Curing and Consolidation of Advanced Thermoset Composite Laminate Parts by Pressing Between a Heated Mold and Customized Rubber-Faced Mold

Abstract

Curing and consolidating thermoset composite laminates and sandwich structures typically involves vacuum bagging an uncured and formed layup over a thin-walled mold, placing it in an autoclave, and subjecting the entire unit to temperature, vacuum, and pressure cycles as prescribed by the manufacturer. Autoclaving is generally considered the major bottleneck in manufacturing advanced composite parts because of high capital and consumable costs, energy usage, waste generated, and process scalability. A new curing and consolidation process called “thermal press curing” is presented and demonstrated as an alternative to autoclaving. The process involves compressing a composite laminate between a special mold set––a heated metal mold and a matching rubber-covered mold made of an insulative material––designed to provide uniform temperature and pressure over the metal mold surface, that is, mimic the process conditions provided by an autoclave. The thermal press curing process is demonstrated for the first time using a mold set for a simple two-dimensional axisymmetric shape. An aluminum curing mold with embedded electric resistance cartridge heaters is heuristically designed to provide uniform temperature in operation across the mold surface within 1°C of the target value (177°C). With the mold set compressing an eight-ply carbon/epoxy composite workpiece and well insulated on all sides, the power draw is at least one to two orders of magnitude less than a comparable autoclaving operation. The potential to significantly improve pressure uniformity from the compressed rubber mask is shown by changing the mask shape. Even without an optimized rubber layer shape and thickness, the eight-ply composite part was successfully cured. Finally, a plan for future work is described.