Tensile and fracture properties of epoxy alumina composite: role of particle size and morphology

Epoxy composites reinforced with three different shapes of Al2O3 nanoparticles were synthesized by instant cross-linking process. Out of three types of Al2O3 particles, two were of rod shape particles termed as large nano rod (diameter 2-4 nm and length 100-200 nm), and small nano rod (diameter of 5-10 nm and length less than 50 nm) and third particle was spherical in shape (diameter of 27-43 nm). 0.5, 1.0, and 1.5 wt.%. of reinforcement was maintained constant. Reinforcement of low (1.0) wt.% of spherical Al2O3 nanoparticles is more promising in enhancing tensile strength and failure strain of epoxy composite. At 1.0 wt.% reinforcement of spherical Al2O3 nanoparticles, tensile strength and failure strain are improved by 10% and 29%, respectively. Quasi-static fracture toughness of epoxy composite was improved by reinforcement of all three types of Al2O3 nanoparticles. Fracture toughness of epoxy composite was enhanced by 52% at 1.5 wt.% inclusion of large Al2O3 nano rod. Crack deflection and crack bridging were the micro-mechanics accountable for improved fracture toughness of spherical Al2O3 composite. Crack tilting and twisting, particle pull out, along with crack deflection were the main contributors for increased fracture toughness of composites of Al2O3 nano rods.