Composite Materials

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

2. Lysle Wood Professor
• Goals of the Professorship
– Make a positive and significant impact on aerospaceMake a positive and significant impact on aerospace
technology nationally and in Montana
– Provide support for aerospace related faculty
d ldevelopment
– Enhance student learning opportunities for aerospace
related engineering careersrelated 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 3501 6 for– Hygrothermal characterization of Carbon, Glass, and Kevlar with Hercules 3501-6 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 resistance andg
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 militar and commercial aerospace primar str ct ral applications– materials for military and commercial aerospace primary structural 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 technologyon 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
Design and Analysis of Aircraft Structures 13-3
• Private Pilot Certificate, 2006
• FAA Consultant for developing composite materials specifications for General
Aviation Aircraft

4. Introduction
• Composite materials are used more and more forp
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 materialg
• 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 MilitaryApplications to expensive structures (often Military
Aerospace)
• Applications to stuff rich people buy
• Applications to things you and I can afford
K A ti R t i l lti t lKey Assumption: Raw materials are ultimately
inexpensive and materials synthesis is ultimately
inexpensivep
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 platesp
• Very Expensive Applications
– Art Deco furnishings in the 1920s and 1930s
Milit i ft d i WW II– Military aircraft during WW II
• Stuff that rich people buy (Post WW II through 1960s)
– General Aviation
– Boats
– Bicycles
Toda• 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 Fibers Kevlar Fibers
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
fiber bicycle used byRadius developed Swix carbon fiber
G
y y
Lance Armstrongski poles; have been used by Gold
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 Structuresp
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 CompositeMatrix
• Good shear properties
Low density
• High strength
High stiffness
• High strength
High stiffness• Low density• High stiffness
• Low density
• High stiffness
• Good shear properties
• Low density
Design and Analysis of Aircraft Structures 13-15
y

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
fibersfibers
• Much more sensitive to fiber mis-alignment fromg
manufacturing process
Design and Analysis of Aircraft Structures 13-17

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

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 onfuselage 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 B i it t l ith d i dli d id th l b l ifor Boeing as it struggles with dwindling orders amid the global recession.
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 to which the arrow is pointing.a a to c t e a o s po t g
• 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
[45/0/-45/90] s
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
Tapes or undirectional tapes
Design and Analysis of Aircraft Structures 13-21
midplane. A subscript “S” is used to indicate that the code for only one
half of the laminate is shown.

22. Shorthand Laminate Orientation Code
Fabrics and Tapes and Fabrics
[(45)/(0)/(45)]
Midplane
• 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
[(45)/0(-45)/90]
Fabrics
g g p
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
Midplane
p g
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.
Tapes & Fabrics
Design and Analysis of Aircraft Structures 13-22
p

23. Fatigue Performance of Composites Exceeds
That of Metals
(Reference only)
1.00
Maximum
25/50/25/ Gr/Ep
0.75
cyclic
stress/ultimate
stress
0.50
Room
temperature
0.25
7075-T6 aluminum
temperature,
dry
• R = -1.0
• K1 = 3.0
0
102 103 104 105 106 107
Design and Analysis of Aircraft Structures 13-23
Cycles to failure

24. Reduced Corrosion Problems With
Advanced Composites
• Advanced composites do not corrode like metals—
the combination of corrosion and fatigue crackingg g
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)
Design and Analysis of Aircraft Structures 13-25
compression and decompression pressurization cycles from short hops)
• Operated in moist, warm environment (chemical processes exponential
with temperature)

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

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

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

31. FAA/JAA Requirements for
Material Allowables
• FAR 25.613, “Material Strength PropertiesFAR 25.613, Material Strength Properties
– Statistical basis
– Environmental effects accounted for
– MIL-H-17B
• FAR 25.615, “Design Properties”, g 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
Design and Analysis of Aircraft Structures 13-31
, ,
FAA regulations

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– 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 25 605 and 25 609 similar to FAA
Design and Analysis of Aircraft Structures 13-32
JAR 25.603, 25.605, and 25.609 similar to FAA
regulations

33. FAA/JAA Advisories That Govern
Composite Materials
• FAA AC 20-107A, “Composite Aircraft Structure”, p
– 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 25.603, “Composite Aircraft Structure”
Design and Analysis of Aircraft Structures 13-33
• Similar to FAA AC 20-107A

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

35. 777 Composite Primary Structure
Certification
Sequence Load Description Sequence Load Description
1 Limit proof Load 4 Strain surveyp
a. Up bending
b. Up bending/unsymmetric
c. Down bending
d. Down bending/
5
6
7
y
Fatigue spectrum
Strain survey
Ultimate load strain survey
a. Stall buffet
2
g
Unsymmetric
e. Stall buffet (unsymmetric)
Strain survey 8
b. Up bending
c. Down bending
Destruction test -
d b di
Design and Analysis of Aircraft Structures 13-35
Fatigue spectrum3 down bending

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• 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)– Critical weight reduction (empennage, wings, fuselage, etc).
• Use must be justified by weighing benefits against costs.
Design and Analysis of Aircraft Structures 13-40