Synergistic Thermal-Moisture Damage Mechanisms of Epoxies and Their Carbon Fiber Composites

Abstract

Experiments were conducted measuring the changes in weight of neat epoxy resins and carbon fiber reinforced epoxy composites during immersion in distilled water in temperature range from 0.5°C to 80°C. From the weight change data, the values of maximum moisture contents and diffusion coefficients were determined. Systematic studies were carried out on the "reverse thermal effect" for both neat resin and composite. A critical temperature was observed below which the materials exhibit normal behavior (the rate of absorption of water into epoxy resin increases with increasing temperature) and once the materials saturated with water at temperatures above it, the reversibility of reverse thermal effect was observed. A possible mechanism involving moisture-induced elastic cavities is suggested to explain the effect. The effects of water on Tg, thermal expan sion and yield stress of neat epoxy resin were studied.