Macro Fiber Research Articles

A cost-efficient UHPC incorporated with coarse aggregates and macro fibres recycled from waste GFRP

High production cost is a key impediment to the broader applications of UHPC materials. In the present study, a concept has been therefore proposed on jointly incorporating coarse aggregates and macro fibres recycled from waste GFRP in the UHPC system to produce a cost-efficient UHPC. The coarse aggregates were respectively incorporated into UHPC using the modified Andreasen and Andreasen model (MAAM) leading to the cement added in per m3 UHPC being as low as 668 kg. Compression and flexural tests were first carried out to examine the effects of incorporating both coarse aggregates and macro fibres on the properties of such a UHPC. The tensile stress-strain curves were then obtained from the data results of bending tests through a twice inverse analysis. A cost analysis was performed as well to quantitatively compare the production costs of different UHPCs, justifying the proposed concept. The test results and discussion revealed that the UHPC incorporated coarse aggregates have a compressive strength of about 150 MPa, and the presence of macro fibres of 6% in volume results in about 20% decrease in the compressive strength of UHPC, but significantly enhances the flexural properties of UHPC, including peak strength, residual strength, and toughness. The production cost of the UHPC mixture has been lowered to about 1700 CNY/m³ by jointly incorporating coarse aggregates and macro fibres. The maximum value of the efficiency index (E) is achieved when utilizing aggregate with a maximum particle size of 9.5 mm and 6% macro fibre.

Fabrication and property of flexible macro fiber composites for vibration-based energy harvesting

Fabrication and property of flexible macro fiber composites for vibration-based energy harvesting

Resonant frequency tuning of a novel piezoelectric vibration energy harvester (PVEH)

It is imperative to provide autonomous power supplies for the sensor nodes in structural health monitoring. Piezoelectric vibration energy harvesters (PVEH) can generate power to meet this. Here, studies on a novel PVEH design integrating ionic polymer metal composites (IPMC), for electrical tuning of resonant frequency of the harvester have been discussed. The device for which a patent is pending, has two sections. Macro fiber composite (MFC) is bonded on the root section and the extension beam is impacted by IPMC. Net power output was achieved with varying conditions. This article also discusses theoretical analysis of results and next-generation devices.

Underwater dynamic hysteresis modeling and feedforward control of flexible caudal fin actuated by macro fiber composites

Underwater bionic robotics and vehicles that use flexible structures as power sources have attracted considerable attention. Thus, the underwater dynamic behaviors of the flexible structure of a variable cross-section actuated by smart actuators must be further investigated. In this study, underwater dynamic hysteresis modeling and feedforward compensation of a flexible caudal fin driven by macro fiber composites (MFC) at different frequencies were investigated. The MFC-actuated flexible caudal fin is considered a Euler–Bernoulli beam. A revised hydrodynamic function governed by the thickness of the viscous layer and the gap-to-width ratio of the cross-section was developed. Then, a characteristic-frequency-dependent extended transform function model is proposed for the hydrodynamic response of a non-uniform beam. An asymmetric hysteresis model is presented to characterize the rate-independent hysteresis behavior of the MFC actuators. Further, the underwater dynamic equation of the MFC-actuated caudal fin with hysteresis is obtained by connecting the two established models in series. Experiments demonstrate the dynamic behavior between the underwater responses of the caudal fin and the input voltages have an ellipse-like shape and vary in shape and size with oscillating frequency. The ellipse-like dynamic hysteresis loop first grows, reaching its maximum at the resonant frequency, and then decreases, because of the frequency-dependent dynamic behavior. Meanwhile, a phase shift of approximately 90°between the input voltage and underwater dynamic response was observed at the resonant state. Furthermore, the experimental results demonstrate that the proposed model can describe the nonlinear underwater dynamic hysteresis behavior of the proposed caudal fin at different frequencies. The trajectory tracking performances are remarkably improved over a broad frequency range with the proposed compensator. Consequently, the effectiveness of the proposed dynamic model and compensation method was demonstrated. These results are helpful for robotic fish or autonomous underwater vehicles propelled by oscillating foils actuated by smart actuators, including MFC.

Buckling Analysis of Composite Piezoelectric Cylindrical Shells with Graphene Skin Subjected to the Axial Load

The buckling of new three‐phase composite shells, which include the base material combined with macro fiber composite and reinforced with graphene (MFC‐GP), is investigated in this article. The bifurcation condition of the buckling is obtained by implementing the first‐order shell theory and wave propagation theory in conjunction with the principle of minimum potential energy. The buckling analysis is transformed into a bifurcation problem of equations. Parametric study is conducted to investigate the effects of the GP volume fraction, length, neutral surface radius, and thickness on the critical buckling loads and critical buckling modes. Furthermore, the influences of voltage and temperature change on the critical buckling displacements are explored. Reliable theoretical support for the design and manufacture of the MFC‐GP structures is provided in the results.

Active vibration control and experimental investigations of the composite parabolic shell with variable cross-section under thermal load

The accurate dynamic equation of the parabolic shell with variable cross-section is developed in this paper. The geometric nonlinearity is used to amend the expression of the strain. Considering the large overall motion and solar heat flux, the flexible deformations and freedom vibrations of the parabolic shell are analyzed by the proposed method. Meanwhile, the strain rate feedback control law with piezoelectric layer is presented to improve the dynamic performance of the parabolic shell during the motion process. The experiments with parabolic shell are studied to verify the correctness of the proposed method and control strategy. It is found that the results obtained by the proposed method agree very well with the experiments. Furthermore, the numerical results show that high-frequency vibration and flexible deformation can be effectively improved by the Macro Fiber Composite (MFC). And the optimized controller gain coefficient is also discussed at the end of this paper. This paper demonstrates the importance of the piezoelectric layer for the improvement of the dynamic response of flexible parts.

Macro Fiber Composite-Actuated Soft Robotic Fish: A Gray Box Model-Predictive Motion Planning Strategy Under Limited Actuation.

This work experimentally investigates a model-predictive motion planning strategy to impose oscillatory and undulation movements in a macro fiber composite (MFC)-actuated robotic fish. Most of the results in this field exploit sinusoidal input signals at the resonance frequency, which reduces the device's maneuverability. Differently, this work uses body/caudal fin locomotion patterns as references in a motion planning strategy formulated as a model-based predictive control (MPC) scheme. This open-loop scheme requires the modeling of the device, which is accomplished by deriving a gray box state-space model using experimental modal data. This state-space model considers the electromechanical coupling of the actuators. Based on the references and the model, the MPC scheme derives the input signals for the MFC actuators. An experimental campaign is carried out to verify two references for mimicking the locomotion patterns of a fish under limited actuation. The experimental results confirm the motion planning scheme's capability to impose oscillatory and undulation movements.

Hydrodynamic effect and Fluid-Structure coupled vibration of underwater flexible caudal fin actuated by Macro fiber composites

Underwater bionic robotics or vehicles using oscillating flexible structures as power sources are attracting considerable attention. In this study, the hydrodynamic effect and fluid–structure coupled vibration of a flexible caudal fin actuated by macro fiber composites(MFC) are investigated. A fluid–structure coupled dynamic equation of the MFC-actuated caudal fin with a variable cross-section is established, and both the internal moment generated by the MFC and the complex-valued hydrodynamic forces are considered. Distributions and evolutions of the flow velocity and pressure in the vicinity of the oscillating caudal fin with different parameters are visualized through comprehensive parametric CFD simulations. Simulation results show that the presence of the gap introduces significant flow reshaping effects to the flow distribution and hydrodynamics. Distributions of the flow velocities and concentrated pressure regions depend highly on the gap width of the forked caudal fin. Then, a revised hydrodynamic function depending on three nondimensional governing parameters is developed, this is, the characteristic oscillating frequency, the width ratio, and the gap-to-width ratio. Formulas for the real and -imaginary parts of the complex-valued hydrodynamic function are developed respectively through the comprehensive CFD framework. Theoretical and experimental results show that the revised hydrodynamic function and developed model are capable of estimating the hydrodynamic effect and underwater dynamic response of the MFC-actuated caudal fin. Compared with the classical hydrodynamic function for the rectangular beam, the expression for the beam overestimates the added mass effect exerted on the caudal fin, and underestimates the hydrodynamic damping effect, thus leading to a smaller estimated resonant frequency and bandwidth, but a higher predicted response peak. These findings are useful for the robotic fish or autonomous underwater vehicles which are propelled by oscillating foils actuated by smart actuators.

Dynamic analysis of graphene-reinforced sandwich plates with piezoelectric macro fiber composite face sheets

Graphene is considered as an ideal candidate for composite materials owing to the outstanding physical characteristics. However, existing higher-order shear deformation theories in the literature may meet severe challenges for the accurate prediction of natural frequencies of graphene-reinforced sandwich plates with piezoelectric macro fiber composite (MFC) face sheets. If transverse shear deformations cannot be described accurately, the dynamic behaviors of piezoelectric sandwich plates with graphene reinforcements will be significantly impacted by the large differences of material properties at interfaces of adjacent layers and electro-mechanical coupling characteristic. Thereby, a novel electro-mechanical coupling theory is to be proposed for the free vibration of graphene-reinforced sandwich plates with MFC face sheets. Based on the Reissner mixed variational theorem (RMVT), the precision of the interlaminar shear stresses including the electro-mechanical coupling effect can be improved. The modified interlaminar shear stress field is absorbed in the strain energy, which can enhance the accuracy of the free vibration response of piezoelectric sandwich plates. Additionally, the second-order derivatives of in-plane displacements have been eliminated from the interlaminar shear stress components, which can substantially simplify the finite element implementation. Thus, a simple C0-type finite element formulation is developed for the free vibration of piezoelectric sandwich plates with graphene reinforcements. The 3D elasticity solutions and the results obtained from other theories are used to evaluate the performance of the proposed theory. In comparison with the existing higher-order theories, the proposed theory can produce more accurate results. In addition, a comprehensive parametric study is conducted to explore the impacts of significant parameters on the free vibration behaviors of piezoelectric graphene-reinforced sandwich plates.

Repeatable self-healing of composite’s fatigue delamination

This paper investigates repeatable self-healing of composite laminates to mitigate fatigue delamination where a two-step healing mechanism is employed to heal the delamination cracks in a CFRP composite: (i) close the cracked surfaces by thermally activating dispersed shape memory polymer (SMP) filaments, and (ii) heal the closed crack by melting the thermoplastic healant (PCL) dispersed in the thermoset polymer matrix and allowing it to flow into the cracked region and solidify. Repetitive self-healing is carried out on double cantilever beam (DCB) specimens using macro fiber composite (MFC) actuators bonded to the test specimens, which generate the heat required to activate the thermoplastic healants to heal the delamination in the composite. Fatigue delamination growth rates were obtained for replicate specimens to extract statistically meaningful data on fatigue life under mode-I loading after seven healing cycles, indicating substantial retardation in delamination growth rate resulting in a significant increase in fatigue life.

Performance enhancement of a bioinspired micro air vehicle by integrating a smart composite in its morphing wing

The purpose of this paper is to show the advantages of using a smart composite in a micro air vehicle (MAV) equipped with morphing wing technology. A Macro Fiber Composite (MFC) actuator is attached to the wing’s bottom surface to modify the wing camber during the mission. This material allows the MAV to be optimized according to each flight, thus making it more versatile and attractive to the market. The elongation of the lower surface when a positive voltage is applied to the actuator is translated to an increment in camber, which results in an increment in the maximum lift coefficient, thus enabling the vehicle to fly slower to adapt to any payload. Besides, a reduction in camber results in an increase in aerodynamic efficiency, which improves range and endurance. Several tests of the MAV at prototype level have been carried out at INTA, so as to demonstrate the feasibility of implementing MFC actuators to control and manoeuvre these vehicles. The use of this material in aerospace industry opens up various fields of research in aerospace engineering, such as new features in flight mechanics and aerodynamic performance and new strategies in the design of flight stability and control laws.

Analysis and prediction of tensile properties based on rule of mixtures model for multi-scale ramie plain woven fabric reinforced composite

Natural fibers are increasingly used as sustainable reinforcement for composites because of their carbon capture and renewability. Classical rule of mixtures (ROM) and ROM-based models have been widely used to predict the tensile properties of natural fiber reinforced composites with random or unidirectional oriented structures. However, the woven fabric reinforcement is interwoven by warp and weft yarns, which are spun by short fibers. The multi-scale composite structure made tensile properties challenging to predict. To provide the prediction of woven fabric reinforced composites, the macro and micro ramie fiber reinforced composites fabricated by multi-layer ramie plain woven fabrics, single-layer fabric, and detached yarn were analyzed. Results demonstrated that tensile properties of composites in the warp direction are lower than that in the weft direction due to yarn crimp and weaving damage. The linear fracture behavior of various composites confirms the hierarchical relationship between internal structure and tensile properties. The actual yarn volume fraction in fabrics or composites is calculated and introduced to the ROM model. The improved ROM model significantly enhances the prediction accuracy and efficiency of ramie plain woven fabric reinforced composites in five different areal densities and two interwoven directions.

Actuation Performance of Macro Fibre Composite (MFC) as Actuator in Vibration Reduction of Cantilever Beams

This study proposes a vibration suppression technique that uses piezoelectric material to restrict the dynamic amplitudes of a cantilever beam. The finite element analysis (FEA) model of the cantilever is created and incorporated with Macro Fiber Composite (MFC8507-P2) in the ANSYS framework. A comparative study has been performed using three different types of materials i.e., Polylactic acid (PLA), PLA with Short Carbon Fibers (PLA-SCF Composite), and PLA with Continuous Carbon Fibers (PLA-CCF Composite), for the beam. An external disturbance causes the beam to vibrate, and the MFC8507-P2 patch provides a counter-force to the structure to reduce vibrations. The MFC8507-P2 patch is placed at an appropriate location on each beam to suppress vibration induced by the initial fundamental modes. Modal analysis has been performed to find the natural frequencies and the contribution of each mode to the overall response under dynamic loading conditions. Transient structural analysis is performed to observe the influence of the MFC8507-P2 patch on vibration amplitude with time. Furthermore, frequency response analysis has been performed to determine the impact of the MFC8507-P2 patch on the vibration amplitude of the natural modes. The vibration response has been measured at the tip of the beam and the simulation results validate that the vibration amplitude decreases as the applied voltage increases.

Method of high precision pointing control for spacecraft system based on the active-passive integrated orthogonal micro-vibration isolation platform

To acquire the high precision pointing control for spacecraft system under the disturbance of micro-vibration, and resolve conflicts between the vibration suppression and pointing control, a simultaneous-distributed control method was proposed in this paper. Based on this method and the Stewart platform, an active-passive integrated orthogonal micro-vibration isolation platform with multiple dimensions was developed. Six line-actuators according to the configuration of Gough-Stewart parallel mechanism were selected to build the platform. Specially, the displacement of the line-actuator was converted from the end deflection of two groups of active and passive integrated cantilever beams, which contained viscoelastic damping plate, aluminum material and macro fiber composite (MFC). It should be noted that the dynamic model of the platform system was strongly coupled and it was decoupled by employing the orthogonal configuration. By employing the simultaneous-distributed control strategy, the integrated control algorithm of vibration isolation and pointing was deeply studied. Furthermore, the dynamic behavior and control effects for the 6 degree of freedom (6-DOF) Stewart platform with different control strategies were compared and analyzed. Results showed the method had a good vibration isolation effect and reliable pointing accuracy, which could be applied for the spacecraft requiring high precision pointing.

Experimental Analysis of Hysteresis in the Motion of a Two-Input Piezoelectric Bimorph Actuator

This article presents a comparison of hysteresis courses in the motion of a two-input actuator (bimorph) and hysteresis in the motion of a single-input actuator (unimorph). The comparison was based on the results of laboratory and numerical experiments, the subject of which was an actuator built of three layers: a carrier layer from a glass-reinforced epoxy laminate and two piezoelectric layers from Macro Fiber Composite. The layers were glued together, and electrodes in the Macro Fiber Composite layers were connected to a system that included an analogue/digital board and a voltage amplifier. The main purpose of this research was to compare the characteristic points of the hysteresis curves of the displacement of the bimorph actuator with the characteristic points of the hysteresis curves of the unimorph actuator. Based on the research results, it was noticed that, in the bimorph, the maximum hysteresis and mean hysteresis values increase faster than the maximum displacement of a beam tip. However, values of characteristic input voltages for hysteresis loops—voltage corresponding to a maximum displacement of the actuator beam tip and voltage corresponding to maximum hysteresis—are almost the same for the bimorph and unimorph. From a practical point of view, it was noticed that the unimorph is a better choice compared to the bimorph in applications in which high changes in frequencies of input voltages appear.

Influence of different embedding methods on flexural and actuation performance of piezoelectric intelligent structures

AbstactEmbedding piezoelectric materials as actuators or sensors into structures to form intelligent piezoelectric structures is a research hotspot. Piezoelectric intelligent structures should not only have good sensing and actuation performance, but should also ensure mechanical performance. The influence of forming and cutting embeddings of macro fiber composites (MFC) on the flexural and actuation properties of a piezoelectric composite curved shell was studied by simulation and experiment. The flexural performance was evaluated using a three-point bending simulation and test, and the actuation performance was evaluated by simulating the actuation deformation of a curved piezoelectric cantilever beam. Compared with forming embedding, cutting embedding destroys the continuity of the fiber, resulting in a reduction in the strength of the structure. However, it exhibits good actuation performance. Simultaneously, the influence of ply direction on performance was studied.

Research on Asymmetric Hysteresis Modeling and Feedforward Compensation of Macro Fiber Composite Actuator

Research on Asymmetric Hysteresis Modeling and Feedforward Compensation of Macro Fiber Composite Actuator

Selection of piezoeloectric material and fiber volume fraction to maximize the electrical power produced by macro-fiber composite energy harvesters

A piezoelectric Macro fiber composite (MFC) materials developed in the last decade found widespread applications such as vibration sensing, actuation and structural health monitoring. Unlike conventional ceramic piezoelectric materials (PZT), these composites show many advantages such as flexibility, reliability and high actuation capacity. However, increasing their energy harvesting capabilities still remains a challenge. Modeling and simulation of electrical energy harvesters using MFC patches provide a mean for geometrical optimization and appropriate choice of the MFC composite. This paper proposes a linear analytical model for prediction of the electro-mechanical response of bimorph harvesters using MFC patches. Homogenization technique is used to describe the equivalent piezoelectric properties of the composite structure of the MFC patch. This paper investigates the effect of the volume fraction of the fibers and the material choice of the piezoelectric fibers and epoxy matrix on the generated electrical power. It has been found that an increased fiber volume fraction causes a decrease of the voltage, the power and the velocity amplitudes for a range of load resistance. However, an increase in the fiber volume fraction FVF is achieved by an increase of the current amplitude for a range of load resistance. Maximum amount of power is generated by the bimorph MFC harvester for an FVF of 86% which corresponds to the reference configuration. The piezoelectric fiber material has a significant influence on the output power. In fact, the SONOX-P502 generated the greatest electrical power. However, the material of the matrix has a negligible effect on the generated power.

Restrained Shrinkage of High-Performance Ready-Mix Concrete Reinforced with Low Volume Fraction of Hybrid Fibers.

Cracking due to restrained shrinkage is a recurring issue with concrete bridge decks, impacting durability and ultimately service life. Several scholars' research has proven that the incorporation of fibers in concrete mitigates restrained shrinkage cracking when utilizing high (0.5-3%) fiber volumes. This often presents a mixing and placement issue when used for ready-mixed concretes, which discourages their use in bridge decks. This study aims to optimize the incorporation of fibers for their benefits while producing concrete that is conducive to ready-mix, jobsite use. A series of tests were performed on a high-performance concrete (HPC) mix which incorporated blended, multiple fiber types (steel crimped, macro polypropylene, and micro polypropylene) while maintaining low total fiber (0.19-0.37%) volume. These "hybrid" fiber mixes were tested for multiple mechanical properties and durability aspects, with a focus on the AASHTO T334 ring test, to evaluate fiber efficiency under restrained conditions. Promising results indicate the use of a low-volume hybrid fiber addition, incorporating a macro and micro polypropylene fiber (0.35% by volume) blend, reduced the cracking area by 16.6% when compared to HPC incorporating a single fiber type, and 39% when compared to nonfibrous HPC control mixture.

Creep Phenomenon in a Multiple-Input Single-Output Control System of a Piezoelectric Bimorph Actuator

This article presents a comparison of the course of a creep phenomenon in the control system of a bimorph actuator, in which control voltages were applied to both piezoelectric layers, with the course of the creep phenomenon in the control system of a unimorph actuator, in which a control voltage was applied to only one piezoelectric layer. The bimorph actuator was built from two layers of piezoelectric composite, macro fiber composite was applied, and a carrier layer made of epoxy laminate was used for production of printed circuit boards. A comparative analysis was carried out on the basis of 22 laboratory experiments in which the vision system was used to measure a displacement change of six points of the bimorph actuator structure. Based on the results of laboratory experiments, it was noted that the duration of a transient part is approximately the same in a system with a control voltage applied to one MFC patch as in a system with control voltages applied to two MFC patches. In the system with control voltages applied to two MFC patches, the position change due to the creep process is more than two times bigger in comparison to the system with the control voltage applied to one MFC patch.