Identification of the damping properties of orthotropic composite materials using a mixed numerical experimental method

A mixed numerical experimental approach is the basis of a new method for the identification of the material damping properties of fibre reinforced polymers, which provides an answer to many problems encountered in experimental damping characterization. Experimental modal parameters, measured on a plate specimen, are compared with corresponding results from a numerical calculation, thus allowing to determine the stiffness and damping properties of the material. The relation between the modal parameters (structural parameters) and the material parameters, is obtained by using a numerical model of the specimen in combination with the modal strain energy method. In the first part of this paper, the complex moduli are introduced as measures for both material stiffness and damping and the relation between these complex moduli and the modal parameters of a thin plate specimen is derived. Next, the practical procedure of the mixed numerical experimental method is presented, followed by a procedure for estimating the reliability of the obtained results. Finally, two examples are discussed in which all the independent material damping properties are identified as functions of frequency.