Classification

• CONCRETE: Gravel, sand and cement

• PAINT: Paint and aluminum flakes

• GRAPHITE/EPOXYGraphite fibers in epoxy matrix

Particulate Composites

Flake Composites

Fiber Composites

Polymer Matrix Composites

• What are the most common advanced composites?– Graphite/Epoxy– Kevlar/Epoxy– Boron/Epoxy

Polymer Matrix Composites

• What are the drawbacks of polymer matrix composites?– Low operating temperatures– High CTE and CMEs– Low elastic properties in certian

directions

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

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

materials

Property Units Graphite/Epoxy

Glass/ Epoxy

Steel Aluminum

Specific Gravity Young’s modulus Ultimate Tensile Strength Coefficient of Thermal Expansion

Msi Ksi in/in/F

1.6 26.25 217.6 0.01111

1.8 5.598 154.0 4.778

7.8 30.0 94.0 6.5

2.6 10.0 40.0 12.8

Comparative Stiffness of PMCs and Metals

How to make a PMC

Schematic of Prepreg Manufacturing

Prepreg Boron/Epoxy

Autoclave Lamination

Filament Winding

Filament Winding Video

Resin Transfe

r Molding

Common PMC Fibers & Matrices

• Fibers– Graphite– Glass– Kevlar

• Matrices– Epoxy– Phenolic– Polyester

Table 1.5 Typical mechanical properties of fibers used in polymer

matrix composites

Property Units Graphite Aramid Glass Steel Aluminum Specific Gravity Young’s modulus Ultimate Tensile Strength Axial Coefficient of Thermal Expansion

Msi Ksi in/in/F

18. 33.35 299.8 -0.722

1.4 17.98 200.0 -2.778

2.5 12.33 224.8 2.778

7.8 30 94 6.5

2.6 10 40 12.8

Cost Comparison of PMC fibers

Type of fiber Cost ($ per pound)

A-glass 0.65 - .90 C-glass 0.75 - 1.00 E-glass 0.75 - 1.00 S-2 Glass 6.00 - 8.00 Heavy Tow 9.00 - 12.00Medium Tow 15.00 -20.00 Low Tow 40.00 -70.00+ Kev29 12.00 -14.00 Kev149 25.00 -30.00

Manufacturing of Glass Fibers

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

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

glassProperty Units E-glass S-glass Specific Gravity Young’s modulus Ultimate Tensile Strength Coefficient of Thermal Expansion

Msi Ksi in/in/F

2.54 10.5 500 2.8

2.49 12.4 665 3.1

Table 1.7 Chemical Composition of E-Glass and S-

Glass Fibers % Weight Material E-glass S-glass Silicon Oxide Aluminum Oxide Calcium Oxide Magnesium Oxide Boron Oxide Others

54 15 17 4.5 8 1.5

64 25 0.01 10 0.01 .8

Fig 1.10 Forms of Fibers

Fig 1.11 Manufacturing Graphite Fibers

Resin Systems

• Polyester• Phenolics• Epoxy• Silicone• Polymide

Properties of epoxy

PROPERTY UNITS EPOXY

Specific gravity - 1.28

Young’s modulus Msi 0.55

UTS Ksi 12.0

Curing Stages of Epoxy

Comparison of Resins

Difference between thermosets and thermoplastics

THERMOPLASTICS THERMOSET

Soften on heating and pressure, and henceeasy to repair

Decompose on heating

High strains to failure Low strains to failure

Indefinite shelf life Definite shelf life

Can be reprocessed Cannot be reprocessed

Not tacky and easy to handle Tacky

Short cure cycles Long cure cycles

Higher fabrication temperature andviscosities have made it difficult to process

Lower fabricationtemperature

Excellent solvent resistance Fair solvent resistance

Pre-Preg Graphite/Epoxy