Effects of water absorption on the mechanical and morphological properties of date palm leaf fiber-reinforced polymer composites

The growing demand for sustainable and biodegradable materials has led to increasing interest in using natural fibers as reinforcements in polymer composites. Among these, date palm leaf fibers (DPLFs), an abundant agricultural byproduct in the Middle East, show promise due to their favorable mechanical characteristics. This study investigates the effects of water absorption on the mechanical and morphological properties of DPLF-reinforced polymer (DPLFRP) composites to assess their viability in moisture-prone environments. Five types of DPLFs (Nabtat-seyf, Sultana, Barhee, Sukkary, and Khalasah) were extracted, characterized morphologically using scanning electron microscopy (SEM), and fabricated into unidirectional epoxy-based laminates via hand layup. Mechanical performance was assessed through tensile testing before and after 48 hrs of water immersion. Morphological changes and water uptake behavior were also examined. The results show that Nabtat-seyf exhibited the highest tensile strength (100.58 ± 7.95 MPa) and modulus (6.16 ± 0.85 GPa) among the DPLFs. Water absorption led to a reduction in tensile strength and modulus of DPLFRP composites by 39–47% and 21–32%, respectively. SEM analysis revealed microstructural damage mechanisms such as fiber–matrix debonding, fiber swelling, and matrix cracking. The specific tensile modulus and strength also declined significantly with increased moisture content. These findings suggest that while DPLFs, especially Nabtat-seyf, have high potential as reinforcement in biocomposites, water absorption presents a major challenge. Applications include automotive interior components, construction panels, and low-load structural elements, provided moisture barriers or fiber treatments are applied for durability enhancement.