1. WELCOME TO COMPOSITE MATERIALS
Introduction to Composite Materials Senior Elective in Mechanical Engineering Instructor: Autar Kaw

2. What are you going to learn?
What are composite materials?
How are they manufactured?
What advantages and drawbacks do composites have over metals?
Develop mathematical models to understand the mechanical response of composites to mechanical and hygrothermal loads?
Use the above mathematical models to optimally design structures made of composites.

3. What is a composite?
A composite is a structural material which consists of combining two or more constituents
Examples:
Flesh in your leg reinforced with bones
Concrete reinforced with steel
Epoxy reinforced with graphite fibers.

4. “You are no longer to supply the people with straw for making bricks; let them go and gather their own straw” - Exodus 5.7.

5. Shift in Paradigm About Materials
“More important than any one new application is the new ‘materials’ concept itself ”
Peter F. Drucker
The Age of Discontinuity, 1969

6. What is this paradigm shift in materials?
From substance to structures
From artisan to science
From workshop to mathematical modeling
From what nature provides to what man can accomplish

7. Are Composites Important?
Considered as one of the ten outstanding achievements of

8. From constituents to application

9. Chapter 1 Introduction to Composite Materials

10. Chapter 1: Objectives What is a composite?
What are the advantages and drawbacks of composites over monolithic materials?
What factors influence mechanical properties of a composite

11. Chapter Objectives (continued)
How do we classify composites?
What are the common types of fibers and matrices?
How are composite materials manufactured?
What are the mechanical properties of composite materials?

12. Chapter Objectives (continued)
Give applications of composite materials.
How are composites recycled?
What terminology is used for studying mechanics of composites?

13. What is an advanced composite?
Advanced composites are composite materials which were traditionally used in aerospace industries
Examples include graphite/epoxy, Kevlar/epoxy and Boron/aluminum

14. Examples of Natural Composites
Wood
Cellulose Fibers
Lignin Matrix
Bones
Collagen Fibers
Mineral Matrix

15. Fibrous Composites Generally there are two phases
Fiber as a reinforcement
Matrix as a binder

16. Historical Perspective
4000 B.C. Fibrous composites were used in Egypt in making laminated writing materials
1300 BC: Reference to Book of Exodus
1700 AD: French Scientist, Reumer talked about potential of glass fibers

17. Historical Perspectives (continued)
1939: Glass fiber manufactured commercially for high temperature electrical applications
1950s: Boron and carbon fibers were produced to make ropes.
1960s: Matrix added to make polymeric matrix composites

18. Historical Perspectives (continued)
1970s: Cold war forces development of metal matrix composites for military aircrafts and missile guidance systems
1990s: High temperature ceramic matrix composites are being aggressively researched for use in next generation aircraft engines and power plant turbines

19. Shipments of Composites

20. World Market of Composites

21. Advantages of Composites
Specific Strength and Stiffness
Tailored Design
Fatigue Life
Dimensional Stability
Corrosion Resistance
Cost-Effective Fabrication

22. Drawbacks of Composites
High cost of fabrication of composites
Complex mechanical characterization
Complicated repair of composite structures
High combination of all required properties may not be available

23. Composites vs. Metals

24. Composites vs. Metals
Comparison based on six primary material selection parameters

25. Why composites over metals?
High Strength and High Stiffness
Tailored Design
Fatigue Life
Dimensional Stability
Corrosion Resistance

26. Why Composites over Metals?
How is the mechanical advantage of composite measured?

27. Specific Strength vs. Year

28. Table 1.1. Specific modulus and strength of typical fibers, composites and bulk metals

29. Specific Strength vs Specific Modulus

30. Other Mechanical Parameters
Are specific modulus and specific strength the only mechanical parameters used for measuring the relative advantage of composites over metals?
NO!!

31. Tailored Design
Engineered to meet specific demands as choices of making the material are many more as compared to metals.
Examples of choices
fiber volume fraction
layer orientation
type of layer
layer stacking sequence

32. Fatigue Life Fatigue life is higher than metals such as aluminum.
Important consideration in applications such as
aircrafts
bridges
structures exposed to wind

33. Dimensional Stability
Temperature changes can result
in overheating of components (example engines)
thermal fatigue due to cyclic temperature changes (space structures)
render structures inoperable (space antennas)

34. Corrosion Resistance
Polymers and ceramics matrix are corrosion resistant
Examples include
underground storage tanks
doors
window frames
structural members of offshore drilling platforms

35. What is most limiting factor in the use of composites in structures?
Lack of engineers with the knowledge and experience to design with these materials!!!!

36. Cost Considerations
Composites may be more expensive per pound than conventional materials. Then why do we use composite materials?

37. Factors in Cost Estimate
For Composite Materials
Fewer pounds are required
Fabrication cost may be lower
Transportation costs are generally lower
Less maintenance than conventional materials is required

38. Fiber Factors
What fiber factors contribute to the mechanical performance of a composite?
Length
Orientation
Shape
Material

39. Fiber Factor - Length Long Fibers Short Fibers Easy to orient
Easy to process
Higher impact resistance
Dimensional stability
Short Fibers
Low Cost
Fast cycle time

40. Fiber Factor - Orientation
One direction orientation
High stiffness and strength in that direction
Low stiffness and strength in other directions
Multi-direction orientation
Less stiffness but more direction independent

41. Fiber Factor - Shape Most common shape is circular
Hexagon and square shapes give high packing factors

42. Fiber Factor - Material
Graphite and aramids have high strength and stiffness
Glass has low stiffness but cost less

43. Matrix Factors
What are the matrix factors which contribute to the mechanical performance of composites?
Binds fibers together
Protects fibers from environment
Shielding from damage due to handling
Distributing the load to fibers.

44. Factors Other Than Fiber and Matrix
Fiber-matrix interface
Chemical bonding
Mechanical bonding

45. Fiber Types Glass Fiber (first synthetic fiber)
Boron (first advanced fiber)
Carbon
Silicon Carbide

46. Types of Matrices
Polymers
Metals
Ceramics

47. Polymer Matrix Thermosets Thermoplastics polyester epoxy polymide
polypropylene
polyvinyl chloride
nylon

48. Metal Matrix
Aluminum
Titanium
Copper

49. Ceramic Matrix Carbon Silicon Carbide Calcium AluminoSilicate
Lithium AluminoSilicate

50. Why do fibers have thin diameter?
Less flaws
More toughness and ductility
Higher flexibility
Thin Fiber
Thick Fiber

51. Less Flaws

52. More Toughness and Ductility
Fiber-matrix interface area is inversely proportional to the diameter of the fibers
Higher surface area of fiber-matrix interface results in higher ductility and toughness, and better transfer of loads.

53. More Flexibility Flexibility is proportional to inverse of
Young’s modulus
Fourth power of diameter
Thinner fibers hence have a higher flexibility and are easy to handle in manufacturing.

54. Classification CONCRETE: Gravel, sand and cement
PAINT: Paint and aluminum flakes
GRAPHITE/EPOXYGraphite fibers in epoxy matrix

55. Polymer Matrix Composites
What are the most common advanced composites?
Graphite/Epoxy
Kevlar/Epoxy
Boron/Epoxy

56. Polymer Matrix Composites
What are the drawbacks of polymer matrix composites?
Low operating temperatures
High CTE and CMEs
Low elastic properties in certian directions

57. Are Carbon and Graphite the Same?No
Carbon fibers have 93%-95% carbon content and graphite has >99% carbon content
Carbon fibers are produced at 2400o F and graphite fibers are produced at 3400o F

58. Table 1.4. Typical mechanical properties of polymer matrix composites and monolithic materials

59. Comparative Stiffness of PMCs and Metals

60. How to make a PMC

61. Schematic of Prepreg Manufacturing

62. Prepreg Boron/Epoxy

63. Autoclave Lamination

64. Filament Winding

65. Resin Transfer Molding

66. Common PMC Fibers & Matrices
Graphite
Glass
Kevlar
Matrices
Epoxy
Phenolic
Polyester

67. Table 1.5 Typical mechanical properties of fibers used in polymer matrix composites

68. Cost Comparison of PMC fibers
Type of fiber Cost ($ per pound)
A-glass
C-glass
E-glass
S-2 Glass
Heavy Tow
Medium Tow
Low Tow
Kev
Kev

69. Manufacturing of Glass Fibers

70. Glass Fiber Types E-glass (fiberglass) - electrical applications
S-glass - strength applications
C-glass - Corrosion resistant
D-glass - Low dielectric applications
A-glass - Appearance applications
AR-glass - Alkali resistant

71. Table 1.6 Comparison of properties of E-glass and S-glass

72. Table 1.7 Chemical Composition of E-Glass and S-glass Fibers

73. Fig 1.10 Forms of Fibers

74. Fig 1.11 Manufacturing Graphite Fibers

75. Resin Systems
Polyester
Phenolics
Epoxy
Silicone
Polymide

76. Properties of epoxy

77. Curing Stages of Epoxy

78. Comparison of Resins

79. Difference between thermosets and thermoplastics

80. Pre-Preg Graphite/Epoxy

81. Application of Polymer Matrix Composites
A strong, ultralight leg prosthesis of graphite/epoxy helps an athelete compete in world-class bicycle race.

82. Space Shuttle

84. Lear Fan

85. Fighter Jets

86. Corvette Leaf Springs

87. Snow Skis

88. Space Shuttle

89. I-beam

90. Pressure vessels

91. Metal Matrix Composites
What are metal-matrix composites?
Metal matrix composites have a metal matrix.
Examples include silicon carbide fibers in aluminum, graphite fibers in aluminum.

92. Advantages of MMCs Higher specific strength and modulus over metals.
Lower coefficients of thermal expansion than metals by reinforcing with graphite.
Maintenance of high strength properties at high temperatures.

93. Degrading properties in MMCs (Fig 1.3)
Are there any properties which degrade when metals are reinforced with fibers?
Yes, they may have reduced ductility and fracture toughness.

94. Typical mechanical properties of metal matrix composites

95. Boron Fiber

96. Step 0: Cutting the shape

97. Step 1: Apply Aluminum File

98. Step 3: Lay Up Desired Plies

99. Step 4:Vacuum the specimen

100. Step5: Heat to Fabrication Temperature

101. Step 6: Apply Pressure and Hold for Consolidation Cycle

102. Step 7: Cool, Remove and Clean Part

103. Schematic of Diffusion Bonding

104. Silicon Carbide/ Aluminum Composite

105. Application of MMCs

106. Application of MMCs

107. Application of MMCs

108. Ceramic Matrix Composites
What are ceramic matrix composites?
Ceramic matrix composites have matrices of alumina, calcium alumino silicate (CAS), lithium alumino silicate (LAS). Examples include Silicon Carbide/CAS and Carbon/LAS.

109. Owens Corning Webster about CMS
Advantages of CMCs
High strength, hardness and high service temperatures
Chemical inertness
Low Density
Owens Corning Webster about CMS

110. Table 1.12 Typical fracture toughness of monolithic materials and ceramic matrix composites

111. Table 1.13 Typical mechanical properties of some ceramic matrix composites

112. Manufacturing of Ceramic Matrix Composites - Slurry Infiltration

113. Application of CMCs

114. Carbon-Carbon Compoistes
What are carbon-carbon composites?
Carbon - Carbon composites have carbon fibers in carbon matrix.

115. Advantages of Carbon-Carbon Composites
Gradual failure
Withstand high temperatures
Low creep at high temperatures
Low density
High thermal conductivity
Low and tailorable Coefficient of Thermal Expansion

116. Advantages of Carbon-Carbon Composites
Great strength to weight ratio
High modulus, thermal conductivity, and electrical conductivity
Good thermal shock resistance, abrasion resistance, and fracture toughness
Excellent high temperature durability in inert or vacuum environment
Good corrosion resistance

117. Table 1.14 Typical mechanical properties of carbon-carbon matrix composites

118. Carbon-Carbon Manufacturing (Fig 1.34)

119. Applications of C-C Composites
Space Shuttle Nose Cones
Re-entry temperature of 3092 K
Aircraft Brakes
Saves 450 kgs of mass
Two-four times durability vs. steel
2.5 times specific heat of steel

120. Applications of Carbon-Carbon Composites

121. Recycling of Composites
What types of process are used for recycling of composites?
Why is recycling of composites complex?
What can one do if one cannot separate different types of composites?

122. Recycling Continued
What are the various steps in mechanical recycling of short fiber-reinforced composites?
Where are mechanically recycled short fiber composites used?

123. Chemical Recycling
Why is chemical recycling not as popular as mechanical recycling?
Which chemical process shows the most promise?

124. Definitions Isotropic body Homogeneous body Anisotropic body
Nonhomogeneous body
Lamina
Laminate

125. Schematic of Analysis of Laminated Composites

126. An Artist’s Rendition of a Composite Material