Accumulation of damage in the femoral component of the hip arthroplasty made of Carbon-Carbon composite material

The purpose of the study. Assessment of the quantitative accumulation of damage in the C/C composite and the effect of damage on the bearing capacity of the endoprosthesis during continuous loading. The need to assess the impact of damage on load-bearing capacity is due to the heterogeneous structure of the C/C composite. The reason for the inhomogeneity of the C/C composite is the pyrocarbon matrix, which is a stochastic medium at the level of the crystallite dimension. Due to the specific structure of the C/C composite, damage to the grains may occur under low loads caused by accidental circumstances during human movement. Damage to the grains leads to a change in elastic properties in the area of damage to the pyrocarbon matrix and C/C composite. Such changes lead to pseudoplastic deformation of the C/C composite product. Methods. The model for analyzing the effect of damage accumulation on the bearing capacity of the endoprosthesis, developed as part of the study, is a synthesis of two methodologically different models. The first level of the model is an algorithm that allows us to obtain solutions to the integral equation for deformations in polycrystal grains of pyrolytic carbon, determine the probabilities of damage to the matrix grains for each of the criteria, calculate the volume fractions of destroyed, partially damaged and undamaged crystallites, and determine the elastic properties of the pyrocarbon matrix at two scale levels within the framework of the generalized singular approximation and the polydisperse model. The second level is a finite element model of the femoral component of the hip arthroplasty, created in the ANSYS package. The second level model makes it possible to evaluate the effect of matrix damage at the dimensional level of crystallites on the macroscopic mechanical condition of the structure. The interconnection of the two-level model is ensured by the continuous exchange of data between the two levels. Result of investigation. A piecewise linear diagram demonstrating the nontrivial pseudoplastic nature of the C/С composite deformation. Conclusion. A two-level model of the femoral component of the hip joint endoprosthesis showed that the C/C composite exhibits subcritical pseudoplastic deformation, which indicates the survivability and positive mechanical response of the structure.