This dissertation studies by experiment and numerical analysis an advanced composite material (Machine Augmented Composite or MAC) for enhancement of the passive damping while maintaining its stiffness. This MAC is composed of a pre-buckled wall structure placed within a viscoelastic matrix. The pre-buckled machine can contain viscous fluids for additional energy dissipation. For the experiments, the MAC was fabricated by using rigid and soft polyurethane as a machine and matrix material respectively. Various viscosity fluids (0.83 ~ 4730 cps) filled the inner-channel of the machine structure. Dynamic properties such as tan ?? and the loss modulus (E") of the composite were measured and compared with those of a homogeneous matrix sample over a frequency range of 0.1 to 100 Hz at room temperature through load-controlled cyclic testing. Measured tan ?? and loss modulus values for the composite were higher than those of the matrix alone in the 1 to 40 Hz range. However the viscous fluid effects on the overall damping properties were small. The performance of a theoretical MAC was explored through numerical analysis. The amount of inner-channel gap closure was calculated for various matrix Poisson??s ratios, for various Young??s modulus ratios between the machine and matrix (Emachine/Ematrix), and for the volume fraction of the machines. The most desirable performance of the composite was obtained when the matrix Poisson??s ratio was 0.49, and there was interaction between the Emachine/Ematrix and the volume fraction of the machines. Also the proper volume fraction range of the machine was predicted to be between 0.15 and 0.2 for the lamina shape MAC. Based upon the analysis, a sandwich structure MAC was fabricated and tested. This composite showed 11 times higher stiffness than the matrix without loosing the matrix damping property. This dissertation shows that the research met these objectives: 1) the MAC concept is effective for passive damping of vibrations, 2) that material combinations studied here had optimal combinations for best performance, and 3) that this is a promising field study for future passive and active materials development.

This dissertation studies by experiment and numerical analysis an advanced composite material (Machine Augmented Composite or MAC) for enhancement of the passive damping while maintaining its stiffness. This MAC is composed of a pre-buckled wall structure placed within a viscoelastic matrix. The pre-buckled machine can contain viscous fluids for additional energy dissipation. For the experiments, the MAC was fabricated by using rigid and soft polyurethane as a machine and matrix material respectively. Various viscosity fluids (0.83 ~ 4730 cps) filled the inner-channel of the machine structure. Dynamic properties such as tan ?? and the loss modulus (E") of the composite were measured and compared with those of a homogeneous matrix sample over a frequency range of 0.1 to 100 Hz at room temperature through load-controlled cyclic testing. Measured tan ?? and loss modulus values for the composite were higher than those of the matrix alone in the 1 to 40 Hz range. However the viscous fluid effects on the overall damping properties were small. The performance of a theoretical MAC was explored through numerical analysis. The amount of inner-channel gap closure was calculated for various matrix Poisson??s ratios, for various Young??s modulus ratios between the machine and matrix (Emachine/Ematrix), and for the volume fraction of the machines. The most desirable performance of the composite was obtained when the matrix Poisson??s ratio was 0.49, and there was interaction between the Emachine/Ematrix and the volume fraction of the machines. Also the proper volume fraction range of the machine was predicted to be between 0.15 and 0.2 for the lamina shape MAC. Based upon the analysis, a sandwich structure MAC was fabricated and tested. This composite showed 11 times higher stiffness than the matrix without loosing the matrix damping property. This dissertation shows that the research met these objectives: 1) the MAC concept is effective for passive damping of vibrations, 2) that material combinations studied here had optimal combinations for best performance, and 3) that this is a promising field study for future passive and active materials development.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Politics, 1999. / Bibliography: leaves 311-340.

Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1993. / Includes bibliographical references (p. 86-93).

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Generally, to meet the Telemetry and Tracking functions in space probes, RF packages are realised using dedicated circuit configurations and different building blocks. While this approach is warranted for certain Space missions, for some Space programmes, which are basically Technology demonstrators and where the main emphasis is on higher flexibility with minimal complexity - usage of multifunction RF modules (MFRM), would be highly avantageous. The MFRM, which can be considered as a RF package, has a flexible configuration and is built around Common basic building blocks like broadband MMIC, wide band amplifiers, switches, Dielectric Resonant Oscillators (DRO), Numerically Controlled Oscillators (NCO), etc. It also has a Microcontroller, whose function is to select the required configuration and make necessary interconnections between the building blocks, so as to achieve a specific end function, based on the pre set commands from system designer. The commands can either be preprogrammed or they can be through uplink Telecommand signals from the ground stations. A brief outline of the results of the proto unit of a MFRM which can be configured for different end RF functions, through a microcontroller is presented in the paper. It is expected that in Space missions like LEO programmes, Microsats, Reentry, Microgravity experiments etc, the MFRM approach would offer greater flexibility to the system designer at reduced-cost, complexity and production turn around time.

Bibliography: leaves 311-340. / iv, 340 leaves ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the Multifunction Polis concept, its possibilities and its failure. / Thesis (Ph.D.)--University of Adelaide, Dept. of Politics, 1999

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