Dynamic Tensile Mechanical Properties Of Ultra-high Temperature Ceramic Composites

Ultra high temperature ceramics have a series of excellent properties,such as high melting point,high hardness,good oxidation resistance and thermal stability,and become the preferred materials for the key parts of hypersonic vehicles.However,under the service environment of aircraft,it will be affected by the aerodynamic load,and the lower tensile strength is the main limiting factor for the application of ultra-high temperature ceramics,which directly affects the failure of this kind of material components.Therefore,the dynamic tensile mechanical behavior of ultra-high temperature ceramic composites is particularly important.Firstly,the applicability of JC constitutive model to simulate the dynamic behavior of ZrB₂-SiC ultra-high temperature ceramic material is verified by using the dynamic splitting tensile test data.Based on JC constitutive model,the design of direct drawing specimen and fixture is carried out,and various types of specimens are selected to ensure that the tensile force is uniform and there is no obvious stress concentration,which meets the requirements of dynamic tensile test.Secondly,through the pre-test to find the shortcomings of the design sample,improve the test scheme,based on the analysis of the difficulties and improvement direction,simultaneously improve the design of the collet and sample,ensure the feasibility of the test scheme.Then,the dynamic tensile test is carried out to study the influence of strain rate on the tensile strength,dynamic stress with time and failure mode.The results show that the dynamic strength factor increases exponentially with the increase of strain rate in the range of 1/1000s^-1to 150s^-1,and there is an obvious strain rate effect,The effect of strain rate on dynamic tensile strength is not obvious.With the increase of strain rate,it is found that the failure area does not increase significantly and the fragment size does not decrease significantly.Finally,the JC constitutive model is used to predict the dynamic mechanical behavior of the material.Through the analysis of JC model,it is found that the simulation results of JC model are close to the experimental results,and the prediction results of JC model are reliable and predictable.