Effect of contiguity on the mechanical behavior of co-continuous ceramic-metal composites

The mechanical behavior of co-continuous ceramic-metal composites was investigated. The composites were manufactured by molten metal infiltration into alumina preform. Aluminum and copper were used as metal phases and two types of co-continuous composites were obtained. A material processing technique was developed to achieve composites of varying contiguity. Analysis on optical micrographs of the composites was performed to calculate the contiguity of the spherical alumina phase. Quasi-static compression tests and spherical indentation tests were accomplished to study the mechanical properties of the composites. It was found that the contiguity significantly affects the nonlinear stress-strain behavior, whereas the effect on elastic property is relatively small. A new Representative Volume Element (RVE) was introduced to ensure continuous networks in both alumina and metal phases. Measured contiguity and volume fraction were used as parameters to determine the dimensions of RVE. Thermo-mechanical Finite Element Analysis (FEA) was performed on the proposed RVE, to predict the elastic-plastic behavior of the composites. Thermo-mechanical analysis results revealed that the contiguity also affects the thermal residual stress in co-continuous composite. The FEA-predicted nonlinear stress-strain curves were compared to experimental data. Good agreements were observed and it was found that the proposed RVE could be very effective to represent the contiguity and volume fraction.