VARTM processing typical process

A typical lay-up is shown in Figure 21.51. Traditional VARTM processing entailed opening and closing the resin ports manually, but this has been replaced by sequential injection automation, with resin flow monitored by film sensors such as SMARTweave. 

Figure 10.1 illustrates a commonly used VARTM setup. For a VARTM process, the environmental pressure (e.g., the atmospheric pressure) is typically utilized to provide the compressive pressure against the fiber preform... 

The major processing steps of a typical VARTM process (also see Fig. 10.1) include ... 

The resin injection pressure is limited between the environmental pressure (e.g.,the atmospheric pressure) and the vacuum. The resin injection pressure of a VARTM process is much less than the pressure applied during a typical RTM process or an autoclave/vacuum bagging process, and can limit the air void compressibility. 

Thermosetting resins are typically used in VARTM processes. Due to the geometry of a typical VARTM panel, the heat transfer analysis of the curing process only needs to be performed in the thickness direction (i.e., the... 

A typical setup for a VARTM infusion process with membrane is illustrated in Fig. 10.11. Here, the layup includes the dry reinforcing fibers as a preform on the mold. A peel ply separates the high-permeability layer (i.e., distribution media) from the preform. The membrane is placed on the distribution media and sealed to the tooling surface. Often, an additional breather material is placed between the membrane and bag to facilitate fast volatile flow to the vent. 

The RTM process begins with a dry fiber preform. The preform is placed into a matched metal mold and the mold is closed resulting in the compaction of the preform to the specified fiber volume fraction. A liquid thermosetting resin is then injected into the mold (typically at high pressure, such as 5-7 bar). The mold and resin can be preheated before injection, or the mold can be heated after injection to cure the resin. Due to the high injection pressures and often high temperatures involved, RTM tools are bulky and costly to manufacture and to process. To aid filling of the mold, vacuum may also be applied to remove trapped air. In addition, vacuum can be used to optimize the resin infusion/injection. This leads to VARTM. More information on RTM can be found in Chapters 9-11. 

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