What is Resin Transfer Moulding (RTM)?
Resin transfer moulding (RTM) consist in a closed mould process. It is needed a male and female mould. The process of RTM consists in a preform of the fibres, transfer the resin mix into the cavity with the injection ports at high pressure. RTM offers low production cost composite parts with complex structures and large near net shapes. The main advantage of RTM is that it can be automated in operations such as preforming, reinforcement loading, demoulding and trimming. That is why RTM is considered an intermediate volume moulding process.
As it stands, RTM is a processes in which can have a balance between a reasonable performance and the production volume as it is show in Figure 1.
Resin transfer moulding (RTM) manufacturing process
The main advantage of injection moulding is the high production rate and the high automation level of the process. In Figure 2, it is shown the process of resin transfer moulding and the degree of automatization that can be achieved.
- Cutting plotter.
- Lay-up.
- Preform ready.
- Preform on mould.
- Preform.
- Prefom on injection mould.
- Resin injection.
- Demoulding.
- Finishing.
Materials
- Fibre: can be used any: carbon fibre, glass fibre, aramid…
- Resins: epoxy, polyester, vinylester and phenolic.
- Core: honeycombs cannot be used. In the case of open cellular foams, a selected ones can be used.
Advantages of Resin Transfer Moulding (RTM)
The next pros of using resin transfer moulding for manufacturing composite materials parts are summarized below:
- Class A surface: A surface: Surface definition is superior to lay-up. In addition, using matched tools for the mold, one can improve the finish of all the surfaces
- Close tolerance: Parts can be made with better reproducibility than with layup.
- Design tailorability: Reinforcement and combination of reinforcements can be used to meet specific properties.
- Fast cycles: Production cycles are much faster than with layup.
- Good mechanical properties: Mechanical properties of molded parts are comparable to other composite fabrication processes.
- Good moldability: Large and complex shapes can be made efficiently and inexpensively. In addition, many mold materials can be used.
- Lavor saving: The skill level of operator is less critical.
- Low tooling cost: Clamping pressure is low compared to other closed mold operations.
- Low volatile emission: Volatile emissions are low because RTM is a closed mold process. The worker is not exposed to chemical vapors as with the lay-up process.
Disadvantages of Resin Transfer Moulding (RTM)
Due to the nature of the developmentofthis process is rapid, some of the stated disadvantages may be overcome the advances made in this technology.
- Mould design: The mold design is critical and requires good tools or great skill. Improper gating or venting may result in defects.
- Mould filling: Control of flow pattern or resin uniformity is difficult. Radii and edges tend to be resin-rich
- Reiforcemetn movement furing reisn injection is sometimes a problem.
- Limited to smaller components: the main restriction if the hot-press size.
Applications of RTM
The most typical application for RTM are small complex aircfract and autmotive components, such as composite leaf spring. The driving force for RTM was the automotive industry, consumer products and, more recently, marine and aviation markets
