Dr. Douglas S. Cairns, Lysle A. Wood Distinguished Professor. Department of Mechanical and Industrial Engineering Montana State University

Transcription

1 Composite Materials for Aircraft Structures Dr. Douglas S. Cairns, Lysle A. Wood Distinguished Professor Department of Mechanical and Industrial Engineering Montana State University ME 463 Composites, Fall 2009

2 Lysle Wood Professor Goals of the Professorship Make a positive and significant impact on aerospace technology nationally and in Montana Provide support for aerospace related faculty development Enhance student learning opportunities for aerospace related engineering careers Design and Analysis of Aircraft Structures 13-2

3 Cairns Background Began composites career in 1978 as a Staff Engineer at the University of Wyoming Characterization of compression fatigue mechanisms of F18 vertical stabilizer (AS1/3501-6) for Navy Hygrothermal characterization of Carbon, Glass, and Kevlar with Hercules for Navy and Army Senior Engineer, Hercules Aerospace, Magna UT (designed and analyzed space and aircraft structures manufactured from composite materials) Ph.D. in Aeronautics and Astronautics, MIT, thesis on damage resistance and damage tolerance due to impact damage in carbon/epoxy and kevlar/epoxy structures, research sponsored by FAA Manager of Composites Technology, Hercules Materials Company US largest manufacturer of structural carbon fibers materials for military and commercial aerospace primary structural ral applications Radius Engineering Board of Directors since 1988 Joined Mechanical and Industrial Engineering at Montana State University in 1995, began working on wind turbine blade structures, <$10/lb final part cost target based on aerospace technology Teamed with Boeing engineers to develop and implement Aircraft Structures course at MSU Former Chairman, AIAA Materials Technical Committee Co-Chairman Damage Tolerance Committee NASA/ MIL HDBK 17 Composites Private Pilot Certificate, 2006 FAA Consultant for developing composite materials specifications for General Aviation Aircraft Design and Analysis of Aircraft Structures 13-3

4 Introduction Composite materials are used more and more for primary structures in commercial, industrial, aerospace, marine, and recreational structures Design and Analysis of Aircraft Structures 13-4

5 Composites: Composites materials consist of a fibrous reinforcements bonded together with a matrix material Occur naturally in your bones, in wood, horns etc. Allow the stiffness and strength of the material to change with direction of loading Design and Analysis of Aircraft Structures 13-5

6 The Hierarchy for Advanced Structural Materials Begin as laboratory curiosity Applications to expensive structures (often Military Aerospace) Applications to stuff rich people buy Applications to things you and I can afford Key Assumption: Raw materials are ultimately t l inexpensive and materials synthesis is ultimately inexpensive Design and Analysis of Aircraft Structures 13-6

7 Case History- Aluminum At one time, more rare than gold and silver; Kings and Queens wanted aluminum plates Very Expensive Applications Art Deco furnishings in the 1920s and 1930s Military aircraft during WW II Stuff that rich people buy (Post WW II through 1960s) General Aviation Boats Bicycles Today Aluminum BBQ grills at K-Mart Aluminum shower curtain rods at hardware store Design and Analysis of Aircraft Structures 13-7

8 Composites: Fiberglass Carbon Fibers Fibers Kevlar Fibers Design and Analysis of Aircraft Structures 13-8

9 Radius Engineering- Salt Lake City, Utah Radius developed Swix carbon fiber ski poles; have been used by Gold medal Olympic skiers since 1990s Radius developed the Trek carbon fiber bicycle used by Lance Armstrong Design and Analysis of Aircraft Structures 13-9

10 Discussion Objective Provide a brief introduction to composite materials and structures in Airplane Structures Design and Analysis of Aircraft Structures 13-10

11 Composites are Damage Tolerant F18 Midair Collision (Circa 2002, no injuries) Design and Analysis of Aircraft Structures 13-11

12 Composites are Damage Tolerant (cont.) Design and Analysis of Aircraft Structures 13-12

13 Composites are Damage Tolerant (cont.) Design and Analysis of Aircraft Structures 13-13

14 Composite Vertical Stabilizer and Rudder Damage Design and Analysis of Aircraft Structures 13-14

15 Composition of Composites Fiber/Filament Reinforcement Matrix Composite High strength High stiffness Low density Good shear properties Low density High strength High stiffness Good shear properties Low density Design and Analysis of Aircraft Structures 13-15

16 Carbon is the Emperor Typical large tow properties Design and Analysis of Aircraft Structures 13-16

17 The Emperor s New Clothes Two Basic Facts Hamper Application of Carbon Fibers to Primary Structure Carbon Fiber is expensive; about 8X-10X E-glass fibers Much more sensitive to fiber mis-alignment from manufacturing process Design and Analysis of Aircraft Structures 13-17

18 Not Just An Academic Exercise Consequence of Misalignment in Large, Composite Structure Design and Analysis of Aircraft Structures 13-18

19 To help protect your privacy, PowerPoint prevented this external picture from being automatically downloaded. To download and display this picture, click Options in the Message Bar, and then click Enable external content. The Emperor s New Clothes Two Basic Facts Hamper Application of Carbon Fibers to Primary Structure updated 3:56 p.m. MT, Fri., Aug 14, 2009 Boeing Co. has discovered another problem with its long-delayed 787 jetliner, prompting the aircraft maker to halt production of fuselage sections at a factory in Italy. The Chicago-based company found microscopic wrinkles in the skin of the 787 s fuselage and ordered Italian supplier Alenia Aeronautica to stop making sections on June 23, spokeswoman Lori Gunter said Friday. Boeing has started patching the areas. The plane, built for fuel efficiency from lightweight carbon composite parts, is a priority for Boeing as it struggles with dwindling dli orders amid the global l recession. Design and Analysis of Aircraft Structures 13-19

20 Difficult to Control Manufacturing Defects in Production Design and Analysis of Aircraft Structures 13-20

21 Shorthand Laminate Orientation Code Tapes or Undirectional Tapes [45/0/-45/90 2 /-45/0/45 [45/0/-45/90] s Tapes or undirectional tapes Each lamina is labeled by its ply orientation. Laminae are listed in sequence with the first number representing the lamina a to which the arrow is pointing. Individual adjacent laminae are separated by a slash if their angles differ. Adjacent laminae of the same angle are depicted by a numerical subscript indicating the total number of laminae which are laid up in sequence at that angle. Each complete laminate is enclosed by brackets. When the laminate is symmetrical and has an even number on each side of the plane of symmetry (known as the midplane) the code may be shortened by listing only the angles from the arrow side to the midplane. A subscript S is used to indicate that the code for only one half of the laminate is shown. Design and Analysis of Aircraft Structures 13-21

22 Shorthand Laminate Orientation Code Fabrics and Tapes and Fabrics [(45)/(0)/(45)] Midplane Fabrics [(45)/0(-45)/90] Midplane Tapes & Fabrics When plies of fabric are used in a laminate. The angle of the fabric warp is used as the ply direction angle. The fabric angle is enclosed in parentheses to identify the ply as a fabric ply. When the laminate is composed of both fabric and tape plies (a hybrid laminate). The parentheses around the fabric plies will distinguish the fabric plies from the tape plies. When the laminate is symmetrical and has an odd number of plies, the center ply is overlined to indicate that it is the midplane. Design and Analysis of Aircraft Structures 13-22

23 Fatigue Performance of Composites Exceeds That of Metals 1.00 (Reference only) Maximum cyclic stress/ultimate stress /50/25/ Gr/Ep Room temperature, dry R = -1.0 K 1 = T6 aluminum Cycles to failure Design and Analysis of Aircraft Structures 13-23

24 Reduced Corrosion Problems With Advanced Composites Advanced composites do not corrode like metals the combination of corrosion and fatigue cracking is a significant problem for aluminum commercial fuselage structure. Design and Analysis of Aircraft Structures 13-24

25 Corrosion Case History Aloha Airlines Low time airframe (but many Ground-Air-Ground cycles, 89,090 compression and decompression pressurization cycles from short hops) Operated in moist, warm environment (chemical processes exponential with temperature) Design and Analysis of Aircraft Structures 13-25

26 767 Exterior Composite Parts Design and Analysis of Aircraft Structures 13-26

27 Honeycomb Usage Design and Analysis of Aircraft Structures 13-27

28 Summary Advantages and Disadvantages of Composite Materials Advantages Weight reduction (approximately 20-50%) Corrosion resistance Fatigue resistance Tailorable mechanical properties Sales through h offset Lower assembly costs (fewer fasteners, etc.) Disadvantages Some higher recurring costs Higher nonrecurring costs Higher material costs Nonvisible impact damage Repairs are different than those to metal structure Isolation needed to prevent adjacent aluminum part galvanic corrosion Design and Analysis of Aircraft Structures 13-28

29 Material and Process Specifications Material specifications Supplier qualification Fiber requirements Prepreg requirements Fiber volume Resin chemistry Mechanical properties Forms (tape, fabric) Cure cycle Quality controls Manufacturing characteristics Incoming and receiving tests Process specifications Storage and handling Cure cycle Layup and bagging procedures In-process quality control Postprocess quality control Acceptable anomalies Splicing Design and Analysis of Aircraft Structures 13-29

30 Building Block Approach Environment Coupons (Thousands) Elements Joints Small Panels (Hundreds) Coupons and Elements Large Panels Subcomponents (Dozens) Mechanical properties Interlaminar properties Stress concentrations ti Durability Bolted Joints Impact damage characterization Environmental factors Materials The effects of temperature and moisture are accounted for in design values and strength properties. Components RT/Ambient Full Airplane Structure Large Panels and Test Boxes Validate design concepts Verify analysis methods Provide substantiating data for material design values Demonstrate compliance with criteria Demonstrate ability of finite element models to predict strain values Analysis Thermal and moisture strains calculated using finite element model for each critical condition. Design and Analysis of Aircraft Structures 13-30

31 FAA/JAA Requirements for Material Allowables FAR , Material Strength Properties Statistical basis Environmental effects accounted for MIL-H-17B FAR , Design Properties A basis for single load path B basis for redundant structure FAA AC A JAR , , and similar to FAA regulations Design and Analysis of Aircraft Structures 13-31

32 FAA/JAA Regulations That Govern Structural Materials FAR , Materials Suitability and durability established by tests Conform to specifications that ensure strength Takes into account environmental conditions FAR , Fabrication Methods Fabrication methods must produce consistently sound structure (repeatability) New methods must be substantiated by tests FAR , Protection of Structure Protected against deterioration or loss of strength JAR , , and similar to FAA regulations Design and Analysis of Aircraft Structures 13-32

33 FAA/JAA Advisories That Govern Composite Materials FAA AC A, Composite Aircraft Structure Presents an acceptable but not the only means for certifying advanced composite structure FAA AC 21-26, Quality Control for the Manufacture of Composite Structure Presents an acceptable but not the only means for complying with the quality control requirement of FAR 21 JAA ACJ , Composite Aircraft Structure Similar to FAA AC A Design and Analysis of Aircraft Structures 13-33

34 Strength Reduction of Advanced Composite Materials Pristine Materials Reduction of the allowable stress Stress Allowable design region Strain Processing anomalies Surface irregularities Splicing Waviness Inclusions Voids Damage Visible damage Nonvisible damage Repair (holes, etc.) Design Environment Allowable strain reduction Design and Analysis of Aircraft Structures 13-34

35 777 Composite Primary Structure Certification Sequence Load Description Sequence Load Description 1 Limit proof Load 4 Strain survey a. Up bending b. Up bending/unsymmetric c. Down bending Fatigue spectrum Strain survey Ultimate load strain survey d. Down bending/ Unsymmetric e. Stall buffet (unsymmetric) a. Stall buffet b. Up bending c. Down bending 2 Strain survey 8 Destruction test - 3 Fatigue spectrum down bending Design and Analysis of Aircraft Structures 13-35

36 787 Airplane Approximately 50% of the airframe is made from composites; a very bold move in the commercial aircraft industry Design and Analysis of Aircraft Structures 13-36

37 Design and Analysis of Aircraft Structures 13-37

38 Design and Analysis of Aircraft Structures 13-38

39 Boeing 787 Dreamliner Logistics Design and Analysis of Aircraft Structures 13-39

40 Summary Composite parts used for aircraft applications are defined by Material, process, and manufacturing specifications. Material allowable (engineering definition). All of these have a basis in regulatory requirements. Most efficient use of advanced composites in aircraft structure is in applications with Highly loaded parts with thick gages. High fatigue loads (fuselage and wing structure, etc). Areas susceptible to corrosion (fuselage, etc). Critical weight reduction (empennage, wings, fuselage, etc). Use must be justified by weighing benefits against costs. Design and Analysis of Aircraft Structures 13-40