Characterization of Inelastic Deformation During the Transverse Loading of Weakly-Bonded Unidirectional Metal Matrix Composites

A combined numerical and experimental analysis of a unidirectional titanium matrix composite (SCS-6/Timetal 21S) under a series of transverse loadings and unloadings is capable of separating the interfacial fiber-matrix bond strength into two distinct components: one associated with chemical bonding and the other with mechanical bonding. The influence of the mechanical bonding, which is the clamping due to the thermal residual stress state, is determined by finite element analysis with an imperfectly-bonded interface. The chemical bond strength is deduced by subtracting the mechanical bond strength component from the experimental response. Combined numerical and experimental analyses were conducted at two temperatures. At 25°C, the initial inelastic deformation from fiber-matrix separation is controlled by the mechanical component of the bond which is much larger than the chemical component; however, at 650°C, it is controlled by the chemical component. The mechanical bond strength is very dependent on temperature, whereas the chemical bond strength is only weakly dependent on temperature. In addition, the transverse response of unidirectional SCS-6/Timetal 21S was numerically determined for a wide range of temperatures (25°C to 815°C) and strain rates (8.33 × 10−4 1/s to 8.33 × 10−6 1/s) for both perfectly- and imperfectly-bonded cases.