Evaluation of Ablation and Mechanical Behavior in Needle-Punched High Silica-Phenolic Composites With Comparison to Laminated Structures

This study aims to prevent delamination of high silica-based phenolic ablative composite by needle punch technique and silica felt structure. Conventional laminate and needle-punched (NP) configurations were both experimentally investigated for their mechanical response and torch-ablation behavior in high-silica (HS) fiber reinforced phenolic composites. A series of HS fabric–felt preforms with different fabric/felt layer ratios and fiber volume fractions were manufactured using a laboratory needle-punching set-up, impregnated with phenolic resin by vacuum assisted resin transfer molding (VARTM) and consolidated by hot pressing. For each configuration, tensile, short-beam shear, and three-point bending tests were performed, together with oxy-propane torch tests to determine linear and mass ablation rates. Compared with the baseline laminate reference, the needle-punched configurations exhibited a 25–60% reduction in tensile strength and up to about 25% lower flexural strength, whereas the interlaminar shear strength obtained from short-beam tests increased by as much as 40–50% due to the improved through-thickness fiber bridging. In parallel, the non-needle-punched silica fabric–silica felt configuration showed only a modest decrease in tensile and flexural strength compared with the reference laminate while maintaining a relatively high interlaminar shear capacity, suggesting that this simpler, more easily manufactured configuration can be considered a practical alternative when processing robustness and cost are prioritized over maximum delamination resistance. According to ablation measurements, the laminate displayed the strongest ply-by-ply separation and the highest linear ablation rate. While maintaining similar tensile and flexural performance, an optimized needle-punched configuration with a balanced fabric/felt stacking sequence and a fiber volume fraction of roughly 60–65% decreased the mass ablation rate by roughly 40–50% and the linear ablation rate by roughly 90% in comparison to the laminated reference. Needle-punched composites produced a more stable char layer and considerably reduced delamination during extreme heat loading, according to post-test inspections. Overall, the results demonstrate that appropriately designed needle-punched HS/phenolic composites offer a substantial improvement in delamination resistance and ablative performance without sacrificing mechanical properties, making them strong candidates for thermal-protection components in aerospace applications.