Cyclic fatigue crack propagation of nanoparticle modified epoxy

An experimental study on the fatigue performance of nanoparticle modified epoxy was conducted. Seven material systems were examined which were: neat epoxy (E), 6 and 12 weight percent (wt.%) silica nanoparticle modified epoxy (S6, S12), 6 and 12 wt.% rubber nanoparticle modified epoxy (R6, R12), 3 wt.% each of silica and rubber nanoparticle modified epoxy (S3R3) and 6 wt.% each of silica and rubber nanoparticle modified epoxy (S6R6). Effects of those nanoparticles on the fatigue threshold (ΔGth and ΔKth) and fatigue crack propagation rates (da/dN) were studied. It was found that, compared to neat epoxy (E), nanosilica (S6, S12) increased ΔGth (and ΔKth) but nanorubber (R6 and R12) did not. However, a synergistic effect was observed on the fatigue threshold when both silica and rubber nanoparticles were added into epoxy. All these nanoparticles, individually or conjointly, decreased da/dN with silica the most effective. Morphology of the fracture surface was examined to understand the role of nanoparticles on toughening mechanisms under cyclic loading, which depended on the applied ΔG levels.