Dynamic free vibration response of thermoplastic polyurethane–aluminum powder composites

Advanced thermoset composite materials are widely used due to their high specific strength, corrosion resistance, good fatigue life, light-weight nature, and design flexibility; however, they exhibit limitations such as poor recyclability, weak out-of-plane strength, and low damping capacity. Since mechanical vibrations lead to energy loss, fatigue failure, and noise, materials with enhanced damping properties are required for vibration control applications. In this study, pure thermoplastic polyurethane (TPU) and aluminum powder-filled TPU composites (1,2,5, and 10 wt%) were fabricated using injection molding for tensile and free vibration analysis. The first three natural frequencies were evaluated theoretically using Euler-Bernoulli beam theory, numerically via ANSYS following ASTM E756 standards, and experimentally through impact hammer testing using an ACC 103 accelerometer sensor. Mechanical properties were determined using tensile testing, while dynamic responses were analyzed in terms of natural frequencies and damping ratios. The results indicate that natural frequencies are directly dependent on elastic modulus, while the aluminum filler in the corporation reduces natural frequencies and significantly improves damping performance. SEM analysis revealed that filler dispersion, agglomeration, and interfacial adhesion strongly affect both mechanical and dynamic properties. The maximum damping ratio of 2.44 was achieved for 10 wt% aluminum-filled TPU with 65% improvement compared to pure TPU, demonstrating its potential for applications such as sandwich composite cores, vibration isolation systems, and structures requiring effective vibration suppression.