Enhancing the Automated Tape Placement Process: Novel Approaches in Flashlamp Heating and Tape Steering for Thermoplastic and Natural Fiber Composites

Automated Tape Placement (ATP) is a process widely used in composite manufacturing. Due to the high degree of automation and the ability to produce complex geometries with high precision, this process is particularly of interest for high-performance industries such as the aerospace industry. This dissertation presents significant advancements in two promising aspects for further enhancing the ATP process: tape steering and flashlamp heating. A special focus is placed on the processing of thermoplastic matrix materials. The first part of the dissertation explores the novel processing technique of stretch-steering using highly aligned discontinuous fiber tapes in ATP. By applying in-situ tensile strain during tape placement, the process enables the production of laminates with steering radii two orders of magnitude smaller compared to the current capabilities of continuous fiber tapes. Steering radii of 25 mm for 12.5 mm wide tapes are possible. A novel photogrammetry-based measurement methodology is developed to assess strain distribution and path deviation during steering, providing insights into the mechanical behavior of the tape under various processing conditions. This technique not only verifies the feasibility of stretch-steering in reducing the minimum steering radius but also offers a new approach for optimizing the ATP process to minimize defects and enhance material performance. The second part of the dissertation investigates the feasibility of using flashlamp heating systems as an alternative to conventional laser and hot-gas torch systems in ATP. Flashlamp heating offers advantages such as high energy density, short response time, and scalability for large tape widths, all while maintaining a compact system size. The study investigates the effects of flashlamp heating on bonding strength and tape width variability. Ideal parameters for the bonding strength and low tape width variability are found. Further assessment of the influences on the bonding strength shows that the moisture within the tape and the flashlamp heating system quartz guide geometry have a significant influence. Natural fiber tapes are processed for the first time using a flashlamp heating system. Optimal processing parameters are found to mitigate fiber degradation by analyzing the material itself and the influence of the flashlamp heating system parameters. Tensile, compressive, three-point bending, and double cantilever beam tests are conducted to assess the mechanical performance of the natural fiber-reinforced thermoplastic tapes. Different processing variations are tested, and a combination of ATP with a consecutive consolidation step in a hot press improved the compressive, flexural, and fracture toughness properties of the natural fiber polypropylene composite. The effect of the processing temperature on tape temperature as well as the pressure distributions of the consolidation roller onto the tape are monitored for all studies. Thermophysical analysis is used to assess changes in crystallinity and to aid in the process parameter selection. The findings of this research contribute to the broader scientific community by introducing new methodologies for strain measurement and path deviation analysis in ATP, validating the use of flashlamp heating for high-performance composite manufacturing, and advancing the application of stretch-steering in the production of complex composite structures. The dissertation lays a foundation for future studies on the integration of these novel ATP technologies in industrial applications, particularly in the aerospace sector, where the demand for lightweight, high-strength materials continues to grow.