Effect of micro-scale fibre uncertainties on the mechanical behaviour of natural/synthetic hybrid fibre composites

This paper investigates how uncertainties in natural/synthetic hybrid fibre composites— specifically fibre distribution, diameter, and elastic properties—affect the lamina properties and micro-stress distributions. Using a representative volume element model and Monte Carlo simulations, the study examines unidirectional flax/E-glass/epoxy and flax/epoxy composite laminae. Flax fibre uncertainties are modelled as normal distributions with a 20% coefficient of variation. Results reveal that these uncertainties minimally influence the homogenised properties of flax/epoxy laminae. However, in flax/E-glass/epoxy laminae, E-glass fibres significantly alter homogenised properties, with fibre elastic properties uncertainties having a greater effect. These uncertainties also influence matrix stress fields in flax/epoxy laminae, primarily due to uncertainties in fibre elastic properties. Although the influence is smaller in flax/E-glass laminae, it remains significant, as hybridisation can increase von Mises stress and potentially cause early resin cracking. This stochastic approach highlights the importance of micro-scale fibre uncertainties for damage analysis despite their limited influence on homogenised properties.