MTY-7-ENComposites

Examples of composites

•Composited in nature•wood

•bones

•Syntetic composites•Plywood•Paper •Metallic alloys•Reinforced concrete

Advantages and disadvantages of composites

• Advantages• High ratio between strength and stiffness to density

• High resistance against creep and fatigue

• High strength at high temperatures

• High toughness

• Resistivity to corrosion

• Anisotropy

• Disadvantages• Expensive materials

• Expensive manufacturing

• Hard to repair

• Material properties

• Anisotropy

• Complex testing of properties and inspection

Principle of composite

Two or more components are combined in such a way that the properties of the resulting material cannot be obtain from one homogeneous material

High-tech application of composites

Composites in sport and luxury goods

Phases of composites

• Matrix - continuous

• Reinforcement – discrete

Metals Ceramics

Polymers Glasses

Composites

Composite materials

Composites

particulate fibrous Structural

Large p. dispersion Long fiber Short fiber

oriented random

laminates sandwich

Voigt

Reuss

Composites:isostress a isostrain

b

b

a

a

Reuss

effE

V

E

V

E

1

bbaa

Voigt

eff EVEVE

Density bbaaC VV

Modulus (bounds)

Elastic moduli of long-fibre composites

Mechanical properties of long-fibre composite

Mechaniccal properties of composites

Lower

Upperbond

Strength of composites

fiber fiber

composite

compositematrix

matrix

Strength of fiber reinforced material

Anisotropy of unidirectional fiber-reinforced layer

Laminates - notation

Quasi isotropy

Symmetry

Lamina orientation

[0/45/-45/90]

Symmetry

[0/90/0]s = [0/90/0/0/90/0]

Layers repetition

[0/903/45] = [0/90/90/90/45]

Material indication

[0G/0C/90C/90K] – Glass, Carbon, Kevlar

Sandwich

Short-fiber composite

Short – fibred composites

Short fiber composites – fiber orientation

Relation of fiber strength to its diameter

Material Elasticity modulusE [GPa]

Strength in tensionRm [MPa]

Glass fiber type E 72 2 100 to 3 500

Glass E 72 100

Carbon fiber 190 to 850 2 000 to 7 000

Polycrystalline graphite 10 20

Ceramic fiber SiC 400 3 900

bulk SiC 410 500

Polyethylene fiber UHMW PE 80 to 120 3 000

Comparison of bulk and fiber strength of selected materials

Fiber materialsPolymeric material density

ϱ (g.cm-3

)R(MPa) E(GPa) Elongation A

(%)Syntethic wood 1,0 900 72,00 ---celullose (Fortisan) 1,52 1 100 2,4 ---polyester (Terylen) 1,38 600 1,2 ---polyamide (Nylon) 1,14 800 2,9 ---aramide (Kevlar 29) 1,44 3 450 58,6 4,0aramide (Kevlar 49) 1,44 3 620 124,0 2,5aramide (Kevlar 149) 1,45 2 410 146,0 1,5aramide (Twaron) 1,44 3 000 67,0 3,3aramide (Twaron HM) 1,45 3 000 125,0 2,3

Ceramic Material

Densityϱ (g.cm

-3)

Rm

(MPa)E

(GPa)Fiber

diameter(µm)

Thermal stability

(°C)Al2O3 3,15 to 4,0 2 070 to 2 800 172 to 470 25 800ZrO3 4,84 2 000 344 60 1 000

carbon 1,6 to 2,0 1 700 to 3 400 220 to 690 58 to 76 --BN 1,90 1 380 to 2 400 90 to 315 66 to 70 2 500

B4C 2,3 to 2,5 2 070 to 2 420 276 to 480 100 2 500

Carbon fibres

Property Hi-modulusgraphite

Hi-strengthgraphite

steel(pcomparison)

density ϱ [g.cm-3] 1,90 1,90 7,8

Young modulus of elasticity E [GPa] 390 240 210

Strength Rm [GPa] 2,1 2,5 0,34 to 2,1

Effective modulus E/ϱ [MPa.g-1.cm3] 205 126 26,9

Effective strength Rm/ϱ [MPa.g-1.cm3] 1,1 1,3 0,043 to 0,27

Carbon fiber property at room temperature

Materials of fibres

Matrix Materials

•Polymeric• Thermosets (Epoxides)• Thermoplastic matrix (Polyetheretherketone (PEEK),

Polyfenylensulfide (PPS))

•Metallic• Copper• Sintered carbides• Cermets

•Ceramic• SiC whiskers / Al2O3 matrix• SiC whiskers / Si3N4 matrix• SiC / SiC matrix• Fiber / glass matrix• Carbon / carbon composites

Synergic effect

•Rule of mixtures: PRoM = P1f1 + P2f2 (f1 + f2 = 1)

•Synergy Pobserved >>> PRoM

•Fracture toughness: •glass U~ 1 J/m2, •polyester U~ 100-1000 J/m2

•Rule of mixtures U~ 1 – 1000 J/m2 but... •Observed U~ 104 - 105 J/m2 !!

•WHY???

Interface - wetting

Interaction between fracture and composite

-Plastic deformation of matrix in vicinity of crack-Crack changes direction in contact with fiber (not perpendicular to force)-Energy to separate fiber from matrix-Pull/out of fibers from matrix - friction

Fracture toughness of composites

Comparison of composites and other classes of materials

Testing of composite materials

• Elastic properties (4 independent values)• Modulus of elasticity in direction of fibers

• Modulus of elasticity in perpendicular direction to fibers

• Shear modulus

• Poisson ratio

• Strength properties (5 independent values)• In direction of fibers – tension and compression

• In direction perpendicular to fibers – tension and compression

• Shear strength

Manufacturing of composites

prepregs

Manufacturing of composites

autoclave

Manufacturing and joining of composites

lepení

Thank you for your attention!