Hand layup

Corrosion Resistant Fiber-Reinforced Plastic (FRP). Fiber glass reinforcement bonded with furfuryl alcohol thermosetting resias provides plastics with unique properties. Excellent resistance to corrosion and heat distortion coupled with low flame spread and low smoke emission are characteristics that make them valuable as laminating resins with fiber glass (75,76). Another valuable property of furan FRP is its strength at elevated temperature. Hand-layup, spray-up, and filament-win ding techniques are employed to produce an array of corrosion-resistant equipment, pipes, tanks, vats, ducts, scmbbers, stacks, and reaction vessels for industrial appHcations throughout the world. 

Inert fillers are sometimes mixed with the resin in an effort to reduce cost. However, many fillers increase the viscosity to such an extent that with hand layup methods much more of the resin-filler mix is required to impregnate the mat. Since greater difficulty in working may also prolong processing time and there is invariably a marked drop in mechanical properties care must be taken before making a decision whether or not to employ fillers. 

Some plastics, such as the TSs and in particular the TS-RPs (RTSs), can produce products with exceptionally tight tolerances that practically meet zero tolerances. In injection or compression molding of relatively thin to thick and complex shapes, tolerances can be held to less than 0.001 in. or to even zero, as can also be done using hand layup RP fabricating techniques. 

Filament Winding, Hand Layup. Compression Molding. Iniectior. Molding. Vacuum Bag. Stamping. Coming. Pultrusion... 

Hand Layup. Compression. Injection. Spray Jp. Vacuum Bag, Autoclave, RTM. RtM, Rotational. Stamping. Autocalve. Coining... 

Fig. 10-3 Practical ail glass fiber-TS polyester RP (hand layup) recreational vehicle.

Thus, the fiber is impregnated in the partially cured resin. Depending upon the assembly the fiber is usually unidirectional, but they can also be made bidirectional or some other combination. The process of fitting the prepreg into, generally onto, the mold is called layup. Generally a number of layers of prepreg are used. The lay-up may be done by hand, called hand lay-up, or done automatically, or by a combination of automatic and hand layup. As expected, hand lay-up is more costly but is essential where one-of-a-kind products are produced. 

Several layers of dry, continuous-strand mat, woven roving, or cloth called preform are placed in the bottom half of a two-part mold, either by a hand-layup or by an automated technique (see Figure 7.90). The mold is closed, and a catalyzed liquid... 

Readily applied by hand layup to large areas, adheres tightly to most substances. 

Apart from the above three types there are custom built rubber products such as expansion joints, flexible cell covers and large size rubber foils for the caustic soda industry, and many inflatables, fabric reinforced products and thick moulded sheets for specialty applications in certain process plants. These are all hand formed in aluminium or cast iron moulds or forms by laying up process and then cured in autoclave. Here the flow of the un-vulcanized rubber during cure is not very important as the shape is already formed rather the green strength and the stiffness of rubber stock with a low scorch time are the important requisites. A rubber expansion joint made by a hand layup method and cured in autoclave is shown in the following figure 14.1. 

CT-88 Aerosol. [Chem-TrentQ Fluoro-polymer/tMganic binder disp. dry-film rdease agent and lubricant fw moldings, casting, potting, hand layup, encapsulation, filament winding. 

Eining for the heads are thermoformed afterpieces are welded. Carbon cloth is first laid using the resin. FRP is then laminated by contact molding (hand layup). The edge of the liner is left uncovered for subsequent welding. 

The only specialist use of hardness testing for composite materials is related to the assessment of cure using the Barcol hardness test available as EN 59 [16], The test is frequently used as a low-cost quality check on the cure of laminates such as hand layup CSM materials used in marine and general purpose commercial moldings. Care should be taken to avoid cracking thin laminates. 

In vacuum-bag molding the reinforcement and the resin mixed with catalyst are placed in a mold, as in the hand layup method, and an airtight flexible bag (frequently rubber) is place over it. As air is exhausted from the bag, atmospheric air forces the bag against the mold (Figure 2.46). The resin and reinforcement mix now takes the contours of the mold. If the bag is placed in an autoclave or pressure chamber, higher pressure can be obtained on the surface. After the resin hardens, the vacuum is destroyed, the bag opened and removed, and the molded part obtained. The technique has been used to make automobile body, aircraft component, and prototype molds. 

Methods of producing FRP laminates with polyesters have been described in Chapter 2. The major process today is the hand layup technique in which the resin is brushed or rolled into the glass mat (or cloth) by hand (see Figure 2.44). Since unsaturated polyesters are susceptible to polymerization inhibition by air, surfaces of the hand layup laminates may remain under-cured, soft, and, in some cases, tacky if freely exposed to air during the curing. A common way of avoiding this difiiculty is to blend a small amount of paraffin wax (or other incompatible material) in with the resin. This blooms out on the surface and forms a protective layer over the resin during cure. 

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. 

There are reinforcement preform constructions. A preform is a method of making chopped fiber mats of complex shapes that are to be used as reinforcements in different RP molding fabricating processes (hand layup, injection, etc.). Oriented fiber patterns can be incorporated in the preforms (Chapter 5). 

C/oss Capplies to hand layup, sprayup, vacuum bag, and other methods using molds made of RP/C material. It applies to parts that would be covered by Class B when they are not molded with a high degree of care. 

Design parameter Resin transfer molding Sprayup Hand layup Mat/preform SMC... 

A simple definition for a composite is two or more materials, that when combined, will retain their original identities but do interface chemically and physically when subjected to specific conditions of either time, temperature, pressure, or chemical catalyzation. Composites are widely available with different resin systems and reinforcement combinations. They are produced in several physical forms and can be shaped with conventional molding methods as well as a variety of other less conventional methods such as resin transfer molding (RTM), resin injection molding (RIM), structural resin injection molding (SRIM), hand-layup, and autoclave molding(i.e., vacuum bag technique). 

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