Particles

Whiskers / Short Fibers: L/d ~ 10² - 10⁴

Continuous Fibers: L/d > 10⁴

Round of Ellipsoid

Odd Shaped

Platelets

Most common uses are non-structural: Thermal or Electrical Conductivity, Wear Resistance

SiC/SiC

SiC/Si₃N₄

{High Temp Applications}

Al₂O₃ / Aluminum

SiC / Aluminum

Graphite / Iron

Gives Highest Strength and Stiffness

L/D > 10⁴

More than one kind of filler or reinforcement in a common matrix.

Ex. Glass/Carbon

Carbon Fibers / Carbon Black

Aluminum Layer

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Glass Layer

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Aluminum Layer

Glass

Pros: Low Cost, High Strength

E-Glass (1$/lb): Electrical Grade

S2-Glass (6$/lb): Military Grade - Extra Strength n' Thickne

Cons:

Low Stiffness (10 MSI)

Low Fatigue and sustained load knockdown (~3)

Other:

Quartz - Expensive, low di-electric constant

C-Glass - Corrosian Resistant, Acidic Enviornments

A or R Glass - Corrosive Resistant (Alkaline) {Concrete}

Basalt - Costs & Properties between E and S2

Mass Density:

density ~ 2.5 g/cc

E= 70-85 GPa

Ultimate Strength: Eult = 5-6%

Carbon - Early 1960's

Pros:

• High Strength,
•  High Stiffness,
•  Low Density,
•  Chemical Resistance,
•  High temp strength,
• low fatigue knockdown (.7)

Cons:

• Oxydation > 400 C
• Expensive

Carbon:

Pan: Poly acrylonitrite

High Strength

AS4

T1000

Pitch: High Modulus

P120

Little known facts:

• Less stiff than glass in transverse direction
• Same story on strength - does not bond to matrices as well
• less susceptible to moisture-induced fiber/matrix bond degregation

Aramid Fibers ~ 1970's

Density 1.4 g/cc (lowest)

Pros: High Tensile Strength

Cons: Poor compression stength/stiffness

<200C in use

High moisture absorbtion

UV Radiation damage

Dupont Kevlar:

E_T = 12-27 MSI

S_T = 490 - 580 KSI

Eta_T = 2-4%

Note: Good for ballistic applications

Ceramic Fibers

Silicon Carbide (SiC) {E = 58Msi, 100$/lb, T_max=1200C}

Alumina (Al₂O₃) {E = 55 Msi, T_max=1300C}

Pro: High Modulus, High Temp Capability

Cons: High Cost, Low ultimate eta

Matrix Materials: PMC's - Epoxy

Pros:

• High Strength + Adhesion
• High Stiffness > E= 2-5 GPa
• Strain_MAX ~5%
• Highly Tailored Cure Temp and Viscosity
• No volatiles emitted as part of cure

Cons:

High Cost, 3-10 $/lb

Long Cure Time

Matrix Materials: PMC's - Polyester, Vinylester

Marine and Civil - E= 3.4 GPa

Pros:

• Lower Cost <1$/lb
• Low Viscosity (
• Fast Cure (min. 1 minute)

Cons:

• Not as strong as epoxy
• High Shrinkage

Matrix Materials: PMC's - Thermoplastics E=2-5 GPa

Pros:

• High Toughness
• Infinite Shelf Life

Cons:

• Poor solvent resistance
• High processing temps ~800F
• High viscosity

Peek - Poly Ether Ether Keytone  \ Semi-

PPS - Poly Phenylene Sulfide         \        -Cryst

Matrix Materials: MMC's

Good for thermal Applications

Copper

Aluminum - 250C

Magnesium - 600C

Titanium - 600-800C

Pressure + Heat

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Pressure + Heat

Matrix Materials: CCC

Carbon-Carbon Composites

Rocket Nozzles and Race Car disc brakes

 up to 2800 C (inert)

This is the one where you keep repeating the process of applying phenolil and carbonizing it.

Micromechanics

• Method of homogonizing the properties of a heterogenous material
• Analysis of constituents to give 'effective' properties of a composite