Deflection of Cross-Ply Composite Laminates Induced by Piezoelectric Actuators

The coupling effects between the mechanical and electric properties of piezoelectric materials have drawn significant attention for their potential applications as sensors and actuators. In this investigation, two piezoelectric actuators are symmetrically surface bonded on a cross-ply composite laminate. Electric voltages with the same amplitude and opposite sign are applied to the two symmetric piezoelectric actuators, resulting in the bending effect on the laminated plate. The bending moment is derived by using the classical laminate theory and piezoelectricity. The analytical solution of the flexural displacement of the simply supported composite plate subjected to the bending moment is solved by using the plate theory. The analytical solution is compared with the finite element solution to show the validation of present approach. The effects of the size and location of the piezoelectric actuators on the response of the composite laminate are presented through a parametric study. A simple model incorporating the classical laminate theory and plate theory is presented to predict the deformed shape of the simply supported laminate plate

Modeling of macro fiber composite actuated laminate plates and aerofoils

© 2019 Sage Publications . The final, definitive version of this paper has been published in the Journal of Intelligent Material Systems and Structures by Sage Publications Ltd. All rights reserved. It is available at: https://doi.org/10.1177/1045389X19888728This article investigates the modeling of macro fiber composite-actuated laminate plates with distributed actuator patches. The investigation details an analytical and finite element modeling, with experimental validation of the bending strain and deflection of an epoxy E-glass fiber composite laminate. An analytical approach is also developed to estimate the plate deflection from the experimental strain measurements. The analytical method uses direct integration of single dimensional plate bending moments obtained by strain-induced shear moments from the macro fiber composite actuators. Finite element analysis software was used with the composite laminate modeled in ANSYS ACP. The results from both analytical and numerical models show good agreement with the experimental results, with strain values agreeing within 20 ppm and the maximum difference in deflection not exceeding 0.1 mm between models. Finally, an application of the analytical model for developing morphing aerofoil designs is demonstrated.Peer reviewe

Modeling of piezoelectric laminated composite plate using finite element analysis

A finite element model for shape control analysis of piezoelectric laminated composite plate is presented in this paper. Elastic field and electric field of the piezoelectric laminated composite plate has been coupled through the linear piezoelectric constitutive equations. Piezoelectric actuators and sensors are modeled as additional layers either to be surface bonded or embedded in the laminated composite plate. A computer code was written in C++ based on the finite element model and was successfully validated with experimental and numerical results that are readily available in the literatures. The effects of actuator voltage, actuator orientation, fiber orientation and actuator placement along the thickness direction have been simulated and analyzed using the present model

Multistable morphing structures using variable stiffness laminates

Mit zunehmender Thematisierung des Klimawandels vertiefen auch immer mehr Branchen und Forschungseinrichtungen die Suche nach ökologischen Energiequellen. Windenergie ist eine der billigsten sauberen Energieformen und somit eine attraktive Alternative zu nicht erneuerbaren Energien. Das Hochskalieren von Windkraftanlagen gilt klassischerweise als Mittel zur Kostensenkung je Kilowattstunde und ist nach wie vor im Trend. Mit zunehmender Größe der Rotorblätter von Windkraftanlagen besteht jedoch die Notwendigkeit, Konstruktionen zu entwickeln, die in der Lage sind, Extrem- und Ermüdungslasten zu reduzieren. Die aktive Hinterkantenklappe ist ein vielversprechendes Konzept zur Entlastung großer Rotorblätter von Windkraftanlagen. Die meisten existierenden Klappenmechanismen haben zwar das Potenzial zu einer schnellen Reaktionszeit, und damit verbundener Lastreduktion, sind aber oft mit komplizierten Aktuator-Systemen verbunden, was zu zusätzlichem Gewicht und zunehmender Komplexität führt. Darüber hinaus erfordern sie eine kontinuierliche Energiezufuhr, um eine bestimmte Position der Klappe beizubehalten. Multistabile Laminate mit variabler Steifigkeit (VS) haben ein großes Potenzial bei Morphing-Anwendungen, in erster Linie aufgrund der Existenz mehrerer stabiler Gleichgewichtslagen. Der Einsatz von VS-Laminaten mit kurvenförmigen Faserbahnen ermöglicht es, die Leistungsfähigkeit von multistabilen Laminaten als Morphing-Strukturen weiter zu verbessern. Das Hauptziel dieser Arbeit ist es, die Eigenschaften von multistabilen VS-Laminaten nutzbar zu machen, und sie bei einem neuartigen Entwurf von Morphing-Hinterkantenklappen anzuwenden. Um dies zu erreichen, bedarf es nicht nur der Entwicklung numerischer und analytischer Werkzeuge, sondern auch eines geeigneten Entwurfes, um die VS-Eigenschaften in eine Morphing-Klappe zu integrieren. Daher wird in dieser Arbeit ein schnelles semi-analytisches Berechnungsverfahren entwickelt, um stabile Gleichgewichtslagen von VS-Laminaten vorherzusagen. Darüber hinaus wird in einer systematischen Studie untersucht, wie sich die stabilen Zustände bei Variation der kurvenförmigen Faserbahnen ändern. Als Ergebnis dieser Untersuchungen wurden Kriterien abgeleitet durch die VS-Laminate in Familien mit gleichartigen multistabilen Gleichgewichtslagen eingeteilt werden können. Dies ist wiederum für den vorgesehenen Entwurf der Morphing-Klappe erforderlich. Durchschlagen, d. h. der Übergang von einer Gleichgewichtslage zur nächsten, ist ein wesentlicher Prozess bei der Charakterisierung multistabiler Laminate in Morphing-Anwendungen. Zwei unterschiedliche Durchschlagsmechanismen werden hier untersucht, einer mit Hilfe konzentrierter Krafteinleitung, und der andere mit piezoelektrischen Aktuatoren. Das oben genannte semi-analytische Berechnungsverfahren verschafft Einblicke in die zugrundeliegende Mechanik sowie die Eigenschaften des Durchschlagsprozesses. Die Erkenntnisse aus den semi-analytischen Berechnungen ermöglichen Entwurf und Analyse komplexerer multistabiler Rechteckplatten. Es wird der optimale Entwurf von rechteckigen Platten mit Aktuatoren bestimmt, der zu einer maximalen Verschiebung außerhalb der Ebene führt, jedoch eine minimale Durchschlagspannung erfordert. Ein neuartiges Konzept einer Morphing-Hinterkantenklappe mit integrierten rechteckigen bistabilen Platten wird vorgestellt. In diesem neuen Konzept ist die Auslenkung der Hinterkante durch multistabile Platten realisiert. Die Verifikation des vorgeschlagenen Morphing-Mechanismus wird mittels Finite Elemente-Software erbracht.As the concern about climate change grows, more industries and research organizations are stepping up in search of viable solutions. Wind energy is one of the cheapest clean forms of energy, making it an attractive alternative against non-renewable sources. Upscaling of wind turbine has traditionally been considered a means to decrease the cost per kWh, and it remains a trend. However, with an increase in the size of wind turbine rotor blades, there is a need to conceptualize designs capable of reducing ultimate and fatigue loads. Active trailing edge flap is one such promising concept to alleviate loads in large wind turbine blades. Most existing flap mechanisms have the potential for quick reaction time, but it often involves intricate actuation systems, adding additional weight and complexity. Moreover, it requires a continuous supply of energy input to maintain a particular position of the flap. Multistable variable stiffness (VS) laminates have a great potential in morphing applications primarily due to the existence of multiple stable shapes. The use of VS laminates with curvilinear fiber paths allows one to improve further the performance of multistable laminates as morphing structures. The principal aim of this thesis is to exploit the properties of multistable VS laminates and apply them to a novel design of morphing trailing edge flap. This requires not only developing numerical and analytical tools, but also a suitable design to integrate VS laminates into a morphing flap. Therefore in this work, a fast semi-analytical tool is developed to predict the stable shapes of VS laminates. In addition, a systematic study is carried out to investigate the variation the curvilinear fiber paths on the stable equilibrium shapes. As a result of these investigations, VS laminates could be classified into families with similar multistable equilibrium positions. This, in turn, is applied to the envisaged design of the morphing flap. Snap-through, which is a transition from one equilibrium state to another, is a crucial process to characterize multistable laminates in morphing applications. Two different snapping mechanisms are studied, one using concentrated force and the other using piezoelectric actuators. The extension of the aforementioned semi-analytical tool provides insights that reflect the underlying mechanics and characteristics of the snap-through process. The knowledge gained from the semi-analytical calculations facilitates the design and analysis of more complex multistable rectangular plates. Optimal design of rectangular plates with actuators that leads to maximum out-of-plane displacement but with minimum snap-through voltage is determined. A novel concept of a morphing trailing edge flap with integrated rectangular bistable plates is proposed. In this new concept, the trailing edge deflection is realized by the snap-through of the multistable rectangular plates. The viability of the proposed morphing mechanism is examined using finite element tools

Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates

Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors

Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures

Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors

Analysis of Smart Composite Structures Including Debonding

Smart composite structures with distributed sensors and actuators have the capability to actively respond to a changing environment while offering significant weight savings and additional passive controllability through ply tailoring. Piezoelectric sensing and actuation of composite laminates is the most promising concept due to the static and dynamic control capabilities. Essential to the implementation of these smart composites are the development of accurate and efficient modeling techniques and experimental validation. This research addresses each of these important topics. A refined higher order theory is developed to model composite structures with surface bonded or embedded piezoelectric transducers. These transducers are used as both sensors and actuators for closed loop control. The theory accurately captures the transverse shear deformation through the thickness of the smart composite laminate while satisfying stress free boundary conditions on the free surfaces. The theory is extended to include the effect of debonding at the actuator-laminate interface. The developed analytical model is implemented using the finite element method utilizing an induced strain approach for computational efficiency. This allows general laminate geometries and boundary conditions to be analyzed. The state space control equations are developed to allow flexibility in the design of the control system. Circuit concepts are also discussed. Static and dynamic results of smart composite structures, obtained using the higher order theory, are correlated with available analytical data. Comparisons, including debonded laminates, are also made with a general purpose finite element code and available experimental data. Overall, very good agreement is observed. Convergence of the finite element implementation of the higher order theory is shown with exact solutions. Additional results demonstrate the utility of the developed theory to study piezoelectric actuation of composite laminates with pre-existing debonding. Significant changes in the modes shapes and reductions in the control authority result due to partially debonded actuators. An experimental investigation addresses practical issues, such as circuit design and implementation, associated with piezoelectric sensing and actuation of composite laminates. Composite specimens with piezoelectric transducers were designed, constructed and tested to validate the higher order theory. These specimens were tested with various stacking sequences, debonding lengths and gains for both open and closed loop cases. Frequency changes of 15% and damping on the order of more than 20% of critical damping, via closed loop control, was achieved. Correlation with the higher order theory is very good. Debonding is shown to adversely affect the open and closed loop frequencies, damping ratios, settling time and control authority