrid specimens. broader plateau prior to decay, implying that molten PE had infiltrated along the nanofiber mat, sealed crack faces, and re-established an efficient load path that both accumulated and released strain energy without catastrophic dissipation. Collectively, the energy analyses indicated that only the hybrid architecture combined high energy uptake with elastic recovery and post-thermal restoration.