Resin-infusion processes

The cost limitations of prepreg processing have led to the development of alternative techniques in which dry fabric is infused with resin as part of the manufacturing 

Advantages of resin-infusion processes (sometimes referred to as out of autoclave processes ) include  

Scott and Heath (1992) [11] have reported that cost savings ranging from 25% to 40% are possible with liquid moulding raw materials when compared to prepreg. This is substantial as up to 50% of an autoclave component cost can be associated with the raw materials. 

There are a number of ways in which fibres or reinforcements can be impregnated with thermosetting resin during production. In the early days of composite manufacture the resin system was hand mixed and then applied by bmsh to each layer and consolidated using pressure applied through a hand-held roller. 

The sprayup process is ideal for low to medium volume applications and is particularly well suited for efficient fabrication of large shapes. The decision to choose sprayup over hand layup is based on both the mechanical properties required and the processing constraints. This process has been superseded in some applications by other advanced fabrication techniques such as RTM which are discussed in later sections. 

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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. 

SCRIMP (Seeman Composites Resin Infusion Process) 522 ... 

Epoxy vinyl ester resins are a special class of unsaturated resin. This resin is made by capping an epoxy resin with methacrylic acid and then dissolving in styrene monomer to the desired viscosity. This gives mechanical properties similar to epoxy resins, but the processibility (low viscosity allowing for resin infusion processes) of an unsaturated polyester resin. As with unsaturated vinyl esters, the most common fire retardant vinyl ester resin is based on a resin made from a halogenated system, tetrabromobisphenol A. The level of bromine in the resin and the presence of antimony will determine the fire performance of the resin. These resins are normally used for corrosion resistant equipment or when fire performance and high mechanical properties are required. It is very difficult to get a low smoke value with a brominated vinyl ester resin again due to the fact that bromine... 

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. 

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... 

This Seeman Composites Resin Infusion Process (SCRIMP) has been used to manufacture corrosion resistance bus shells (Chapter 5). North America Bus Industries (NABI) of Anniston, AL uses glass fiber-polyester plastic material from TPI Composites of Warren, RI. These new buses weigh about 10,000 kg (22,000 lb) that is 3200 kg (7000 lb) lighter than steel units. Lighter weight results in reduced axial loads, brake wear, etc. and improved fuel efficiency. 

SPRINT allows heavier weight reinforeement to be used when compared with prepreg technology and conforms readily during proeessing. Resin flow is more easily eontrolled than in the resin infusion process and the resin only has to flow through the thickness of the fiber to achieve full impregnation. 

SMARTweave [82,83] is very useful for molding thick parts and can be used with RTM, SCRIMP , vacuum assisted RTM and other resin infusion processes. 

Aker Finnyards Oy used a foam sandwich structure, utilizing an epoxy resin infusion process with carbon fiber reinforcement to make the superstructure of a prototype air cushion vehicle. 

One should notice that the resin flows quickly through the flow distribution medium layer and gradually infuses into the fiber preform in the thickness direction (see Fig. 10.1). As the length of a VARTM part is usually much larger than its thickness, the flow distribution medium layer will greatly accelerate the resin infusion process. 

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. 

Setup of the injection and double vacuum-assisted resin transfer Molding (IDVARTM) process proposed by Fan ef a/.The IDVARTM setup controls the preform porosity, compaction and the pressure inside the preform during the resin infusion process by changing the chamber vacuum pressure.The capillary flow effect and the Darcy s flow effect are both utilized in the IDVARTM process to infuse the MWCNTs enhanced epoxy into the glass fiber preform. (This original schematic Is created based on the work reported in reference 38.)... 

Govignon Q, Bickerton S, Kelly PA. Simulation of the reinforcement compaction and resin flow during the complete resin infusion process. Composites Part A Applied Science and Manufacturing, 2010 41(1) 45-57. 

Govignon Q, Allen T, Bickerton S, Morris J. Monitoring Variations in Laminate Properties Through the Complete Resin Infusion Process, in SAMPE From Art to Science Advancing Materials Process Engineering, Cincinnati, OH, 2007. 

Govignon Q, Kazmi SMR, Hickey CMD, Bickerton S. Control of laminate quality for parts manufactured using the resin infusion process, in 18th... 

Govignon Q, Verleye B, Bickerton S, Kelly PA. A 2.5D model of the resin infusion process, experiments and simulation, in 7th Asian-Australasian Conference on Composite Materials (ACCM7), Taipei, Taiwan, 2010. 

Gallez, X.E. Advani, S.G. Resin infusion process simulation (RIPS) A fast method for three dimensional geometries. Proceedings of the 55th Annual Technical Conference, ANTEC, Part 2 (of 3) April-May, Toronto, Canada, Society of Plastics Engineers Brookfield, CT, USA, 1997 2454—2458. 

Figure 9.1 Schematic of a typical resin infusion process (Umer et al., 2015, with permission of Springer Science+Business Media).

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