Influence of heat transfer and curing on the quality of pultruded composites. I: Experimental

Blister formation, a major concern in pultrusion, has not been studied in detail. The objective of this study is to investigate the mechanism of blister formation and the effect of process variables such as die temperature, pulling speed, die length, and composite thickness on blister formation. Dies with different length and a stop-start method were used to investigate blister formation. The results show that for a given die and resin system, low temperature and a higher pulling speed lead to blister formation. Longer dies can prevent blister formation. Based on the experimental results, process windows for 4-mm-thick and 6-mm-thick composites are established for a vinyl ester resin. This study suggests that heater power input should be optimized in high-speed pultrusion.