JEC COMPOSITES MAGAZINE - Issue #36 - October 2007 - 62

KNOW-HOW Process An advanced out-of-autoclave curing technology for prepregs and resin infusion Quickstep is an out-of-autoclave fibre-reinforced polymer composite (FRPC) curing technology that uses a heat transfer fluid (HTF) to precisely control heat and pressure on the uncured component during processing. Savings on process time, energy, and overall component manufacturing costs are key features of this technology. DALE BROSIUS, CHIEF OPERATING OFFICER AMERICAS & EUROPE QUICKSTEP TECHNOLOGIES JENS SCHLIMBACH, CHIEF EXECUTIVE OFFICER QUICKSTEP GMBH lthough autoclave processes are well established, the applied technologies to manufacture a composite component are very time consuming (long cure cycles) and capital expensive (machine and equipment costs, energy consumption, etc.). Due to the forecasted growth of fibre-reinforced polymer composites (FRPC) and the need for improved economics, it is advisable to use out-of-autoclave processes in combination with traditional prepregs or innovative preform-infusion techniques. The Quickstep process is one of the emerging out-of-autoclave technologies with potential for qualified FRPC manufacturing. Fig. 1: Schematic of Quickstep process unit volume capacity much greater than that of a gas, the heat transfer rate between the HTF and laminate is much higher than that achievable in an oven or autoclave. This allows rapid heating/cooling rates to be achieved and provides precise control of the resin viscosity, especially during the early consolidation phase of the cure. The high heat transfer rate allows a lower viscosity to be obtained in the laminate than that achievable with a slower autoclave heat-up rate (figure 2). Description of the Quickstep process The Quickstep process utilizes a fluid-heated, balanced-pressure floating mould for the curing, partial curing and joining of composite materials. The process works by rapidly applying heat to an uncured laminate stack that is moulded to a rigid (or semi-rigid) tool floating in a heat transfer fluid (HTF). The mould and laminate stack are separated from the circulating HTF by a flexible membrane. The temperature and pressure of the HTF behind the mould and flexible membrane are constant. The process uses vacuum, combined with optional vibration, to evacuate air and volatiles from the laminate as well as to compact, heat and cure the part. The laminate may be thermoset or thermoplastic prepreg, or a wet resin/dry fibre combination. Typically, parts manufactured using this process have equivalent, and in many instances, superior strength, stiffness, surface finish and appearance when compared to autoclave-cured components. The laminate stack is assembled on a single-sided tool, or within a double-sided one, using conventional lay-up. It is then sealed in a vacuum bag and installed in a low-pressure chamber containing a glycol-based HTF The tool and laminate are supported between two . flexible membranes in the curing chamber (figure 1). Temperature control is maintained by circulating the HTF through the curing chamber. As fluids have a heat energy per Fig. 2: Low viscosity due to rapid resin heating This is made possible by the laminate reaching consolidation dwell temperatures with reduced chemical cross-linking having occurred within the matrix. By achieving lower viscosities in the laminate, excellent consolidation is obtainable at low applied pressures, typically vacuum, plus 10 to 30 kPa externally from the fluid. The HTF also acts as a large thermal sink, removing any excess heat generated in a high-rate exothermic reaction, thus a constant cure temperature may more easily be maintained, even for thick laminates. The HTF is stored in three separate tanks - hot, medium and cold (figure 3) - and circulated through an attached curing chamber that is mounted within a lifting frame (figure 4). JEC Composites Magazine / No36 October - November 2007

JEC COMPOSITES MAGAZINE - Issue #36 - October 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #36 - October 2007