Morphed Shape Research Articles

Shape-retaining beam-like morphing structures via localized snap through

In this study, we present a concept of morphing structure – featuring an arch mounted on a compliant base – that can be reconfigured via snap-through buckling and leverages bistability to retain its morphed shape. We show that one-dimensional arrays of such units yield beam-like structures that, upon localized snapping, can attain multiple, morphologically distinct stable shapes. Units are modeled using discrete elastic rods, a reduced-order formulation for beams and beam structures, and the results are validated via experiments. We leverage our model to understand the influence of the geometrical design parameters on the response and final shape of a unit. We then show that the morphed shapes of arrays of units can be predicted by concatenating results of simulations on single units, and leverage this idea to inverse-design structures that can be snapped into target stable shapes. Ultimately, our work suggests an up-scalable way to create shape-retaining morphing structures with target stable shapes.

Hydrogen‐Bonded Liquid Crystal Elastomers Combining Shape Memory Programming and Reversible Actuation

AbstractMaterials that undergo shape morphing in response to external stimuli have numerous applications, e.g., in soft robotics and biomedical devices. Shape memory polymers utilize kinetically trapped states to, typically irreversibly, transfer between a programmed morphed shape and an equilibrium shape. Liquid crystal elastomers (LCEs), in turn, can undergo reversible actuation in response to several stimuli. This study combines the irreversible and reversible shape morphing processes to obtain LCEs that undergo shape‐programming via the shape memory effect and subsequent reversible actuation of the programmed shape. This is enabled by an LCE crosslinked via dynamic hydrogen bonds that break at high temperatures and reform upon cooling, endowing the shape memory effect, while mild thermal or photothermal stimulation yields the reversible actuation. Through this combination, proof‐of‐concept robotic application scenarios such as grippers that can adjust their shape for grabbing different‐sized objects and crawling robots that can morph their shape to adapt to constrained spaces, are demonstrated. It is anticipated that this work adds new diversity to shape‐programmable soft microrobotics.

Frequency memorizing shape morphing microstrip monopole antenna using hybrid programmable 3-dimensional printing

Four-dimensional printing is expected to help greatly assist many industries due to its unique ability to create self-morphing structures that react to external stimuli without human intervention. Nevertheless, it is currently limited to structural mechanics due to lacking integration with other technologies. In particular, the electronics industry strongly requires new materials for reconfigurable electronics since current active components have many drawbacks. This paper proposes frequency memorizing microstrip monopole antennas (MMAs) realized by hybrid programmable 3D printing using an inkjet to print onto shape morphing 3D printed material. Self-shape morphing electronics overcome limitations from passive structures or requiring additional morphing systems. Electromagnetic performance for the proposed hybrid-printed microstrip line was experimentally verified depending on the morphed shape (bent, wave, or twist). The proposed frequency memorizing MMA achieved 25.9 dB return loss at 3.43 GHz in the initial MMA (mode I). Resonance frequency reduced from 3.43 to 3.0 and 2.3 GHz for modes II and III, respectively. The programmed shape morphing MMA also successfully returned to the memorized initial stat, thus the MMA could provide functional and deployable systems with wireless connectivity in human inaccessible areas.

Experimental evaluation of the aerodynamic performance of a large-scale high-lift morphing wing

The Smart Morphing & Sensing (SMS) project was a multi-disciplinary upstream project that investigated the use of intelligent electro-active actuators to modify the lifting surface of an aircraft. In particular, the attention of the project was focused on trailing-edge, high-lift morphing devices aimed to obtain the optimal shapes to improve the aerodynamic performance of the wing of a large passenger aircraft. The present work describes the experimental assessment of the morphed aerodynamic shapes of the high-lift morphing flap developed during the project. Wind-tunnel tests were performed using a large-scale wing prototype reproducing a section of a full-scale wing of a large passenger aircraft. Several quantities were measured during the tests. Pressure measurements performed in the mid-span section of the wing showed an increase of the lift provided by the cambered morphed shape of the flap in take-off configuration and an increase of both the lift coefficient and the wing efficiency in landing configuration. Particle Image Velocimetry surveys enabled us to obtain an insight in the flow physics behind the measured performance of the morphing flap. Moreover, the deformation of the morphing flap was measured by optical systems to check the actual shape. The tests demonstrated that morphing the trailing-edge flap can be useful to optimise the aerodynamic performance of the wing during take-off and landing.

A Shape Optimization Method for Part Design Derived from the Buildability Restrictions of the Directed Energy Deposition Additive Manufacturing Process

The design methodologies and part shape algorithms for additive manufacturing (AM) are rapidly growing fields, proven to be of critical importance for the uptake of additive manufacturing of parts with enhanced performance in all major industrial sectors. The current trend for part design is a computationally driven approach where the parts are algorithmically morphed to meet the functional requirements with optimized performance in terms of material distribution. However, the manufacturability restrictions of AM processes are not considered at the primary design phases but at a later post-morphed stage of the part’s design. This paper proposes an AM design method to ensure: (1) optimized material distribution based on the load case and (2) the part’s manufacturability. The buildability restrictions from the direct energy deposition (DED) AM technology were used as input to the AM shaping algorithm to grant high AM manufacturability. The first step of this work was to define the term of AM manufacturability, its effect on AM production, and to propose a framework to estimate the quantified value of AM manufacturability for the given part design. Moreover, an AM design method is proposed, based on the developed internal stresses of the build volume for the load case. Stress tensors are used for the determination of the build orientation and as input for the part morphing. A top-down mesoscale geometric optimization is used to realize the AM part design. The DED Design for Additive Manufacturing (DfAM) rules are used to delimitate the morphing of the part, representing at the same time the freeform mindset of the AM technology. The morphed shape of the part is optimized in terms of topology and AM manufacturability. The topology optimization and AM manufacturability indicator (TMI) is introduced to screen the percentage of design elements that serve topology optimization and the ones that serve AM manufacturability. In the end, a case study for proof of concept is realized.

Computational design optimization of a smart material shape changing building skin tile

The development and evaluation of a computational approach for optimal design of a smart material shape changing building skin is presented and numerically evaluated. Specifically, a unique shape-based approach is utilized to create an optimization approach to identify the activation and actuation mechanisms to minimize the difference between a desired shape and the estimated morphed shape. Three potential metrics of shape difference are considered and their capability to facilitate an efficient optimization process leading to accurate shape matching is evaluated. Details of the optimal design framework are presented, particularly focusing on the shape difference metrics as well as the strategy to parameterize the activation of the smart material. In particular, the parameterization strategy is a unique approach to easily integrate controllable localized activation within a smart material structure in a generally applicable way that does not limit the design search space. A series of numerical design examples are presented based on the concept of a smart material (e.g., shape memory polymer) shape changing tile that can be activated and actuated in a variety of ways to achieve desirable surface wrinkle patterns. These numerical design examples are applied to both 2D and 3D problems and consider a variety of parameterizations and target shapes. Results indicate that the shape-based approach can consistently determine the mechanisms of morphing needed to accurately match a target shape. Furthermore, it is shown that localized material activation can lead to not only a more accurate shape but also requires less energy and actuation devices to do so.

Experimental evaluation of a morphing leading edge concept

This article presents an experimental evaluation of a morphing leading edge demonstrator by investigating its morphed shape, the level of induced strains in the airfoil skin, the actuation force, and the morphing mechanism’s capability to lock and transfer the applied loads. In addition, a finite element model of the demonstrator is assembled comprising an elastic morphing skin and a kinematic morphing mechanism. The obtained results are used to assess whether the demonstrator performs according to the design objectives, such as the target shape, the character of the morphing deformation and the morphing mechanism locking, applied during the design process. The comparison between experimental and numerical results yielded a good agreement in terms of observed morphed shape and pertaining strains. The average difference in morphed shape was less than 0.08% chord at the maximum actuator extension. The observed difference in the respective strains was less than 400 micro-strains. A significant difference, up to 70%, was observed in the actuation force, which was attributed to the modelling assumptions and to the force measurement technique employed in the experiment. Nevertheless, both results show good qualitative agreement showing similar trends.

Finding the optimal shape of the leading-and-trailing car of a high-speed train using design-by-morphing

We present a new, general design method, called design-by-morphing for an object whose performance is determined by its shape due to hydrodynamic, aerodynamic, structural, or thermal requirements. To illustrate the method, we design a new leading-and-trailing car of a train by morphing existing, baseline leading-and-trailing cars to minimize the drag. In design-by-morphing, the morphing is done by representing the shapes with polygonal meshes and spectrally with a truncated series of spherical harmonics. The optimal design is found by computing the optimal weights of each of the baseline shapes so that the morphed shape has minimum drag. As a result of optimization, we found that with only two baseline trains that mimic current high-speed trains with low drag that the drag of the optimal train is reduced by $$8.04\%$$8.04% with respect to the baseline train with the smaller drag. When we repeat the optimization by adding a third baseline train that under-performs compared to the other baseline train, the drag of the new optimal train is reduced by $$13.46\%$$13.46%. This finding shows that bad examples of design are as useful as good examples in determining an optimal design. We show that design-by-morphing can be extended to many engineering problems in which the performance of an object depends on its shape.

A SMA-based morphing flap: conceptual and advanced design

In the work at hand, the development of a morphing flap, actuated through shape memory alloy load bearing elements, is described. Moving from aerodynamic specifications, prescribing the morphed shape enhancing the aerodynamic efficiency of the flap, a suitable actuation architecture was identified, able to affect the curvature. Each rib of the flap was split into three elastic elements, namely cells, connected each others in serial way and providing the bending stiffness to the structure. The edges of each cell are linked to SMA elements, whose contraction induces rotation onto the cell itself with an increase of the local curvature of the flap airfoil. The cells are made of two metallic plates crossing each others to form a characteristic X configuration; a good flexibility and an acceptable stress concentration level was obtained non connecting the plates onto the crossing zone. After identifying the main design parameters of the structure (i.e. plates relative angle, thickness and depth, SMA length, cross section and connections to the cell) an optimization was performed, with the scope of enhancing the achievable rotation of the cell, its ability in absorbing the external aerodynamic loads and, at the same time, containing the stress level and the weight. The conceptual scheme of the architecture was then reinterpreted in view of a practical realization of the prototype. Implementation issues (SMA - cells connection and cells relative rotation to compensate the impressed inflection assuring the SMA pre-load) were considered. Through a detailed FE model the prototype morphing performance were investigated in presence of the most severe load conditions.

2412 CADデータフィッティングメッシュモーフィング技術の開発(OS3 デジタルエンジニアリング)

We developed a mesh morphing technique, which can be used to change the shape of existing analytical mesh models, and generated a mesh model for a new shape by morphing the mesh model for the previous one. Therefore, our method is suitable to use for analysis during the early stage of design because it reduces the amount of time required to generate analytical mesh models. However, this technique is impossible to morph a free-form surface, and to change surface type. Therefore, we developed the fitting morphing technique for solving the problem. This technique is possible to morph based on specification of the STL data as morphed shape and indication of fitting nodes and movable nodes. We confirmed that this technique can be morphed to free-form surface from cylindrical surface by application to the piston head model in 2 seconds. Futhermore, the technique can be morphed to maintain the boundary of the shape by application to the gear model.

Design of morphing winglets with the inclusion of nonlinear aeroelastic effects

AbstractA nonlinear aeroelastic model capable of assessing arbitrary morphing manoeuvres and calculating the associated morphing energy requirement is presented in this paper. The aeroelastic model consists of a close coupling between a corotational beam element, accounting for geometric nonlinearities, and a Weissinger method aerodynamic model, containing the Prandtl-Glauert correction for high-subsonic Mach numbers. The morphing deformations are discretised into three distinct morphing modes; fold morphing, twist morphing, and shear morphing, because of which virtually any morphed shape can be achieved, given a proper distribution of the three modes over the wing. The proposed aeroelastic morphing framework is used to design morphing winglets, and it has been shown that morphing winglets can improve the performance of fixed winglets significantly for regional airliners.

Bio-inspired wing morphing for unmanned aerial vehicles using intelligent materials

Biologically inspired engineering or Biomimicry is the practice of developing designs and technologies inspired by nature. This conscious use of examples from nature is a form of applied case-based reasoning thus treating nature itself as a database of solutions that have survived for millions of years-survival of the fittest. Inspired by nature, we have developed aircraft wings that imitate the amazing flight of birds. This bio-inspired effort, which is the result of a collaborative research program with Defence Science Organisation National Laboratories of Singapore, is concerned with the design and development of a novel wing prototype for unmanned aerial vehicles (UAVs) that morphs seamlessly without the use of complex hydraulics and/or servo motors. The novel design, selected from a number of designs, is characterised by a high degree of flight adaptability, enhanced manoeuvrability and improved performance with a limited added weight. These characteristics were attained through the use of shape memory alloys as actuators in an antagonistic fashion. Unlike compliant actuators that require continued input of thermal energy, antagonistic setup does not suffer from this difficulty. This is because they require the thermal energy to deform the wing but not to maintain its morphed shape. Structural analysis based upon safety factors specified by FAR23 standards and aerodynamic analysis using FLUENT were conducted on the novel designs to validate their suitability as viable wings for UAVs. In addition, conditioning of the shape memory actuators was conducted using a specially designed circuitry that imposes the appropriate heating and cooling cycles at set periodic times. The outcome of this study is manifest in the new designs that satisfy the missions of different UAVs.

Lift-to-drag ratio and laminar flow control of a morphing laminar wing in a windtunnel

A new hardware-in-the-loop control strategy to enhance the aerodynamicperformance of a two-dimensional morphing laminar wing prototype was developedand tested. The testing was performed in a wind tunnel under cruise flight flowconditions: Mach number ranging from 0.2 to 0.3 and angle of attack from − 1° to0.5°. For each set of flow conditions, the shape of the upper surface of the wing was modifiedusing two independent shape memory alloy actuators. The wing shape was morphed in twosequential steps. The initial morphed shape was controlled using open-loop architectureand the results of an anterior aero-structural numerical optimization study. The finalmorphed shape was closed-loop controlled using either the wind tunnel balance or aninfrared camera as hardware-in-the-loop to give an instantaneous lift-to-drag ratio (L/D) or a laminarflow extension (xtr/c) over the upper surface of the prototype. In respect to theaerodynamic performance of the unactuated wing profile, theL/D gain varies from 10.6 to 15% for the closed-loop control strategy compared to10.0 to 13.7% for the open-loop control strategy. Laminar flow extension gains,Δxtr/c, measured by infrared camera, were situated in the 29–33% range for both controlstrategies. However, the results obtained showed that the closed-loop controller could behindered by the noise of the hardware-in-the-loop signal.

A Novel SMA-based Concept for Airfoil Structural Morphing

The adaptive structures concept is of great interest in the aerospace field because of the several benefits which can be accomplished in the fields including noise reduction, load alleviation, weight reduction, etc., at a level in which they can be considered as compulsory in the design of future aircraft. Improvements in terms of the aerodynamic efficiency, aeroelastic behavior, stability, and manoeuvrability performance have already been proved through many international studies in the past. In the family of the Smart Materials, Shape Memory Alloys (SMA) seem to be a suitable solution for many static applications. Their high structural integrability in conjunction with actuation capabilities and a favorable performance per weight ratio, allows the development of original architectures. In this study, a morphing wing trailing edge concept is presented; morphing ability was introduced with the aim of replacing a conventional flap device. A compliant rib structure was designed, based on SMA actuators exhibiting structural potential (bearing external aerodynamic loads). Numerical results, achieved through a FE approach, are presented in terms of trailing edge induced displacement and morphed shape.