INVESTIGATION ON FATIGUE HYSTERESIS LOOPS MODELS OF FIBRE-REINFORCED CERAMIC-MATRIX COMPOSITES

When the fibre-reinforced ceramic-matrix composites (CMCs) are first loading to the fatigue peak stress, the matrix cracking and fibre/matrix interface debonding occur. Under the fatigue loading, the stress-strain hysteresis loops appear due to the fibre sliding relative to matrix in the fiber/matrix interface debonded region. The micromechanical hysteresis loops models for the fibre-reinforced CMCs have been developed in present analysis. The fibre/matrix interface debonded length upon first loading, the unloading interface counter-slip length and the reloading interface new slip length were determined by the fracture mechanics approach. The hysteresis loops of four different interface slip cases have been analysed. By assuming that the mechanical hysteresis behavior of cross-ply and woven CMCs was mainly controlled by the fiber/matrix interface slip in the 0o ply or the longitudinal yarns, the hysteresis loops of unidirectional, cross-ply and woven CMCs corresponding to different peak stresses and different cycles have been predicted, respectively. The predicted results agreed with the experimental data.