| According to the key technology of thermal protection material for the future hypersonic flight vehicle, the lightweight, multifunctional materials should be developed to satisfy the hypersonic aircraft environmental requirements. The macro-mechanical properties of the C/SiC lattice structures and the influences of carrying capacity on the form of gradient will be studied, the damage evolution and the mechanical behaviors are studied under the thermal-mechanical coupling load. This project provides a theoretical basis and technical reserves for design of the gradient lattice structures.Firstly, based on the mechanical properties of plain-woven C/SiC composite, this paper combined with two dimensional PUCK criterion, defined the trigger and evolution of the damage of the material, its influence on constitutive equation is defined, then wrote VUMAT subroutine to describe this constitutive equation that contain material damage.Secondly, this paper used the angle of the lattice structure core rod as a control variable, the influence of the change of the angle of the core rod with uniform lattice structure on the load carrying capacity is analyzed by subroutine, the load include compression, lateral pressure, shear and three-point bending, and the angle of the core rod in the side projection is 30°, 45°, 60°.Furthermore, based on 45° uniform lattice sandwich, this paper established 9 kinds of graded lattice sandwich structures by controlling the single cell size of the lattice. The influence of the gradient mode on the bending strength is studied and get some rules.Finally, based on the mechanical behavior of C/SiC composites at high temperature, the VUMAT subroutine is adapted to the thermal-mechanical coupling environment is expanded, the effects of high temperature and temperature stress on the structure of the gradient lattice were analyzed. The influence of the gradient mode on the bending strength after being subjected to high temperature is studied. |
PDF Full Text Request