This research focuses on the friction mechanism at the tool/fabric interface during thermostamping of commingled glass-polypropylene plain-weave fabric composites (TwintexRTM). The results of these investigations contribute directly to the development of a design tool for manufacturers using these materials. More specifically, the effects of processing parameters on the friction coefficient between the fabric and the steel tool during thermostamping processes are under investigation. This work focuses on the effect of fiber orientation, fabric velocity, normal force and resin viscosity (through variations in tool- and fabric-temperature) under conditions similar to those in thermostamping processes. Based on this research, velocity, normal pressure and tool temperature have the greatest effect on the friction coefficient. The effect of tool temperature on the friction coefficient was much more significant than the effect of initial fabric temperature on the friction coefficient. A phenomenological friction model was derived from the noted effect of these processing parameters on the friction coefficient. This friction model was incorporated into the commercial finite element code ABAQUS/Standard as a user-supplied friction subroutine. This friction model was first used in a finite element model of the friction test. Agreement was found between the experimentally measured friction force and the numerically calculated friction force. Two parametric studies were completed using the fabric-friction model with a finite element model of the thermostamping process. These parametric studies were conducted to investigate the effect of changing the binder-ring force and the punch velocity on the reaction force on the punch during the thermostamping process. Punch velocity has a much greater effect on the reaction force on the punch than binder-ring force.
展开▼
