1. 1 MFGT 104 Materials and Quality Composites Professor Joe Greene CSU, CHICO MFGT 104

2. 2 Chap 9: Polymers Composites Objectives –Define the components and difference types of composites. –Explain the different types of composite construction and the reasons behind them. –Describe the various manufacturing methods used to produce composites. –List the different reinforcing materials used in composites. –List the various matrix materials used in composites. Excellent Web sites –Michigan State http://islnotes.cps.msu.edu/trp/ –U of Delaware http://www.ccm.udel.edu/publications/CU/99/ –Cornell University http://www.engr.siu.edu/staff2/abrate/NSFATE/links.htm

3. 3 Composites Composite definition –A composite is a material comprised of two or more physically distinct materials with at least one material providing reinforcing properties on strength and modulus. Natural Composites –Bone –Wood –Bamboo: Natures fiber glass due to pronounced fibrillar structure which is very apparent when fractured. –Muscle and other tissue Engineering Composites –Reinforced concrete beams –Thermoset composites: Thermoset resins (polyurethanes, polesters, epoxies) Glass fibers, Carbon fibers, Synthetic fibers, metalfibers, or ceramic fibers –Thermoplastic composites (polypropylene, nylon, polyester,TPU,polyimide) Glass fibers, Carbon fibers, Synthetic fibers, metalfibers, or ceramic fibers

4. 4 SMC Sheet Molding Compound RTM Resin Transfer Molding

5. 5 Automotive Plastics and Composites Use Exterior Composite Panels –doors Sheet Molded Compound (SMC): Camaro, Firebird and Corvette Resin Transfer Molding (RTM): Viper –hoods Sheet Molded Compound (SMC): Camaro, Firebird, Corvette, Ford trucks Resin Transfer Molding (RTM): Viper, Heavy duty trucks) –bumper beams Glass Mat Thermoplastic (GMT): Camaro, Firebird, Venture, Transport, Interior –floor pan Resin Transfer Molding (RTM): Corvette Engine –valve covers, intake manifolds, fluid containers, etc.

6. 6 Automotive Plastics and Composites Use SMC Sheet Molding Compound SMC Sheet Molding Compound

7. 7 Recreational Plastics and Composites Use Snow Equipment –skis, snow boards, snow mobiles, etc. Water Sports Equipment –water skis, water crafts, snorkel equipment, fishing gear –diving equipment Land Sports Equipment –shoes, roller blades, skate boards, tennis, golf Air Sports Equipment –plane kits

8. 8 Applications for Thermosets Epoxy –Protective coatings: maintenance coatings for industrial and marine, tank linings, industrial floorings, beer and beverage can coatings, food cans, appliance primers, hospital and laboratory furniture. –Bonding and adhesives: Automotive and aircraft industries adhesive to metals and composites. –Molding, casting and tooling: Molding compounds in electrical and electronic industries, casting resins, potting resins. Prototype and master model tools. –Laminating and composites: Binders in fiber reinforced laminates and composites. Laminates are used in printed wiring boards. Composite applications include filament winding (high performance pipes in oil fields, pressure vessels, tank and rocket motor housings), pultrusion, casting, and molding (graphite composites for aerospace applications) –Building and construction: Flooring (seamless, self-leveling, or epoxy terrazzo floors), repair of bridges and roads with glass and carbon fiber wraps, concrete crack repair, coat reinforcing bars, binders for patios, swimming pool decks, and soil around oil-well drills.

9. 9 Applications for Thermosets Polyester –Boat hulls, shower stalls, electrical components, appliances –Recreation vehicles, automotive body panels, floor pans; SMC –Soft tooling, patterns –Cultured marble, buttons, corrosion resistant tanks and parts, –Corrugated and flat paneling, simulated wood furniture, bowling balls, polymer concrete, and coatings Polyurethane –Rigid foams: (MDI) Laminated board stock, Moldings, Bun, Foam in place insulation, sprayed foam, packaging –Semi-flexible foam: (MDI and TDI) Moldings, Integral-skin moldings –Flexible foam:(TDI) Moldings, integral skin molding, carpet underlay –Packaging: (TDI) Furniture cushioning –Microcellular foam: (MDI) RIM parts, shoe soles –Non-foam cast elastomers –Coatings, binders, thermoplastic elastomers, sealants, paints

10. 10 Composite Classifications Reinforcement Type –Discontinuous (fibers are chopped and dispersed in matrix resin) Short fibers: fiber lengths 3mm or less (most injection molded materials) Long fibers: fiber lengths greater than 6 mm. (Some injection molded materials with 6mm fibers, Sheet Molding Compound (SMC) with 1” fibers, DFP Directed Fiber Preforms for RTM and SRIM) Particulates: fibers is forms as spheres, plates, ellipsoids (some injection molded materials reinforced with mineral fibers) –Continuous (fibers are throughout structure with no break points) Glass roving: glass bundles are wound up in a packet similar to yarn. Roving is woven into several weaves using a loom machine like in apparel. –Mat products: random swirl glass pattern. –Woven product: roving is woven into machine direction (warp) and cross direction (weft) –Uni product: roving is woven in one direction with a cross thread given to hold mat together.

11. 11 Composites Have a Fiber Preform Fiber type –Roving form that can be sprayed into a 3-D preform –Roving form that is woven into a glass sheet and then formed to shape (preform)

12. 12 Processing of Composites Open Mold processes –Hand lay-up and Spray-up –Filament winding

13. 13 Composite Classifications Resin (or matrix) type –Thermoset resins- those that undergo a chemical cross-linking reaction Epoxy: reaction of bisphenol A and epichlorohydrin Polyester: reaction of difunctional acid (or anhydride) and a difunctional alcohol (glycol) Polyurethane: reaction of alcohol and isocyanate Phenolic Silicone Melamine –Thermoplastic resins- those that are formed under heat Polyamines (nylon) (short and long fibers) Polyesters (short and long fibers) Polypropylene (short, long fibers and continuous fibers) Other thermoplastic resins (short and long fibers)

14. 14 Properties of Materials Tensile modulusDensitySpec Mod –Low alloy steel207GPa(30Mpsi)7.85 g/cc26spGPa –Aluminum 72GPa(10Mpsi) 2.8 g/cc26spGPa –Carbon fiber300GPa(40Mpsi)1.8 g/cc167spGPa –Glass fiber76GPa(10Mpsi)2.56g/cc30spGPa –Aramid fiber125GPa (20Mpsi)1.4g/cc89spGPa (Kevlar) Tensile strengthDensitySpec Str –Low alloy steel1500MPa(220Kpsi)7.85 g/cc191spMPa –Aluminum 500MPa(75Kpsi) 2.8 g/cc178spGPa –Carbon fiber2400MPa(360Kpsi)1.8 g/cc4320spGPa –Glass fiber2000MPa(300Kpsi)2.56g/cc781spGPa –Aramid fiber3000MPa (450Kpsi)1.4g/cc2140spGPa (Kevlar)

15. 15 Thermoset Definition Thermoset materials are polymers that under go a chemical reaction to build molecular weight and viscosity. Thermosets are set or crosslinked with heat and can not be reheated for forming repeated forming.

16. 16 Thermosets History Thermosets are polymers that undergo a chemical reaction during the polymerization. Thermosetting reaction is not reversible under heat. Epoxy –Standard epoxy is based on bisphenol A and epichlorohydrin. –Others based on phenols and formaldehyde or aromatic amines and aminophenols –Curing can occur at room temperature with the use of 2 component systems. Curing at elevated temperature with use of one- component. –Properties include good adhesion to many substrates, low shrinkage, high electrical resistivity, good corrosion resistance, and thermal. –Processing is achieved without generation of volatiles.

17. 17 Epoxy Chemistry Epoxy: O H H C C H + H 2 N (C) N (C) NH 2 H H H H epoxide group + amines (DETA) epoxy Other epoxy resins –diglycidyl ether of bisphenol A (DGEBRA) –tetraglycidyl methylene dianiline (TGMDA –epoxy phenol cresol novolac –cycloaliphatic epoxies (CA) Curing agents (hardeners, catalysts, cross-linking agents) –aliphatic or aromatic amines (DETA, TETA, hexamethylene tetramine,etc.) –acid anhydrides (phthalic anhydride, pyromellitic dianhydride, etc.) Active hydrogen react with epoxide groups. 15% hardener is needed

18. 18 Epoxy Chemistry

19. 19 Polyester Chemistry Unsaturated Polyesters –Thermoset reaction between a difunctional acid (or anhydride) and a difunctional alcohol (glycol) –At least some of the acid (or anhydride) features double bonds between adjacent carbon atoms for unsaturation. –Characteristic ester linkages are formed, hence the name Polyester C 6 H 4 (COOH) 2 + (CH 2 ) 2 (OH) 2 -[(CH 2 ) 2 -O- C - C- O]- terephthalic acid + ethylene glycolPolyethylene terephthalate (PET) –Acids include: maleic, fumaric, isophthalic, terphthalic, adipic, etc. –Anhydrides include: maleic, phthalic –Glycols include ethylene glycol, diethylene glycol, propylene glycol OO

20. 20 Polyester Chemistry Heat or radiation can trigger the cross linking reaction Catalyst (or initiator) is used. Methyl ethyl ketone (MEK) peroxide, benzoyl peroxide, and cumene hydroperoxide Accelerators (or promoters) speed up the reaction. Inhibitors extend shelf life (hydroquinone, tertiary butyl catechol) Condensation Reaction results in CO 2 and H 2 O Monomer required to polymerize, e.g., Styrene, to react with the unsaturations in the polyester molecules to form 3-D network. –Styrene at 30% to 50% in commercial polyester systems –vinyl toluene for vinyl ester –methyl methacrylate for methyl methacrylate ester

21. 21 Polyester Chemistry

22. 22 Polyester and Polyurethane Polyester –Thermoset reaction between a difunctional acid (or anhydride) and a difunctional alcohol (glycol) –Heat or radiation can trigger the cross linking reaction –Accelerators (or promoters) speed up the reaction. –Condensation Reaction results in CO 2 and H 2 O. –Monomer required to polymerize, e.g., Styrene at 30% to 50% in commercial polyester systems Polurethane –Reaction between isocyanate and alcohol (polyol). Condensation Reaction results in CO 2 and H 2 O. –Crosslinking occurs between isocyanate groups (-NCO) and the polyol’s hydroxyl end-groups (-OH) –Thermoplastic PU (TPU) have some crosslinking, but purely by physical means. These bonds can be broken reversibly by raising the material’s temperature, as in molding or extrusion.

23. 23 Polyurethane Chemistry Reaction between isocyanate and alcohol (polyol). Crosslinking occurs between isocyanate groups (-NCO) and the polyol’s hydroxyl end-groups (-OH) Thermoplastic PU (TPU) have some crosslinking, but purely by physical means. These bonds can be broken reversibly by raising the material’s temperature, as in molding or extrusion. Ratio between the two give a range of properties between a flexible foam (some crosslinking) to a rigid urethane (high degree of crosslinking). In PUR foams density can range from 1 lb/ft3 to 70 lb/ft3. Foams are produced by chemical blowing agents. Catalyst are used to initiate reaction. RIM process is used to produce fenders and bumper covers

24. 24 Polyurethane Chemistry

25. 25 Processing of Composites Open Mold processes –Hand lay-up –Spray-up –Vacuum bag, pressure bag, autoclave –Filament winding –Centrifugal casting Closed Mold Processes –Compression molding –Injection Molding [high pressure] –Resin Transfer Molding (RTM), Structural Reaction Injection Molding (SRIM) [low pressure] –Pultrusion

26. 26 Processing of Composites Closed Mold Processes –Compression molding [moderate pressure] –Injection Molding [high pressure] –Resin Transfer Molding (RTM), Structural Reaction Injection Molding (SRIM) [low pressure] –Pultrusion [low pressure]

27. 27 Polyurethane Processing Polyurethane can be processed by –Casting, painting, foaming –Reaction Injection Molding (RIM)

28. 28 Structural RIM Fiber preform is placed into mold. Polyol and Isocyanate liquids are injected into a closed mold and reacted to form a urethane.

29. 29 Processing of Composites Open Mold processes –Vacuum bag, pressure bag, SCRIMP –autoclave: Apply Vacuum Pressure and Heat in an oven which can be 5 feet to 300 feet long

30. 30 Thermoset Reacting Polymers Process Window –Temperature and pressure must be set to produce chemical reaction without excess flash (too low a viscosity), short shot (too high a viscosity), degradation (too much heat)

31. 31 Sheet Molding Compound (SMC) SMC is the paste that is compression molded –33% polyester resin and stryrene, which polymerizes and crosslinks –33% glass fibers (1” fibers) –33% Calcium Carbonate

32. 32 Compression Molding Compression molding was specifically developed for replacement of metal components with composite parts. The molding process can be carried out with either thermosets or thermoplastics. However, most applications today use thermoset polymers. In fact,compression molding is the most common method of processing thermosets.

33. 33 Resin Transfer Molding In the RTM process, dry (i.e.,unimpregnated ) reinforcement is pre-shaped and oriented into skeleton of the actual part known as the preform which is inserted into a matched die mold. The heated mold is closed and the liquid resin is injected The part is cured in mold. The mold is opened and part is removed from mold.

34. 34 Injection Molding Glass Reinforced Composites Plastic pellets with glass fibers are melted in screw, injected into a cold mold, and then ejected. Glass filled resin pellets

35. 35 Composites Have Directional Properties Fiber type and Fiber % –Different fibers have different strength, modulus, and strain at failure Generally, the stiffer the fiber, the smaller the strain at failure. –The higher the fiber %, the higher the properties Fiber % for automotive is 35% by volume Fiber % for aerospace is 60% by volume Fiber Orientation –Carbon fiber is Amoco high modulus pitch based fiber –Effect of orientation on carbon fiber properties Unidirectional had double the strength and triple the modulus as a quasi-isotropic material Unidirectional material had 10% of the strength and 3% of the modulus in the transverse direction as the quasi-isotropic laminate –Mechanical Properties of Carbon-Fiber Composites with Epoxy and PEEK Epoxy resin had 25% higher tensile strength and 60% higher tensile modulus than the peek composite in the 0° direction Peek resin had 40% higher strength and 330% higher Fracture strain in the 45° direction than epoxy.

36. 36 Carbon/Graphite Fibers Need for reinforcement fibers with strength and modulii higher than those of glass fibers has led to development of carbon Thomas Edison used carbon fibers as a filament for electric light bulb High modulus carbon fibers first used in the 1950s Carbon and graphite are based on layered structures of hexagonal rings of carbon Graphite fibers are carbon fibers that –Have been heat treated to above 3000°F that causes 3 dimensional ordering of the atoms and –Have carbon contents GREATER than 99% –Have tensile modulus of 344 Gpa (50Mpsi)

37. 37 Carbon/Graphite Fibers Manufacturing Process –Current preferred methods of producing carbon fibers are from polyacrylonitrile (PAN), rayon (regenerated cellulose), and pitch. PAN –Have good properties with a low cost for the standard modulus carbon –High modulus carbon is higher in cost because high temperatures required PITCH –Lower in cost than PAN fibers but can not reach properties of PAN –Some Pitch based fibers have ultra high modulus (725 GPa versus 350GPa) but low strength and high cost (Table 3-2)

38. 38 Carbon/Graphite Fibers PAN Manufacturing Process Figures 3-3 and 3-4 –Polyacrylonitrile (PAN) is commercially available textile fiber and is a ready made starting material for PAN-based carbon fibers –Stabilized by thermosetting (crosslinking) so that the polymers do not melt in subsequent processing steps. PAN fibers are stretched as well –Carbonize: Fibers are pyrolyzed until transformed into all-carbon Heated fibers 1800°F yields PAN fibers at 94% carbon and 6% nitrogen Heated to 2300°F to remove nitrogen yields carbon at 99.7% Carbon –Graphitize: Carried out at temperatures greater than 3200° F to Improve tensile modulus by improving crystalline structure and three dimensional nature of the structure. –Fibers are surface treated Sizing agent is applied Finish is applied Coupling agent is applied –Fibers are wound up for shipment

39. 39 Carbon/Graphite Fibers PITCH Manufacturing Process Figure 3-3 –Pitch must be converted into a suitable fiber from petroleum tar Pitch is converted to a fiber by going through a meso-phase where the polymer chains are somewhat oriented though is a liquid state (liquid crystal phase) Orientation is responsible for the ease of consolidation of pitch into carbon –Stabilized by thermosetting (crosslinking) so that the polymers do not melt in subsequent processing steps –Carbonize: Fibers are pyrolyzed until transformed into all-carbon Heated fibers 1800°F Heated to 2300°F –Graphitize: Carried out at temperatures greater than 3200° F to Improve tensile modulus by improving crystalline structure and three dimensional nature of the structure. –Fibers are surface treated Sizing agent is applied Finish is applied Coupling agent is applied –Fibers are wound up for shipment

40. 40 Carbon Fiber Mechanical Properties Table 3-2

41. 41 Mechanical Properties Pitch versus PAN Carbon Fiber Properties for 62% volume carbon fiber –PITCH fiber has higher density –PAN Fiber intermediate modulus has tensile strength and shear strength but a lower tensile modulus and lower thermal conductivity than PITCH intermediate modulus fiber. –PITCH High modulus fiber has higher tensile modulus and higher thermal conductivity but lower tensile strength and compressive strength than PAN Intermediate fiber.

42. 42 Directional Properties Carbon Fiber Different types of carbon fiber composites Epoxy resin with 60% volume carbon fiber, PITCH or PAN Results –High strength PAN fibers have lower modulus that high modulus PAN –High strength PITCH fibers have lower modulus that high modulus PITCH

43. 43 Directional Properties Carbon Fiber PEKK Laminates Fiber Volume Fraction is 60% Aerospace Quality –Continuous fiber has higher strength and modulus for tensile, compression, and shear in the 0° than long fiber composite. –Long Fiber PEKK composites has higher Tensile strength and modulus and Poisson ratio in the 90° direction than continuous fiber.

44. 44 Directional Properties Carbon Fiber Unidirectional (0°/ 90°) versus Quasi-isotropic laminate (0°/30°/60°/90°/120°/150°) Fiber Volume Fraction is 60% Aerospace Quality –Polymer is Epoxy and Carbon Fiber is PITCH High Modulus fiber Results –Uni-directional laminate is 40 times stronger and 92 times stiffer in the 0° direction versus the transverse 90° direction in tensile. –The quasi isotropic laminate is stronger and stiffer in tension in the 0° direction than the 90° direction. The opposite is true for compression

45. 45 Directional Properties Carbon Fiber Unidirectional (0°) versus Quasi-isotropic laminate (45°) Results –Uni-directional laminate is stronger and stiffer in the 0° direction versus the transverse 45° direction in tensile for Epoxy and PEEK –The quasi isotropic laminate is has higher fracture strain% in the 45° direction than the 0° direction for epoxy and for PEEK.

46. 46 Directional Properties Thermoplastic Composites Results –PEEK APC2 and AS-4 Carbon fiber had the highest tensile strength –Kevlar 49 had high strength but the lower tensile modulus than carbon

47. 47 Rule of Mixtures Mechanical properties of a composite material made from two materials can be estimated based upon the volume fraction of each material times the material property of each. Modulus, strength, CLTE, shrinkage, density, and others formula: Ec = Ef*Vf + EmVm = Ef*Vf + Em(1-Vf), where E is Tensile modulus, f is fiber, m is matrix, and c is composite Example,

48. 48 Rule of Mixtures Example, Density –Epoxy and Glass, –formula:  c =  f*Vf +  mVm =  f*  f +  m(1-Vf), where  is density, f is fiber, m is matrix, and c is composite

49. 49 Rule of Mixtures Example, Epoxy and Glass –Formula: Ec = Ef*Vf + EmVm = Ef*Vf + Em(1-Vf), where E is Tensile modulus, f is fiber, m is matrix, and c is composite –Formula: TSc = TSf*Vf + TSmVm = TSf*Vf + TSm(1-Vf), where TS is Tensile strength, f is fiber, m is matrix, and c is composite

50. 50 Rule of Mixtures Comparison with published data Example, –Polyester with 33% glass fibers 0/90 Ply –Experimental Tensile strength = 360 MPa Tensile modulus = 17 GPa –Rule Mixture (Theoretical) Tensile strength = 395 MPa Tensile modulus = 26 GPa –% Experimental with Theoretical Tensile strength = - 8.86% Tensile modulus = - 34.6%

51. 51 Rule of Mixtures Comparison with published data Example, –Epoxy with 60% carbon fibers 0/90 Ply –Experimental Tensile strength = 2040 MPa Tensile modulus = 134 GPa –Rule Mixture (Theoretical) Tensile strength = 2283 MPa Tensile modulus = 197 GPa –% Experimental with Theoretical Tensile strength = - 10.6% Tensile modulus = - 31.4%