Hygrothermal properties of ramie fiber/phenolic resin composite under different hygrothermal conditions

Ramie fiber fabric reinforced phenolic resin composite laminates were prepared, and the moisture absorption, diffusion properties and mechanical properties were studied under different hygrothermal conditions. Results show that instantaneous moisture absorption rate of the laminate increases with the increase of relative humidity at 20°C, 40°C and 60°C, and that the temperature has unobvious effect on the hygrothermal properties of the laminate under 50% relative humidity. When the moisture absorption fraction is less than 0.5, the moisture diffusion coefficient of the laminate are 2.16×10^-6 cm²/s, 2.94×10^-6 cm²/s and 6.61×10^-6 cm²/s respectively under the temperatures of 20°C, 40°C and 60°C, and the relative humidity of 50%. The mechanical properties of the laminates decrease with the increase of the moisture absorption rate. The SEM photographs indicate that the moisture absorption damages the interface adhesion between fiber and resin of the composite, resulting in weak stress transferring between the fiber and the resin matrix.