In 1997 BMBF, within the framework of an idea competition for future-oriented key technologies and their industrial utilization, called for project proposals from industries and research for so-called 'Leitprojekts'. An independent group of experts selected few project proposals form the many submitted, and prosed them to BMBF for promotion. One of these projects is the BMBF-Leitprojekt ADAPTRONIK which is introduced in this paper. The Leitprojekt ADAPTRONIK which is conducted under the responsibility of Deutsches Zentrum fuer Luft-und Raumfahrt e.V. in Brunswick, focuses on the strucutre-conforming integration of piezoelectric fibers and patches in structures for lightweight construction. It is aimed at active vibration and noise reduction, contour deformation and micro-positioning in the very sense of adaptronics in various industrial applications. The project targets are prototype assemblies from the fields of automotive industry, rail vehicles, mechanical engineering, medical engineering, and aerospace.

Piezoceramic thin fibers and sheets of the same nominal chemical composition represent the active materials basis applied in the industrial research project 'Adaptronik' in Germany. Research activities and latest results concerning these Piezoceramic materials are discussed in the paper. Especially, progress has been attained in the PZT fiber technology. Fibers of complex chemical compositions have been prepared by a sol-gel process with diameters smaller than 20 micrometers showing a porefree microstructure with grains of 2-4 micrometers in diameter. The piezoelectric charge constant d₃₃ was nearly doubled in comparison to the undoped PZT fibers. Ceramic sheets have been supplied by CeramTec AG. The integration of PZT-fibers and -sheets into light weight structures made of glass or carbon fiber reinforced composites, may be realized via functional modules, which are tailored as robust sensing, actuating or damping components. The effective properties of these modules are deduced to provide a reliable database in view of the design and the operation of adaptive structures. Additionally, the preparation of 1-3 composites consisting of PZT-fibers and epoxy polymer was successful. This step opens new potentials for the design of advanced ultrasonic transducers. An aspect ration of 30 of the PZT phase in the transducers represents one of the outstanding features.

Up to now all mirrors verified and flown in interferometric optical and IR astronomic instruments on space missions documented in the literature have been passive systems. Preliminary investigations have shown that requirements of future systems like a significant reduction in mass while maintaining optical quality or an increase of optical quality at constant mass, as well as realization of mirrors with several meters in diameter while meeting all requirements for modern satellite systems can only be achieved by active shape control of the optical surface.

By introducing sinusoidal deformations on piezoelectric crystals using surface acoustic waves with spatial frequencies > 30 mm^-1 and amplitudes > 1 nm new optical diffractive elements can be generated. For high diffraction efficiencies it is necessary to produce amplitudes of the SAW as high as possible or to use light wavelength as short as possible. Conventional diffraction gratings are fixed in amplitude and spatial frequency whereas both can be varied for this new type of gratings. The gratings can operate in several environments such as N₂, He gas or vacuum and be remote controlled. Therefore they are a very flexible tool. First results on these gratings with frequencies up to 200 MHz and amplitudes in the order of 5 nm are shown.

Light weight structures - e.g. carbon fiber reinforced aeroplane parts or glass fiber reinforced robot arms - feature specific microscopic material structures resulting in the well known favorable mechanical properties.The integration of conventional actuators/sensors can adversely affect the mechanical properties. On the contrary, the actuators/sensors have to have a particularly small volume and stiffness - combined with a sufficient piezo electric efficiency.

Piezoelectric sensor arrays and sensor networks have been suggested as a means to monitor the integrity of composite structures throughout the service life for instance of an aircraft. Complex sensor systems will require significant additional expenditures with respect to cabling and electronics, with the added weight and effort possibly outweighing any benefits. Sensor positions in remote locations of an aircraft will often necessitate accessibility to these locations for maintenance purposes. For these reasons wireless, integrated sensors have recently become an object of increasing interest. Within the framework of a feasibility study various aspects of integrated wireless sensor system were investigated in detail. Particular emphasis was thereby laid on issues that are essential form a practical point of view, but that have not been discussed in the literature extensively. As a starting point a trade-off study between different sensor network configurations was conducted, form passive, remotely queried senors without power supply to fully functional active sensor pads with integrated power supply and electronics. Various concepts for the on-board energy supply of remotely queried sensor pads were studied and a comparison between rechargeable, and single-use batteries was performed. The suitability of different electronic components for integration into carbon fiber composites was investigated with particular emphasis on their survivability under typical temperature cycles experienced in autoclave runs. Finally, a crackwire sensor as an example of a passive remotely queried sensor system was pursued further in order to show the feasibility of such a wireless system for composite health monitoring purposes.

Previously, the results of embedding multi-axis fiber gratings into adhesively bonded joints were discussed. This paper presents more information on the testing of the adhesive joints and techniques employed to successfully embed a fiber grating sensor into such structures. These techniques include orienting the fiber, marking its orientation, and preparing it for embedment into the adhesive. Also discussed are strain relief methods for the egress of the fiber.

The recent studies suggest possible applications of shape memory alloy (SMA) for a smart health monitoring and suppression of damage growth. The authors have been conducting research and development studies on applications of embedded SMA foil sensors and actuators in CFRP laminates. The goal of this research is suppression of damage growth in CFRP laminates. At first, the authors proposed a concept of damage suppression in CFRP laminates. Then, the development studies are conducted in three phases. The first phase is the improvement of interlaminar shear strength between SMA and CFRP laminates. Some surface treatments were investigated for the improvement of bonding property by peel resistance test and single lap shear strength test. The second phase is the investigation of fabrication technique for producing a CFRP panel with embedded SMA foils. Fixture jigs were devised to introduce tensile loads during the fabrication process. The third phase is the strength demonstration of CFRP laminates with embedded SMA foils. Some strength test were conducted to obtain the design data for aircraft structures. It is confirmed that the shrinking force of pre-strained SMA influences to the strength and the crack density of CFRP panel.

A method of stretching optical fiber holds interest for measuring strain in smart structures where the physical displacement may be used to tune optical fiber lasers. A small, lightweight, low power tunable fiber laser is ideal for demodulating strain in optical fiber Bragg gratings attached to smart structures such as the re-usable launch vehicle that is begin developed by NASA. A method is presented for stretching optical fibers using the THUNDER piezoelectric actuators invented at NASA Langley Research Center. THUNDER actuators use a piezoelectric layer bonded to a metal backing to enable the actuators to produce displacements larger than the unbonded piezoelectric material. The shift in reflected optical wavelength resulting from stretching the fiber Bragg grating is presented. Means of adapting THUNDER actuators for stretching optical fibers is discussed, including ferrules, ferrule clamp blocks, and plastic hinges made with stereo lithography.

As part of the Defense Advanced Research Projects Agency (DARPA) SAMPSON program, a team has been developing and testing the use of smart materials for quieting turbomachinery. The team is composed of representatives form Pennsylvania State University, General Dynamics Electric Boat, GTE BBN Technologies, and the Naval Surface Warfare Center Carderock Division. Four concepts for quieting were proposed and wind tunnel testing, water tunnel testing, as well as computational fluid dynamic analysis were performed to down select two of the concepts for further consideration: protuberance and gap control. The wind tunnel testing was performed to determine the optimum shape of the protuberance. Water tunnel testing was performed at Penn State University/Applied Research Laboratory to establish the performance of the protuberance and gap control elements. Piezoelectric inchworm actuators, developed by PSU/Center for Acoustics and Vibration, were utilized for the evaluation of the two concepts. GTE BBN Technologies developed the control system simulation for the ultimate concept, the General Dynamics Electric Boat was responsible for hydrodynamic and hydroacoustic analysis. Naval Surface Warfare Center/Carderock Division performed hydrodynamic analysis and developed the rotary component design for the water tunnel test fixture. Successful testing in the twelve- inch diameter water tunnel at PSU/ARL demonstrated superior performance with the gap control concept over the protuberance control concept, and efforts are on-going to develop the final large scale demonstration. This paper summarizes the result of these activities.

This paper describes the application of Active Fiber Composite (AFC) actuators, a hybrid piezoelectric device, to the reduction of acoustic radiation from a cylindrical shell by active control methods. AFCs were developed to provide a mechanically robust method for large-area, orthotropic actuation and sensing in active structures. The actuation layer is formed by small diameter piezoelectric fibers that are unidirectionally aligned and imbedded in a resin matrix system. By the nature of its structure, an AFC actuator allows use of the primary piezoelectric effect in the plane of the composite. A cylindrical shell testbed is used for this experiment due to the predominance of this structure, and the resulting general interest, within the field of underwater acoustics. To control acoustic radiation from the cylindrical shell, the AFC actuators, placed at optimal locations determined using numerical models, are used to generate a strain field that counteracts the strain associated with acoustically efficient shell motions. Using an end-mounted accelerometer as the error measurement, an adaptive LMS algorithm is used to minimize the error signal in real-time. Experimental are supplied to validate both the device and the methodology in a complex, real-world environment.

The late 20th century has seen the evolution of smart structures technology form theoretical studies and bench level experimentation to demonstration on complex ground test articles and flight demonstration. This paper will discuss the role that the Air Force Research Laboratory (AFRL) and its government, industry, and academic partners have played in making this transition occur. The focus of the paper is on the flight experiments and large ground based demonstrations that have been led from these various activities. Directions for future research and activities that could motivate transition of the technology to operational system are also discussed.

This paper presents a review of the Air Force Research Laboratory advanced controls technology experiment program. Representing the first space-demonstration of smart structures technology, the ACTEX-I program has met or exceeded all program goals at each stage, beginning with the program initiation in 1991 through launch in 1996 to the conclusion of the Guest Investigator program and program conclusion in 1999. This paper will provide a summary of the ACTEX-I program from the AFRL perspective, focusing on lessons learned from the program both positive and negative.

The Air Force Research Laboratory is currently conducting a number of space flight experiments with the goal of demonstrating and transitioning smart structures technology to the operational user. Three of these experiments have focused on approaches for providing high-performance on- orbit isolation to precision spacecraft payloads. This paper will describe the design and performance of two systems that are slated for a 2000 launch; the vibration isolation, suppression, and steering experiments and the satellite ultra-quiet isolation technology experiment. Additionally, this paper will provide an overview of a third program initiated in 1999, the miniature vibration isolation system.

The Air Force Research Laboratory (AFRL) is sponsoring the Middeck Active Control Experiment Reflight (MACE II) Program. MACE II is a manned space experiment that evaluates the capabilities of adaptive control of flexible structures in the zero-g environment of the space shuttle's Middeck. MACE II has grown out of lessons learned from the original MACE flight and from AFRL sponsored structural control experiments. Previous experiments required extensive testing and 'tuning' for their particular test environment to meet their performance expectations. Such a process is too inefficient to be seriously considered for operational systems, especially space-based systems where access is limited. MACE II takes the next logical step by evaluating the capability of adaptive structural control algorithms AFRL has assembled a team of five small businesses and universities to develop and evaluate several adaptive control methodologies. In addition, AFRL has recruited a second science team led by the Massachusetts Institute of Technology to evaluate control system for time-varying and geometrically nonlinear systems. This paper is an overview of the AFRL science team only.

Future launch vehicle payload fairings will be manufactured form advanced lightweight composite materials. The loss of distributed mass causes a significant increase in the internal acoustic environment, causing a severe threat to the payload. Using piezoelectric actuators to control the fairing vibration and the internal acoustic environment has been proposed. To help determine the acoustic control authority of piezoelectric actuators mounted on a rocket fairing, the internal acoustic response created by the actuators needs to be determined. In this work, the internal acoustic response of a closed simply-supported (SS) cylinder actuated by piezoelectric (PZT) actuators is determined using a n impedance model for the actuator and boundary element analysis. The experimentally validated model is used to extrapolate results for a SS cylinder that emulates a Minotaur payload fairing. The internal cylinder acoustic levels are investigated for PZT actuation between 35 and 400 Hz. Significant reductions in the structural response due to increased damping do not equate to similar reductions in the acoustic SPLs for the cylinder. The sound levels at the acoustic resonant frequencies are essentially unaffected by the significant increase in structural damping while the acoustic level sat the structural resonant frequencies are mildly reduced. The interior acoustic response of the cylinder is dominated by the acoustic modes and therefore significant reductions in the overall interior acoustic levels will not be achieved if only the structural resonances are controlled. As the actuation frequency is reduced, the number of actuators required to generate acoustic levels commensurate to that found in the fairing increases to impractical values. Below approximately 100 Hz, the current demands reach levels that are extremely difficult to achieve with a practical system. The results of this work imply that PZT actuators do not have the authority to control the payload fairing internal acoustics below approximately 100 Hz.

The unique combination of composite structures, SMA actuators and optical fiber sensors provides an opportunity to obtain lightweight adaptive structures for spacecraft with increased reliability and reduced payload resources. In particular, by taking advantage of the mechanical properties of certain classes of asymmetric laminated composite structures, it is possible to design and fabricate structures that possess a multitude of stable shapes. Very little energy is required to force the structure to move from one stable shape to another, and the inherent stability of the structure means that the applied energy can be removed immediately upon actuation. This conserves power and makes this class of materials uniquely adaptable to space applications, where power for actuators is at a premium. We will describe the results of a two-year program to fabricate such a structure, instrument it with optical fiber sensors, and qualify it for launch on the MightySat II.1 satellite.

Payloads are attached to launch vehicles by structural adapters known as Payload Adapter Fittings (PAF). The adapters are substantially rigid; therefore, the launch vehicle vibration is transmitted without isolation to the payloads. The payload cost includes a substantial component for provision to withstand the severe launch vibration environment. In this paper, a novel three degree-of-freedom isolation system built in the footprint and within the existing PAFs is presented. The vibration isolator consists of a mechanical constraining mechanism that prevents the rotation of the payload relative to the launch vehicle in both rocking rotation and rotation about the long axis of the launch vehicle. The above rotational motion restraining mechanism would therefore only allow axial and lateral vibration of the payload relative to the launch vehicle. The second major component of the system consists of isolation components that are used to reduce vibration in the latter to directions, i.e., in the axial and the lateral directions. The proposed isolating payload adapter fitting also has a stand-alone thrust-support preload adjustment component that adjusts for the varying quasi-static acceleration seen in different flight regimes in a passive- adaptive control mode. The advocated isolation system is structurally modular and parameterizable such that a range of launch vehicle platforms could be accommodated. Through the utilization of the advocated isolating payload adapter fitting, a fifty percent reduction in vibration transmission is achieved at 10 Hz in the axial direction and 20 Hz in the lateral directions. A 40 db reduction is achieved at frequencies above 100 Hz. Active actuating elements may easily be included in the prosed design to attain an active isolation unit.

The Shape Memory Alloy (SMA) Consortium (SMAC) has been developing actuators and magnetically actuated SMA materials. This paper will summarize the overall SMAC developments, and concentrate on the development of a SMA torsional actuator. This is being developed for quasi-static twisting the V-22 rotor blades for added performance. The paper provides updated results to the 1999 SPIE paper on this subject, including further and more focused development of the actuator that combines thermoelectric heat control with SMA materials.

Spacecraft require a variety of mechanisms to accomplish mission-related functions such as deployment, articulation, and positioning. Current off-the-shelf devices such as pyrotechnic separation nuts, paraffin actuators, and other electro-mechanical devices may not be able to meet future satellite requirements, such as low shock and vibration, and zero contamination. The Air Force Research Laboratory (AFRL), with corporate and government partners, has developed Shape Memory Alloy (SMA) spacecraft release mechanisms and hinges as alternatives. In order to meet future goals, the SMA devices have been designed to reduce shock and vibration, reduce parts, and eliminate pyrotechnics. This paper will focus on descriptions and results of on-orbit SMA mechanism experiments and applications. AFRL has flown SMA release devices as part of the Shape Memory Alloy Release Device (SMARD) experiment on MightSat I. The SMARD experiment, that compared the shock and release times of two SMA devices with those of current off-the-shelf devices, was conducted in May 1999 with extremely successful results. In addition, four AFRL funded SMA release mechanisms successfully deployed the Air Force Academy FalconSat spacecraft from the Orbital Sub-Orbital Program Space Launch Vehicle in January 00. AFRL has also conducted an on-orbit experiment with SMA hinges. The hinges were flown as part of the Lightweight Flexible Solar Array program, that was a joint AFRL/DARPA/NASA/Lockheed Martin program to develop innovative solar array technologies. Six SMA hinges were launched as part of the LFSA experiment on the Space Shuttle Columbia in July 1999 with successful results.

NASA's High Displacement Actuators (HDAs) are being examined for several potential aerospace applications. In order to determine if these HDAs are suitable for these applications, the strain must be determined as a function of applied voltage and stress over the range of temperature required for the environment of space. Additionally, the variability between HDAs of the same design must be determined to establish their performance average and standard deviation. Towards this end, a matched set of rectangular HDAs were fabricated and characterize to determine their on-center displacement. These actuators were run at a 1 Hz frequency using peak-to-peak voltages from 100 to 800 volts with a maximum negative voltage of -150 volts. The test temperature ranged from -101 to 66 degrees C at 28 degrees C intervals. Loads ranging form 50g to 1450g were line loaded on center to observe the effects of strain on displacement. After preliminary characterization, these HDAs were incorporated into a prototype linear motor drive system for satellite instrumentation. This paper describes the fabrication, test methodology and the resulting performance of these HDAs as well as the linear piezo motor.

A design consisting of an elliptical metal shell whose long axis is occupied by prestressed multilayer actuators can be applied to a large variety of piezoelectric structures to offer compact, low-voltage actuation at operating frequencies that range from DC to 40 kHz. The useful motion or vibration is recovered in the transverse direction, at the extremities of the short axis. The elliptical shell serves as an amplification mechanism. Its dimensions determine the output characteristics of the device in terms of strain, force and resonance frequency. This paper presents the design of three structures based on this concept. 3D finite element analysis result as well as experimental measurements are presented.

The Boeing Active Flow Control (AFC) System (BAFCS) is a DARPA sponsored program to develop AFC technology to achieve a significant increase in payload for the V-22 tiltrotor vehicle. The program includes Computational Fluid Dynamics analysis, wind tunnel testing and development of smart materials based AFC actuators. This paper will provide an overview of the program and its interrelationships, as well as concentrating on the development of the AFC actuators.

Current research has shown that aircraft can gain significant aerodynamic performance benefits by employing active flow control (AFC). One of the enabling technologies of AFC is the synthetic jet. Synthetic jets, also known as zero-net-mass flux actuators, act as bi-directional pumps injecting high momentum air into the local aerodynamic flow. Previous work has concentrated on high frequency synthetic jets based on piezoelectric active diaphragms such as Thunder actuators. Low frequency synthetic jets present a unique challenge requiring large displacements, which current technology has difficulty meeting. Boeing is investigating novel shaped low frequency synthetic jets that can modify the flow over fixed aircraft wings. This paper present the initial study of two promising active diaphragm concepts: a crescent shape and an opposing bender shape. These active diaphragms were numerically modeled utilizing the general-purpose finite element code ABAQUS. Using the ABAQUS results, the dynamic volume change within each jet was calculated and incorporated into an analytical linear Bernoulli model to predict the velocities and pressures at the nozzle. Simulations were performed to determine trends to assist in selection of prototype configurations. Prototypes of both diaphragm concepts were constructed from polyvinylidene fluoride and experimentally tested at Boeing with promising results.

Under a joint research and development effort conducted by the National Aeronautics and Space Administration and the Boeing Company three neural-network based control system were developed and tested. The control system were experimentally evaluate using a transonic wind-tunnel model in the Langley Transonic Dynamics Tunnel. One system used a neural network to schedule flutter suppression control laws, another employed a neural network to schedule flutter suppression control laws, another employed a neural network in a predicative control scheme, and the third employed a neural network in an inverse model control scheme. All three of these control schemes successfully suppressed flutter to or near the limits of the testing apparatus, and represent the first experimental applications of neural networks to flutter suppression. This paper will summarize the findings of this project.

A small low-cost piezoceramic linear motor has been developed in the US and is being commercialized by EDO Corporation, working with a leading motion control OEM and with a prominent US corporate research laboratory. First generation motor design has emphasized high displacement at up to 200mm per second velocity with 3.5 Newtons force with high resolution, short time constant and a 15 volt power supply at a cost of less than 100 dollars. Motor dimensions of 30 by 50 by 4 mm allow broad configuration choices, al hidden within the motion control slide. The EDO approach was to build on its core competence in high reliability electroceramic material engineering and production, and to use a strategy of back-integrating, or outsourcing of recent advances outside Edo in piezoceramics, while forward- integrating into specific emerging applications known intimately by the OEM in the market. The strategy provided design focus that has led to a cost-effective advance in 'solid-state actuation and control'. This is considered a classic case of successful industrial integration of an enabling technology across organizations in order to access the needed mix of technology for development of an innovative and competitive solution.

High resolution metrology and production systems are pushing the capability of existing pneumatic isolation systems. The need for better isolation at low frequency is growing as mechanical noise further constrains the lower limits of many electro-optical technologies and techniques. Unfortunately, the problem is magnified due to the 1-4 Hz natural frequency of pneumatic isolators. An active damping system, the Activator, uses an electromagnetic actuator to apply a damping force to an isolation table to reduce the transmission of these low amplitude, low frequency vibrations from the floor to the table. The system is low cost and easy to install. The controller, sensor, and electronics are integrated with the actuator. Given floor excitations on the order of submicrons, a 12 dB attenuation in transmissibility is achieved. This level of performance was attained after overcoming many physical hurdles due to the very low frequencies and small measurement signals. This unique, self-contained active damper result in a system more tolerant of existing floor locations and environments and is a simple upgrade, relieving the end user of facility improvements or relocation costs. This paper describes these challenges and shows how the performance goals were met providing a compact, economical system.

This work presents a theoretical model for the damping force of a magneto-rheological fluid (MRF) shock absorber of an off-road motorcycle. The Bingham plastic model and a 3D electromagnetic finite-element analysis are employed to develop a theoretical model to estimate the damping force of a MRF shock absorber. The mode is based on the physical parameters of the device as well as the properties of the fluid, making a valuable tool in shock absorber design for a particular application. By comparing the theoretical and experimental results, it is demonstrated that the model accurately predicts the damping force.

This paper presents the development and evaluation of field- controllable, semi-active magneto-rheological fluid (MRF) shock absorbers for a mountain bicycle. Recent trends in the bicycle industry show a movement towards semi-active suspension systems. Two new MRF dampers are designed and tested with the intent of being used on the front and rear suspension of a modern mountain bicycle. The MRF shock absorbers are designed to emulate the performance of the original equipment manufacturer shock absorbers in passive mode. Application of an input electric current to the MRF shock absorber causes a dramatic increase in the damping capacity. Procedures and results are presented for the design and experimental characterization of these MRF dampers.

In this study a piezoelectric actuator was designed and built to subject osteoblasts and human endothelial cells to cyclic tensile strains in order to study the effects of such loading on cell growth. As the cells are quite sensitive and must be kept submerged in a culture media at all times, a device was constructed to hold the cells in place and to subject them to loads inside a petri dish. Critical aspects of the design were a limited choice of materials because of biocompatibility and the need for sterilization, and the required strain levels to which the material was to be subjected. Current deices for stretching cells cannot consistently produce such small strains. This paper describes how a THUNDER piezoelectric actuator was used as the prime mover in a device designed to excite cells under conditions that have not yet been achieved in the lab.

The displacement output of the telescoping actuators, as developed in the NRL, depend on the material properties. Recently developed relaxor ferroelectric materials, with compositions near the morphotropic phase boundary and in single crystal forms, show high strain output capability and high coupling coefficients. These materials, when design into devices, would provide high performance, in terms of displacement output, and high transduction efficiency. We have utilized one of these single crystal materials, namely, lead zinc niobate-lead titanate, PZN-PT, for the construction of the NRL telescoping actuators. The evaluation of the piezoelectric performance of these single crystal-based telescoping actuators showed much higher displacement outputs than that for the ones previously made with polycrystalline PZT ceramics.

Design and analysis of a scalable piezohydraulic actuation system is presented. Efficiency analysis of frequency rectification demonstrates that hydraulic actuation transfers the maximum amount of work from the actuator to the load. The ratio of peak electrical power to average power delivered caries from 8 percent to 25 percent depending on the piezoelectric coupling coefficient, highlighting the need for efficient power electronics to minimize heat dissipation in the system and minimize volume. A lumped parameter system model demonstrates that fluid compliance is the limiting facto in the stiffness of a bidirectional actuator that does not require hydraulic accumulators or four-way valves. A benchtop experiment consisting of a piezoelectric shock actuator, pumping chamber, and a linear hydraulic cylinder is developed and tested to determine the effect of friction on the micron- level motion of the actuator. The effects of friction are minimized by applying a pneumatic precharge to the system and driving the actuator at its maximum voltage level. Friction is not deemed a limiting factor to the development of a piezohydraulic system with stroke outputs on the order of 100 micrometers per cycle.

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.

RolaTube Technology has developed a smart structures technology called bi-stable reeled composite. Made from layers of reinforced thermoplastic, BRC can alternate between two stable forms; that of a strong, rigid structure and that of a compact coil of flat-wound material.

A novel concept proposed is the use of SMA to reduce the panel thermal deflection and linear flutter responses. SMA has the unique ability of recovering large prestrain completely when the alloy is heated. During the recovery process, a large tensile recovery stress occurs if the SMA is restrained. In this paper, a panel subject to the combined aerodynamic and thermal loading is investigated. A nonlinear finite element model based on von Karman strain displacement relation is utilized to study the effectiveness of an SMA embedded panel on the flutter boundary, critical buckling temperature and post-buckling deflection. The study is performed on an isotropic panel, with embedded SMA. The aerodynamic model is based on the first order quasi-steady piston theory. The aerodynamic pressure effect on the buckling and post-buckling behavior of the panel is investigated by introducing the aerodynamic stiffness term, which changes both the critical buckling temperature and the post-buckling shape. Panels with SMA embedded in either x or y-direction and either partially or fully embedded are investigated for post-buckling behavior. Similarly, the influence of the temperature elevation on the flutter boundary is investigated by including the thermal terms.

A finite element method for predicting critical temperature and postbuckling deflection is presented for composite plates embedded with prestrained shape memory alloy (SMA) wires and subjected to high temperatures. The temperature- dependent material properties of SMA and matrix, and the geometrical non linearities of large deflection are considered in the formulation. An incremental method consisting of small temperature increments and including the effect of initial deflection and initial stresses for materials non linearities is presented. Within each temperature increment, the Newton-Raphson iteration method is used for calculating large thermal deflection. Results show that the critical buckling temperature can be raised high enough and the postbuckling deflection can be reduced and controlled for a given operating temperature range by the proper selection of SMA volume fraction, prestrain and alloy composition.

A finite element formulation and solution procedure for the free vibration behavior of composite plates with embedded shape memory alloy (SMA) at elevated temperatures is presented. The temperature-dependent material properties of MA and composite matrix, and the geometrical nonlinearity due to large thermal deflection are considered in the formulation. The solution procedure consists of two steps: large thermal deflection is determined first, then followed by the free vibration analysis about the thermally buckled equilibrium position. Examples of hybrid composite plates are given to show the variation of lowest few frequencies versus temperature and the influence of SMA on the natural frequencies at elevated temperatures. Potential applications to frequency turning and sonic fatigue using SMA are discussed.

The thermomechanical performance of a shape memory alloy hybrid composite beam specimen is demonstrated and used in a preliminary validation study of a recently developed constitutive model and finite element formulation for analysis of such structures. A brief description of the thermoelastic formulation is given. A material system consisting of a glass/epoxy matrix with embedded Nitinol actuators was chosen for this study. Results from Nitinol material characterization testing, beam specimen fabrication processes, and base acceleration testing for measuring the dynamic response performance in presented. Selected results from the dynamic test are shown, interpreted, and compared with predictions form the FE model. Elimination of a thermal post-buckling deflection by the activated SMA was observed. The fundamental natural frequency is shown to increase by a facto of 5.3 and the RMS displacement response is attenuated by a factor 6.4. Preliminary comparisons between predicted and measured performance is good. Discrepancies are attributable to insufficient knowledge of the matrix material properties at elevated temperature.

The capability of periodic structures to act as filters for traveling waves is used to control the longitudinal wave propagation in rods. Shape memory inserts placed periodically along the rods act as sources of impedance mismatch with tunable characteristics. Such characteristics are attributed to the unique behavior of the shape memory alloy whereby the elastic modulus of the inserts can be varied up to three times as the alloy undergoes a phase transformation. With such controllable capability, the inserts can introduce the proper impedance mismatch necessary to reduce the wave propagation. An analytical model based on the transfer matrix approach is developed to predict the performance of the periodic rods with shape memory inserts. The activation temperatures of the shape memory inserts are controlled using two different strategies. The propagation constants as well as the response of the composite rod are first evaluated when the inserts are all activated at the same temperature. The obtained results show that changing the thermal activation modifies the width and location of the pass and stop bands. The rod can therefore be tuned to attenuate waves propagating at selected frequencies. The tunable characteristics of the shape memory alloy are also used to introduce irregularities in the periodic structure. The source of disorder is the variance in the activation temperature of the inserts. Disorder in the periodicity typically extends the stop-bands into adjacent propagation zones. More importantly, it produces the localization of the vibration energy near the excitation source. The obtained results demonstrate the localization phenomenon and its control through appropriate tuning of the level of disorder in the activation temperatures. The theoretical investigations presented here provide guidelines for the level of disorder in the activation temperatures. The theoretical investigations presented here provide guidelines for designing tunable periodic structures with high control flexibility where propagating waves can be attenuated and localized.

For given displacement amplification ratios, resonant 3- section waveguides are geometrically more compact than simpler taper-only displacement-amplifying waveguides. For resonant 3-section exponential waveguides, an explicit solution is derived for finding the node and the maximum dynamic stress in each section. The node serves as the mounting location for waveguides driven by quarter- wavelength magnetostrictive TERFENOL-D transducers with reaction mass. The waveguide tip is loaded by water begin atomized and propelled for industrial purposes. The relatively broad bandwidth of TERFENOL-D can be exploited to reduce overall sensitivity to impedance mismatches between the waveguide tip and the load.

The formulation of an optimization problem for the design of a current controlled switching power amplifier to drive a piezoelectric actuator is the subject of this paper. The design is formulated as a continuous optimization problem. A detailed model that includes the anhysteretic nonlinearity between the electric field and polarization is developed and is coupled with a dynamic model of the amplifier. The design specifications are formulated as optimization constraints. The objective function is chosen to be the weight of the inductor. Optimization results are presented to demonstrate the efficiency of the proposed design morphology.

Active Fiber Composites (AFCs) provide a novel method for large scale actuation and sensing in active structures. The composite comprises unidirectionally aligned piezoelectric fibers, a resin matrix system, and interdigital electrode. AFCs have demonstrated distinct advantages over current monolithic piezoceramic actuators, including: higher planar actuation strain, tailorable orthotropic actuation, robustness to damage, conformability to curved surfaces, and potential for large area distributed actuation/sensing system. This manuscript focuses on recent developments in three key areas. The first area describes the completion of a standard AFC baseline material. The baseline AFC consists of 5.5mil diameter PZT-5A fibers laminated with an epoxy film adhesive and silver screen-printed electrodes. A scalable fabrication process based on lamination industry equipment has been implemented. Baseline AFC performance has been characterized, including free strains and blocked force. The send area describes continued work in developing optimized geometry/materials for future AFCs. AFC performance and efficiency can be affected significantly by changes in electrode pitch and fiber diameter and/or cross- sectional geometry. Various improved design have been identified. Third is review of application demonstration that exploit the benefits of AFCs to solve structural control problems.