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Reinforcement

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Reinforcement

Publié dans : Technologie, Business, Mode de vie
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Reinforcement

  1. 1. REINFORCEMENT
  2. 2. REINFORCEMENT
  3. 3. REINFORCEMENT
  4. 4. REINFORCEMENTMATRIX
  5. 5. REINFORCEMENT
  6. 6. HIGH PERFORMANCE REINFORCEMENTOTHER REINFORCEMENTS• Glass Beads – Does not increase viscosity• Asbestos – Health hazard• Confined to Brake lining & Clutch facing• Carbon Fibers – Higher StrengthReduced Coefficient of FrictionHigher Thermal & Electrical ConductivityInert Surface• Aramid – High Temperature Resistance, ToughBonding difficult• UHMWPE – Low Melting PointUnreactive Surface• Short Stainless Steel Fibers –Less build up in ViscosityConductive Applications(RFI & EMI Shield)
  7. 7. REINFORCEMENTFIBRES:
  8. 8. REINFORCEMENT
  9. 9. REINFORCEMENT
  10. 10. REINFORCEMENT
  11. 11. REINFORCEMENT
  12. 12. REINFORCEMENT
  13. 13. HIGH PERFORMANCE REINFORCEMENTADVANTAGES• High Strength & Stiffness• Light Weight• Design Flexibility• Dimensional Stability• Higher Heat Deflection Temperature• High Dielectric Strength• Corrosion Resistance• Less Finishing• Moderate Tooling Cost
  14. 14. HIGH PERFORMANCE REINFORCEMENTLIMITATIONS• Higher Processing Temperatures & Pressures• Machine Wear• Lower Impact Strength• Anisotropic Properties• Loss of Transparency• Finish• Cost• Higher Specific Gravity
  15. 15. REINFORCEMENTTARGETPROCEDURE
  16. 16. REINFORCEMENT•High Performance ReinforcementContinuous FibersVolume Loading•Low Performance ReinforcementShort FibersParticulate Reinforcing FillersVolume Loading
  17. 17. HIGH PERFORMANCE REINFORCEMENTMECHANICAL STRENGTHDepends on amount, type & arrangement of fibersCHEMICAL,ELECTRICAL & THERMAL PROPERTYDepends on choice of matrix, formulation & other additives
  18. 18. HIGH PERFORMANCE REINFORCEMENTARRANGEMENT OF FIBERS• Unidirectional - 80% loading by weight possibleContinuous Pultrusion• Bidirectional - 75% loading by weight possibleHand Lay up• Multidirectional – 10 to 50% loading by weight possibleCompression & Injection MoldingSpray, Preform, Pressure Bag
  19. 19. HIGH PERFORMANCE REINFORCEMENT
  20. 20. HIGH PERFORMANCE REINFORCEMENT
  21. 21. HIGH PERFORMANCE REINFORCEMENTUnidirectional ReinforcementLongitudinal ResponseAssumptions:• Isostrain conditions (ε of composite = ε of fiber = ε of matrix)• Matrix & Fibers are elastic• Poisson ratio of matrix = Poisson Ratio of FiberF Composite =ⁿ∑F Fiber + F MatrixForce = Stress (σ) x Area (A)Ασ(Composite) =n Ασ(fiber) + Ασ(Matrix)Volume (Vc) Composite = n Volume (Vf) Fiber + Volume (Vm) MatrixVolume Fraction of Matrix Φm =Vm ∕ VcVolume fraction of Fiber Φf = nVf ∕ VcΦm = 1 - Φf
  22. 22. HIGH PERFORMANCE REINFORCEMENTVolume = Length x AreaLength of composite = fiber = matrixσc = Φfσf + (1 - Φf )σmUnder isostrain conditionsε of composite = ε of fiber = ε of matrixσc∕ εc = Φf σf ∕ εf+ (1 - Φf )σm ∕ εmEc = Φf Ef + (1 - Φf )EmLimitation of AssumptionsMicro cracks, VoidsPerfect adhesion between fiber & matrixPractical: k Fiber utilization efficiencyK Critical Volumetric Fractionσc =K{Φf}σf + (1 - Φf )σm
  23. 23. HIGH PERFORMANCE REINFORCEMENTTransverse DirectionAssumption:• Isostress Conditions• Fiber & Matrix are elastic• Poisson Ratio of Fiber & Matrix are equalStrain terms are additiveVcεc = nVf εf + Vmεmεc = Φfεf + (1 - Φf )εmUnder isostress conditionsσc = σf =σmJc = ΦfJf + (1 - Φf )Jm1/Ec = Φf/Ef + (1 - Φf )/EmEc = Ef Em/Φf/Em + (1 - Φf )/Ef
  24. 24. HIGH PERFORMANCE REINFORCEMENTAngular Orientation of the FibersThree possible modes of failure1.Fracture at right angles to the fiber axis[σc]θ= [σc]nCos2 θ2.Failure in the Shear plane ║ to Fiber due to debonding or matrix failure[σc]θ = τm ∕sin θ cos θ3.Tension failure of matrix ║ to fiber[σc]θ = [σc]90 ∕ sin2 θ
  25. 25. HIGH PERFORMANCE REINFORCEMENTRandomly Oriented Fibers[Eθ]c = ∫[Eθ]c dθ ∕ ∫ dθIntegrate 0 to π ∕ 2By simple law of mixtureEθ = FΦf Ef + (1 - Φf )EmF = Fiber efficiency factor – function of fiber volumetric fraction & ratioof modulus of fibers to that of matrixF is in the range of 0.15 – 0.60

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