Characterization of inter-ply slipping behaviors in hot diaphragm preforming: Experiments and modelling

Understanding the inter-ply slipping behaviors of uncured prepregs is fundamental for avoiding defects such as wrinkling during manufacturing of large-scale composite parts in hot diaphragm forming. This work investigates the inter-ply slipping behaviors in hot diaphragm preforming of carbon fiber/epoxy prepregs. A home-made testing system is used to characterize the inter-ply slipping behaviors of prepreg/prepreg, prepreg/release film and release film/diaphragm, respectively, with considering the effects of temperature, normal pressure and pulling rate. Based on testing results, a phenomenological three-stage analytical model is proposed to characterize the inter-ply slipping behaviors of prepreg/prepreg. For prepreg/release film and release film/diaphragm, a traditional Coulomb model is assumed and its static and dynamic friction coefficients are obtained by matching corresponding experimental data. The characterization of the inter-ply slipping properties is vital for numerical simulation and process optimization of the hot diaphragm preforming.