Influence of Alcohol Pre-Infusion on the Quality of VARTM Composites

In the vacuum assisted resin transfer molding (VARTM) process, part-to-part variations such as the uncertainty in the permeability and race tracking phenomenon make it difficult to achieve consistent mold filling and ensure part quality of composites. Alcohol pre-infusion was presented in this study as a novel real-time monitoring and control approach for the flow process in the VARTM process, alcohol test fluid is infused before the actual resin infusion to locate the potential dry spots without using the large quantity of sensors. Then corresponding process control strategy is designed, such as opening the auxiliary gate at specific moment on those predicted dry spot locations to compensate flow defects. Moreover, alcohol can be easily removed by heat without changing the local permeability. The influence of alcohol pre-infusion on the quality of VARTM composites were investigated in this study. The mechanical tests were conducted to verify that the alcohol pre-infusion approach has no significant effect on composite properties because alcohol can be removed from fiber by heat and air flow. Specifically, DMA, TGA, and FTIR spectrum proved that negligible difference existed on the resin-fiber interface between the composites with or without alcohol pre-infusion. Finally, the microscopy results revealed a similar failure path in a resin matrix. TMA results also demonstrated similar dimension stability. This alcohol pre-infusion approach was effective when compared with computer simulation and could eliminate the occurrence of dry spots and voids without using sensors or data-acquisition system. The control schemes were shown in a case study to be capable of compensating the flow defects and achieving desired fill patterns in the face of permeability uncertainty. POLYM. COMPOS., 29:1310-1320, 2008. (C) 2008 Society of Plastics Engineers