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Layer Arrangement Impact on the Electromechanical Performance of a Five-Layer Multifunctional Smart Sandwich Plate

Rasool Moradi-Dastjerdi and Kamran Behdinan

Advanced Research Laboratory for Multifunctional Lightweight Structures (ARL-MLS), Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Canada

1.1 Introduction

The reversible effect of piezoelectricity is the ability to generate electrical charge as a result of subjecting to mechanical loads. This active effect is observed in some specific materials called piezoelectric materials. Such active materials are usually employed as attachments or layers in passive structures to provide a self-controlling property with fast response in the resulting smart structures [1]. The application of such active materials mainly relies on their passive structures. In the design of aerostructures, weight and strength are two key points which can be addressed using sandwich structures as they generally contain a thick lightweight core for stabilizing the structures and two thin stiff faces to provide structural strength [2-4]. In this regard, attaching thin layers made of polymer base nanocomposites onto the faces of polymeric porous cores results in multifunctional sandwich structures [5]. Moreover, the use of such passive structures as the host of piezoceramic attachments reduces failure risks due to the brittle structure of piezoceramics. Depending on the application, a wide range of nanofillers with astonishing thermomechanical properties have been proposed and utilized in nanocomposites. Among them, the extraordinary nanofillers of graphene and carbon nanotubes (CNTs) have aroused the interest of researchers in both academia and industry [6-8]. Although there are different parameters in the electromechanical design of five-layer multifunctional smart sandwich plates (5LMSSPs), protecting brittle layers of piezoceramic is also an important issue. Changing the location of piezoceramic layers from faces to middle layers (i.e. between porous core and nanocomposite faces) provides protecting layers. This change in layer arrangements can affect both the mechanical and electrical response of such structures.

In recent literature, different passive structures have been considered as host for piezoelectric sensors/actuators to introduce smart structures with potential applications in energy harvesters [9], noise and vibration reduction [10], fluid delivery [11, 12] and structural damage monitoring [13] where piezoelectricity plays an essential role. In these structures, piezoelectric components come as attached pieces, separate layers or (nano)fillers. Askeri et al. [14] proposed attaching two lead zirconate titanate (PZT) layers on the faces of a transversely isotropic nonpiezoelectric plate to introduce a smart plate. Functionally graded (FG) metal/ceramic materials, as advanced materials, have been considered as the passive part of smart structures activated by piezoelectric materials. In this regard, passive plates and shells made of such FG materials and PZT-activated layer(s) were considered under thermo-electro-mechanical loads to study their nonlinear dynamic responses in [15-17]. The deflections of FG titanium/aluminum oxide plates integrated between PZT faces under static and dynamic electromechanical loads were presented in [18]. Khoa et al. [19] covered the outer layer of imperfect FG metal/ceramic cylindrical shells with a PZT layer and studied its buckling resistance. In another setting, laminated composites have been also employed as the passive part of piezoelectric activated smart structures. Talebitooti et al. [20] considered such plates covered with PZT sensor and actuator layers to optimally control the vibrations of the obtained smart plates using a feedback algorithm. By developing an isogeometric finite element method (FEM), Phung-Van et al. [21] aimed to outline the static deflections and vibrations of the same composite plates actuated by PZT layers. To reduce structural weight, nanocomposite materials have also been used as the host of piezoelectric actuated smart structures. In addition, there are different types of nanofillers that can be utilized in specific applications. The use of composite plates enhanced with wavy CNTs and carbon fibers as the multifunctional host of two piezoelectric patches was proposed by Kundalwal et al. [10]. They utilized piezoelectric patches made of piezoceramic fibers embedded in a polymer to provide smart damping property for host plates. Mohammadimehr et al. [22] employed nanofillers of CNTs and piezoelectric nanotubes of boron nitride in passive and active polymers and considered double sandwich plates. They presented the vibration behaviors of such smart structures subjected to magnetic and electric fields. Moradi-Dastjerdi et al. [23] proposed the use of nanocomposite plates enhanced with nanoclays in aggregated and intercalated forms as the passive layers of a smart plate with two PZT faces. Arani et al. [24] utilized two piezoelectric faces made of polyvinylidene fluoride to control the frequencies of CNT/polymer microplates under magnetic field and located on an elastic foundation. Malekzadeh et al. [25] considered a graphene/polymer multi-layered circular plate with a randomly located hole activated with two PZT faces and outlined its vibration behavior. For further reduction of structural weight in the passive layer, porous material can be utilized. Jabbari et al. [26, 27] suggested the use of circular plates with FG dispersions of embedded porosities for passive layers activated by attaching two PZT faces and investigated the stability resistances of the obtained smart circular plates. Askari et al. [28] considered rectangular plates with FG patterns of porosity dispersion between two PZT faces to determine porosity impact on the natural frequencies of the resulted active plates. Barati and Zenkour [29] studied the vibrations of active porous plates made of an FG mixture of two different piezoceramics. Mohammadi et al. [30] considered aluminum cylindrical pressure vessels with three patterns of porosity dispersion integrated between two inner and outer PZT faces as sensor and actuator. They presented the electromechanical responses of such smart pressure vessels located in elastic media. In a more advanced setting of smart structures, the combination of nanocomposite and porous materials have been utilized as multifunctional passive structures. Nguyen et al. [31, 32] proposed three-layer smart sandwich plates with a metal porous layer enhanced with graphene platelets (GPLs) as a passive core integrated between two active PZT faces. They considered FG patterns for the dispersions of GPLs and porosities in the passive layer and obtianed two different sets of results including vibrational response and its active control using PZT layers. However, GPLs in the core layer of these three-layer smart plates interfere with the electrical charge and potential field obtained in PZT faces. In addition, according to the concept of sandwich panels, the use of separated layers of nanocomposite and porous materials leads to five-layer multifunctional smart panels with higher structural stiffness to weight ratio. In these regards, Setoodeh et al. [33] proposed such five-layer smart curved shells including two PZT faces, two CNT-enhanced nanocomposite middle layers and one porous core with FG patterns for the dispersions of nanofillers and porosities. Another set of five-layer smart plates including PZT faces, graphene/polymer middle layers and porous core were also proposed and thermo-electro-mechanical behaviors of such 5LMSSPs are presented in [34-37].

Five-layer multifunctional smart sandwich plates with layers made of porous, GPL/polymer and PZT have been proposed in the literature. However, considering piezoceramic layers as the faces of such plates is a challenging point because of their brittle nature. Therefore, in this work, a comparison study has been conducted to explore the impact of changing the location of piezoceramic layers from faces to middle layers on the electromechanical performances of 5LMSSPs. In this regard, a mesh-free solution has been developed based on Reddy's third-order shear deformation theory (TSDT). Moreover, Halpin-Tsai equations with the ability to capture the shape of nanofillers are employed to define the mechanical properties of GPL/polymer nanocomposite layers. In addition to the impact of layer arrangement, the effects of GPL volume and dispersion, porosity volume and the thickness of each layer are investigated in this chapter.

1.2 Modeling of 5LMSSP

The considered multifunctional smart sandwich plates have five layers including one porous, two piezoelectric and two GPL-reinforced nanocomposite layers to provide a wide range of industrial applications. There is no doubt in the use of a porous layer as the core because embedding porosity in the core results in a remarkable structural weight reduction without a significant loss of structural stiffness. However, the locations of nanocomposite and piezoelectric layers could be changed based on the operating conditions of...