Multi-walled carbon nanotube(MWNT)/poly(methyl methacrylate) composites was fabricated by film casting under different nanotube concentrations. It was confirmed that the nanotubes were well dispersed in PMMA by viewing SEM image. The mechanical improvement of composites with various MWNT concentrations was studied; moreover, The increase of the electric conductivity was researched. As the MWNT concentration increased from 0 to 0.15 wt%, the strength of MWNT/PMMA nanocomposites showed about 20% of improvement and their modulus showed about 32% of improvement. The tensile modulus was estimated by using Tsai and Pagano equation which has been used for short fiber composites. However, the estimated results were not consistent with the test results because MWNTs in this research were not stretched straightly but entangled ones, that is, MWNT could not be assumed to be a short fiber, and the concentration of MWNT is too small to be compared with that of the common composites.
