Experimental and Theoretical Analysis of Pulling Force in Pultrusion and Resin Injection Pultrusion (RIP)–Part I: Experimental

Pulling force is the summation of resistance forces along a pultrusion die. Its mechanism is complicated because the impregnated resin inside the compressed fiber reinforcement changes from a liquid to a gel, and finally to a solid in the die. Two methods, a ‘mat tracer’method and a ‘short die length’ method, were used to determine the pulling force distribution. Results show that the downstream part of the die contributes little to the pulling force. In order to predict the resistance force in both the injection die and the heating die, two models were developed in this study. A friction measurement device was designed to measure the friction coefficient between the composite and the mold surface. The effect of process variables, such as temperature, resin conversion, normal force, and line speed, on the friction coefficient was investigated and a friction coefficient model was proposed based on the experimental results. A volume change model of vinylester resin was also developed to predict the thermal expansion–polymerization shrinkage during curing. The parameters of the model were determined by dilatometry, thermomechanical analysis (TMA) and differential scanning calorimetry (DSC).