MODELING FREQUENCY-DEPENDENT LONGITUDINAL DYNAMIC BEHAVIOR OF LINEAR VISCOELASTIC LONG-FIBER COMPOSITES

An approach to modeling the longitudinal dynamic behavior of unidirect ional long fiber composites made from constituents having frequency-de pendent material properties is described. In this approach, the total displacement field is considered to be comprised of two parts: an elas tic part, and an anelastic part. Material dynamic behavior is describe d by constitutive equations and governing differential equations. Thes e equations involve the coupled behavior of the total displacement fie ld and the anelastic displacement fields. An ''equation of motion'' de scribes the time evolution of the total displacement field, while ''re laxation equations'' describe the time evolution of the anelastic disp lacement fields. Distinct anelastic displacement fields are initially associated with the constituent fiber and matrix materials. Effective composite anelastic displacement fields and material properties are th en developed in terms of the corresponding constituent properties and their respective volume fractions. The determination of frequency-depe ndent composite modulus and damping properties from corresponding cons tituent properties is illustrated, using data from prior experiments. This approach to modeling composite longitudinal behavior suggests dir ection for the development of an approach to modeling more general beh avior, as well as an approach to the analysis of thermorheologically c omplex materials.