Mechanical properties of leaf sheath and trunk fiber of Cocos nucifera L. as dispersed materials for eco-friendly composite development

In recent years, composite materials have been recognized as promising materials for various industrial applications. Owing to their eco-friendly, recyclable, and low-energy production, natural fiber-reinforced composites are a potential alternative to synthetic fibers, which still dominate manufacturing. Here, our study aims to develop innovative, low-cost, and promising materials from Cocos nucifera L. fiber and to analyze their mechanical, structural, and chemical properties to meet the scientific community’s needs and enhance several sustainable applications. We conducted the fabrication process and compared composites with 45% volume fraction (Composite 1), 30% monolithic leaf sheath fibers (Composite 2), and 30% hybrid fibers combining 25% leaf sheath and 5% trunk fibers (Composite 3). The results show Composite 2 exhibited superior tensile (17.85 ± 0.36 MPa), flexural (41.93 ± 0.84 MPa), and moisture absorption capability (6.11 ± 0.12%) among the tested formulations. It was found that the suboptimal mechanical and favorable hygroscopic properties were due to the number of composite voids represented by a high-risk void (HRV) of 0.63%, as well as the presence of C = C, CH (sp 2 ), and aromatic ring functional groups, which indicate the presence of impurities such as lignin, and an amorphous index of 86.28% in Composite 2. In summary, our study demonstrates that Cocos nucifera L. fiber-based composites are suitable for semi-structural applications, and performance can be improved through optimized NaOH treatment.