Microstructural Simulation of Mechanical Behaviour of porous CMC matrices by means of a parametric Unit Cell Approach

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. In this class of materials, damage evolution initiates on the microscale in the matrix component, and interacts with damage processes on subsequent length scales in a complex manner. To study the influence of changes in matrix porosity or particle diameter on the microscopic 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. This 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 experimental data. To validate the numerical model, mechanical tests on small specimens of porous matrix material and microscopic investigations have been performed