RTM Flashcards
What is Resin Transfer Molding (RTM)?
The creation of reinforced plastics or fiber composites
Composites are different in the instance that the material is created during the manufacturing of the part
Process(5)
- Fibers placed in mold
- Resin driven into mold by pressure difference
- Curing
- De-molded
- Cycle times are about an hour (considerably longer for epoxy resins)
Composite Properties depend on … (3)
- Properties of fiber & resin
- Volume fraction of fiber
- Fiber orientation
Properties of RTM
Brittle – fiber
High strength – fiber
Viscous – resin
Required Pressure Difference =
V = (P_dK)/(Lmu)
V: velocity
P_d: Pressure difference
L: Length of flow
mu: dynamic viscosity
k: permeability (m^2)
Injection Time =
(L_inj^2 mu)/(2P_d*K)
L_inj: Injection length
mu: viscosity
k: permeability
P_d: Pressure Difference
k: permeability
What is Resin & Primary Types?
Resin is thermo-setting plastic that enters as a viscous liquid and then cures during the process
Epoxies
Polyesters
Expoxies (4)
Mixed w/ hardener
Ratio b/w the two must be controlled to achieve desired ductility
Takes longer to set
For High-performance applications where toughness is favored
Polyesters (3)
Mixed w/ starter compound & cobalt
Set much faster than epoxies
Favored over expoxies
Other Resin Types (2)
1.Vinyl esters
2.Bio-based
Issues with RTM(2)
1.Variation in fiber volume fraction
2.Internal Runners
Methods
1.Pressure Controlled
2.Volume Controlled
3.Resin Infusion
4.Light RTM
Unidirectional (UD) composite
All fibers in 1 direction
Will fail if loaded in perpendicular direction
0/90 Cross-ply
Fibers orientated in 2 directions
+/- 45 degree angle orientation
Volume fraction
Fraction of the volume that is composed of fibers
