Tensile and flexural properties of polylactic acid-based hybrid green composites reinforced by kenaf, bamboo and coir fibers

Bio-based hybrid green composites in unidirectional configuration were prepared by using kenaf, bamboo and coir fibers to reinforce polylactic acid (PLA) polymer matrix. Three types of hybrid green composites: kenaf-coir/PLA, bamboo-coir/PLA and kenaf-bamboo-coir/PLA composites were investigated by tensile and flexural tests. Scanning electron microscopy and optical microscopy were used to observe their microstructural failures. Tensile strength of kenaf-bamboo-coir/PLA composites achieved 187 MPa, approximately 20 and 78% higher than bamboo-coir/PLA and kenaf-coir/PLA, respectively. Young's moduli of the three composites were low, ranging from 6.0 to 7.5 GPa. High flexural strength was obtained in both kenaf-bamboo-coir/PLA (199 MPa) and bamboo-coir/PLA (206 MPa) composites, approximately 16 and 20% higher than that of kenaf-coir/PLA, respectively. However, kenaf-coir/PLA composites showed the highest flexural modulus, approximately 70% higher than other combinations. Higher strain energy per unit volume required to break (toughness) was characteristic of kenaf-bamboo-coir/PLA composites. It was found that the combination of high strength and stiffness of bamboo and kenaf fibers and high ductility of coir fiber improved tensile and flexural strengths compared to those of single fiber green composites.