Temperature and loading rate effects on tensile properties of kenaf bast fiber bundles and composites

This paper presents extensive experiments and micromechanics-based modeling to evaluate systematically the tensile properties of kenaf bast fibers bundle (KBFB) and kenaf bast fiber-reinforced epoxy strands. Uniaxial tension behaviors of KBFBs and KBFB-reinforced epoxy strands were evaluated statistically using large sample sets. The elastic modulus, tensile strength, as well as failure strains of KBFBs, displayed large scatter statistically ranging from 10% to 30%. The loading rate-dependency was evaluated at three strain rates ranging from approximately 10−4 ∼ 10−2/s. The tensile strength increases gradually as the loading rate increases, while the tensile modulus almost remains the same as the loading rate increases until the loading rate reaches 10−2/s, at which a much higher modulus was presented. The high temperatures (170–180 °C), possibly subjected during fiber processing and composite fabrication, do not impose significant effects on the tensile properties of KBFBs if the duration is less than 1-h. The tensile properties of KBFB were not affected by the conditioning at 130 °C for 24-h, which mimics the severe service temperature of automotive front-end components. KBFB-epoxy composite strands were further evaluated at various loading rates. A micromechanics-based Mori–Tanaka model was implemented to predict the anisotropic elastic moduli of KBFB and KBFB-epoxy composite strands based on the microstructural compositions.