Composite Manufacturing Flashcards
DMM1: Manufacturing Deck 8
What is a prepreg ?
Carbon fibres with the thermoset resin impregnated into its structure, the resin is partially cured making think flexible sheets which can be reformed and fully cured
describe AFP (automatic fiber placement)
robot systems which place unidirectional prepreg slit tapes on a large mold forming the product one layer at a time
mould is then covered with a release film and heated in a vacuum autoclave to cure the resin
describe ATL Automatic Tape Laying)
robot systems which place unidirectional prepreg wide tapes on a large mold forming the product one layer at a time
mould is then covered with a release film and heated in a vacuum autoclave to cure the resin
What is the purpose of a dwell temperature in an autoclave curing process?
this stage causes the resin to become more viscous before curing allowing it to more deeply inpregnate the material
Describe SMC (Sheet moulding compound)
glass fibres are chopped up and thermoset resin is added into the resulting glass fibre pulp
rollers compress the mixture into thick sticky sheets
layers of these sheets are placed into a mould curing under heat and pressure
Describe composite pultrusion
think lengths of fibres are continously woven into a mat or veil which is dipped in resin
then it is heated in a die to give the correct cross section, pulling forces continously pull more fibers through the die in a single continous part
the long extrusion is cut to the desired lengths.
Describe RTM (Resin Transfer Moulding)
a long weave of fibre preform iis cut into think sheets
the sheets are stacked and heated over a mould allowing it to cure in place
the excess is trimmed away to create the final product
what is the difference between unidirection and fabric sheets?
unidirection has all the fibres in a single direction and is held together with a binding material whereas fabric has fibres in two or more directions and is woven together
Describe VARTM (Vacuum assisted resin transfer moulding)
dry preforms are mounted over a mould
resin is drawing over the preform with a vaccuum pump
it then cures under atmospheric pressure
What are some problems with VARTM (Vacuum assisted resin transfer moulding)?
resin flows along the smallest path creating dry points with no resins, creating weakness where the resin hasnt reached
Describe Fibre Winding
long fibres of compostie are drawn through a resin bath and woven over cylindrical mould where it cures forming the final shape