In this study the energy dissipation performance of machine augmented composite(MAC) materials is investigated. MAC materials are formed by inserting simplemachines into a matrix material. In this work the machines take the form of fluid filledtubes, and the tube cross-sectional geometry induces fluid flow when it is deformed in itsplane. This flow dissipates mechanical energy, and thus provides the composite materialwith attractive damping properties. The objective of this study is to gain insight into thegeometry, the material property combinations, and the boundary conditions that areeffective in producing high damping MAC materials. Particular attention is given totube geometry and to dimensionless parameters that govern the energy dissipationefficiency of a MAC lamina. An important dimensionless parameter is the ratio of solidelastic moduli to the product of the driving frequency and the fluid dynamic viscosity.This is a measure of the ratio of elastic forces in the solid material to the viscous forcesin the fluid material that makes up a MAC lamina. Governing equations and simulationmethods are discussed. Simplified equations are derived to predict the pressuregenerated when a tube/matrix cell is squeezed with zero pressure end conditions.Transient, three dimensional finite element models are also used to predict theperformance of the damping MAC materials with zero pressure at the ends of the tubes.For the geometry and material properties considered, the highest energy dissipationefficiency predicted by these models is approximately 0.8 out of a maximum of 1.0.
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