Improving Mechanical Properties of Glass Fiber Reinforced Polymers through Silica-Based Surface Nanoengineering

Glass fiber reinforced polymer (GFRP) composites are widely used materials in structural and transport applications owing to their excellent strength-to-weight ratio. In GFRPs, mechanical properties are mainly governed by the filler-to-matrix interphase region, which need to be rationally designed and carefully engineered to optimize the composite performance. However, the structural and chemical parameters that optimize mechanical performance are partially unknown. Here, we report on different surface nanoengineering strategies and their effect on the mechanical properties of GFRPs. Commercial woven glass fibers (wGFs) are modified with several distinct silica-based nanostructured coatings that provide different pore sizes, surface areas, and adhesion energies. To study their mechanical properties, epoxy-wGF laminated composites are manufactured and characterized using sliding contact, tensile, and three-point bending tests. Composites based on coated wGFs generally show improved mechanical performance over those based on bare wGFs. In particular, wGFs coated with mesoporous silica films display the highest specific surface areas, pore sizes and adhesion energies and provide the highest Young's and flexural modulus, with up to 31% improvement with respect to composites based on bare wGFs. The improvement of the composite's mechanical properties with the wGFs coating is related to a better stress distribution and a homogeneous loading transfer at the polymer-GF interphase. Overall, this study provides insights on how GFRP's mechanical properties can be boosted beyond the current state-of-the-art by the rational design of its interphase.