Showing papers on "Smart material published in 1992"
TL;DR: In this article, a smart material made from a metallized ionomer membrane called Nafion has been developed to sense mechanical vibrations and generate a voltage response with a unique vibrational damping property.
Abstract: Vibration control has been achieved using state-of-the-art 'smart' materials. A 'smart' material has been developed from a metallized ionomer membrane called Nafion. This electroded material can sense mechanical vibrations and generate a voltage response. Electroded Nafion has a unique vibrational damping property. Damping with this material is achieved by dissipating the electrical energy generated as heat. This can be done using an external resistance or optimally by creating an internal conductive path. A prototype accelerometer cell has been developed which shows excellent linear characteristics and high sensitivity. It is found that the most critical element in both of the applications is the sum of the internal and the contact resistances of the electroded Nafion hydrogen pressure cell. Accordingly, a study of the resistance of these Nafion-based cells has been made and the results are included and discussed.
281 citations
TL;DR: In this paper, the authors report on the development of a wavelength demodulation system that is inexpensive and easily implemented with a minimum of equipment, which can process many fiber optic sensors, yet be small enough to be integrated within the structural interface and thereby address the interconnect problem.
Abstract: Smart materials and adaptive structures will require structurally integrated fiber optic sensing systems that can operate in practical situations including harsh environments. The intracore fiber optic Bragg grating has considerable potential to serve as the sensor of choice for this emerging field. However, its role has been impeded by the lack of a simple, passive and fast method of determining the wavelength of its narrow back-reflected optical signal. The authors report on the development of just such a wavelength demodulation system that is inexpensive and easily implemented with a minimum of equipment. Furthermore, they shall show that this approach lends itself to the development of an optoelectronic chip that could process many fiber optic sensors, yet be small enough to be integrated within the structural interface and thereby address the interconnect problem-potentially one of the most critical facing the development of practical smart structures.
74 citations
01 May 1992
TL;DR: In this paper, the authors present a distributed system in which sensing and actuation repair occur when and where they are needed, in which materials containing various types of hollow fibers filled with a chemical which releases into the matrix at appropriate times, or over time, are designed to address some of the major issues of material performance.
Abstract: The subject of this research is the sensing of damage such ascracking or corrosion in a settable material by a chemical or physical sensorwhich, in the process of sensing, starts the activation of a remedial orprevention process. It is a distributed system in which sensing and actuationrepair occur when and where they are needed.Materials containing various types of hollow fibers filled with a chemicalwhich releases into the matrix at appropriate times, or over time, are designedto address some of the major issues of material performance.
17 citations
01 Jan 1992
TL;DR: In this paper, a smart structure is viewed as a structure or structural component on which are attached or embedded sensors and actuators whose actions are coordinated through a control system imbuing the structure with the capability of responding spontaneously to external stimuli exerted on the structure in proportion to their magnitudes to compensate for undesired effects or to enhance desired effects.
Abstract: A smart structure may be viewed as a structure or structural component on which are attached or in which are embedded sensors and actuators whose actions are coordinated through a control system imbuing the structure with the capability of responding spontaneously to external stimuli exerted on the structure in proportion to their magnitudes to compensate for undesired effects or to enhance desired effects. For example, to suppress vibration levels in a slender elastic beam, several researchers have demonstrated the feasibility of achieving reduced amplitudes by exploiting the sensing and actuation capabilities of piezoelectric ceramics or films bonded onto its surface. As the beam is deformed through the application of external forces, the simultaneously deformed piezoelectric sensor develops a surface charge proportional to the magnitude of the force. Upon processing this signal received from the sensor, the control system then impresses an appropriate voltage upon the piezoelectric actuator that induces a counteractive deformation and damping into the beam. The beam’s oscillations are subsequently quickly diminished.
13 citations
TL;DR: In this article, the authors describe a combined approach, utilizing these new capabilities, to the design, synthesis and characterization of a smart macromolecule which can function to control damage at the interface between a polymer matrix and a reinforcing fiber, and can also provide a colour change which will reveal the presence of the damaged region.
Abstract: Macromolecules offer many ways of creating smart materials. New capabilities for the predictive design of polymer molecules are coming from the rapid advances in computer modelling of the structure and properties of large molecules. Powerful chemical methods for the creation of polymeric modules that can be assembled in a variety of ways to perform useful, smart molecule functions are available. It has only recently become possible to observe directly segments of polymer molecules attached to solid surfaces, thanks to the techniques of scanning tunnelling microscopy and atomic force microscopy. This paper describes a combined approach, utilizing these new capabilities, to the design, synthesis and characterization of a smart macromolecule which can function to control damage at the interface between a polymer matrix and a reinforcing fibre, and can also provide a colour change which will reveal the presence of the damaged region.
12 citations
Journal Article•
9 citations
27 May 1992
TL;DR: Field-induced changes in the nonlinear properties of relaxor ferroelectrics and soft rubber are utilized to construct tunable transducers, which enable integration of different technologies into compact, multifunction packages.
Abstract: 'Smart' materials have the ability to perform both sensing and actuating functions. Passively smart materials respond to external change in a useful manner without assistance, while actively smart materials have a feedback loop which allows them to both recognize the change and initiate an appropriate response through an actuator circuit. One of the techniques used to impart intelligence into materials is 'Biomimetics', the imitation of biological functions in engineering materials. Composite ferroelectrics fashioned after the lateral line and swim bladders of fish are used to illustrate this idea. 'Very smart' materials, in addition to sensing and actuating, have the ability to 'learn' by altering their property coefficients in response to the environment. Field-induced changes in the nonlinear properties of relaxor ferroelectrics and soft rubber are utilized to construct tunable transducers. Integration of these different technologies into compact, multifunction packages is the ultimate goal of research in the area of smart materials. >
9 citations
01 May 1992
TL;DR: In this paper, a hybrid numerical method involving finite element modeling in the plate structure and transducer region and a plane wave representation in the fluid region is used to simulate the performance of smart materials that incorporate piezoceramics.
Abstract: Smart materials are expected to adapt to their environment and provide a useful response to changes in the environment. Both the sensor and actuator functions with the appropriate feedback mechanism must be integrated and comprise the `brains' of the material. Piezoelectric ceramics have proved to be effective as both sensors and actuators for a wide variety of applications. Thus, realistic simulation models are needed that can predict the performance of smart materials that incorporate piezoceramics. The environment may include the structure on which the transducers are mounted, fluid medium and material damping. In all cases, the smart material should sense the change and make a useful response. A hybrid numerical method involving finite element modeling in the plate structure and transducer region and a plane wave representation in the fluid region is used. The simulation of the performance of smart materials are performed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
9 citations
TL;DR: In this article, a method of controlling the elastic/viscoelastic behavior of a cantilever beam embedded with a bulk visco-elastic material having ''smart'' properties is addressed.
Abstract: With an external electrical stimulus, a method of controlling the elastic/viscoelastic behavior of a cantilever beam embedded with a bulk viscoelastic material having ``smart'' properties, is addressed. The test smart material used is constituted of a heteorogeneous mixture of barium titanate and ferrite (in powder forms) dispersed in a sol-gel phase of polyacrylamide with a specific aqueous content. The barium titanate content possesses the piezoelectric property that enables the material to exhibit electroelastic characteristics. The test beam made of plexiglass material keeps the smart material constrained in its core along its axis. When subjected to transient and static load conditions, and electrically stimulating the embedded smart material, the free-vibration damping characteristics of the test beam are elucidated. It is shown that the measured response of the cantilever beam excited to vibrate in its first natural mode can be controlled with the application of the voltage stimulation. Relevant ex...
7 citations
TL;DR: In this article, the authors describe a new smart material system using intercalated graphite as the material and using exfoliation as the phase transition that gives rise to the electromechanical switching action.
Abstract: The author describes a new smart material system using intercalated graphite as the material and using exfoliation as the phase transition that gives rise to the electromechanical switching action. In this action, a stress of up to 3 MPa (400 psi) or a strain of up to 4500% results reversibly from an applied electric field of only 7 V cm-1. This high-stress, high-strain, low-electric-field type of electromechanical switching is in sharp contrast to the electromechanical switching provided by piezoelectric materials. The exfoliation is a phase transition involving the vaporization of the intercalate between the graphite layers to form bubbles. For bromine as the intercalate, the bubbles remain mostly closed and exfoliation is reversible. The resulting stress or strain is along the c axis of the graphite, so highly oriented pyrolytic graphite and graphite flakes are both possible for achieving electromechanical switching. Applications of this new smart material include electrically activated thermal contacts, electrical contacts and micromanipulations.
7 citations
29 Jan 1992
TL;DR: The past five years has seen the emergence of a new field of engineering termed "Smart Materials and Structures" as discussed by the authors, which will lead to a revolution in engineering principles and a radical change in structures as diverse as: Aircraft and Space Platforms, Marine Vehicles and Installations, Ground Transportation Systems and Terrestrial Structures.
Abstract: The past five years has seen the emergence of a new field of engineering termed "Smart Materials and Structures." This multidisciplinary field will lead to a revolution in engineering principles and a radical change in structures as diverse as: Aircraft and Space Platforms, Marine Vehicles and Installations, Ground Transportation Systems and Terrestrial Structures.
TL;DR: In this paper, the progress made in developing these concepts into reality and attempts to define what the future applications are likely to be for these emerging "multidisciplinary" materials systems.
20 Oct 1992
TL;DR: Experimental applications to the adaptive control of space and automobile structures, active sonar absorbers and vibration and radiated noise are reviewed.
Abstract: Smart structures must adapt to their environment. Piezoelectric ceramics have proved to be effective as both sensors and actuators for a wide variety of applications. Realistic simulation models are needed that can predict the performance of smart structures that incorporate piezoceramics. A hybrid finite element method in conjunction with a boundary element technique is used to model the fields in and around a smart structure containing piezoceramic elements on an immersed structure. Numerical simulation can be used as a design tool for engineering smart materials. Experimental applications to the adaptive control of space and automobile structures, active sonar absorbers and vibration and radiated noise are reviewed. >
01 May 1992
TL;DR: In this article, the authors present a detailed analysis of phase transition properties of smart materials with memory and apply it to the problem of large deformation of magnetostrictive materials.
Abstract: : This report includes the following topics: Electromechanical Properties of Smart Materials; Effective Medium Theories for Piezoelectric Composites; Sensitivity Analysis for a Dynamic Model of Phase Transitions in Materials with Memory; Distributed Electro-Thermo-Mechanical Analysis of Shape Memory Alloy Actuators; Stress Driven Instability in Non-Hydrostatically Stressed Crystals and Its Role in the Problems of Crystalline Thin Films; Computational Methods for Identification and Feedback Control in Structures with Piezoceramic Actuators and Sensors; A Finite Dimensional Model Problem in Ferromagnetism; Numerical Minimization of Free Energy Functions for Diffusionless Phase Transitions; and Existence Results for Large Deformations of Magnetostrictive Materials.
TL;DR: In this paper, the authors present a guest editorial on Optical Fiber Sensor Based Smart Materials and Structures (OFTBSS) for OE Vol. 31 Issue 1, No.
Abstract: This PDF file contains the editorial “Guest Editorial: Optical Fiber Sensor Based Smart Materials and Structures” for OE Vol. 31 Issue 01
01 Jan 1992
TL;DR: A conference on the rapidly developing fields of smart materials and microelectro-mechanical systems produced papers in the areas of fabrication and characterization of ferroelectric thin films; polycrystalline silicon; optical, chemical, and biological sensors; thin film shape memory alloys; materials characterization; and alternative materials and applications as mentioned in this paper.
Abstract: A conference on the rapidly developing fields of `smart materials' and micro-electro-mechanical systems produced papers in the areas of fabrication and characterization of ferroelectric thin films; polycrystalline silicon; optical, chemical, and biological sensors; thin film shape memory alloys; materials characterization; and alternative materials and applications.
01 Dec 1992
TL;DR: In this paper, the feasibility of smart structural composite materials, in which the microstructure is modified with the introduction of a piezoelectric constituent, was investigated, and the results demonstrated self-sensing of strain and damage measurement in beam and shell elements.
Abstract: : The research culminated into the feasibility of smart structural composite materials, in which the microstructure is modified with the introduction of a piezoelectric constituent. Greater success was achieved in the sensing aspect of smart properties, enabling the material to have an inherent property of health monitoring. By sensing and quantifying elastic strain, the material can monitor its dynamic state (vibration), degradation and damage. In actuation, the material is readily suitable for active vibration control and manipulative damping. One out-growth of the results was an active fibrous sensor, which offers a readily viable alternative to a passive fiber-optic sensor as it is marred with breakage problems. A new concept of piezoelectric emission, analogous to acoustic emission, emerged which imparts the material ability to sense stress waves. This ability can be used to locate the regions of delamination and local fractures through fabrication to operational life of structure. Techniques were developed for deposition of thin piezoelectric (ZnO) film on carbon and metal fibers. Sensing and actuation properties were imparted into carbon fiber composites. The results demonstrated self-sensing of strain and damage measurement in beam and shell elements. The concept is ready for technological advancement and application. Smart materials, Structural materials, Carbon fiber composites.
01 Jan 1992
TL;DR: The Materials Research Symposium on the rapidly developing fields of smart materials and micro-electromechanical systems as mentioned in this paper was the first of its kind to be given by the Materials Research Society.
Abstract: This symposium marked the first of its kind to be given by the Materials Research Society on the rapidly developing fields of smart materials and micro-electromechanical systems. Originally we had planned to have symposia for each topic, however the materials issues tend to be very similar and thus both were combined. The organizers felt that this created some synergy and hopefully will inspire future uses of adaptive and active materials in these fields. The science and technology of the 21st century will rely heavily on the development of new materials. Such materials should be innovative with regards to structure, functionality and design. They will have characteristics similar to what has been projected for the current generation of smart structures; i.e. embedded sensors, actuators and control mechanisms that are fully integrated into the structure giving it the ability to sense stimuli imposed upon it and to take an appropriate response to those stimuli in a predetermined and controllable fashion. However, unlike smart structures, smart materials will be fabricated in such a manner that the sensors, actuators and control mechanisms will be part of the microstructure of the material itself. This will typically involve the design, synthesis and processing of such materialsmore » at the atomic and/or molecular level. As the rapidly growing field of micro-electromechanical systems (MEMS) develops, issues of material selection and material characterization will become increasingly important. Indeed, the number of materials which are available for use in the fabrication of MEMS is expanding dramatically. The papers in this volume consider the processing, characterization and application of a wide range of materials, including polycrystalline silicon (the traditional material for MEMS), ferroelectrics, optically active materials, metals, polymers, and more.« less
01 Mar 1992
TL;DR: The use of optical fibers as sensors in advanced composites has led in part to the development of smart materials and structures during the past ten years as mentioned in this paper, and this internal sensing capability makes the structures made from such materials "sense-able structures".
Abstract: The use of optical fibers as sensors in advanced composites has led in part to the development of smart materials and structures during the past ten years. During those years, embedded and attached fiber sensors have been developed to monitor composite cure, determine structural behavior during use, and detect the onset of material degradation and damage. This internal sensing capability makes the structures made from such materials "sense-able structures." This discussion reviews this established technology, and focuses on recent developments and directions.
01 Apr 1992
TL;DR: In this article, the results of the research and development activities focused on the development of a new generation of smart structures incorporating embedded hybrid multiple actuation systems which capitalize on the diverse strengths of both electrorheological fluids and piezoelectric materials, and employ fiber-optic sensing systems.
Abstract: : This final report documents the results of the research and development activities focused on the development of a new generation of smart structures incorporating embedded hybrid multiple actuation systems which capitalize on the diverse strengths of both electrorheological fluids and piezoelectric materials, and employ fiber-optic sensing systems. A state-of-the-art review of smart materials and structures technologies has been undertaken, and an in-depth critique of the current generation of actuators and sensors for smart structures applications has also been presented. An in-depth review of analytical, computational and experimental investigations on controlling the vibrational characteristics of beams, plates and a variety of prototype structural systems has also been undertaken. Furthermore ,variational formulations for predicting the performance characteristics of smart structures featuring hybrid embedded piezoelectric and electrorheological domains have been successfully developed. These formulations will form viable bases for the development of finite element design tools for Phase II. A comprehensive library of smart structures and articulating mechanical systems applications has been developed and documented. The principal research findings distilled from these comprehensive set of investigations clearly indicate that it is possible to significantly tailor the vibrational and aeroelastic characteristics of structural and mechanical systems for US Army applications.
01 Jan 1992
TL;DR: In this paper, the authors used the lateral line and swim bladders of fish to illustrate the idea of biomimetics in composite ferroelectrics and soft rubber to construct tunable transducers.
Abstract: Smart" materials have the ability to perform both sensing and actuating functions. Passively smart materials respond to external change in a useful manner without assistance, while actively smart materials have a feedback loop which allows them to both recognize the change and initiate an appropriate response through an actuator circuit. One of the techniques used to impart intelligence into materials is "Biomimetics," the imitation of biological functions in engineering materials. Composite ferroelectrics fashioned after the lateral line and swim bladders of fish are used to illustrate the idea. "Very smart" materials, in addition to sensing and actuating, have the ability to "learn" by altering their property coefficients in response to the environment. Field-induced changes in the nonlinear properties of relaxor ferroelectrics and soft rubber are utilized to construct tunable transducers. Integration of these different technologies into compact, multifunction packages is the ultimate goal of research in the area of smart materials.