Vacuum Bag Resin Infusion

Knitted continuous glass fibers were used to produce reinforced polyester composites by UV curing associated with vacuum bag resin infusion (VBRI) technique [188]. This approach allowed a maximum thickness of 13 mm. It was noticed that flexural strength and modulus decreased with the increasing sample thickness due to the reduced crossUnking density. 

The clamp is manufactured via Vacuum Bag Resin Infusion, a process that is similar to Vacuum Assisted Resin Transfer Moulding, at room temperature. Machining and drilling are required to form the necessary grooves that house the seals and the holes for the fasteners, respectively. Alternative manufacturing approaches may be used, such as wet lay-up and resin transfer moulding. A typical ProAssure Clamp is shown in Figure 12.2. 

There are other variations of the RTM, VARTM and CRTM process which belong to the class of LCM processes such as RTM light in which a caul plate is introduced on top of the bag, resin infusion under flexible tooling (RIFT), resin film infusion (RFI) and vacuum injection preform relaxation (VIPR). In addition many of the same processes are known by different acronyms. It is useful to note that as the science base of RTM improved and led to better understanding of the variables and parameters that influence the flow and dry spot creation in RTM, it led to approaches and creative ideas to improve the process and cut down the cost. This learning continues today to evolve new modifications to the LCM family of processes. For example in VIPR one can now introduce flow control effectively to modify the flow front and create a part that is better than the SCRIMP process and is of consistent quality. ... 

SCRIMP process This Seeman Composites Resin Infusion Process (SCRIMP) is described as a gas-assist resin transfer molding process. As an example glass fiber fabrics/ thermoset vinyl ester polyester plastic and polyurethane foam panels (for insulation) are placed in a segmented tool. A vacuum is pulled with a bag so that a huge amount of plastic can be drawn into the mold (Marco process approach). Its curved roof is made separately and bonded to the box with mechanical and adhesive fastening. It is similar to various reinforced plastics molding processes. 

The vacuum assisted liquid molding process has been used for the manufacture of large composite parts. In this process, a preform is placed in an open mold and a plastic vacuum bag placed on top of the mold. A vacuum is created in the mold using a vacuum pump. A resin source is connected to the mold. As vacuum is drawn through the mold, resin infuses into the preform. Application includes the fabrication of large products with complex geometry such as panels of allcomposite buses, railroad cars, and vehicle components. 

SCRIMP This process involves placing a peel-ply and distribution medium between the fibre preform and the vacuum bag (Figure 3.7). Advantages include speeding up the filling process, i.e. resin infusion. 

Figure 10.7 Example of a cricket helmet (RawTek ) from Ayrtek . The helmet is made from carhon fiber via placing the material into a female mold that is vacuum-bagged and placed in an autoclave to cure it as the resin infuses into the material, forming the shell. The helmet also features a grade 5 titanium grille that comes standard with this model. With kind permission from Ayrtek Limited.

RIFT or vacuum resin infusion is a hybrid of RTM and vacuum bag molding. In RIFT, one mold face of RTM is replaced by a flexible polymeric bag and resin is introduced into the mold by vacuum only. The process is better known in the USA as SCRIMP, which is a patented process. During resin infusion, the initial dry fiber compaction affects the permeability to resin flow and is time dependent, but when the resin enters the fibers, it appears to act as a lubricant and leads to further compaction. 

Resin film infusion (RFI), where dry fibres are laid up interleaved with layers of semi-solid resin film supplied on a release paper. The lay-up is vacuum bagged to remove the air through the dry fabrics and then heated to allow the resin to first melt and flow into the air-free fabrics, and then to cure. 

Vacuum bag moulding for retrofitting is a semi-automatic resin infusion under flexible tooling (RIFT) technique, which allows production of quality composites. In the RIFT process, dry GF are pre-formed in a mould and are taken to the side and attached to the structure. A resin supply is then channelled to the prepreg, and both are enveloped in a vacuum bag. The flow of resin into dry GF (preform) develops the composite material and the adhesive bond between composite and structure as well. 

However, the above operations show some disadvantages compared to more advanced manufacturing technologies first of all, hand lay-up of fibers requires a greater quantify of resin than normally necessary. Secondly, eliminating the superfluous part turns out to be quite a hard operation, even by means of a vacuum infusion and, as a result, the composite will be of worse qualify, since very mobile fiber layers increase the difficulty in executing a good vacuum bag. 

Afterwards the five-layer laminate stmcture with two sensors as described above was impregnated using a vacuum bag infusion process in order to make the composite part stiff. The resin employed was EPOLAM 5015 epoxy. The four connections of the top and bottom sensors, which remain outside the reinforcement at the two ends, were carefully separated from the rest of the mould. This was done by creating two vacuum submoulds inside the larger mould so that the resin would not impregnate the... 

With a transparent plastic vacuum bag, a visible dry spot occurring during the resin infusion process can be removed by inserting a vacuum needle at the dry spot and drawing the air out. 

Fig. 1. Very large parts can be produced by the patented Seaman Composites Resin Infusion Molding Process (SCRIMP), in which dry reinforcements are vacuum bagged before thermoset resin is introduced into the lay-up. Courtesy Hardcore Composites, New Castle, Del.

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