Design reinforced plastic theory

Orientation of reinforcement The behavior of RPs is dominated by the arrangement and the interaction of the stiff, strong fibers with the less stiff, weaker plastic matrix. The features of the structure and the construction determine the behavior of RPs that is important to the designer. A major advantage is the fact that directional properties can be maximized in the plane of the sheet. As shown in Fig. 8-55 they can be isotropic, orthotropic, etc. Basic design theories of combining actions of plastics and reinforcements... 

Processing any plastics, reinforced or unreinforced, into curved panels is relatively easy and inexpensive. Panels fit the structural theory that curved shaped can be stiffer to bend than flat shapes of the same weight. However, to withstand external pressure, a square section component will usually be heavier than one that is circular and of the same volume. Both single- and double-curvature designs are widely used to ensure a more effective use of RP materials. 

Because the fibers in mat are randomly oriented, mat-reinforced materials have essentially the same strength and elastic properties in all directions in the plane of the plate, that is, they are essentially isotropic in the plane. Consequently, the usual engineering theories and design methods employed for isotropic engineering materials may be applied. It is only necessary to know strength, modulus of elasticity, shearing modulus, and Poisson s ratio of the combined mat and resin. These can be obtained from standard stress-strain measurements made on specimens of the particular combination of fiber and plastic under consideration. 

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