Study On Dynamic Splitting Tensile Properties Of Ultra-high Temperature Ceramic Composites

Ultra-high temperature composite ceramics possess good high temperature resistance and low density,and have been applied into key parts of aircrafts,such as nose cone and wing leading edge.Serious application environments require this material to overcome two problems of“high temperature”and“high speed”.Compared with mechanical behavior under static condition,dynamic mechanical behavior is more complicated.Until now,research on dynamic behavior is rare and dynamic fracture mechanism and process is inadequate.Therefore,it is significant to investigate dynamic splitting tensile behavior of ultra-high temperature composite ceramic.On the basis of above background,ZrB₂-SiC material is introduced and investigated by combining theoretical and numerical approached in this study.Firstly,dynamic splitting tensile properties of ultra-high temperature composite ceramics are measured and the validity of experimental test is verified.Dynamic splitting tensile properties are investigate,including dynamic splitting tensile strength,variation of dynamic stress with time as well as dynamic fracture mode and mechanism.Results show that with the increase of strain rate and loading rate,dynamic splitting tensile strength and peak value of stress increase,fragment size becomes smaller and fragment number is larger.Secondly,Based on the experimental results,the JH-2 constitutive model was modified by LS-DYNA finite element software to realize the dynamic mechanical properties of the material and the numerical simulation of the failure process.The dynamic mechanical behavior of ultra-high temperature ceramic composites was predicted.The results show that the JH-2 modified model can better predict the dynamic tensile strength of the material with the strain rate and the dynamic stress with time.Finally,The failure morphology of the material under different strain rates and the Leica scanning technique were used to observe the influence of the strain rate on the failure mode of the specimen,and the failure mechanism of the ultra-high temperature ceramic dynamic tension was revealed.The numerical simulation results of the JH-2 modified model were extracted.The stress cloud diagram in the stress analysis of the stress wave propagation law and the corresponding failure mode are compared with the damage process collected by the high-speed camera.The results show that the numerical prediction results in this paper agree well with the experimental results,further verifying the JH-2 modified model reliability.