Macro Fiber Composite Research Articles

The synergism of peak to peak value, frequency and superimposed DC bias voltage on electric-field-induced strain of PZT based-macro fiber composites

The macro fiber composites (MFCs) with uniform and repeatable electromechanical performance have been a popular choice in various applications like structural actuation, vibration control, structural health monitoring, and energy harvesting. Herein, the strains of lead zirconate titanate based MFCs subjected to various driving signals were conducted via the strain-electrometry method. The formation mechanism of the strains was profoundly expounded, and the variation of the strains as a function of peak to peak value, frequency and superimposed DC bias voltage was further explored. The results demonstrate that both longitudinal and transverse strain-voltage curves with the voltage cyclic loading are closed “ellipse-like” hysteresis loops, in which the strain of ascending branch is smaller than that of the descending branch. Both strains increase with increasing the peak to peak value of driving signal and the increase is more remarkable at smaller bias voltage and lower frequency, while decrease with increasing the positive DC bias voltage and the decrease is specially obvious at larger peak to peak value and lower frequency. Besides, the dispersive effect of the strains induced by larger peak to peak value, particularly with smaller superimposed bias voltage, is more apparent than that induced by smaller peak to peak value. The longitudinal and transverse strains of MFCs with an active area of 40 mm × 30 mm range from 74.8 με to 1688.3 με, and 20.3 με to 488 με, respectively. This research indicates that through properly and carefully synthetical modulation of electrical parameters of driving signal, a notably enhanced strain can be achieved in MFCs for the specific applications such as actuation and high frequency structural control.

Macro fiber composite-based energy harvester for human knee

The harvesting of energy from human motion for portable and wearable electronic devices has received considerable attention. This letter describes a lightweight macrofiber composite (MFC)-based energy harvester for capturing biomechanical energy through the natural motion of the human knee. In the proposed device, a slider-crank mechanism is used to transform the rotary motion of the knee joint to linear motion, and a bending beam is used to transform the linear motion to a bending motion. When walking, a bending deformation is induced in two MFC slices attached to the bending beam, generating electrical energy. To test the performance of the developed device, treadmill tests at various walking speeds and resistive loads are performed. Experimental results show that the lightweight harvester (weighing just 307 g) can generate 1.60 mW without increasing the human effort required for walking. This is expected to significantly promote the usage of biomechanical energy harvesters.

Piezoelectric energy harvesting based on macro fiber composite from a rotating shaft

Piezoelectric energy harvesting from rotating applications can be realized by the use of harvesters, the basic part of which is a piezoelectric material. Such harvesters have various structures but most of them contain a cantilever composite beam, which consists of the carrying material and the piezoelectric material. A diversification of the harvester structures is, above all, the result of the application of additional mechanical structures, the task of which is to deform the cantilever composite beam. In contrast to these approaches, this article presents the simulation and laboratory investigation of the piezoelectric energy harvesting from a rotating shaft without the use of any additional mechanical structure. Energy harvesting was realized by the use of macro fiber composite (MFC), which was directly glued onto the rotating shaft surface, instead of on a cantilever beam being a part of the additional mechanical structure. In the theoretical part of the article, a mathematical model of piezoelectric energy harvesting from the rotating shaft with the use of MFC was elaborated. This model was verified on the basis of the laboratory experiments. On the basis of the simulation and laboratory experiments it was found that both an increase in the rotation frequency of the shaft and an increase in the stress in a rotating shaft caused a linear increase in the voltage generated by the MFC and caused an exponential increase in power generated by the MFC. These characteristics are significantly different to the characteristics obtained for harvesters consisting of a cantilever beam, in which the maximal value of a voltage and a power is generated only for a resonant frequency of a cantilever beam. In spite of these differences the optimal load resistance for the specific rotation frequency of the shaft can be calculated from the formula used to calculate the optimal load resistance for a harvester based on a cantilever beam.

Experimental investigation on a flapping beam with smart material actuation for underwater application

This paper presents an experimental investigation of flapping beam for thrust generation. The beam is studied in current of water and actuated by the “Macro-Fiber Composite (MFC)” based smart material to undergo flapping and undulatory motions, mimicking a fish. The results obtained are expected to be useful in designing process of robotic fish in different marine environment. Herein, the average power spent for actuation is measured and it is observed that the maximum efficiency obtained is 55% for the frequency of 2.0 Hz. The set of experiment of the undulatory smart beam conducted at different depths of submergence showed that an increase in depth of submergence lead to increase of the thrust. However, in the region between the free surface and bottom of the channel (i.e. mid-depth) the thrust is low. By analyzing the measured data, threshold value of “Elastio-Inertia” number for low input power and high efficiency is determined. The results obtained are expected to help in better understanding the swimming pattern, locomotion of fish and other sea creatures. Also, it contributes to the design and development of motor-less and gearless thrust generation mechanisms for the marine vehicles and robots.

Simulation Analysis of Bionic Robot Fish Based on MFC Materials

With the development of marine resources, research on underwater robots has received unprecedented attention. The discovery and application of new smart materials provide new ideas for the research of underwater robots, which can overcome the issues of traditional underwater robots and optimize their design. A macro fiber composite (MFC) is a new type of piezoelectric fiber composite that combines actuators and sensors. The material has excellent deflection, good flexibility, and a high electromechanical coupling coefficient. Bionic mechatronics design is an effective way to innovate mechatronics in the future and can significantly improve mechatronics system performance. As an important issue for the design of bionic mechatronics, it is necessary to make robots as soft as natural organisms to achieve similar biological movement with both higher efficiency and performance. Compared with traditional rigid robots, the design and control of a soft robotic fish are difficult because the coupling between the flexible structure and the surrounding environment should be considered, which is difficult to solve due to the large deformation and coupling dynamics. In this paper, an MFC smart material is applied as an actuator in the design of bionic robotic fish. Combined with the piezoelectric constitutive and elastic constitutive equations of the MFC material, the voltage-drive signal is converted to a mechanical load applied to the MFC actuator, which makes the MFC material deform and drives the movement of the robotic fish. The characteristics of caudal fin motion during the swimming process of the bionic robotic fish were analyzed by an acoustic-solid coupling analysis method. The motion control analysis of the bionic robotic fish was carried out by changing the applied driving signal. Through numerical analysis, a new type of soft robotic fish was designed, and the feasibility of using an MFC smart material for underwater bionic robotic fish actuators was verified. The new soft robotic fish was successfully developed to achieve high performance.

Internal Resonance Responses of Rectangular Cross-Ply Composite Plates with Graphene Skins

This paper presents an investigation on the nonlinear dynamic behavior of three-phase rectangular composite plates made of cross-ply macro fiber composites (MFC) in the polymer with graphene (GP) skins, which are uniformly dispersed at the top and bottom surfaces of the plates. According to the mixture rules for multi-components of composite materials, the constitutive laws for MFC-GP composite materials can be obtained. A simply-supported rectangular plate model subjected to a transversal excitation in thermal environments is considered. The governing equations are formulated by using the first-order shear deformation theory, von Kármán geometrical kinematics and Hamilton’s principle. The Galerkin approach is used to discretize the governing equations for analysis. The vibration frequencies of MFC-GP composite plates with different modes are presented and the case of 1:2 internal resonance is selected to be investigated here. Three different coupled forms (i.e. uncoupled, weakly coupled and strongly coupled cases) of two vibration modes are presented. In addition, the influences of various parameters, including volume fraction of graphene, applied voltage, temperature effect and external excitation, on the nonlinear dynamic characteristics of MFC-GP composite plates are also examined.

Experimental analysis of active–passive vibration control on thin-walled composite beam

In the study presented, active and passive vibration control techniques for a thin-walled composite beam were developed and experimentally analysed. An MFC (Macro Fibre Composite) actuator was used, together with the magnetic forces between two permanent cuboidal magnets (passive vibration control) for vibration damping applications. After the experiments conducted with active vibration control (MFC actuator), it was found that in all cases, the vibration damping of the analysed system was much higher at its resonant frequency. Nevertheless, due to the experimental results, it could be concluded that active and passive vibration control systems were efficient for thin-walled composite beam vibration amplitude control. Methodology for thin-walled composite beam vibration control analysis was developed and presented in the article.

Modeling, analysis, and control of MFC sandwiched laminate panel flutter with general layups and arbitrary boundary conditions

In this paper, a new solution approach based on Lagrange multipliers is developed for aeroelastic panel flutter analysis of rectangular composite plates sandwiched by two Macro Fiber Composites (MFCs). The smart panel has general stacking sequences and subjected to the elastic edge restraints. By utilizing the assumed mode technique, the displacements and electric potentials are expanded using formerly determined mode shapes. Afterward, the potential and kinetic energies of the problem are achieved and by employing the Lagrange equation, the discretized equations of the motion are obtained. The supersonic aerodynamic load is modeled through the well-known piston theory and included within the equations by means of the non-conservative force term of the Lagrange equation. Deriving the equations is more simplified thanks to the orthogonality of the Legendre polynomials. Finally, the input voltage of the MFC actuator is determined through the proportional or velocity feedback control algorithms based on the sensor output. The capability and credibility of the proposed approach are confirmed by comparing the results with those achieved by the FEM. The method is used to investigate the effects of MFCs orientations on the panel flutter boundaries of smart plates.

An Experimental Study on Macro Piezoceramic Fiber Composites for Energy Harvesting

During the last decades, composite materials are being widely used in a variety of applications. Recently, a type of composite materials with piezoelectric fibers has been introduced for energy harvesting. This study presents an experimental study about composite materials with Piezoceramic fibers for energy harvesting. For this purpose, Macro Fiber Composite (MFC) layers were attached to the surface of metal substrates to form a unimorph harvester. In addition, to investigate the effect of substrate geometrical imperfection on output power, unimorph harvester with notched corners are studied. The output voltage and power were measured during different base excitations. Voltage frequency spectrum and output power as a function of load resistance are analyzed. Results show that the power density for the MFC harvester is 10.37 [μW/cm3.g2] when vibrating on its fundamental natural frequency with current of 50 [μA], which are relatively higher than previous studies.

Effects of vibrating and deformed trailing edge of a morphing supercritical airfoil in transonic regime by numerical simulation at high Reynolds number

This article examines the aerodynamic performance increase of an Airbus A320 aerofoil thanks to morphing of the near-trailing-edge region in transonic regime corresponding to cruise conditions. The study has been carried out by numerical simulation at Reynolds number Re=2.06×106 and Mach number of 0.78, by using the NSMB code (Navier–Stokes MultiBlock) including adapted turbulence modelling approaches sensitised in capturing coherent structures development. It has been shown that transonic buffet occurs at angle of incidence 1.8° and in a more pronounced way at angle of 5°. The interactions among the shock-boundary layer area, the shear layers vortices and those of the near wake have been analysed by spectral analysis and streakline dynamics. Strong feedback effects have been shown from the near trailing-edge region towards the SWBLI (Shock Wave Boundary Layer Interaction) up to the upstream of the shock area. By taking benefit from these feedback effects, it has been obtained that morphing applied as a slight upwards deflection of the near-trailing-edge region by 2° is able to practically attenuate the buffet instability and to increase lift-to-drag ratio by 10.4 percent. The trailing-edge’s area vibration at low amplitudes simulating the motion of piezo-patches of MFC type (Macro-Fibre Composites) applied experimentally in the context of the H2020 European research project www.smartwing.org/SMS/EU) has shown a lock-in effect of the buffet’s frequency. Therefore, a conditioning of the shock’s motion by means of these actuations can be reached, although a relative increase of the rms of the aerodynamic forces is produced in this case. The study of a combined upwards slight deflection and of trailing-edge area vibrations allowed obtaining decrease of drag and increase of lift-to-drag ratio with simultaneous decrease of rms. These effects have been studied for a wide frequency range from 200 to 500 Hz.

Modelling and Laboratory Tests of the Temperature Influence on the Efficiency of the Energy Harvesting System Based on MFC Piezoelectric Transducers.

Macro Fibre Composites (MFC) are very effective piezoelectric transducers that, among others, can be used as elements of energy harvesting systems. The possibility to generate electric energy, for example, from mechanical vibrations in order to power electrical elements that could not be powered in another way (using wires or batteries) is a great solution. However, such a kind of systems has to be designed by considering all phenomena that could occur during the exploitation of the system. One of those phenomena is the temperature fluctuation during the device operation. In the presented research work, a mathematical model of the energy harvesting system based on MFC transducers is proposed. The mathematical model was validated by laboratory tests conducted on a laboratory stand equipped with a universal mechanical testing machine (Instron Electropuls 10000) and a thermal chamber. During the tests, the samples were subjected to cyclic excitation simulating the operation of the system in various environmental conditions by forcing changes in the system operation temperature with the constant conditions of its excitation.

Improved analytical homogenization of the piezoelectric macro-fiber composite: active layer embedded among passive layers

Predicting the effective electromechanical properties for piezoelectric fiber composite patches is crucial for analysis of smart structures equipped with such patches. In particular, analytical homogenization models are attractive but are limited by the complexity of the microstructure and the multiphysics involved. The macro-fiber composite (MFC) has emerged as the most popular piezoelectric fiber composite. But typical reports of its effective properties provide layerwise homogenization with low-order mechanical plate theories. This approach discards most of the out-of-plane properties and may introduce significant error from the assumptions about the plate kinematics. Moreover, the effective permittivities of the transducer are not available analytically. In an attempt to overcome these limitations, a new analytical scheme for homogenizing all layers in the MFC patch is proposed. Based on the newly discovered mechanics of structure genome, we avoid all kinematical assumptions and obtain an exact analytical solution for a periodic, multi-layered, linear-piezoelectric material. In doing so, we prove that in any such multi-layered composite, the in-plane strains and the transverse stresses are equal in each layer and the in-plane electric fields and transverse electric displacement are constant between the electrodes. Using this knowledge, a hybrid rule of mixtures is developed to homogenize all the MFC layers to obtain the complete set of properties of the full MFC. In doing the new analytical framework can homogenize any layered piezoelectric medium. Finally, since we were able to avoid the plate-kinematics assumptions, we present studies on their effect on the properties they obtain. We find that the in-plane elastic properties are not affected but the transverse shear moduli are overpredicted from 100% to 300%. What is more, studies are presented on how using the ubiquitous plane-stress-like assumptions to homogenize the fiber layers causes an 8% underprediction of the lateral elastic modulus of the MFC.

Towards actuation improvement of low-profile piezo fibre composites by notched electrodes

The present contribution reports on a novel approach for enhanced piezoelectric patch transducers based on round piezoceramic fibres. Starting from a critical review of the well-known Active Fibre Composite (AFC) concerning electrical coupling between electrodes and ceramic fibres, a new electrode design is proposed. By introducing notches into the fibres perpendicular to their axis and filling these notches witch a conductor, a much better coupling is created. This leads to a significantly better alignment of the intrinsic dipoles over a wide volume of the fibres during poling and thus to much higher piezoelectric performance of the transducers. With the aid of a finite element analyses, design rules for optimization of notched electrodes as well as prediction of transducer behaviour have been derived. For verification of the approach, transducers with varying notch depths have been built and glued onto polystyrene beams attaining active cantilevers. The setup was used to measure free displacement and blocking force generated by the transducers in comparison to other existing patch transducers. An improvement of the piezoelectric actuation up to a factor of four is observed for free deflection and blocking force, significantly exceeding results from state-of-the-art patch transducers such as Macro Fiber Composites (MFC).

Suppressing high-order surface errors of an active carbon fiber reinforced composite reflector using two types of actuators

Active feedback control is a feasible approach for maintaining the desired shape of a reflector. An architecture for an active reflector is presented in which both piezoelectric ceramic transducer (PZT) and macrofiber composite (MFC) actuators are introduced to reduce both the global and local (high-order) surface errors. An electromechanical finite element model with two types of actuators is developed using the Hamilton principle. An optimal shape controller is then developed to minimize the reflector surface error. Lower-order orthogonal Zernike polynomials are derived in a unit hexagon. The polynomials are considered to be the basic error modes of a reflector and are used to optimize the length of the PZT actuators. The arrangement of MFC actuators can be optimized in a single triangular component of the reflector because the deflections they induced are very local. An experiment is conducted to verify the performance of MFC actuators in a triangular component. The improvement in the control efficiency of the active reflector is demonstrated by two numerical examples.

A solution method based on Lagrange multipliers and Legendre polynomial series for free vibration analysis of laminated plates sandwiched by two MFC layers

In this paper, a new solution approach based on Lagrange multipliers is developed to investigate the free vibrations of rectangular composite plates equipped with piezoelectric layers such as Macro Fiber Composites (MFCs). The piezo-composite plate has general stacking sequences and is subjected to the elastic edge restraints. Using the first-order shear deformation theory (FSDT) and Hamilton’s principle, the boundary conditions of the problem are deduced. To solve the problem, the generalized displacements and electric potentials are expanded using the Legendre polynomial series as the base functions. Afterward, the strain and kinetic energies of the problem are achieved. Then, all the boundary conditions have been added to the energy expression by means of Lagrange multipliers to form the functional. This functional is extremised to give the natural frequencies and mode shapes of the problem through the generalized eigenvalue problem. Capability and credibility of the proposed approach are confirmed by comparing the results with those achieved by the experimental, finite element method (FEM) and 3D elasticity. The method finally is used to investigate the effects of MFCs orientations on the vibrational behavior of the smart plates.

Experimental Exploration of Macro-fiber Composite Morphing Wing

In this paper, a experimental model of morphing swept-wing with carbon fiber is designed and driven by Macro-Fiber Composites (MFC). Dynamic analysis of the wing structure is carried out. The maximum twist angle of the carbon fiber structure driven by the MFC in the experiment is 10.72°. External excitation can be applied to the wing structure for its dynamic analysis and the modal performance of the structure is analyzed.

Electromechanical modelling of a bistable plate with Macro Fiber Composites under nonlinear vibrations

Vibrational broadband energy harvesting has been the most focused application of bistable composite plates paired with piezoelectric materials due to their wide array of nonlinear responses at low frequencies. Various cross-well behaviors between the two potential wells allow large amplitudes and broadband characteristics favorable for generating ample power even away from resonance. With most past works being experimental, there are limitations in the available literature for validated model predictions of the electromechanical response resulting from cross-well dynamics under harmonic excitation. This paper presents the formulation, implementation, and experimental validation of the nonlinear analytical model for the rectangular piezoelectrically generated bistable laminate with a fixed center consisting of Macro Fiber Composites (MFC) in a cross-ply layup. The full range of nonlinear responses observed in tests are predicted by the simulated electromechanical equations of motion such as intermittency, limit cycle, chaotic, and subharmonic oscillations. These responses and the corresponding voltage and power outputs are investigated for a range of excitation parameters using both time and frequency domain analysis, and they show good agreement with experimental results.

Compliant structure under follower forces and any combined loading: Theoretical and experimental studies

A linear finite element and a nonlinear finite element solution scheme have been proposed to obtain the deflection of a compliant structure, modeled as a cantilever beam, under the action of a follower force acting at the end, in addition to any additional arbitrary loading. The developed techniques have been compared with a numerical technique available in literature, wherein, nonlinear Euler–Bernoulli beam theory is used in an iterative scheme. It was found that the results of the nonlinear finite element algorithm exactly match the solution from the available scheme; while on the other hand, the linear finite element gives fairly close results at a higher rate of convergence. Experiments are carried out to validate the two proposed solution techniques. Two example problems have been solved, which show the practical application of this numerical scheme, in the design of mechanisms actuated by smart materials like shape memory alloys (SMA) and macro fiber composites (MFC), in the process, obviating the limitations of the available techniques in solving such problems.

Motion planning and tracking control for coupled flexible beam structures

A systematic flatness-based motion planning approach for a structure consisting of coupled flexible bending beams is introduced. The beams are equipped with in-domain piezoelectric macro-fiber composite (MFC) actuators and are coupled by an elastic string, modeled as spring, which connects the tip masses of adjacent beams. This setup provides a challenging benchmark experiment to evaluate control concepts. Hamilton’s principle leads to the equations of motion involving spatially varying parameters due to the different material characteristics of the carrier structure and the attached MFC-actuators. The flat output is constructed by exploiting the spectral system representation and enables a differential parameterization of the system states and inputs. This parameterization transfers the motion planning problem into a trajectory assignment problem for the flat output. The resulting flatness-based feedforward control law is analyzed and evaluated at an experimental setup. To increase the performance and the robustness w.r.t. model uncertainties and external disturbances the flatness-based feedforward control is amended by a feedback controller with observer in the spirit of the two-degrees-of-freedom control approach.

Low Cost and Piezoelectric based Soft Wave Energy Harvester

Abstract:Wave energy converters have been developed and commercialized in past decades; they have now faced numerous challenges of large volume sizes, environmental hazards, and high costs of deployment, components and maintenance. To address these challenges and make a wave energy converter practically available for various applications at a reasonable cost, we have developed a soft wave energy harvester that integrated low-cost soft material structures and piezoelectric-based Macro Fiber Composite (MFC). This integrated soft wave energy converter has a straightforward fabrication process and structure that can harvest energy from a broad working frequency of waves. The innovative design combined low-cost and commercially available materials and formed a harvester that addressed the aforementioned problems of commercially available harvesters. Additionally, the low cost and simple design are scalable for large energy conversion in the future. The energy conversion performance of the proposed platform has been investigated in a wave flume with low-frequency incoming waves (<2Hz). The soft energy conversion platform is hung like a curtain and produces a maximum 487nW. Also, the low cost and durable encapsulation can protect the electrical properties of MFCs and circuits, and a single harvester can last through all experiment steps without any degradation, which was more than 170 hours.