Damage Constitutive Model Of C/SiC Based On Uncertainty Modeling Method

C/SiC composite has many excellent properties,such as low density,high temperature resistance,ablation resistance and wear resistance.It has become an indispensable material in the structural design of national defense and industrial fields,such as aerospace.Due to the manufacturing process,there are a lot of defects in the micro geometry.Under the external load,there are random micro defects in the material,which are dependent on the load,resulting in damage a nd degradation of the material.The material's macro mechanical properties are nonlinear,stress state sensitive and accompanied by obvious discrete characteristics.Aiming at the mechanical behavior characteristics of the above C/SiC composites,this paper mainly studies and develops the accurate constitutive model and uncertainty characterization method to realize the reliability design of structural analysis response.In this paper,two-dimensional braided C/SiC composite materials are taken as the research object.The strain of the specimen is obtained by two methods,i.e.sticking strain gauge and digital image technology.The mechanical nonlinear and discrete behavior characteristics of the material under simple and complex stress state are obtained.Based on the macro nonlinear constitutive model,the trend of material damage state and inelastic strain evolution under different stress states is simulated,and the goal of describing the nonlinear characteristics of material mechanical behavior is achieved.In order to realize the discrete characterization of mechanical behavior of C/SiC composites,the parameters in the process of initial performance and damage evolution of materials are set as uncertain parameters,and the change range of uncertain parameters is quantified by means of probability statistics.The stress-strain curves of materials under five different loads are simulated by the confirmed uncertainty modeling method of C/SiC composite materials,and compared with the real test data,it is verified that the material beh avior uncertainty characterization method established in this paper can reflect the phenomenon of material mechanical behavior dispersion in the testIn this paper,Gaussian process regression model is used to predict the confidence interval of the constitutive model fitted by data when interpolating inside and outside.The UMAT subroutine is written in FORTRAN language,and the error of constitutive model of ring frame structure under load is analyzed by ABAQUS software,which improves the confidence of st ructural analysis results.