Synergistic Effect of Nano Silica and Carbon Nano Fiber Fillers on Mechanical Properties, Thermal Stability, and Ablative Properties of Carbon Fiber/Phenolic Resin Composites

Abstract

This experimental investigation evaluates the influence of Nano Silica (NS) and Carbon Nano fiber (CNF) fillers-individually and in hybrid form on the mechanical, thermal, and ablative characteristics of Carbon Fiber/Phenolic (CP) composites. Four laminates were fabricated: neat CP, CP/NS (5 wt %), CP/CNF (0.5 wt %), and hybrid CP/NS/CNF using the hand lay-up technique followed by autoclave curing. Comprehensive mechanical, physical, and ablative characterization was conducted in accordance with ASTM standards. Ablation resistance was assessed on an ox-acetylene test bed (OTB) at a heat flux of 500 W/cm², replicating severe thermal environments. The incorporation of nanofillers significantly enhanced the overall composite performance. Due to synergetic effect among the fillers, the hybrid (CP/NS/CNF) composite exhibited the greatest improvements, with interlaminar shear strength (ILSS) and Flexural strength (FS) increased approximately by 26 % and 11 %, respectively, relative to the neat composite. Thermo gravimetric analysis (TGA) confirmed superior thermal stability, while linear erosion and mass ablation rates were reduced by 23 % and 18 %, respectively. Scanning Electron Microscopy (SEM) of ablated surfaces revealed improved structural integrity and reduced matrix degradation, elucidating the synergistic reinforcing mechanism for the hybrid composite. These findings demonstrate that hybrid reinforcement with nano fillers is an effective strategy to tailor the properties of CP composites for high-temperature aerospace and thermal protection applications.