## 3 Results
### Energy-Displacement  
The energy-displacement diagrams provide complementary insights to the force-time and energy-time graphs, as the slope of each curve corresponds to the instantaneous contact force, while the extent to which the lines return after the peak reflects the degree of permanent indentation in the plate. Taken together, these characteristics reveal how each laminate architecture balances stiffness and damage progression.  
For the untreated virgin specimens (Figure 7a), the first-impact traces (V1, V2) rose sharply and almost linearly to their peak, after which the curves became concave and dropped slightly, a behavior that is typical of brittle, fiber-dominated failure followed by partial elastic rebound. In contrast, thermal treatment (V2T) shifted the curve further rightward, indicating matrix softening and a reduction in bending stiffness rather than any healing effect. Virgin epoxy laminates demonstrated high energy absorption but limited toughness. Post-impact (V1U) and thermally conditioned (V2T) specimens revealed a decreased displacement and increased curvature, suggesting interfacial debonding and coalescence of microcracks.  
Figure 7: Energy-displacement graphs of (**a**) virgin, (**b**) nanofiber-layered, (**c**) PE-modified, and (**d**) hybrid specimens.  
The nanofiber-interleaved specimens exhibited notably consistent behavior across all four traces (Figure 7b). Their curves are closely clustered and exhibited nearly identical slopes, even for the thermally treated specimen (N2T), which followed the same trajectory after a slightly delayed onset. This suggests that the nanofiber interleaf helped preserve structural integrity and mitigates stiffness degradation, although it introduced some additional compliance after the nanofibers have fractured.  
In the PE-modified system (Figure 7c), the untreated specimens (P1 and P2) exhibited the steepest initial slope of the group. This steeper ascent reflected higher average force transmission and was attributed to localized shear-yielding around PE domains that rapidly engaged the E-glass layers. For the re-impacted specimen (P1U), the curvature was smoother, implying distributed, ductile damage rather than abrupt delamination. The treated specimen (P2T) absorbed energy much more gradually, indicating that molten PE had decreased the matrix modulus, delaying load transfer in the early stage but ultimately allowing larger transverse deflection and hence a comparable total energy budget. PE enhanced the ductile deformation capacity of the composite. The longer tail of P2T was indicative of energy dissipation through plastic flow and interfacial slippage. Heat likely contributed by softening the PE domains and improving interphase compatibility.  
For the hybrid specimens (Figure 7d), the untreated specimens (H1 and H2) showed the lowest displacement of all groups. Re-impact (H1U) revealed only minimal loss, confirming superior damage tolerance. After thermal activation, H2T surpassed its own untreated twin. This increase in final energy, coupled with early-stage softening, suggested that molten PE had infiltrated the nanofiber network, partially healed crack faces, and enabled further deflection before puncture without compromising ultimate load capacity. The combination of PE and nanofibers provided excellent toughness and post-impact durability. The high slope and wide displacement demonstrated damage tolerance with stable energy absorption. Hybrid samples outperformed the others in absorbed energy, progressive deformation, and damage mitigation, making them optimal for reusable or cyclic impact applications.