ABSTRACT Copper (Cu)‐polyethylene terephthalate (PET)‐Cu composite films are widely used in energy storage devices, such as lithium‐ion batteries. During the winding process of these composite films, the stress distribution within wound rolls directly affects their winding quality. Here, the mechanical behavior of Cu‐PET‐Cu composite film during the winding process is systematically analyzed through a combination of theoretical modeling, experiments, and finite element (FE) simulations. Based on the thick‐walled cylinder theory, a theoretical model is established to achieve analytical expressions for radial and circumferential stresses. Winding experiments are then designed to measure the stress distribution, and the results show good agreement with those obtained by the theoretical model and FE simulations. It is observed that the von Mises stress, radial stress, and circumferential stress of composite films all decrease from the inner layers to outer ones and increase with increasing winding tension. Additionally, increasing the thickness of the PET layer effectively reduces the overall stress and enhances the uniformity of stress distribution. Notably, the stress concentration and interlayer slippage of wound rolls are also investigated in detail. This study provides a systematic analysis of stress characteristics of the Cu‐PET‐Cu composite film, offering valuable support for optimizing the winding process and improving product quality.
Yang et al. (2026) studied this question.