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!