Macro Fiber Composite Research Articles

Continuous electric field modeling of Macro-Fiber Composites for actuation and energy harvesting

This paper presents a new low-order electric field model for Macro-Fiber Composite devices with interdigitated electrodes. Specifically, the paper proposes a continuous electric field model, where the differential form of Gauss's law is used to obtain spatial terms of the electric field, and the integral form of Gauss's law is used to obtain temporal term of the electric field. By neglecting three-dimensional effects, the method of matched asymptotic expansion is employed to obtain the electric field between two pairs of interdigitated electrodes under quasi-electrostatic conditions. By averaging the solution along with the thickness of piezoceramic fibers and expanding it to the device's entire geometry by Fourier series, the low-order model of the electric field between the interdigitated electrodes is obtained. The matched asymptotic expansion and the low-order model agree well with finite element results. Generalized Hamilton's principle is employed to obtain the coupled electromechanical equations of motion for a beam with the Macro-Fiber Composite device. The Euler-Bernoulli assumptions are used to approximate strain distribution. Under current assumptions, equivalent capacitance and electromechanical coupling terms are obtained without using discontinuous functions (e.g., Heaviside or piecewise functions) for electric field terms. The equivalent capacitance is within 2% of the values reported by the manufacturer. Frequency response functions are obtained for the output voltage, tip displacement, and optimum working load of the energy harvester, and the current and the tip displacement for the actuator by assumed modes solution for a cantilever beam. It is shown that the actuator's current is related to the optimum working load of the energy harvester by Ohm's law. In the limited case, the proposed continuous electric field model reduces to the constant electric field model. When the constant electric field model is compared to the continuous electric field model, it is shown that the constant electric field model overpredicts the equivalent capacitance and electromechanical coupling. The relative difference between the two models for equivalent capacitance is around 41%, and for electromechanical coupling is around 22%. These relative differences are in agreement with the empirical correction factors defined in the earlier constant field models.

Motion planning of a fish-like piezoelectric actuated robot using model-based predictive control

This work proposes a novel methodology for planning the motion of fish-like soft robots actuated by macro-fiber composite (MFC) pairs. These structures should mimic oscillatory and undulation movements, which can be accomplished if the amplitude of the tail motion is larger than that of the head motion. Design strategies, such as the use of concentrated and distributed masses, are addressed to mimic fish-like motion since they guarantee suitable mode shapes for the structure. The motion planning proposal explores a model-based predictive control (MPC) strategy for deriving the input signals for the MFC actuators. This model-based control strategy requires the use of reasonably small-sized models. This is accomplished by extracting modal state-space models based on the free–free Euler–Bernoulli beam theory considering the electro-mechanical coupling of the MFC actuator pairs. Numerical results demonstrate the capability of the proposal for deriving bounded input signals that generate oscillatory and undulation movements even in the presence of disturbances. This general approach can be further extended for other applications.

Ultra-magnetic field sensitive magnetoelectric composite with sub-pT detection limit at low frequency enabled by flash photon annealing

An ultra-sensitive magnetic field detector is demonstrated in a bilayer magnetoelectric (ME) composite structure employing a flash photon annealing (FPA) treated amorphous Metglas (FeBSi) alloy and piezoelectric single crystal macro fiber composites (SFC). A millisecond FPA annealing approach altered the magnetostrictive and mechanical properties of Metglas by annealing at a high temperature without inducing severe embrittlement. The ME composite (MEC) fabricated with FPA-treated Metglas (FPA-MEC) exhibited an enhanced ME coupling coefficient (at a resonance condition ~47% and at an off-resonance condition ~52%) relative to that of untreated Metglas based ME composite (pristine MEC), owing to the improved magnetic flux concentration/piezo-magnetic coefficient and reduced resonance loss in Metglas. This led to the realization of an ultra-sensitive magnetic field sensor with a direct detection limit of 0.5 pT [1 order improved performance compared to the pristine MEC (sensing limit of 5 pT)] at an extremely low resonance frequency condition (<100 Hz). The obtained results demonstrate a feasible way to design magnetic sensors for detecting bio-magnetic and extremely low-frequency (ELF) magnetic fields under ambient conditions.

Lifetime estimation of single crystal macro-fiber composite-based piezoelectric energy harvesters using accelerated life testing

Piezoelectric energy harvesters (PEHs) based on single crystal macro fiber composites (SFCs) have been widely utilized in vibration sensing, energy conversion, and power portable/wearable electronic devices. Despite growing attention to improve the output power of PEHs, few dedicated studies on reliability, especially on estimation of the usable lifetime of PEHs, have been reported. In this paper, an accelerated life test is applied to d32-type hard SFC-based PEHs to efficiently estimate usable lifetime in a short period of time. High temperature is used as environmental stress to accelerate the life of the PEHs, and time-to-failures are collected according to the criterion of a 10% drop in output power at 45, 55, and 70 °C under a mechanical vibration of 4.9 m/s2. The statistical failures distribution is analyzed using the Arrhenius-Weibull model with an activation energy (Ea) of 2.36 eV and a shape parameter (β) of 1.44. Accordingly, the average lifetime to failure of the PEHs in normal use (i.e., at room temperature) is determined as 4.3 × 109 vibration cycles. In addition, each failure mode is assessed to identify vulnerable points that reduce the lifespan of SFC-based PEHs. This study provides insight for evaluating and enhancing the reliability of PEHs as a basis for future practical application.

Leveraging a data-driven approach to simulate and experimentally validate a MIMO multiphysics vibroacoustic system

The objective of the present work is to evaluate the performance of a data-driven approach to simulate a multiphysics vibroacoustic field. Of particular interest is the complex propagation of anechoic waves in a finite 1D-structure submerged in water. Experimental data from an underwater beam actuated by two macro-fiber composites (MFCs) serves as the experimental framework for the data-driven model. Next, the Vector-Fitting (VF) algorithm estimates a state-space model of the multiphysics dynamics with voltage signals to the two MFCs as inputs, and the structural and the acoustic responses as the outputs. The multi-input–multi-output data-driven model is then used to determine the parameters that result in the optimal anechoic wave, a process that was carried out previously by experimental iterations. The optimal time-domain simulations are validated with experimental results.

Numerical analysis of Lamb waves propagating through impact damage in a skin-stringer structure composed of interlaminar-toughened CFRP

Many structural health monitoring systems are being developed to detect the impact damages in carbon fiber reinforced plastic (CFRP) structures, which are widely adopted in the aviation industry. In this study, a refined finite element model is established to simulate a Lamb wave propagating through impact damage in a CFRP skin-stringer structure. The accurate stiffness constants are determined for toughened CFRP laminates, which include the resin layers. The impact damage of toughened CFRP laminates is modeled as a truncated-cone-shaped region in which the rigidity is homogeneously reduced. Furthermore, the directive generation of the Lamb wave through a macro fiber composite (MFC) actuator is incorporated in the model. Simulations are performed for several configurations of the MFC and impact damage. The observed tendency of the delay in the arrival time of the lowest antisymmetric Lamb wave mode is noted to be consistent with the experimental results. The proposed model can facilitate the determination of the optimized configuration of MFCs in CFRP structures.

Low-Computational-Cost Technique for Modeling Macro Fiber Composite Piezoelectric Actuators Using Finite Element Method.

The large number of interdigitated electrodes (IDEs) in a macro fiber composite (MFC) piezoelectric actuator dictates using a very fine finite element (FE) mesh that requires extremely large computational costs, especially with a large number of actuators. The situation becomes infeasible if repeated finite element simulations are required, as in control tasks. In this paper, an efficient technique is proposed for modeling MFC using a finite element method. The proposed technique replaces the MFC actuator with an equivalent simple monolithic piezoceramic actuator using two electrodes only, which dramatically reduces the computational costs. The proposed technique was proven theoretically since it generates the same electric field, strain, and displacement as the physical MFC. Then, it was validated with the detailed FE model using the actual number of IDEs, as well as with experimental tests using triaxial rosette strain gauges. The computational costs for the simplified model compared with the detailed model were dramatically reduced by about 74% for memory usage, 99% for result file size, and 98.6% for computational time. Furthermore, the experimental results successfully verified the proposed technique with good consistency. To show the effectiveness of the proposed technique, it was used to simulate a morphing wing covered almost entirely by MFCs with low computational cost.

Vibration damping of aircraft propeller blades using shunted piezoelectric transducers

Gas turbine engine blades experience vibrations due to the flow disturbances, these vibrations are critical to the engine durability and performance. Piezoelectric transducers (sensors and actuators) have been used for engine blade vibrations damping either through a passive or active vibration control. The propeller blades are part of turboprop engine and considered as one of the main source of turboprop engine vibrations. Piezoelectric blade damping ideas have been studied by other researchers for fan blades and compressor blades. In this research a vibration damping procedure using piezoelectric transducers applied to an unmanned aerial vehicle (UAV) composite propeller. Experimental investigation introduces an approach for the propeller vibration damping using piezoelectric transducers in conjunction with appropriate shunt circuit. Three thin piezoelectric transducers macro fiber composite (MFC) type PZT-5A are surface-mounted on the propeller, one at each blade. These transducers are placed at locations of high modal strain areas for the propeller first mode at each blade, where these locations are identified by finite element numerical simulation. Electronic resonance shunt circuit, resistor-inductor-capacitor type, for the piezoelectric transducers is designed and experimentally developed such that effective vibration suppression of the propeller is achieved. The experimental and numerical investigations in this research illustrate that piezoelectric transducers with appropriate shunt circuit reduces the aircraft propeller vibrations.

A Micro-Power Generator Based on Two Piezoelectric MFC Films

In order to realize the collection of micro or small vibration energy, a micro-power generator based on two piezoelectric Macro Fiber Composite (MFC) films is proposed. The piezoelectric generator consists of a double piezoelectric MFCs type vibrator and a displacement amplifying mechanism, which can achieve the output of high energy density. The design process of this kind of piezoelectric generator is presented. Based on LabVIEW platform and NI Data Acquisition (DAQ) card, the output voltage acquisition system of the generator is built, and the output voltage and power are collected and calculated. Experimental results show that the maximum output power is 6.2 mW under transient excitation. Under continuous excitation with a load resistance of 10 kΩ and an excitation frequency of 26 Hz, the maximum output of the generator is up to 11.9 mW. The research results lay a foundation for the application of the proposed micro-power piezoelectric generator.

Time-delayed positive position feedback control of nonlinear vibrations of continuous rotating shafts

The objective of the present study is to suppress the large amplitudes of a continuous spinning shaft under an active vibration control. For this purpose, the Positive Position Feedback (PPF) control with time-delays are applied to the system via Macro-Fiber-Composite (MFC) sensors and actuators. The nonlinear dynamics of the system is explored analytically utilizing the perturbation method in the primary and one-to-one internal resonances. The steady state solutions of the system and controller in the Cartesian and polar forms are obtained. The effects of the controller gains and time delays on the stability and loci of bifurcations of the system are investigated. The controller shows its feasibility in controlling the system vibrations. Also, it is demonstrated that by increasing the controller gain coefficients the minimum amplitude regions of the system are increased. Furthermore, the safe boundary of the loop delays is studied. The results of the analytical approach are in good agreement with the numerical results of the original system of equations.

Trout-like multifunctional piezoelectric robotic fish and energy harvester

This work presents our experimental studies on a trout-inspired multifunctional robotic fish as an underwater swimmer and energy harvester. Fiber-based flexible piezoelectric composites with interdigitated electrodes, specifically macro-fiber composite (MFC) structures, strike a balance between the deformation and actuation force capabilities to generate hydrodynamic propulsion without requiring additional mechanisms for motion amplification. A pair of MFC laminates bracketing a passive fin functions like artificial muscle when driven out of phase to expand and contract on each side to create bending. The trout-like robotic fish design explored in this work was tested for both unconstrained swimming in a quiescent water tank and under imposed flow in a water tunnel to estimate the maximum swimming speed, which exceeded 0.25 m s−1, i.e., 0.8 body lengths per second. Hydrodynamic thrust characterization was also performed in a quiescent water setting, revealing that the fin can easily produce tens of mN of thrust, similar to its biological counterpart for comparable swimming speeds. Overall, the prototype presented here generates thrust levels higher than other smart material-based concepts (such as soft polymeric material-based actuators which provide large deformation but low force), while offering simple design, geometric scalability, and silent operation unlike motor-based robotic fish (which often use bulky actuators and complex mechanisms). Additionally, energy harvesting experiments were performed to convert flow-induced vibrations in the wake of a cylindrical bluff body (for different diameters) in a water tunnel. The shed vortex frequency range for a set of bluff body diameters covered the first vibration mode of the tail, yielding an average electrical power of 120 μW at resonance for a flow speed around 0.3 m s−1 and a bluff body diameter of 28.6 mm. Such low-power electricity can find applications to power small sensors of the robotic fish in scenarios such as ecological monitoring, among others.

Magnetic actuation of switchable bistable structures: a numerical study

Bistable laminates have posed a significant research interest in the recent past owing to their potential applications in morphing and energy harvesting. An important aspect of research has been their snapthrough analysis, wherein the use of solid state actuators like shape memory alloys (SMAs) and macro-fiber composites (MFCs) has been prevalent. These actuators however, interfere with the structural response of the laminate altering its bistability and snapthrough characteristics. Recently, reversible snapthrough was demonstrated in 3D printed thermoplastic filaments composed of PLA with finely ground iron particles embedded. Remote actuation was achieved by means of permanent magnets providing the necessary snapthrough loads. In this manuscript, a numerical model has been developed based on a Rayleigh-Ritz minimization scheme, to predict the equilibrium states and the snapthrough loads. The means of snapthrough is the interaction between the ferromagnetic layers and the nonlinear magnetic field generated by a solenoid, which has been modeled using Biot-Savart’s law. The developed numerical model has been validated against finite element simulations in ABAQUS®, wherein the magnetoelastic interactions have been modeled as body forces using the DLOAD subroutine. This manuscript details one of the preliminary efforts in modeling of the remote snapthrough of switchable multistable structures and can provide valuable insights into the design of such non-contact actuation systems.

Numerical study on gust energy harvesting with an efficient modal based fluid-structure interaction method

Gust disturbance during flight causes elastic vibrations and rigid body motions of an aircraft. A macro fiber composite (MFC)-based energy harvester can be used to obtain energy from gust-induced vibrations. This paper aims to present an efficient fluid-structure interaction (FSI) method for fast and accurate calculation of gust response and harvested energy of a fly wing aircraft half model. In this method, computational fluid dynamics (CFD) and computational structural dynamics (CSD) are coupled by embedding a modal-superposition-based structural solver into the CFD solver. Parallel data exchange and interpolation strategy on the fluid-structure interface is introduced to improve the computational efficiency. MFC harvester is modeled by a piezoelectric beam model, and the displacement of the piezoelectric beam is obtained by interpolation from FSI results. The numerical results of gust response and MFC voltage output are in good accordance with wind tunnel test results, while the calculation time is only 1/8 of the time consuming of a direct CFD/CSD coupling method. The influences of gust frequency, gust amplitude, freestream velocity, and the number of retained modes on energy harvesting are investigated. Results indicate that the accuracy of the calculation can be guaranteed by the superposition of several retained modes, and the additional suction provided by leading-edge vortices causes a nonlinear increase in energy harvesting near the stalling angle of attack.

Impact of Series and Parallel Connection of Macro Fiber Composite Patches in Piezoelectric Harvester on Energy Storage

A beam containing a piezoelectric layer or layers is used for piezoelectric harvesting from various processes. The structure of the beam is made by gluing the piezoelectric material on one side (unimorph) or both sides (bimorph) of a carrying substrate. Two piezoelectric layers, glued on both sides of the substrate, may be electrically parallel or series connected. This paper presents an experimental analysis of the impact of parallel and series connections of two Macro Fiber Composite (MFC) MFC patches in a bimorph on the charging of a capacitor. In experiments, the effective charging process of the capacitor was obtained both for parallel and series connection of two MFC patches. The bimorph with a parallel connection generated a larger capacitor charging power than the bimorph with a series connection in the range of voltage across the capacitor from 1 to 18 V. However, the bimorph with a series connection was more effective than a parallel connection for voltage across the charged capacitor from 18 to 20 V. The maximum capacitor charging power generated by the bimorph, in which two MFC patches were parallel connected, was 1.8 times larger than that generated by the bimorph with a series connection and was 3.3 times larger than that generated by a unimorph with one MFC patch. The impact of level of voltage across the capacitor on its discharging process has a significant meaning for the ratio of maximum power between bimorphs and between the bimorph and unimorph.

Vibroacoustical Performance Analysis of a Rigid Device Casing with Piezoelectric Shunt Damping.

Noise and vibration are common issues that may have a negative impact on human’s’ health. To minimize their consequences, several vibroacoustical methods may be employed. One well-known method is Piezoelectric Shunt Damping (PSD). Over the years, many approaches have been investigated, from passive, state switching circuits to active pulse-switching. In this paper, the authors propose three PSD implementations—passive Synchronized Switch Damping on Inductor (SSDI), semi-active SSDI and active Synchronized Switch Damping on Voltage source (SSDV)—for a single-panel structure mounted on a rigid-frame casing. The nine Macro Fiber Composite (MFC) elements were mounted on the plate based on preliminary simulations in FreeFEM. Then, the theoretical results were validated by an identification experiment. The main research is concentrated on the Sound Pressure Level (SPL) and structural vibrations reduction for selected frequencies. The active method provided the highest reduction of vibration—up to 5.5 dB for maximal possible loudspeaker level without overdrive and up to 7.5 dB for lower excitation levels.

Bio-Inspired Morphing Tail for Flapping-Wings Aerial Robots Using Macro Fiber Composites

The aim of this work is to present the development of a bio-inspired approach for a robotic tail using Macro Fiber Composites (MFC) as actuators. The use of this technology will allow achieving closer to the nature approach of the tail, aiming to mimic a bird tail behavior. The tail will change its shape, performing morphing, providing a new type of actuation methodology in flapping control systems. The work is intended as a first step for demonstrating the potential of these technologies for being applied in other parts of the aerials robotics systems. When compared with traditional actuation approaches, one key advantage that is given by the use of MFC is their ability to adapt to different flight conditions via geometric tailoring, imitating what birds do in nature. Theoretical explanations, design, and experimental validation of the developed concept using different methodologies will be presented in this paper.

Piezoelectric‐Driven Self‐Sensing Leaf‐Mimic Actuator Enabled by Integration of a Self‐Healing Dielectric Elastomer and a Piezoelectric Composite

Soft robots and devices exploit highly deformable materials that are capable of changes in shape to allow conformable physical contact for controlled manipulation. While soft robots are resilient to mechanical impact, they are susceptible to mechanical damage, such as tears and punctures. The development of self‐healing materials and actuators continues to attract increasing interest, in particular, with respect to integrating self‐healing polymers to create bioinspired soft self‐healing devices. Herein, a novel piezoelectric‐driven self‐healing leaf‐motion mimic actuator is designed by combining a thermoplastic methyl thioglycolate–modified styrene–butadiene–styrene (MGSBS) elastomer with a piezoelectric macrofiber composite (MFC) for self‐sensing applications. This article is the first demonstration of a self‐sensing and self‐healing actuator‐sensor system, which is driven by a piezoelectric actuator and can mimic leaf motion. The leaf‐motion actuator combines built‐in dynamic sensing and room‐temperature self‐healing capabilities to restore macroscale cutting damage with an intrinsically high bandwidth of up to 10 kHz. The feasibility and potential of the new actuator for use in complex soft autonomous systems are demonstrated. These new results help to address the emerging influence of self‐healing soft actuators and the challenges of sensing, actuation, and damage resistance in soft robotics.

Conceptual design and numerical studies of active flow control aerofoil based on shape-memory alloy and macro fibre composites

ABSTRACTActive flow control for aerofoils has been proven to be an effective way to improve the aerodynamic performance of aircraft. A conceptual hybrid design with surfaces embedded with Shape-Memory Alloy (SMA) and trailing Macro Fibre Composites (MFC) is proposed to implement active flow control for aerofoils. A Computational Fluid Dynamics (CFD) model has been built to explore the feasibility and potential performance of the proposed conceptual hybrid design. Accordingly, numerical analysis is carried out to investigate the unsteady flow characteristics by dynamic morphing rather than using classical static simulations and complicated coupling. The results show that camber growth by SMA action could cause an evident rise of Cl and Cd in the take-off/landing phases when the Angle-of-Attack (AoA) is less than 10°. The transient tail vibration behaviour in the cruise period when using MFC actuators is studied over wide ranges of frequency, AoA and vibration amplitude. The buffet frequency is locked in by the vibration frequency, and a decrease of 1.66–2.32% in Cd can be achieved by using a proper vibration frequency and amplitude.

Snap-through of bistable variable stiffness laminates using MFC actuators

Unsymmetric composite laminates exhibit two or more stable equilibrium shapes with opposite curvature as a result of residual thermal stresses induced during the curing process. Surface bonded Macro Fibre Composite (MFC) actuators are generally employed to trigger snap-through between one stable shape to another by applying external voltages. However, these actuators require high actuation voltage input to change from one stable shape to another, especially when used in morphing applications. If the snap-through voltage is too high, morphing becomes infeasible or may require several actuators, which is contrary to the weight requirements. Variable Stiffness (VS) laminates provide the possibility for an enlarged design space with the possibility to tailor stiffness parameters, leading to lower snap-through loads and consequently reducing the size of the actuators.On the prediction of snap-through voltages, the existing semi-analytical models have shown reasonably high discrepancies between numerical and experimental results. An improved analytical model is proposed in this study to predict the snap-through of bistable VS laminates with MFC actuators. In the improved model, the equations resulting from the compatibility and the in-plane equilibrium are described equivalent to a standard plane elasticity problem which can be solved using a standard finite element (FE) approach. In addition, the total potential energy is written in terms of curvatures. The improved semi-analytical results are compared with a full geometrically nonlinear FE calculation.

Optimal strain-deflection analyses of a wedge edged beam for enhanced vibration energy scavenging in patch-like harvester

Recently, non-prismatic beams have been considered as perfect substitutes to replace uniform cantilever beam structures in harvester design. This is due to their tendencies to provide uniform strain distribution, which enhances piezoelectric (PZT) charge generation when coupled with the beams. As the voltage produced by the PZT depends largely on the geometrical shape of the substrate, thus there is need for formulations to analyze the behavior of the shim prior to practical implementation. In this paper, analytical and finite element models were developed to study deflection and strain distribution of a non-prismatic beam termed, wedge edged cantilever (WEC) for patch-like harvester application. The analyses offer possibility for maximum utilization of strain location along the beam span for efficient harvester design. Vibration energy harvesting characteristics of the WEC beam with partially covered PZT material forming three configurations namely: Config1, Config2 and Config3 were studied. Both numerical and experimental results show that Confg3 with macro fiber composite (MFC) as the PZT material covering the determined optimal strain position yielded 2 to 3 times more peak output voltage than Config1 and Config2 with the MFC bonded at non-optimal positions.