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Highlights Three dimensional (3D) textiles are preferable reinforcing materials for composites with lightweight and higher mechanical properties. In this study, a 3D woven flax fiber reinforced PLA composite with better flexural and tensile properties was developed. Four hybrid yarns with varied PLA contents were prepared as warp, weft and z‐yarns to weave the 3D preform and then changed to composites through compression molding technology without additional fillers and matrixes. The composite's flexural and tensile properties were studied and an optimum value of 78.0 and 140.0 MPa respectively were found. Stress strain properties were also discussed which implies the flexural elongation is higher than those of tensile values. The microstructure was analyzed using optical microscope and SEM equipment's showed composites with higher PLA content were more brittle due to the PLA inimitable behavior. The thermal properties of the 3D composites made with different Flax/PLA combinations have closer and comparable values. One way ANOVA statistical analysis was done to show the significancy of PLA /Flax mass ratio, which has a significant effect on composite's properties. This study could bring a novel procedural approach for an advanced 3D woven composites for load bearing applications. 3D woven flax /PLA composite was developed using Flax/PLA hybrid yarns Tensile and flexural properties were studied Flexural strength increases with PLA, but, slightly lower in its strain PLA/Flax mass ratio has a significant effect on composite's properties The mechanical strengths were improved compared to the related findings [ABSTRACT FROM AUTHOR]

In this research work, the natural fiber reinforced hybrid epoxy composites were fabricated using the hand lay‐up method. The flax and kevlar are used as a reinforcement and epoxy as a binding material. This study aims to analyze the influence of stacking sequence and hybridization on the mechanical, water absorption, and morphological properties of polymer composites. The results reveal that the neat kevlar reinforced composite achieved a maximum tensile strength, modulus, and impact strength of 189.94 MPa, 2345.35 MPa and 37.16 kJ/m2 respectively with less water absorption behavior. Whereas, the hybrid composite with kevlar as an outer layers and flax as core layers was exhibited a maximum flexural strength, modulus, and inter laminar shear strength of 360.76, 37124.2, and 213.51 MPa, respectively. The water absorption percentage was more in neat natural flax reinforced epoxy composite due to its more hydrophilic nature. The scanning electron microscope analysis reveals the proper bonding and adhesion of both kevlar and flax fabrics with the epoxy matrix. [ABSTRACT FROM AUTHOR]

Despite their scarce resistance to humid or wet conditions, natural fiber reinforced composites (NFRCs) seem to be able to partially recover their performances under discontinuous exposition to marine environment. To investigate this peculiarity, flax fiber reinforced composite was at first subjected to salt-fog spray condition at 35 °C for 15 and 30 days, respectively, and then stored in "dry" condition (i.e., 50% R.H. and 22 °C) between 0 and 21 days. The performances evolution was evaluated through flexural tests, water uptake and contact angle measurements. Moreover, the morphology of fractured mechanical samples was examined by using 3D optical microscope and scanning electron microscope (SEM). Flax fiber reinforced composite experienced phenomena of both reversible and irreversible degradation during the wet phase thus evidencing a relevant mechanical recovery thanks to the drying. Quite interestingly, the laminate showed an almost complete recovery of the flexural strength, meaning that this property is more strictly related to mainly reversible aging phenomena whereas the greater stiffness loss is more probably due to irreversible ones. • Natural Fiber Reinforced Composites were aged under alternated salt-fog and dry steps. • Flexural tests, water uptake and water contact angle measurements were performed. • NFRCs experienced reversible and irreversible degradative phenomena. • Due to the drying, NFRCs showed an almost complete recovery of flexural strength. • A topological map discriminating reversible and irreversible aging zones was created. [ABSTRACT FROM AUTHOR]