Study On A Meso-mechanical Model Considering Fiber Creep For Modeling The Creep Of CMCs In High Temperature

Braided SiCf/SiC ceramic matrix composites,as an important application material for the hot end parts of aero-engine,are prone to creep in long-term high temperature service environment,which has an important influence on the service life of the engine.In this paper,the high temperature creep properties of SiCf/SiC mini-composites,which can be used as a yarn of a braided material,are studied.In order to eliminate the influence of oxygen on the properties of materials at high temperature,a new device suitable for high temperature testing of SiCf/SiC mini-composites was built in this paper,and the creep strain-time curve of SiCf/SiC mini-composites was tested under the environment of inert gas protection at 1400 ?.The types of mini-composites used include SiC/PyC/SiC mini-composites and SiC/PyC+SiC/SiC mini-composites.The test results show that when the SiCf/SiC mini-composites under the atmosphere of inert gas protection at 1400 ? are tested for creep,the two kinds of materials can show the characteristics of deceleration creep stage under proper load,creep fracture is more likely to occur when the load is large.For the test pieces with creep fracture,the creep fracture of SiC/PyC/SiC mini-composites under 12 kg weight loading at 1400 ? shows brittle fracture characteristics,while the creep fracture of SiC/PyC+SiC/SiC mini-composites under 24 kg weight loading at 1400 ? is uneven,present "pull out" shape.In order to further study the high temperature creep law of SiCf/SiC mini-composites,a meso-mechanical model of high temperature creep of SiCf/SiC mini-composites considering component creep is established in this paper,which is combined with the matrix cracking,interface debonding,fiber fracture and other failure mechanisms of SiCf/SiC mini-composites at the same time,and finally output the creep strain-time curve of SiCf/SiC mini-composites.By comparing the output curve of the model with the test data,it is proved that the model has the ability to describe the variation of high temperature creep strain of SiCf/SiC mini-composites with time,and it is feasible.