The Effects of Curing Cycles on Properties of the Epoxy System 3221/RH Glass Fabric Composites

摘要

In this work, the epoxy system 3221 and its glass fabric laminates were thermally cured under different curing temperatures. The curing degree of the resin was increased with elevated reaction temperature. Dynamic mechanical analysis was performed on the laminate coupons and glass transition temperature (T_g) and relative stiffness (E') of composites were measured before and after soaked in distilled water at 70°C. A shift in glass transition temperature to higher values and the splitting of the tan δ curve were observed with extent of cure under dry conditions. T_g values shifted to lower temperatures after immersion. Under wet condition, the change in T_g1 was very small when the curing degree was up to 96%. The relative stiffness experienced a reduction both in initial modulus and the initial sharp drop temperature after immersion. It also suggested that the excessively high curing temperature (>130°C) had a negative effect on the retention of relative stiffness under wet condition. Both the interlami-nar shear strength and dielectric properties of laminates were determined before and after immersion. The compared results demonstrated that the elevated curing temperature played a good influence on both of the properties before aged. However, for samples cured above 130°C, lower retention of interlaminar shear strength and poor dielectric properties were observed during immersion due to their higher moisture contents.