Institute of Fundamental Technological Research

Gradual degradation of brittle composites exhibits different mechanical responses under uniaxial tension and uniaxial compression. In this paper, we analysed cracking processes and failure under quasi-static loading of a two-phase ceramic material made of an Al2O3 and ZrO2 mixture subjected to tension and compression. Constitutive modelling of two-phase ceramic composites obeys the description of: (1) elastic deformations of initially porous material, (2) limited plasticity and (3) cracks initiation and propagation.

Modelling of polycrystalline ceramics at the mesoscopic level under mechanical loading is related to the analysis of a set of grains, i.e. Representative Volume Element (RVE), Fig. 2. The basic elements ofthe defect structure inside a polycrystal are: micro- andmesocracks, kinked and wing cracks. To obtain a macroscopic response of the material, one can calculate averaged values of stress and strain over the RVE using an analytical approach.

High-strain-rate degradation process was illustrated for Al2O3/ZrO2 composite, which was subjected to a short compressive impulse. The pulse duration was 10- 7s, Fig. 3. In the proposed more advanced finite elements formulation, it was necessary to take into account the following data and phenomena appearing inside of the RVE: (1) spatial distribution of the composite constituents, (2) system of grain boundaries/binder interfaces modelled by interface elements, (3) rotation of brittle grains.

In the proposed more advanced finite elements formulation, it was necessary to take into account the following data and phenomena appearing inside of the RVE: (1) spatial distribution of the composite constituents, (2) system of grain boundaries/binder interfaces modelled byinterface elements, (3)
rotation of brittle grains.

impact, experiments, SHPB, numerical model

The paper presents modelling and experimental testing of non-linear degradation processes developing in the two-phase ceramic matrix (CMCs) and metal matrix composites (MMCs) subjected to quasi-static and dynamic compressive loading. Modelling was performed by a multiscale approach using both: (1) analytical and (2) numerical methods and selected Representative Volume Elements (RVE) based on SEM observations of composites. Both quasi-static and dynamic experimental tests were done applying standard MTS (100 kN) servo-hydraulic machine and Split Hopkinson Pressure Bar (SHPB) stand for impact tests with loading velocities 20 – 30 m/s. As a result, we observed for CMCs in quasi-static loading failure mode by splitting of cylindrical samples, whereas for impact loading dynamic crushing process took place.

metal-matrix composites, dynamic testing, Split Hopkinson Pressure Bar, peridynamics