Liquid Composite Molding: Experiments and Modeling

Richard S. Parnas
Polymers Division
National Institute of Standards & Technology
Gaithersburg, Maryland

Flow through porous media has been characterized in terms of both the Darcy permeability and the apparent permeability during unsaturated flow. Model relationships between porous structures and the permeability tensors have been constructed but much work remains to quantify the flow/structure relationship in a general sense. In addition to the flow behavior, chemical reactions and heat transfer are important in liquid composite molding, and an optical fiber sensor has been constructed to measure the progression of the chemistry deep within the porous preform during processing. The signal from the sensor is currently being incorporated into a high-level control algorithm designed to manipulate the set-points of base-level controllers in order to move the entire process towards optimal operation. The high-level controller algorithm consists of both off-line components and on-line components, and the on-line portion of the controller uses a digital process contour map of the feasible operating space to locate the actual process behavior relative to the optimum.