Multi-scale analysis of mechanical properties and failure behavior of SiCf/Ti composite thin-walled tubes under compression loading

SiC_f/Ti composite thin-walled tubes exhibit a variety of fracture modes due to their complex structures and intricate manufacturing process, limiting their application. Specifically, accurate prediction of failure behavior is crucial for improving the performance of SiC_f/Ti composite thin-walled tubes. In this study, a generic multi-scale analytical model was established to evaluate the mechanical properties and failure behavior of SiC_f/Ti composite thin-walled tubes under uniaxial compression, and damage evolution and stress distribution at two scales were analyzed. At the macroscopic level, a three-dimensional Hashin-based orthotropic damage model was implemented through a user-defined subroutine (VUMAT), including damage initiation, stiffness degradation, and constitutive relationships. At the mesoscopic level, three mesoscopic models of different fiber distributions were developed based on random sequential addition (RSA) algorithm and representative volume element (RVE), and the mechanical behavior of the fiber/matrix interface was characterized by cohesive zone model (CZM). Subsequently, the nodal displacement of the macroscopic model was imposed on the mesoscopic model as the boundary condition, forming a strong coupling relationship at different scales. Furthermore, the influence of interfacial modeling approach on the buckling behavior and mechanical properties was particularly considered, and the interactions among capsule yield strength, capsule thickness, and fiber distribution were also integrated to discuss their effects on the damage evolution and stress distribution of SiC_f/Ti composite thin-walled tubes. The results indicate that the multi-scale model can accurately capture the crack initiation, propagation and failure in SiC_f/Ti composite thin-walled tubes. Moreover, the overall strength of SiC_f/Ti composite thin-walled tubes can be significantly improved as the capsule strength increases or the outer capsule thickness increases. Notably, the stress variation along the axial direction of the composite core is similar to that of the inner capsule, while the outer capsule exhibits an opposite stress trend. The multi-scale method proposed in this work provides a fresh perspective for the design of SiC_f/Ti composites thin-walled tubes.