In this paper, a polymer-based composite material was prepared by hand Lay-up method consisting of epoxy resin as a base material filled with by magnesium oxide powder once and silicon dioxide powder again and with different weight ratios (3%, 6%, 9%, 12%). The three-point bending test was performed in normal conditions and after immersion in sulfuric acid. The results showed that the bending value decreased with the increase of the weighted ratio of the filled nano powder (MgO, SiO 2) .The Bending of samples filled with by SiO 2 was found to be less than the bending of samples filled with by particles (MgO), the bending of the SiO 2 sample (0.32mm) at the weighted ratio (3%) and for the MgO (0.18mm) sample at the weight ratio were the same at the same weighted load (100 g). It was found that the bending values of all samples exceeded the value after immersion in sulfuric acid. The percentage of weight (6%) at the load level (500 g) was changed from 1.16mm in normal conditions to 1.48mm for the same weight ratio after immersion. In sulfuric acid diluted with 0.3N for 10 days at the same Applied load.