Single-layer woven carbon fibers improved the thermal and mechanical properties of epoxy resin

Abstract

Epoxy EPON 828 was reinforced with a single layer of carbon fiber fabrics and exhibited significant increase of thermal and mechanical properties. Two fabric types, twill 2/2 and 4-harness satin (4HS), were investigated. Epoxy of diglycidyl ether of bisphenol-A/epichlorohydrin, EPON 828 was cross-linked with 4,4’-diaminodiphenylmethane. The thermal decomposition temperature, Tdec, and the glass transition temperature, Tg, of the composites were increased relative to the neat epoxy, and the 4HS fabric increased Tdec and Tg over 60 K. The twill fabric increased fourfold the tensile Young’s modulus E and twofold the flexural modulus E’. In contrast, when adding a nonwoven glass fiber fabric, the tensile modulus only increased twofold, thus highlighting the unique reinforcement effect of woven carbon fibers. Scanning electron microscopy showed that the epoxy resin was well dispersed within the carbon fiber fabrics and the absence of matrix–fiber debonding indicated an efficient stress transfer between epoxy and carbon fibers. Dynamic mechanical analysis showed a shift to higher temperatures of the α mechanical relaxation, and the intensity of the mechanical damping was attenuated denoting restricted macromolecular motions, and this may explain the enhanced thermal and mechanical properties.