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ME 5720Mechanics of Composite Materials

Dr. Ronald Gibson

Composite Material

• Two or more materials combined in a structural unit having properties which could not be achieved by any of the constituent materials acting alone.

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Specific Learning Objectives

After completing this course, students will be able to:• Develop a strong understanding of the role of constituents in overall

response of composite lamina• Develop a strong understanding of how a set of laminae with different

orientations affects the overall laminate properties and response• Apply these concepts to analyze and design fiber-reinforced composites

for engineering applications• Analyze stresses and strains in anisotropic and orthotropic materials

having both continuous and discontinuous reinforcement• Model hygrothermal effects on properties and response of composite

materials• Predict composite properties based on micromechanical theories• Use Classical Lamination Theory to assess the role of individual plies on

overall axial, bending and twisting deformation of laminates under applied loads

• Use failure theories for multiaxial loading to determine if the composite will fail for known loading and use this knowledge to design failure resistant structures

MicromechanicsMacromechanics

FibersLamina

Matrix

Laminate

Structure

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• Natural compositesWoodbone

• Man-made compositesMetallic alloysPlywoodReinforced concreteFiber-reinforced composites

polymer matrixmetal matrixceramic matrix

Types of Composites

Historical importance of different materials (From Ashby, 1987)

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Griffith’s measurements of tensile strength of glass fibers (From Gordon, 1976)

Surface area-to-volume ratio for cylindrical particles vs. particle aspect ratio(From McCrum, et al., 1988

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Lamina TypesContinuous Fiber

Hybrids

Woven

Chopped Fiber

Composite Sandwich Structure

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Constituent Materials in Composites

1. Reinforcing Fibers2. Matrix or binders3. Fillers

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Fibers for Reinforcement

• Glass ( E-Glass, S-Glass )• Graphite ( carbon )• Aramid ( Kevlar ™)• Boron• Basalt• Other metals ( steel, tungsten )• Whiskers• Oriented polyethylene ( Spectra™ )• Carbon nanotubes

Table 1.1. Selected properties of bulk and fibrous materials

Material Tensile Strength Tensile Modulus Density Specific Strength Specific Modulus Ultimate Strain ManuMPa GPa g/cm3 MPa/(g/cm3) GPa/(g/cm3)

Bulk metals6061T6 Aluminum 310 69 2.71 114.4 25.5 0.174340 Steel 1030 200 7.83 131.5 25.5 0.19AZ80 Magnesium 345 45 1.8 191.7 25 0.06

Bulk polymers Nylon 6/6 75 2.8 1.14 65.8 2.5 0.5Polycarbonate 65 2.4 1.2 54.2 2 1.1Polyvinylchloride 40 3.1 1.44 27.8 2.2 0.4

Bulk ceramics Silicon carbide 0.4 400 3.4 0.1 117.6 0.001Aluminum oxide 0.5 380 3.8 0.1 100 0.001

Glass fibers E-glass 3448 72 2.54 1357.5 28.3 0.04 Owens-CorS-2 glass 4830 87 2.49 1939.8 34.9 0.057 Owens-Cor

PAN-based carbon fibers AS4 4278 228 1.79 2389.9 127.4 0.0187 HexcelIM7 5175 276 1.78 2907.3 155.1 0.0178 HexcelIM9 6072 290 1.8 3373.3 161.1 0.018 HexcelT-300 3750 231 1.76 2130.7 131.3 0.014 CytecT-650/35 4280 255 1.77 2418.1 144.1 0.017 CytecT-800S 5880 294 1.8 3266.7 163.3 TorayT-1000G 6370 294 1.8 3538.9 163.3 Toray

Pitch-based carbon fibers P-55S 1900 379 1.9 1000 199.5 0.005 CytecP-100S 2410 758 2.16 1115.7 350.9 0.003 CytecP-120S 2410 827 2.17 1110.6 381.1 0.003 Cytec

Polymeric fibers Kevlar 29 aramid 3620 83 1.44 2513.9 57.6 0.044 DuPontKevlar 49 aramid 3792 131 1.44 2633.3 91 0.023 DuPontSpectra 900/650 polyethylene 2400 66 0.97 2474.2 68 0.041 HoneywellSpectra 2000/100 polyethylene 3340 124 0.97 3443.3 127.8 0.03 HoneywellTechnora aramid 3430 73 1.39 2467.6 52.5 0.046 TeijinZylon-AS PBO 5800 180 1.54 3766.2 116.9 0.035 Toyobo

Other fibers Boron 4.0 mil dia 3516 400 2.57 1368.1 155.6 0.008 Specialty MSCS-6 silicon carbide 3450 380 3 1150 126.7 0.0013 Specialty M

Carbon nanotubes 30000 1000 1.9 15789.5 526.3

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Specific modulus vs. specific strength for bulk materials and fibers

Kevlar 49 fiberSpectra 900 fiber

Zylon-ASfiber

AS-4 fiber

IM-9 fiberIM-7 fiberT-650/35 fiber

S-2 glass fiberE-glass fiber

bulk Nylon bulk Aluminum

bulk Silicon Carbide

Boron fiber

P-100S fiber

P-55S fiber

SCS-6 fiber

P-120S fiber

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50

100

150

200

250

300

350

400

450

0 500 1000 1500 2000 2500 3000 3500 4000

Specific Strength, MPA/(g/cc)

Spe

cific

Mod

ulus

, GP

a/(g

/cc)

From M. Shuart, NASA, 2001

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Carbon structures, including nanotube(From Smalley web site, 2002)

Disadvantages of Fibers Alone

1. Cannot support longitudinal compressive loads

2. Transverse properties are not as good as longitudinal properties

Thus, a binder or matrix material and transverse reinforcement are needed for structural use of fibers.

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Matrix - for binding and protecting fibers

PolymersThermoplastics

Thermosets

MetalsMagnesium

Aluminum

Ceramics

Increasing Operating

temperature

Thermosetting Polymer Matrix Materials

• Epoxies *• Phenolics• Polyesters

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Advanced Thermoplastic Matrix Materials

• Polyether ether ketone ( PEEK ) • Polyphenylene sulphide ( PPS )• Polysulphone ( PS )• Polyether sulfone ( PES )• Polyimide ( PI )• Polyetherimide ( PEI )

Advantages of Advanced Thermoplastics Compared with

Thermosets• Improved ductility and toughness • Better “hot/wet” properties• Non-flammable, lower toxic fume emission• Potential for lower fabrication cost• Faster production rates

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Fillers• Calcium carbonate, clay, mica - for cost

reduction• Glass or graphite micro spheres – for weight

reduction• Alumina trihydrate – for flame and smoke

suppression• Carbon black – for ultraviolet and thermal

protection