Methodology of numerical modelling of mechanical properties of the porous heat-shielding material based on ceramic fibers

We propose a method to predict the compression strength and elastic modulus of high porous ceramics based on fibers or whiskers. The method is based on the direct numerical simulation of material microstructure using a finite element approach. The representative volume elements of material samples are created using the random algorithm taking into account the given sample size, fibers mean size and orientation and porosity volume fraction. The fiber structure is assumed to consist of long rods as fibers and short rods as links (contacts) between fibers. For the considered structures we proposed the formulation of the strength criterion, in accordance with which the destruction of the material occurs due to the failure of connections between the fibers. It is proposed to consider the ultimate strength of the fiber contacts as unknown model parameter. Its value should be determined using the fitting of the estimation results to the experimental data. Predicted values of effective stiffness and strength of material are based on the analysis of representative element stress state under mechanical pressure. In this paper, we studied the repeatability of the numerical calculations results for the same type of representative elements with the same average microstructural characteristics. The convergence of the effective properties values with the increasing of the fragments size is also studied. Test results of the mechanical properties modeling of fibrous materials with different porosity and fibers orientation are presented in this article.