Development of commercial fully bio-based sport utility using jute/hemp bio-epoxy composite: Influence of stacking sequence on the fatigue, thermo-mechanical, vibrational and viscoelastic behavior

Eco-friendly composites are a key research focus due to environmental concerns, with natural fibers being explored as replacements for synthetic materials. This study aimed to develop and evaluate composites using commercially available jute and hemp fibers with a bio-epoxy matrix. Although there are various studies that report the mechanical properties of jute-hemp composites, no work has analyzed the complex dynamic mechanical, thermo-mechanical, fatigue, and vibrational properties of these bio-based jute-hemp bioepoxy composites. In this study, composites were developed using commercially available jute and hemp fibers, with bio-epoxy (SR-56) as the matrix to enhance eco-friendliness. Thermomechanical analysis revealed that the hemp-based composite had the lowest thermal expansion (0.12%) in the glass transition region. Dynamic mechanical analysis, performed under dual and single cantilever modes, showed that the jute-based composite exhibited the highest Tan δ value. The composite with hemp as the skin and jute as the core demonstrated intermediate values, with controlled Tan δ and complex modulus (E*). The E* of the HJH composite was 3.5 GPa in dual cantilever mode and 2.1 GPa in single cantilever mode due to localized stress concentration. Fatigue analysis showed an increase in stiffness from 30.04 N/mm at 40,000 cycles to 31.61 N/mm at 60,000 cycles before microcracks appeared at 90,000 cycles. Free vibration analysis indicated that composites reinforced with lower stiffness fibers had higher damping across all modes, with the JJJ composite exhibiting the highest damping ratios in mode-1 (0.56161), mode-2 (0.1664), and mode-3 (0.074891). These results demonstrate the potential of jute-hemp bio-epoxy composites for lightweight structural applications, demonstrated by the development of a bicycle mudguard using the optimal stacking sequence.