Moisture effect on tensile and low‐velocity impact tests of flax fabric‐reinforced PLA biocomposite

This study investigates the hygrothermal aging effect on the tensile and impact behavior of flax/PLA biocomposites. Specimens underwent up to four weeks of conditioning at 40°C in a climate chamber with water. Analysis covered porosity, moisture diffusibility, and transversal microstructure, enabling assessment of tensile strength, tensile modulus, and impact performance in relation to moisture uptake and fiber orientation. The study of tensile properties revealed that at approximately 12% moisture content, stiffness and yield stress decrease, while strength remains constant. Moisture diffusivity is higher in warp and weft yarn directions than the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture reveals greater stiffness in the weft direction, correlated with lower crimp percentage and yarn angle. The main contribution of the paper is the study of the influence of moisture on the impact behavior, the results show that energy absorption capability of flax/PLA biocomposite increases with moisture content. Highlights Fully biodegradable composite material by heat‐compression molding subjected to hygrothermal aging conditions for up to four weeks. The moisture diffusivity in both the warp and weft yarn directions registered higher values in comparison to the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture revealed that the stiffness in the weft direction presented higher values. At 12% of moisture uptake, the stiffness and yield stress reached their lowest values, while strength remained constant. However, the low‐velocity impact properties of the composites exhibited improvement with moisture.