Machine augmented composite materials for damping purposes
(MAC) materials is investigated. MAC materials are formed by inserting simple
machines into a matrix material. In this work the machines take the form of fluid filled
tubes, and the tube cross-sectional geometry induces fluid flow when it is deformed in its
plane. This flow dissipates mechanical energy, and thus provides the composite material
with attractive damping properties. The objective of this study is to gain insight into the
geometry, the material property combinations, and the boundary conditions that are
effective in producing high damping MAC materials. Particular attention is given to
tube geometry and to dimensionless parameters that govern the energy dissipation
efficiency of a MAC lamina. An important dimensionless parameter is the ratio of solid
elastic 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 forces
in the fluid material that makes up a MAC lamina. Governing equations and simulation
methods are discussed. Simplified equations are derived to predict the pressure
generated when a tube/matrix cell is squeezed with zero pressure end conditions.
Transient, three dimensional finite element models are also used to predict the
performance of the damping MAC materials with zero pressure at the ends of the tubes.
For the geometry and material properties considered, the highest energy dissipation
efficiency predicted by these models is approximately 0.8 out of a maximum of 1.0.
Advisor:Reddy, J. N.; Creasy, Terry; Perry, William
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:machine augmented composites damping
Date of Publication:12/01/2004