Design anisotropic materials

The study of composite materials actually involves many topics, such as, for example, manufacturing processes, anisotropic elasticity, strength of anisotropic materials, and micromechanics. Truly, no one individual can claim a complete understanding of all these areas. Any practitioner will be likely to limit his attention to one or two subareas of the broad possibilities of analysis versus design, micromechanics versus macromechanics, etc. 

RTR filament-wound pipe is, however, an anisotropic material. That is, its material properties, such as its modulus of elasticity and ultimate strength, are different in each of the principal directions of hoop and longitude. It is here where the design approaches for steel and RTR pipe part company [Fig. 4-2(c)]. This behavior is a result of the construction of filament-wound RTR pipe. 

The design and properties of stimuli-responsive photoluminescent LC materials are described. It is essential to control the interactions between luminescent cores to induce stimuli-responsive luminescent properties. These classes of anisotropic materials would be important for future photonic materials. 

The model used consisted of a half helmet with three element layers of composite material through the thickness. A half model was used to take advantage of the symmetry present in the problem. The elements used were eight-noded brick elements because these elements can represent the deformation sufficiently. Anisotropic material properties were defined for each element using a user subroutine and impact was designated at the front of the helmet. 

Research has shown that the cubical triaxial tester is useful for investigating anisotropy of cohesive and noncohesive powders and the effect of particle shape and sample deposition methods. For anisotropic materials such as wheat flour, the strains in three principal directions are statistically different (Li and Puri, 1996). Wheat flour was used for the calibration of the triaxial tester to determine parameters related to a hopper design (Kamath, 1996). 

The main aspect of design and dimensioning of CMC combustion liners is the integration of CMC components into metallic structures. Therefore the different thermal expansion of the CMC components and the metallic support structure has to be taken into account carefully Based on an anisotropic material model and a failure criterion suitable for the CMC material, Finite Element Analysis supports the design of the liner. 

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. 

The discovery of mesophase order in densely crosslinked networks has led to some innovative concepts in designing and processing thermoset materials, for example, these networks could be oriented under external fields during curing reaction and result in highly anisotropic materials. These LC thermosets exhibit unique properties that show promise for applications in the aircraft, aerospace, and electronic packaging fields as well as for surface coatings with superior impact resistant properties. 

Rigid plastic composites. Reinforced plastics are often anisotropic materials. This means their strength properties are directional. Joints made from anisotropic substrates should be designed to stress both the adhesive and adherend in the direction of greatest strength. Laminates, for example, should be stressed parallel to the laminations. Stresses normal to the laminate may cause the substrate to delaminate. 

Thus, the presence of functional groups with various stmc-tures strongly affects all the physicochemical properties of these self-organized anisotropic materials and thus makes it possible to design multifunctional materials, one of the most important tendencies of modem materials science. 

Uncertainty about a material s properties, along with a questionable applicability of the simple analysis techniques generally used, provides justification for extensive end-use testing of plastic parts before approving them in a particular application. However, it should be noted that as the use of more FEA methods becomes common in plastic design, the ability of FEAs to handle anisotropic materials will demand greater understanding of the anisotropic nature of plastics. 

The model described by the mesh is then analyzed and the results displayed, if desired, by graphic means. A mesh and the corresponding analysis results are shown in Figures 10-16 and 10-17. For structural designing with plastic materials several unique requirements exist. Because plastic materials may have nonlinear and anisotropic material prop-... 

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