Resin Transfer Molding (RTM) is a closed-mold composite process where dry technical textile preforms are placed in a sealed mold and impregnated with injected resin. The textile architecture controls strength, flow, and performance, making RTM ideal for producing lightweight, high-strength, and precision-engineered composite components.
Step by Step Guide
- Mold Preparation
Clean mold halves, apply release agent/gel coat, and set injection & vent ports. - Fiber Preform Placement
Place dry textile reinforcements in the mold, shaped to near-net geometry. - Mold Closing & Sealing
Clamp the mold tightly; apply vacuum if required to remove air. - Resin Injection
Inject low-viscosity resin under pressure to fully wet the fibers. - Curing
Apply heat/catalyst to polymerize and solidify the composite. - De-molding
Open mold and remove the finished part.
Material Used
Fibers:
- Glass Fiber (E-glass)
- Carbon Fiber
- Aramid (Kevlar)
- Basalt Fiber
Fabrics / Preforms:
- Woven fabrics (biaxial, triaxial)
- Non-crimp fabrics (NCF)
- Multiaxial stitched fabrics
- 3D woven / braided preforms
Advantages
- Excellent surface finish on both sides
- High dimensional accuracy
- Controlled fiber-to-resin ratio
- Low emissions (closed mold process)
- Suitable for complex geometries
Limitations
- High tooling and mold cost
- Complex process design (resin flow control)
- Risk of voids or dry spots
- Moderate production cycle time
Applications & End Products
- Automotive panels, EV components
- Aerospace interior structures
- Marine parts (hulls, decks)
- Wind turbine components
- Sports goods (helmets, bicycles)
- Electrical enclosures, industrial housings
Selection Criteria (When to Use RTM)
- Medium-volume production with repeatability
- Requirement of both-side surface finish
- Complex shapes with high precision
- Lightweight, high-strength structural parts
- Need for controlled fiber architecture (technical textiles)