Effect of stochastic brittle fragmentations on cyclic loading/unloading hysteresis behavior of fiber-reinforced ceramic-matrix composites

Under monotonic tensile and cyclic tensile loading, the occurrence of stochastic brittle fragmentations will affect monotonic and cyclic loading/unloading mechanical behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this work, synergistic effects of stochastic brittle matrix and fiber fragmentations on monotonic and cyclic loading/unloading hysteresis behavior of fiber-reinforced CMCs were investigated. Different matrix fragmentation lengths and distributions of stresses between intact and broken fibers were determined using stochastic fragmentation models, taking into account cyclic loading/unloading hysteresis constitutive relationships. Experimental monotonic tensile and hysteresis curves, matrix fragmentation density, and fiber fragmentation probability for two different SiC/SiC minicomposites were forecasted. Theoretical tensile curves and loading/unloading hysteresis loops for different peak stresses agreed well with the actual data collected. Interface slip is constrained by the debonding of the interface for long matrix brittle fragmentation (LMBF) length and the fragmentation length of the matrix for short matrix brittle fragmentation (SMBF) length. The impacts of fiber volume fraction and fiber's strength on monotonic and cyclic tensile loading/unloading hysteresis loops were analyzed. Fiber volume fraction increase resulted in increased proportional limit stress and tensile fractured strength and decreased tensile failure strain; in addition, the peak strain of hysteresis loops as well as valley strain and area decreased, with increased hysteresis loops modulus for different matrix fragmentations.