The RTM (Resin Transfer Molding) process involves injecting a reactive low viscosity resin into a closed mold under pressure injection or/and vacuum assisted conditions to soak dry fiber materials and expel gas. After soaking, the resin undergoes crosslinking reaction by heating and curing to obtain composite parts. Many people engaged in the field of composite materials are familiar with these process principles and operating methods, but they also have confusion about RTM technology and terms such as vacuum diversion, vacuum injection, and vacuum assistance. Today, we will explain it clearly in the length of an article. After reading it, I believe everyone can have a more professional and clear judgment on the process they are using.

1、 RTM process

The characteristic is the closed mold, which adopts the method of combining yin and yang molds. The process of liquid resin infiltration, infiltration, and coating of dry fibers in a closed mold cavity. Developed by RTM, there are also LRTM (Light Resin Transfer Molding) and HP-RTM (High Pressure Resin Transfer Molding) based on the pressure and flow rate of the injected resin.

2、HP-RTM

HP-RTM emerged with the high demand for lightweight civilian equipment. Using higher injection pressure and flow rate can greatly improve production efficiency, reduce production costs, and improve the impregnation quality of prefabricated components under high pressure. The disadvantage is that in order to cope with high injection pressure, the structural strength and stiffness of the mold need to be correspondingly increased to ensure that the mold does not deform under high injection pressure. Usually, this type of mold uses cored composite materials with steel pipe support, or aluminum or steel molds processed by CNC machine tools, which greatly increases manufacturing costs and mold opening time.

3、LRTM

LRTM is a low-cost manufacturing process that conforms to the development of industry needs. In the fields of shipbuilding, medical, and certain development, it does not require such high injection pressure and speed while ensuring the effectiveness of use, and the cost is controllable. Therefore, it has also been greatly developed in recent years.