Advanced Structural Concepts Branch Overview

1. Advanced Structural ConceptsBranch Overview Structures Division Air Vehicles Directorate Wright Patterson AFB, OH

2. Outline • Branch Mission • Vision • Recent Highlights • CFTI Products • Team Organization • Projects • Facilities & Resources

3. Branch Mission Leads the Air Force in maturing and transitioning advanced air and space vehicle structural concepts • Plans, develops, and demonstrates innovative technologies enabling multifunctional and adaptive structural designs • Creates new design opportunities for composite/metallic/hybrid materials • Pioneers novel structural health monitoring systems and extreme environment structures to permit affordable, responsive space access and hypersonic vehicle operations • Provides expertise to industry, academia, and other government organizations on the design, development, production, and employment of revolutionary aerospace structures technologies

4. Vision SENSORCRAFT SPACE ACCESS DISTRIBUTED SUAV HUNTER/KILLER Sensing Load Bearing Actuation Cognition Thermal Mgmt Conventional Vehicles • Functional integration of disparate subsystems is an exercise in packaging • Airframe functions solely to carry loads Future Vehicles to Embody a “Living Airframe” – System Based Integration • Robust unitized structure with integrated electronic subsystems & apertures • Integrated Thermal Management & Structural state feedback control • Systems will be scalable & dynamic - SUAV networked sparse array • Adaptive and Reconfigurable – Airframes capable of configuration changes Airframes operating at “natures limits”, continuously sensing the environment, measuring performance and adapting to optimize effectiveness Optimized Airframe “System”

5. Recent Accomplishment Highlights • Durable Hot Structure • Thermal Protection Systems • 100x Durability Increase • 100x Decrease in TPS Remove & Replace Time • Detect and Assess Damage to the System • Enables Next Gen Launch • Hardware in the Loop ISHM Simulation • Flight Test of Structural Health Monitoring • Breaks Sensor/Struct Integ Paradigm • HALE ISR Enabled • Large Low/High Frequency Arrays • Small UAV Antenna Structure

6. Recent Accomplishment Highlights • Morphing Shown to Enable Dramatic Reduction in Req’d Sorties • Working with ACC to Define Next Gen Hunter Killer Vehicle Concept • Demonstrated Self Repairing Structure • Nano Enhanced Joining for High Temperature Structures • Structural Capacitor Energy Storage • Will Enable DE on Small Aircraft • Patent # 6,981,671 Awarded

7. Focused Long Term ChallengesStructural Concept Linkages

8. Adaptive Structures Adv Structures Concepts Structural Health Assessment Thermal Structures Multi- Functional Structures Advanced Structural Concepts Branch Team Organization

9. Advanced Structures Concepts Team • Vision • Promote dominance in combat by the United States Air Force, and improved • safety of air travel through better performing aircraft • Mission • Lead technology demonstration efforts to generate fundamental change in the structural architecture of future airframes • Goals • Exploit emerging materials and manufacturing technologies to conceive new innovative structural concepts for aircraft • Develop those concepts and appropriate design methods, validate structural safety and performance, demonstrate readiness for transition • Payoffs • Improve ALL aspects of structural performance • Increase Strength, durability, damage tolerance, and reliability, • Reduce weight, cost, and risk Dick Holzwarth

10. Advanced Aluminum AerostructuresInitiativeDeveloping New Technology - Solving Current Problems C-17 Cargo Ramp Extension • Aluminum machined FSW sandwich structure replaces built-up honeycomb • 40% weight reduction • Cost neutral (based on 600 C-130’s in service) • Forged and High Speed Machined One-piece Frame with Separate Aluminum Skin • 30% cost reduction • 92 fewer part count (81% reduction) • Better impact damage tolerance • Replaceable and interchangeable • Snap Lock-Adhesive Bonded Joining • $6.1 million savings over the life of the F/A-22 fleet F-22 Nose Landing Gear Door C-17 Crew Emergency Escape Door

11. ACCA ApproachDevelop Composite Fuselage for Do 328J All-composite, bonded fuselage with approximately one tenth the parts of conventional designs Vertical stabilizer implementing Highly Tailored Stiffening (HiTS) Skins and cobonded assembly Growth provisions for new wing installation Growth provisions for new empennage installation High wing configuration for FOD tolerance Advanced composite, aft-loading cargo door Expanded volume non-circular fuselage to accommodate 2 - 463L Pallet with up to 4,000 lb load State-of-the-art commercial flight station controls and displays Robust advanced composite landing gear backup structure to accommodate growth high sink landing gear (up to 15 fps)

12. ACCA Composite Design ApproachUnitized Out of Autoclave Manufacture and Bonded Assembly Vertical Tail Leading Edge (4 parts) Do-328J Horiz. Stab. Do-328J Wing Do-328J Rudder Vertical Tail Assembly (62 parts) Upper Fairings (20 parts) Upper Fuselage Skin Cargo Floor (30 parts) Tail Fairing (2 parts) Lower Fuselage Skin & Frames (113 parts) Cargo Door (29 parts) Do-328J Fwd Fuselage Do-328J Main Landing Gear MLG Fairings & Doors (40 parts) 306 Structural Parts ~ 90% reduction from original Do-328J Fuselage and Vertical Tail ~98% Fastener Reduction

13. Reliability Based Design MethodsTool to DESIGN to Reliability Standards A bonded composite joint design based on air vehicle requirements has been designed using a reliability as primary measure of merit. COMPLETED TO DATE • Validated Analytical Method Against Test Data • Developed Modeling and Analysis Process • Sensitivity Model for Reliability-Based Design • Sensitivity/Design Scans • Reliability-Based Design • Verification Testing –Establish Performance Improvements • Applied to both pristine and impact damage problems PRODUCT • Validated Process for Application of Reliability-Based Methods using multiple damage models and multiple probabilistic analysis tools • Robust Design, Low Weight, Maximum Capability, Low Cost • Methods for multiple forms of damage. NEAR TERM FOCUS • Methods to analyze effects of inclusions and sensors FAR TERM OBJECTIVE • Demonstration of Reliability Based Certification Approach Global/Local FEM Analysis Detail Failure Analysis Generate Highly Reliable Design Most Efficient, Robust, High Reliability Structure

14. Reliability Analysis MethodsApplication to an Unmanned Aerial Vehicle Traditional aircraft structural design uses • Deterministic limit load cases • Nominal member thicknesses • Conservative material strength allowables • Factor of safety of 1.5 for manned aircraft • Drawbacks • No measure of design’s reliability • No measure of tradeoffs between performance and reliability Objective is to use probabilistic analysis to assess the structural reliability of a UAV and relate reliability to design factor of safety and weight A large test article, implementing mostly sandwich structures assembled using bonded pi joints, and incorporating integral antennas has been designed using this philosophy. It will be tested for durability, damage tolerance, and residual strength.

15. Thermal Structures Team • Vision • Develop airframe structures for operationally responsive spacelift, • hypersonic cruise, and prompt global strike vehicles • Mission • Lead the development of durable, reliable, and maintainable • air vehicle structures which are exposed to extreme environments • such as thermal protection systems and hot structures • Goals • Generate design requirements for structures subject to extreme environments • Advance the state of the art in thermal structures durability and operability • Develop methods for analytically predicting and experimentally validating the response and life of structures exposed to combined static, dynamic, and thermal loads • Payoffs • Shorter turn-around time for space access vehicles • Lower cost high speed vehicle operations • All weather operations for space vehicle launch and return Andy Swanson

16. Thermal StructuresThe Problem • Leading Edges • Heating of sharp edges expected to exceed material limits • May effect controllability • Will increase maintenance and turn-time Space Access • Acreage TPS • Unacceptable turn-time • Subsystem access requires destructive remove/replace • Excessive maintenance required • Damage tolerance low • Weather sensitive Hypersonic Cruise Global Strike

17. Thermal StructuresRBSA Solution Carbon-Carbon Carbon Foam Leading Edge • Leading Edges • Passive materials • Robust designs for space access vehicle wing application • Heat Pipe Cooling • Drastically lowers max temp of inlet cowls • Lower weight/complexity than active cooling Heat Pipe Cooled Leading Edge Ceramic Composite Wrapped Tile • Acreage TPS • Durable ceramic TPS • Dramatically lower damage accumulation • Lower weight • Mechanically attached TPS • Nondestructive interior access • Fast turn-around Remove Replace Mechanically Attached Blanket TPS

18. Multifunction Structures Team • Vision • Create structures capable of external sensing, energy/fluids storage and transfer, internal distributed sensing and active devices, and propulsion enhancement • Mission • Develop and demonstrate the technologies, concepts, and processes to enable structures with embedded subsystems capabilities • Goals • Merge structure design, subsystem design, and manufacture into a single discipline • Payoffs • New and overwhelming warfighter capabilities packaged in highly efficient and supportable airframes James Tuss

19. Structural ExcitationVertical Tail End Cap CLAS UHF/VHF Tail End Cap Concept F-18 Demonstration • ANTENNA GAIN Conventional blade antenna CLAS tail end cap F-35 Transition • Blade Antennas not suitable for LO and subject to damage • The CLAS end cap was flight tested with dramatic gain improvement results, as shown in the gain vs azimuth plot • The CLAS VHF end cap increased VHF voice communication range 17 fold

20. Structural X-band Array X-Band State of Art • Demonstrated New Approach to X-band Array Design F-35 Structural Antenna Array Elements RF-on-Flex • High Performance Target Cuing • Wide Band Dual Polarization Thin Profile – 1 inch Very Lightweight <8 lb/sf Very Low Cost $50k/sf (proj) Potential “First Use” Applications

21. Low Band Structural Array (LOBSTAR) Sensorcraft UHF Wing Skin Antenna Structure • LOBSTAR Sensorcraft ISR Capabilities: • Aperture for wide area air to air search radar (250 nm range, cue for x-band targeting radar) • Ground foliage penetration (60-100 km range) • 3-5 m/s minimum detect velocity (ground targets) • 360° coverage UHF Wing Skin Antenna Structures (upper and lower skins) Sensorcraft Multilayer Bonded Composite Construction Load Reaction Applied Load RF Range Test Wing Section Test Setup • Test Objectives • Characterize RF radiation patterns • Demonstrate strength and durability of LOBSTAR antenna • Demonstrate ability of antenna circuitry to survive the structural environment • Structural Test Conditions • High altitude long endurance spectrum • -100°F to 180°F ambient humidity • 2 Lifetimes fatigue • Static test to Limit Load

22. Slotted Waveguide Antenna Stiffened Structure (SWASS) F111 Panel • Concept • Use structural stiffening features as waveguides • Radiate RF signal through slots in skin • Payoffs • Very lightweight • Enables large antennas • Enables new antenna locations Conventional Slotted Waveguide Conventional Hat Stiffed Composite Skin Dr. Callus will present at the Australian International Aerospace Congress (AIAC) Congress March 2009 at the Melbourne Convention Centre SWASS Patent Disclosure Filed

23. Low Frequency Structural Antennas for Small UAVs (SUAVs) Shadow Dakota Raven Hunter Pointer Low Frequency Comm Earth Penetrating Radar Develop High Gain, Vertically Polarized, Low Frequency Capability for SUAVs Development focused on 30 MHz to 3000MHz Pointer UHF VHF HF 0 10 Ft 50 Ft 100 Ft 200 Ft Wavelength  Small UAV Dictates an Electrically Small Antenna

24. Structural Health Assessment Team Mission Lead the development and demonstration of technologies that enable real-time monitoring and assessment of aerospace vehicle structural health to extend vehicle life and reduce maintenance. Lead the integration of Structural Health Monitoring techniques with overall Integrated Vehicle Health Monitoring schemes. Mark Derriso Mission Operation Center

25. Definition of SHM • “Automated methods for determining adverse changes in the integrity of mechanical systems” SHM system must perform three major functions: Data Analysis State Sensing Structural Models Structural Health Assessment

26. Technical Challenges for Structural Sensing • Sensor Integration • Applique • Cured/Bonded layer • Sensor Development • Low/high temperature • Reliability • Frequency response • Moisture tolerance • Ingress/Egress • Wireless • Buss • Connector durability • Sensor Optimization • Location • Quantity • Data Conditioning • Local • Remote Integrated Sensor Suite

27. Fiber Optic System Magnetostrictive System Guided Lamb Wave Grip Area Patch Piezoelectric System Photoelastic System Damaged Region Strain field image Grip Area Number of Cycles Device Testing

28. Structural Health Monitoring for Bonded Repair Objective: Use structural health monitoring techniques to determine the health of a bonded repair patch • Sensor installation • Center keel area in the wheel well of the F-16 station 341 bulkhead • Piezoelectric disks in a polyimide substrate • Failure mode testing • Crack growth under the repair • Disbond of the repair • Ultimate load test F16 Advanced Technology Demonstration Bonded Repair Patches Diagnostics/Prognostics

29. SHM Flight Test • Evaluating Hardware in Flight Environments • Needs to operate in the design environment • Must survive anticipated environments that occur while system is not in operation Many Sensor Concepts will not work in Hot Spots • Require a far field stress condition • Complex geometry inhibit wave propagation algorithms • Piezoelectric sensor system • F-16 Aircraft Flight Data • No signs of degradation to date

30. Adaptive Structures Team • Vision • Become a world class team of scientist and engineers conducting research in a multidisciplinary environment • Mission • Enable new capabilities for air vehicle design through exploration, invention, and maturation of revolutionary aerospace structures capable of adapting to environmental and mission changes utilizing embedded networks of controllable active systems • Goals • Develop distributed sensor and actuation systems for structural shape control • Develop design methodologies • Explore alternative structural capabilities utilizing emerging technologies such as nano- and bio-sciences • Identify notional air vehicle concepts and missions possible with adaptive structures • Payoffs • Vastly expand the operational envelop and capability of future USAF air vehicles Dr Greg Reich

31. Timeline for AFRL’s Strategic Vision: “Ubiquitous, Swarming Sensors & Shooters” 2015 Strategic Goal: “Biomimeticbird-sized UAV platform with WMD sensing capability” 2030 Strategic Goal: “Biomimeticinsect-size UAV platform with WMD sensing, tracking and targeting capability, capable of autonomous persistent operation” • Technical approach • Fundamental unsteady aerodynamics and aeroelasticity • Transition fundamentals to vehicle design • Offramps to 2015 goal • Long-term research for 2030 goal • Vehicle flight agility • Maneuver in close-quarters • Participate in swarms • Sensors-on-target in windy/gusty environments • Follow fleeting/elusive targets • Vehicle flight efficiency • Aerodynamic • Propulsive • System (energy storage, multi-functional structures,…) 2015 Near Term 2030

32. Challenge Development of an MAV that can perform the “perch and stare” mission Based 2015 AFRL strategic goal of a “bird-sized bio-memetic MAV” Requirements Hide in plain sight Land on natural or man-made structure to “recharge”, transmit data, or perform sensing Motivation • Solution • Bio-inspired design • Bird-like MAV that can “perch” • Project Focus: • Wing Mechanization • Structural Design • Integration

33. Definition of Perching • Reduce speed and maintain lift • Land with approximately zero horizontal AND vertical velocity • Beating wings: avian stroke • Rotating wings • Assuming ascending path, exchanging kinetic energy for potential energy Lee, Davies, Green, Van Der Weel, 1993

34. Bio-Inspiration Common Pigeon 24 inch span 4.3 inch chord 306 grams Birds have three joints in each wing Our model is simplified by using 2 joints: shoulder and wrist with 1 DOF each Design Details 4 wing panels – all capable of 90º rotation Proximal operate dependently Rotated to high angles to create drag Distal operate independently Used as control surfaces Coaxial cylinder spar design 3 servo motors Actuation contained within fuselage Conceptual Design

35. Final Design Conservative design Factor of safety of 2 on max loads Servo motors Proximal: 9 grams, 90º in 0.27 sec Distal : 3.6 grams, 90º in 0.18 sec Fabrication Built by Ward Engineering, Columbus, OH Structure – Balsa Fuselage Ribs Spar – Carbon Fiber Skin – Mylar Final Mass 158 grams (51.6% of goal) Model does not include: landing gear, motor, power supply, tail, communication devices Final Design/Fabrication

36. Develop an on-board EH power train Input from any number or type of EH devices Do power conditioning, management, switching, etc. Understand energy densities, availability, and system-level impact Solar and vibration sources and devices Compare system performance trades using entropy generation analysis Energy Harvesting and Storage for MAVs Harvesting Technologies Ambient Vibrations Light Source Solar Array Vibrating Generator Storage/Management Technologies

37. AFRL DIRECTORATE FACILITIES Materials IN HOUSE FACILITIES Fatigue and Fracture Lab Combined Environment Acoustics Chamber Propulsion Sensors INDUSTRY – ACADEMIA – OTHER GOVERNMENT SubElement Facility Multi-Functional & Structures Health Monitoring Random Force Dynamic Vibration Facility for Innovative Research in Structures Technology Composite Material Fabrication Facility Mechanical Loading with Elevated Temperature Thermal Acoustic Chamber Resources-Facilities Combined EnvironmentStructural Experimental Facilities Building 65

38. In-House Research Staff Highly Educated Workforce Highly Diverse Workforce • Civilian & Military 24 • Onsite Contractors 8 • Students 5 • Visiting Scientists 4 • AFRL Collaboration 11 1 1 1 PhD-4 BS-9 3 13 MS-11 5 Expertise Structural Materials – Composite, Metallic, Ceramic, Hybrid Design -Topological Optimization, Vehicle Trades, Aeroelasticity Structural Sensors – Piezoelectric, Fiber Optics, Thin Films, Algorithms Structural Electronics - Antennas & Device/Circuits Testing – Combined Environment

39. Recognition & Products2005-2007 Technical Affiliations AIAA Technical Committees (4) Journal Associate Editors (2) Conference Chair/Co-Chair/Committee (US-6, Intl-4) RTO Working Groups (2) Peer/Committee Review Panels (2) SAE Chairman – Dayton Section Awards Composites Manufacturing Magazine 2007 Excellence & Innovation SAE Distinguished Young Member Int’l Award Industry Special Recognition Award for Prognosis and Health Mgmt RB Senior Technical Mgmt Federal Employee of the Year Finalist Products Journal Articles (9) Conference Papers (25) Patents (1) Patent Filings (2)

40. Summary Technical Quality • Leading hypersonic structures development from NASP to present • ISHM AFRL Leadership, 1ST SHM on Military Aircraft • Pioneered and led CLAS development Near Term AF Relevance • Falcon Aeroshell and X37 Flight Test • SHM on F22 & F16, Ground Test on Global Hawk • SUAV War Effort Support & XBand on AWACS Future Capability Relevance • Thermal structures for hypersonic weapons and space access • Cognitive Aircraft • Sensorcraft Resources • Excellent research staff – Broad AFRL Team • Extensive industry, academia & Gov Partnerships • Unique facilities