Can plant fiber composites outperform glass and carbon fiber composites in terms of stiffness-damping trade-off?

This study investigates the influence of fiber volume fraction on the viscoelastic behavior of flax–GreenPoxy composites, with a focus on damping characteristics relevant to vibration sensitive structural applications. Composites with 25%, 35%, and 47% fiber volume fractions are characterized using dynamic mechanical analysis, modal analysis, and quasi-static measurements, and the experimental results are interpreted in parallel with multiscale homogenization simulations. The results show that increasing the plant fiber volume fraction leads to enhancement of the longitudinal storage modulus as expected, while the damping factor remains nearly unchanged at about 1.5% over the tested range. This behavior contrasts with that of conventional synthetic fiber composites, in which increasing fiber content typically results in a significant reduction in damping. The combined experimental and numerical approach provides a consistent understanding of how fiber content governs the viscoelastic response of plant fiber composites. Furthermore, analysis of the loss modulus demonstrates that plant fiber composites exhibit a more favorable stiffness–damping trade-off, outperforming glass fiber composites while approaching the dynamic performance of carbon fiber composites, highlighting their potential for vibration-sensitive structural applications.