Relationship between water absorption and dielectric behaviour of natural fibre composite materials

Gravimetric and dielectric measurements have been used to monitor water uptake in composites with glass, jute and washed jute fibres. The results showed that the dielectric constant of jute fibre composites is higher than that of the composites based on glass fibres. Also, when the frequency increases the permittivity decreases. A Fickian diffusion model was applied and the effective diffusion coefficient was calculated. The results obtained show that when the sizing is removed in fibres washed with hot water, the effective coefficient diffusion increases. Changes in the dielectric permittivity were measured at different frequencies and at different times during water absorption at room temperature. A non-linear behaviour has been found in the changes of the permittivity with water absorption in the frequency range of 200 Hz to 1 MHz.