Mechanical property characterisation of napier grass fibre reinforced polyester composites

The mechanical properties of Napier grass fibre-reinforced composites were characterised. Napier grass fibres were extracted through water retting process. The effect of alkali-treatment on the tensile properties and morphology of the fibres was investigated. The fibres were alkali-treated using NaOH solutions of 5, 10, 15 and 20% concentrations which subjected to single fibre testing. The morphology of the fibres was observed using scanning electron microscopy (SEM). The 10% alkali-treated Napier grass fibres yielded the highest strength. To fabricate the composites, Napier grass fibre and polyester resin were used as the reinforcing material and polymer matrix, respectively. The tensile and flexural properties of the composites were studied. In general, up to a certain threshold value, the tensile and flexural strengths of the composites increased as the fibre volume fractions increased, following which, there was a reduction in strength. The maximum tensile and flexural strengths of the composites were obtained at 25% fibre loading. Water absorption test were conducted by immersing samples in distilled water bath at room temperature (25°C) at different time durations. The wet and dry specimens of composites were subjected to tensile, flexural and scanning electron microscopy (SEM) tests according to ASTM standard respectively. The water absorption pattern of Napier grass fibre composites obeys Fickian behavior at room temperature immersions. The percentage of water absorption is higher for untreated fibres samples rather than treated due to removal of both lignin and hemicelluloses on the fibre surfaces. Tensile and flexural properties of Napier grass composites decreased with increase in percentage of water absorption. Effects of elevated temperature were studied temperature set at room temperature, 45°C, 65°C and 75°C. Higher temperature induces physical and chemical changes in the composites the mechanical properties which are also governed by the unsaturated polyester. However, a significant decrease in tensile and flexural properties was observed for the entire composite tested at elevated temperature. Generally, this study is useful to predict the suitability of using the novel Napier grass fibre as reinforcement in polymer resins.