RELATIONSHIP AMONG CHEMICAL CONVERSION, GLASS TRANSITION TEMPERATURE, AND MECHANICAL PROPERTIES OF EPOXY MATRIX COMPOSITES

摘要

This paper investigates the relationship among chemical conversion (α), glass transition temperature (T_g) and mechanical properties for two commercial carbon-fiber prepregs (CYCOM 977-2 UD and CYCOM 5215 PW). In order to obtain the mechanical properties, composite panels cured at different isothermal temperatures were cut into coupons and tested according to ASTM standard test methods for Combined Loading Compression (CLC) and Short Beam Shear (SBS). T_g for 5215 PW was obtained using an encapsulated sample rheometer (ESR). T_g for 977-2 UD was obtained using ESR and Differential Scanning Calorimeter (DSC), α for 977-2 UD was obtained using DSC. A correlation that agreed well with the empirical DiBenedetto equation in the form of Pascault and William was found between T_g and a for 977-2 UD and α-T_g master curve was derived subsequently. While T_g for both prepregs showed a gradual increase in value as the isothermal cure temperature increased; the results of the mechanical testing showed that, for a relatively wide range of isothermal cure temperatures (from 93℃ to 127℃ for 5215 PW and from 160℃ to 182℃ for 977-2 UD), the mechanical properties showed no statistically significant variations. As a result, the studied mechanical properties seem to be independent of T_g and a for a wide range of isothermal cure temperatures.