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Morphing structures can allow significant improvements in performance by optimally changing shape across varying conditions. A critical barrier to the design of morphing structures is the challenge of determining how optimal shape changes as a function of the many operating conditions that affect optimality. Traditional engineering optimization techniques are able to determine an optimal shape only for one condition or an aggregation over operating conditions (i.e., optimizing average performance). Parametric optimization is an alternative approach that can solve a family of related optimization problems simultaneously. Herein the authors analyze the design of a structurally consistent camber morphing wing for light aircraft applications using parametric optimization techniques. The approach combines rigorous consideration of structural constraints via Class/Shape Transformation (CST) equations and use of a C1-continuous analytical representation of wing outer mold line geometry with the Predictive Parametric Pareto Genetic Algorithm (P3GA), an algorithm for nonlinear multi-parametric optimization. The system is tuned to maximize lift-to-drag ratio, a key metric for aircraft flight range. Kriging-based interpolation is applied to P3GA output to obtain an optimal solution map determining optimal shape variable values as a function of flight conditions (airspeed, angle of attack, and altitude). Solutions obtained from iterated use of traditional optimization techniques are utilized to benchmark the more novel and efficient parametric optimization accuracy. Results show that parametric optimization is useful for optimizing morphing structures across a range of operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and characterization of a self-foldable Active Origami Reflector Antenna (AORA) of parabolic form. Self-folding of the AORA is enabled by smooth uncreased folds composed of shape memory polymer (SMP) composites. Design methods for origami with smooth folds are applied to determine the shape and fold pattern of a planar sheet that can be folded to reach the parabolic antenna shape. A proof-of-concept prototype of the AORA is fabricated and self-folding of the AORA driven by thermal actuation of the SMP composite folds is demonstrated. The far-field electromagnetic (EM) characteristics of the AORA prototype are investigated through numerical simulations and experimental measurements in an anechoic chamber. A design-of-experiment study is conducted to investigate the effects of the antenna shape parameters on its EM characteristics such as far-field antenna gain and beamwidth, and to compare the performance of the AORA to that of equivalent smooth and faceted parabolic reflectors. Applications of the AORA include high-gain directional radio telescopes and satellite telecommunication. [ABSTRACT FROM AUTHOR]

Because of the continuous variability of the ambient environment, all aircraft would benefit from an in situ optimized wing. This paper proposes a method for preliminary design of feasible morphing wing configurations that provide benefits under disparate flight conditions but are also each structurally attainable via localized active shape change operations. The controlled reconfiguration is accomplished in a novel manner through the use of shape memory alloy embedded skin components. To address this coupled optimization problem, multiple sub-optimizations are required. In this work, the optimized cruise and landing airfoil configurations are determined in addition to the shape memory alloy actuator configuration required to morph between the two. Thus, three chained optimization problems are addressed via a common genetic algorithm. Each analysis-driven optimization considers the effects of both the deformable structure and the aerodynamic loading experienced by the wing. Aerodynamic considerations are addressed via a two-dimensional panel method and each airfoil shape is generated by the so-called class/shape transformation methodology. It is shown that structurally and aerodynamically feasible morphing of a modern high-performance sailplane wing produces a 22% decrease in weight and significantly increases stall angle of attack and lift at the same landing velocity when compared to a baseline design that employs traditional control surfaces. [ABSTRACT FROM AUTHOR]

Engineers routinely perform parameter studies to investigate how system response changes over a range of parameter values. This can provide engineering insight into the importance of an exogenous variable, the robustness of a design alternative, or even the validity of simulation models. Parametric optimization is an extension of this concept in which one investigates how the solution to an optimization or equilibrium problem changes over a range of parameter values. It has been applied in economics, process engineering and engineering systems design. Recent work has yielded a general-purpose algorithm for parametric multi-objective optimization, the Predicted Parametric Pareto Genetic Algorithm (P3GA), and demonstrated it on engineering examples. This article advances understanding about the capabilities of P3GA through a suite of test problems of varying scale and application to a multiphysical engineered system: a magnetohydrodynamic thermal transport (MTT) system. We also compare P3GA to iterated application of an established multi-objective optimization algorithm, NSGA-II. Results indicate P3GA outperforms the iterative approach, underscoring the importance of using an algorithm tailored to parametric optimization. [ABSTRACT FROM AUTHOR]

Developing novel techniques for monitoring structural integrity has become an important area of research in the aerospace community. One new technique exploits the stress-induced phase transformation behavior in shape memory alloy particles embedded in a structure. By monitoring changes in the mechanical and/or electromagnetic behavior of such particles, the formation or propagation of fatigue cracks in the vicinity of these particles can be detected. This work demonstrates sensory particle response to local structural damage using finite element modeling for the first time. Using an optimization method to minimize the difference between experimentally measured strain and simulated results, a good approximation of sensory particle properties can be determined and the strong sensory response of the transforming particle demonstrated. To illustrate an application of this method, a multi-scale finite element model of sensory particles embedded in the root rib of an aircraft wing is then considered. In particular, this unique model utilizes substructure modeling to maintain computational efficiency while relating globally applied loads to local structural response, allowing for the consideration of predicted particle response to crack propagation during wing loading. The effect of particle position relative to the crack tip on particle sensory response is assessed. Finally, this work demonstrates how sensory particles can be used to approximate the location of structural damage by interpolating a stress field based on the responses of multiple sensory particles in the vicinity of a propagating crack. [ABSTRACT FROM AUTHOR]

Shape memory alloy actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. Induction heating of shape memory alloy actuators, specifically tubes that twist about the longitudinal axis, has recently been studied experimentally and computationally using finite element analysis. Reduced-order models for the torsional behavior of shape memory alloy tubes and induction heating of general metallic tubes exist, and thus, it is possible for these thermal and mechanical models to be combined and numerically solved. This work develops and implements an engineering model for inductively heated shape memory alloy tubes based on the reduction of the governing partial differential equations in space and time to an ordinary differential equation in time. An example solution is compared to finite element analysis results and agrees well. Finally, the ordinary differential equation is linearized and solved analytically. The linearized model agrees well with the nonlinear ordinary differential equation and finite element model. [ABSTRACT FROM AUTHOR]

This paper discusses the fabrication, operation, and physical reconfiguration of a structurally embedded vascular antenna. The antenna is a thin-wire dipole that meanders with rotational symmetry according to a sinusoid with power-series growth. It is formed from two curvilinear vascular networks embedded into a structural composite panel and connected to a conductive vertical interconnect structure and SubMiniature Version A-connected parallel-strip transmission line for excitation and measurement. The pressure-driven flow of a liquid metal alloy within the vascular network enables the physical reconfiguration of the meandering dipole with the primary goal of dynamically tuning the matched impedance bandwidth of the fundamental dipole mode by symmetrically lengthening the conductive pathways forming the dipole. Details regarding the design, fabrication, simulation, and measurement of the meandering dipole antenna are provided along with a linearly expanding dipole for comparison. [ABSTRACT FROM PUBLISHER]

This work addresses the multi-fidelity analysis-driven design of a thermal transport system based on the flow of liquid metal through a structural laminate as induced by a solid-state magneto-hydro-dynamic (MHD) pump. A full three-dimensional model of the thermal transport system is both simplified to a reduced-order algebraic model, which correctly captures trends in the global system response, and alternatively implemented in an finite element framework, which captures essential global and local aspects of the system response not attainable via reduced-order modeling. The predictions of each model are validated against previously published experimental data. It is shown in detail for the first time in the context of MHD systems that a multi-fidelity approach to the multi-objective design optimization problem can leverage both the speed of the algebraic model and the accuracy of the finite element model, leading to effective predictions of optimal system designs in a reasonable amount of time. A relatively new algorithm for multi-objective and parameterized Pareto optimization is employed, and a clear path of continued development is identified. [ABSTRACT FROM AUTHOR]

This article describes the development and validation of a new thermomechanically coupled multi-layered shape memory alloy beam finite element. The finite element is formulated, assuming coupled equilibrium equations for the mechanical and thermal problems. The constitutive shape memory alloy model of Lagoudas and coworkers is implemented in the formulation. Multi-field kinematic hypotheses are proposed, combining a first-order shear displacement field with a sixth-order polynomial temperature field through the thickness of the beam, enabling adequate representation of the temperature and phase transformation profiles due to rapid thermal loading, uneven thermal loading, and boundary conditions and multi-layered configurations with variable thermal properties. The non-linear transient discretized equations of motion of the shape memory alloy beam are synthesized and solved using the Newton–Raphson method with an implicit time integration scheme. Numerical results illustrate the time response of uniform and bi-layered NiTi beams under various thermomechanical loads predicted by the developed finite element. Correlations of the beam element predictions with those of plane stress two-dimensional finite element shape memory alloy models demonstrate excellent agreement in the calculated displacement, temperature, and phase transformation fields. Additionally, the developed beam finite element yields computationally fast simulations providing an effective tool for the design and simulation of rod, beam, and strip shape memory alloy actuators and active structures. [ABSTRACT FROM AUTHOR]

The increasing number of applications incorporating shape-memory alloy (SMA) components motivates the development of three-dimensional constitutive models to enhance their analysis and design. These models only reach their full utility if they are then implemented into numerical (e.g. often finite-element-based) frameworks. The present article addresses a topic rarely considered in the myriad of SMA computational analysis works in the literature: the analysis of the time and accuracy of implementation options. In particular, this work proposes to compare the performance of the implicit and explicit integration methods for two common three-dimensional phenomenological constitutive models: (i) the model by Lagoudas et al.; and (ii) the model by Auricchio et al. available in all installations of Abaqus. In doing so, the present work develops and implements an explicit algorithm for the model by Lagoudas et al. for the first time. The investigated models are compared in a chosen benchmark boundary value problem analysis considering both thermally induced actuation and isothermal stress-induced transformation of an SMA beam. The performance of the methods in terms of analysis time and parallelization efficiency are also investigated. [ABSTRACT FROM AUTHOR]

Recent tendencies in architecture take a unique point of view, with aesthetically novel and unnatural sensibilities emerging from a close scrutiny and study of apparently natural systems. These tendencies are being driven by mathematical and computational abstractions that transform the way we understand the matterinformation relationship. This project was inspired by Op Art, a twentieth century art movement and style in which artists sought to create an impression of movement on an image surface by means of an optical illusion. Passive elements consisting of composite laminates were produced with the goal of creating lightweight, semi-rigid, and nearly transparent pieces. The incorporation of active materials comprised a unique aspect of this project: the investigation of surface movement through controlled and repeatable deformation of the composite structure using shape memory alloy (SMA) wiring technology. The integration of composite materials with SMA wiring and Arduino automation control resulted in an architectural wall that incorporated perceptual and actual motion. [ABSTRACT FROM AUTHOR]

Origami engineering, which is the practice of creating useful three-dimensional structures through folding and fold-like operations applied to initially two-dimensional entities, has the potential to impact several areas of design and manufacturing. In some instances, however, it may be impractical to apply external manipulations to produce the desired folds (e.g., as in remote applications such as space systems). In such cases, self-folding capabilities are valuable. A self-folding material or material system is one that can perform folding operations without manipulations from external forces. This work considers a concept for a self-folding material system. The system extends the ‘programmable matter’ concept and consists of an active, self-morphing sheet composed of two meshes of thermally actuated shape memory alloy (SMA) wire separated by a compliant passive layer. The geometric and power input parameters of the self-folding sheet are optimized to achieve the tightest local fold possible subject to stress and temperature constraints. The sheet folding performance considering folds at different angles relative to the orientation of the wire mesh is also analyzed. The optimization results show that a relatively low elastomer thickness is preferable to generate the tightest fold possible. The results also show that the self-folding sheet does not require large power inputs to achieve an optimal folding performance. It was shown that the self-folding sheet is capable of creating similar quality folds at different orientations. [ABSTRACT FROM AUTHOR]

This work presents the design and fabrication of two multi-element structurally embedded vascular antennas (SEVAs). These are achieved through advances in additively manufactured sacrificial materials and demonstrate the ability to embed vascular microchannels in both planar and complex-curved epoxy-filled quartz fiber structural composite panels. Frequency-reconfigurable antennas are formed by these structures through the pressure-driven transport of liquid metal through the embedded microchannels. The planar multi-layer topology examines the ability to fabricate two co-located radiating structures separated by a single ply of quartz fabric within the composite layup. The multi-element linear array topology composed of microchannels embedded on to a single-layer are used to demonstrate the ability to conformally-integrate these channels into a complex curved surface that mimics an array of antennas on the leading edge of an Unmanned Aerial Vehicle (UAV). A parallel-strip antipodal dipole feed structure provides excitation and serves as the interface for fluid displacement within the microchannels to facilitate reconfiguration. The nominal design of the SEVAs achieve over a decade of frequency reconfiguration with respect to the fundamental dipole mode of the antenna. Experimental and predicted results demonstrate the operation for canonical states of the antennas. Additional results for the array topology demonstrate beam steering and contiguous operation of interconnected elements in the multi-element structure. [ABSTRACT FROM AUTHOR]

Origami, the ancient art of paper folding, has inspired the design of engineering devices and structures for decades. The underlying principles of origami are very general, which has led to applications ranging from cardboard containers to deployable space structures. More recently, researchers have become interested in the use of active materials (i.e., those that convert various forms of energy into mechanical work) to effect the desired folding behavior. When used in a suitable geometry, active materials allow engineers to create self-folding structures. Such structures are capable of performing folding and/or unfolding operations without being kinematically manipulated by external forces or moments. This is advantageous for many applications including space systems, underwater robotics, small scale devices, and self-assembling systems. This article is a survey and analysis of prior work on active self-folding structures as well as methods and tools available for the design of folding structures in general and self-folding structures in particular. The goal is to provide researchers and practitioners with a systematic view of the state-of-the-art in this important and evolving area. Unifying structural principles for active self-folding structures are identified and used as a basis for a quantitative and qualitative comparison of numerous classes of active materials. Design considerations specific to folded structures are examined, including the issues of crease pattern identification and fold kinematics. Although few tools have been created with active materials in mind, many of them are useful in the overall design process for active self-folding structures. Finally, the article concludes with a discussion of open questions for the field of origami-inspired engineering. [ABSTRACT FROM AUTHOR]