Resin transfer molding (RTM) is a closed molding process where preformed fibers are packed into a mold, and resin is pumped in to create composite products. The process allows for the use of various reinforcing and matrix materials, enabling the production of complex structures like automotive parts and wind turbine blades. While offering advantages such as good surface finish and fast cycle times, RTM also has limitations including high tooling costs and constraints on material flow.

1. Resin Transfer
Molding
KAMLESH JAKHAR

2. Introduction
Resin transfer molding in which fiber preform or dry fiber reinforcement is packed
into a mold cavity that has the shape of the desired part and then supply the matrix
material to form the product.
Resin transfer molding is a closed molding process.
It is also knows as liquid transfer molding process.
Molding unit has two halves namely upper half mold (core) and lower half
mold(cavity).
In this technique, resin is transferred over the already placed reinforcement.

3. Raw Materials
Reinforcing materials:-
Glass fiber, carbon fiber, aramid fiber, natural plant fibers
(sisal, banana, nettle, hemp, flax etc.)
- These fibers are used either individually or in combined form (hybrid) as a woven
mat, unidirectional mat or copped strand mat.
- Minerals fillers may also be added to improve surface finish, Fire retardants,
Accelerator, U V stabilizers, Release agent.

4. Matrix:-
Thermosets :- Epoxy resin, Methyl Methacrylate, polyester, polyvinyl
ester, phenolic resin, polyurethane resin, silicone, alkyd, thermoset
polyamides.
Thermoplastics :- Nylon, PP, PE, Styrene resin, Thermoplastic polyester,
fluoropolymer, Liquid crystal polymers and thermoplastic
elastomers.

5. Resin transfer molding procedure
• Reinforcement in terms of either woven mat or strand mat form is placed on
the surface of lower half mold.
• A release gel is applied on the mold surface for easy removal of the
composite.
• The mold is properly closed and the mold halves clamped together.
• The resin is pumped in by repeated stroking of the metering cylinders until
a predetermined volume has been delivered into the mold.

6. • Air is displaced through other vents.
• The uniformity of resin flow can be enhanced by using a catalyst as an
accelerator and vacuum application.
• After curing, the mold is opened and composite product is taken out.

7. Process

9. Process
• There are two separate containers for resin and catalyst.
• Resin container is larger than the catalyst container.
• Both the containers have separate outlets which pass through pumping
unit and opens in mixing chamber.
• Pumping unit transfers the resin and catalyst to the mixing chamber.
• Resin and catalyst is mixed thoroughly(properly) in the mixing chamber.

10. • Resin injector is used to inject the mixture to the mold cavity.
• Molding unit has two halves namely upper half mold and lower half mold.
• Heating arrangement is integrated with molding unit.
• Vents are provided to release the gases in the mold cavity during
clamping.
• End of process the molding unit is open and eject the product.

11. Components
Resin and catalyst container
Pumping unit
Mixing chamber
Resin injector
Molding unit like lower halves and upper halves.

12. Controlling Parameter
Resin viscosity
Injection time
Injection pressure
Temperature in the mold

13. • The viscosity of the resin plays an important role in resin transfer molding
process.
• Injection time depends upon viscosity of the resin.
• If viscosity of resin is high, high pressure is required which may cause
displacement of fibers knows as fiber wash.

14. Application
Complex structure can be produced.
Automotive body parts, big containers, bathtubs, helmet etc.
Vehicle panels
Boat hulls.
Wind turbine blades.
Aerospace parts.

17. Advantage
• Good surface finish on both surface of the product.
• Fast cycle time can be achieved through temperature control device.
• Higher production rate is associated with process automation.
• The process does not require high injection pressure.
• Wide range of reinforcement.

18. • Process can be manual control, semi-automatic or highly automated.
• Ability to incorporate insert and other attachment into molding.
• Parts are easily painted.
• Composite part thickness is uniform which is determined by the mold
cavity.
• Low capital investment.

19. Disadvantage
• Limited to smaller components.
• Tolling cost expansive.
• There is limitation on reinforcing materials due to the flow and resin
saturation of fibers.
• Mold maintenance is high than compression tools.
• It is produce higher volume waste because of a large pad with sprues.