Durability study of carbon fiber reinforced polyurethane pultruded plates subjected to water immersion

Water absorption and thermal-mechanical properties of polyurethane (PU) resin and pultruded carbon fiber reinforced PU plates (CFPUs) were studied through immersion of specimens in distilled water at 20^oC, 40^oC and 60^oC, respectively. The water uptake of PU resin reached the water saturation about 2.43%, higher than that of an epoxy resin matrix for carbon fiber reinforced composites. PU possessed excellent tensile properties with a high elongation at break (~ 7%). Water immersion at 20^oC, 40^oC and 60^oC for 3 months reduced the tensile strength of PU resin by 29.2%, 20.1% and 11.8%, respectively. The less degradation at higher immersion temperature was attributed to the increased postcuring, which was supported by dynamic mechanical thermal analysis (DMTA) results. The saturation of the water uptake of the pultruded CFPU was realized in 1 month. In addition, after 1 month of immersion in water, the tensile strength of CFPU was not degraded. This indicates that the current CFPU shows super water resistance compared to the epoxy based plates.