Numerical Modeling Strategies in Flax Fiber-Reinforced Polypropylene Forming Processes

Natural fiber-reinforced thermoplastic composites have gained increasing attention due to the abundant availability of natural fibers, their ability to effectively reinforce polymer matrices, and the resulting partial biodegradability of the final material. This study presents numerical modeling strategies for investigating the manufacture of spherical caps made from polypropylene composites reinforced with woven flax fabrics. The investigation considers both cold incremental forming and stretch-forming processes, performed either with or without the support of a partial counter die. Building on the findings of a previous experimental study conducted by the authors on compression-molded laminates manufactured using untreated woven flax fabrics and without coupling agents and formed without localized heating, numerical predictions are compared with experimental results in terms of final geometry, forming forces, and failure mechanisms. The findings highlight the need for a thorough understanding of material behavior to fully exploit finite element analysis as a reliable predictive tool in the forming of these innovative lightweight composite structures.