Flax Composites With Improved Interfacial Strength Through Microbially Induced Mineral Precipitation.

Driven by the needs of modern transportation and the clean energy transition, the demand for sustainable and lightweight materials is increasing. Composite materials incorporating natural fibers such as flax fibers have gained attention due to their carbon-capturing potential and good specific mechanical properties. However, when embedded in hydrophobic polymer matrices, flax fibers exhibit inferior mechanical performance primarily due to their hydrophilic composition and discontinuous fiber architecture. Biological materials such as nacre have developed useful strategies through mineralization to distribute localized stresses and develop extrinsic toughness that could inspire a solution to enhance stress transfer in natural fiber composites. Here, we report a biomineralization strategy to introduce an additional hierarchy to flax composites. By tuning salt concentrations in the process, we achieve controlled deposition of microbe-mediated mineral particles on flax yarns. With controlled biomineralization, we show that the minerals can enhance the compressive toughness by 178% and compressive strength by 30%. The findings highlight a novel bio-inspired pathway for tailoring composite performance through sustainable processing, offering a scalable and environmentally friendly approach to enhance natural fiber composites for structural applications.