Más contenido relacionado


Reinforced Plastics.ppt

  1. Reinforced Plastics MFG 355
  2. Composites
  3. Advanced Composites • Long (continuous) fibers • Very high performance reinforcements – Carbon and aramid • Resins are also very high performance • Typically aerospace applications
  4. Engineering Composites • Shorter fibers/fiberglass • Lower mechanical properties (stiffness) • Lower performance resins
  5. Matrix Materials • Resins – Both thermosets and thermoplastics can be used – Short fibers are generally used in thermoplastics – Long fibers are generally used with thermosets
  6. Matrix Materials • Short fiber composites – Less than 0.2 inches (whiskers) – Processed through standard thermoplastic processes • Must pass through gates, runners, and gap between processing screw and barrel walls – Thermoplastics generally benefit greatly from even the short reinforcement materials
  7. Matrix Materials – FRP • Intermediate length fiber reinforcement – The longer the fibers, the more difficult it is to coat the fibers enough to reap strength benefits – Low viscosity thermosets “wet-out” the materials better than high viscosity thermoplastics – Generally use unsaturated polyester and vinylester resins for FRP
  8. Matrix Materials – Advanced • Very long fibers or continuous fibers – Typically used with thermosets, also for “wet- out” reasons – Used generally in advanced composite parts and have greater material property requirements – Generally use epoxy resins
  9. Reinforcements • Three main types of fibers – Fiberglass – Carbon fiber or Graphite – Organic fibers, aramids (kevlar)
  10. Fiberglass • Spin molten glass • Different types of glass can be made – E-glass (improved electrical resistance) – S-glass (high strength) – C-glass (high chemical resistance)
  11. Carbon or Graphite Fiber • Originally some distinction was made— now the two refer to the same material • Made from PAN fibers, pitch or rayon fibers • Through heating, raw material looses most non-carbon atoms in the chain • Processing also aligns carbon chains • Carbon fibers have very high modulus (stiffness)
  12. Organic Reinforcement Fibers • Aramid fibers have greatest strength and modulus properties of organic fibers • Kevlar is the most commonly used aramid fiber • Aramids are strong and stiff but their greatest value is in impact applications – Front of airplane wings – Armor applications
  13. Reinforcement Forms • Fiber manufacturers package the fibers on spools called tows • Fibers are generally converted to other forms after manufacturing – Chopped fibers (including whiskers) – Mat (random) – Woven fibers – Tapes – Prepregs
  14. Manufacturing Methods • Thermoplastic processes using short fibers – Injection molding – Extrusion – Minor changes are made to accommodate the fiber reinforcements • All gaps in flow path should be increased • A resin viscosity decrease may be necessary
  15. Manufacturing Methods • Matched die or Compression molding – Reduced flow path over injection or extrusion – SMC compression molding allows for continuous fibers, mats or weaves – These processes offer parts that are finished on both sides where most other composite processes do not
  16. Manufacturing Methods • Resin transfer molding – Fiber preform is placed in the mold cavity – Preform doesn’t move—resin is pulled/pushed in
  17. Manufacturing Methods • Spray-up – Fibers are chopped, coated with resin and sprayed onto the mold
  18. Manufacturing Methods • Hand Lay-up (wet and prepreg) Prepreg Wet
  19. Fiber Orientations • Isometric materials have equal strength in all directions • Composites can be lighter weight by not having strength in the directions that it is not needed • Lay-up still has to have some balance and symmetry
  20. Vacuum Bagging • Provides for increased part consolidation • Reduces matched die mold costs
  21. Manufacturing Methods • Filament winding and fiber placement – Fiber placement has greater accuracy – Fiber placement can wind on less symmetrical and even partially concave mandrels • Tubes, tanks, wind turbine blades and rockets
  22. Manufacturing Methods • Roll wrapping – Faster than filament winding – Limited to symmetrical mandrels
  23. Manufacturing Methods • Pultrusion – High volume production – Comparable to extrusion but the main processing force is tension – Profile is pulled from the machine
  24. Plant Concepts • Many of the processes require considerable space • Curing equipment for large parts can be very large (and expensive) • Controlling volatiles (solvents and resins) must be taken care of • Molds can be both expensive and fragile