Automation of Autoclave Cure of Graphite-Epoxy Composites

Abstract

Techniques were developed for control and automation of autoclave cure of graphite-epoxy composites. Heat conduction dynamics of the system were determined on-line before the reaction exotherm began. System parameters were then used for tuning the controller and for developing bounded setpoint temperature profiles for control action. The advantage of this bounded control is the definition of an envelope for cure temperature trajectory that can provide improved process guidance and control compared to on-off automation techniques. Different strategies based on predictive action and early reheating were used to maintain the laminate's temperature so that cure could be carried out in mini mum time without a thermal runaway. Reheating strategies, such as employing a dual heat flux sensor combined with the dimensionless Damkohler number, were used to quickly drive the cure reaction to completion. The automation techniques achieve a balance in avoiding thermal runaway while reducing cure cycle time.