Osman Pehlivanoğlu 030040089 11th Week

Polymer Matrix Composite (PMC)
A polymer matrix composite (PMC) consists of a thermoset or thermoplastic resin matrix reinforced by fibers that are much stronger and stiffer than the matrix. PMCs are attractive because they are lighter, stronger, and stiffer than unreinforced polymers or conventional metals, with the additional advantage that properties and form can be tailored to meet the needs of a specific application. High-performance fiber reinforcements are of the highest interest for military and aerospace composite applications; these incude carbon fibers and such organic fibers as aramids, liwuid crystalline polymers, and ultrahigh-molecular-wieght polyethylene. (High Performance Structural Fibers For Advanced Polymer Matrix Composites, National Research Council, p.1)
Preform Molding
In preform molding, a dry mat of the reinforcing material is performed to the approximate shape of the part and placed into the open mold. Resin is added to the perform, and the mold halves are then pressed together and heated to cure the part. During the process the resin flows, impregnating the perform, and becomes hard. The cured part is removed after the mold is opened (often with the assistance of knockout pins that are built into the mold). In a variation on the standard method, preimpregnated chopped fibers are blown onto the perform and then cured.(Handbook of Composite Reinforcements, Lee, p.323)
Pulforming
Thepultrusion process islimited to straight sections of constant cross section. There is also a need for long parts which continuous fiber reinforcement that are curved rather than straight and whose cross sections may vary throughout the length. The pulforming process is suited to these less regular shapes. Pulforming can be defined as pultrusion with additional steps to form the length into a semicircular contour and alter the cross sestion at one or more locations along the length. After exiting the shaping die, the continuous workpiece is fed into a rotating tabe with negative molds positioned around its periphery. The work is forced into the mold cavities by a die shoe, which squeezes the cross section at various locations and forms the curvature in the length. The diameter of the table determines the radius of the part. As the work leaves the die table, it is cut to length to provide discrete parts. Resins and fibers similar to those for pultrusion are used in pulforming. An important application of the process is production of automobile leaf springs. (Fundamentals of Modern Manufacturing, 4th Edition, Groover, p.340)
Side-by-Side Mills (in Roll Forming)
Mills with the side-by-side arrangement of the stands are commonly used as rail-and-structural steel and heavy-section mills.
The side-by-side mills are less costly, but have a substantial drawback. Roll speed is the same in all the stands; as strip length increases after each pass, the final stand becomes a bottleneck. Because of this, the rolling rate in these mills is quite low.(Iron and Steel Production, Bugayev, p.167)