EFFECT OF MORPHOLOGY ON THE MECHANICAL BEHAVIOR OF HETEROGENEOUS NONISOTROPIC MICROBEAMS

Abstract eng:
In many microstructures, the size of the subelement (grain, chain bundles, fillers), is not negligible as compared with the overall scale (thickness, length) and the random morphology is expected to cause an inherent statistical dispersion of the structural response, and even affect the average structural behavior. These features have a direct influence on both the design and reliability of the microsystem. In this work, we study the effects of microstructure morphology characteristics such as grain size, shape, location, modulus and statistical correlations on the generalized displacements of statically determinate beams, frequently used in MEMS. The analysis includes nonisotropic material tension-shear coupling, and its relation to structural coupling, such as tensile-bending-torsion deformations. Generalizing previous studies of isotropic heterogeneity, the beams in this analysis are made of random nonisotropic elastic elements, including heterogeneity inside the cross section. Although the beams are externally determinate, the nonisotropic behavior imposes additional internal compatibility (indeterminacy) degrees of freedom, which cannot be neglected. Timoshenko deflections and statistical homogeneity assumptions are used. We assume cross-sectional linear and parabolic functions for the normal and shear strains, respectively, for which a (3x3) compliance matrix is defined with 3 independent material constants, modeling nonisotropic crystals.

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