It is well known that the plastic gears have some advantages, that is lightweight, low noise and operation of oil-less conditions. But plastic gears have been used only low torque conditions. As FRP gears have acquired higher strength and stiffness than the plastic gears, FRP gears are now attracting attention and they have replaced metallic gear in order to reduce weight and noise. Although there have been many researches on metallic gears, we have seen few reports about FRP gears. At present, FRP gears are designed mainly based on few test data of plastic gears and experiences that engineers have. In this research, we investigated the bending fracture characteristic of FRP gears to develop design criterion for FRP gears. According to the experimental results, it is clear that tensile, compressive and shear strength of FRP materials were needed to estimate the tooth bending strength.
