Dynamic Fracture Mechanical Behavior Of ZrB₂-SiC Ceramic Composites

In order to expand the application of ultra-high temperature ceramic composites in aerospace,this paper uses a combination of experimental testing,numerical simulation and theoretical analysis to study the dynamic fracture mechanics behavior and failure mechanism of ultra-high temperature ceramic composites.The dynamic fracture test of ZrB₂-SiC ceramic materials under different loading rates was carried out with a separate Hopkinson pressure bar.The correlation between the dynamic fracture toughness of ceramic materials and the loading rate was discussed,and the influence of loading rate on dynamic fracture toughness was revealed.The dynamic failure model of ceramic composites is established,combined with the dynamic constitutive model,to realize the prediction of fracture toughness and fracture strength of ultra-high temperature ceramic composites.The ANSYS finite element software was used to simulate the dynamic failure process of ultra-high temperature ceramic unilateral notched beam specimens,and the failure mechanism of the specimens under different loading rates was analyzed.（1）Carry out the dynamic fracture toughness test of ZrB₂-SiC ceramic material,reveal the influence of loading rate on the dynamic fracture toughness,energy time history curve and failure mode of ultra-high temperature ceramic composite materials.The test results show that the fracture behavior of ZrB₂-SiC ceramic material has obvious rate effect.（2）Based on the maximum principal stress criterion,a dynamic failure criterion is established,combined with a dynamic constitutive model,and the prediction of the dynamic fracture behavior of ZrB₂-SiC ceramics is carried out.The numerical prediction results of the dynamic stress intensity factor are in good agreement with the experimental results.The dynamic fracture strength and failure strain of ZrB₂-SiC ceramic composites can be predicted by the method in this paper.（3）High-speed photography was used to record the dynamic failure process of ceramic samples,the failure modes of ultra-high temperature ceramic samples under different loading rates were analyzed,and the dynamic failure mechanism of ultra-high temperature ceramics was revealed.（4）The JH-2 modified model was used to reconstruct the dynamic fracture process of ceramic samples at ultra-high temperature.Extract the numerical simulation results of the first principal stress and the maximum principal strain nephogram and high-speed photography record of failure process were analyzed,the results show that the results of numerical simulation and experimental results is good,in combination with dynamic failure criterion and JH-2 model can effectively reconstruct ultra high temperature ceramic in the process of high speed impact failure pattern.