Composites in Aircraft - Montana State University

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1 Composite Materials for Aircraft Structures Dr. Douglas S. Cairns, Lysle A. Wood Distinguished Professor Department of Mechanical and Industrial Engineering Montana State University y 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 d development l 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 Carbon, Glass Glass, and Kevlar with Hercules 3501 3501-6 6 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 g 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 militar and commercial aerospace primar primary str structural ct 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,

4 Introduction Composite p 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 g 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 A K Assumption: ti R Raw materials t i l are ultimately lti t l inexpensive and materials synthesis is ultimately inexpensive p 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 p Very Expensive Applications Art Deco furnishings in the 1920s and 1930s Military Milit aircraft i ft during d i WW II Stuff that rich people buy (Post WW II through 1960s) General Aviation Boats Bicycles Today Toda Aluminum BBQ grills at K-Mart Aluminum shower curtain rods at hardware store Design and Analysis of Aircraft Structures 13-7

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

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

10 Discussion Objective Provide a brief introduction to composite materials and structures in Airplane p 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 Good shear properties High strength High stiffness Low density High stiffness Low density Good shear properties Low densityy 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 Emperors 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 g 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 y our priv acy , PowerPoint prev ented 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 Emperors 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 787s 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 f Boeing for B i as it struggles t l with ith dwindling d i dli orders d amid id th the global l b l recession. i http://www.msnbc.msn.com/id/32415601/ns/business-aviation/ 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/-45/902 /-45/0/45 Each lamina is labeled by its ply orientation. Laminae are listed in sequence with the first number representing the lamina a a to which c tthe eaarrow o is s po pointing. t g [45/0/-45/90] s 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. angle Each complete laminate is enclosed by brackets. When the laminate is symmetrical and has an even number on each Tapes or undirectional tapes 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 When plies of fabric are used in a laminate. The [(45)/0(-45)/90] angle of the fabric warp is used as the ply direction angle. g The fabric angle g is enclosed in p parentheses to identify the ply as a fabric ply. Midplane When the laminate is composed of both fabric and tape plies (a hybrid laminate). The parentheses around the fabric p plies will distinguish g the fabric Tapes & Fabrics plies from the tape plies. When the laminate is symmetrical and has an odd number of plies, the center ply is overlined to p 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) 25/50/25/ Gr/Ep 0.75 Maximum cyclic stress/ultimate 0.50 stress 7075-T6 aluminum 0.25 Room temperature temperature, dry R = -1.0 0 102 103 104 105 106 107 K1 = 3.0 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 g crackingg 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 SummaryAdvantages and Disadvantages of Composite Materials Advantages Disadvantages Weight reduction Some higher recurring costs (approximately 20-50%) Higher nonrecurring costs Corrosion resistance Higher material costs Fatigue resistance Nonvisible impact damage Tailorable mechanical Repairs are different than properties those to metal structure Sales S l through th h offset ff t Isolation needed to prevent Lower assembly costs adjacent aluminum part ((fewer fasteners,, etc.)) galvanic corrosion Design and Analysis of Aircraft Structures 13-28

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

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

31 FAA/JAA Requirements for Material Allowables FAR 25.613, Material Material Strength Properties Statistical basis Environmental effects accounted for MIL-H-17B FAR 25.615,, Design g Properties p A basis for single load path B basis for redundant structure FAA AC 20-107A JAR 25.613,, 25.615,, and 25.603 similar to FAA regulations Design and Analysis of Aircraft Structures 13-31

32 FAA/JAA Regulations That Govern Structural Materials FAR 25.603,, Materials Suitability and durability established by tests Conform to specifications that ensure strength Takes into account environmental conditions FAR 25.605, Fabrication Methods Fabrication methods must produce consistently sound structure (repeatability) New methods must be substantiated by tests FAR 25.609, Protection of Structure Protected against deterioration or loss of strength JAR 25.603, 25 603 25.605, 25 605 and 25.609 25 609 similar to FAA regulations Design and Analysis of Aircraft Structures 13-32

33 FAA/JAA Advisories That Govern Composite Materials FAA AC 20-107A,, Composite p Aircraft Structure Presents an acceptablebut not the onlymeans for certifying advanced composite structure FAA AC 21-26, Quality Control for the Manufacture of Composite Structure Presents an acceptablebut not the onlymeans for complying with the quality control requirement of FAR 21 JAA ACJ 25.603, Composite Aircraft Structure Similar to FAA AC 20-107A Design and Analysis of Aircraft Structures 13-33

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

35 777 Composite Primary Structure Certification Sequence Load Description Sequence Load Description 1 Limit p proof Load 4 Strain surveyy a. Up bending 5 Fatigue spectrum b. Up bending/unsymmetric 6 Strain survey c. Down bending 7 Ultimate load strain survey d. Down bending/ g a. Stall buffet Unsymmetric b. Up bending e. Stall buffet (unsymmetric) c. Down bending 2 Strain survey 8 Destruction test - 3 Fatigue spectrum d down b bending di 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 (empennage, wings wings, fuselage fuselage, etc) etc). Use must be justified by weighing benefits against costs. Design and Analysis of Aircraft Structures 13-40

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