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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. [ABSTRACT FROM AUTHOR]

The mechanical properties of the glass fiber reinforced Polyamide (PA6) composites made by prepreg tapes and commingled yarns were studied by in-plane compression, short-beam shear, and flexural tests. The composites were fabricated with different fiber volume contents (prepregs-47%, 55%, 60%, and commingled-48%, 48%, 49%, respectively) by using vacuum consolidation technique. To evaluate laminate quality in terms of fiber wet-out at filament level, homogeneity of fiber/matrix distribution, and matrix/fiber bonding standard microscopic methods like optical microscopy and scanning electron microscopy (SEM) were used. Both commingled and prepreg glass fiber/PA6 composites (with Vf ∼ 48%) give mechanical properties such as compression strength (530-570 MPa), inter-laminar shear strength (70-80 MPa), and transverse strength (80-90 MPa). By increasing small percentage in the fiber content show significant rise in compression strength, slight decrease in the ILSS and transverse strengths, whereas semipreg give very poor properties with the slight increase in fiber content. Overall comparison of mechanical properties indicates commingled glass fiber/PA6 composite shows much better performance compared with prepregs due to uniform distribution of fiber and matrix, better melt-impregnation while processing, perfect alignment of glass fibers in the composite. This study proves again that the presence of voids and poor interface bonding between matrix/fiber leads to decrease in the mechanical properties. Fractographic characterization of post-failure surfaces reveals information about the cause and sequence of failure. POLYM. COMPOS., 36:834-853, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]