Active Fiber Composites Research Articles

Date Palm Tree Waste Recycling: Treatment and Processing for Potential Engineering Applications

Date palm, the most important tree in Saudi Arabia and the Middle East, produces a huge amount of waste yearly in the form of fibrous materials, dried fruits, and seeds. Such waste is a great source of excellent degradable biomass that can be used in numerous applications as natural fiber composites, active carbon precursors, and even nano-featured sheets. That rich resource is yearly burned on date palm farms due to the lack of effective processing strategies. This review offers a scientific evaluation for date palm waste in terms of specifications and applications, and it proposes pre-treatment processes to produce fibrous and powder raw materials to be used in some engineering and industrial applications. Additionally, some possible advanced industrial applications, such as active carbon and natural fiber composites, will be discussed and reviewed.

Nonlinear vibration analysis of smart functionally graded plates

Abstract This paper presents the damping characteristics of nonlinear vibrations of functionally graded (FG) plates utilizing piezoelectric composite material. For this analysis the active fiber composite (AFC) is taken as piezoelectric composite material. Finite element (FE) models are made for the FG plates combined with active constrained layer damping (ACLD) patches made of AFC material. Von Karman strain–displacement equations considering the displacement fields and satisfactory boundary conditions are used. The working of the ACLD patches for nonlinear vibration damping of FG plates is explored where AFC is used for the constraining layer of the ACLD patches. The Golla-Hughes-McTavish method is used for modeling the constrained layer of ACLD patch which is considered to be made of a viscoelastic material. Simulation models are also developed using ANSYS software for smart FG plates for validating the FE model. The contribution of ACLD patches for the nonlinear vibration control of the FG plates is investigated.

Passive flutter suppression of damaged smart laminated composite plate using active fiber composite layer

This research addresses the effect of damage on flutter characteristics of laminated composite plate and passive control of flutter with active fiber composite (AFC) layer bonded over the substrate. A finite element model coupled with MSC.Nastran is developed to calculate the flutter characteristics of smart laminated composite plate. The damage characterized based on anisotropic damage formulation is incorporated through the finite element model. The effect of orientation and location of damage on flutter characteristics of laminated plate is studied. Further AFC layer with interdigitated electrode, which is more adaptive and efficient than conventional monolithic piezoelectric, is considered over the top of substrate layer to act as actuator. The enhancement of the flutter characteristics lost due to damage, is investigated by activating AFC layer with applied voltage. The AFC layer is observed to have great potential to regain the flutter strength of composite plate. Communicated by Chandrika Prakash Vyasarayani.

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).

Novel design of interdigitated electrodes for piezoelectrictransducers

Novel design of interdigitated electrodes capable of increasing the performance of piezoelectric transducers are proposed. The new electrodes\' geometry improve the electromechanical coupling by offering an enhanced adaptation of the electric field to the interdigitated electrode configuration. The proposed analysis is based on finite element modeling and takes into account local polarization effect. It is shown that the proposed electrodes considerably increase the strain generation compared to flat electrode arrangement used for Macro Fiber Composite (MFC) and Active Fiber Composite (AFC) actuators. Also, electric field singularities are reduced allowing better reliability of the transducer against electric failure.

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.

Performance analysis of smart laminated composite plate integrated with distributed AFC material undergoing geometrically nonlinear transient vibrations

The present work focuses on geometrically nonlinear transient analysis of laminated smart composite plates integrated with the patches of Active fiber composites (AFC) using Active constrained layer damping (ACLD) as the distributed actuators. The analysis has been carried out using generalised energy based finite element model. The coupled electromechanical finite element model is derived using Von Karman type nonlinear strain displacement relations and a first-order shear deformation theory (FSDT). Eight-node iso-parametric serendipity elements are used for discretization of the overall plate integrated with AFC patch material. The viscoelastic constrained layer is modelled using GHM method. The numerical results shows the improvement in the active damping characteristics of the laminated composite plates over the passive damping for suppressing the geometrically nonlinear transient vibrations of laminated composite plates with AFC as patch material.

Geometrically nonlinear transient vibrations of actively damped anti-symmetric angle ply laminated composite shallow shell using active fibre composite (AFC) actuators

In present work, the thin laminated composite shallow shell as smart structure with AFC material’s ACLD treatment is analyzed for geometrically nonlinear transient vibrations. The AFC material is used to make the constraining layer of the ACLD treatment. Golla-Hughes-McTavish (GHM) is used to model the constrained viscoelastic layer of the ACLD treatment in time domain. Along with a simple first-order shear deformation theory the Von Kármán type non-linear strain displacement relations are used for deriving this electromechanical coupled problem. A 3-dimensional finite element model of smart composite panels integrated with the ACLD treated patches has been modelled to reveal the performance of ACLD treated patches on improving the damping properties of slender anti-symmetric angle-ply laminated shallow shell, in controlling the transient vibrations which are geometrically nonlinear. The mathematical results explain that the ACLD treated patches considerably enhance the damping properties of anti-symmetric angle-ply panels undergoing geometrically nonlinear transient vibrations.

Performance analysis of geometrically nonlinear static deformations of laminated composite plates using PFRC/AFC materials

The present work focuses on geometrically nonlinear static analysis of laminated smart composite plates integrated with the patches of Active fiber composites (AFC) and piezoelectric fiber-reinforced composite (PFRC) materials acting as the distributed actuators has been compared using generalized energy based finite element models. To derive this coupled electromechanical finite element model the Von Karman type nonlinear strain displacement relations and a simple first-order shear deformation theory (FSDT) are used. Eight-node diso-parametric serendipity elements are used for discretization of the overall plate integrated with AFC/PFRC patch material .Picard’s direct iteration method with under relaxation is used to solve the nonlinear finite element equilibrium equations. The performance of both AFC and PFRC patches has been investigated and compared for symmetric cross-ply laminated composite plate substrate.

Vibration analysis and control of smart composite plates with delamination and under hygrothermal environment

An analysis of delaminated composite plates with integrated active fibre composite (AFC) actuators and sensor under hygrothermal environment has been undertaken in the present work. The top and bottom plies of the laminate constitute AFC actuators and sensors. In the present investigation, hygrothermal loading is taken into consideration, and the effect of moisture and temperature on the delaminated plate structures is analysed. The minimum total potential energy approach is used for arriving at the governing equation. A finite element model for centrally located delamination is developed on the basis of first order shear deformation theory. An eight noded serendipity element with five degrees of freedom per node is considered for the finite element formulation. A parametric study on the effect of stacking sequence, boundary conditions and environmental conditions in the presence of delamination on the laminated plate is studied. The key observations from the parametric study are: there will be reduction in natural frequencies in the presence of delamination and/or hygrothermal loading, and reduction in structural stiffness due to the presence of delamination can be negated by applying voltage to the active fibre actuator layer.

Ferroelectric hybrid fibers to develop flexible sensors for shape sensing of smart textiles and soft condensed matter bodies

Piezoelectric fibers are widely used in composites for actuator and sensor applications due to its ability to convert electrical pulses into mechanical vibrations and transform the returned mechanical vibrations back into electrical signal. They are beneficial for the fabrication of composites especially 1–3 composites, active fiber composites (unidirectional axially aligned PZT fibers sandwiched between interdigitated electrodes and embedded in a polymer matrix) etc, with potential applications in medical imaging, structural health monitoring, energy harvesting, vibration and noise control. However, due to the brittle nature of PZT fibers, maximum strain is limited to 0.2% and cannot be integrated into flexible sensor applications. In this contribution, a new approach to develop flexible ferroelectric hybrid fibers for soft body shape sensing is investigated. Piezoelectric particles incorporated in a polymer matrix and extruded as fiber, 0–3 composite in fibrous form is studied. Commercially obtained calcined PZT and calcined BaTiO3 powders were used in the unsintered form to obtain flexible soft condensed matter ferroelectric hybrid fibers. The extruded fibers were subjected to investigation for their electromechanical behavior as a function of electric field. The hybrid fibers reached 10% of the maximum polarization of their sintered counterpart.

Nonlinear transient analysis of smart laminated composite plate integrated with PVDF sensor and AFC actuator

In this article, the geometrically nonlinear transient response of the smart laminated composite plate is investigated under the coupled electromechanical load. The plate has been modeled using the higher-order kinematic model in conjunction with Green-Lagrange nonlinear strains. The electric potential across the sensor/actuator layer is modeled as the quadratic function of the thickness coordinate. The domain is discretized with the help of a nine noded isoparametric quadrilateral element with thirteen degrees of freedom per node. The desired transient responses are obtained using the direct iterative method in association with Newmark’s time integration scheme. In order to achieve distributed actuator and the sensor behaviour the active fibre composite and Polyvinylidene fluoride fibre reinforced composite are utilized along the poled fibre direction and through the thickness, respectively in this present investigation. In this analysis, two types of configurations of the sensor and actuator (collocated and non-collocated) are considered to compute the active stiffening responses. The convergence and the validity of the present numerical model have been checked. Finally, the effects of various geometrical parameters along with the sensor and the actuator arrangements on the nonlinear transient responses of the laminated composite plate are examined by solving various numerical examples.

Temperature and time dependence of the electro-mechanical properties of flexible active fiber composites

Active fiber composites (AFCs) are comprised of piezoelectric fibers embedded in a polymeric matrix. AFCs use interdigitated electrodes, which produce electric field lines parallel to the fiber direction, thus taking advantage of the larger d33 piezoelectric coefficient. The polymer volume content of the AFCs is generally more than 50%; since polymers tend to have behaviors affected by their viscoelastic characteristics especially at elevated temperatures, it is necessary to understand the thermo-electro-mechanical behavior of AFCs at different loading rates. In this study, mechanical, electrical and electromechanical properties of AFCs were measured at different isothermal temperatures, namely 25 °C, 50 °C and 75 °C and at different loading rates. The measurements of all the properties of AFCs were done along the fiber direction. It was found that at higher temperatures, the modulus and tensile strength decreased for all strain rates and the strain at failure increased. The remnant polarization increased with decrease in frequency and increase in temperature; however, the coercive field decreased with temperature and was not affected by the frequency. Due to the viscoelastic behavior of the epoxy, the piezoelectric coefficient d33 increased at higher temperature and lower frequency. It was also noted that this coefficient is dependent on the magnitude of the electric field.

Active Vibration Control of Smart Functionally Graded Beams

This work is devoted to examine the performance of the constraining layer of the active constrained layer damping (ACLD) treatment made of the active fiber composites (AFC) materials for vibration control of functionally graded (FG) beams. The task of investigating the performance of the active constrained layer damping (ACLD) treatment has been accomplished to demonstrate the use of AFCs as the materials for distributed actuators. Finite Element (FE) model is developed to describe the open loop and closed loop dynamics of the FG beams integrated with the patches of the ACLD treatment. The closed loop frequency response functions computed by the FE models reveal that the ACLD treatment with its constraining layer composed of AFC material significantly enhances the damping characteristics of the FG beams.The performance of the ACLD treatment when the orientation angle of the piezoelectric fibers of the AFC constraining layer is varied has also been investigated. Such variation of piezoelectric fiber orientation angle significantly affects the controllability of the ACLD treatment for active damping of the FG beams. The investigations carried out here may be useful for further experimental verifications and suggest the potential use of AFC materials for developing new distributed actuators of light-weight smart structures.

Geometrically Nonlinear Analysis of Smart Sandwich Plates

This paper presents the geometrically nonlinear analysis of smart sandwich plates. The top surface of the plate is integrated with a layer of commercially available active fiber composite. Considering the First order shear deformation theory individually for each layer of the sandwich plate, a three-dimensional finite element model has been developed. The performance of active fiber composite for the smart control of geometrically nonlinear deflection of the sandwich plates has been studied and numerical results are presented.

Design and finite element analysis of a short piezoelectric fiber-reinforced composite actuator

Piezoelectric distributed actuators are exhaustively utilized in control of the structural deformation/vibration. These actuators are also used in the form of smart composite of which active fiber composite (AFC) and macro-fiber composite (MFC) are the most popular smart composites. In the present work, few shortcomings of MFC/AFC actuator in its structural applications are identified and those are alleviated through the proposition of a short piezoelectric fiber-reinforced composite (SPFRC) actuator. The SPFRC is composed of equally spaced coaxial short piezoelectric fibers embedded within the polymer matrix. Every fiber is poled along its length that yields maximum piezoelectric stress/strain within the composite along the same direction in effect of co-directional applied electric field. This piezoelectric effect quantified by the coefficient (e11) is the main parameter in its use as an actuator with a special arrangement of electrodes in microscale. The SPFRC is designed with an objective of improved magnitude of major effective coefficient (e11), and it is performed through a continuum micro-mechanics finite element analysis of its effective electro-elastic properties. The actuation-capability of SPFRC actuator according to its present design is verified by analyzing the geometrically nonlinear electro-elastic deformations of a simply supported smart beam. The micro-mechanics analysis reveals a significant magnitude of e11 of SPFRC although it is lesser than the case of continuous fibers within the similar composite. However, the analysis of smart beam reveals better actuation-capability of the smart composite actuator when short fibers are used instead of continuous fibers retaining the same applied voltage and electrodes.

A parametric study on flexible electro-active composites: Importance of geometry and matrix properties

Active fiber composites comprised of long circular fibers embedded in an epoxy polymer, where the fibers are made of the piezoelectric ceramic lead zirconate titanate. The active fiber composites use interdigitated electrodes, which produce electric field lines parallel to the fiber direction instead of through-the-thickness. It is noted, however, that the d33 of the active fiber composite is almost a third that of the lead zirconate titanate, mainly because of the significant mismatch in dielectric properties between the epoxy matrix and the ceramic fibers. The objective of the current work is to investigate the effects of active fiber composite geometry and polymer properties on the overall performance of active fiber composite in terms of mechanical displacement and electric potential. An active fiber composite model that considers several fibers, epoxy matrix, and electrode fingers (interdigitated electrodes) as part of the representative volume element is developed and implemented using finite element method. The model examines the effect of the interdigitated electrode parameters such as the spacing between the electrode’s fingers and their width. The other parameters examined are the fiber diameter and matrix properties. This parametric study will lead to an optimized geometry and matrix that can be used for the manufacturing of next-generation active fiber composites with higher performance than what is currently available.

Vibration Control of Sandwich Plates

This paper presents the active control of vibrations of sandwich plates using piezoelectric composites (PZC). The top surface of the plate is integrated with the patches of active constrained layer damping treatment. Active fiber composite, one of the commercially available PZCs, is used as the material of the constraining layer of the patches and the constrained layer of the patch is composed of a viscoelastic material. Considering the first order shear deformation theory individually for each layer of the sandwich plate, a three-dimensional finite element model has been developed. The performance of active fiber composite for the smart vibration control of the sandwich plates has been studied and numerical results are presented. Emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the constraining layer on the control authority of the patches.

Numerical and analytical analyses for active fiber composite piezoelectric composite materials

This study consists of the calculation of the effective properties for active fiber composites made of either circular or square cross-section fibers not only by using finite element analysis and representative volume elements, but also based on the asymptotic homogenization method. Thus, there is an investigation about different approaches, which have specific mathematical formulations and unique characteristics. The comparison between numerical and analytical approaches shows that the numerical results are in good agreement with investigations performed by both analytical and semi-analytical methods, mainly the predictions for loading applied in fiber direction. For active fiber composites made of circular cross-section fibers, the maximum difference between asymptotic homogenization method and finite element analysis is from 1.29% to 5.49% for mechanical and piezoelectric effective properties, respectively, considering representative volume element in square arrangement. However, for active fiber composites made of square cross-section fibers, the maximum difference between semi-analytical method and finite element analysis is from 2.15% to 17.09% for mechanical and piezoelectric effective properties, respectively, considering representative volume element in square arrangement.

Nonlinear finite element analysis of smart laminated composite sandwich plates

This paper deals with the nonlinear dynamic analysis of smart laminated composite sandwich plates. A three dimensional energy based finite element (FE) model has been developed for the composite sandwich plates integrated with the patches of active constrained layer damping (ACLD) treatment. Von Kármán type nonlinear strain–displacement relations and the first-order shear deformation theory (FSDT) are adopted individually for each layer of the sandwich plate in developing the FE model. The constraining layer of the ACLD treatment is considered to be made of active fiber composite (AFC) material. The Golla–Hughes–McTavish (GHM) method is used to model the constrained viscoelastic layer of the ACLD treatment in the time domain. Sandwich plates with symmetric and antisymmetric laminated faces separated by HEREX core are considered for evaluation of the numerical results. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the composite sandwich plates for suppressing their geometrically nonlinear transient vibrations. The effect of variation of piezoelectric fiber orientation angle in the AFC material on the control authority of the ACLD patches is also investigated.