Anisotropic RP Design

RP methods of design analysis differ from those of traditional materials due to  

Another factor of anisotropic design analysis is greater dependence of stress distributions on materials properties. For isotropic materials, whether elastic, viscoelastic, etc., static values often result in stress fields which are independent of material stiffness properties. In part, this is due to the fact that Poisson s ratio is the only material parameter appearing in the compatibility equations for stress. This parameter does not vary widely between materials. However, the compatibility equations in stress for anisotropic materials depend on ratios of Young s moduli for different material axes, and this can introduce a strong dependence of stress on material stiffness. This approach can be used in component design, but the product and material design analysis become more closely related. 

For fixed component geometry, changes in proposed material stiffness properties result in modifications in the way in which loads are carried 

In addition to what has been reviewed in meeting structural shapes, analyses of product shapes also includes factors such as the size of available processing equipment. The ability to achieve specific shapes and design details is dependent on the way the process operates and plastics to be processed. Generally the lower the process pressure, the larger the product that can be produced. With most labor-intensive fabricating methods, such as RP hand lay-up there is virtually no limit on size (Chapter 5). 

Based on the usual data on metals, they are considered much stiffer and stronger than plastics. This initial evaluation could eliminate the use of plastics in many potential applications, but in practice it is recognized by those famihar with the behavior of plastics (RPs or URPs) that it is the stiffness and strength of the product that is important, not its material properties. 

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