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