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