文档介绍：RESIN TRANSFER MOLDING (RTM)
RTM PROCESS
impregnating preformed dry reinforcement in a closed mold with wet thermosetting resin under pressure
REINFORCEMENTS USED IN RTM
type
E-glass, S-glass
carbon/graphite
aramid
form
mat
fabric
textile preform architecture (knitted, braided, 3-D stitched)
preforms - preshaping of reinforcement
DESIGN OF PREFORMS
compression of fiber preform into the mold (denser the fiber, the more resistance it offers to impregnation by resin)
fiber orientation (resin flows faster along the length of the fiber than across it)
multiple layers or plies (impede plicate the resin distribution)
RESINS USED IN RTM
polyester, vinyl ester, epoxy
desired resin characteristics
must remain liquid as it is held in the reservoir prior to injection
must impregnate fiber preform quickly and uniformly without voids
must gel as quickly as possible once impregnation occurs (fast cycle time)
must possess sufficient hardness to be demolded without distortion
low viscosity critical (< 1,000 cps to impregnate preform loading of 50%)
low viscosity resin requires less pressure to achieve adequate wet-out
injection temp (typically elevated) of resin should be held as close as possible to minimum viscosity to insure preform impregnation, yet higher temp accelerates cure, cutting into injection time
RTM EQUIPMENT
resin/curing agent (catalyst) mixing equipment
positive displacement piston pumping cycle
maintain accurate ratio control between resin and curing agent
RTM process requires low injection pressures (30 psi - 100 psi)
piston type positive displacement pumps are critical due to changing back pressure conditions - as resin is pushed through reinforcement an increasing back pressure builds against metering pumps - if slippage occurs at pump, resin/curing agent ratio will be affected
with resin ponents accurately metered, sent through flexible hoses to a mix head
THE MIX HEAD USES A MOTIONLESS MIXER
thoroughly blends resin and curing agents together immedi