Mechanical properties and modeling of licorice root fiber-reinforced eco-friendly polymer composites

Licorice root fibers are promising natural reinforcements for polymer composites due to their favorable mechanical properties, rapid growth, and environmental sustainability. This study investigates the influence of fiber morphology and dispersion on the mechanical performance of epoxy-based laminated composites reinforced with licorice root fibers. Two fiber configurations, including bundles and milled fibers sieved to mesh sizes 20, 40, 60, and 80, are evaluated. Composites are fabricated using LY5052 epoxy resin and HY5052 hardener, and tensile properties are measured according to ASTM D3039. Analytical predictions are conducted using Halpin-Tsai and Mori-Tanaka models to assess uniform and clustered fiber distributions. Results show that elastic modulus decreases with decreasing fiber size (bundled fibers > mesh 20 > mesh 40 > mesh 60 > mesh 80), reflecting the importance of fiber aspect ratio and load-transfer efficiency. In contrast, toughness and strain energy increase with finer powders, indicating enhanced energy absorption and fracture resistance. These findings demonstrate that fiber morphology, fineness, and dispersion critically govern stiffness, toughness, and ductility in licorice root fiber composites, providing mechanistic insights and practical guidance for the design and optimization of sustainable biocomposites.