Water diffusion in carbon fiber reinforced polyamide 6 composites: Experimental, theoretical, and numerical approaches

Diffusion of moisture through composites is one of the main environmental causes of their deterioration and loss of service life. This paper deals with water diffusion in the unidirectional continuous carbon fiber reinforced polyamide 6 composites by experimental measurement, theoretical analysis, and numerical simulation. Immersion experiment is respectively conducted in distilled water at 25°C, 70°C, and 95°C for the pure polyamide 6 resin and the carbon fiber/polyamide 6 composite. Then, the theoretical Fickian and Langmuir models are employed to fit the gravimetric data of the specimens. Subsequently, water diffusion in the composite is also simulated using finite element method. Moreover, to capture the real distribution of fibers in the matrix, the random algorithm is developed to generate the computational composite models with randomly dispersed fibers. Finally, the comparison between the experimental, theoretical, and numerical results is made to assess the applicability of theoretical models and the influences of fiber distribution and interphase on the effective water diffusion coefficient of composite.