Passive energy balancing design for a linear actuated morphing wingtip structure

A passive energy balancing concept for linear actuation is investigated in the current work by adopting a negative stiffness mechanism. The proposed negative stiffness mechanism uses a pre-tensioned spring to produce a passive torque and therefore to transfer the passive torque through a crankshaft for linear motion.The proposed passive energy balancing design is supposed to be applied in a morphing wingtip, of which the shape change comes from the elastic deformation of the morphing structure. A significant amount of linear actuation force can be required to deform the structure, and therefore it is important to reduce the required force and the consumed energy by adopting the passive energy balancing design.The kinematics of the negative stiffness mechanism is developed to satisfy the required linear motion and its geometry is then optimised to reduce the energy requirements. The performance of the optimised negative stiffness mechanism is evaluated through the net force and the total required energy, which shows the potential of the design in the morphing wingtip application

형상 기억 효과를 활용한 소프트 모핑 섬유 구동기

학위논문 (박사)-- 서울대학교 대학원 공과대학 기계항공공학부, 2017. 8. 안성훈.Soft morphing structures execute biologically inspired motions more effectively through flexible body mechanisms than conventional rigid-bodied structures. Their softness and compliance allow them to mimic muscle-like biological locomotion and possess many degrees of freedom, compared with rigid bodies. To demonstrate the morphing in various modes, including three-dimensional (3D) volumetric transformation, textile actuators are presented based on woven and knitted structures. First, a woven type smart soft composite (SSC) consisting of shape memory alloy (SMA) wires and a glass fiber-reinforced composite was introduced for generating a large deformation using the inherent properties of woven textiles. The embedded SMA wires were divided into independently controlled groups to create asymmetrical bending through unequal power input and/or current feed times. By controlling the power input, symmetric/asymmetric actuation modes were achieved. To determine the characteristics of the woven SSCs, different configurations of the composite were tested in terms of the diameters of the SMA wires, numbers of embedded SMA wires, and numbers of glass-fiber fabric lamina. The proposed woven type SSC was implemented as the trailing edge of a spoiler on a small (⅛)-scale car and as variable winglets of an unmanned aerial vehicle. To confirm their aerodynamic performance, wind tunnel experiments were conducted under various wind speeds, angles of attack, and actuation modes of the soft morphing wings. Second, to demonstrate the morphing in various modes, including 3D volumetric transformation, a smart morphing knit was developed that was made from a thermally responsive fiber, allowing the creation of 3D morphologies with no auxiliary materials or an elastomeric matrix. A knitting method was used in the manufacturing process of the smart textile structure, and four combinations of loop patterns (plan, garter, rib, and seed patterns) were used to explore a variety of morphing shapes. Open and closed geometries of 14 knitting structures were used to characterize their morphing behaviors. Using the knitting methods, morphing flowers (a lily-like, a daffodil-like, a gamopetalous, and a calla-like flower) were fabricated and their blooming motion was demonstrated by controlling the current to actuate the petals selectively.Chapter 1. Introduction 1 1.1. Actuators for morphing systems 1 1.2. Soft morphing actuators 3 1.3. Textile platform-based actuators 5 1.4. Textile manufacturing technologies 7 1.5. Goals of this research 8 Chapter 2. Woven type smart soft composite actuators 10 2.1. Design 10 2.2. Materials and fabrication 12 2.2.1. Active component 12 2.2.2. Fabrication 14 2.3. Beam-type soft actuators 17 2.3.1. Deformation behavior 17 2.3.2. Blocking force 25 2.3.3. Mechanical properties and analysis 27 2.4. Shell-type soft actuator 34 2.4.1. Concept and design 34 2.4.2. Theoretical analysis 36 2.4.3. Actuation evaluation 41 Chapter 3. Applications of woven actuators 48 3.1. Rear-spoiler for ground vehicles 48 3.1.1. Introduction 48 3.1.2. Design and actuation behaviors 52 3.1.3. Modeling 56 3.1.4. Wind tunnel testing with soft morphing spoiler 62 3.1.5. Small-scale vehicle with soft morphing spoiler 76 3.1.6. Conclusions 85 3.2. Morphing winglets for unmanned aerial vehicles (UAV) 88 3.2.1. Introduction 88 3.2.2. Concept of soft morphing winglet 91 3.2.3. Materials and fabrication 94 3.2.4. Design and evaluation 95 3.2.5. UAV with soft morphing winglets 99 3.2.6. Conclusions 105 Chapter 4. Smart morphing knit 108 4.1. Introduction 108 4.2. Design 110 4.3. Materials and methods 111 4.4. Modeling of a unit loop 113 4.5. Performance evaluation 117 4.5.1. Modes of actuation 117 4.5.2. Actuating force 124 4.5.3. Long-term actuation 129 Chapter 5. Applications of knit actuators 131 5.1. Blooming knit flowers 131 5.2. Wearable applications 134 Chapter 6. Conclusions 142 Bibliography 143 국문초록 151Docto

Stability and morphing characteristics of bistable composite laminates

The focus of the current research is to investigate the potential of using bistable unsymmetric cross-ply laminated composites as a means for achieving structures with morphed characteristics. To this end, an investigation of the design space for laminated composites exhibiting bistable behavior is undertaken and the key parameters controlling their behavior are identified. For this purpose a nonlinear Finite Element methodology using ABAQUS code is developed to predict both the cured shapes and the stability characteristics of unsymmetric cross-ply laminates. In addition, an experimental program is developed to validate the analytically predicted results through comparison with test data. A new method is proposed for attaching piezoelectric actuators to a bistable panel in order to preserve its favorable stability characteristics as well as optimizing the actuators performance. The developed nonlinear FE methodology is extended to predict the actuation requirements of bistable panels. Actuator requirements, predicted using the nonlinear FE analysis, are found to be in agreement with the test results. The current research also explores the potential for implementing bistable panels for Uninhabited Aerial Vehicle (UAV) wing configuration. To this end, a set of bistable panels is manufactured by combining symmetric and unsymmetric balanced and unbalanced stacking sequence and their stability characteristics are predicted. A preliminary analysis of the aerodynamic characteristics of the manufactured panels is carried out and the aerodynamic benefits of manufactured bistable panel are noted.Ph.D.Committee Chair: Erian Armanios; Committee Member: D. Stefan Dancila; Committee Member: Juan R. Cruz; Committee Member: Massimo Ruzzene; Committee Member: Rami Haj-Al

A review of modelling and analysis of morphing wings

Morphing wings have a large potential to improve the overall aircraft performances, in a way like natural flyers do. By adapting or optimising dynamically the shape to various flight conditions, there are yet many unexplored opportunities beyond current proof-of-concept demonstrations. This review discusses the most prominent examples of morphing concepts with applications to two and three-dimensional wing models. Methods and tools commonly deployed for the design and analysis of these concepts are discussed, ranging from structural to aerodynamic analyses, and from control to optimisation aspects. Throughout the review process, it became apparent that the adoption of morphing concepts for routine use on aerial vehicles is still scarce, and some reasons holding back their integration for industrial use are given. Finally, promising concepts for future use are identified

Continuous Open Access Special Issue "Aircraft Design": Number 2/2020

Following the successful initial Special Issue on “Aircraft Design (SI-1/2017)”, this is already the second SI “Aircraft Design (SI-2/2020)”. Activities in the past showed that aircraft design may be a field too small to justify its own (subscription-based) journal. A continuous open access special issue may fill the gap. As such, the Special Issue “Aircraft Design” can be a home for all those working in the field who regret the absence of an aircraft design journal. SI-2/2020 contains seven papers; an Editorial: 1.) "Publishing in 'Aircraft Design' with a Continuous Open Access Special Issue" and six Original Research Articles about 2.) Amphibious Aircraft Developments, 3.) Design Space Exploration of Jet Engine Components, 4.) Study of Subsonic Wing Flutter, 5.) Design Optimization of a Blended Wing Body Aircraft, 6.) Discrete Mobile Control Surfaces, 7.) Electro-Impulse De-Icing Systems

Design and Optimisation of Morphing Aircraft

Morphing has the potential to improve the aircraft performance by adaptively changing the shape during different flight conditions. The capabilities of changing shape and carrying aerodynamic loads simultaneously make the design of the morphing structure challenging. The weight increase of morphing aircraft should also be considered, which requires system level analysis and evaluation, and the optimisation of the morphing structure. The thesis focuses on morphing wingtip devices, which are small in size but have a significant influence on the aerodynamic performance. A compliant structure based on unsymmetrical stiffness is proposed. The compliant structure has unsymmetrical stiffness allocation, which will have differential axial deflections when it is actuated. The differential deflections lead to a rotation of the compliant structure. A simplified model of the compliant structure is built, and analytical expressions are derived, which highlight the effects of the total stiffness and the stiffness asymmetry. A case study also represents the system level influence of retrofitting a morphing winglet to a baseline wing. Corrugated panels are applied to provide the stiffness asymmetry. An equivalent model is built to predict the deformation of the corrugated panels. A coupling between the vertical deflection and the axial load is found, which will affect the deflections of the compliant structure significantly. An equivalent beam is used to represent the corrugated panel. The equivalent model is verified by detailed finite element models and experiments. The optimisation of the compliant structure is performed. The actuation force is the objective, while the aerodynamic force and the shape change are included in the optimisation. The influence of the different aerodynamic forces and target shape changes are investigated, which shows the compromise made by the optimised variables to satisfy the constraint and reduce the actuation force. The compliant structures in the earlier case study are optimised, which shows a significant performance increase at the system level. A demonstration model of the morphing winglet is designed, manufactured and tested. To fit within the thickness of the airfoil, a sequence of optimisations is performed to find the suitable geometry variables. An extreme stiffness asymmetry is required to reduce the actuation force, which validates the proposed morphing structure concept. Static tests and wind tunnel tests are performed to validate the model. Finally, the contributions of the research are summarised, together with some future work on different aspects

Design of a composite morphing wing

Morphing aircraft components can increase the possibility of optimising the performance of an aircraft at various flight conditions. A morphing aircraft wing can change the wing shape to modify the lift and drag distribution on the wing surface, allowing the lift-to-drag ratio to be tailored to the desired performance. A camber morphing and a trailing edge morphing wing changes the aerodynamic lift by altering the camber and by deflecting the wing trailing edge, potentially reducing the aerodynamic drag by eliminating the gaps; which exist between the main wing and the control surfaces of a conventional wing. Among the technology used to achieve camber morphing and trailing edge morphing, were mechanical and smart actuations, such as piezoelectrics and shape memory alloys (SMAs). Compliant structures, cellular structures, shape memory polymers, and multi-stable structures were exploited to improve the flexibility of the aerofoil sections or wings. SMA wires were one of the smart actuators which had been extensively utilised to morph various aerofoils/wings, mainly due to the high actuation force and compatibility, which reduce the volume and weight of the actuators and the complexity of moving mechanical components. In this research, a user defined material model (UMAT) was developed within the explicit LS-DYNA FE code, for NiTi shape memory alloy (SMA) wires, and used for actuation of the composite morphing wing. The Tanaka SMA constitutive model was implemented in MATLAB and FORTRAN codes for the SMA-actuation of various structures. The UMAT was used to simulate actuations of various complex morphing structures, including several aluminium and composite aerofoils with corrugated sections, and a pre-curved corrugated plate. Actuations of the two aluminium aerofoils, with corrugated sections in the lower surface and the middle cantilever section, by a 0.5mm-diameter SMA wire with a maximum recoverable strain or a pre-strain of 1.6%, resulted in trailing edge (TE) deflections of 7.8 mm and 65.9 mm, respectively. Actuation of the carbon fibre (CF) composite aerofoil, with the corrugated section as a middle cantilever section, and with 8 layers of CF in ±45° directions, produced a TE deflection of 52.0 mm. To demonstrate the SMA-actuated morphing concept, a composite 3D-printing technology was explored to manufacture a carbon fibre (CF) composite structure, consisted of a flat vertical front plate, a corrugated section, and a rear trailing edge (TE) section. Due to the nature of 3D-printing, two layers of CF were 3D-printed along the circumference of the corrugation and the TE section, and the minimum thickness of the structure was 3 mm. Experimentally, actuation of the CF composite corrugated structure by a NiTi SMA wire with a diameter of 0.2 mm and a pre-strain of 4.77%, and with a diameter of 0.5 mm and a pre-strain of 1.68%, aligned in the chordwise direction, resulted in 1.1 mm and 6.0 mm TE deflections, respectively. Cyclic tests (10 and 30 cycles) of the actuation of the CF composite corrugated structure showed the TE deflection converged after few cycles. A 1.25m-span composite morphing wing was finally designed and manufactured, consisted of a CF composite D-nose spar which resisted the main aerodynamic loading, and rear sections which were made of rigid and flexible foams. CF composite spar flanges, spar web, front and rear ribs, were 3D-printed, and were assembled with a CF composite skin which was autoclave-manufactured, to form the CF composite D-nose spar. Sections of rigid and flexible foams were CNC-machined and were attached to the front CF composite D-nose spar, 3D-printed long rear ribs, trailing edge sections and the morphed corrugated structure, to form a complete composite morphing wing.Open Acces

A cooling system for s.m.a. (shape memory alloy)based on the use of peltier cells

The aim of this thesis has been the study and the implementation of an innovative cooling system for S.M.A. (Shape Memory Alloy) material by using a Peltier cell. This system has demonstrated a consistent cooling time reduction during the application and so that the solution adopted has confirmed that it can be used for a better operability of the S.M.A. material during the cooling phase. After an accurate selection of possible cooling system to be adopted on these materials the better choice in terms of efficiency and energy consumption reduction has converged on Peltier cell design development. In this context for our research three investigation have been conducted. The first one has concerned an analytic investigation in order to understand the phenomenology and the terms involved during the heat exchange. After this study a numerical investigation through a Finite Element approach by commercial software has been carried out. Also an experimental investigation has been conducted, at the CIRA Smart Structure Laboratory, in order to verify the results obtained by the numerical prediction. The set-up with the Peltier cell used as heater and cooler of the S.M.A. has confirmed the soundness of the solution adopted. Finally, a correlation between numerical and experimental results have been presented demonstrating the validity of the obtained results through the developed investigations. This system, composed of Peltier cell has confirmed also an energy consumption reduction because the cell has been used for heating and cooling phase without additional system as resistive system (Joule effect). This project shall be also industrial involvement in a new cost cut down point of vie

Thermally induced multi-stable composites for morphing aircraft applications

This research focuses on the realisation of 'shape-adaptable' systems through unsymmetrical laminates.The residual stress field which is built-into this type of laminates, is used to obtain panels with two or more equilibrium states. Such systems provide a possible solution for the realisation of morphing structures because they allow to simultaneously fulfil the contradictory requirements of flexibility and stiffness.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Optimal design of morphing structures

Morphing structures change their geometric configuration to achieve a wide range of performance goals. For morphing aircraft these include alleviating drag, or altering aerofoil lift. The design of structures capable of realising these goals is a highly multidisciplinary problem. Optimally morphing a compliant structure involves finding the distribution of actuation which best achieves a desired configuration change. In this work, the location and magnitude of discrete actuators are optimised, to minimise both aerodynamic and geometric objective functions. A range of optimisation methods, including differential and stochastic techniques, has been implemented to search optimally the large, nonlinear, and often discontinuous design spaces associated with such problems. The optimal design of morphing systems is investigated through consideration of a morphing shock control bump and an adaptive leading edge. CFD is implemented to evaluate the aerodynamic performance of optimiser-controlled morphing structures. A bespoke grid-generation algorithm is developed, capable of producing a mesh for all possible geometries, with low levels of cell skewness and orthogonality at the fluid-structure boundaries. Structural compliance – a prerequisite for morphing – allows significant displacement of the structure to occur, but simultaneously enables the possibility of detrimental aeroelastic effects. Static aeroelasticity is catered for, at significant computational expense, via coupling of the structural and aerodynamic models within individual optimisation function evaluations. Morphing geometry is investigated to reduce computational design requirements, and provide an objective starting point for an aeroelastic optimisation. The requirements of morphing between aerodynamic shapes are evaluated using geometry-based objective functions. Displacements and curvatures are compared between an optimiser-controlled structure and the target morph, and the differences minimised to effect the required shape change. In addition to enabling optimal problem definition, these geometric objective functions allow conclusions on the feasibility of a morph to be drawn a priori