Hygroscopic multi-scale analysis and degradation of bamboo fiber composites

Résumé fourni par la source

This paper addresses the multiscale moisture absorption and degradation of bamboo fiber–epoxy composites with different fiber fractions (20, 30, and 40 wt.%). The equilibrium moisture absorption of composites has been studied at different relative humidities (30%, 65%, and 80%) using a multiscale homogenization method. The findings reveal that the overall macroscopic property does not obey the classical law of mixtures, which is attributed to the hygro-mechanical coupling arising from the matrix-induced confinement effect. This response is strongly governed by both fiber fraction and humidity levels. The results indicate that the classical Fick model is sufficient to describe the experimental moisture uptake. Interestingly, the predicted hygroscopic stress distributions reveal increasing tensile and compressive stress levels with fiber content, driven by the combined effects of moisture concentration gradients and enhanced hygroscopic expansion. Herein, compressive stress reaches 46.46, 66.91, and 105 MPa in the surface regions during the transient regime for 20, 30, and 40 wt.% fiber composites, suggesting an increased risk of damage initiation even without adding external loads, respectively. More importantly, good retention of the tensile properties is noticed for 20 and 30 wt.% fiber composites after exposure to wet–dry aging, suggesting that fiber expansion and leaching are the dominant mechanisms. However, microstructural damage and active hydrolysis reactions drive the recovery at 40 wt.% fiber fractions. The damage parameter used to reflect the loss of tensile strength reaches values of 0.034, 0.054, and 0.169 at 20, 30, and 40 wt.% fiber fractions, indicating progressive damage with increasing fiber content, respectively.