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High Speed AFP Processing of Thermoplastics

Today, large aircraft components rely on automated fiber placement (AFP) processing followed by an autoclave cure. High-speed AFP processing has proven very effective for insitu layup using thermoset materials on latest generation AFP equipment. There remains, however, a substantial opportunity to utilize thermoplastic preimpregnated (prepregs) for large structural components in commercial aircraft. Thermoplastics have an advantage with the elimination of uncured resin build-up. The build-up limits AFP reliability and productivity. This advantage hasn’t been realized because most thermoplastic research has centered around full insitu consolidation intending to eliminate post-processing for curing. The main restriction of full insitu consolidation is on the speed (and productivity) of the AFP process, which is limited by the physics or chemistry of thermoplastic materials. This method places all the demands of final part quality (low porosity, proper crystallinity and autohesion) on the AFP process. In addition, the insitu consolidated AFP process is further complicated by being sensitive to the quality of the raw material, which can vary greatly from supplier to supplier and for each material matrix. Current advances in materials, AFP technology and post processing can greatly increase the productivity of thermoplastics for large structural components. Toray Advanced Composites’ CF/PEEK TC1200 is a well-established material in the industry, providing a large material property baseline for reference and comparison. TC1200 was used in the high-speed trials with success. CF/LMPAEK (TC1225) is the latest slit tape that provides a lower viscosity, and lower processing temperature, that will enable even faster AFP speeds and part complexity. The advances in AFP technology, such as the new, Variable Spot Size (VSS) laser, have enabled the AFP processing of thermoplastics with individual tow heating. There are new Out-of-Autoclave (OoA) post-processing methods that can achieve the proper crystallinity and autohesion. By implementing these advances together with high speed AFP processing, the advantages of thermoplastic materials can be realized for large structural part.