Hygroscopic Behavior of Woven Fabric Carbon-Epoxy Composites

The hygroscopic behavior of a woven fabric carbon-epoxy composite and its effect on the viscoelastic properties and glass transition temperature was investigated. The mechanical and thermal properties of the material had been previously fully determined. An experimental study was conducted at full immersion in water and at a specific temperature condition. The moisture absorption process was found to be reversible with a low-saturation moisture uptake. The absorption through-the-thickness was determined to be lower than in the in-plane directions. The coefficients of moisture expansion or hygroelastic coefficients were determined and found to be similar in the warp and fill directions and much lower than through-the-thickness direction. The results were correlated to the behavior of a unidirectional composite with the same fiber and matrix. The viscoelastic properties were not affected during the process but the plasticization was very pronounced.