Smart Shell Research Articles

Vibration Control of a Smart Shell Reinforced by Graphene Nanoplatelets

Smart control and dynamic investigation of a graphene nanoplatelets reinforced composite (GPLRC) cylindrical shell surrounded by a piezoelectric layer as actuator and sensor based on a numerical solution method called generalized differential quadrature method (GDQM) are presented for the first time. The strains and stresses can be determined via the first-order shear deformable theory (FSDT). For accessing to various mass densities, thermal expansion as well as Poisson ratio, the rule of mixture is applied, although a modified Halpin–Tsai theory is used for obtaining the module of elasticity. The external voltage is applied to the sensor layer, while a proportional-derivative (PD) controller has been utilized for controlling the output of sensor. GPLRCs boundary conditions are derived through governing equations of the cylindrical shell using an energy method known as Hamilton’s principle. The outcomes show that the PD controller, viscoelastic foundation, slenderness factor ([Formula: see text]/[Formula: see text], external voltage and graphene nanoplatelets (GPLs) weight fraction have a considerable impact on the amplitude, and vibration behavior of a GPLRC cylindrical shell. As an applicable result in related industries, the parameter and consideration of the PD controller have a positive effect on the static and dynamic behaviors of the structure.

An efficient facet shell element with layerwise mechanics for coupled electromechanical response of piezolaminated smart shells

In this work, an efficient four-node facet shell element is presented for analysis of doubly curved multilayered piezoelectric shells, based on an electromechanically coupled third order zigzag theory. It is motivated by the excellent performance of the shell element developed earlier by the authors for elastic laminated shells. The laminate theory not only incorporates a layerwise description of the inplane displacements but also accounts for the layerwise normal deformation due to the d33-effect of the piezoelectric layers. The number of primary displacement variables is, however, the same as for the smeared third order theory (TOT). A quadratic variation of the electric potential across the piezoelectric layers is assumed, while satisfying the equipotential condition of electroded piezoelectric surfaces using the concept of electric nodes. The performance of the element is assessed for the stress analysis under mechanical and electric potential loads, and for the free vibration response of hybrid piezolaminated deep shells in comparison with the three dimensional piezoelasticity based analytical and finite element solutions. The comparison shows excellent accuracy of the present element for the deflection, stresses, sensory potential, electric displacement and natural frequencies of hybrid shells made of composite as well as the highly inhomogenous soft-core sandwich laminates, for which the smeared TOT is shown to produce highly erroneous results. It is also shown to yield better accuracy than the other available elements of similar computational efficiency for hybrid composite shells.

Topographic Mechanics and Applications of Liquid Crystalline Solids

Liquid crystal elastomers and glasses suffer huge length changes on heating, illumination, exposure to humidity, etc. A challenge is to program these changes to give a complex mechanical response for micromachines and soft robotics. Also desirable can be strong response, where bend is avoided in favor of stretch and compression, even in the slender shells that are our subject. A new mechanics paradigm arises from such materials—spatially programmed anisotropy allows a spatially varying metric to develop upon stimulation, with evolving Gaussian curvature, topography changes, and superstrong actuation. We call this metric mechanics or topographical mechanics. Thus programmed, liquid crystalline solids meet the above aims. A frontier is the complete programming and control of topography, driving both Gaussian and mean curvature evolution. That, and smart shells, which sense and self-regulate, and exotic new realizations of anisotropic responsive structures, are our concluding themes.

Active Vibration Control of a Fluid-Conveying Functionally Graded Cylindrical Shell using Piezoelectric Material

Active vibration control of a smart FG (functionally graded) cylindrical shell conveying fluid in thermal environment is studied theoretically by using a laminated piezoelectric actuator. Velocity feedback control law is implemented to activate the piezoelectric actuator. Considering the electric-thermo-fluid-structure interaction effect, a nonlinear dynamic model of the smart fluid-conveying FG cylindrical shell is developed based on Hamilton’s principle and von-Karman type geometrical nonlinear relationship. The inviscid, incompressible, isentropic and irrotational fluid is coupled into governing equations using the linearized potential theory. The Galerkin’s method is used to obtain the nonlinear governing equations of motion of the coupled system. The multiple time scales approach is applied to solve the resulting governing equations for analysing the nonlinear dynamic characteristics of the coupled system. The influence of fluid flow velocity, feedback control gains of piezoelectric voltage, external excitation and material properties of FGM on the frequency-response curves of system are investigated. The results indicate that the piezoelectric voltage is an effective controlling parameter for vibration control of the system, and the flow velocity can effect significantly the vibration amplitude and nonlinearity of the coupled system.

General method for the production of hydrogel droplets from uniformly sized smart shell membranes

A smart solid-state liquid crystal shell membrane template prepared by a microfluidic method with a reactive mesogen mixture doped with a nematic liquid crystal of 5CB as a porogen was used for a facile and general method to produce uniformly sized hydrogel droplets.

Isogeometric analysis of laminated smart shell structures covered with piezoelectric sensors and actuators using degenerated shell formulation

An isogeometric approach to the analysis of laminated composite smart shell structures based on the degenerated formulation and Mindlin–Reissner assumptions using non-uniform rational B-spline basis functions is the subject of this article. To model the laminated orthotropic smart free-form shells, the equivalent single layer theory is adopted, and an accurate approach to construct the local basis systems is used. To consider the electric potential in the piezoelectric layers, a sub-layer approach is employed that assumes linear variation over the thickness of the sub-layer. To investigate the performance of the approach, static, free vibration, and static control analysis of laminated composite shells covered with piezoelectric sensor and actuator layers with different degrees of basis functions is performed. Also, the effect of mechanical loading, various input voltages, and different boundary conditions on the static response and natural frequencies have been investigated. Several numerical examples are presented to demonstrate the efficiency and accuracy of the approach and validated with the existing results from the literature.

Static and dynamic FE analysis of piezolaminated composite shells considering electric field nonlinearity under thermo-electro-mechanical loads

The present article focuses on the static and dynamic finite element simulations of smart piezolaminated composite shell structures considering strong electric field nonlinearity under thermo-electro-mechanical loads. To model the electromechanical behaviour of piezoelectric patches or layers under large applied electric fields more efficiently, two-way coupled rotationally invariant second-order nonlinear constitutive relations are used in the variational principle approach. Furthermore, the nonlinear piezoelectric element formulations are further extended to capture the response under temperature gradients. Quadratic and cubic polynomial approximations are deemed to represent the electric potential and temperature fields, respectively. Validation of the present element formulation has been done in comparison to experimental and numerical investigations of those available in the literature. Moreover, numerical simulations are performed to study the large electric field nonlinearities of piezolaminated structures in static and dynamic as well as active vibration control problems under both mechanical and thermal loads. The numerical simulations have shown that using the piezoelectric nonlinearity, both the static shape control and vibration suppression either under mechanical or thermal loads can be accomplished at much lower actuation voltages than estimated by the linear model.

Exact solutions for static electro-mechanical response of doubly curved smart laminated shells

This paper deals with the derivation of the exact solutions for the static electro-mechanical response of a simply-supported doubly curved (DC) smart shell, composed of a piezoelectric fiber reinforced composite (PFRC) placed over a laminated substrate. These responses are evaluated when the system is subjected to distributed electrical and mechanical loads. The electro-mechanical governing equations and the associated boundary conditions have been derived here for the curvilinear coordinate system using the variational principle. Closed-form expressions for the mechanical displacement and the electrical potential have been obtained by solving these governing differential equations and simultaneously satisfying the derived boundary conditions. Numerical results have been presented for different shell geometries. The effect of the curvature and the geometric parameters of the PFRC layer over its performance as an actuator are studied and compared for these shells. Also, the effect of varying geometric parameters of the PFRC over its performance as a sensor is studied. Optimal dimensions of the PFRC for use as an actuator and sensor/harvester have been proposed. This study may be considered as a benchmark for use in the numerical and experimental studies involving smart shells.

Numerical and experimental nonlinear dynamic response reduction of smart composite curved structure using collocation and non-collocation configuration

In this work, a generic geometrical nonlinear mathematical model of smart composite curved shell panels has been developed for the evaluation of the linear and nonlinear dynamic responses. Further, the dynamic deflections are reduced by employing the piezoelectric material with the parent composite using two different arrangements (sensor and actuator). The current layered structure model is developed based on the higher-order mid-plane kinematics including the stretching effect. The electric potential due to the piezoelectric material included via a quadratic function of thickness for the current combined electro-elastic modeling. The geometrical distortion of the smart shell panel structure accounted via Green-Lagrange strain field including all of the nonlinear higher-order terms. The desired responses are evaluated computationally using an original computer code (MATLAB environment) with the help of the current higher-order model and finite element steps. The nonlinear dynamic deflection values are obtained through the direct iterative method in conjunction with Newmark’s integration. Additionally, the accuracy of the proposed model is demonstrated via comparison study with the available published literature with and without electric field potential. The reduction of response frequencies is also compared with the in-house experimental data. Lastly, few more numerical examples are computed for the various geometrical parameter including the shell configuration and the comprehensive behaviour of the currently developed nonlinear numerical model for the analysis of smart layered structure discussed in details.

One-Pot Synthesis of a Bismuth Selenide Hexagon Nanodish Complex for Multimodal Imaging-Guided Combined Antitumor Phototherapy.

For integrating therapy and diagnosis into a single nanoparticle for higher antitumor efficiency and lower toxicity, our group designed a smart theranostic nanoplatform based on a hyaluronic acid-doped polypyrrole-coated bismuth selenide loading with a zinc phthalocyanine nanodish complex (Bi2Se3@HA-doped PPy/ZnPc) for multimodal imaging-guided combined phototherapy. Moreover, we expect that the HA-doped PPy smart shell for the surface functionalization will also be applied to a variety of 2D nanomaterials sharing a similar structure with Bi2Se3 to broaden their applications in biomedicine. The Bi2Se3 hexagon nanodish was synthesized via a simple and safe solution-based method compared to the commonly adopted ones. A one-pot synthesis of the naoncomplex was carried out by adding HA during the polypyrrole coating on the Bi2Se3 process, and then it was further loaded with ZnPc. Besides the good ability for infrared thermal, photoacoustic, fluorescence, and X-ray computed tomography imaging, the nanodish complex has its own high photoheat conversion efficiency for photothermal therapy, and it has remarkable optical absorption of the coefficient for photodynamic therapy. With the EPR effect of nanoparticles and the CD44-targeted effect of HA, the tumor-growth inhibition ratio of Bi2Se3@HA-doped PPy/ZnPc for PTT/PDT was as high as 96.4%, compared with that of the PTT (68.0%) or PDT (24.3%) alone, showing an excellent combined therapeutic effect. Moreover, no obvious toxicity in vivo was caused by the nanoparticles. Thus, such a Bi2Se3@HA-doped PPy/ZnPc nanodish complex has promise for real-time monitoring and precise, high-efficiency antitumor treatment.

Delivery of Hydrophobic Anticancer Drugs by Hydrophobically Modified Alginate Based Magnetic Nanocarrier

Since most of the anticancer drugs have low solubility in water, the clinical use of them is limited unless by some modification the solubility increases or the drug is carried with a soluble compartment. To solve this problem, we prepared a magnetic nanocarrier with a hydrophobic surface based on oleic acid chains in which hydrophobic drug molecules such as doxorubicin hydrochloride (DOX) and paclitaxel (PTX) are easily adsorbed onto the surface. Since the drug molecules are physically adsorbed on the surface, large amounts of DOX (282 mg·g–1) and PTX (316 mg·g–1) were immobilized onto the nanocarrier. Then, the surface of the drug loaded magnetic core was covered by a smart pH-sensitive shell based on sodium alginate. The alginate shell around the magnetic core increased the stability and biocompatibility of the drug loaded nanocarrier. The results of the drug release profile showed that the drug molecules were released faster in acidic medium than in the neutral medium. The MTT assay of the nanocarrier...

Seismic response of smart nanocomposite cylindrical shell conveying fluid flow using HDQ-Newmark methods

In this research, seismic response of pipes is examined by applying nanotechnology and piezoelectric materials. For this purpose, a pipe is considered which is reinforced by carbon nanotubes (CNTs) and covered with a piezoelectric layer. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via cylindrical shell element and Mindlin theory. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite and to consider the effect of the CNTs agglomeration on the scismic response of the structure. Moreover, the dynamic displacement of the structure is extracted using harmonic differential quadrature method (HDQM) and Newmark method. The main goal of this research is the analysis of the seismic response using piezoelectric layer and nanotechnology. The results indicate that reinforcing the pipeline by CNTs leads to a reduction in the displacement of the structure during an earthquake. Also the negative voltage applied to the piezoelectric layer reduces the dynamic displacement.

Geometrically nonlinear FE analysis of piezoelectric laminated composite structures under strong driving electric field

To give a precise prediction of piezolaminated smart structures under strong electric field resulting in large displacements and rotations, the paper develops various geometrically nonlinear models with taking into account the electroelastic material nonlinear effect. The present nonlinear FE formulations are derived based on the first-order shear deformation theory (FSDT) with taking into account various geometric nonlinearities, which include von Kármán type nonlinearity, moderate rotation nonlinearity, and large rotation nonlinearity. The constitutive equations with consideration of piezoelectric material nonlinearity are integrated into the present FE formulations. The proposed nonlinear FE models are first validated by experimental and numerical examples in the literature, and later on implemented into numerical analysis for piezolaminated smart plates and shells with applied strong electric field.

Smart shell membrane prepared by microfluidics with reactive nematic liquid crystal mixture

Smart, uniform-sized, solid-state nematic liquid crystal (NLC) (NLCsolid) shell membranes were successfully fabricated from a reactive mesogen mixture (RMM727) and 4-cyano-4′-pentylbiphenyl (5CB) using a microfluidic method that combines flow-focusing and co-flow glass capillary geometries after UV curing and 5CB extraction. The NLC shells having planar anchoring with poly(vinyl alcohol) (NLCp shells) showed unavoidable defects as per the Poincaré theorem, with a total of +2 defect strengths on the top of the shell (often the weakest point of the shell), and were usually ripped during UV curing. The NLC shells having homeotropic anchoring with sodium dodecyl sulfate/polysorbate 80 (1/1, w/w) (NLCh shells) had a defect-free structure and could be formed into NLCsolid shells without ripping when the density of the RMM727/5CB mixture matched that of the aqueous medium in the microfluidic channel (controlled using a glycerol/water mixture). The thin part of the NLCh shell was easily ripped during UV curing without density matching. The thus-produced NLCsolid shells exhibited good swelling/shrinkage properties depending on the solvent quality and temperature, which could be further utilized for encapsulating/releasing Rhodamine 6G in/from the core of the NLCsolid shell. The pores in the NLCsolid shell (the size of which was controlled by the 5CB content of the RMM727/5CB mixture) were completely closed in a poor solvent and open in a good solvent. The encapsulation/release properties were studied based on the fluorescence intensity of encapsulated Rhodamine 6G. This study provides a method for preparing uniform-sized and robust NLCsolid shell membranes that can be used for several applications, such as in smart actuators, sensors, and parts of microelectromechanical systems.

An asymptotically exact theory of smart sandwich shells

An asymptotically exact two-dimensional theory of elastic-piezoceramic sandwich shells is derived by the variational-asymptotic method. The error estimation of the constructed theory is given in the energetic norm. As an application, analytical solution to the problem of forced vibration of a circular elastic plate partially covered by two piezoceramic patches with thickness polarization excited by a harmonic voltage is found.

Active structural acoustic control of a smart cylindrical shell using a virtual microphone

This paper investigates the active structural acoustic control of sound radiated from a smart cylindrical shell. The cylinder is equipped with piezoelectric sensors and actuators to estimate and control the sound pressure that radiates from the smart shell. This estimated pressure is referred to as a virtual microphone, and it can be used in control systems instead of actual microphones to attenuate noise due to structural vibrations. To this end, the dynamic model for the smart cylinder is derived using the extended Hamilton’s principle, the Sanders shell theory and the assumed mode method. The simplified Kirchhoff–Helmholtz integral estimates the far-field sound pressure radiating from the baffled cylindrical shell. A modified higher harmonic controller that can cope with a harmonic disturbance is designed and experimentally evaluated. The experimental tests were carried out on a baffled cylindrical aluminum shell in an anechoic chamber. The frequency response for the theoretical virtual microphone and the experimental actual microphone are in good agreement with each other, and the results show the effectiveness of the designed virtual microphone and controller in attenuating the radiated sound.

Linear and nonlinear free vibration of a multilayered magneto-electro-elastic doubly-curved shell on elastic foundation

Nonlinear and linear free vibration of symmetrically laminated magneto-electro-elastic doubly-curved thin shell resting on an elastic foundation is studied analytically. The shell is considered to be simply-supported on all edges and the magneto-electro-elastic body is poled along the z direction and subjected to electric and magnetic potentials between the upper and lower surfaces. To obtain the equations of motion, the Donnell shell theory in the presence of rotary inertia effect is used. Moreover, Gauss' laws for electrostatics and magnetostatics are used to model the electric and magnetic behavior. The nonlinear partial differential equations of motion are reduced to a single nonlinear ordinary differential equation by introducing a force function and using the single-term Galerkin method. The resulting equation is solved analytically by Lindstedt-Poincare perturbation method. After validation of the present study, several numerical studies are done to investigate the effects of foundation parameters, geometrical properties of the shell, and electric and magnetic potentials on the linear and nonlinear behavior of these smart shells.

Effect of multiphysics conditions on the behavior of an exponentially graded smart cylindrical shell with imperfect bonding

In the present study, a functionally graded cylindrical shell (FGM) with imperfectly surface bounded functionally graded piezoelectric material (FGPM) subjected to an axisymmetric hygrothermo-electro-mechanical loading and placed in a constant magnetic field is considered. The shell is simply supported and could be rested on an elastic foundation. The material properties of FGM and FGPM are assumed to be exponentially graded in the radial direction. The Fourier series expansion method through the longitudinal direction and the differential quadrature method across the thickness direction are used for solving governing differential equations. To check the validity of the present work, comparisons with the previous results are performed. Finally, numerical results are shown to clarify the effects of important parameters on the behavior of the smart shell. The multiphysics analysis is carried out to explore the effect of moisture, temperature, electric, and mechanical loadings as well as magnetic field on the behavior of the hybrid shell.

A finite element formulation for smart piezoelectric composite shells: Mathematical formulation, computational analysis and experimental evaluation

A formulation of a smart shell finite element for laminated curved structures with piezoelectric layers working under either the d31 or d33 effects has been developed in order to simulate dynamic tests. The electrical domain was modeled using a first order theory for the electrical field and a layer-wise approach. The mechanical domain is modeled using a degenerated shell theory with implicit curvature, considering a first order shear deformation theory and an equivalent single layer approach. The final formulation was implemented within Abaqus™ commercial finite element analysis package using its User Element (UEL) subroutine. First, some results provided by the proposed formulation were compared to numerical analyses shown by the literature. Second, the implemented finite element was evaluated using modal and frequency domain experiments for a cantilever aluminum beam with two piezoelectric transducers working under the d31 effects, and a free-free curved composite plate with four piezoelectric transducers working under the d33 effects. Comparisons between the natural frequencies and the frequency response functions amplitudes obtained from the experiments and the computational analyses were performed in order to discuss the limitations and potentialities of the proposed formulation.

Hygrothermal analysis of a rotating smart exponentially graded cylindrical shell with imperfect bonding supported by an elastic foundation

In the present study, a rotating functionally graded cylindrical shell (FGM) with imperfectly surface bounded functionally graded piezoelectric material (FGPM) subjected to an axisymmetric hygrothermo-electro-mechanical loading is considered. The shell is simply supported and could be rested on an elastic foundation. The material properties of FGM and FGPM are assumed to be exponentially graded in the radial direction. The Fourier series expansion method through the longitudinal direction and the differential quadrature method (DQM) across the thickness direction are used for solving governing differential equations. To check the validity of the present work, comparisons with the previous results are performed. Finally, numerical results are shown to clarify the effects of important parameters on the behavior of the smart shell.