Physical, Mechanical, and Thermal Characterization of a Cocos Nucifera Rachis Reinforced Polyester Matrix Composite

The valorisation of natural waste proves highly promising given its abundance in our environment. In this context, we developed a polyester matrix composite reinforced with treated fibres extracted from the coconut rachis (Cocos nucifera). Prior to incorporation, the fibres were subjected to an alkaline treatment and then added at different volume fractions (10%, 15%, 20%, 25%, and 30%) into the matrix using a manual hand lay-up technique. After fabrication of the composite material, the physical, mechanical, and thermal properties of each specimen were evaluated. Regarding the physical properties, the results indicate an increase in composite porosity, ranging from 6.877% to 13.437% depending on the fibre content. The water absorption rate shows a slight, monotonic rise, averaging 0.49%. Concerning the mechanical properties, the composite containing 25% fibres exhibits the best tensile and flexural strengths, with values of 19.450 MPa and 28.718 MPa, respectively. Thermal assessment using an asymmetric hot plate device reveals that fibre incorporation enhances the thermal insulation of the material. Furthermore, X-ray diffraction (XRD) analysis highlights a predominantly amorphous structure at 0% fibre content, with characteristic peaks of polyester. From 15% onwards, crystallinity peaks associated with cellulose and minerals begin to appear. At 25% and 30%, crystallinity becomes more pronounced, reflecting improved structuring of the fibrous phases and stronger interaction with the matrix. These observations are consistent with the literature on natural fibre composites.