An experiment-modeling integrated approach to characterize friction between composites prepregs during preforming

During preforming of carbon fabric prepregs, multiple layers of composites will be deformed into parts with 3D geometry. Large relative sliding between different prepreg layers, especially when these layers have various initial stacking orientations, will significantly influence deformation of the prepregs and reorientation of the reinforcement yarns, greatly affecting performance of the final parts. However, it is challenging to correctly identify local environmental conditions, which can substantially change friction between prepregs, during preforming in closed molds. To tackle this issue, an innovative experiment-modeling integrated approach has been developed to iteratively characterize friction between prepregs under non-uniform conditions throughout the entire prepreg region and preforming process. This integrated characterization approach was supported by a self-developed tester to measure the coefficients of friction (CoFs) between prepregs under target preforming conditions, and a variable friction model with experimental data directly implemented using the bilinear Lagrange interpolation for finite element analysis (FEA) of preforming. Comparison between experimental and numerical modeling results regarding geometry and yarn angles of the single-dome benchmark samples from preforming indicates that the experiment-modeling integrated approach, supported by the reliable friction tester and the variable friction model, can effectively determine the complex friction conditions between prepregs during preforming, greatly improving accuracy of the process modeling at the end.