Fiber Bundling in SiO₂ Particle-Modified Glass Fiber Felt Composites Enables Synergistic Enhancement of Short-Beam Shear Strength and Thermal Insulation

This study tackles challenges in improving both thermal insulation and short-beam shear strength (SBSS) of glass fiber felt composites (GFFCs). It proposes modifying glass fiber felts with silica (SiO₂) particles using a waterborne epoxy sizing agent. SiO₂ particles (0, 5, and 9 wt%) were loaded onto fibers using ultrasonic-assisted dispersion. Sandwich composites were then made by the vacuum-assisted resin transfer molding (VARI) process. Results indicate SiO₂ modification changes the interface structure. Dense fiber bundles formed in the 9 wt% samples. XPS-confirmed increased polar groups. The C-O/C-C ratio rose from 0.32 to 0.54. This structure increased SBSS by 28.8%, from 4.62 to 5.95 MPa. The failure mode also changed from fiber pull-out to combined resin/fiber fracture. Thermal conductivity decreased significantly in the thickness direction by 24.3%, from 0.1938 W/(m·K) to 0.1467 W/(m·K). However, the decrease was only slight in the in-plane direction. This physical strategy achieves mechanical reinforcement and heat flow control through fiber bundling. It offers a new approach for low-cost, large-scale production of high-performance thermal insulation structural materials.