A review of the emerging approaches for developing multi-scale filler-reinforced epoxy nanocomposites with enhanced impact performance

Fiber-reinforced polymer composites (FRPCs) are utilized for myriad applications owing to their exceptional characteristics like high specific strength and stiffness. However, the low-to-moderate impact strength of these materials is a major constraint restricting their usage in fields requiring high-impact performance. To ensure the reliable performance of FRPCs throughout the intended life span, a combination of good static mechanical properties and high impact resistance is crucial. Recent advancements in this field have yielded a breakthrough by developing novel materials that overcome this limitation. This groundbreaking achievement was realized by processing epoxy-based GFRPs containing a synergistic blend of surface-modified nano-clay and compatibilized polymeric fiber micro-reinforcement. This review provides an overview of advancements in the development of FRPCs, starting from the single-filler to multi-scale filler-reinforced materials. The review elaborates on the effect of reinforcement of various thermoplastic fibers (polyethylene, para-aramid, and spandex) on the mechanical performance of FRPCs. The necessity of filler compatibilization to enhance interfacial bonding constituents is also discussed. It can be concluded that the choice of surface treatment for a given thermoplastic fiber is governed by its chemical composition, the functional groups to be added on its surface through a specific compatibilization treatment, and the chemical nature of other constituents of the composite system with which the treated fiber surface interacts. Further, the greater the elasticity and ductility of the reinforced thermoplastic fiber, the higher the impact strength of the resulting epoxy-based GFRPs. Finally, the review brings forth the potential opportunities for future research in this area. Highlights: Discussed recent advancements in epoxy-based GFRPs with multi-scale filler reinforcement. Multi-scale filler-reinforced epoxy-based GFRPs have myriad applications in aviation, automobile, marine, sports, etc. Nano-/micro-fillers in their pristine state degrade the mechanical performance of epoxy-based GFRPs. Filler compatibilization is essential for achieving superior mechanical performance in epoxy-based GFRPs. Reinforcing compatibilized soft/ductile thermoplastic fibers resulted in a notable increase in impact strength while maintaining tensile properties.