Effect of Nanosilica on Bending Strength and Thermal Stability of Glass Fiber/Phenolic Nanocomposite

Glass fiber/phenolic composites are effectively used as heat shields for fabrication of cooled combustion chambers. To improve the performance of these composites as well as to lower their costs, the use of nanosized silicon dioxide (SiO2) particles has been adopted. In this work, we investigated the effect of nanosilica on properties, heat stability and ablation properties of glass fiber/phenolic composites. Glass fiber/phenolic/nanosilica composites were made of 1, 2 and 3 wt% of well-dispersed silica nanoparticals in a phenolic resin. The average size of silica nanoparticals was 45 nm. These nanocomposites were prepared by hot-press process. Ablation properties of the composites were studied by oxy-acetylene torch environment and their mass and linear erosion rates were evaluated. The thermal stability of the produced composite structures was examined by means of thermal gravimetric analysis in air with dynamic scans at a heating rate of 10°C/min from room temperature to 800°C. Bulk samples, of about 20 ±1 mg each, were tested. The results indicated that nano-SiO2 increased the thermal stability of nanocomposites so that their linear and mass erosion rates after modifying with 3 wt% nanosilica dropped by 58% and 53%, respectively. The 3-point bending test results showed that bending strength and modulus of the as-received composites increased with percentage nanosilica added up to 2 wt%, beyond which they decreased. For the glass fiber/phenolic composites with 2 wt% nanosilica particles, embedded in the matrix, strength and modulus increased about 40% and 19%, respectively, in comparison to those for neat glass/phenolic composite.