New Preform Process
A consortium formed by IACMI – The Composites Institute has developed a new CFRP manufacturing process that improves fabric formability compared to traditional woven materials. The first phase of the project shows promise for easier and safer production of carbon fiber composites.
Led by DuPont in partnership with Fibrtec Inc. and Purdue University, the process has the potential to increase design flexibility and decrease the cost of production for carbon fiber composite structures. This could allow for “net near shape” preforms, where initial production of the preforms is close to the final shape, reducing the need for finishing. That would be a compelling option for automotive and other high-volume industries requiring complex shapes.
The process uses Fibrtec’s flexible coated carbon fiber tow, FibrflexTM, which is partially impregnated with DuPont’s polyamide thermoplastic resin and then processed with DuPont’s Rapid Fabric Formation (RFF) technology. The research was facilitated by Purdue University’s modeling and characteristics capabilities software for the development of the net near shape preforms.
The new process begins when Fibrtec partially impregnates the outer layers of carbon fiber, leaving the inner material uncoated to maximize the flexibility of the ribbon-like tow. “Fibrflex preforms rapidly consolidate to a void-free composite under heat and pressure,” says Bob Davies, CEO of Fibrtec, Midland, Texas. “Using a 12K carbon fiber, the resulting 5-millimeter wide, 0.3-millimeter thick tape is easily manipulated and draped, ready to produce near net shapes through RFF.”
Davies adds that the tapes can be woven or braided and “drape without wrinkling or buckling as compared to fully consolidated rigid unidirectional tapes or organo sheets made from films and fabric, which are stiff and board-like.”
The process eliminates another potential issue with woven fabric: Weaving dry fiber tows often causes fiber breakage, releasing short, conductive carbon fiber strands into the environment. Because of this issue, looms and equipment must be electrically isolated. The Fibrflex product fully encapsulates the fiber with a thermoplastic sheath, preventing fiber breakage.
DuPont’s RFF process quickly manufactures fabrics in varying orientations using robotic tow placement, eliminating the need to lift the tow during processing. Experiments, modeling and simulations conducted by Purdue University have reportedly shown that this combination of materials and process has the potential for producing lower cost continuous FRP materials with a thermoplastic matrix that conforms well during molding.