Composite Materials Engineering 45 Bruce Mayer, PE

Engineering 45

Composite

Materials

Bruce Mayer, PE

Registered Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Engineering-45: Materials of Engineering

1

Bruce Mayer, PE

BMayer@ChabotCollege.edu • ENGR-45_Lec-28_Composites.ppt

Learning Goals – Composites

 List The CLASSES and TYPES of Composites

 When to Use Composites Instead of

Metals, Ceramics, or Polymers

 How to Estimate Composite

Stiffness & Strength

 Examine some Typical Applications


2

Bruce Mayer, PE


Terms & Classifications

 Composite



MultiPhase

Material with Significant

Proportions of Each Phase

• Phase Components

– MATRIX

– DISPERSED Phase

 Matrix

• The CONTINUOUS Phase

• The Matrix Function

3

– transfer stress to other phase(s)

– Protect other phase(s) from the (corrosive) Environment


Reprinted with permission from

D. Hull and T.W. Clyne, An

Introduction to Composite

Materials, 2nd ed., Cambridge

University Press, New York, 1996,

Fig. 3.6, p. 47.

Bruce Mayer, PE


Terms & Classifications cont.1

 Composite Classifications

• M MC



Metal Matrix Composite

• C MC



Ceramic Matrix Comp.

• P MC



Polymer Matrix Comp.

 Dispersed Phase (DP)

• Function = To Enhance the

Matrix Properities

– MMC : increase σ y

, TS/ σ u

, creep resistance

– CMC : increase K c

(fracture toughness)

– PMC: increase E, σ y

, TS/ σ u

, creep resistance

• Classes: Particle, fiber, structural


4

Bruce Mayer, PE


Composite Taxonomy

PARTICLE Reinforced

LARGE

Particle

DISPERSION

Strengthened

Composites

Continous

(Aligned)

FIBER Reinforced

DIScontinous

(Short)

STRUCTURAL

Laminates

Sandwich

Panels

Aligned

Randomly Oriented


5

Bruce Mayer, PE


Composite Survey – Particle-I

Particle-reinforced Fiber-reinforced

 Examples

-Spheroidite steel matrix: ferrite ( a )

(ductile)

Structural particles: cementite

(Fe3C)

(brittle)

Adapted from Fig.

10.10, Callister 7e.

(Fig. 10.10 is copyright United

States Steel

Corporation, 1971.)

60 m m

-WC/Co cemented carbide matrix: cobalt

(ductile)

Vm:

10-15vol%!

-Automobile tires matrix: rubber

(compliant)


6

600 m m particles:

WC

(brittle, hard)



(Fig. 16.4 is courtesy Carboloy

Systems,

Department,

General Electric

Company.) particles:

C

(stiffer)



(Fig. 16.5 is courtesy Goodyear

Tire and Rubber

0.75

m m


ReInforced ConCrete

 Concrete is a

PARTICLE

ReInforced

Composite

• Matrix = PortLand

Cement

– 3CaO-SiO

2

2CaO-SiO

2

+

• Dispersed Phases

– Sand+Gravel

Aggregate

– 60%-80% by Vol


7

 Steel ReInforcing

Bars (Rebar)

• A type of FIBER

Reinforcement

• Improves Tensile &

Shear Strength

Bruce Mayer, PE


More ReInforced Concrete

 Concrete ≡ gravel + SAND + cement

• Why sand and gravel? → Sand packs into gravel VOIDS

 Reinforced concrete - Reinforce with steel reBAR or reMESH

• Increases TENSILE strength - even if Concrete matrix is cracked

 PreStressed concrete - reMesh under tension during setting of concrete. Tension release puts concrete under COMPRESSIVE Stress

• Concrete is much stronger under compression.


8

Bruce Mayer, PE


Composite Survey – Particle-II

Particle-reinforced Fiber-reinforced Structural

 Composite Material Elastic Modulus, E c

• Two “Rule of Mixtures” Approximations upper limit:

E c

=

V E

+

V

“rule of mixtures” p

E p ←Springs in PARALLEL

Data:

E(GPa)

350

Cu matrix w/tungsten particles

300

250

200

150 lower limit:

1

E c

=

V m

E m

+

V p

E p

0 20 40 60 80 100

(Cu) (W) vol% tungsten

 Rule-of-Mixtures Applies to Other Properties

• Electrical conductivity, σ elect

: Replace E by σ elect

• Thermal conductivity, k: Replace E by k.


9

Bruce Mayer, PE


Composite Survey: Fiber-I

 Fibers very strong

• Provide significant strength improvement compared to pure matrix-material

 Example: fiber-glass

• Continuous glass filaments in a polymer matrix

• Strength due to fibers

• Polymer simply holds them in place


10

Bruce Mayer, PE


Fiber Materials

 Whiskers - Thin single crystals large length to diameter ratio

• graphite, SiN, SiC

• high crystal perfection – extremely strong, strongest known

• very expensive

 Traditional Fibers

 polycrystalline or amorphous

 Generally polymers or ceramics

 Ex: Al

2

O

3

, Aramid,

E-glass, Boron,

UHMWPE


11

Bruce Mayer, PE


Composite Survey: Fiber-II

Particle-reinforced Fiber-reinforced

 Fiber Materials

• Whiskers - Thin single crystals with large length to diameter ratio

– graphite, SiN, SiC

– high crystal perfection – extremely strong, strongest physical form known

– very expensive to produce

– Fibers

• polycrystalline or amorphous

• generally polymers or ceramics

• Ex: Al

2

O

3

– Wires

, Aramid, E-glass, Boron, UHMWPE

• Metal – steel, Mo, W

Structural


12

Bruce Mayer, PE


Fiber Alignment

Adapted from Fig.

16.8, Callister 7e .

13 aligned continuous

Engineering-45: Materials of Engineering aligned random discontinuous

Bruce Mayer, PE


ISOstress & ISOstrain

 isoSTRAIN →

Tensile strength and elastic modulus when fibers are parallel to the direction of stress

 isoSTRESS →

Tensile strength and elastic modulus when fibers are perpendicular to the direction of stress


14

Bruce Mayer, PE


Composite Survey – Fiber-I


 ALIGNED, CONTINUOUS Fibers

• Examples

Metal: g ’ (Ni

3

Al)a (Mo) by eutectic solidification.

matrix: a (Mo) (ductile)

Glass w/SiC fibers formed by glass slurry

E glass = 76GPa; E SiC = 400GPa.

15

(a)

2 m m fibers: g ’ (Ni3Al) (brittle)

From W. Funk and E. Blank, “Creep deformation of Ni

3

Al-Mo in-situ composites", Metall. Trans. A Vol. 19(4), pp. 987-998, 1988. Used with

(b)

From F.L. Matthews and R.L.

Rawlings, Composite Materials;

Engineering and Science, Reprint ed., CRC Press, Boca Raton, FL,

2000. (a) Fig. 4.22, p. 145 (photo by J. Davies); (b) Fig. 11.20, p.

349 (micrograph by H.S. Kim, P.S.

Rodgers, and R.D. Rawlings).

Used with permission of CRC

Press, Boca Raton, FL.

Bruce Mayer, PE


Composite Survey – Fiber-II


 DISCONTINUOUS, RANDOM, 2D (Planer) Fibers

 Example: Carbon-Carbon

• Process: fiber/pitch, then burn out at up to 2500C.

• Uses: disk brakes, gas turbine exhaust flaps, rocket nose cones.

(b) view onto plane

C fibers: very stiff very strong

C matrix: less stiff less strong fibers lie in plane

(a)

 Other variations:

• Discontinuous, random 3D

• Discontinuous, 1D

– Fully Aligned


16

Adapted from F.L. Matthews and R.L.

Rawlings, Composite Materials; Engineering and Science, Reprint ed., CRC Press, Boca

Raton, FL, 2000. (a) Fig. 4.24(a), p. 151; (b)

Fig. 4.24(b) p. 151. (Courtesy I.J. Davies)

Reproduced with permission of CRC Press,

Boca Raton, FL.

Bruce Mayer, PE


Composite Survey – Fiber-III

Particle-reinforced Fiber-reinforced

 CRITICAL fiber length for effective stiffening & strengthening:

Structural fiber strength in tension fiber length



15



 f c d fiber diameter shear strength of fiber-matrix interface

 The Equation Balances (want PullOut ≥ Tear)

• The Fiber Load capacity → σ f

•[A

CylXsec

] = σ f

•[πd 2 /4]

• The Fiber Pull-Out Force→  c

•[A

CylSurf

] =

 c

•[πd•l]

 Stronger Fibers → need LONGER fiber

 Stronger Fiber-Matrix ShearBond → need SHORTER Fiber


17

Bruce Mayer, PE


Fiber Lengths cont.

 Example: FiberGlass

• Need Fiber Lengh > 15mm

 Reason for length Criteria → examine Extreme cases

• Very Short Fiber has very little hold-in force and would PULL-OUT (Fiber PULLS OUT before Fracture)

• Very Long Fiber would take almost all the axial load

(Fiber FRACTURES before PullOut)

Shorter, thicker fiber: fiber length



15

 f c d fiber length



15



 f c d



Poorer fiber efficiency


18

Better fiber efficiency

Bruce Mayer, PE


Composite Survey – Fiber-IV


 Estimate E c and TS

• Valid for LONG Fiber

Condition: fiber length



15



 f c d

 The Elastic Modulus in

Fiber Direction

E c

=

E m

V m

+

KE efficiency factor f

V f

 Typical Values for K:

• Aligned 1D: K = 1 (anisotropic)

• Random 2D: K = 3/8

2D isotropy)

• Random 3D: K = 1/5

(3D isotropy)

 TS in fiber direction

(1D, Aligned) by VOLUME

Weighted Average

(TS) c

=

(TS) m

V m

+

(TS) f

V f


19

Bruce Mayer, PE


Composite Survey – Structural


 Stacked and bonded fiber-reinforced sheets

• Orthogonal stacking sequence: e.g., 0°/90°

• benefit: balanced, in-plane stiffness

 Sandwich panels

• low density, honeycomb core

• benefit: small weight, large bending stiffness face sheet adhesive layer honeycomb

Similar to Composite Beam

Lab Exercise


20

Bruce Mayer, PE


Composite Benefits

 Ceramic Matrix

Composites →

Better FRACTURE

TOUGHNESS

 Metal Matrix

Composites →

Improved CREEP

RESISTANCE

Force particle-reinf fiber-reinf un-reinf

Bend displacement


21

Bruce Mayer, PE


Composite Benefits cont.1

 Polymer Matrix Composites →

Better E: ρ (Stiffness:Weight) ratio

103

102

10

PMCs

1 ceramics metal/ metal alloys

.1

.01

G=3E8

K=E polymers

.1 .3 1 3 10 30

Density, r [Mg/m 3]


22

Bruce Mayer, PE


Specific Strength

 The PRIMARY

Motivation for the

Use of Composites

→ Hi-Strength,

Hi-Stiffness &

Lo-Weight

 Thus Two Important

Metrics

• Specific STRENGTH

S



=

Strength

Specific



Weight


23

S

E

• Similarly The

Specific STIFFNESS

=

Elastic

Specific

Modulus



Weight

 Now Specific Weight g = r  g in N/m

3

• Where

– ρ 

Density in kg/m 3

– g 

Acceleration of

Gravity (9.81 m/s 2 )

Bruce Mayer, PE


Specific Strength cont.1

 Now Determine

Units for S

σ and S

E by Way of Examples

• For 7075 Al in the

Heat treated State

–  u

= 83 ksi

– g

= 0.101 lb/in 3

S



=

83000 lb

0 .

101 lb in

2 in

3

S



=

8 .

218



10

5 in


24

• For Kevlar-49

(Aramid Fiber)

– E = 131 GPa

– ρ = 1444 kg/m 3

• Find g g = r g

=

1444 kg m

3



9 .

81 m s

2

=

14166

N m

3

S

 Now Specific Stiffness

E

=

131



10

9

N

1 4166 N m m

3

2

S

E

=

9 .

248



10

6 m

Bruce Mayer, PE



25

Bruce Mayer, PE


S

σ

vs S

E

Comparison

26

 The High DENSITY of Metal Reduces S

σ and S

 The Low STRENGTH & STIFFNESS of most

E

Polymers Reduces S

σ

Engineering-45: Materials of Engineering and S

E

Bruce Mayer, PE


Summary – Composite Matls

 Composites Classified by:

• The Matrix Material

– Ceramic (CMC)

– Metal (MMC)

– PolyMer (PMC)

• ReInforcement Geometry

– Particles

– Fibers

– Layers


27

Bruce Mayer, PE


Summary – Composites cont.1

 Composites enhance matrix properties:

• MMC: enhance  y

, TS, creep performance

• CMC: enhance K c

• PMC: enhance E,  y

, TS, creep resistance

 Particle ReInforced

• Elastic modulus can be estimated by the

Rule of Mixtures

• Properties are isotropic


28

Bruce Mayer, PE


Summary – Composites cont.2

 Fiber ReInforced:

• Elastic modulus and TS can be estimated along fiber direction By Rule of Mixtures

• Properties can be isotropic or anisotropic

 Structural:

• Based on build-up of sandwiches in layered form

– Plys

– HoneyCombs


29

Bruce Mayer, PE


WhiteBoard Work

 Prob 16.11

• Given IsoStrain,

Longitudinal Loading for a Continuous

F

Fiber Composite: c

=

F m

+

F f

• Then Show

• Where

– F 

Force

– E 

Elastic Modulus

– V 

Volume fraction

– Sub-f → “fiber”

– Sub-m → “matrix”

– Sub-c → “composite”

30

F

F m f =

E

E

Engineering-45: Materials of Engineering f

V m

V m f

Bruce Mayer, PE


Chabot Engineering

Appendix

E-glass

Bruce Mayer, PE

Licensed Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Bruce Mayer, PE



31

E Glass - BackGround

 http://www.azom.com/details.asp?Articl

eID=764

 Background

• E-Glass or electrical grade glass was originally developed for stand off insulators for electrical wiring. It was later found to have excellent fibre forming capabilities and is now used almost exclusively as the reinforcing phase in the material commonly known as fibreglass.


32

Bruce Mayer, PE


E Glass - Composition

 Composition

• E-Glass is a low alkali glass with a typical nominal composition of SiO

2

14wt%, CaO+MgO 22wt%, B

54wt%, Al

2

O

3

2

O

3

10wt% and Na

2

O+K

2

O less then 2wt%. Some other materials may also be present at impurity levels.


33

Bruce Mayer, PE


E Glass – Key Properties

 Properties that have made E-glass so popular in fibreglass and other glass fibre reinforced composite include:

• Low cost

• High production rates

• High strength, (see table on next slide)

• High stiffness

• Relatively low density

• Non-flammable

• Resistant to heat

• Good chemical resistance

• Relatively insensitive to moisture

• Able to maintain strength properties over a wide range of conditions

• Good electrical insulation


34

Bruce Mayer, PE


E Glass – Fibre Strength

 Table 1. Comparison of typical properties for some common fibres.

Materials

E-Glass

S-Glass

Alumina (Saffil)

Carbon

Kevlar 29

Kevlar 49

Density (g/cm 3 )

2.55

2.49

3.28

2.00

1.44

1.44

Tensile Strength

(MPa)

2000

4750

1950

2900

2860

3750

Young modulus

(GPa)

80

89

297

525

64

136


35

Bruce Mayer, PE


E Glass – Use in Composites

 The use of E-Glass as the reinforcement material in polymer matrix composites is extremely common.

Optimal strength properties are gained when straight, continuous fibres are aligned parallel in a single direction. To promote strength in other directions, laminate structures can be constructed, with continuous fibres aligned in other directions. Such structures are used in storage tanks and the like.

 Random direction matts and woven fabrics are also commonly used for the production of composite panels, surfboards and other similar devices.


36

Bruce Mayer, PE


Composite Materials Engineering 45 Bruce Mayer, PE

Engineering 45

Composite

Materials

Learning Goals – Composites

Terms & Classifications

Terms & Classifications cont.1

Composite Taxonomy

Composite Survey – Particle-I

ReInforced ConCrete

More ReInforced Concrete

Composite Survey – Particle-II

Composite Survey: Fiber-I

Fiber Materials

Composite Survey: Fiber-II

Fiber Alignment

ISOstress & ISOstrain

Composite Survey – Fiber-I

Composite Survey – Fiber-II

Composite Survey – Fiber-III

Fiber Lengths cont.

Composite Survey – Fiber-IV

Composite Survey – Structural

Composite Benefits

Composite Benefits cont.1

Specific Strength

Specific Strength cont.1

S

vs S

Comparison

Summary – Composite Matls

Summary – Composites cont.1

Summary – Composites cont.2

WhiteBoard Work

Chabot Engineering

Appendix

E-glass

E Glass - BackGround

E Glass - Composition

E Glass – Key Properties

E Glass – Fibre Strength

E Glass – Use in Composites

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