© gnu su-jin kim composite material science composite( 복합재 ) associate professor su-jin...

© GNU Su-Jin Kim© GNU Su-Jin Kim

CompositeCompositeMaterial ScienceMaterial Science

Composite(Composite( 복합재복합재 ))

Associate Professor Su-Jin Kim

School of Mechanical EngineeringGyeongsang National University

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Composit( 복합재 )

1. Fiber Reinforced Polymer (FRP) ( 섬유강화 )

2. Particle Reinforced ( 입자강화 )

3. Structure ( 구조강화 )

Particle-reinforced Fiber Reinforced Structural

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• Stacked and bonded fiber-reinforced sheets

- stacking sequence: e.g., 0º/90º

- benefit: balanced, in-plane stiffness

Structural Composite

• Sandwich panels

- low density, honeycomb core - benefit: small weight, large bending stiffness

honeycombadhesive layer

face sheet

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Particle Reinforced Composites I

SpheroiditeSteel

기지 : 페페페페

(ductile)

입자 :시맨타이트 (Fe3C)

(brittle)60 m

WC/Co 초경공구

기지 : 코발트 (ductile)

입자 : 텅스텐 (brittle, hard)Vm:

10-15 vol%! 600 m

자동차타이어Carbon black

기지 : 고무 (compliant)

입자 : 탄소 (stiffer)

0.75 m

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Concrete : 자갈 + 모래 + 시맨트

Reinforced( 강화 ) Concrete : 철근을 넣고 콘크리트를 부어 인장 응력에 견딜 수 있는 능력을 향상

Prestress Concrete : 철근에 인장 응력을 가한 상태로 콘크리트를 부어 경화시킨 다음 인장 응력을 제거 .

Particle Reinforced Composites II

Post tensioning : Place the tendons and nail anchors to the formwork, cast the concrete slab, remove the formwork, stress and anchor the tendons, then cut and grout the tendons with non-shrink grout.

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• Elastic modulus, Ec, of composites:

- two approaches.

• Other Characteristics:

- Electric resistance, R: Replace E in equations with R. - Thermal conductivity, k: Replace E in equations with k.

lower limit:1

Ec= VmEm

+VpEp

c m m

upper limit:E = V E +VpEp

“rule of mixtures”

Data: Cu matrix w/tungsten particles

0 20 40 60 80 100

150

200

250

300

350

vol% tungsten

E(GPa)

(Cu) (W)

Particle Reinforced Composites III

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Fiber Reinforced Polymer (FRP)

FRP ( 복합재료 ) Fiber( 섬유 ) + Plastic matrix ( 모재 ) Fiber: Kevlar, Glass fiber, Graphite fiber, Boron Plastic matrix: Epoxy, Polyester

Process1. Impregnation: fiber+resin2. Molding3. Cure by heat & pressure

http://vimeo.com/13769356

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Fiber Reinforced Polymer, FRP

• Composites are made from two (fiber + plastic matrix) or more materials with significantly different properties and which remain separate on a macroscopic level.

• Reinforcements (fiber) improve strength, stiffness of plastic matrix.

http://www.youtube.com/watch?v=qEU9N7UNBWk&p=9B6D9EAE75875D9D

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Composite Usage

• Bow wings, tennis rackets, racing bicycles and skis are made of [Glass, Carbon fiber] + [Epoxy matrix] composit.

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Fiber materials

• Fibers are strong, stiff, have a high specific strength and specific modulus.

• But they are brittle, abrasive and lack toughness• Ex) Kevlar, Glass fiber, Graphite fiber, Boron.

stiffness/density

stre

ngth

/den

sity

•Steel, Aluminum

•Glass fiber

•Kevilar

•Graphite

•Boron

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Kevlar (Polymer fiber)

• Kevlar is a light, strong para-aramid synthetic fiber. • Kevlar has many applications such as racing tires,

because of its high tensile strength-to-weight ratio; 5 times stronger than steel on an equal weight basis.

Kevlar(yellow)+Graphite(black) Bulletproof helmet & vest

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Glass fibers ( 유리섬유 )

• Glass fiber is chipper than others.• Called Glass-fiber reinforced polymer (GFRP).

Glass fiber Fishing bloat

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Graphite fibers ( 탄소섬유 )

• Graphite fibres are more expensive; low density, high strength, and high stiffness.

• Called carbon-fiber reinforced polymer(CFRP).

Boing787

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Boron fibers

• High strength and stiffness in tension, compression and resistant to high temperatures.

• High density• Expensive

made with carbon and boron fibre

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Plastic matrix

Matrix (Resin) in reinforced plastics has 3 functions:1. Transfer the stress to the fibres2. Protect fibres against physical damage.3. Reduce propagation of cracks in the composite.

• Epoxy(80%), Polyester (cheap).

Carbon fiber + Epoxy

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Metal matrix• The advantage is it has higher resistance to elevated

temperatures and higher ductility and toughness.• Limitations are that it has higher density and makes

processing more difficult.

Fiber Matrix Application

Graphite Aluminum Helicopter, Tennis racket

Magnesium Satellite

Boron Aluminum Compressor blade

Titanium Jet-engine fan blade

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Properties of Fiber reinforced plastics

• Type and length of the fibres.• Volume fraction of the reinforcement.

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Properties of Fiber reinforced plastics

• The highest stiffness and strength is obtained when fibres are aligned in the direction of tension force.