Damping characterization of viscoelastic composites using micromechanical approach

When studying composite material systems, mechanical properties, such as stiffness, strength, fracture toughness or damage resistance are the subjects of greatest interest and in most of the cases are considered in the context of simple static loading conditions. However, in almost all applications, composites, like most materials are subjected to dynamic loading which requires that the dynamic response of the composite be analyzed. For structural materials which are linear elastic, the stress-strain response is not dependent on strain rate, and there is no hysteresis or damping. However, this is not the case for viscoelastic materials for which both the stiffness and loss properties directly depend on strain rate and implicitly depend on temperature via time temperature superposition, which in case of harmonic loading leads to frequency dependent response. For viscoelastic composites in which at least one of the constituent materials is viscoelastic, there is great utility in the ability to predict the effective dynamic mechanical properties as a function of the constituent phase properties and geometry. In this paper micromechanical methods combined with the correspondence principle of viscoelasticity are used to obtain the effective damping properties of viscoelastic composites. When materials with different damping properties are present in a composite, the damping properties of the resulting composite are different than that of the constituents. The correspondence principle helps to consider all the frequency dependent properties of the constituent materials and conclude the effective damping vs. frequency. In this study the matrix phase is considered to be viscoelastic and spherical elastic/viscoelastic particles are dispersed into the matrix.