Epoxy with different mix ratio of volume fractions 1, 3, 5, 7, and 10% of SiO2 nanoparticles and microparticles were used to prepare epoxy nanocomposites and microcomposites in order to examine and study their Impact strength. The molding method was used to prepare epoxy and their nanocomposites and microcomposites specimens using shearing mixer, ultrasonic homogenizer and vacuum system. Charpy impact test was used to test epoxy and their nanocomposites and microcomposites.Results obtained from charpy impact test shows that Impact strength of EP/SiO2 nanocomposites was increased with increasing volume fractions of SiO2 nanoparticles in random manner. It was noticed the Impact strength reach to maximum values (20.11 KJ/m2) at 3% vol. of SiO2 nanoparticles, then decrease with increasing volume fraction of SiO2 nanoparticles, but the results of Impact strength still higher than that of neat epoxy. Brittle fracture still appears at specimen surface obtained for EP/SiO2 nanocomposites. Also the results showed that the specimen of EP/SiO2 microcomposites reach to maximum values (6.74KJ/m2) at 3% vol. of SiO2 microparticles than the other specimens, then Impact strength values decrease with increasing volume fraction of SiO2 microparticles. In comparison the composites with silica nanoparticles exhibits higher mechanical properties than the composites containing micro size silica particles. However, the fatigue life is generally better for nanocomposites than for micorcomposites. However, the Impact strength is generally better for nanocomposites than for micorcomposites.
