Enhancement of Fracture Toughness in Carbon Fiber/Epoxy Composites Through the Incorporation of Two Distinct Nano Particles with Varying Structures

The effect of two types of nano fillers with different characteristics was studied on the toughness of imidazole/epoxy (IMI/EP) resin system and their carbon laminates. One is rigid core/plastic shell, the other is plastic core/rigid shell. The influence of nano particles on fracture toughness (KIC), energy (GIIC), thermal mechanical properties (DMA), and curing behaviors were investigated. The nano fillers, SiO2 and core–shell rubber nano particles (CSR) did not lower the glass transition temperature (Tg). Both KIC and GIIC were increased after the addition of nano fillers. The mechanisms of these improvements in toughness were explored using optical microscopy (OM) and scanning electron microscopy (SEM). It was revealed that the improvement of fracture toughness with addition of nano particles was due to debonding and deformation of the nano particles. Subsequently, the crack growth was hindered by the nano particles, and the stress energy at crack tip was released by crack deflections, particles deformation and particles rupture. Finally, the curing behavior of the epoxy resin with different types of nano particles was studied using DSC. The crosslinking reaction rate slowed down with the addition of SiO2 and CSR.