Damping in partially delaminated composites

Abstract

A simple model was developed to predict the material damping in partially delaminated composites. First, we evaluated the damping loss factors experimentally in three kinds of specimens corresponding to various partial delamination areas. Second, the stiffness loss with delamination growth was assumed to result directly in the loss of energy from the oscillatory system because the delamination due to interlaminar stress is accompanied with stiffness loss in numerous laminated composites. By correlating the laminate stiffness reduction and the corresponding delamination area, a model for their basic material damping properties was formulated using the elastic-viscoelastic principle, the rule-of-mixtures law and modified Hashin’s Model. We predicted the damping of any partially delaminated composites with different stacking sequences based on Adams and Ni’s work and their basic damping loss factors. Numerical and experimental results demonstrate that damping is significantly influenced by the size of delamination area in laminated composites. In addition, experimental improvements in making accurate damping measurements are discussed as well.