Exam 1 Prep

Roll Wrapping

  • Typically a fabric is rolled around a mandrel
  • Need a highly drape-able fabric
  • Medium production
  • Semi -automateable
  • Good:
    • Multi-axis stiffness
    • Low start-up cost
    • Good for protoyping
    • Thin cross sections OK!
  • Bad:
    • Size is a factor
    • No complex parts
    • Need to consider mandrel material and removal
    • Voids are common, compaction can be challenging
    • Fiber/resin movement

Pultrusion

  • Continuous horizontal process
  • Produces parts of constant cross section
  • Similar to plastic extrusion
  • High thru-put
  • Low waste (typ. <5%)
  • Structural
  • V_f = ~50-60%
  • Good
    • High production
    • Continuous process
    • Low waste
    • Low cost materials
    • Structural parts OK!
    • Automated low-labor (except for start up and clean up)
  • Bad:
    • Only low-viscosity resin
    • High equipment/startup cost
    • Speed limited by how fast resin cures
    • Constant cross section only
    • Strenth only in longitudinal direction
    • No thin walls

V_f,max = 60%

Spray Up

  • Chopped fibers are sprayed onto a mold surface with initiated resin
  • Fiber glass and polyester (Rarely vinylester)
  • Good:
    • Medium production
    • Low-skilled labor
    • Can be automated
    • Inexpensive tooling
    • Inexpensive startup cost
    • Good for protoyping
    • Inexpensive materials
  • Bad:
    • Dirty
    • Potential health hazards
    • non-automated quality, it is operator dependent
    • Non-structural components
    • Not highly engineered
    • One tooled surface
    • Possibility of voids = high

Wet Lay-up w/ Vacuum Bag

  • Purpose of Bag: draw out voids and resin to raise V_f (Volume fraction of fibers)
  • V_f,max = 70%
  • Good:
    • Variety of materials
    • Fewer voids
    • Good for protoyping
    • Low-cost tooling
    • Low start-up cost
    • Can make engineering and advanced composites
  • Bad:
    • Waste with bagging materials
    • Low production
    • Quality is operator-dependent
    • One-tooled surface
  • Kit
    • Peel ply
    • Breather
    • Bleeder
    • Perforated Barrier
    • Peel ply
    • Bag

VARTM

  • Unlimited setup time

  • Low-viscosity resin required

  • Once resin is introduced there is no fixing dry fibers

  • V_f,max = 60%

  • Layers

    • Peel Ply
    • Flow media
    • Bag

  • Open Mold Manufacturing