Hierarchic multi scale analysis of porous matrix CMCs

Abstract

Wound highly porous oxide ceramic matrix composites (WHIPOX®), manufactured by German Aerospace Center in Cologne, consist of oxide fibres, embedded in an oxide matrix. WHIPOX® applies the concept of a highly porous matrix to achieve weak fibre-matrix bonding and macroscopic non-brittle, damage tolerant behaviour under mechanical loading. WHIPOX® components are fabricated using an automated process, during which a continuous fibre roving is infiltrated with ceramic slurry and wound on a rotating mandrel. To study the influence of processing-induced changes in the microstructure (matrix porosity and diameter distribution of the sintered matrix particles) on the mechanical properties, a unit cell approach has been chosen. Based on comprehensive microstructure analyses, the unit cells are generated parametrically by means of a random sequential addition algorithm that randomly places spherical matrix particles inside a bounding box. A cubic grid-based meshing algorithm facilitates the numerical simulation of the mechanical behaviour of virtual matrix microstructures under different loading conditions via the finite element method. The simulation results are compared with analytical bounds and predictions obtained by mean field and self-consistent methods.