Moisture absorption effects on the mechanical properties of carbon/epoxy composites

Purpose This paper investigates the influence of moisture absorption on the mechanical properties of carbon/epoxy composites. Design/methodology/approach Three types of specimens are prepared, which are for longitudinal, transverse and shear tests. Specimens are immersed in distilled water at 70 degrees C for 1, 3 and 9 months. These correspond to the moisture content of 2.2, 3.8 and 5.3%. Findings Compared to the values at dry condition, the longitudinal modulus, shear modulus and Poisson's ratio are invariant with the moisture content. However, the transverse modulus, transverse strength and shear strength are sensitive to moisture attack. The maximum degradation is 33%, 76 and 33% for the three properties, respectively. It is also worth to note that the longitudinal tensile strength is stable at 1 and 9 months of immersion. However, at 3-months ageing period, there is only 67% of the longitudinal tensile strength retained. Originality/value The experimental results are fitted with a residual property model. Results show comparatively good fit, with a difference within 16% except the longitudinal tensile strength at 9-months immersion. This highlights that the model is not suitable to fit the experimental data with a fluctuated trend.