Characterization of Fatigue Damage in a Metal Matrix Composite (SCS-6/ TI-15-3) at Elevated Temperature

The fatigue characteristics of a unidirectional titanium based metal matrix composite (MMC) were investigated at elevated temperature (427°C). A hybrid strain controlled loading mode was used to subject the 0° and 90° laminas to fatigue. Along with the fatigue tests, microscopy and analytical modeling ware also conducted. This combination of activities led to defining the initiation and progression of damage and deformation in the MMC. Hen loading was parallel to the fiber on, the fatigue behavior was initially dominated by creep deformation of the matrix. Then, depending on the maximum strain, specimen failure was the result either fiber fractures or matrix cracking. In contrast, when loading was perpendicular to fiber direction, the fatigue response was first dominated by the initiation of fiber-matrix interface damage. Then, if the maximum strain was above .35%, the dominant damage mechanism was matrix cracking. Below this strain level, the damage was a mixture of matrix microcracks and the progression of fiber-matrix interface damage. The analysis for this fiber orientation included unique methods to model the interface damage. This hybrid approach involving experiments, microscopy, and analytical modeling provided better understanding of the fatigue behavior of the MMC