Life-Prediction of Resins for FRP Matrix in Corrosive Environments

The estimation method of life of resin for FRP matrix based on flexural strength in a corrosive environment was studied. The corrosion tests of iso-phthalic unsaturated polyester resin and epoxy resin cured with various contents of phthalic anhydride and accelerator were carried out by immersing into KOH solution. These resin systems showed the surface-reaction type or corroded-layer forming type corrosion. The thickness of specimen or corroded-layer decreased with increase of immersion time linearly. The effects of concentration of KOH solution, composition of resin system, and temperature on the rate of decrease of the thickness were investigated. The estimation method of life was proposed for surface reaction type resin and corroded-layer forming type resin without pits or cracks, which was based on considering the effects of various factors on the corrosion rate. For corroded-layer forming type resin with pits of cracks, a method which estimates the life for safer side was obtained by assuming the corrosion rate equal to the growth rate of cracks.