Active Fiber Composite Actuator Research Articles

Transient analysis and control of delaminated composite plates in hygrothermal environment using active fiber composite actuator

In the present article, the transient analysis and control of delaminated composite plates under hazardous environmental conditions using active fiber composite (AFC) is discussed. Top and bottom layers of the laminated composite plate are embedded AFC layers. The present investigation utilizes AFC as an actuator and sensor. A finite element model for centrally located delamination is developed and coded in Matlab. The proportional controller is used to control the undesirable response in real time. The transient response of the smart delaminated plate is studied for different temperatures and moisture conditions. The feedback control of the dynamic response is performed with the help of velocity and displacement feedback gain to the AFC actuator. The key observations from the numerical studies are; the dynamic response and the frequency response of composite plate increase due to delamination and also with the increase of the temperature and moisture concentrations. The response reduces when the feedback control loop is activated. So, the overall performance of the delaminated plate structure in hygrothermal environment may be enhanced.

Vibration analysis and control of delaminated and/or damaged composite plate structures using finite element analysis

The present article deals with the vibration analysis of delaminated and/or damages composite plate structures. Delamination and/or debonding occur in the laminate due to various load and extreme environmental conditions in their service time. A Matlab based finite element model is developed for centrally located delamination. The Active Fiber Composite actuator layer is placed at top or bottom of the laminated plate. A small delamination in the mid-plane is considered. Numerical results are generated for different boundary conditions and delamination sizes. The formulation of the governing equation is based on minimum potential energy approach. The key observation is that natural frequencies decrease due to delamination because of a decrease in stiffness of the structures. Certain local mode shapes can also be observed in the delamination region. The stiffness of the delaminated composite plate can be enhanced by applying voltage to the active fibre actuator layer.

Durability Characterization of Active Fiber Composite Actuators for Helicopter Rotor Blade Applications

Theprimary objective of this work was to characterize the long-term durability performance of the Active Fiber Composite (AFC) actuator material system for the Boeing Active Material Rotor (AMR) blade application. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes. These actuators were integrated directly into the blade spar as active plies within the composite structure to perform structural actuation for helicopter vibration control. Therefore, it was necessary to conduct extensive electromechanical material characterization to evaluate AFCs both as actuators and as structural components of the blade. The long-term durability characterization tests designed to extract important electromechanical properties were electrical fatigue tests and mechanical fatigue tests. This paper presents the test results as well as the comprehensive testing process developed to evaluate the relevant AFC durability properties. The durability tests conducted under simulated electromechanical loading conditions expected on AFCs during the blade operation provided an invaluable insight into the behavior of the AFCs under dynamic loading environment. The results from this comprehensive durability characterization of the AFC material system supported the design and operation of the Boeing AMR blade scheduled for wind tunnel tests.

COMPARISON OF STRUCTURAL–ACOUSTIC CONTROL DESIGNS ON AN ACTIVE COMPOSITE PANEL

This work presents a comparison of three technologies for structural–acoustic control that, while prevalent in the literature, had not been compared on a single structure. The comparison is generalizable because the techniques are implemented on a panel structure representative of a more complex structure (e.g., an aircraft fuselage, a submarine vehicle hull, a satellite payload shroud, etc.). The test-bed used for this comparison is a carbon-fiber composite panel manufactured with embedded active fiber composite actuators. Since such integrated structures constitute a continued avenue of research, the manufacturing and performance of this structure is illustrated. The design of the test-bed is guided by an effort to achieve a dynamic response similar to a single panel in a typical aircraft or rotorcraft fuselage.Existing active control architectures for broadband acoustic radiation reduction are compared both analytically and experimentally on a representative structure to quantify the capabilities and limitations of the existing control methodologies. Specifically, three broad categories of control are compared: classical feedback (rate feedback), optimal feedback (linear quadratic Gaussian), and adaptive feedforward control (x -filtered least mean square). The control architectures implemented during this study are all single-input/single-output in order to allow a fair comparison of the issues involved in the design, as well as the use and performance of each approach. Both the vibration and the acoustic performance are recorded for each experiment under equivalent conditions to allow a generalizable comparison. Experimental results lead to conclusions pertaining to the application of active structural-based control to improve the acoustic performance of more complex structures.

Active fiber composite actuators for reducing acoustic radiation from cylindrical shells

Active fiber composites were developed to provide a mechanically robust method for large-area, orthotropic actuation and sensing in active structures. This presentation will describe the application of active fiber composite actuators to the reduction of acoustic radiation from a cylindrical shell by active control. The composite actuation layer is formed by small diameter piezoelectric fibers that are unidirectionally aligned and imbedded in a resin matrix system. A separate, etched, interdigital electrode layer makes the electrical connections. By nature of its structure, an active fiber composite actuator or sensor allows use of the primary piezoelectric effect in the plane of the composite. Active fiber composites are inherently tolerant of damage and can be conformed to a wide range of structural shapes. To control acoustic radiation from a cylindrical shell, active fiber composite actuators are used to generate a strain field that counteracts the strain associated with acoustically efficient shell motions. Optimal placement of the actuators is determined using numerical models verified by an experimental characterization of the shell dynamics. The control signal applied to the actuator is determined, in real time, using adaptive control. Error sensing methods using accelerometers or active fiber composite sensors were considered. [Work supported by DARPA.]