Numerical Modeling of Interply Adhesion in Composite Forming of Viscous Discontinuous Thermoplastic Prepregs

“Quilted Stratum Process” (QSP®) is a new process developed by CETIM, Ecole Centrale de Nantes and their partners which is in the category of thermoplastic composite forming. Unlike the conventional thermoforming process, a QSP® preform stack consists of several discontinuous plies. Due to the inability of using the blank-holders in this process, these discontinuous patches can experience large sliding and/or rotation. Thus, the mechanisms occurring at ply-ply interfaces, especially the interply adhesion are important and should be considered in the process simulation. A penalty based, semi-empirical contact model is proposed and implemented in the industrial code of Altair RADIOSSTM in order to model interply adhesion. This model allows sliding of plies over long distance while providing a finite adhesive strength before delamination and it has resulted in a significant improvement in the prediction of the final positions and orientation of the discontinuous patches in QSP® simulation. The model requires minimal characterization making it suitable for industrial applications.