For 20 years, Collins Aerospace has developed, improved and manufactured filament wound products at its Composites Centre of Excellence in Banbury, UK. Filament winding is a highly automated, controlled and repeatable process that produces high performance and lightweight tubular products. Due to its automated process, much of the component cost is directly attributed to the cost of the resin and the fibre, particularly when high toughness prepreg slit tape is required. With many stages of production for the material, the slit prepreg can impact the overall cost – up to five times more - in contrast to the fibre and resin constituents.
Collins Aerospace has been investing in alternative ways to manufacture toughened slit tape and tow-preg materials without compromising the final component performance. A tow-preg processing route was developed and optimised, whereby a narrow band of very high viscosity resin with a uniform thickness is consolidated with the dry fibre tow. By applying shearing and compressive forces, the resin is forced between the individual fibres in the tow bundle in a single process without causing handling damage to the fibre. This process is effective, allowing the toughen tow-preg material to be processed at commercially viable rates with multiple tows simultaneously impregnated. The resulting continuous process eradicates the need for multiple backing papers and freezing steps. By using this tow-preg material, a component cost saving can be achieved with no detriment to the mechanical performance of the material or in the finished component. This tow-preg material can be used in conventional filament winding to produce damage tolerance transmission shafts, axial struts, tie-rods, etc.
To assess the damage tolerance, test components were wound on a six axis robot filament winding machine. These tubular specimens were assessed for compression after impact performance in which it was demonstrated that the material matched the commercially available materials. Further, mechanical testing was performed at both coupon and component level which demonstrated improvements in strength and stiffness control. The materials showed no signs of tow buckling, had a consistent tow thickness, a very low void content, and were below that of commercially available processed materials.
The production of this novel tow-preg material will be employed in a range of toughen shafts and struts for use in a wide range of applications moving forward.