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Carbon Fiber (cont.)

Carbon Fiber (cont.). F-35 The Navy’s affordable tactical aircraft for the 21 st century. The first all-aspect stealth platform, all weather precision strike capability. Its simplified, low-cost maintenance and quick turnaround generates striking power. Lecture 5 & 6-2. Carbon Fiber (Cont.).

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Carbon Fiber (cont.)

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  1. Carbon Fiber (cont.) F-35 The Navy’s affordable tactical aircraft for the 21st century. The first all-aspect stealth platform, all weather precision strike capability. Its simplified, low-cost maintenance and quick turnaround generates striking power. Lecture 5 & 6-2

  2. Carbon Fiber (Cont.) Turbine blades (wind energy generators) have great length of carbon/glass hybrids (56.5 m). They use carbon fibers and curved back edge to optimize blade performance

  3. Carbon Fiber (Cont.) • The pleasant plain road bridge (composites)

  4. Carbon Fiber (applications) • Graphite fiber reinforced composites have found applications in a variety of areas: • Aerospace/aircrafts- wings, empennage (tail), fuselage, space, missiles. • Leisure: golf clubs, tennis rackets, finishing rods. • Agriculture • Materials handling equipment • Medical applications • Industrial-weaving machine Kflf9fpe0e-e0e[rtl6

  5. 4- Aramid (Kevlar) Fibers • another important class class of fibers. • Aramid is the generic name for aromatic polyamide. • Organic fiber that posses high strength and stiffness as a result of high aligned, rod like polymeric molecules. • The high strength and stiffness are combined with a relatively low density to give very high specific properties. • Most important aramid fibers are DuPont’s Kevlars, which were introduced in 1971. • used quite often to replace glass fibers in many applications due to their high strength and moduli plus ease of handleability. • Were not satisfactory to replace glass fibers in amy applications due to their high strength. • Combined with gr to give hybrid composites to take advantage of toughness and for damage resistance. • Aramid fibers are produced by an extrusion/ spinning process:

  6. Aramid (Kevlar) Fibers • aromatic polyamides are made in solution- a polycondensation of diamines and di-acid halides at low temperatures. • Polymers are spun from strong acid solution by a”dry-jet wet spinning process”.

  7. Aramid (Kevlar) Fibers • Has low longitudinal shear modulus and poor transverse properties which would result in low resistance to axial compressive failure. • Great in tension bad in compression (buckling has been observed) • Fiber properties: • Three types of Kevlar (29, 49 and 149) 29 is used widely as tire cord—has low properties but 49/149 is in our interest for high performance. • Aramid fibers possess high tensile strength and moduli combined with low density: giving then vey high specific properties. • Also possess good retention of properties to elevated temperature. • Good chemical resistance • Good fatigue resistance • - high moisture regain is a problem for processing composites- can cause adhesion/wetting problems for the resin-fiber must be dried prior to resin application.

  8. Aramid (Kevlar) Properties • Reinforcement Forms • Kevlar 49 is available in a variety of forms: • Yarns • Roving • Fabrics • Filaments are available in a variety of deniers • Yarns and roving are available in different cross-sectional size depending on numbers and sizes of filaments per strand. • Fabrics come in all verities of weave and etc. • Composites can be fabricated from a variety of starting materials. • Preimpregnated tapes, fabrics, yarns • Roving can be impregnated in-situ with the process as filament winding. • Most starting materials for gl are available for Kevlar. Composite fabrication is dictated by material form and resin system

  9. Aramid (Kevlar) Properties

  10. Aramid (Kevlar) Properties 200 not good enough

  11. Composite Properties • typical composite properties attainable with Kevlar as shown in the table for unidirectional continuous fiber reinforced epoxy composites: • The high tensile strength and moduli and low density are translated into composites with high specific strength (4x10^6 in) and high specific moduli (2.2 x 10^8 in.) • Also, in addition to above, Kevlar composites possess good fatigue resistance. • Another major characteristic material is very tough impact/damage (hard to machines) • Has two major drawbacks: • - very low compression properties make them unsuitable for compression critical structures. • Low inter-laminar shear (poor adhesion to resin) is also bad for non-tension critical applications • Best suited for tension-critical applications such as filament-wound pressure vessels.

  12. Kevlar Applications • Due to high specific tensile properties and ease of handling, Kevlar, Kevlar 49 is well qualified for filament winding of pressure vessels. • Large amount of work in this area. • In addition to pressure vessels also have applications in • Aerospace– secondary structures, interiors, helicopters, rocket motor cases, engines. • Leisure—boats, sails • Protective clothing vests, helmets. • Automotive—tires • Another very important use– hybrid composites • Is used with other advanced composites reinforcements to achieve an optimum balance of properties • Combined with kev/gr/ep • Major usage is as glass replacement

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