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Composite Materials

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Published in: Mechanical
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Presentation on Composite Materials.

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  1. Composite material
  2. Composite a e (Syllabus) Introduction; constitution and classification of composites - particle- reinforced, fiber- reinforced, metal matrix-fibre composites, hybrid composites, structural composites and their applications; processing of fibre reinforced composites; application of composite materials
  3. WHAT ISA COMPOSITE MATERIAL? A materials system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents. or Two or more chemically distinct materials which when combined have improved properties over the individual materials. Composites could be natural or synthetic.
  4. Composites A judicious combination of two or more materials that produces a synergistic effect. A material system composed of two or more physically distinct phases whose combination produces aggregate properties that are different from those of its constituents. To obtain a more desirable combination of properties (principle of combined action) e.g., low density and high strength 4
  5. Importance of Composite Materials Composites can be very strong and stiff, yet very light in weight, so ratios of strength -to - weight and stiffness -to - weight are several times greater than steel or aluminum. Fatigue properties are generally better than for common engineering metals. Toughness is often greater too Composites can be designed that do not corrode like steel Possible to achieve combinations of properties not attainable with metals, ceramics, or polymers
  6. Properties of Composite Material In selecting a composite material, an optimum combination of properties is usually sought, rather than one particular property Fuselage and wings of an aircraft must be lightweight and be strong, stiff, and tough Several fiber reinforced polymers possess this combination of properties Example: natural rubber alone is relatively weak; adding significant amounts of carbon black to NR increases its strength dramatically.
  7. One Possible Classification of Composite Materials 1. 2. Traditional composites - composite materials that occur in nature or have been produced by civilizations for many years Examples: wood, concrete, asphalt Synthetic composites - modern material systems normally associated with the manufacturing industries, in which the components are first produced separately and then combined in a controlled way to achieve the desired structure, properties, and part geometry
  8. Components in a Composte Material Nearly all composite materials consist of two phases: 1. 2. Primary phase - forms the matrix within which the secondary phase is imbedded Secondary phase - imbedded phase sometimes referred to as a reinforcing agent, because it usually serves to strengthen the composite The reinforcing phase may be in the form of fibers, particles, or various other geometries
  9. - Matrix - is continuous - Dispersed - is discontinuous and surrounded by matrix Dispersed phase Fig.l Matrix phase 9
  10. phase Dispersed phase (a) (d) variations (b) esign (c) (e)
  11. Functions of matrix Binds fibre Act as medium Protect fibre Prevent propagation of cracks.
  12. Essentials of matrix phase o It should be ductile Bonding strenth should be high Corrosion resistant
  13. Classification of dispersed phase The dispersed phase can be fibre particle etc. Fibres: 1.Glass fibres 2.Carbon fibres 3.Aramid fibres(Aromatic) Particles (metallic or non metallic) Flakes : 2-d particles Whiskers: thin crystals with high impact ratio e.g. graphite, silicon carbide etc.
  14. Functions of the Mätrux (Primary Phase) aterial Provides the bulk form of the part or product made of the composite material. Holds the imbedded phase in place, usually enclosing and often concealing it. When a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent.
  15. The Reinfotcong se (Secondary Phase) Function is to reinforce the primary phase Imbedded phase is most commonly one of the following shapes: Fibers Particles Flakes In addition, the secondary phase can take the form of an infiltrated phase in a skeletal or porous matrix Example: a powder metallurgy part infiltrated with polymer
  16. posite Survey Particle-reinforced Composites Fiber-reinforced Continuous Discontinuous (aligned) (short) Aligned Randomly oriented Structural Large- particle Dispersion- strengthened Laminates Sandwich panels
  17. icatlon o -Composite Mate Lia s by Matrix: Ceramic matrix composites (CMC): — Silicon carbide-silicon carbide (SiC-SiC) — Same material both matrix and filler BUT filler different form such as whickers, chopped fibers or strands to achieve preferred properties.
  18. Hybrid Composites Incorporation of two or more fibres within a single matrix resulted in formation of hybrid composite,
  19. Hybrids: configuration
  20. RID COM Hybrid materials are composites consisdng of two consfituents at the molecular level. nanometer or Commonly one of these compounds is and morgamc the other one in nature, Thus, they differ from orgamc fradifional composites where the consdtuents are at the macroscopic (micrometer to millimeter) level, Mixing at the microscopic scale leads to a more homogeneous material that either show characterisfics in between the two phases or even new properfies.
  21. C ificaüon. Hybrid materials can be classified based on the possible interacüons connecdng the inorganic and orgamc species, Class I hybrid materials are those that show weak interacüons between the two phases, such as weak elecfrostaüc interacdons, or Class 11 hybrid materials are those that show sfrong chemical interacdons between the components such as covalent bonds,
  22. ADVANTAGES OF—HYBRID AL COMPO MATERIALS ' Inorganic clusters or nanoparticles with specific opdcal, elecfronic or magnedc properdes can be incorporated in organic polymer matices. ' Confrary to pure solid state inorganic materials that often require a high temperature freaünent for their processing, hybrid materials show a more polymer-like handling, either because of their large orgamc content or because of the formadon of crosslinked inorganic networks from small molecular precursors just like in polymerizadon reacdons.
  23. Structural Composites The properties of structural composites depend on Constituents Geometrical design
  24. Types of Structural Composites LaminaÜ Is composed of two-dimensional sheets or panels that have a preferred high strength direction such as is found in wood and continuous and aligned fiber-reinforced plastics. The layers are stacked and cemented together such that the orientation of the high-strength direction varies with each successive layer. One example of a relatively complex structure is modern ski and another example is plywood.
  25. Structural Composites: Sandwich Panels: Consist of two strong outer sheets which are called face sheets and may be made of aluminum alloys, fiber reinforced plastics, titanium alloys, steel. Face sheets carry most of the loading and stresses. Core may be a honeycomb structure which has less density than the face sheets and resists perpendicular stresses and provides shear rigidity. Sandwich panels can be used in variety of applications which include roofs, floors, walls of buildings and in aircraft, for wings, fuselage and tailplane skins.
  26. Structural Composites Stacked and bonded fiber-reinforced sheets -stacking sequence: e.g., 0/90 -benefit: balanced, in-plane stiffness Sandwich panels •low density honeycomb core •benefit: small weight, large bend stiffness face sheet adhesive laye» Fabricated sandwich panel
  27. pplications of H OSITES 'Scratch-resistant coatings with hydrophobic or anti-fogging properties. 'Nanocomposite based devices for electronic and optoelectronic applications including light-emitting diodes photodiodes, solar cells gas sensors and field effect transistors 'Fire retardant materials for construction industry. 'Nanocomposite based dental filling materials. electrolyte materials for applications such as solid-state lithium 'Composite batteries or supercapacitors Corrosion protection
  28. 1. 2. 3. Another Classification of Composite Materüals Metal Matrix Composites (MMCs) - mixtures of ceramics and metals, such as cemented carbides and other cermets Ceramic Matrix Composites (CMCs) - A1203 and SiC imbedded with fibers to improve properties, especially in high temperature applications The least common composite matrix Polymer Matrix Composites (P MCs) - thermosetting resins are widely used in PMCs Examples: epoxy and polyester with fiber reinforcement, and phenolic with powders
  29. Fibers Filaments of reinforcing material, usually circular in cross-section Diameters range from less than 0.0025 mm to about 0.13 mm, depending on material Filaments provide greatest opportunity for strength enhancement of composites The filament form of most materials is significantly stronger than the bulk form As diameter is reduced, the material becomes oriented in the fiber axis direction and probability of defects in the structure decreases significantly
  30. Fiber Orientation — Three Cases One-dimensional reinforcement, in which maximum strength and stiffness are obtained in the direction of the fiber Planar reinforcement, in some cases in the form of a two-dimensional woven fabric Random or three-dimensional in which the composite material tends to possess isotropic properties
  31. Materials for fiber Fiber materials in fiber reinforced composites: Glass - most widely used filament Carbon - high elastic modulus Boron - very high elastic modulus Polymers - Kevlar Ceramics - SiC and A1203 Metals - steel The most important commercial use of fibers is in polymer composites
  32. The interface There is always an interface between constituent phases in a composite material For the composite to operate effectively, the phases must bond where they join at the interface Primary (matrix) phase Secondary (reinforcing) phase, fiber Interface Figure 9.4 - Interfaces between phases in a composite material: (a) direct bonding between primary and secondary phases
  33. Metal Matrix Composites (MMCs) A metal matrix reinforced by a second phase. Reinforcing phases: 1. 2. Particles of ceramic (these MMCs are commonly called cermets) Fibers of various materials: other metals, ceramics, carbon, and boron
  34. Metal matrix composites (MMC): - Metal matrix: Al, Mg, Fe, cu, Ni — Different metal or another material, such as a ceramic or organic compound — Example: Al-SiC (silicon carbide) — Example: Al-A1203 (aluminum oxide) High strength, high stiffness, dimensional stability, high temperature and toughness.
  35. co Ion: MMCs are made by dispersing a reinforcing material into a metal matrix. 'The reinforcement surface can be coated to prevent a chemical reaction with the matrix. 'For example, carbon liber are commonly used in aluminium matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminium to generate a brittle and water-soluble on the surface of the fibre. compound 'To prevent this reaction, the carbon fibres are coated with nickel or titanium boride
  36. Fiber Reinforced Polymers (FRPs) A PMC consisting of a polymer matrix imbedded with high-strength fibers. Polymer matrix materials: Usually a thermosetting (TS) plastic such as unsaturated polyester or epoxy Can also be thermoplastic (T P), such as nylons (polyamides), polycarbonate, polystyrene, and polyvinylchloride Fiber reinforcement is widely used in rubber products such as tires and conveyor belts
  37. Fibew inforced Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon tibers. Fibers increase the modulus of the matrix material. The strong covalent bonds along the fiber's length gives them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved. Fibers are difficult to process into composites which makes fiber- reinforced composites relatively expensive. Fiber-reinforced composites are used in some of the most advanced, and therefore most expensive, sports equipment, such as a time-trial racing bicycle frame which consists of carbon fibers in a thermoset polymer matrix. Body parts of race cars and some automobiles are composites made of glass fibers (or fiberglass) in a thermos(
  38. Fiber Orientations in Fiber Reinforced Composites Continuous an(l aligne(l fibers Discontinuous an(l aligne(l fibers Discontinuous anci ran(lomly oriented fibers Note: Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus.
  39. A fiber-reinforced composite (FRC) is a composite building material that consists of three components: (i) the fibers as the discontinuous or dispersed phase, (ii) the matrix as the continuous phase, and (iii) the fine interphase region, also known as the interface. This is a type of advanced composite group, which makes use of rice husk, rice hull, and plastic as ingredients. This technology involves a method of refining, blending, and compounding natural fibers from cellulosic waste streams to form a high-strength fiber composite material in a polymer matrix. The designated waste or base raw materials used in this instance are those of waste thermoplastics and various categories of cellulosic waste including rice husk and saw dust.
  40. Common FRP Structure Most widely used form of FRP is a laminar structure, made by stacking and bonding thin layers of fiber and polymer until desired thickness is obtained. By varying fiber orientation among layers, a specified level of anisotropy in properties can be achieved in the laminate Applications: parts of thin cross-section, such as aircraft wing and fuselage sections, automobile and truck body panels, and boat hulls
  41. FRP Properties High strength-to-weight and modulus-to-weight ratios Low specific gravity - a typical FRP weighs only about 1/5 as much as steel; yet, strength and modulus are comparable in fiber direction Good fatigue strength Good corrosion resistance, although polymers are soluble in various chemicals Low thermal expansion - for many FRPs, leading to good dimensional stability Significant anisotropy in properties
  42. FRP Applications Aerospace - much of the structural weight of todays airplanes and helicopters consist of advanced FRPs. Automotive - somebody panels for cars and truck cabs Continued use of low-carbon sheet steel in cars is evidence of its low cost and ease of processing. Sports and recreation Fiberglass reinforced plastic has been used for boat hulls since the 1940s Fishing rods, tennis rackets, golf club shafts, helmets, skis, bows and arrows.
  43. Guide to Processing Composite Materials The two phases are typically produced separately before being combined into the composite part. Processing techniques to fabricate MMC and CMC components are similar to those used for powdered metals and ceramics Molding processes are commonly used for PMCs with particles and chopped fibers Specialized processes have been developed for FRPs.
  44. Composite Manufacturing Processes Particulate Methods: Sintering Fiber reinforced: Several Structural: Usually Hand lay-up and atmospheric curing or vacuum curing
  45. Polynner-matl'ix comlxosite processes Open-face molding Hand lay-up Spray molding Automated lay-up Tape lay-up Filament winding Braiding Tube rolling Pultrusion Matched-die molding Fiber preform Resin transfer molding Structural reaction vinoection molding Prepreg Sheet molding compound Bulk molding compound Impregnation Curing Vacuum bag Autoclave figure 15.4 11tviu/McGraco-Hi11 0 2000 lhe McGraw-I-fill Companies, Inc.,
  46. pen Mold Processes Only one mold (male or female) is needed and may be made of any material such as wood, reinforced plastic or , for longer runs, sheet metal or electroformed nickel. The final part is usually very smooth. Shaping. Steps that may be taken for high quality 1. Mold release agent (silicone, polyvinyl alcohol, fluorocarbon, or sometimes, plastic film) is first applied. 2. Unreinforced surface layer (gel coat) may be deposited for best surface quality.
  47. Hand Lay -Up: The resin and fiber (or pieces cut from prepreg) are placed manually, air is expelled with squeegees and if necessary, multiple layers are built up. Hardening is at room temperature but may be improved by heating. Void volume is typically 1%. Foam cores may be incorporated (and left in the part) for greater shape complexity. Thus essentially all shapes can be produced. Process is slow (deposition rate around 1 kg/h) and labor- intensive Quality is highly dependent on operator skill. Extensively used for products such as airframe components, boats, truck bodies, tanks, swimming pools, and ducts.
  48. _-SPRAY•UPMOLDING A spray gun supplying resin in two converging streams into which roving is chopped • Automation with robots results in highly reproducible production Labor cos• Roving Catalyzed resin Chopper Mold Spray gun Accelerated resin
  49. Tape-Layln Machine (Automated Lay-Up) Cut and lay the ply or prepreg under computer control and without tension; may allow reentrant shapes to be made. • Cost is about half of hand lay-up • Extensively used for products such as airframe components, boats, truck bodies, tanks, swimming pools, and ducts.
  50. Filament Winding Characteristics Because of the tension, reentrant shapes cannot be produced. CNC winding machines with several degrees of freedom (sometimes 7) are frequently employed. •The filament (or tape, tow, or band) is either precoated with the polymer or is drawn through a polymer bath so that it picks up polymer on its way to the winder. Void volume can be higher (3%) •The cost is about half that of tape laying Productivity is high (50 kg/h). Applications include: fabrication of composite pipes, tanks, and vessels. Carbon fiber reinforced rocket motor pressure cases used for this way. Space Shuttle and other rockets are made
  51. Pultrusion Fibers are impregnate with a prepolymer, exactly positioned with guides, preheated, and pulled through a heated, tapering die where curing takes place. Fortning guides Coated fiber Preheat Heated die ttÅt Pull cut I I Emerging product is cooled and pulled by oscillating clamps Small diameter products are wound up •Two dimensional shapes including solid rods, profiles, or hollow tubes, similar to those produced by extrusion, are made, hence its name 'pultrusion'
  52. Vapor deposition 'Physical vapor deposition: The fiber is passed through a thick cloud ofvaporized metal, coating it. In-situ fabrication technique Controlled unidirectional solidification of a alloy can eutectic result in a two-phase microstructure with one of the phases, present in lamellar or fiber form, distributed in the matrix
  53. sa vantages an Materials mposite Properties of many important composites are anisotropic - the properties differ depending on the direction in which they are measured - this may be an advantage or a disadvantage Many of the polymer-based composites are subject to attack by chemicals or solvents, just as the polymers themselves are susceptible to attack. Composite materials are generally expensive Manufacturing methods for shaping composite materials are often slow and costly
  54. Books and references 1. Engineering Chemistry by Jain & Jain 2. A text book of Engineering Chemistry by Shashi Chawla •en.wikipedia.org/wiki/Composite_materiaI •www.substech.com/dokuwiki/doku.php?id=classification of composites

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