Micromechanical analysis of crack closure mechanism for intelligent material containing TiNi fibers - (1st report, modeling of crack closure mechanism and analysis of stress intensity factor)

Micromechanical modeling of an intelligent material containing TiNi fibers is performed by taking into consideration the existence of crack-bridging fibers given a tensile transformation strain. The total amount of shape memory shrinkage of the fiber corresponds to the transformation strain and this shrinkage strain is replaced with the eigenstrain of the fiber. Moreover, the thermal expansion strain due to the mismatch between the thermal expansion coefficients of a fiber and a matrix is also considered in the model. By analyzing the model, stress and strain fields in the composite, the total potential energy of the system is derived. Moreover, from the resultant total potential energy, the stress intensity factor at the tip of a crack in the composite is derived and expressed successfully in terms of the shrinkage strain of fibers and the thermal expansion strain in the material.