Introduction to RTM Process and Its Evolution

 

Core Tip: RTM is a process method in which a designed preform of reinforced material is laid in the mold cavity, a low-viscosity resin is injected into the mold cavity under the action of pressure or vacuum or both, the resin completes the infiltration of the preform of reinforced material during the flow filling process, and the resin is cured to form a composite material component. It is an advanced low-cost preparation technology for composite materials and has attracted widespread attention.

 

Introduction to RTM Process:

RTM is a process method in which a designed preform of reinforced material is laid in the mold cavity, a low-viscosity resin is injected into the mold cavity under the action of pressure or vacuum or both, the resin completes the infiltration of the preform of reinforced material during the flow filling process, and the resin is cured to form a composite material component. It is an advanced low-cost preparation technology for composite materials and has attracted widespread attention.

 

The Japan Reinforced Plastics Association recommends RTM process and pultrusion process as the two most promising processes. Many European and American companies have invested heavily in the research and development of RTM process. The “Development of RTM Process Technology and Application” project invested by the European Community alone cost 2.9 million euros. The United States has set up a technical school to train RTM professionals.

 

RTM Process Features:

 

RTM is divided into two steps: pre-laying of reinforcement materials and injection of resin;

Closed mold molding process; the impregnation of reinforcement materials and resin is completed by the rapid flow of pressurized resin in a closed mold cavity, rather than manual impregnation in hand lay-up and injection processes, or expensive mechanized impregnation in prepreg and SMC processes. It is a low-cost, high-quality semi-mechanized fiber/resin impregnation method.

Low-pressure injection technology (injection pressure less than 0.4MPa);

Can produce large-sized, complex-shaped, smooth-on-both-side integral structures

 

RTM Process Evolution:

Serial Number	RTM Technology Derivatives	Main Features
1	RTM	The mold base needs support, usually reinforced concrete; The mold surface quality requirements are high, and composite materials are generally used
2	Flashless RTM	The mold base needs support, usually reinforced concrete; The mold surface quality requirements are high, and composite materials are generally used; The mold surface is equipped with an MPG (Mold Protection Guard) valve, which stops the resin pump through a signal when the pressure exceeds the limit to avoid resin overflow and flash.
3	Multi-faceted RTM	The mold base needs support, usually reinforced concrete; Multi-embedded composite surface mold, replaceable
4	VARTM	The mold base needs support, usually reinforced concrete; The mold surface quality requirements are high, and composite materials are generally used; After the mold is closed, vacuum is drawn to compact the braided body and increase the power of resin transmission.
5	((Vacuum mold) Light RTM (VM RTM Light)	The mold base does not need support, and the mold is thin and light; semi-rigid female mold, semi-flexible male mold; The mold is drawn with a lower vacuum, and the mold sealing flange is drawn with a higher vacuum; The mold surface is equipped with VMPC (Vacuum Manifold Pressure Control) sensor, when the pressure exceeds the limit, the resin pump stops working through the signal to avoid resin overflow and flash.
6	Zero Injection Pressure RTM (ZIP RTM)	Semi-rigid male mold, the bottom liner needs to be supported; Semi-flexible female mold, the bottom liner does not need to be supported, the mold is thin and light, and can be replaced frequently; The resin injection port is arranged at the edge of the mold sealing flange, and the vacuum port is arranged in the center of the mold; The VMPC (Vacuum Manifold Pressure Control) sensor is installed on the mold surface, and the feeding is stopped when the pressure in the mold cavity is positive.
7	TERTM	Rigid foam core mold, wrapped with fiber preform, placed in the traditional RTM mold cavity, low viscosity resin is injected, and the resin cannot completely impregnate the fiber preform; when heated and cured, the foam core mold expands at the same time, the resin completely impregnates the fiber preform, and solidifies. The final product is a foam sandwich product.
8	RARTM	Rigid mold supports soft mold to form a combined male mold, which cooperates with the female mold to form a mold cavity. Covering the male mold with reinforcing material, closing the mold for injection, heating and curing, the soft mold expands and squeezes glue, which can increase the fiber content of the product and solve the problems of demolding and sealing of complex surfaces.