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Robert G. Bryant

Bio: Robert G. Bryant is an academic researcher from Langley Research Center. The author has contributed to research in topics: Solar sail & Piezoelectricity. The author has an hindex of 22, co-authored 85 publications receiving 2058 citations. Previous affiliations of Robert G. Bryant include Government of the United States of America.


Papers
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Proceedings ArticleDOI
12 Jun 2000
TL;DR: In this article, a planar composite piezoceramic actuator is presented, which uses interdigitated electrodes for poling and subsequent actuation of an internal layer of machined piezoelectric fibers.
Abstract: The design, manufacture, and testing of a low-cost, flexible, planar composite piezoceramic actuator device will be presented. The actuator uses interdigitated electrodes for poling and subsequent actuation of an internal layer of machined piezoceramic fibers. The fiber sheets are formed from monolithic piezoceramic wafers and conventional computer controlled wafer-dicing methods. The fabrication and use of fiber sheets allows precise handing and alignment of piezoceramic fibers during subsequent phases of actuator assembly. Test show that the actuator is capable of producing large, directional in-plane strains; on order of 2000 parts-per-million under a 4000 V peak-to-peak applied voltage cycle. Preliminary endurance testing indicates that the device is relatively durable, with no reductions in free-strain performance up to 90 million electrical cycles.

561 citations

Patent
24 Jan 1997
TL;DR: A method for forming ferroelectric wafers is provided in this article, where a prestress layer is placed on the desired mold and a ferro-electric wafer is placed over this layer, and the layers are heated and then cooled, causing the wafer to become prestressed.
Abstract: A method for forming ferroelectric wafers is provided A prestress layer is placed on the desired mold A ferroelectric wafer is placed on top of the prestress layer The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer Wafers produced using this method have greatly improved output motion

213 citations

Journal ArticleDOI
TL;DR: In this paper, 13 different configurations of a new class of piezoelectric devices called THUNDER (thin layer composite unimorph ferroelectric driver and sensor) were tested at two stages of the manufacturing process: before and after repoling.

165 citations

Journal ArticleDOI
03 Nov 2015-ACS Nano
TL;DR: The experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites are demonstrated and the additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions.
Abstract: Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buck-paper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions. utilizing the unique characteristics of BNNTs.

105 citations

Proceedings ArticleDOI
09 Jul 2002
TL;DR: The NASA Morphing Project as discussed by the authors seeks to develop and assess advanced technologies and integrated component concepts to enable efficient, multi-point adaptability in air and space vehicles, including smart materials, adaptive structures, micro flow control, biomimetic concepts, optimization and controls.
Abstract: The NASA Morphing Project seeks to develop and assess advanced technologies and integrated component concepts to enable efficient, multi-point adaptability in air and space vehicles. In the context of the project, the word "morphing" is defined as "efficient, multi-point adaptability" and may include macro, micro, structural and/or fluidic approaches. The project includes research on smart materials, adaptive structures, micro flow control, biomimetic concepts, optimization and controls. This paper presents an updated overview of the content of the Morphing Project including highlights of recent research results.

100 citations


Cited by
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Journal Article
TL;DR: This book by a teacher of statistics (as well as a consultant for "experimenters") is a comprehensive study of the philosophical background for the statistical design of experiment.
Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

13,333 citations

Journal ArticleDOI
TL;DR: A comprehensive review of existing piezoelectric generators is presented in this paper, including impact coupled, resonant and human-based devices, including large scale discrete devices and wafer-scale integrated versions.
Abstract: This paper reviews the state-of-the art in vibration energy harvesting for wireless, self-powered microsystems. Vibration-powered generators are typically, although not exclusively, inertial spring and mass systems. The characteristic equations for inertial-based generators are presented, along with the specific damping equations that relate to the three main transduction mechanisms employed to extract energy from the system. These transduction mechanisms are: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ active materials that generate a charge when mechanically stressed. A comprehensive review of existing piezoelectric generators is presented, including impact coupled, resonant and human-based devices. Electromagnetic generators employ electromagnetic induction arising from the relative motion between a magnetic flux gradient and a conductor. Electromagnetic generators presented in the literature are reviewed including large scale discrete devices and wafer-scale integrated versions. Electrostatic generators utilize the relative movement between electrically isolated charged capacitor plates to generate energy. The work done against the electrostatic force between the plates provides the harvested energy. Electrostatic-based generators are reviewed under the classifications of in-plane overlap varying, in-plane gap closing and out-of-plane gap closing; the Coulomb force parametric generator and electret-based generators are also covered. The coupling factor of each transduction mechanism is discussed and all the devices presented in the literature are summarized in tables classified by transduction type; conclusions are drawn as to the suitability of the various techniques.

2,834 citations

Journal ArticleDOI
TL;DR: The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans as mentioned in this paper, and the use of batteries can be troublesome due to their limited lifespan, thus necessitating their periodic replacement.
Abstract: The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their limited lifespan, thus necessitating their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of a disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with piezoelectric materials. This article will review recent literature in the field of power harvesting and present the current state of power harvesting in its drive to create completely self-powered devices.

2,438 citations

Journal ArticleDOI
TL;DR: An overview of the progress in functionalized hexagonal boron nitride (h-BN) nanomaterials can be found in this paper, where different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc.
Abstract: Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields.

836 citations