The design and implementation of a friction test apparatus based on the thermostamping process of woven-fabric composites

The effects of processing parameters on the friction coefficient between woven-fabric composites and the steel tool during the thermostamping process were studied.; During the thermostamping process, fabric in-plane forces are developed as a result of the friction between the fabric and tool, and controlling these in-plane forces is important to the manufacture of quality parts while achieving efficient manufacturing cycle times. A test apparatus was designed for measuring both the static and dynamic coefficients of friction. Based on this research, the coefficient of friction was found to increase with increasing velocity and decreasing normal force. The tool-temperature results suggest that a tool temperature where the friction between the tool and fabric is minimized exists in the room temperature to 140°C range. The tool temperature was found to lower the fabric temperature significantly upon contact such that the resin layer is a quasi-solid rather than a fluid under the binder plate during thermostamping. The static coefficient of friction measured with a force-control method was typically lower than the coefficient measured with a position-control method. Processing parameters such as fabric temperature coming out of the oven, sample transfer time, and rate of normal-force application influence the degree of consolidation. An alternate test method was explored that includes an isothermal condition between the fabric and tool. The importance of boundary conditions is discussed.