Integration Of Shape Memory Alloys Research Articles

Designing a Morphing Wing for Fixed-Wing UAVs By IJISRT

This project report details the original conceptualization, design, and analysis of a morphing wing structure for fixed-wing Unmanned Aerial Vehicles (UAVs). Our approach incorporates an octahedron cell structure coupled with the application of shape memory alloys(SMAs) to facilitate controlled wing morphing. The primary goal is to augment the UAVs aerodynamic efficiency and adaptability to various flight conditions. The octahedron cell structure is employed as the foundational framework, providing a balance between structural integrity andflexibility for shape adjustments. The integration of shape memory alloys, known for their reversible phase transformations, enables precise and efficient control over the morphing process. Through this combination, we aim to optimize the UAVs flight characteristics, including improved efficiency, stability, and maneuver ability. To validate the feasibility and performance of the morphing wing design, Finite Element Analysis (FEA) has been conducted. This computational approach allows for a comprehensive evaluation of the structural integrity and aerodynamic behavior of the morphing wing under diverse loading conditions. The FEAresults offer crucial insights into the structural response, stress distribution, and deformation patterns, guiding the iterative refinement of the design for optimal functionality. This project represents a unique contribution to UAV technology, presenting an original perspective on morphing wing design that harnesses the benefits of octahedron cell structureand shape memory alloys. The insights gained from the FEA analysis provide valuable guidance for the ongoing development and implementation of morphing wing structures in fixed- wing UAVs. This work sets the stage for improved adaptability and performance in a range of operational scenarios, without reliance on external sources or existing research

A highly integrated shape memory alloy actuator and precision self-sensing tracking control based on position compensation

Shape memory alloy (SMA) actuators are widely used in various actuators due to their advantages of simplicity, high strength, and flexibility. The mapping relationship between the resistance change and displacement during the phase transition process of SMA enables its self-sensing control without external displacement sensors. However, the limited accuracy and high complexity of existing self-sensing models are two crucial factors restricting the wide application of self-sensing control. Due to the high nonlinearity of the SMA wire’s phase transition process, it is challenging to achieve accurate position estimation using a simple self-sensing model. Thus, this paper proposes a novel approach by utilizing the simplest linear model for position estimation. The inevitable modeling errors are directly compensated in the final control results, rather than compensating for estimation errors. This significantly reduces the implementation difficulty of SMA self-sensing control and effectively improves control accuracy. Furthermore, a highly integrated prototype of SMA actuator is designed in this paper, where the additional position sensor and self-resetting loading device are integrated, greatly reducing the size of the SMA actuator. A series of self-sensing tracking experiments are conducted on this prototype, validating that the compensated self-sensing control can achieve comparable performance to the control method with external sensors.

Analysis of low velocity impact response of glass fiber reinforced epoxy resin composite with shape memory alloy incorporation

The current article investigates about degradation of lightweight materials in aircraft structural components resulting from low-velocity impacts, a common cause of failure. Although subsonic collisions do not cause immediate external damage to the structure, they significantly reduce the material's stiffness and impact strength. The study explores the performance of intelligent hybrid thermoplastic composite plates subjected to low-speed impacts, both numerically and experimentally. Particularly, the behavior of laminated composites with integrated shape memory alloy (SMA) fibers is discussed in this study. SMA wires are inserted into the composite laminate fabric layer located on the intermediate planes. The study revealed that incorporating SMA fibers increases the damage tolerance and stiffness of the laminated composites compared to standard composite structures. The compounds exhibit a noticeable increase in hardness and energy levels before failure.

Design and fabrication of shape memory alloy based 4D-printed actuator for FWMAV: A performance study

Flapping Wing Micro Aerial Vehicles (FWMAVs) use flapping wings to create lift and thrust, akin to bird flight. In this work, we seek to design and fabricate a Shape Memory Alloy (SMA) based 4D-printed actuator that behaves as a wing structure to achieve the desired flapping action in an FWMAV. The integration of SMA in the static matrix facilitates the desired motion by bending SMA as a response to a stimulus. The properties of SMA such as the work density, stroke angle, etc., are greatly enhanced in contrast to more complex, conventional motor-driven mechanisms. The study includes the investigation of the actuator's performance, which is evaluated using image processing based on parameters such as the stroke angle, actuation speed, and recovery force, and helps in utilizing the actuator based on the needs and demands of specific targeted applications by referring to the baseline data recorded by conducting a series of experiments.

Hinged Adaptive Fiber-Rubber Composites Driven by Shape Memory Alloys-Development and Simulation.

Adaptive structures based on fiber-rubber composites with integrated Shape Memory Alloys are promising candidates for active deformation tasks in the fields of soft robotics and human-machine interactions. Solid-body hinges improve the deformation behavior of such composite structures. Textile technology enables the user to develop reinforcement fabrics with tailored properties suited for hinged actuation mechanisms. In this work, flat knitting technology is used to create biaxially reinforced, multilayer knitted fabrics with hinge areas and integrated Shape Memory Alloy wires. The hinge areas are achieved by dividing the structures into sections and varying the configuration and number of reinforcement fibers from section to section. The fabrics are then infused with silicone, producing a fiber-rubber composite specimen. An existing simulation model is enhanced to account for the hinges present within the specimen. The active deformation behavior of the resulting structures is then tested experimentally, showing large deformations of the hinged specimens. Finally, the simulation results are compared to the experimental results, showing deformations deviating from the experiments due to the developmental stage of the specimens. Future work will benefit from the findings by improving the deformation behavior of the specimens and enabling further development for first applications.

Experimental and Numerical Analysis of the Deformation Behavior of Adaptive Fiber-Rubber Composites with Integrated Shape Memory Alloys.

Fiber-reinforced rubber composites with integrated shape memory alloy (SMA) actuator wires present a promising approach for the creation of soft and highly elastic structures with adaptive functionalities for usage in aerospace, robotic, or biomedical applications. In this work, the flat-knitting technology is used to develop glass-fiber-reinforced fabrics with tailored properties designed for active bending deformations. During the knitting process, the SMA wires are integrated into the textile and positioned with respect to their actuation task. Then, the fabrics are infiltrated with liquid silicone, thus creating actively deformable composites. For dimensioning such structures, a comprehensive understanding of the interactions of all components is required. Therefore, a simulation model is developed that captures the properties of the rubber matrix, fiber reinforcement, and the SMA actuators and that is capable of simulating the active bending deformations of the specimens. After model calibration with experimental four-point-bending data, the SMA-driven bending deformation is simulated. The model is validated with activation experiments of the actively deformable specimens. The simulation results show good agreement with the experimental tests, thus enabling further investigations into the deformation mechanisms of actively deformable fiber-reinforced rubbers.

Autonomous camber morphing of a helicopter rotor blade with temperature change using integrated shape memory alloys

The present study proposes and explores a new autonomous morphing concept, where a 12–13° increase in camber is realized over a spanwise section of a helicopter rotor blade with increase in ambient temperature. The camber change is achieved through integration of Shape Memory Alloys (SMAs) on the lower surface of the blade, aft of the leading-edge spar. For a reference rotor of a utility-class helicopter generating 21,000 lbs thrust, a loss in lift of 2590 lb was observed due to operation in hot conditions. With the SMA camber morphing section extending from the blade root to 25%, 50%, and 75% span, the rotor recovered up to 11%, 43%, and 82% of the lift loss at high temperature (compared to a no-SMA blade). If the morphing section instead spans the outboard 25% of the blade (from 75% span to the blade tip), up to a 66% lift recovery is achieved due to the higher dynamic pressures over this region. While these results are achieved with existing SMA properties, idealized target values are also presented. For the SMA considered in the study, while a 40–115°F temperature change was required to achieve the full 12–13° design camber change, partial camber is achieved over a smaller temperature range. The paper identifies desired SMA properties that would produce a 12–13° camber change over an 80–100°F temperature change.

Modeling of integrated shape memory alloy and Macro-Fiber Composite actuated trailing edge

Owing to their high energy densities, smart materials like shape memory alloys (SMAs), Macro-Fiber Composites (MFCs) and, electroactive polymers (EAPs) have massive potential as actuators in wing morphing applications. In this article, a detailed numerical model is developed for the shape prediction of an elastic base that is actuated by a combination of a shape memory alloy (SMA) wire and a Macro-Fiber Composite (MFC) bimorph. It has been demonstrated using the model that it is possible to achieve large deflections at low frequencies by virtue of the phase transformations in the SMA wire and rapid actuation with small deflections due to the MFC bimorph. In the developed scheme, the elastic base is modeled using non-linear Euler-Bernoulli beam theory. The influence of the non-linear hysteresis in the SMA wire and the linear actuation characteristics of the MFC is studied by incorporating thermo-mechanical and electro-mechanical constitutive behavior into the non-linear beam theory. The system of coupled equations hence obtained, is solved iteratively to obtain the deflected shape of the elastic base. The results from the developed numerical scheme are validated against the previously available studies in the literature and experiments. Additionally, the synergistic advantage of using the two actuators together has been shown through experiments. As an illustration, a smart trailing edge camber morphing concept is developed by integrating the flexible elastic structure along with the two smart actuators to a NACA 0012 airfoil as the trailing edge.

Improving the stiffness of multilayer 3D woven composites by the integration of shape memory alloys (SMAs) into structures

Shape memory alloys (SMAs) are capable of shape-retaining and stress generation when activated. SMA wires are embedded in laminated composites for improving the properties of the composites. Laminated composites have low through-the-thickness properties and poor delamination resistance. 3D composites are well known for having higher through-the-thickness properties. In 3D woven composites, a set of yarn is in through-the-thickness direction that improves through-the- thickness properties and provides resistance to delamination of layers. As in multilayer 3D woven structures, yarns are distributed from in-plane to through-the-thickness direction, so in-plane properties are reduced with the same number of yarns compared to 2D laminated composites. In this research, SMA wires are embedded into different types of 3D woven structures for utilising stress generation property of SMA wires for improving in-plane properties, specifically stiffness of the composites. Three types of 3D orthogonal interlocking composites: layer-to-layer, through-the-thickness, and modified multilayer interlock structures are fabricated with and without SMA wires. From the tensile test, results show that embedding SMA wires into structures significantly improves the stiffness of the structures due to the stress-induced martensite phase of SMA wire when subjected to load. When these SMA wires are activated, stresses are generated by SMA wires due to phase transformation from martensite to austenite that further gives remarkable higher values of stiffness. This results in a composite structure that has higher in-plane properties due to embedded SMA wire and through-the-thickness properties due to 3D structure of composite reinforcement. The interlocking pattern in the through-the-thickness direction of 3D structures was also found to have an effect on the extent of the improvement in stiffness.

Review on fabrication and mechanical characterization of shape memory alloy hybrid composites

Metals are replaced by composites in various structural applications as composite possesses unique properties such as low weight, high specific strength, and stiffness. However, there is a need to enhance mechanical properties of composite structure. Therefore, hybridization of composite is required that can improve mechanical properties in different testing conditions. One method of fabricating hybrid composite is by reinforcing the shape memory alloy (SMA) in composite laminates. In spite of various advantages offered by the SMA, there is always a challenge in an integration of SMA with the composite for the hybridization. Mainly, these challenges offered during the fabrication process due to their incompatibility of matrix fiber, lack of bonding between SMA and polymer matrix, location of SMA in the composite, and curing temperature of composites. Different methods have been proposed by various researchers for reinforcing SMA into composite. The current review emphasizes the fabrication process of SMA hybrid composite (SMAHC), fractographic study using scanning electron microscopy (SEM) to detect interfacial bonding of SMA and polymer matrix and also the effect of SMA reinforcement on mechanical properties such as tensile, flexural, and impact.

Adaptive fiber-reinforced plastics based on open reed weaving and tailored fiber placement technology

The textile-technical integration of shape memory alloys into reinforcing fabrics for the development of adaptive fiber-reinforced plastics (FRPs) has been developed in recent years. This is aimed at reproduction, automation, and series production as well as reduced delamination of shape memory alloys in FRPs, and higher force transmission from shape memory alloys to FRPs. This type of integration can be executed in several ways, for example, by weaving or by tailored fiber placement technology. We present a comparative study of the functional properties of adaptive FRPs based on both types of technology. In order to conduct this study, functionalized reinforcing fabrics for the formation of adaptive FRPs were produced by open reed weaving and tailored fiber placement technology. Subsequently, they were infused by means of a thermosetting resin system. After the fabrication of adaptive FRPs, their functional properties were characterized and evaluated. Results show that the maximum deformation of adaptive FRPs produced by open reed weaving technology was higher than those produced by tailored fiber placement technology. Therefore, the adaptive FRPs produced by open reed weaving technology are more suitable for the formation of grippers, aerodynamically effective flaps, or robotic hands than that of adaptive FRPs produced by tailored fiber placement technology.

Integrated shape memory alloy devices toward a high-performance glazed curtain wall seismic retrofit

Recent dynamic events, such as Alaska and San Fernando earthquakes, have shown shortcomings in contemporary façade design processes, exacerbated by the occurrence of non-structural component damage and failure when subjected to extreme wind loads or seismic events. Accordingly, in the present work the feasibility of an original and advanced dissipation technology is pursued investigating on the façade performance by testing and modeling strategies.Initially, based on the experimental activities performed at the Construction Technologies Institute (ITC) laboratories of the Italian National Research Council (CNR), numerical simulations are run to interpret and reproduce the experimentally tested response of two full-scale façade units. Thereafter, sophisticated 3D finite element models are calibrated acquiring information on the fundamental mechanisms accountable for the dynamics in façades.Subsequently, by virtue of the peculiar properties of Shape Memory Alloys (SMA), such as superelasticity and shape memory effect, innovative curtain wall joints are designed, focusing on the improvement of the façade energy dissipation performance and on the enhancement of the overall structural behavior.Finally, the improvements are demonstrated both globally and locally: on one hand, traditional and novel curtain wall force-drift capacity curves are compared; on the other hand, the effectiveness of the suggested device is shown, when built on a reference structure.

Adaptive fiber-reinforced plastics based on open reed weaving functionalization

It is aimed at realizing adaptive, and thus mechanically adjustable fiber-reinforced plastic (FRP) components with complex 2D layouts so that complex 3D deformation of adaptive FRPs can be achieved. Therefore, the textile-technical integration of shape memory alloys into reinforcing fabrics is required. Hence, this paper presents the development of adaptive FRPs, where nickel-titanium-based shape memory alloy was structurally integrated into textile-reinforced semi-finished products by means of open reed weaving technology to generate adaptive FRP components. After manufacturing of the functionalized preform, it was infused by both a thermosetting resin system and a thermosetting system modified by means of plasticizer. Results of thermo-mechanical characterization revealed that the deformation of adaptive FRPs increased fourfold by adding the plasticizer to the reference thermosetting resin system.

Exploiting the instability of smart structure for reconfiguration

Aiming to verify the concept of using heteroclinic connections to reconfigure smart structures, a multistable buckled beam with integrated Shape Memory Alloy (SMA) wires is utilized as a high fidelity model. The Shape Memory Alloy (SMA) wires are resistively heated to provide the actuation force to stabilize the unstable configuration and the transition of the beam from one unstable equilibrium condition to the other. This concept provides a means of reducing the energy requirement for transitions between configurations of the structure, which is an energy-efficient reconfiguration scheme between equal-energy unstable (but actively controlled) equilibria. This letter presents a detailed design of the system, and how the active (heated) SMA wires control the structure stay in unstable configuration and drive the structure to achieve reconfiguration. Exploiting the instability of the smart structure has significant interests in many power reduction applications, including active flow control, reconfiguration of large deployable aerospace structures, and MEMS devices.

Development and testing of controlled adaptive fiber-reinforced elastomer composites

The integration of shape memory alloys (SMAs) into textile-reinforced composites produces a class of smart materials whose shape can be actively influenced. In this paper, Ni-Ti SMA wires are inserted during the weaving of a glass fiber reinforcement textile. This “active” reinforcement is then combined with an elastomeric matrix to produce a highly flexible composite sheet, which maintains high rigidity in the longitudinal direction. By activating the SMAs, high deflection ratios of up to 35% (relative to the component's length) are achieved. To adjust the composite's deflection to defined values, a closed-loop control is set up to adjust the current flow through the SMA wires. A control algorithm is designed and evaluated for several test cases. The high deformability and the controllable behavior show the high potential of these materials for applications such as aerodynamic flow control, automation and architecture.

Fiber-reinforced polymers with integrated shape memory alloy actuation: an innovative actuation method for aerodynamic applications

This contribution focuses on the application potential of active fiber-reinforced polymer (FRP) structures with integrated shape memory alloy (SMA) elements for new aerodynamic functions. The advantages of hybrid SMA FRP structures are highlighted, and promising application concepts are discussed. To illustrate the applicability of the technology, the developed manufacturing, design, and control approaches are presented. Main focus is the development of a new concept for an active aerodynamic airfoil and the realization of a hardware demonstrator. Beginning with the idea of an adaptive airfoil, able to bear an application relevant down force at a relatively high deflection, the design process starts with an evaluation of different actuation concepts. An SMA-powered cantilever is a part of the profile itself. Applying the finite-element method with a suitable model for the active hybrid material, an effective selection of material and design is possible. After manufacturing and assembling of the active hybrid airfoil, a comparison of experimental results and simulation is the first proof of success. Finally, the installation of an integrated hardware setup with power source, control, and the active hybrid structure, demonstrating actuation on demand, verifies the potential and the distinct advantages of the new approach using SMA FRP structures.

Review and perspectives: shape memory alloy composite systems

Following their discovery in the early 1960s, there has been a continuous quest for ways to take advantage of the extraordinary properties of shape memory alloys (SMAs). These intermetallic alloys can be extremely compliant while retaining the strength of metals and can convert thermal energy to mechanical work. The unique properties of SMAs result from a reversible diffussionless solid-to-solid phase transformation from austenite to martensite. The integration of SMAs into composite structures has resulted in many benefits, which include actuation, vibration control, damping, sensing, and self-healing. However, despite substantial research in this area, a comparable adoption of SMA composites by industry has not yet been realized. This discrepancy between academic research and commercial interest is largely associated with the material complexity that includes strong thermomechanical coupling, large inelastic deformations, and variable thermoelastic properties. Nonetheless, as SMAs are becoming increasingly accepted in engineering applications, a similar trend for SMA composites is expected in aerospace, automotive, and energy conversion and storage-related applications. In an effort to aid in this endeavor, a comprehensive overview of advances with regard to SMA composites and devices utilizing them is pursued in this paper. Emphasis is placed on identifying the characteristic responses and properties of these material systems as well as on comparing the various modeling methodologies for describing their response. Furthermore, the paper concludes with a discussion of future research efforts that may have the greatest impact on promoting the development of SMA composites and their implementation in multifunctional structures.

Influence of structural architecture on linear shape memory alloy actuator performance and morphing system layout optimisation

In this work, a design strategy is presented, addressed to adaptive structural systems, driven by shape memory alloy actuators. The peculiar behaviour of shape memory alloy materials, non-linear and fully dependent on three parameters (stress, strain and temperature), and the load path itself complicate the numerical simulation process. This is even more evident if those active elements are integrated within complex structures. Actuators generate forces. Integrated shape memory alloy–based structural actuator capability is strongly influenced by the hosting structure stiffness. It does in turn depend on the geometrical configuration. The structural architecture may be then said to modulate the performance of the aforementioned devices. The layout modifies in fact the structural resistance that opposes the action of a generic shape memory alloy actuator, even if the same topological point is referred to. This opposition affects the change of phase process (martensite ↔ austenite) regulating shape memory alloy peculiar phenomena and then impacts its performance. For simple, linear shape memory alloy actuators, the structure may be represented as an oriented spring where all the information of the parent structure is concentrated in its scalar stiffness property. This value is a function of the specific layout. A way to compute this equivalent structural stiffness comes directly by its definition: the ratio between the generated actuation force and the derived homologue structural displacement, that is, displacement occurring along the same force direction. Because such stiffness is what the shape memory alloy actuator feels, in this article it is referred as ‘perceived stiffness’. In this article, the structural layout effect on linear shape memory alloy actuator performance is initially evaluated for a simple spring. The approach is then extended to a complex active structural system, element of an aircraft wing morphing architecture. The referred device is capable of deforming wing regions while resisting the aerodynamic and the structural loads and recovering the original shape, once the actuation stops. Structural actuator geometry is optimised as a function of the attained structural displacement (figure of merit). The work is concluded with a discussion on the achieved results, namely, rotation, vertical displacement, internal stress (strain) levels and activation temperature.

Modular Optoelectronic Microfluidic Backplane for Fluid Analysis Systems

We report on the development of backplane modules with integrated microvalves and optical switches enabling custom-made system design of analysis systems. The backplane modules are reversibly interconnected by magnetostatic connectors and provide optical and fluidic coupling to four neighboring backplane modules and one optical sensor module, which is mounted on top. This concept allows for selectively guiding fluids and light to the sensor modules to be operated. We integrated shape memory alloy (SMA) microvalves in different designs and two kinds of optical switches, i.e., one linearly actuated assembly of optical elements and one based on an electrostatically deflectable mirror. We manufactured the modules in polymers and carried out optical and fluidic characterization. The functionality of the backplane is demonstrated by interconnecting two optical sensor modules with integrated spectrometer and photodiode color sensor, respectively. Herewith, we carried out fluorescence transmission experiments.

Optimization and integration of shape memory alloy (SMA)-based elastic actuators within a morphing flap architecture

Aircraft morphing architectures are currently worldwide investigated to enhance performance while reducing weights, volumes and costs. A 3-flap wing, for instance, shall pay a penalty up to 100% due to the insertion of mechanical devices in its body. Moreover, the insertion of cover nacelles disturbs the wing aerodynamics itself. In addition, flapped wings are noisy: deformable, instead of slotted and flapped wings, may lead to significant enhancement also in this field. Within Joint European Initiative on Green Regional Aircraft frame, in cooperation with the University of Naples, Department of Aerospace Engineering, the authors with their colleagues came to the definition of dedicated morphing architectures. This paper focuses on the design and optimization of a morphing architecture based on Shape Memory Alloy (SMA) technology, aimed at increasing airfoil trailing edge curvature. The deformable rib system is constituted of four elastic elements. The aerodynamic loads were computed through a classical panel method for the most severe flight condition. The descriptive finite element model underwent an optimization process performed through a proprietary code, based on a genetic selection strategy. Resulting values, from the optimization study were different for the variables referring to each subsystem: plate thickness, depth and length, relative orientation, SMA ribbons thickness, depth and location. Trailing edge vertical displacement was assumed as target. The main features of the 4 elastic elements are presented in the body of the document. As expected, the more rearward is the element position, the less is the weight and size; decreasing values of the aerodynamic load led towards lighter solutions.