Shape Memory Alloy Volume Fraction Research Articles

Computational Modeling and Parametric Analysis of SMA Hybrid Composite Plates under Thermal Environment.

This paper presents a coupled thermoelastic finite element formulation for static and dynamic analysis of composite laminated plates with embedded active shape memory alloy (SMA) wires, which accounts for both the phase transformation and the nonlinearity effects of SMA wires. The equations of motion are obtained by using Hamilton's principle and first-order shear deformation theory (FSDT). Furthermore, based on Brinson's one-dimensional phase transformation constitutive law, a novel coupled thermoelastic finite element model that enables analysis of the SMA hybrid composite (SMAHC) plate is developed. The accuracy and efficiency of the developed computational model for analysis of SMAHC plates are reinforced by comparing theoretical predictions with data available from the literature. The results of the numerical examples also show the ability of the proposed model to predict the thermal-mechanical behavior of SMAHC plates in accordance with SMA's hysteresis behavior. In addition, based on the proposed model, the influence of temperature as well as SMA volume fraction, pre-strain value, boundary condition and layup sequence on the static bending and free vibration behavior of the SMAHC plates is investigated in detail. The results of parametric analysis show that the variations of both static deflection and natural frequency of the SMAHC plate over temperature exhibit a nonmonotonic behavior.

A simple and efficient analytical model for the natural frequencies of sandwich plates made of flexible core and composite face sheets with embedded pre‐strained shape memory alloy wires

AbstractTwo main goals are followed in the present work. The first objective is the development of a simple analytical model based on piecewise low‐order shear deformation theory (PLSDT) for the natural frequencies of sandwich plates made of flexible core with temperature‐dependent mechanical properties and laminated composite face sheets with embedded pre‐strained shape memory alloy (SMA) wires. Brinson's model is applied in this research to estimate the recovery stress produced by SMAs. A comparative study is performed to show the ability of the proposed model to offer high solution accuracy at low computational costs. Specifically, the results of the present research exhibit less than a 2% difference from those obtained from the mixed LW/ESL models in the framework of Carrera's unified formulation (CUF). As the second goal, the influences of some parameters such as the pre‐strain of SMAs, the volume fraction of SMAs, and core thickness on the fundamental frequencies of SMA‐reinforced sandwich plates are examined. The results reveal that depending on the geometric parameters and operating temperature, SMAs may have constructive or destructive effects on the free vibration of sandwich plates.

Development of a torsional theory for radially functionally graded porous shape memory alloy circular bars

This work develops a novel torsional theory for a radially functionally graded (FG) porous shape memory alloy (SMA) circular bar. Prior to the theoretical development, the effective three-dimensional (3D) phenomenological constitutive model for SMAs with high porosity is proposed. To help derive successfully the theory, the pure shear-driven material parameters in the effective model are expressed in the cubic polynomial. Subsequently, the torsional theory for radially FG porous SMA circular bar is derived considering the evolution of effective phase evolution in the bar. This phase evolution consideration guarantees the accuracy of the developed theory. Indeed, the soundness of effective constitutive model is confirmed by 3D finite element method (FEM) simulation of porous SMA structure in Abaqus using the well-established ZM’s model for dense SMAs. Specifically, the simulating results in terms of the shear stress-shear strain response obtained from two prediction methods considering a variation of SMA volume fraction and temperature are in good agreement. Furthermore, accuracy of torsional theory is validated by 3D FEM simulation using the 3D effective constitutive model with a good agreement observed. It is found that the superelasticity of the bar can be enhanced by increasing the gradient index and decreasing the temperature and wall thickness.

Analytical model of shape memory alloy embedded smart beam, under actuated condition

Vibration characteristics of actuated Shape Memory Alloy (SMA) embedded smart composite beam are studied and it is extended to reduce the impact of resonance in cantilever beams. Smart composite beam with SMA embedded at neutral layer is studied for its vibrational characteristics under martensite and austenite conditions. The smart beam is developed as a analytical model incorporating the change in Young's modulus and damping factor under martensite and austenite conditions of SMA. The variation of natural frequency and damping are evaluated and verified with experimentation at different volume fraction of SMA. The thermo elastic nature of SMA and GFRP incorporated in the numerical model depicts the shift in natural frequency of 10% and reduction in magnification factor of 50% under actuation conditions. The frequency response of the smart beam depicts the capability of SMA in active vibration control and improvement of the structural health of composite beam. The thermo mechanical analytical model derived can be utilized to optimize the volume fraction of SMA to be embedded. The study can be extended to optimize actuation current to minimize the effect of resonance.

Analytical study of thermal buckling and post-buckling behavior of composite beams reinforced with SMA by Reddy Bickford theory

Shape memory alloys are used in composite structures due to their shape memory effect and phase transformation. The recovery force of the shape memory alloy improves the post-buckling behavior of the structure. In this study, the thermal buckling and post-buckling of Shape Memory Alloy (SMA) hybrid composite laminated beam subjected to uniform temperature distribution is investigated. To this purpose, considering Von-Karman non-linear strain terms for large deformation, the non-linear equations of SMA reinforced beam based on Reddy Bickford theory have been derived. Besides, the recovery stress of the restrained SMA wires during martensitic transformation was calculated based on the one-dimensional constitutive law of the Brinson’s model. A numerical solution using Galerkin’s method has been presented for solving the nonlinear partial differential equations to obtain the critical buckling temperature and transverse deformation of the beam in the post-buckling region in both symmetric and anti-symmetric layups. The effect of SMA volume fraction, pre-strain, the boundary condition of the beam, stacking sequence, and its geometric properties have been studied. The results show that even by adding a small amount of SMA to the composite, the critical buckling temperature increases significantly, and the beam deflection decreases. Besides, using this theory has an evident effect on the anti-symmetric layup, especially for the thick beams.

Thermal post buckling analysis of smart SMA hybrid sandwich composite plate

Thermal post-buckling analysis of smart sandwich plates has been presented with the incorporation of shape memory alloy (SMA) and shape memory polymer (SMP) in laminated composite structure under uniform temperature distribution. Buckling analysis is based on higher order shear deformation theory (HSDT) with von Karman nonlinearity by finite element method (FEM). Evaluation of critical buckling temperature has been performed under the action of inplane uniform temperature distribution for different boundary conditions, plate’s aspect and thickness ratio, modulus ratio, ply orientations of smart SMA hybrid sandwich composite plate. Shape memory alloys itself acting uniquely under temperature variation and with SMA reinforced SMP laminated composite plate this phenomenon extended further under dynamic temperature condition for thermal buckling behavior. Also SMA with different strain rate and variation in SMA volume fraction is also presented to understand the cumulative buckling behavior.

Cumulative post-buckling buckling behavior of smart sandwich structure

Cumulative post-buckling buckling behavior of smart sandwich structure has been presented with the combination of shape memory alloy (SMA) and shape memory polymer (SMP) in sandwich composite structure under uniform temperature distribution. The analysis is based on higher order shear deformation theory (HSDT) with von Karman nonlinearity by finite element method (FEM). Evaluation of nondimensional critical buckling temperature (NCBT) has been executed under varying plate thickness ratio. Thermal buckling performance of SMA reinforced SMP laminated composites under dynamic temperature condition with different strain rate and variation in SMA volume fraction is also presented first time to understand the cumulative post-buckling behavior.

Post-buckling nonlinear analysis of sandwich laminated composite plate

Thermal post-buckling analysis of sandwich composite plates has been presented with the incorporation of shape memory alloy (SMA) under uniform temperature distribution by higher order shear deformation theory (HSDT) with von Karman nonlinear kinematics by finite element method (FEM) in MATLAB environment. The validity of the present utilized model is checked by performing validation study also convergence study has been done to select the mesh size to compute the results without affecting the results. Study clearly defines effect of layer variation, layup sequence, uniform temperature variation, and aspect ratio under different boundary conditions (BC) over nondimensional critical buckling temperature (NCBT). Study also clearly indicate the effect of the SMA volume fraction under different ply sequence over NCBT of sandwich composite plate.

Viscoelastic behavior of epoxy resin reinforced with shape-memory-alloy wires

The effect of NiTi alloy long wires on the viscoelastic behavior of epoxy resin was investigated by utilizing the dynamic mechanical analysis (DMA) and a novel micromechanical model. The present model is capable of predicting the viscoelastic properties of the shape-memory-alloy (SMA) reinforced polymer as a function of the SMA volume fraction, initial martensite volume fraction, pre-strain level in wires, and the temperature variations. The model was verified by conducting experiments. Good agreement between the theoretical and experimental results was achieved. A parametric study was also performed to investigate the effect of SMA parameters. According to the results, by the addition of a small volume fraction of SMA, the storage modulus of the composite increases significantly, especially at higher temperatures. Moreover, applying a 4% pre-strain caused a 10% increase in the maximum value of the loss factor of the SMA reinforced epoxy in comparison with the 0% pre-strained SMA reinforced epoxy.

Thermo-mechanical modeling and characterization of three-phase shape memory alloy hybrid composites

The thermo-mechanical properties of shape memory alloy hybrid composites (SMAHCs) are characterized, and their three-phase constitutive relationship in the form of a lamina embedded with shape memory alloy (SMA) wires is established by micromechanics. Considering large beam deflection, a theoretical bending model of SMAHC beams with different fiber volume fractions and arbitrary ply schemes is proposed. The Runge–Kutta method is employed to solve the nonlinear ordinary differential equations, and the quantitative relations of curvature, rotation and deflection under thermal load are obtained from the model by directly using the original three-phase material parameters without the need of the experimental measurement in single layer. The SMAHC beams with different fiber orientation, number of layers, and volume fraction of SMA are fabricated, and their thermo-mechanical behavior is experimentally evaluated. Good agreements between the theoretical predictions and experimental results demonstrate that the proposed model is capable of predicting the thermo-mechanical behavior of three-phase SMAHC beams. The generic model developed can be used as an analytical tool in design analysis and optimization of SMAHC structures for effective shape, tracking, and vibration control.

On the free vibration and design optimization of a shape memory alloy hybrid laminated composite plate

A shape memory alloy (SMA) is a temperature-dependent smart material that can be used to tune the stiffness of structures in a thermal environment. In the present article, vibrations of hybrid laminated composite plates reinforced with shape memory alloy fibers under temperature change are studied. Parametric free vibration analysis is conducted to study the effect of the SMA volume fraction, SMA fibers prestrain, length-to-width ratio, and thickness-to-length ratio on the fundamental natural frequency and critical thermal buckling temperature of the hybrid plate subject to fully clamped and fully simply supported boundary conditions. With the objective of maximizing the fundamental natural frequency of the hybrid plate, for the first time, simultaneously, the optimum stacking sequence of the hybrid plate and the best layers to embed the shape memory alloy fibers are found. Interestingly, the study shows that the notion of embedding SMA fibers in the composite plate does not guarantee an increase in the fundamental natural frequency. Depending on the stacking sequence and the layers in which the SMA fibers are embedded, adverse effects might happen. It is shown that inserting the SMA fibers in layers close to the mid-plane maximizes the fundamental natural frequency of the plate.

Effect of shape memory alloys on the mechanical properties of metallic glasses: A molecular dynamics study

The strength-plasticity trade-off of metallic glass (MG) has not still been effectively overcome. The introduction of shape memory alloy (SMA) is an effective way to improve the mechanical properties of MG. Here, the deformation behavior of amorphous/SMA Cu64Zr36/B2-CuZr nanomultilayers (ASNMs) under tension loading is investigated by molecular dynamics (MD) simulation method. The results show that the peak stresses and flow stress of the ASNMs are greater than those of the monolithic MG regardless of SMA volume fraction. The martensitic transformation (MT) in the SMA phase limits the propagation of shear bands (SBs), avoids a runaway instability, and simultaneously induces plastic strain strengthening. The results also indicate that the plastic deformation mode of ASNMs changes from the interaction of multiple SBs dominated to finally brittle fracture caused by nano-pores aggregation with the increase of SMA volume fraction. This means that the plasticity and strength of ASNMs can be significantly improved by adjusting the volume fraction of SMA. The fruits stem from this paper may provide a valuable guidance and theory route for the design of high-performance MGs.

Sound Radiation of Orthogonal Antisymmetric Composite Laminates Embedded with Pre-Strained SMA Wires in Thermal Environment

The interest of this article lies in the sound radiation of shape memory alloy (SMA) composite laminates. Different from the traditional method of avoiding resonance sound radiation of composite laminates by means of structural parameter design, this paper explores the potential of adjusting the modal peak of the resonant acoustic radiation by using material characteristics of shape memory alloys (SMA), and provides a new idea for avoiding resonance sound radiation of composite laminates. For composite laminates embedded with pre-strained SMA, an innovation of vibration-acoustic modeling of SMA composite laminates considering pre-stain of SMA and thermal expansion force of graphite-epoxy resin is proposed. Based on the classical thin plate theory and Hamilton principle, the structural dynamic governing equation and the frequency equation of the laminates subjected to thermal environment are derived. The vibration sound radiation of composite laminates is calculated with Rayleigh integral. Effects of ambient temperature, pre-strain, SMA volume fraction, substrate ratio, and geometrical parameters on the sound radiation were analyzed. New laws of SMA material and pre-strain characteristics on sound radiation of composite laminates under temperature environment are revealed, which have theoretical and engineering functional significance for vibration and sound radiation control of SMA composite laminates.

Free and forced vibration analysis of a sandwich beam considering porous core and SMA hybrid composite face layers on Vlasov’s foundation

This paper aims to investigate the free and forced vibration behavior of a sandwich beam with functionally graded porous core and composite face layers embedded with shape memory alloy (SMA). Three different porosity patterns are assumed through the thickness direction of the core, and composite face layers are reinforced with carbon nanotubes (CNT). The sandwich beam is resting on an elastic foundation which is simulated by Vlasov’s model. By using Hamilton’s principle and first-order shear deformation theory, the governing equations of motion are derived. The analytical solution is presented to solve the equations of motion using Navier’s solution. Results are verified with corresponding literatures. Finally, the effects of important parameters such as temperature, volume fraction of SMA, porosity distribution, weight fraction of CNT, and geometric parameters are explored in detail.

Nonlinear dynamics of earthquake-resistant structures using shape memory alloy composites

Earthquake-resistant structures have been widely investigated in order to produce safe buildings designed to resist seismic activities. The remarkable properties of shape memory alloys, especially pseudoelastic effect, can be exploited in order to promote the essential energy dissipation necessary for earthquake-resistant structures. In this regard, shape memory alloy composite is an idea that can make this application feasible, using shape memory alloy fibers embedded in a matrix. This article investigates the use of shape memory alloy composites in a one-story frame structure subjected to earthquakes. Different kinds of composites are analyzed, comparing the influence of matrix type. Both linear elastic matrix and elastoplastic matrix with isotropic and kinematic hardening are investigated. Results indicate the great energy dissipation capability of shape memory alloy composites. A parametric analysis allows one to conclude that the maximum shape memory alloy volume fraction is not the optimum design condition for none of the cases studied, highlighting the necessity of a proper composite design. Despite the elastoplastic behavior of matrix also dissipates a considerable amount of energy, the associated residual strains are not desirable, showing the advantage of the use of shape memory alloys.

Bending and buckling analysis of sandwich Reddy beam considering shape memory alloy wires and porosity resting on Vlasov's foundation

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov\'s foundation. To this end, first, displacement field\'s equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier\'s analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

Effect of Shape Memory Alloy Wires on the Buckling Behavior of Fiber Metal Laminates

Buckling behavior of shape memory alloy (SMA) reinforced fiber metal laminates (FML) was experimentally investigated. The SMA reinforced FML specimens with three different pre-strain levels (1, 2 and 3 %) and different number of the embedded wires (2, 4 and 6 wires) were prepared by a specific mold and hydraulic pressure. The effects of the applied pre-strains in the SMA wires, as well as the stacking sequence of the laminate, SMA volume fraction and the location of the wires were studied on the axial and lateral force-displacement diagrams for the specimens during buckling tests. According to the results, 53 % enhancement in the buckling load was obtained for 2 SMA wires reinforced FML specimens in comparison with the specimens without embedded SMA wires. In constant volume fraction of the SMA, pre-straining the wires by 3 % led to 25 % improvement in the buckling load, in comparison with the specimens reinforced with 1 % pre-strained wires. The influence of the FML stacking sequence on the results was also discussed.

Thermal vibration analysis of SMA hybrid composite double curved sandwich panels

This work analyses the thermal vibration of a double curved sandwich panel (DCSP) with embedded pre-strained shape memory alloy (SMA) wires hybrid composite face sheets and soft core. The von Karman nonlinear displacement–strain relationships are here applied to handle large deflections due to a thermal loading. The equations of motion are derived by applying the Hamilton’s principle and the first order shear deformation theory (FSDT) for the composite face sheets and core layer. This last one features the displacement field of the Frostig's second model here, used to model the DCSP. The material properties of the DCSP are assumed to be both temperature-dependent (TD) and/or temperature-independent (TI). The effect of the SMA wires is captured by adding a stress recovery within the formulation. This term is determined by using a one-dimensional Brinson’s model in the constitutive equations of the SMA composite face sheets during the phase transformation of the pre-strained SMA wires. It is verified that SMAs can play a key role within DCSPs subjected to a thermal loading condition, whereby the proposed formulation is validated comparatively against the available literature. We also explore the sensitivity of the vibration response for a varying SMA activation temperature, volume fraction, and pre-strain, as well as for different curvature ratios, thickness ratios and different sequences in composite layers.

Buckling and post-buckling responses of smart doubly curved composite shallow shells embedded in SMA fiber under hygro-thermal loading

In this research, the post-buckling behaviors of doubly curved composite shells in hygro-thermal environment are investigated by employing multiple scales perturbation method. Three-phase composites shells with polymer/Carbon nanotube/fiber and polymer/Graphene platelet/fiber (PGF) and Shape Memory Alloy (SMA)/matrix according to Halpin-Tsai model are taken into consideration. The displacement-strain of laminated doubly curved shells via third-order shear deformation theory (TSDT) and using von-Kármán nonlinear shell theory is obtained. The governing equations of shallow shell are derived by implementing Hamilton's principle. For investigating correctness and accuracy, this paper is validated with other previous researches. Finally, different parameters such as volume fraction of SMA, temperature rise, various distribution patterns, aspect and curvature ratios are considered in this article. It is found that these parameters have significant effect on the thermal buckling loading.

Nonlinear free and forced vibration analysis of multiscale composite doubly curved shell embedded in shape-memory alloy fiber under hygrothermal environment

In this research, nonlinear free and forced vibration behaviors of the multiscale doubly curved composite shells have been investigated. By using Reddy's third-order shear deformation theory (TSDT) and von-Karman type nonlinearity the strains and stresses are obtained. Three-phase composites shells with polymer/carbon nanotube/fiber and polymer/graphene platelet/fiber and shape-memory alloy (SMA)/matrix according to the Halpin–Tsai model have been analyzed. The governing equations of composite shell have been derived by implementing Hamilton's principle, and according to the multiple scales perturbation method have been solved. The obtained results are validated through the comparison with the available results. Finally, the effects of different parameters such as volume fraction of SMA, temperature rise, various distributions pattern, aspect, and curvature ratio considered on nonlinear frequency have been studied. The results indicate that the changes of the fundamental vibrational mode shape have a significant influence on the nonlinear frequency of the composite shell.