A new effective 3-D FE formulation of FRP structural modal damping for thick laminate

In order to calculate the contribution of out-of-plane stresses and strains to laminate structural modal damping in FEM with fewer elements in thickness direction, composite structural modal damping prediction theory based on 3-D effective damping matrix is presented in this paper. First, the composite structure is divided into several sublaminates along the thickness, and each sublaminate contains many laminas. These sublaminates’ stiffness matrices, compliance matrices and 3-D effective damping matrices are calculated by lamination theory. Then finite elements are generated with these sublaminates, and structural modal analysis is implemented. Combining the 3-D effective damping matrices and the results of modal analysis, specific damping capacities for each modal are calculated. The presented method is validated by the calculations for structural SDCs of unidirectional laminate, symmetrical laminate and thick laminate. This method combines the accuracy and efficiency with the consideration of out-of-plane stresses and strains contribution.