Search

This paper introduces the design process of a multi-functional skin structure for thermal energy transport and load bearing using topology optimization. A single cell with periodic boundary condition in the in-plane direction is used as a design space so that the final single cell design can be repeated to construct a continuous sheet of material. The new engineered skin is developed using two materials to meet two required functionalities of a Sensorcraft wing skin; one is to maximize the conductivity of the skin in out-of-plane direction in order to dissipate internal heat into the air (sink) so that the thermoelectric (TE) device can be operated at an optimum condition. The other is to maximize the in-plane stiffness to provide the load bearing capability of the skin to an external load such as torsion. A multi-functional optimization scheme using a linear combination of two objective functions with weights is used to find the optimal layout of those two materials. The Optimality Criteria (OC) method is utilized as an optimizer. A sample problem is solved to demonstrate the design process. A specimen was manufactured and tested to verify the synthesis results.

The addition of energy harvesting is investigated to determine the benefits of its integration into a small unmanned air vehicle (UAV). Specifically, solar and piezoelectric energy harvesting techniques were selected and their basic functions analyzed. The initial investigation involved using a fundamental law of thermodynamics, entropy generation, to analyze the small UAV with and without energy harvesting. A notional mission was developed for the comparison that involved the aircraft performing a reconnaissance mission. The analysis showed that the UAV with energy harvesting generated less entropy. However, the UAV without energy harvesting outperformed the other UAV in total flight time at the target. The analysis further looked at future energy harvesting technologies and their effect on the energy harvesting UAV to conduct the mission. The results of the mission using the advanced solar technology showed that the effectiveness of the energy harvesting vehicle would increase. Designs for integrating energy harvesting into the small UAV system were also developed and tests were conducted to show how the energy harvesting designs would perform. It was demonstrated that the addition of the solar and piezoelectric devices would supply usable power for charging batteries and sensors and that it would be advantageous to implement them into a small UAV.

The broadly defined mission of the Biomedical Informatics Research Network (BIRN, www.nbirn.net) is to better understand the causes human disease and the specific ways in which animal models inform that understanding. To construct the community-wide infrastructure for gathering, organizing and managing this knowledge, BIRN is developing a federated architecture for linking multiple databases across sites contributing data and knowledge. Navigating across these distributed data sources requires a shared semantic scheme and supporting software framework to actively link the disparate repositories. At the core of this knowledge organization is BIRNLex, a formally-represented ontology facilitating data exchange. Source curators enable database interoperability by mapping their schema and data to BIRNLex semantic classes thereby providing a means to cast BIRNLex-based queries against specific data sources in the federation. We will illustrate use of the source registration, term mapping, and query tools.

This investigation introduces a novel optimization approach for conceptual design of a distributed actuation system that is capable of achieving radical structural shape changes, specifically applicable to morphing air vehicles. The topology and dimensional design process is implemented in two-stages: The actuation system layout is first determined through a multi-disciplinary topology optimization process and, then, the thickness or crosssectional area of each existent member is optimized under aerodynamics pressure and actuation loads. The previous investigation by the authors demonstrated the potential capabilities of a topology optimization methodology for determination of distributed actuation systems for a morphing wing structure without dimensional considerations. The primary objective of the present investigation, therefore, is to introduce the new methodology and processes to address the sizing issues. The investigation includes the formulation of appropriate optimization problems, solution sequence, and development of effective modeling concepts. Sample problems are solved to demonstrate the potential capabilities of the presented methodology.

In this paper, the optimal distribution of actuators throughout an in-plane flexible morphing wing structure was investigated. The drive to minimize structural weight causes a wing to be more flexible, and the locations and orientations of the actuators become more critical as the structure becomes more flexible. The optimal location and orientation varied depending on the loading conditions and initial configuration of the wing. The optimization problem was stated such to minimize weight, while maximizing the geometric advantage (GA) and efficiency of the system. The optimization problem constraints were member stresses, and the force transferred to the actuators was not to be greater than the force the actuator is able to produce. Each unit cell was comprised of four linkages pinned together, and possibly an actuator. The flexible skin was modeled as a non-linear elastic spring stretched between two apposing vertices. Initially, a purely rigid system was studied for both the single-cell and three-cell systems. Next, the flexible cases for the single-cell and three-cell models were examined. Experiments were designed for the single-cell and three-cell models using both the NASTRAN optimization toolbox and MATLAB. The three-cell experiment was designed using aeroelastic scaling techniques. Results for the single-cell and three-cell analyses will be compared to experimental data for validation.

*† ‡ This paper describes the development of engineered composite skins for morphing aircraft applications. Some of these applications suggest that materials with low in-plane stiffness and relatively high out-of-plane stiffness may be required. To this end, a two-step topology optimization process has been developed in order to design skins to meet these requirements. The first step in the process is to determine bulk material properties for the skin and the layout of attachments between the skin and underlying substructure. This results in a distribution of bulk properties across the skin. The second step utilizes these property values as objectives in a multi-phase material optimization in order to determine the composition and layout of a set of macroscopic multi-phase material unit cells.

This paper describes the development of a simulation tool to study the time domain, in-flight behavior of aircraft morphing mechanisms. Limitations of existing tools are discussed leading to requirements for the new capability. The framework of the tool is discussed as well as the component analyses including control systems, aerodynamics, modal structural representations, and multibody kinematics. The basic capability of the tool is demonstrated through example simulations of a folding morphing wing.

This paper describes the development of a tool for simulating the flight of a morphing aircraft during the morphing process. Also discussed are current-generation tools for modeling vehicle flight and illustrations of how these tools are as yet too immature for modeling of the flight of an aircraft during morphing of the wings. A framework is developed for modeling vehicle flight that incorporates vehicle morphing. The procedures outlined in the paper are sufficiently general to accommodate aircraft utilizing changes in sweep, span, or area. The current state of the art and the planned developments are illustrated through their application to the flight of a folding-wing vehicle.

Demonstrated in this research is the aeroelastic simulation of a folding wing unmanned combat aerial vehicle through integration of finite element modeling, aerodynamic loading, and continuous-time multibody simulation. Flexible vehicle structural elements are modeled and assembled using traditional finite element methods, with component mode synthesis applied to obtain a defined subset of the full-order system modes. Investigations of time histories recorded for changing flight conditions and morphing states are presented for simulated wind tunnel test runs. Results of simulated wind tunnel test runs clearly indicate the ability of the integrated simulation approach to characterize the aeroelastic behavior of a folding wing aircraft throughout the structural morphing process. The results of free-flight maneuvering simulations reveal the significance of wing fold angle on structural load paths and wing fold hinge moments undergoing out-of-plane wing morphing. The success of this study demonstrates the validity of this innovative modeling and simulation approach in the design and analysis of morphing vehicles

In this paper, the optimal location of a distributed network of actuators within a scissor wing mechanism is investigated. The analysis begins by developing a mechanical understanding of a single cell representation of the mechanism. This cell contains four linkages connected by pin joints, a single actuator, two springs to represent the bidirectional behavior of a flexible skin, and an external load. Equilibrium equations are developed using static analysis and the principle of virtual work equations. An objective function is developed to maximize the efficiency of the unit cell model. It is defined as useful work over input work. There are two constraints imposed on this problem. The first is placed on force transferred from the external source to the actuator. It should be less than the blocked actuator force. The other is to require the ratio of output displacement over input displacement, i.e., geometrical advantage (GA), of the cell to be larger than a prescribed value. Sequential quadratic programming is used to solve the optimization problem. This process suggests a systematic approach to identify an optimum location of an actuator and to avoid the selection of location by trial and error. Preliminary results show that optimum locations of an actuator can be selected out of feasible regions according to the requirements of the problem such as a higher GA, a higher efficiency, or a smaller transferred force from external force. Results include analysis of single and multiple cell wing structures and some experimental comparisons.

In this paper, the topology optimization methodology for the synthesis of distributed actuation system with specific applications to the morphing air vehicle is discussed. The main emphasis is placed on the topology optimization problem formulations and the development of computational modeling concepts. For demonstration purposes, the inplane morphing wing model is presented. The analysis model is developed to meet several important criteria: It must allow large rigid-body displacements, as well as variation in planform area, with minimum strain on structural members while retaining acceptable numerical stability for finite element analysis. Preliminary work has indicated that addressed modeling concept meets the criteria and may be suitable for the purpose. Topology optimization is performed on the ground structure based on this modeling concept with design variables that control the system configuration. In other words, states of each element in the model are design variables and they are to be determined through optimization process. In effect, the optimization process assigns morphing members as 'soft' elements, non-morphing load-bearing members as 'stiff' elements, and non-existent members as 'voids.' In addition, the optimization process determines the location and relative force intensities of distributed actuators, which is represented computationally as equal and opposite nodal forces with soft axial stiffness. Several different optimization problem formulations are investigated to understand their potential benefits in solution quality, as well as meaningfulness of formulation itself. Sample in-plane morphing problems are solved to demonstrate the potential capability of the methodology introduced in this paper.

The Entropy Generation Minimization (EGM) approach is applied to the design of a new integrated radar aircraft skin, which both meets requisite aircraft structural needs and provides a pathway for the waste heat from structurally integrated power devices. Thermoelectric (TE) devices, sandwiched between a heterogeneous skin layer and the radar devices for the purpose of harvesting waste heat rejected to the ambient, are considered in the analysis. A heterogeneous skin layer is designed using the EGM approach, which is then applied to the overall mission of the aircraft to determine the optimal skin thickness and volume fractions of the matrix and inclusions in the composite skin.Copyright © 2006 by ASME

This paper provides a description of research seeking to experimentally verify the effectiveness of a thermal switch used in series with TE devices for waste heat recovery for constant and variable source heat input, and for variable source thermal capacitance (mass). Using an experimental set-up comprised serially of a fixed heat source, a variable thermal resistance air gap serving as a thermal switch, a thermoelectric device and a heat sink mounted on a translation stage, the time-averaged power output to power input ratios improved up to 15% and 30% respectively for constant and variable heat input in certain design space conditions. The experimental results, as supported by model predictions, suggest that the thermal capacitance of the heat source must be greater than the thermal capacitance of the TE device in order for thermal switching to improve the time-averaged power output to power input ratios of waste heat recovery systems.Copyright © 2006 by ASME

In this work, a design optimization procedure is developed to maximize the energy efficiency of a scissor mechanism for the NextGen's Batwing application. The unit cells are modeled using a finite element approach. The model considers elastic skin, modeled as linear springs, as well as actuator and aerodynamic loads. A nonlinear large displacement analysis is conducted, and the position of the actuator is optimized using Matlab's gradient based optimization algorithm FMINCON. This optimization procedure is used to investigate the effect of different constraints and load cases. The model is expanded to include multiple unit cells and actuators. A two stage optimization process using a Genetic Algorithm and traditional gradient based optimization (FMINCON) is also developed. The two stage optimization is used to optimize actuator position and placement for different constraints and load cases. Results show that placement and position optimization produce small gains in maximizing energy efficiency; morphing using a soft isotropic skin is more efficient than stiff isotropic and anisotropic skin. In addition, the GA did not use the all of the available actuators to maximize energy efficiency.

This investigation addresses basic characterization of a shape memory polymer (SMP) as a suitable structural material for morphing aircraft applications. Tests were performed for monotonic loading in high shear at constant temperature, well below, or just above the glass transition temperature. The SMP properties were time-and temperature-dependent. Recovery by the SMP to its original shape needed to be unfettered. Based on the testing SMPs appear to be an attractive and promising component in the solution for a skin material of a morphing aircraft. Their multiple state abilities allow them to easily change shape and, once cooled, resist large loads.

A synthesis technique using a topology optimization scheme for an adaptive wing structure and mechanism design will be described. This enables the design of energy efficient adaptive structures with controllable deformation characteristics. This is accomplished by using a multi-objective function that minimizes strain energy and maximizes mutual potential energy to design the structure and mechanism simultaneously. To enable simultaneous design for structure and mechanism, the reference structure is composed of three layers; a membrane layer for skin, a frame element layer for structure, and truss element layer for an efficient mechanism. The attachment points between mechanism and structure are also identified with linear springs that are located between mechanism and structure layers. We focus on a simultaneous design of a wing structure and mechanism for large shape change applications. The geometrically large deformation analysis scheme is also added to the synthesis to capture nonlinear effects in design and it will be compared with linear synthesis results.Copyright © 2005 by ASME

In this investigation the hybrid cellular automaton (HCA) method for structural synthesis is extended to facilitate simultaneous topology and shape optimization. The HCA methodology has been developed for application to continuum structures. The development of this methodology has been inspired by the biological process of bone remodeling. In bone remodeling, only those elements located on the surface of the mineralized structure can be modified. In the HCA methodology implemented in this research only surface elements are allowed to change density during the structural synthesis process. The HCA method combines local design rules based on the cellular automaton paradigm and finite element analysis. Closed-loop control is used to modify the mass distribution on the internal and external surfaces of the design domain to find an optimum structure. The local control maintains a balance between mass and rigidity. The new methodology effectively combines elements of topology optimization and shape optimization into a single tool. Three classes of test problems are used to illustrate the method’s efficacy.

The Morphing Aircraft Structures (MAS) program has grown substantially in technology and has received more attention in recent years. One main initiative of this project is to develop aerial vehicles that are capable of radical shape change. Such shape changes should enable the vehicle to efficiently perform single missions that normally would require two or more different aircraft. Many design optimization issues arise for such systems. Morphing aircraft have multiple configurations which create multiobjective and possibly multilevel optimization problems. The problems are multiobjective because of the performance trade-offs occurring between each morphed state. In many morphing concepts one configuration must be defined in order to design a second state; this produces a multilevel design problem. The complexity of the simulation model and the nested formulation of the multilevel design problem results in a very computationally intensive optimization problem. This paper includes a discussion of solution strategies for these multiobjective, multilevel morphing aircraft design problems. Two design tools are explored to combat the described issues of the optimization problem: conversion to a single-level design problem and the use of variable fidelity optimization. A study is performed comparing the results obtained from the optimization processes of both a multi-level design problem and its corresponding single level problem. Finally a variable fidelity optimization framework is discussed and applied to design a morphing concept; the two fidelity models include a high fidelity computational fluid dynamics simulation and a low fidelity panel method.

This research is investigating the use of wide span, smoothly varying control surfaces placed on the leading and trailing edges of a wing to control cruise and maneuver performance of a representative combat unmanned vehicle. The purpose of the research is to understand the desired mechanical characteristics as well as the optimum deflection distribution in the spanwise and chordwise directions. In particular we are looking for the shapes of the control surfaces such that roll, pitch, and yaw control are performance requirements are met while the necessary input energy (actuator) is minimized during maneuvering phase of a mission. We are also looking at using the same set of control surfaces to minimize the induced drag during the cruise, loiter and dash portions of the flight profile. Several objective functions where investigated to gain insight into minimizing the actuator requirements. The optimization schemes satisfied equilibrium conditions. Results indicate and that the deflection distribution of the control surfaces is strongly dependent on the selected objective function, and that the desired shapes of the surfaces range from a linear variation to a parabolic distribution. Nomenclature b Span (ft) c Chord (ft) S Wing area (ft 2 ) α L C Lift coefficient due to angle of attack p L C Roll moment coefficient due to roll rate

This paper represents a "work-in-progress" status report on shape determination and sensing methods for deforming structures utilizing embedded sensors. This work is part of a larger effort in morphing aircraft structures at the Air Force Research Laboratory. The two critical issues involved in the present work are the determination of the number and placement of embedded sensors, and algorithms for transforming the sensor data into displacements to define the shape of the structure. These issues are addressed in the context of a laboratory experiment, which demonstrate many of the challenges inherent in the problem.

This paper describes the synthesis of a twodimensional airfoil with a chordwise variable geometry trailing edge control surface. Sequential unconstrained minimization techniques are applied to the control surface camberline representation to determine the optimal deflected shape. In addition to a continuous fourth order equation, a series of segments are used to describe the change in camber of the control surface, and viability of the two models is considered. Design variables consist of parameters which change the camberline including the control surface “hinge” location. The typical aeroelastic airfoil section is modelled with vertical and torsional springs to account for the flexibility of the system. Thin airfoil theory is used to model the pressure differential along the complete airfoil section, and determine aeroelastic performance parameters. The lift, moment imparted by the aerodynamic pressures on the control surface about its effective “hinge” point, and the energy necessary for the variable geometry control surface to overcome the aerodynamic forces as it changes positions are utilized as behavior functions. These behavior functions can be used in combination to provide objectives and constraints to the design process. Preand post-roll reversal cases are studied. 1 American Institute of Aero *Member AIAA †Associate Fellow AIAA ‡Professor, Fellow AIAA s declared a work of the U.S. Government and is not subject to copyright prote Nomenclature = , where is an integer = , where is an integer Aerodynamic Parameters = Density of Air = Freestream Velocity of Air = Dynamic Pressure = Initial Angle of Attack (AoA) = Change in AoA due to flexibility = Pressure Differential = Lift of Airfoil = Change in Energy at TECS = Aerodynamic Moment about Shear Center = “Hinge” Moment at Location = Lift Coefficient of 2-D Section = Slope of the Coefficient of Lift w.r.t. AoA = Moment Coefficient about Shear Center = Pressure Coefficient Differential

This study investigates the effect of store parameters variation on store-induced flutter and limit-cycle oscillation phenomena of an aircraft wing in the transonic regime. The primary store parameters are its mass and the chord wise location of its center of gravity. The effect of including store aerodynamics on the wing/tip store configuration is also investigated. These studies are being conducted to understand the behavior of store-induced flutter and limit-cycle oscillation in the nonlinear region so as to limit the number of flutter flight tests to a few critical ones and enable in future store certification efforts. The tip store center of gravity (c.g.) has been varied and positioned at three different locations: 32.5%, 40%, and 50%, with respect to aerodynamic tip chord. Automated Structural Optimization System and Computational Aeroelasticity Program - Transonic Small Disturbance (CAP-TSD) have been used in the linear and nonlinear region to perform this research. Studies show that flutter speed increases as the store c.g. was moved forward towards the leading edge. This gives an indication that store c.g. must be placed as far forward as possible with respect to the elastic axis to delay the occurrence of flutter, while satisfying other design constraints. It was observed that the increase in tip store mass significantly reduced the flight operating speed range of the aircraft. The effect of inclusion of store aerodynamics for different wing/store configurations was found to be insignificant compared to their corresponding mass-only models in the transonic regime. LCO onset speed was found to be sensitive to store mass and varied significantly for different store mass configurations.

This paper describes the development of a design model for the study of a two-dimensional airfoil with a chordwise variable geometry trailing edge control surface. A fourth order equation is used to describe the change in camber of the control surface allowing for discontinuity in the slope but not displacement at the control surface “hinge”. The equation coefficients and the control surface “hinge” location represent the design variables. The typical aeroelastic airfoil section is modelled with vertical and torsional springs to account for the flexibility of the system. Thin airfoil theory is used to model the pressure differential along the complete airfoil section. Relations for the aerodynamic lift and moment about the shear center are established so that the aeroelastic equilibrium equations can be solved. A relationship for the moment imparted by the aerodynamic pressures on the control surface about its effective “hinge” point is determined. Further, a relationship describing the energy necessary for the variable geometry control surface to overcome the aerodynamic forces as it changes position is established. These represent the behavior functions of the model, and thus can be considered as objectives and constraints in the design process. Studies are conducted to establish trends of behavior to aid in future synthesis. Nomenclature

Northrop Grumman Corporation built and twice tested a 30 percent scale wind tunnel model of a proposed uninhabited combat air vehicle under the DARPA/AFRL Smart Materials and Structures Development - Smart Wing Phase 2 program to demonstrate the applicability of smart control surfaces on advanced aircraft configurations. The model constructed was a full span, sting mounted model with smart leading and trailing edge control surfaces on the right wing and conventional, hinged trailing edge control surfaces on the left wing. Among the performance benefits that were quantified were increased pitching moment, increased rolling moment and improved pressure distribution of the smart wing over the conventional wing. This paper present an overview of the result from the wind tunnel test performed at NASA Langley Research Center's Transonic Dynamic Tunnel in March 2000 and May 2001. Successful results included: (1) improved aileron effectiveness at high dynamic pressures, (2) demonstrated improvements in lateral and longitudinal effectiveness with smooth contoured smart trailing edge over conventional hinged control surfaces, (3) chordwise and spanwise shape control of the smart trailing edge control surface, and (4) smart trailing edge control surface deflection rates over 80 deg/sec.

Morphing as an independent variable is addressed. Potential missions to demonstrate the value of morphing are presented and discussed. The effects of morphing on vehicle kinematics is demonstrated for takeoff, landing, and turn rate. At the system level, the effects of variable lift-to-drag ratio and specific fuel consumption on vehicle weight are examined for cruising flight. An example mission is presented to demonstrate how morphing can be implemented in constraint and sizing analyses, which are at the core of the aircraft conceptual design process. A comparison of morphing and non-morphing aircraft weights is made. It is demonstrated in some cases morphing adds weight due to requiring a structure to complete two missions. The requirement for new structural concepts is briefly discussed.

The recently completed DARPA/AFRL/NASA Smart Wing program, performed by Northrop Grumman Corporation (NGC), addressed the development and demonstration of smart materials based concepts to improve the aerodynamic and aeroelastic performance of military aircraft. This paper presents a final overview of the, program. The program was divided into two phases. Under Phase 1 (Jan 95 to Feb 99), the NGC-led team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. An important limitation of the Phase 1 effort, the low bandwidth achievable in shape memory alloy (SMA) based actuation, was addressed in Phase 2 (Jan 97 to Nov 01). Under Phase 2, a 30 percent scale full span wind tunnel model of an NGC uninhabited combat air vehicle (UCAV) design was developed. For the Phase 2 first wind tunnel test, completed in March 00, SMA-based leading and trailing edge control surfaces were incorporated on one wing of the model with conventional trailing edge control surfaces actuated using electric motors on the other. This test provided baseline steady-state data at Mach numbers ranging from 0.3 to 0.8. The second test, performed in May 01, demonstrated a structurally compliant trailing edge control surface actuated using piezo-electric motors. Spanwise and chordwise shape control was demonstrated for the trailing edge control surface at deflection rates of up to 80 deg/sec. Performance improvements in terms of increased rolling and pitching moments and lower control surface deflections were quantified.

A wind tunnel demonstration was conducted on a scale model of an unmanned combat air vehicle (UCAV). The model was configured with traditional hinged control surfaces and control surfaces manufactured with embedded shape memory alloys. Control surfaces constructed with SMA wires enable a smooth and continuous deformation in both the spanwise and cordwise directions. This continuous shape results in some unique aerodynamic effects. Additionally, the stiffness distribution of the model was selected to understand the aeroelastic behavior of a wing designed with these control surfaces. The wind tunnel experiments showed that the aerodynamic performance of a wing constructed with these control surfaces is significantly improved. However, care must be taken when aeroelastic effects are considered since the wing will show a more rapid reduction in the roll moment due to increased moment arm about the elastic axis. It is shown, experimentally, that this adverse effect is easily counteracted using leading edge control surfaces.

The DARPA/AFRL/NASA Smart Wing program, conducted by a team led by Northrop Grumman Corporation (NGC) under the DARPA Smart Materials and Structures initiative, addresses the development of smart technologies and demonstration of relevant concepts to improve the aerodynamic performance of military aircraft. This paper presents an overview of the smart wing program. The program is divided into two phases. Under Phase 1, (1995 - 1999) the NGC team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. Two half-span 16% scale wind tunnel models, representative of an advanced military aircraft wing, one with conventional control surfaces and the other with shape memory alloy (SMA) actuated smart control surfaces, were fabricated and tested in the NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) wind tunnel during two series of tests, conducted in May 1996 and June 1998, respectively. Details of the Phase 1 effort are documented in several papers. The on-going Phase 2 effort discussed here was started in January 1997 and includes several significant improvements over Phase 1: 1) a much larger, full-span model; 2) both leading edge (LE) and trailing edge (TE) smart control surfaces; 3) high-band width actuation systems; and 4) wind tunnel tests at transonic Mach numbers and high dynamic pressures (up to 300 psf.) representative of operational flight regimes. Phase 2 includes two wind tunnel tests, both at the NASA LaRC TDT - the first one was completed in March 2000 and the second (and final) test is scheduled for April 2001. The first test-demonstrated roll-effectiveness over a wide range of Mach numbers achieved using a combination of hingeless, smoothly contoured, SMA actuated, LE and TE control surfaces. The second test addresses the development and demonstration of high bandwidth actuation. An overview of the Phase 2 effort is presented here; detailed discussions of the wind tunnel testing, model design and fabrication, and actuation system development are given in companion papers.

Designing a radically different product requires learning and discovery, as well as experience and analysis. Among recent radically different products are UAV designs such as morphing wings that change shapes during their mission. These small vehicles have limited control energy. Aeroelastic effects provide one method for leveraging limited control energy if the internal structure is compatible with the flight controllers. As a result, structural design must be more detailed during the conceptual design phase if a wide variety of options or "what ifs?" must be considered. This paper describes an effort to improve the aeroservoelastic structure conceptual design process so that learning is improved and morphing wing innovation is supported. This approach uses formal multidisciplinary analysis and optimization tools with multidisciplinary objectives and constraints to populate design space with alternative designs with different forms, performance and weight. An essential requirement for this process is a structural finite element code and generic structural models that can be used to define the structural form that best integrates with the aeroelastic controllers. The features of the process will be demonstrated with an aeroelastic wing design problem. 1.1 Integrated design and morphing aircraft "Integrated design" is a general phrase used for aircraft design activities that have multiple objectives. Integration outcomes always depend on which discipline is allowed to dominate the integration effort. In the earliest design phases, aerodynamics and performance dominate; the structural design appears as a "cartoon" whose details are to be addressed later. This approach restricts design freedom and learning about synergistic features of the design. Structural optimization usually comes into play only after the wing planform and outer mold lines are fixed.

The purpose of this workshop was to provide an in-depth look at the progress in active materials and smart structures with an emphasis on Air Force systems. The technology of smart structures promises a large number of potential uses and performance enhancements for air vehicles and space systems. This workshop brought together researchers from academia, the national labs, and the aerospace industry with the focus of the discussion on Air Force systems. Every effort was made to make the workshop a two-way stream and expose researchers to the problems and needs of the Air Force as well as presenting state-of-the-an research related to active materials and smart structures. Topics discussed were, among others, actuator/sensor concepts, aerodynamic control using active materials, active propulsion systems, and smart space systems.

The DARPA/AFRL/NASA Smart Wing program, conducted by a team led by Northrop Grumman Corporation (NGC) under the DARPA Smart Materials and Structures initiative, addresses the development of smart technologies and demonstration of relevant concepts to improve the aerodynamic performance of military aircraft. This paper presents an overview of the smart wing program. The program is divided into two distinct phases. Under Phase 1, (Jan 1995 - Feb 1999) the NGC team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. A smart wing 16% scale wind tunnel model, representative of an advanced military aircraft wing, was fabricated and tested in the NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) wind tunnel during two series of tests, conducted in May 1996 and June 1998, respectively. The smart wing model incorporated contoured, hingeless flap and aileron designs actuated using built-in SMA tendons. Control surface deflections of up to 10 degrees were obtained. Variable spanwise twist of the model was achieved using SMA torque tubes that employed novel connection mechanisms to effect a high degree of torque transfer to the structure. Up to 5 degrees of twist at the tip was demonstrated. Under steady-state conditions, performance improvements of 8-12% in comparison to a conventional design incorporating hinged control surfaces, over a broad range of wind tunnel and model test conditions, were established. The paper summarizes the Phase 1 effort. Detailed discussions of the wind tunnel testing, model design and fabrication, and torque tube development, are presented in References 6-8. An important limitation of the Phase 1 effort, i.e., the limited band-width provided by the SMA based actuation mechanisms, is being addressed in Phase 2 by developing and validating hybrid concepts. Phase 2 research and development is focused on application of smart technologies to uninhabited air vehicles (UAVs) that (from a scaling standpoint), offer a higher near-term technology transition potential than their tactical aircraft counterparts. Phase 2 efforts are also discussed, albeit briefly, in the paper.

A general Entropy Generation Minimisation (EGM) technique is applied to analyse the feasibility of energy recovery from aircraft avionics via thermoelectric (TE) devices. In employing this approach, a suitable control volume definition is chosen to evaluate the impact of an energy recovery system on the overall entropy generation of the aircraft over a mission. Only those systems which are affected by the energy harvesting system are considered. As importantly, the analysis helps to identify the technical thresholds, which must be realised in order to make avionic energy harvesting via thermoelectric devices practical. This result has exciting implications for the use of this tool for helping to prioritise research directions. Relative to the energy harvesting application from the radar array on a high efficiency aircraft, the results from this approach show that a majority of the entropy generation and fuel exergy wastage is associated with the avionics cooling system due the transfer of heat to the cooling system and to the large mass/power ratio associated with cooling systems.

Herpes viruses and Candida albicans are among the most common opportunistic pathogens infecting patients with neoplastic disease, especially those patients receiving cancer chemotherapy. Herpes virus infections have increased as treatment of oncological disease has become more aggressive and immunosuppression disorders have become more prevalent. Herpes simplex virus on the lips and mouth of a patient receiving chemotherapy can progress to multiple lesions in the mouth, larynx, and in rare instances can lead to pneumonitis and widely disseminated infection. The management and dental findings of a 13-year-old patient with acute lymphocytic leukemia are described.

Rotor blade optimization with blade airfoil Reynolds numbers between 100 000 and 500 000 — characteristic of small single-rotor unmanned aerial vehicles (UAV) — was performed for hover using blade element momentum theory (BEMT) and demonstrated via flight tests. BEMT was used to test various airfoil profiles and rotor blade shapes using airfoil data from 2D computational fluid dynamics simulations with Reynolds numbers representative of the blade elements. Selected blade designs were manufactured and flight tested on a Blade 600X single main-rotor UAV (671 mm blade radius) to validate the theoretical results. The parameters considered during the optimization process were the rotor frequency, radius, taper ratio, twist, chord length, airfoil profile, and blade number. The best of the improved blade designs increased the figure of merit, a measure of rotor efficiency, from 0.31 to 0.68 and reduced power consumption by 54%. Reducing the rotational frequency accounted for 45% of the improvement in power consumption, while the taper ratio and blade number accounted for 25% and 17%, respectively. The blade twist and airfoil profile only had a minor effect on the power consumption, contributing 7% and 6% to the improvement. The rotor diameter and root chord were kept identical to the original rotor and hence had no contribution. The presented results could serve as useful guidelines to single-rotor UAV manufacturers and operators for increasing endurance and payload capabilities.