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UBC Theses and Dissertations

Investigation of prepreg tack through development of an AFP simulator using in-situ sensing and physics-based simulation Bakhshi, Nima


Automation has driven significant advances in aerospace composites manufacturing. Yet the ever-increasing demand for connectivity and accessible air travel requires the industry to further innovate to manufacture ever larger and more complex structures in a more robust, efficient, and cost-effective manner. A fundamentally science-based approach is proposed that first senses critical process parameters affecting quality outcomes. This data is then analyzed within a physics-based framework representing the manufacturing system. The resulting information is leveraged to plan and optimize the process, which can ultimately be integrated into a cohesive process control strategy. While this framework is technology-agnostic, Automated Fibre Placement (AFP) has been selected for further study. A key material property in this process is prepreg tack. Currently, a considerable gap exists between the state-of-the-art of tack characterization methods and even research AFPs, that are far less industrial scale systems. This work seeks to bridge this gap through the development of a table-top AFP simulator (µAFP) that simulates the tow deposition process and incorporates custom operations such as in-situ peel tests. An in-situ peel test method has been developed that implements the µAFP to characterize prepreg tack during fibre placement. The method has been employed in a series of studies to extensively examine various effects of deposition and peel rates, deposition and peel temperatures and substrate orientation, on tack. A physics-based process simulation framework is introduced, encompassing the development of an equivalent tow deposition model and the incorporation of a pre-existing open-literature tack model. The application of the framework is discussed through a case study. Synchrotron Radiation Computed Tomography has been conducted on prepreg-prepreg layups to evaluate the microstructure of intimate contact. In-situ peel tests have been performed on the corresponding process conditions, to qualitatively establish a link between process conditions, microstructure, and tack. Smart AFP compaction rollers can measure local nip point pressure, in-situ. A comprehensive approach is developed for mechanical design of smart rollers. The smart rollers are finally employed in µAFP to illustrate the application of in-situ process parameter monitoring. These measurements can assist in detecting substrate features, predicting process outcomes, and correlating local conditions with process outcomes.

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