Characterization of the tool/fabric and fabric/fabric friction for woven-fabric composites during the thermostamping process

The dynamic coefficients of friction for Twintex® commingled glass-polypropylene balanced plain-weave and unbalanced twill-weave fabrics at the tool/fabric and fabric/fabric interfaces during the composite thermostamping process are characterized. The effects of fabric velocity and pressure on the coefficients of friction under conditions similar to those during the thermostamping process are studied. A phenomenological friction model accounting for pressure and velocity dependence is developed based on the experimental results and implemented into the commercial finite element codes ABAQUS/Explicit and LS-DYNA via user-defined subroutines. The mechanical behavior of the fabric is modeled using a mesoscopic approach. The friction subroutines are validated with a finite element model of the experimental friction test. The forming of a hemispherical dome is simulated using ABAQUS and LS-DYNA. Punch forces and yarn stresses are compared between variable friction and constant friction models, and the simulation results justify the necessity for a variable friction model to accurately predict part quality.