Silicium carbide (SiC) is one of the most important materials in composite and electronic applications. SiC has good properties, such as high thermal resistance, semi conductivity, good wear resistance and suitable mechanical properties (high hardness and modulus). SiC is synthesized by a reaction between silica and coke at very high temperature, from this product such as fibers, microparticles and recently nanoparticles nanowhiskers can be produced. SiC has many usage in industries, such as semi conductor in electronic devices, cutter tools, heat resistance materials and ceramic polymeric composites. Also thermoset composites (specific epoxy based composites) have many application in aerospace industry. SiC nanowhiskers are new product of this material that have high aspect ratio (L/D). in this research, 0.5, 1, 2, 4 wt% SiC nanowhiskers, nanoparticles microparticles filled nanocomposites were made using Epoxy resin as matrix and ultrasonic processor for their dispersion. The influence of particle size from micro to nano and aspect ratio from nanoparticle to nanowhisker on the physical-mechanical properties were investigated. Measurement and characterization were carried out using tensile, flexural, wear, hardness, DSC, FT-IR, XRD and SEM methods. Ultrasonic increased mechanical properties by about 5% due to sono-chemical effects. Addition of microparticles by 1 wt% caused an increase of 15% in tensile and flexural modulus and 25% in strength. Higher content of microparticles reduced the achieved mechanical properties, it is due the particles interaction. As for nanoparticles 1 wt% content produced 17% increase in modulus and 27% increase in strength, this is due to smaller particle size and higher specific area. Reduction in properties were obtained using higher content. For nanowhisker composites for 2 wt% an increase on 35% in tensile and flexural properties and a reduction with higher content were achieved, this could be due to higher aspect ratio as compared with nanoparticles. tensile result of composites were compared with teorical models (in particulated and fiberus composites) such as guth, caron, cox and young. Also the mechanical results have been investgated by statistical analysis (two way Anova) that underscore the effects of fillers and their wt% changes. Nanoparticle composites had higher tribological properties (wear and friction) than neat epoxy resin at pin on disk test, they also offered better tribological properties compared with nanowhisker composites, this is related to their spherical shape and increase of surface slip by particles. Hardness and DSC test results don’t show any changes in hardness or glass transmission temperature with particle loading in epoxy nanocomposites.