Closed-loop flow control approaches for VARTM

VARTM (Vacuum Assisted Resin Transfer Molding) is a liquid composites manufacturing process that offers numerous advantages over other processes because of the low tooling costs and the manufacturing benefits for large structures. During the infusion of resin into a closed mold that contains a preform in VARTM process, resin flow is often affected by the inherent variations in permeability resulting from the part design as well as the variability associated with the mold lay-up. Current injection methods used for VARTM provide; very limited control of the resin flow within the mold: this can result in part defects including dry (unfilled) regions and voids. A definite need exists to continue to improve the part quality especially to eliminate the dry spots and voids. Improved control of resin flow appears possible with several approaches including the development of a multi-segment resin injection line that provides real time modifications to the resin flow front.; The overall goal of this study is to demonstrate practical control strategies for VARTM that provide control of the resin flow within the mold. The potential benefits of this capability are significant. Control of the flow will reduce the presence of voids in finished parts thus decreasing the number of rejected parts. Current manufacturing methods minimize void formation by extending the injection time to promote full mold infusion; better control of the resin flow will reduce the need for extended infusion times thus increasing production efficiency. (Abstract shortened by UMI.)...