Developing a hybrid Al–SiC-graphite functionally graded composite material for optimum composition and mechanical properties

A systematic methodology for developing hybrid Al–SiC-graphite functionally graded composite materials with the highest feasible SiC-content in the top-most layer, without resulting in residual porosities, has been established. The distribution of ceramic reinforcements in individual layers is very homogeneous, and the interlayer regions are free from any defect. Monolithic composites, having composition identical to the overall average compositions of the FGMs, were also fabricated, and their mechanical properties were compared with the corresponding FGM properties. Due to the locally high SiC-content, the top-layer hardness of the FGM is significantly higher than the corresponding monolithic composite. A systematic study of the flexural stress-strain behavior of individual mono-layers and the overall FGM was carried out at different orientations. For identical mono-layer compositions, the orientation of the FGM has a strong influence on its flexural stress-strain behavior. The failure stress is significantly higher when the layer containing high SiC-content is at the compressively loaded side during the 4-point bend test.