Natural fiber

Composite number

Epoxy

Materials science

Ultimate tensile strength

Thermal conductivity

Viscoelasticity

Polymer

Dynamic mechanical analysis

Glass fiber

Composite material

Absorption of water

Scanning electron microscope

Flexural strength

Polymer Composites

The recent development of natural fiber‐reinforced polymer composites have shown innumerable economic and environmental benefits for a vast array of engineering applications. It is quintessential to investigate the effect of water absorption on the composites that remain in the water for a maximum of their intended service period. This study is an effort in this direction that investigates the effect of water absorption on thermo‐mechanical properties of flax‐hemp‐reinforced epoxy composites fabricated using compression hand layup technique with different weight fraction of fiber. The fabricated composites have been characterized physically (density and water absorption), thermo‐mechanically (tensile, flexural, thermal conductivity, and dynamical mechanical analysis), and morphologically (scanning electron microscopy [SEM]). The analysis revealed that hemp‐reinforced composites (S1) had the highest water absorption capabilities in comparison to the flax‐reinforced composites (S5). Higher water absorption capability had an adverse effect on the mechanical properties of fabricated composites. However, hybrid composites (S2, S3, and S4) reported better performance with regard to S1. The increased water content, however, increased the thermal conductivity of composites and maximum has been revealed for S1 (0.82 W/mK) and minimum for S5 (0.48 W/mK). The water molecules showed detrimental effects on the viscoelastic properties and revealed S3 have better interlocking bond with the lowest reduction in storage modulus (12%) and glass transition temperature (4°C) in comparison to S1 (30%) under wet conditions. A comparative analysis of the thermo‐mechanical properties was also made for developed composites under dry, saturated, and re‐dried conditions. The SEM has been used to characterize the morphological and fracture behavior of the fabricated composites under the influence of water uptake. The effects of water molecules on the hygrothermal aging index and diffusion co‐efficient have also been discussed. Overall, the hybridization of flax with hemp fiber showed better results over the hemp fiber‐reinforced composites (S1).

Investigation of the effect of water absorption on thermomechanical and viscoelastic properties of flax‐hemp‐reinforced hybrid composite