Damage Accumulation Process in Advanced Metal Matrix Composite Under Thermal Cycling

This research was intended the second stage of thermal cycling damage in metal matrix composites where progressive dimensional change along the fiber is observed. This dimensional change was documented by SEM-image analysis technique in terms of damage area distribution along the matrix-fiber interface. The progressive dimensional change was then predicted by using elasticplastic creep analytical model, resulting in a good agreement. Based on the analytical study, we designed a new type of MMC which possesses higher thermal cycling resistance and where additional short fibers are embedded in the matrix to make a MMC hybrid MMC. It was found that the main mechanisms for higher thermal cycling resistance in the hybrid MMC are 1 The apparent CTE of the matrix modified with additional short fibers is closer to that of the main fibers, resulting in smaller CTE mismatch, which would be a weaker driving force for thermal cycling damage. 2 Additional short fibers in the matrix give rise to higher density of dislocations which are punched out from the interface between the matrix and these short fibers, enhancing the in-situ mechanical properties of the matrix. Damage Accumulation in Thermal-Cycled Metal Matrix Matrix Composites Experimental and Analytical Studies.