1. Ahmed W. Moustafa Lecture (1)
Composite Materials
Ahmed W. Moustafa
Lecture (1)

2. Composite Material
Two inherently different materials that when combined together produce a material with properties that exceed the constituent materials.

3. Composite Material Defined
A materials system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents

4. Composite Material Defined
Examples:
Cemented carbides (WC with Co binder)
Plastic molding compounds containing fillers
Rubber mixed with carbon black
Wood (a natural composite as distinguished from a synthesized composite)

5. Why Composites are Important
Composites can be very strong and stiff, yet very light in weight, so ratios of strength‑to‑weight and stiffness‑to‑weight are several times greater than steel or aluminum
Fatigue properties are generally better than for common engineering metals
Toughness is often greater too
Composites can be designed that do not corrode like steel
Possible to achieve combinations of properties not attainable with metals, ceramics, or polymers alone

6. Disadvantages and Limitations
Properties of many important composites are anisotropic ‑ the properties differ depending on the direction in which they are measured – this may be an advantage or a disadvantage
Many of the polymer‑based composites are subject to attack by chemicals or solvents, just as the polymers themselves are susceptible to attack
Composite materials are generally expensive
Manufacturing methods for shaping composite materials are often slow and costly

7. Classification of Composite Materials
Traditional composites – composite materials that occur in nature or have been produced by civilizations for many years
Examples: wood, concrete, asphalt
Synthetic composites - modern material systems normally associated with the manufacturing industries, in which the components are first produced separately and then combined in a controlled way to achieve the desired structure, properties, and part geometry

8. Components in a Composite Material
Nearly all composite materials consist of two phases:
Primary phase - forms the matrix within which the secondary phase is imbedded
Secondary phase - imbedded phase sometimes referred to as a reinforcing agent, because it usually serves to strengthen the composite
The reinforcing phase may be in the form of fibers, particles, or various other geometries

9. Functions of the Matrix Material (Primary Phase)
Provides the bulk form of the part or product made of the composite material
Holds the imbedded phase in place, usually enclosing and often concealing it
When a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent

10. Composites Offer High Strength Light Weight Design Flexibility
Consolidation of Parts
Net Shape Manufacturing

11. Fiber Reinforced Polymer Matrix
Transfer Load to Reinforcement
Temperature Resistance
Chemical Resistance
Reinforcement
Tensile Properties
Stiffness
Impact Resistance

12. Design Objective Performance: Strength, Temperature, Stiffness
Manufacturing Techniques
Life Cycle Considerations
Cost

13. Matrix Considerations
End Use Temperature
Toughness
Cosmetic Issues
Flame Retardant
Processing Method
Adhesion Requirements

14. Matrix Types Polyester
Polyesters have good mechanical properties, electrical properties and chemical resistance. Polyesters are amenable to multiple fabrication techniques and are low cost.
Vinyl Esters
Vinyl Esters are similar to polyester in performance. Vinyl esters have increased resistance to corrosive environments as well as a high degree of moisture resistance.

15. Matrix Types
Epoxy
Epoxies have improved strength and stiffness properties over polyesters. Epoxies offer excellent corrosion resistance and resistance to solvents and alkalis. Cure cycles are usually longer than polyesters, however no by-products are produced.
Flexibility and improved performance is also achieved by the utilization of additives and fillers.

16. Reinforcement Fiber Type Fiberglass Carbon Aramid Textile Structure
Textile Structure
Unidirectional
Woven
Braid

17. E-glass: Alumina-calcium-borosilicate glass (electrical applications)
Fiberglass
E-glass: Alumina-calcium-borosilicate glass
(electrical applications)
S-2 glass: Magnesuim aluminosilicate glass
(reinforcements)
Glass offers good mechanical, electrical, and thermal properties at a relatively low cost.
E-glass S-2 glass
Density g/cc 2.46 g/cc
Tensile Strength 390 ksi 620 ksi
Tensile Modulus msi 13 msi
Elongation 4.8% 5.3%

18. Aramid Kevlar™ & Twaron™
Para aramid fiber characterized by high tensile strength and modulus
Excellent Impact Resistance
Good Temperature Resistance
Density g/cc
Tensile Strength 400 ksi
Tensile Modulus 18 Msi
Elongation 2.5%

19. Carbon Fiber PAN: Fiber made from Polyacrylonitrile precursor fiber
High strength and stiffness
Large variety of fiber types available
Standard Modulus Intermediate Modulus
Density g/cc g/cc
Tensile Strength 600 ksi ksi
Tensile Modulus 33 Msi 42 Msi
Elongation 1.8 % %

20. Weight Considerations
Aramid fibers are the lightest
g/cc
Carbon
1.79 g/c
Fiberglass is the heaviest
2.4 g/cc

21. Strength Considerations
Carbon is the strongest
ksi
Fiberglass
ksi
Aramids
400 ksi

22. Kevlar is the toughest Fiberglass Carbon
Impact Resistance
Kevlar is the toughest
Fiberglass
Carbon

23. Stiffness Considerations
Carbon is the stiffest
30-40 msi
Aramids
14 msi
Fiberglass
10-13 msi

24. Cost Considerations Fiberglass is cost effective $5.00-8.00/lb.
Aramids
$20.00/lb
Carbon
$30.00-$50.00/lb

25. Fabric Structures
Woven: Series of Interlaced yarns at 90° to each other
Knit: Series of Interlooped Yarns
Braided: Series of Intertwined, Spiral Yarns
Nonwoven: Oriented fibers either mechanically, chemically, or thermally bonded

26. Woven Fabrics
Basic woven fabrics consists of two systems of yarns interlaced at right angles to create a single layer with isotropic or biaxial properties.

27. Construction (ends & picks) Weight Thickness Weave Type
Physical Properties
Construction (ends & picks)
Weight
Thickness
Weave Type

28. Components of a Woven Fabric

29. Basic Weave Types
Plain Weave

30. Basic Weave Types
Satin 5HS

31. Basic Weave Types
2 x 2 Twill

32. Basic Weave Types
Non-Crimp

33. Braiding
A braid consists of two sets of yarns, which are helically intertwined.
The resulting structure is oriented to the longitudinal axis of the braid.
This structure is imparted with a high level of conformability, relative low cost and ease of manufacture.

34. Braid Structure

35. Types of Braids

36. Triaxial Yarns
A system of longitudinal yarns can be introduced which are held in place by the braiding yarns
These yarns will add dimensional stability, improve tensile properties, stiffness and compressive strength.
Yarns can also be added to the core of the braid to form a solid braid.

37. Conclusions Composite materials offer endless design options.
Matrix, Fiber and Preform selections are critical in the design process.
Structures can be produced with specific properties to meet end use requirements.