Green vibrations: dynamic stiffness and constitutive modelling of recycled nonwoven materials for sustainable vibration damping in flooring

The increasing concern over environmental sustainability has driven the exploration of waste-based materials as innovative engineering applications. Dynamic compressive mechanical tests were performed at varying frequencies to evaluate energy dissipation and stiffness. The results show that compressed samples exhibit higher Young's modulus, tensile strength, and dynamic stiffness compared to their uncompressed counterparts, particularly at higher frequencies. However, these compressed structures also display greater heterogeneity due to uneven fiber distribution and bonding during the compression process. Uncompressed structures, while more flexible and capable of larger deformations, dissipate energy more effectively at lower frequencies due to their looser fiber arrangement. Furthermore, the presence of small fiber black polyester and footwear waste in the samples negatively impacts mechanical performance in uncompressed structures, with shorter fibers hindering effective entanglement in the matrix. Compressed samples with low amounts of black polyester show improved homogeneity and mechanical properties. Overall, the study demonstrates that compression significantly enhances stiffness and energy dissipation at higher frequencies, while fiber composition and distribution play critical roles in determining the mechanical performance of these materials. A constitutive model based on the Kelvin-Voigt viscoelastic model was proposed to capture the complex mechanical behavior of the nonwoven and compressed nonwoven structures under dynamic loading, accounting for the elastic and viscous properties of the materials. By incorporating this model, we can facilitate further numerical studies that simulate real-world conditions, analyze stress distribution, and predict material performance under varying frequencies and loads.