Analysis of failure mechanisms for CFRP laminated composite bogie frames of the next generation high-speed trains under service environment

Carbon fiber reinforced polymer (CFRP) laminated composites are gradually adopted in next-generation high-speed train bogie frames due to their superior mechanical properties. However, the failure behavior of CFRP structures under service conditions remains insufficiently understood. To address this, a progressive fatigue damage method based on element-level analysis is employed and integrated into a novel rigid–flexible coupled high-speed train model incorporating CFRP laminated bogie frames. In particular, the model established here enables real-time updates of material stiffness, strength, and governing equations in the degradation progresses based on the finite element method (FEM) and the floating frame of reference, making it particularly well-suited for analyzing the failure behavior of CFRP laminated bogie frame under service conditions. Numerical results indicate that under the excitation of track irregularity, there are three main failure modes of the bogie frame during high-speed train operation (running 100 kilometers on a straight track with a constant speed 300 km/h), i.e., matrix tensile failure (FM3), matrix compression failure (FM4), and tensile delamination (FM5). Specifically, FM3 occurs when the $E_{12}$ is reduced by approximately 46%–48%, FM4 is triggered with a 21%–23% reduction in $E_{12}$, and FM5 is associated with a reduction of interlaminar tensile strength ($S_{3t}$) by about 85%–87%. These findings may offer practical design guidance. Among others, symmetric ±45°ply orientations should be incorporated in shear-critical regions, such as the curved areas of the side beam, to enhance shear stiffness and delay matrix-dominated failure. Additionally, localized reinforcements, such as applying interlayer resin near the suspension areas, can help mitigate delamination risk. The numerical strategy provides a robust foundation for fatigue prediction, optimization, and the development of damage-tolerant designs for CFRP bogie frames in high-speed rail applications.