Elastothermodynamic damping in laminated composites

When a composite material is subjected to a time-harmonic stress field (homogeneous or inhomogeneous), different phases undergo different temperature fluctuations due to the well-known thermoelastic effect. As a result irreversible heat conduction occurs within each phase and between phases, and entropy is produced. This entropy production is the genesis of elastothermodynamic damping, and manifests itself as a conversion of work into heat. This is one of a large number of sources of damping in a real composite. Mechanics-based analytical methods for predicting damping due to various relaxation mechanisms have not been reported. Therefore, it becomes difficult to divide the total (experimentally measured) damping into its various constituents. This defines the objective of the present work: we present a methodology for predicting the elastothermodynamic damping of an N-layer laminated composite. The stress field may be quite general so long as the resulting heat conduction occurs only in the direction orthogonal to the laminae. By way of illustration, numerical results are presented for a symmetric three-layer plate in biaxial bending. (C) 1997 Elsevier Science Ltd.