VARTM

2 Vacuum assisted resin transfer molding (VARTM) [68] 

Parts can be fabricated on a single sided open mold, which can be male or female 

The fiber reinforcement is placed in the open mold, enclosed within a bag and impregnated with the resin in conjunction with a vacuum 

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The VARTM is a hquid resin infusion process and is currentiy considered by the aircraft industry to be the favoured low cost manufacmring process for the future. It is an autoclave-free process that has been identified as reducing the cost of component processing. It is reported that dimensional tolerance and mass measurements are comparable with stitched RFI autoclave panels. A conventional blade stiffened test panel (3 X 2 ft with 4-in-high blades 0.5 in thick) has been manufactured recently at NASA by using the VARTM method, achieving a reasonable quahty. 

VARTM In this process (which is a variation oftheVARI process), the preform is placed in an open rigid tool (Figure 3.6). The layup is sealed in a flexible vacuum bag. As a vacuum is applied, resin is drawn into the preform which is compacted on the tool surface. The general advantages of vacuum processes such as VARTM are discussed below. 

VIPR This process is a development of VARTM and SCRIMP (Figure 3.8). It involves placing a vacuum chamber over the vacuum bag. Advantages include reduced fiUing time and the ability to direct the flow to regions which are difficult to fill. 

Two of the most popular of these processes are CRTM which is reviewed by Bickerton and Kelly (2012) [22] and VARTM which is discussed by Hsiao and Heider (2012) [23]. The use of vacuum to develop resin-infusion processes has been one of the most successful developments in reducing the problem of voidage as well as speeding up the process. Vacuum-based processes have enjoyed enormous growth in popularity... 

Hsiao K-T, Heider D. Vacuum assisted resin transfer molding (VARTM) in polymer matrix composites. In Advani S, Hsiao K-T, editors. Manufacturing techniques for polymer matrix composites (PMCs). Cambridge (UK) Woodhead Publishing Limited 2012. 

Zero s use is not restricted to high cost aerospace applications as A P designed the febric to provide affordable but superior performance. It can be used in a wide range of RP molding processes including resin transfer molding (RTM), vacuum assisted RTM (VARTM), resin film infusion, and hand lay-up (Chapter 5). 

Vacuum-assisted resin transfer molding (VARTM) is a process to form and shape FRP composites. Fibers are layered on a solid mold base and covered by a vacuum bag. By generating a vacuum, the vacuum bag is compacted owing to the action of atmospheric pressure, and, therefore, air bubbles are ehminated. Porous fabrics absorb excess resin and the entire material is cured to obtain better mechanical properties. This processing technology is suitable to a certain level of automation and ensures a good geometrical control and a smooth surface. 

Cain, J., Post, N.L., RifHe, J.S., Lin, Y.N., Lesko, J.J., and Case, S.W. (2004) Postcuring effects on marine VARTM FRP composite material properties for test and implementation. Composites 2004 Convention and Trade Show, American Composites Manufacturers Association, Tampa, Florida, 2004. 

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 21.51 Schematic of VARTM process with lay-up detail. Source Reprinted with permission from Heider D, Hofmann C, Gillespie JW Jr., Proceedings 45th International SAMPE Symposium/Exhibition, Long Beach, May 21-25,2000. Copyright 2000, The Society forthe Advancement of Matrerial and Process Engineering (SAMPE).

VARTM Vacuum assisted resin transfer molding. 

The vacuum assisted resin transfer moulding (VARTM) process is a variant of vacuum-infusion RTM in which one of the solid tool faces is replaced by a flexible polymeric film (Fig. 23.14). 

Fig. 23.14 A schematic showing VARTM process when a structural part is infused [78]...

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