Investigations on coir fibre inhomogeneity and property variations for biocomposite applications

Agricultural waste-based lignocellulosic natural fillers and fibres are alternatives to synthetic fibres for developing sustainable composite products. The heterogeneity in the structure of the natural fibre affects its properties. The inconsistent performance and qualities of components made with natural fibres pose a significant challenge, limiting their use in engineering applications. By understanding the property variations within a single fibre, designers can select appropriate short fibres for the desired property. The current work aims to understand a fibre's heterogeneities and how they affect its mechanical characteristics. Coir fibre is categorised into three regions to address the property variation, from the root to the tail region. The morphological variations, chemical composition, and tensile behaviour of chopped fibres from each region were studied. The fibre diameter and internal porosity vary along the length of the fibre. The tail region's intact internal structure and lower porosity make it stronger than the other two regions. However, the modulus of the fibres extracted from the tail region is low. The fracture surface reveals the delamination of the cell walls and cellulose microfibril pull-out. The study highlights the need for fibre segregation based on the growth direction in composite part development.