Time-dependent wrinkle formation during tow steering in automated fiber placement

Abstract

Out-of-plane buckling at the inside edge of prepreg tows during steering is one of the major drawbacks of the Automated Fiber Placement (AFP) process, limiting the process application and further optimization of the composite layup. This wrinkle formation is significantly influenced by prepreg tack, which is a property of the viscoelastic prepreg-tool interface. In this paper, an experimental AFP study is performed to gain a deeper understanding of the time-dependent growth of wrinkles. Furthermore, a theoretical model accounting for the viscoelastic properties of the interface is presented. For this purpose, a time-dependent buckling model for an orthotropic plate resting on a generalized viscoelastic Pasternak foundation which is subjected to an in-plane loading is developed. Closed-form solutions for the problem representing individual wrinkles are derived. It is shown that the model can capture the growth of wrinkles with time. Finally, important practical implications of the model are discussed.