Abstract: Based on three-dimensional (3D) progressive damage theory, a stiffness degradation method is proposed to predict the progressive failure properties of 3D composite flywheel rotor, and the correctness of this method is proved by comparing with existing references. Four failure modes are included, Fiber breakage, matrix cracking, delamination and fiber-matrix shear failure. The Newton-Rapson nonlinear iterative algorithm of finite method is developed to perform the 3D progressive failure analysis. The failure analysis and comparisons are all performed when winding prestress are different. The results show that the failure first appears at the middle of composite flywheel, and the failure process includes：Matrix cracking first, and with the rotating speed increasing, the fiber breakage causes the burst failure at the outer radius of the composite flywheel. Besides, the filament tension winding process can increase the initial failure speed of flywheel. There is no delamination and shear failure in this process.

Key words: Composite flywheel, Finite element method, Three-dimensional progressive damage, Winding prestress