chapter9 - CHAPTER 9 COMPOSITE MATERIALS: STRUCTURE,...

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Unformatted text preview: CHAPTER 9 COMPOSITE MATERIALS: STRUCTURE, GENERAL PROPERTIES, AND APPLICATIONS 9-1 Definition of composite materials A combination of two or more chemically distinct and insoluble phases Properties and structural performance superior to those of the constituents Methods of reinforcement Historical example: straw with clay (:4000 BC) Figure 9.1 92 Aft flaps - Outboard (graphite) Flap support fairings 0 Inboard (graphite/ I Fwd segment (graphite/Kevlar fiberglass) + non-woven Kevlar mat) J Rudder o Aft segment (graphite/fiberglass) TIP fairings (graphite) Ailerons (graphite) \ .l‘ (fiber glass) / Fixed trailing edge \ l i" l\ ‘ panels (graphitelKevlar Engine strut fairings (Kevlar! fiberglass) Environmental control system ducts (Kevlar) + non-woven Kevlar ma Elevators (graphite) Auxiliary \ power inlet Fixed trailing edge panels Nose landing (graphite) upper (graphite/fiberglass) gear dqors . lower (graphite/Kevlar (graphlte) ‘ ( Sp'oflers + non-woven Kevlar mat) Wing-to-body fairings (graphite) fixed {13111113 edge P311515 (graphite/Kevlar I Cowl (graphite/Kevlar + non-woven fiberglass) components KEVIN mat) and (graphite/Kevlar (graphite) Wing leading edge lower panels + non-woven Kevlar mat) / (KCVlar/ fiberglass) / - Body main landing gear doors (graphite) 0 Trunnion fairings and wing landing gear doors (graphitelKevlar) 0 Brakes (structural carbon) FIGURE 9.1 Application of advanced composite materials in Boeing 757-200 commercial aircraft. Source: Boeing Commercial -\irpiane Company. 9-3 r4 PTABLE 9.1 Types and General Characteristics of Composite Materials V‘Iaterial Fibers Glass l Graphite Boron Aramids (Kevlar) , Other fibers Matrix materials '-‘ Thermosets Thermoplastics Metals Ceramics Characteristics -___________________._____———————-———’— High strength. low stiffness. high density; lowest cost: E (calcium aluminoborosilicate) and S (magnesia-aluminosilicatei types commonly used. Available as high-modulus or high-strength: low cost: less dense than glass. High strength and stiffness; highest density; highest cost; has tungsten filament at its center. Highest strength—to-weight ratio of all fibers; high cost. Nylon. silicon carbide. silicon nitride. aluminum oxide. boron carbide, boron nitride. tantalum casbidefsteel. tungsren. molybdenum. Epoxy and polyester. with the former most commonly used; others are phenolics, fluorocarbons. polyethersuifone. silicon. and polyimides. Polyetheretherketone: tougher than thermosets but lower resmtance to temperature. Aluminum. aluminum-lithium. magnesium, and titanium; fibers are graphite, aluminum oxide. silicon carbide. and boron. Silicon carbide. silicon nitride. aluminum oxide. and mullite: fibers are various ceramics. . ——-—__—_________________________ 9-4 Reinforcing Fibers Glass E Type (borosilicate) S Type (magnesia — alumina -— silicate) Graphite (carbon) High stq., high stiffness Aramids (Kevlar) Very high stq., high toughness Boron High stq., resistance to high temp. Properties of Reinforced Fibers Table 9.2 9-5 TABLE m PROPERTIES OF REINFORCING FIBERS —___________________________._._._.__._———————————w———— TENSILE STRENGTH ELASTIC MODULUS DENSITY RELATIVE TYPE (MPa) (GPa) (kg/m3) COST _________,,___________..___.____——————- Boron 3500 380 2600 Highest Carbon High strength 3000 275 1900 Low High modulus 2000 415 1900 Low Glass E type 3500 73 2480 Lowest 8 type 4600 85 2540 Lowest Kevlar 29 2800 62 1440 High 49 2800 1 17 1440 High W Note: These properties vary significntly depending on the material and method of preparation. 9-6 Short or long Continuous lIbCI'S. or flakes fibers FIGURE 9.2 Schematic ilustration of methods of reinforcing plastics (matrix) with (21) particles, and (b) short or long fibers or flakes. The four layers of continuous fibers in illustration (C) are assembled into a laminate structure. 9-7 Kevlar 29 Kevlar 49 . . (Resin impregnated strands) . . S_G]ass High-strength Boron o High-modulus graphite . o E-Glass Specific tensile strength (in. X 106) 0 Steel 0 Aluminum I 0 1 2 3 4 5 6 7 Specific tensile modulus (in. x 106) FIGURE 9_3 # Specific tensile strength (tensile strength-to—density ratio) and specific tensile modulus (modulus of elasticity—to-density ratio) for various fibers used in reinforced plastics. Note the wide range of specific strengths and stiffnesses available. _______________.________________________————- 9-8 Matrix Materials Function: 1) Transfer stress to fibers 2) Protect fibers 3) Prevent crack propagation Materials (examples) Epoxy Polyester Phenolic Silicon 9-9 Kevlar fibers Graphite fibers Diameter 0.1 mm Diameter 0.012 mm Matrix Boron Tungsten FIGURE 9.4 (Kevlar) reinforcing fibers. Source: J. Dvorak, Mercury Marine Corporation, and F. Garrett, Wilson Sporting Goods Co. (b) Cross—section of boron fiber-reinforced composite material. (a) Cross-section of a tennis racket, showing graphite and aramid 9-10 a? A 6 300 3 .5' 5 X E E 4 Long glass fibers 2 E 200 s, a. 3 E 5 g a j; w E g 2 100 .a E‘ 5 —- 1 E 0 0 0 10 20 30 40 0 10 20 30 40 Reinforcement (%) Reinforcement (%) .. 6 40 FA 400 e :2 3: 5 300 ‘55 30 n. 8- 4 E a: a 3 a: E” it“ s 3 Carbon fibers 20 a; g 200 2 g e :«a 2 g a 1 10 E 100 :0 Long and short E 0 glass fibers 0 O Reinforcement (%) Reinforcement (‘70) Fl (3 U R E 9.5 Effect of the amount of reinforcing fibers and fiber length on the mechanical properties of reinforced nylon. Note the significant improvement with increasing percentage of fiber reinforcement. Source: Courtesy of Wilson Fiberfill International. ___H______._________.____—-————— 9-1 1 Thermal conductivity Thermal expansion Electrical resistance Creep resistance Endurance limit Wear resistance CI] 40% carbon filled 40% glass filled Unfilled m? The effect of type of fibers on various properties of fiber- reinforced nylon 6,6. Source: NASA. M 9-12 2.0 0.5 we Un'd'rectional I 1-5 1 1 1000 '3 3 G! '5' CL: 15's 1.0 2 5 E 500 3 '5 r: G) E" 3L Glass content (% by weight) FIGURE 93 ———'———-——_' ' I The tensile strength of glass—reinforced polyester as a function of fiber content and fiber direction in the matrix. Source: R. M. Ogorkiewicz, The Engineering Properties of Plastics. Oxford: Oxford University Press, 1977. 9-13 Applications of Reinforced Plastics Early reported uses: Phenolic tank with asbestos fibers (1907) Counter tops, Formica, epoxies, (1920’s and 1930’s) Boats, Fiberglass (1940’s) More recent uses: Aircraft Helicopter blades Helmets Autobodies Leaf springs Golf club shafts Surf boards Fishing rods Tennis rackets 9-14 Double coating of polyurethane lacquer with nonskid finish Impact and uitraviolet-resistant, Ext -t h that-1:3: Prian lecarbonate skin multiaxiai glass weave Embedded honeycomb Glassefinber sheet (paper) reinforcement Carbon or LamiIIated composite stringer Glass Section on A-A reinforcement Ultralight Giass weave expanded polystyrene reinforcement foam core within honeycomb Compound layer <3 . FIGURE 9.1 ________—————————— Cross-section of composite surfboard, an example of advanced materials construction. Source: Ken 2d ed., p. 133. Institute of Metals, 1990. Easterling, Tomorrow '5 Materials, 1 945 Metal — Matrix Composites Compared to polymer matrix: Higher resistance to elevated temp. Higher ductility and toughness Higher density More difficult to process Common Matrix Metals Aluminum Magnesium Titanium Common Fiber Materials Graphite Aluminum Oxide Silicon Carbide Boron Table 9.3 9-16 TABLE 93 _ METAL-MATRIX COMPOSITE MATERIALS AND APPLICATIONS wm.—————_—————————_—\ FIBER MATRIX APPLICATIONS —.—_—-_u——-——————————-———\_ Graphite Aluminum Satellite, missile, and helicopter structures Magnesium Space and satellite structures Lead Storage-battery plates Copper Electrical contacts and bearings Boron Aluminum Compressor blades and structural supports Magnesium Antenna structures Titanium Jet-engine fan biades Alumina Aluminum Superconductor restraints in fission power reactors Lead Storage-battery plates Magnesium Helicopter transmission structures Silicon carbide Aluminum, titanium Superalloy (cobalt-base) Superall0y High-temperature structures High~temperature engine components Molybdenum, tungsten High-temperature engine components 9-17 Ceramic -— Matrix Composites Resistance to high temp. (3000 T) and corrosive environments Lack toughness Common Matrix Metals Silicon Carbide Silicon Nitride Al Oxide Mullite (Al, Si, 0) Applications Jet engines Automotive engines Mining equipment Pressure vessels 9-18 Honeycomb Structure High specific strength and stiffness Bonding between core and skin: adhesives brazing Applications Aircraft, Air frame Aerospace Transportation equipment (trucks, rail) Buildings 9-19 (b) (c) (a) Graphite stringer 1.0 mm (0.040 in.) Graphite skins Aluminum stringer 0.76 mm (0.030 in.) 1.3 mm (0.050 in.) Kevlar skin 1.3 mm (0.050 in.) Metal honeycomb core 12.7 mm (0.50 in.) Aluminum skin 0.8 mm (0.032 in.) Three types of structures for aircraft fuselage: (a) conventional metal structure; (b) honeycomb structure; (c) reinforced plastic structure. Source: Sikorsky Aircraft, Division of United Technologies. 9-20 Mid-term Example Questions 1. A 6061-T6 metal is an alloy consisting mostly of A) Steel B) Copper C) Nickel D) Aluminum 2. lnconel is an aluminum based alloy commonly used in casting engine blocks A) True B) False 3. Stiffness may be defined as A) energy per unit volume dissipated before fracture B) resistance to permanent indentation C) stress divided by strain D) amount of plastic deformation before fracture E) none of the above 06-03 courses/520/sample exam questions ...
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This note was uploaded on 10/13/2010 for the course INDS 354 taught by Professor Shell during the Summer '05 term at University of Cincinnati.

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chapter9 - CHAPTER 9 COMPOSITE MATERIALS: STRUCTURE,...

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