Damping composite materials by machine augmentation

The energy dissipation performance of machine augmented composite materials is investigated. Machine augmented composites are simple machines in a matrix. Fluid-filled tubes are used as machines; the tube cross-sectional geometry induces fluid flow when deformed. This flow dissipates mechanical energy and provides the composite material with attractive damping properties. Time accurate, three-dimensional finite element models are used to predict the performance of these damping materials with zero pressure at the ends of the tubes. Particular attention is given to dimensionless parameters that govern the energy dissipation efficiency of a machine-augmented lamina. An important dimensionless parameter is the ratio of solid elastic moduli to the product of the driving frequency and the fluid dynamic viscosity. For the geometry, the material properties, and the loading type considered the highest single-cycle efficiency predicted by these models is approximately 0.8 out of a maximum of 1.0.