Spatially Tailored and Functionally Graded Light-Weight Structures for Optimum Mechanical Performance; Final rept. 7 May 2007-6 Jan 2008

摘要

The study illustrates the effectiveness of three-phase functionally graded material systems where stiff (typically ceramic) particles are incorporated within the fiber-reinforced medium. Added particles increase the stiffness of the fiber-reinforced material reducing static and dynamic stresses and deformations, increasing buckling loads and fundamental frequencies and enhancing the response to blast loading. The micromechanical model presented in the study represents an extrapolation of the Mori-Tanaka homogenization approach to the case of the system with dissimilar inclusions. It is shown that the material constants (elastic moduli and Poisson's ratios) obtained by the method developed in the study are within the Voight-Reuss and Hashin-Shtrikman bounds. Moreover, the stiffness of a representative cross-ply material remains within the strict three-point bounds. Accordingly, the developed micromechanical model is applicable to the analysis of cross-ply functionally graded particulate-matrix fiber-reinforced materials. The tensors of stiffness obtained by the model are applied to illustrate the effectiveness of three- phase particulate-matrix fiber-reinforced materials in representative static and dynamic problems. In particular, it is shown that blast-induced deformations and stresses can be significantly reduced by adding only a small amount of particles to the outer layers of a fiber-reinforced material.