Performance of nanoclay infused plant fibre-reinforced hybrid biocomposites under impact loading
Authors:   , Moyo Mufaro 
Published: July 2023

This study focused on developing sustainable and lightweight plant fibre-reinforced hybrid bionanocomposites with enhanced impact properties. Such biocomposites are envisaged as potential replacements for the non-sustainable conventional synthetic fibre-reinforced polymer composites in applications requiring resistance to impact loading. In this work, the hybrid bionanocomposites were fabricated using polylactic acid (PLA) as the biopolymer, kenaf fibre nonwoven mat as the biofibre and clay nanoparticles of different loadings as fillers. Clay nanoparticle loading of 0, 3, 5, and 7 wt% were used. The resultant kenaf/nanoclay/PLA hybrid bionanocomposites were tested for thermal decomposition, tensile properties, flexural properties, dynamic mechanical properties and impact properties. The medium velocity impact resistance was tested using a high speed gas gun. The structure-property relationships were characterised using a scanning electron microscopy (SEM), energy dispersive x-ray (EDX), fourier transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD) techniques. The resultant kenaf/nanoclay/PLA hybrid bionanocomposites were found to be considerably lightweight with a positive buoyancy. Clay nanoparticle loading of 5 wt% was found to be the optimum. The results showed that the thermal stability and dynamic mechanical properties of the hybrid bionanocomposites improved with the addition of clay nanoparticles. The tensile strength and the flexural strength of the hybrid bionanocomposites improved by 19.1% and 9.8%, respectively, when clay nanoparticles were added. Infusion with clay nanoparticles improved the Young’s modulus and flexural modulus by 41.5% and 34%, respectively. Addition of clay nanoparticles improved the energy absorption capability and impact strength of the hybrid bionanocomposites under low velocity impact loading by 92.9% and 98.7%, respectively. The clay nanoparticles also considerably enhanced the medium velocity impact resistance of the hybrid bionanocomposites as evidenced by improvement of the perforation threshold limit, energy absorption capability and damage resistance. The perforation threshold limit improved to 37 m/s which was equivalent to 42.3% increase, the energy absorption capability improved by 109% and the resistance to damage improved by 26.5%. The dominating damage mechanisms for the kenaf/nanoclay/PLA hybrid bionanocomposites were observed to be shear, matrix cracking, matrix crushing, fibre fracture, fibre/matrix debonding, shear plugging, bulging, interface debonding and delamination. Since the resistance to impact loading was established to be in the medium velocity impact range, the novel hybrid bionanocomposites have a potential to replace the non-biodegradable synthetic fibre-reinforced polymer composites in cushioning against secondary debris or blasts in the medium velocity impact range. They are also suitable for lightweight applications such as in the transportation sector for lightweight mass transit systems and unmanned aerial vehicles (UAV). The novel biodegradable kenaf/nanoclay/PLA hybrid bionanocomposite materials developed in this work are potential materials for the future which can positively contribute to sustainability and attainment of Sustainable Development Goals (SDG’s).