Micromechanical analysis of viscoelastic damping in woven fabric-reinforced polymer matrix composites

This paper describes the development of a closed-form model and a finite element model for studying viscoelastic damping in woven fabric-reinforced polymer matrix composites, with emphasis on predicting viscoelastic damping loss factors of a plain weave E-glass fabric-reinforced vinyl ester resin matrix composite.;The development of the closed-form model consists of two steps. The first step is to derive the elastic solution based on the mechanics of materials theory. The second step is to apply the Elastic-Viscoelastic Correspondence Principle to the elastic solution, so that the effective complex moduli of the composite can be determined by the complex moduli of the constituent materials and fiber volume fractions. The damping loss factor is defined as the ratio of storage modulus to loss modulus in the complex modulus notation.;A three-dimensional finite element model is constructed based on the geometry of a plain weave fabric-reinforced composite unit cell. The finite element analysis is carried out with various load cases simulating extensional, shear and bending deformations. The strain energies stored in the fiber and matrix elements for each load case can be conveniently determined by the finite element analysis. A strain energy formulation which relates the total damping in the structure to the damping of each element and the reaction of the total strain energy stored in that element is used to calculate the damping loss factors of the composite.;Microscopic analysis is performed to determine the actual geometry of the composite unit cell which is used in the development of both analytical models. Experiments are conducted using an impulse-frequency response technique to measure damping in beam samples made of plain weave E-glass fabric-reinforced vinyl ester resin matrix composite. The predictions from both analytical models show reasonably good agreement with test data. The validated analytical models are then used to further investigate the effects of fiber volume fraction and fiber undulation length in order to improve and optimize damping in composite structures.