Characterization of mechanical, free vibration, and water absorption behavior of natural fiber–vinyl ester composites

In current research, compression molding was used to fabricate Phoenix sp. fiber reinforced vinyl ester composites. Fiber volume fraction (10, 20, 30 and 40 wt%) and fiber length (10, 20 and 30 mm) were varied in order to investigate the mechanical characteristics, free vibration, and water absorption behavior. Composites reinforced with 30 wt% of 20 mm fiber length exhibited optimal properties, including tensile strength (27.56 MPa), tensile modulus (1977.63 MPa), flexural strength (62.28 MPa), flexural modulus (2774.81 MPa), impact energy (0.494 J), hardness (79.33) and free vibration properties (30.42 Hz). Increasing the Phoenix sp. fiber content and length improved the stiffness and reduced mass in the composites, resulting in a higher natural frequency. In contrast, the moisture absorption rate exhibited a positive correlation with both fiber length and volume fraction when evaluated under ambient environmental conditions. Scanning electron microscopy reveals that composites with 20 mm fibers have a strong bonding with vinyl ester matrix. Based on obtained results, 20 mm fiber with 30 wt% reinforcement is the best choice for producing high-quality composites and is recommended for interior use in the automotive and packaging industries.