Impact of natural variability of flax fibres properties on mechanical behaviour of short-flax-fibre-reinforced polypropylene

Short-flax-fibre-composite materials are appealing for technical applications thanks to renewability, biodegradability but also potentially high ratio rigidity/density of flax fibres, in particular. However, the significant variability of technical flax fibres’ constitutive, geometrical and mechanical properties and especially lack of quantitative knowledge about its real impact on composite behaviour still prevent a widespread use of such composites. To overcome this obstacle, this study gives qualitative and quantitative information about impact of variability of flax fibre properties on numerically assessed tensile behaviour of short-flax-fibre-reinforced polypropylene, with particular attention paid to the determination of lower bound of composite behaviour. Different fibre contents and orientations, including in-plane random and distributed orientations, are considered. Results reveal that range of variation of composite behaviour strongly depends on weight of fibre contribution to composite response. It is therefore directly related to fibre content and orientation but also indirectly to manufacturing process, since this latter governs fibre orientation.