| Summary: | 博士 === 國立成功大學 === 土木工程學系碩博士班 === 101 === In the study, the in-plane and out-of-plane mechanical properties of novel and promising elliptical cell honeycombs are analyzed theoretically and numerically. The results of elliptical cell honeycombs are then compared with those of regular hexagonal honeycombs to evaluate their microstructural efficiency. At first, the in-plane mechanical properties of elliptical cell honeycombs including elastic moduli, Poisson’s ratios, brittle crushing strengths and plastic yielding strengths are analyzed theoretically using a unit cell model. Next, the theoretical expressions for the creep-rupturing times, creep strain rates and Monkman-Grant parameters of elliptical cell honeycombs subjected to uniaxial tension or compression at elevated temperatures are analyzed theoretically. In addition, a three-dimensional representative volume element model with appropriate periodic boundary conditions is proposed and employed to numerically calculate the out-of-plane elastic modulus, shear moduli, compressive buckling strengths and shear buckling strengths of elliptical cell honeycombs. The effects of solid distribution in cell walls on the out-of-plane mechanical properties are evaluated to give the theoretical expressions including end constraint factors and cell-geometry coefficients. The results indicate that the in-plane and the out-of-plane mechanical properties of elliptical cell honeycombs are affected significantly by the ellipticity of cell walls. The theoretical expressions for describing the mechanical properties of elliptical cell honeycombs can be written as the product of the mechanical properties of same relative-density circular cell honeycombs and a function of the ellipticity of cell walls. A series of design maps for the in-plane and out-of-plane mechanical properties of elliptical cell honeycombs are generated, and these can be utilized to determine the lowest relative density and a particular ellipticity of cell walls of elliptical cell honeycombs when a set of required mechanical properties is prescribed.
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