Optimization of the damping properties of fibrous composites with viscoelastic coating

In this work we investigate the damping properties of fibrous composites with viscoelastic coating. It is shown that such materials have the effect of increasing the dissipative characteristics for the specific thickness of the viscoelastic coating on the fibers in a sufficiently narrow range of thicknesses value. The observed effect leads, in fact, an additional peak of the effective loss modulus fiber composite, which is implemented in the case of a fairly narrow range of variation of the thickness of the viscous coating when the dynamic elastic modulus (i.e., stiffness of the composite) is large enough. This increase in the effective loss modulus composite for the optimal values ​​of the thickness of the additional viscoelastic layer is so significant that one can speak of a synergistic effect for the effective loss modulus which is greatly exceeds the loss modulus of the viscous coating. We study the dependence of the effective viscoelastic properties of layered composites on the physical parameters of the composites structure (the thickness of the viscous coating on the fibers, fibers volume fraction). As an example, it is investigate in-plane isotropic laminate composite based on epoxy matrix with glass fibers coated with polyurethane. For theoretical calculations involved the classic model of the mechanics of composite materials and the method of complex modules. To determine the effective characteristics of the monolayer of fiber composite we consider two formulations of problems - in the plane of isotropy in the plane perpendicular to it. Effective bulk modulus and shear modulus in the transverse plane are defined, respectively, by the method of Eshelby solutions for the full tension (compression) across the fiber and pure shear in the transverse plane. Shear modulus of the composite is determined by the Eshelby method for the pure shear along the fiber in a cylindrical coordinate system. Effective Young's modulus and Poisson's ratio in the direction of the fibers are determined jointly by solving the problem of uniaxial tension in a cylindrical coordinate system.