Nanoparticles in Glass Fiber‐Reinforced Polyester Composites: Comparing Toughening Effects of Modified Graphene Oxide and Core‐Shell Rubber

The role of nanoparticles in the fracture toughness of glass fiber‐reinforced polyester composites (GFRPs) was investigated. An unsaturated polyester resin (UPR) and a vinyl ester resin (VER) were toughened by two distinct methods: (1) incorporating a very low loading (0.04 wt%) of alkyl or vinyl modified graphene oxide (mGO); or (2) adding core‐shell rubber (CSR, 1 and 5 wt%). For unreinforced resins, results from compact tension tests revealed that adding 0.04 wt% of mGO increased the fracture toughness (GIC_Resin) of UPR and VER by as much as 49 and 35%, respectively, without lowering the modulus and glass transition temperature (Tg); however, the mode I interlaminar fracture toughness (GIC_Comp) of GFRPs was not improved. On the other hand, CSR is a more effective toughener, though at much higher loadings. 1 wt% had little effect, but 5 wt% of CSR enhanced GIC_Resin of UPR and VER by 280 and 600%, respectively, with a significant decrease in flexural modulus and flexural strength. 5 wt% of CSR was not able to increase the GIC_Comp of UPR laminates either; however, CSR did increase the initiation GIC_Comp and propagation GIC_Comp of VER laminates by 50 and 33%, respectively. Scanning electron microscopy of the fractured specimens revealed weak fiber–matrix bonding for all GFRPs. This work suggests that enhancing fiber–matrix bonding is critical to gain the benefit of adding nanoparticles to GFRPs. POLYM. COMPOS., 40:E1512–E1524, 2019. © 2018 Society of Plastics Engineers