Optimum microstructural design of coated sphere filled viscoelastic composites for structural noise and vibration damping applications

Abstract

An unstructured mesh Galerkin time domain finite element method is used to validate the effective viscoelastic stiffness predictions of the n-layered spherical inclusion model. We study composites consisting of a solid polymer matrix filled by core-shell inclusions made up of silica spheres coated with a viscoelastic polymer layer. Assuming temperature dependent properties of the coating layer, temperature runs are performed from below to above its glass transition region. The studied composites have a stiffness contrast from 30 to 3000 and coating layer thicknesses between 1 and 0.001 relative to the sphere radius. Periodic random Monte Carlo computer models with 27 non-overlapping identical core-shell spheres are employed in the finite element calculations. It is shown that the n-layered spherical inclusion model is remarkably accurate and suitable for quick and reliable microstructural design of viscoelastic composites with layered spherical inclusions. Damped natural vibrations of viscoelastic Bernoulli-Euler beams and Kirchhoff plates are considered and, using the viscoelastic corresponding principle, a refined figure of merit for selecting best performing materials for structural noise and vibration damping applications is derived. We perform optimum vibration damping time design and demonstrate that by optimizing the thickness and the properties of the coating layers, substantial improvements can be achieved in the vibration damping characteristics of viscoelastic beams and plates.