Modal analysis and design optimization of natural fibre-based sandwich structures for enhanced damping and stiffness

This study presents a comprehensive investigation into the free vibration behaviour and optimization of natural fibre-based laminated sandwich (NFLS) structures, with a focus on enhancing both damping capacity and structural stiffness. The NFLS beam consists of two isotropic elastic face sheets and a viscoelastic core reinforced with Jute-Polyurethane, a sustainable material offering favourable energy dissipation characteristics. Experimental modal analysis is conducted using the impact hammer technique to find the natural frequencies and modal loss factors. A detailed finite element model is developed incorporating shear and compressive damping effects, with the governing equations formulated through Hamilton's principle. Numerical results shows that a strong agreement with experimental results, validating the accuracy and robustness of the proposed model. A parametric study is carried out to find out the effect of core thickness, skin thickness and core loss factor on the dynamic responses of the NFLS beam. Also, the Taguchi optimization method is used to identify the optimal configuration for maximizing the signal-to-noise (S/N) ratio. This analysis shows that a core thickness of 10 mm, a skin thickness of 2.5 mm, and a core loss factor of 0.8 gives the best combination for superior dynamic performance.