Shape Memory Alloy Hybrid Research Articles

Experimental and numerical investigation on the macroscopic mechanical behavior of shape memory alloy hybrid composite with weak interface

This paper presents an experimental and numerical investigation into the macroscopic mechanical behavior of shape memory alloy hybrid composites (SMAHCs) subjected to quasi-static loading taking into account of weak interface effect and damage evolution. SMA fiber reinforced hybrid laminates were fabricated by vacuum assisted resin injection (VARI). Scanning electron microscopy was used to evaluate the quality of SMA–matrix interface. Uniaxial tensile tests were performed to study the effects of weak interface on the effective modulus of hybrid composite. Failure morphology was discussed based on the observation using digital HF microscope. Owing to the embedding of SMA fiber, the material exhibited a bilinear mechanical behavior, and the overall stiffness of composite at the second stage was lower on average 32.7% than that of the first stage. Ultimate strength was improved by 3.4% for the three-SMA-fiber composite, and rupture elongation was slightly decreased (∼0.1%). A script program was developed to generate the hybrid composite model by using ANSYS Parameter Design Language (APDL). Uniaxial tensile test was simulated using finite element method to study the macroscopic behavior of hybrid composite based on a bilinear cohesive zone model (BCZM). The effects of embedded SMA fiber number and fiber ratio were respectively discussed.

Repeated Instant Self-healing Shape Memory Composites

We present a shape memory composite which is made of two types of shape memory materials, namely shape memory alloy (SMA) and shape memory hybrid. This composite has repeated instant self-healing function by means of not only shape recovery but also strength recovery (over 80%). The activation of the self-healing function is triggered by joule heating the embedded SMA.

Review of biomimetic underwater robots using smart actuators

In this paper, biomimetic underwater robots built using smart actuators, e.g., a shape memory alloy (SMA), an ionic polymer metal composite (IPMC), lead zirconate titanate (PZT), or a hybrid SMA and IPMC actuator, are reviewed. The effects of underwater environment were also considered because smart actuators are often affected by their external environment. The characteristics of smart actuators are described based on their actuating conditions and motion types. Underwater robots are classified based on different swimming modes. We expanded our classification to non-fish creatures based on their swimming modes. The five swimming modes are body/caudal actuation oscillatory (BCA-O), body/caudal actuation undulatory (BCA-U), median/paired actuation oscillatory (MPA-O), median/paired actuation undulatory (MPA-U), and jet propulsion (JET). The trends of biomimetic underwater robots were analyzed based on robot speed (body length per second, BL/s). For speed per body length, robots using an SMA as an actuator are faster than robots using an IPMC when considering a similar length or weight. Robots using a DC motor are longer while their speeds per body length are similar, which means that robots using smart actuators have an advantage of compactness. Finally, robots (using smart actuators or a motor) were compared with underwater animals according to their speed and different swimming modes. This review will help in setting guidelines for the development of future biomimetic underwater robots, especially those that use smart actuators.

Nonlinear finite element analysis of shape memory alloy (SMA) wire reinforced hybrid laminate composite shells

This study introduces a non-linear finite element analysis approach to the procedure of modeling hybrid laminate composite shells with embedded shape memory alloy (SMA) wire subjected to coupled structural and thermal loading. Numerical analyses of SMA wire reinforced composite laminates were carried out by synergizing the non-linear laminate shell element with Brison's model of the SMA constitutive law. To verify the proposed procedure, the present illustrative applications involve rectangular laminated panels clamped along one side. Analysis results were compared with corresponding experimental results from a prior study. Several test cases that depend on the volume fraction of SMA, temperature, and ply angles are presented to illustrate the highly entangled thermo-mechanical behavior of shape memory alloy hybrid composites (SMAHCs). The results of the numerical analysis show the ability of the suggested procedure to compute the thermo-mechanical behavior of a SMAHC in accordance with the SMA's internal phase transformations induced by stress and temperature variation and demonstrate very good agreement with experimental results.

Seismic performance of concrete columns reinforced with hybrid shape memory alloy (SMA) and fiber reinforced polymer (FRP) bars

Lack of corrosion resistance of structural steel has resulted in many structural failures. Fiber reinforced polymer (FRP) bar is emerging as a viable solution to replace steel to mitigate corrosion problems. Since FRP is a brittle material, it can bring about catastrophic sudden structural failures. Conversely, post-earthquake recovery of structures is another prime objective for performance based seismic design. Shape memory alloy (SMA) has the unique ability to undergo large inelastic deformation and regain its undeformed shape through stress removal. Here a hybrid reinforced concrete (RC) column configuration is presented in order to reduce permanent damages, and enhance its corrosion resistance capacity where the plastic hinge region will be reinforced with SMA or stainless steel and the remaining regions with FRP or stainless steel rebar. An analytical investigation has been carried out to develop such hybrid RC columns and analyze them under seismic loadings. The results are compared in terms of base shear-tip displacement, base shear demand/capacity ratio, ductility, residual displacement, and energy dissipation capacity to those of a similar RC column reinforced with stainless steel. The results indicate that such corrosion resistant hybridized column can substantially reduce the residual displacement with adequate energy dissipation capacity during earthquakes.

Effects of shape memory alloys on low velocity impact characteristics of composite plate

The effects of shape memory alloy thin films embedded in composite plates for improving damage resistance of composite structures under low velocity impact were investigated numerically. Analysis model for SMA thin film was developed based on Lagoudas’ model and implemented using the user defined material subroutine of the ABAQUS/Explicit finite element program. Composite damage model based on the Chang–Chang failure criteria was also implemented to consider progressive damage behavior. The finite element simulation of low velocity impact behavior of a shape memory alloy hybrid composite plate was performed using the ABAQUS/Explicit program. Parametric studies were performed to investigate the effect of shape memory alloys for improving damage resistance of composite plate.

Optimal design of a variable-twist proprotor incorporating shape memory alloy hybrid composites

The tiltrotor blades, or proprotor, act as a rotor in the helicopter mode and a propeller in the airplane mode. The helicopter mode generally requires relatively a low built-in twist angle, whereas in the airplane mode, a high built-in twist is desired. Meeting these rather conflicting requirements make the tiltrotor design a challenging task. This paper explores an optimal design of a variable-twist proprotor that changes the built-in twist in an adaptive manner by using the shape memory alloy hybrid composite (SMAHC). The optimum design problem attempts to find the cross-section internal layout that maximizes the twist actuation of the variable-twist proprotor while satisfying a series of design constraints. An optimum design framework is constructed in the current work by combining various analysis and design tools, such as an active composite cross-sectional analysis, a nonlinear flexible multibody dynamics analysis, a 3-D strain analysis, and a gradient-based optimizer. The MATLAB is used to integrate and synthesize the individual tools. A static tip twist is chosen as an objective function that should be maximized for the best performance. The optimum results exhibit that the twist actuation of the variable-twist proprotor can be maximized while satisfying all the prescribed design constraints.

Nonlinear Finite Element Analysis of the Bending of Shape Memory Alloy Hybrid Epoxy Beams

On the basis of considering the thermo-viscoelasticity of the epoxy matrix, the geometrically nonlinear finite element formulation is developed to simulate the moderate deflection bending of the shape memory alloy (SMA) hybrid beam upon actuation of SMA. It is found that the midpoint deflection of the epoxy beam increases with increasing temperature when temperature is lower than the austenite start temperature of SMA. Once the austenite start temperature of SMA is reached, the midpoint deflection of the epoxy beam is rapidly decreased to the initial state with the increasing of temperature. And then it increases slowly with increasing temperature after the austenite phase transformation of SMA is finished. The results based on the geometrically nonlinear finite element analysis are also compared with those from the geometrically linear finite element analysis, which shows that they agree well with each other when the bending deflection of the epoxy beam is small, while significant discrepancies occur between them when the deflection is considerably large.

Fabrication and Thermo-Mechanical Characterization of a Shape Memory Alloy Hybrid Composite

Shape memory alloy (SMA) elements embedded in a structure allow to control the structural properties, thanks to their coupled thermo-mechanical behavior. In this study, the manufacturing and the shape control abilities of glass fiber/polyester resin SMA hybrid composites (SMAHCs) were experimentally investigated. Mechanical and calorimetric characterizations of SMA were carried out and correlated to the thermo-mechanical behavior of the SMAHC. The SMAHC was manufactured by the Vacuum Infusion Process that uses dry fibers and liquid matrix for the composite production. A polyester resin having a curing temperature lower than the SMA Austenite transition temperature was chosen as matrix, so a blocking system for the SMA wires was not needed during the cure. The thermo-mechanical behavior of the SMAHC was investigated by monitoring the shape change of the plate during heating of the embedded wires. The results give some indications on the appropriate characterization and choice of materials for SMAHC manufacturing.

Characterization of a shape memory alloy hybrid composite plate subject to static loading

In this manuscript the design process of a SMA wire-reinforced hybrid composite (SMAHC) plate is introduced in detail. The influence of various parameters on the overall behavior of the SMAHC plate is discussed. These parameters include: the mechanical behavior of the constituents (i.e. the host composite and SMA), the SMA volume fraction, the temperature dependent loading effects and the fabrication process. For that, a series of SMAHC plates were fabricated and tested under monotonic loading condition. The characteristics curves and formula for assessing the effect of the SMA at different temperatures are presented. It would be demonstrated that the embedment of SMA wires could improve the overall structural response of the host material in terms of stiffness and strength at elevated temperatures. Also capability of the one dimensional constitutive models in predicting the macroscopic stress–strain behavior of SMAHC plates is verified experimentally.

Design and analysis of variable-twist tiltrotor blades using shape memory alloy hybridcomposites

The tiltrotor blade, or proprotor, acts as a rotor in the helicopter mode and as a propellerin the airplane mode. For a better performance, the proprotor should have different built-intwist distributions along the blade span, suitable for each operational mode. This paperproposes a new variable-twist proprotor concept that can adjust the built-in twistdistribution for given flight modes. For a variable-twist control, the present proprotoradopts shape memory alloy hybrid composites (SMAHC) containing shape memory alloy(SMA) wires embedded in the composite matrix. The proprotor of the KoreaAerospace Research Institute (KARI) Smart Unmanned Aerial Vehicle (SUAV),which is based on the tiltrotor concept, is used as a baseline proprotor model.The cross-sectional properties of the variable-twist proprotor are designed tomaintain the cross-sectional properties of the original proprotor as closely aspossible. However, the torsion stiffness is significantly reduced to accommodatethe variable-twist control. A nonlinear flexible multibody dynamic analysis isemployed to investigate the dynamic characteristics of the proprotor such as naturalfrequency and damping in the whirl flutter mode, the blade structural loads ina transition flight and the rotor performance in hover. The numerical resultsshow that the present proprotor is designed to have a strong similarity to thebaseline proprotor in dynamic and load characteristics. It is demonstrated thatthe present proprotor concept could be used to improve the hover performanceadaptively when the variable-twist control using the SMAHC is applied appropriately.

Thermal buckling and nonlinear flutter behavior of shape memory alloy hybrid composite plates

A new nonlinear finite element model is provided for the nonlinear flutter response of shape memory alloy (SMA) hybrid composite plates under the combined effect of thermal and aerodynamic loads. The nonlinear governing equations for moderately thick rectangular plates are obtained using first-order shear-deformable plate theory, von Karman strain-displacement relations and the principle of virtual work. To account for the temperature dependence of material properties, the thermal strain is stated as an integral quantity of thermal expansion coefficient with respect to temperature. The aerodynamic pressure is modeled using the quasi-steady first-order piston theory. Newton-Raphson iteration method is employed to obtain the thermal post-buckling deflection, while the linearized updated mode method is implemented in predicting the limit-cycle oscillation at elevated temperatures. Numerical results are presented to show the thermal buckling and flutter characteristics of SMA hybrid composite plates, illustrating the effect of the SMA volume fraction and pre-strain value on the aero-thermo-mechanical response of such plates.

Active shape change of an SMA hybrid composite plate

An experimental study was carried out to investigate the shape control of plates via embedded shape memory alloy (SMA) wires. An extensive body of literature proposes the use of SMA wires to actively modify the shape or stiffness of a structure; in most cases, however, the study focuses on modeling and little experimental data is available. In this work, a simple proof of concept specimen was built by attaching four prestrained SMA wires to one side of a carbon fiber laminate plate strip. The specimen was clamped at one end and tested in an environmental chamber, measuring the tip displacement and the SMA temperature. At heating, actuation of the SMA wires bends the plate; at cooling deformation is partially recovered. The specimen was actuated a few times between two fixed temperatures <TEX>$T_c$</TEX> and <TEX>$T_h$</TEX>, whereas in the last actuation a temperature <TEX>$T_f$</TEX> > <TEX>$T_h$</TEX> was reached. Contrary to most model predictions, in the first actuation the transformation temperatures are significantly higher than in the following cycles, which are stable. Moreover, if the temperature <TEX>$T_h$</TEX> is exceeded, two separate actuations occur during heating: the first follows the path of the stable cycles; the second, starting at <TEX>$T_h$</TEX>, is similar to the first cycle. An interpretation of the phenomenon is given using some differential scanning calorimeter (DSC) measurements. The observed behavior emphasizes the need to build a more comprehensive constitutive model able to include these effects.

Design and analysis of braced frames with shape memory alloy and energy-absorbing hybrid devices

A hybrid seismic device that provides both energy-absorbing and re-centering capabilities to overcome external forces is developed and evaluated. The hybrid device is composed of three main components: (1) a set of re-centering wires fabricated from shape memory alloy (SMA) material, (2) two energy-absorbing struts, and (3) two high-strength steel tubes to guide the movement of the hybrid device. The SMA wires are located within the guiding high-strength steel tubes and designed to be sufficiently long such that their deformation strain is within the 6% target strain limit. A conservative value of 6% strain, instead of 8%, or 10%, is adopted to (1) avoid the SMA stiffening phase that increases strength up to 5 times that of its forward transformation yield forces, resulting in a serious damage to the adjacent structural members, and (2) to retain the full re-centering capability of the SMA wires even when the hybrid device is under large displacement. The energy-absorbing struts are pin-connected outside of the guiding steel tubes and may be fabricated of mild steel or low strength aluminum. To reduce the possibility of buckling in the energy-absorbing struts when subjected to compression, they are designed to be stocky and seismically compact, or buckling restrained. An optimal proportion of the SMA wires and energy-absorbing struts is formulated such that the hybrid device retains re-centering capability, while maximizing energy dissipation. Results obtained through the seismic analysis reveal that the hybrid braced frame system exhibits a similar energy dissipation capacity to the buckling restrained braced system, while also having excellent re-centering capabilities.

Aerothermoacoustic Response of Shape Memory Alloy Hybrid Composite Panels

theacousticexcitationisconsideredtobeawhite-Gaussianrandompressurewithzeromeananduniformmagnitude over the panel surface. Nonlinear temperature-dependence of material properties is considered in the formulation. The dynamic nonlinear equations of motion are transformed to modal coordinates to reduce the computational efforts. The Newton–Raphson iteration method is employed to obtain the dynamic response at each time step of the Newmark numerical integration scheme. Finally, the nonlinear response of a shape memory alloy hybrid composite panel is presented, illustrating the effect of shape memory alloy fiber embeddings, aerodynamic pressure, sound pressure level, and temperature rise on the panel response.

Coupled Deflection Analysis of SMA Fiber Hybrid Composite Active Blade

The constitutive equations relating cross-sectional loads(forces and moments)to cross-sectional displacements(stretching, bending, twisting) of thin-walled laminated beams with integral shape memory alloy (SMA)active fibers was presented. The variational asymptotic method was used to formulate the force- deformation relationships equations, accounting for the presence of active SMA fibers distributed along the cross-section of the beam. The constitutive relationships for evaluation of the properties of a hybrid SMA composite ply were obtained following the rule of mixtures. The analytical expressions of the actuation components for the active beam were derived based on Tanaka’s constitutive equation and Lin’s linear phase transformation kinetics for SMA fiber. The general form of constitutive relation was applied to the case of stretching-twist coupling, corresponding to Circumferentially Uniform Stiffness (CUS). The present analysis extended the previous work done for modeling generic passive thin-walled laminated beams. Numerical results shown that significant stretching and twisting deflection occur during the phase transformation due to SMA actuation. The effects of temperature on structural response behavior during phase transformation from martensite to austenite are significant. The effects of the volume fraction of the SMA fiber, the martensitic residual strain and ply angle were also addressed

Limit-Cycle Oscillation of Shape Memory Alloy Hybrid Composite Plates at Elevated Temperatures

A traditional composite plate impregnated with pre-strained shape memory alloy fibers and subject to combined thermal and aerodynamic loads is investigated to demonstrate the effectiveness of using the SMA fiber embeddings in improving the static and dynamic response of composite plates. The problems investigated can be categorized into: thermal buckling subject to aerodynamic loading, linear flutter boundary at elevated temperatures, nonlinear flutter limit-cycle, and chaotic oscillations at elevated temperatures. A nonlinear finite element model based on the von Karman strain displacement relations and first-order shear deformable plate theory is derived. Aerodynamic pressure is modeled using the quasi-steady first-order piston theory. The governing equations are obtained using the principle of virtual work based on thermal strain being a cumulative physical quantity. Newton-Raphson iteration is employed to obtain the static aero-thermal large deflection at each temperature step and the dynamic response at each time step of the Newmark numerical integration scheme. A frequency domain solution is presented for predicting the flutter boundary at elevated temperatures, while the time domain method along with modal transformation is applied to numerically investigate periodic, non-periodic, and chaotic limit-cycle oscillations. The results show that the critical buckling temperature of the plate is greatly increased, and hence the thermal post-buckling deflection is suppressed by using SMA fiber embeddings. The SMA fiber embeddings caused an increase in the critical dynamic pressure at elevated temperatures, and enlargement of the static flat and dynamically stable region of the panel.

Structural modeling of SMA fiber hybrid active thin-walled composite beams

Abstract The constitutive equations relating cross-sectional loads (forces and moments) to cross-sectional displacements (stretching, bending, twisting) of thin-walled laminated beams with integral shape memory alloy (SMA) active fibers is presented. The variational asymptotic method is used to formulate the force-deformation relationships equations accounting for the presence of active SMA fibers distributed along the cross-section of the beam. The constitutive relationships for evaluation of the properties of a hybrid SMA composite ply are obtained following the rule of mixtures. The analytical expressions of the actuation components for the active beam are derived based on Tanaka’s constitutive equation and Lin’s linear phase transformation kinetics for SMA fiber. The general form of constitutive relation is applied to the cases of extension-twist coupling, corresponding to Circumferentially Uniform (CUS) and bending-twist coupling, corresponding to Circumferentially Anti-Symmetric (CAS). The present analysis extends the previous work done for modeling generic passive thin-walled laminated beams. Numerical results show that significant extension, bending and twisting deflection occur during the phase transformation due to SMA actuation. The effects of temperature on structural response behavior during phase transformation from martensite to austenite are significant. The effects of the volume fraction of the SMA fiber, the martensitic residual strain and ply angle are also addressed.

Thermal Buckling and Flutter Behavior of Shape Memory Alloy Hybrid Composite Shells

A new nonlinear finite element formulation is presented to predict the thermal buckling and flutter boundaries of shape memory alloy hybrid composite cylindrical panels at elevated temperatures. The governing equations are obtained using Marguerre curved-plate theory and the principle of virtual work. The effect of large deflection is included in the formulation through the von Karman nonlinear strain-displacement relations. To account for the temperature dependence of material properties, the thermal strain is stated as an integral quantity of the thermal expansion coefficient with respect to temperature. The aerodynamic pressure is modeled using the quasi-steady first-order piston theory. The Newton―Raphson iteration method is employed to obtain the nonlinear thermal postbuckling deflections, and a frequency-domain solution is presented to predict the critical dynamic pressure at elevated temperatures. Numerical results are presented to illustrate the effect of shape memory alloy fiber embeddings, temperature rise, height-to-thickness ratios, and boundary conditions on the panel response.

Aero-thermo-mechanical characteristics of imperfect shape memory alloy hybrid composite panels

A nonlinear finite element model is provided to predict the static aero-thermal deflection and the vibration behavior of geometrically imperfect shape memory alloy hybrid composite panels under the combined effect of thermal and aerodynamic loads. The nonlinear governing equations are obtained using Marguerre curved plate theory and the principle of virtual work taking into account the temperature-dependence of material properties. The effect of large deflection is included in the formulation through the von Karman nonlinear strain–displacement relations. The thermal load is assumed to be a steady-state constant-temperature distribution, whereas the aerodynamic pressure is modeled using the quasi-steady first-order piston theory. The Newton–Raphson iteration method is employed to obtain the nonlinear aero-thermal deflections, while an eigenvalue problem is solved at each temperature step and static aerodynamic load to predict the free vibration frequencies about the deflected equilibrium position. Finally, the nonlinear deflection and free vibration characteristics of a composite panel are presented, illustrating the effects of geometric imperfection, temperature rise, aerodynamic pressure, boundary conditions and shape memory alloy fiber embeddings on the panel response.