Durability study of ramie fiber fabric reinforced phenolic plates under humidity conditions

Abstract A durability study of a ramie fiber fabric reinforced phenolic resin (RFRP) plate under 50%, 85%, and 98% relative humidity for 6 months at room temperature was performed. Water absorption and desorption, tensile and short beam shear strengths of the RFRP plates were investigated as a function of exposure time. RFRP samples show strong hydrophilic characteristics and the saturated water content varies from 0.73% to 4.5% with relative humidity ranging from 50% to 98%. After 6 months of exposure to 98% relative humidity, an abnormal extra amount of moisture was absorbed, which may have resulted from cracks in the resin matrix or from debonding between fiber and resin due to swelling of the fibers with high moisture content. It was found that the tensile modulus is more susceptible to moisture uptake, which is ascribed to the degradation of ramie fibers with the water ingress. An approximate linearity between the mechanical properties and the moisture content is observed if the abnormal extra water uptake is neglected. Both tensile and short beam shear strengths of the RFRP samples recovered remarkably when samples were fully dried at 60°C, indicating a low degree of permanent degradation occurred due to the exposure.