MECH 3503 - Composites

  1. What is rubber boi
    • Natural rubber is an agricultural crop
    • Synthetic rubber is based on petroleum 

    Why is rubber a composite? idk but there's a rubber matrix and then fibres so polymer bitch!!! wait isn't it all rubber. idk
  2. what is vulcanization. why is it important.
    the treatment that accomplishes cross linking of elastomer molecules 

    this process makes the rubber stiffer and stronger but retain extensibility - CROSS LINKING BOI!!!!! because when it's cross linked it reduced its ability to flow
  3. Processing rubber
    • compounding - adding additives such as sulfur and fillers 
    • mixing
    • shaping
    • vulcanizing - treatment
  4. whats a building drum (rubber)
    prior to molding and curing, carcass is assembled on a building drum that rotates
  5. how do you mold and cure tire
    uncured tire is placed over expandable diaphragm, then split mold is closed and the diaphragm inside expands to go against the mold. then the mold and diaphragm are heated to cure rubber

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  6. properties of composites
    • - strong and stiff but light in weight
    • - fatigue properties are generally better than for common engineering metals 
    • - toughness is greater 
    • - but expensive :( 
    • - manufacturing methods for shaping composite materials are slow and costly
  7. how to make composite materials? general (primary phase and secondary phase)
    • 1. Primary phase forms the MATRIX where the secondary phase is embedded 
    • 2. Secondary phase adds the REINFORCING AGENT because it strengthens the composite material
  8. what types of composite materials are there
    • 1. Metal Matrix Composites (MMCs) - mixtures of
    • ceramics and metals, such as cemented carbides
    • and other cermets
    • reinforced by - particles of ceramic or fibres of other metals, ceramics

    • 2. Ceramic Matrix Composites (CMCs) - Al2O3 and SiC
    • imbedded with fibers to improve properties
    • they high stiff, hard, and good compressive strength 
    • weaknesses: low toughness and bulk tensile strength, susceptible to thermal crackig 


    • 3. Polymer Matrix Composites (PMCs) - polymer resins
    • imbedded with filler or reinforcing agent
    • embedded as fibres, particles or flakes
    • most important 
    • most common example is fibre reinforced polymers
  9. what does the matrix material do
    matrix shares load with the secondary phase and hides da fiber bois
  10. in what forms does the reinforcing phase take on?
    fibres, particles, flakes
  11. what are fibres for reinforcing materials?
    • - typically circular in cross section
    • - greatest opportunity for strength
    • - diameter ~0.0025 mm to 0.13 mm
  12. fiberes - as diameter of fibre reduces...?
    as diameter is reduced, the material becomes oriented in fibre axis direction; probability of defects in structure decreases significantly
  13. difference between continuous fibres  and whisker
    continuous fibres are very long and can carry the load 

    discontinuous fibres (L/D = roughly 100)

    whiskers - discontinuous of single crystals - 0.001 mm. v strong >:)
  14. materials for fibres! x3
    • glass - most widely used
    • carbon - high elastic modulus
    • boron - VERY high elastic modulus
    • kevlar (a polymer babe)
  15. what are particles and flakes /:
    • particles are 3d smol boys
    • flakes are 2d particles /: 2 faced

    distribution is RANDON XD
  16. what are CERMETS!
    • MMC (not MCM) 
    • metal matrix composites with ceramic in a metallic matrix 

    ceramic is 96% in volume 

    can be divided in: cemented carbides or oxide based cermets
  17. what are CEMENTED CARBIDES
    a type of cermets! most common one. 

    there are more than one carbide compounds bonded in a metallic matrix

    • commonly based in
    • - tungsten (W)
    • - titanium (Ti)
    • - chromium (Cr)

    Wcriti
  18. what are fibre reinforced polymers?
    PMC consisting of polymer matrix embedded with high strength fibres

    Matrix: thermosetting plastic such as unsaturated polyester or epoxy, or thermoplastic such as nylons, polycarbonate

    the fibres are discontinuous or continues and are often stacked in a laminar structure (stacking and bonding thin layers of fibre and polymer until desired thickness is obtained)
  19. what are shaping processes of FRP?
    fibre reinforced polymers are shaped by...

    • - open mold processes - similar to layup methods
    • - closed mold processes - similar to plastic molding
    • - filament winding - filaments dipped in liquid resin and wrapped around a rotating mandrel to produce a rigid, hollow cylindrical shape
    • - pultrusion - similar to extrusion
  20. how to make a PMC
    matrix material made of thermosetting polymers or thermoplastic molding compounds.

    all are reinforced with carbon black and mainly fibres
  21. how can you combine matrix and reinforcement? (2 ways)
    1. the starting materials arrive at fabrication separately; during shaping, they're combined 

    2. the two components are combined into some starting form can that then be used during shaping, such as molding compounds or prepregs
  22. what are molding compounds
    starts with matrix and reinforcement 

    resin matrix with random dispersed fibres which can then flow 

    like a bath of these bois
  23. how to process molding compounds?
    (hint: sheet molding compounds)
    you make them into sheets using sheet molding compounds! the resin paste goes thru a series of rollers where choppers cut sum fibres in. this layuer is covered in another layer of resin.

    all rolled up in a take up spool

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  24. what are prepregs
    the second way to have matrix and reinforcement together!

    these are fibers impregnated with partially cured TS resines to facilitate shape processing. refrigerated to inhibit curing

    • prepregs are fabricated with continuous
    • filaments rather than chopped random fibers, thus
    • increasing strength and modulus
  25. first shaping process: open mold processing

    what are the three different lays to have open mold processes. what kind of composites are they used for
    open lay up used a positive or negative mold surface. starting materials applied to mold in layers to desired thickness and then cured

    • 1. hand lay up
    • 2. spray up
    • 3. automated tape-laying machines

    used for fibre reinforced polymers, a type of polymer matrix composites!
  26. what is the hand lay up method
    • its a type of open mold shaping 
    • many layers manually applied to open mold 

    v labour intensive and finished mold must be trimmed w power saw 

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    boat hulls and swimming pools are made of it
  27. what is the spray up method
    type of open mold shaping

    liquid resin and chopped fibres are sprayed onto an mold mold to make layers. randomly oriented short fibres used 

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    boat hulls, bathtubs
  28. what is automated tape laying machines
    machines that dispense prepreg tape on open mold following a programmed path
  29. what are the three parameters for curing? what is curing?
    curing cross links the polymer transforming it from liquid or highly plastic state in solid product 

    mostly done in room temperature in an autoclave 

    • time 
    • temprature
    • pressure
  30. what are three classifications of closed mold processes?
    • compression mold - mold sections brought together under pressure, forcing charge to take shape of cavity. mold halves heated to cure polymer
    • transfer mold - charge of thermosetting resin w short fibres placed in pot or chamber which is then squeezed by ram action into mold cavities 
    • injection mold - thermoplastics, broken into two:

    conventional injection molding: TP and TS, chopped fibres must be used 

    reinforced reaction injection molding: broken into: conventional reaction and reinforced reaction

    conventional reaction - two reactive ingredients are mixed and injected into a mold cavity

    reinforced reaction - same but has reinforcing fibres
  31. what is filament winding
    a type of shaping process

    resin impregnated continuous fibers are wrapped around a rotating mandrel that has the internal shape of the desired product 

    resin cured and thn mandrel removed 

    • pulled from a resin bath 
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  32. what are pultrusion processes? name two!
    workpiece is PULLED through the die (rather than pushed - extrude)

    • pultrusion - pull
    • pulform - for curvy parts with varying cross sections
  33. how does pultrusion work
    continuous fibres dipped in resin bath & pulled thru shaping die 

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  34. how does pulforming work?
    pultrusion with an additional step to make curvy using a die shoe

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  35. what materials are used in pultrusion?
    resins: epoxies, unsat. polyesters, silicones, all TS polymers 

    reinforcing: e-glass
Author
Oddishii
ID
346587
Card Set
MECH 3503 - Composites
Description
multiple bois
Updated