An elastic film peeled from a semi-circular shaft in the circumferential direction

Although the peeling behavior of thin films on flat substrates is extensively investigated, the mechanisms governing film peeling on curved substrates remain insufficiently understood. This work presents a theoretical model for the full-process peeling of an elastic film/curved-substrate system with the interface considering the mixed-mode toughness. A comprehensive parametric study is carried out to examine the effects of key factors, including peeling angle, film bending stiffness, initial cantilever length, and substrate radius, on the variation of peeling force throughout the entire process for conditions of films with/without pre-strain. Complementary analyses of energy variations and interfacial failure mode transitions further elucidate the underlying mechanisms. The findings reveal that the peeling force exhibits a distinct two-stage behavior that it first decreases and then increases. Different influencing factors affect the peeling force at different stages. Specifically, the bending stiffness and substrate radius significantly affect the peeling force throughout the entire process; whereas the initial cantilever length and peeling angle primarily influence the early stage; in contrast, the ratio of Mode I to Mode II interfacial fracture toughness predominantly impacts the later stage. Moreover, the introduction of initial pre-strain generally reduces the full-process peeling force. However, due to the competing effects between pre-strain and other factors (i.e. bending stiffness of the film), the variations in initial and terminal peeling force exhibit complex nonlinear relationships with these factors. Overall, our findings enhance the fundamental understanding of peeling mechanisms in film-substrate systems with complex interfacial geometries and offer theoretical guidance for the interfacial design of such structures.