## 2 Materials and Methods
For all specimen groups, eight layers of dry E-glass fiber fabric with a [0\({}^{\circ}\)/90\({}^{\circ}\)] bidirectional orientation were used as the reinforcement [50]. The fabrics were supplied by a commercial distributor (Kompozit.net, Istanbul, Turkiye) and featured a plain weave architecture with a surface density of 200 g/m\({}^{2}\) and a thickness of 0.2 mm. Additional properties of the E-glass fibers include a tensile strength of 2 GPa, a Young's modulus of 80 GPa, a shear modulus of 30 GPa, a density of 2520 kg/m\({}^{3}\), a glass transition temperature of 350 \({}^{\circ}\)C, a thermal conductivity of 1.2 W/m\(\cdot\)K, and a coefficient of thermal expansion of 4.8 \(\times\) 10\({}^{-6}\) K\({}^{-1}\). In this study, four distinct groups of composite specimens were prepared: (i) virgin specimens, (ii) PE-modified specimens, (iii) nanofiber-reinforced specimens, and (iv) hybrid specimens incorporating both PE and PAN nanofiber mats. The virgin specimens consisted solely of neat epoxy reinforced with eight layers of E-glass fabric. The nanofiber-reinforced specimens were composed of neat epoxy and an eight-layer E-glass laminate, in which a PAN-based electrospun nanofiber mat was interleaved precisely at the mid-plane between the 4 th and 5 th layers. The PE-modified specimens comprised eight layers of E-glass fabric infused with an epoxy matrix containing 15 wt% dispersed PE powder. Finally, the hybrid specimens included eight layers of E-glass reinforcement infused with an epoxy system  
Figure 1: (**a**) Nanofiber mat, (**b**) SEM image of the nanofibers, and (**c**) frequency of the diameter size. containing 15 wt% PE powder, along with a PAN nanofiber mat interleaved at the same mid-plane position. All composite laminates were fabricated using the vacuum bagging technique, in which the glass fiber fabrics were manually impregnated with the epoxy mixture and then stacked layer by layer into a mold (Figure 2b). To ensure a uniform distribution of PE powder within the epoxy system, the PE-modified epoxy was prepared by mechanically stirring the powder with the resin for one hour, followed by the addition of the curing agent, which was mixed for an additional 15 min. The resulting mixture was then applied to the fabric layers. The assembled layup was sealed in a vacuum bag, and vacuum was applied using a pump to remove entrapped air and to promote uniform resin flow and compaction. Special attention was given to maintaining vacuum integrity and preventing air leakage throughout the curing process. The fabrication was carried out at room temperature and approximately 50% relative humidity. After manufacturing, the specimens were removed from the vacuum bag and subsequently stored under ambient conditions for an additional 24 h to ensure complete curing. For each configuration, six nominally identical specimens were fabricated, resulting in a total of twenty-four specimens. To minimize variability between samples, each group was manufactured as a single composite plate with nominal dimensions of 760 \(\times\) 380 \(\times\) 4 mm\({}^{3}\) (including error margins). These plates were subsequently machined into standardized specimens with dimensions of 150 \(\times\) 100 \(\times\) 4 mm\({}^{3}\), in accordance with ASTM D7136 [51], to ensure high dimensional accuracy for low-velocity impact testing. Special care was taken to ensure that the nanofiber-interleaved composite specimens contained a continuous nanofiber mat extending uniformly across the entire width and length of the sample. Low-velocity impact tests were performed in accordance with the ASTM D7136 standard using a custom-designed drop-weight impact tower equipped with a hemispherical impactor head of 12 mm diameter and a total mass of 5.6 kg. The specimens were centrally mounted in a rigid steel rectangular fixture and secured with four mechanical clamps to prevent movement during testing. The impactor was released from a height sufficient to achieve an initial velocity of 2 m/s, corresponding to an impact energy of 11 J.