Multi-scale moisture diffusion modeling and analysis of carbon/Kevlar-fiber hybrid composite laminates under the hygrothermal aging environment

Hybrid fiber reinforced polymer (HFRP) can have more complex micro moisture diffusion process than single fiber composite, owing to diverse hygroscopic properties of dissimilar fibers. Thus, elucidating the multi-scale moisture diffusion mechanism of HFRP through experimental method becomes a challenging endeavor. To this end, a multi-scale moisture diffusion modeling approach is proposed to investigate the moisture diffusion behavior of carbon/Kevlar HFRP under the hygrothermal aging environment. Leveraging Fick's law as a foundation, a combination of multi-scale moisture diffusion model and finite element method is employed. To validate the effectiveness of model, accelerated aging experiments are conducted on HFRP samples with various stacking sequences. By SEM characterization, the surface aging on aged Kevlar fibers and the debonding of aged fiber/matrix interface are conspicuously observed. Based on this model, the moisture diffusion behaviors in different HFRP configurations are simulated and analyzed to reveal the micro-, meso‑ and macro-scale moisture diffusion and resistance mechanisms. Our findings highlight the profound influence of factors such as fiber type, fiber content, fiber placement, hygroscopic properties of constituents, and their synergistic effects on moisture absorption and saturated moisture absorption rates. Finally, the hygroscopic properties of HFRP laminate with different stacking sequences are predicted by multi-scale model. This work endeavor furnishes valuable insights and guidelines for the design and analysis of moisture-resistant HFRP.