Spray up method
In a slight variation, to suit the necessity of bigger size parts the fibre resin and rovings are fed concurrently. The fibre rovings are fed via a chopper whereas a spray gun sprays the catalysed resin. The rollers are employed in the same manner as in condition of hand lay ups. The process is termed as spray-up shown in following figure.
Figure: Spray up method
In vacuum bag-autoclave method long carbon fibres are initially impregnated in resin and laid out upon flat table. Then epoxy gets partially cured the prepregs are placed upon shaped tool in various directions and thickness. The tool covered along with prepregs and desired thickness and shape is situated in vacuum bag that is placed in autoclave. This reasons last curing of the epoxy. The part is stripped from tool and completed to essential dimensions. Vacuum bag process consequences in parts of light weight, high stiffness and strength. Critical parts like airplane wings, parts of rudder and cargo bay doors of space shuttle are made via this procedure. The parts incur high cost and thus are not utilized widely.
Hollow cylinders are made by filament-winding method in which fibres are made to pass throughout resin bath and wound on a mandrel. The wound resin-fibre merged is cured either at room temperature or elevated temperature on mandrel itself. After the curing is completed, the cylinder is eliminated from mandrel. The method resulting in high strength because of stretched fibres is employed for making pressure piping, vesssels for chemicals and casing and fuels for rocket motor.
In closed mould method, the glass fibres mixed along with resin may be injected in a mould. In until another process the chopped fibres are continuously fed upon the top of polyethylene film. On the top of fibres the resin paste is laid that is continuously enclosed along with another polyethylene film generating a sandwiched sheet of composite. The process is continuous and automated. These sheets are then stored in maturation rooms for one to four days. Such sheets are cut to size, situated in a heated metal mould and pressed beneath hydraulic pressure to obtain shape of the mould and uniform thickness. The process termed as sheet- moulding compound process is able of generating high production volume of uniform products along with good surface finish. Auto body parts are being generated by this method.