Research On Fatigue Behavior Of2.5D Woven Ceramic Matrix Composites

2.5D woven ceramic matrix composites not only possess high strength and modulus at elevatedtemperature, but also are a promising way to improve the interlaminar fracture toughness and damagetolerance. They are becoming the excellent choice of component with one end hermetical, and will bewidely used in astronautics fields. To make sure the reliable use of ceramic composites on actualcomponents, it is necessary to perform the investigation on the fatigue behavior of2.5D wovenceramic composites. In this paper, the fatigue hysteresis behavior and life prediction of the ceramiccomposites were investigated.The uniaxial tensile experiments and tensile-tensile fatigue experiments of2.5D woven C/SiCceramic composites at ambient and800℃in air environment have been performed. The mechanicalbehavior and damage mechanisms under tensile and fatigue loading were determined.An approach to predict the fatigue hysteresis loops of2.5D woven ceramic matrix compositesbased on the dual-scale model has been proposed. The dual-scale model was micro-scale model whichconsidered the scale of fiber/matrix/pore and meso-scale model which considered the scale of warp/weft/cavity. The stress-strain curve in meso-scale was gotten by calculating the mechanicsproperties in micro-scale, diminishing the elastic modulus of elements and calculating the averagestress and strain with the periodic boundary conditions. The hysteresis loops of2.5D woven ceramiccomposites were predicted. The results agreed well with the experimental datas at ambientenvironment. Besides, influences of fatigue load, micro-parameters and unit cell structural parameterson the fatigue loops of the composites were analyzed.An approach to predict the fatigue life of2.5D woven ceramic matrix composites based on thedual-scale model has been proposed. By combining the fiber statistical failure model with theinterface shear degradation model, fiber strength degradation model and the maximum strain failurecriterion, the failure process of the ceramic composites during fatigue loading was determined. TheS-N curves of2.5D-C/SiC ceramic composites were predicted. The results agreed well with theexperimental datas at room temperature. And the effect of Weibull modulus, steady shear stress, fiberelastic modulus and fiber volume fraction on the S-N curve was analyzed.