A study of mixed mode interlaminar fracture on nanoclay enhanced epoxy/glass fiber composites

Fiber reinforced laminate are widely used in aerospace, automobile and marine industries, despite its poor interlaminar fracture toughness (IFT), as consequence of the absence of fibers to sustain transverse load. One way recently explored with relative success in order to improve IFT is the use of nanoparticles to reinforce the matrix. Present paper intends to assess and discuss the fracture toughness on mixed mode loading of fiber glass mats/nanoclay enhanced epoxy matrix laminates. The matrix used was the epoxy resin Biresin® CR120 combined with the hardener CH120-3, the fiber glass was triaxial mats ETXT 450 and the nanoparticles were montmorillonite nanoclay (NC). The results were discussed in order to understand the effects of the percentage of nanoclay and the shear load quantified in terms of the GII/GI ratio on the total fracture toughness G. The incorporation of a small quantity of NC into matrices improves significantly mixed-mode IFT for all loading mode ratios GII/G. The total fracture toughness G increases with the mode II loading component and a linear mixed-mode fracture criteria reproduces the Gc against GII/G relationship.