Identification of Viscoelastic Material Properties of a Layer Through a Constrained Sandwich Beam in the Frequency Domain

Constrained-layer damping treatment with viscoelastic material as a core is the most effective passive vibration control technique. Identifying the mechanical properties of viscoelastic materials can be difficult, as polymers combined with different reinforcements and fillers often show variable mechanical characteristics. The present research proposes an inverse identification method to characterize the frequency-dependent mechanical properties of a viscoelastic material utilizing the experimental modal analysis test results. For this purpose, a sandwich beam with a core layer of viscoelastic material constrained between two isotropic face layers is considered. Free vibration test utilizing the impact hammer technique is carried out on the sandwich beam with a core material of natural rubber. The proposed inverse method integrates the response surface method with a constrained optimization approach to identify natural rubber's frequency-dependent shear storage modulus and material loss factor. A fit for these frequency-dependent material parameters is executed to obtain the analytical expressions for a wide frequency range. The identified material parameters of natural rubber are then compared with those obtained from experimental dynamic mechanical analysis (DMA) tests to ensure the accuracy of the proposed inverse method. The results obtained from analytical solutions are in line with the experimental test results, confirming the efficacy of the present research approach. The proposed inverse methodology has the potential to significantly improve the testing and characterization of materials, leading to better design and optimization of materials and structures for specific applications.