Thermo-mechanical coupled simulation of the thermoset automated fibre placement process

With increased demand for carbon fibre reinforced parts, automated manufacturing methods like fibre placement are well established for aircraft and spacecraft manufacture. However the automated manufacturing process is still in development despite its extensive use in industry. The quality of the automated deposition processes heavily depends on the tack of the preimpregnated thermoset fibres. Without sufficient tack the fibres do not stick to the surface and the process will fail. One key aspect to influence the magnitude of tackiness and therefore the quality of parts attainable from the thermoset Automated Fibre Placement process is the impact of the heat source. For most industrial applications, an infrared heater is used and suitable process windows are still defined by trial-and-error approaches. Further, to utilize AFP's strong potential to deposit fibres on complex curvature surfaces or even steer the slit-tapes along a load path, the need arises to analyse emerging defects like gaps or bridging. The deformability of the compaction roller further influences tack with contact time and compaction pressure. Commercially available software solutions allow the kinematic offline-simulation of the lay-up process, but do not take into account any process parameters or material properties. To reduce this gap in design and to understand the complex interactions of the process parameters the main goal of this thesis is the coupling of those thermal and mechanical interactions. Different analytical and numerical models were developed to achieve this goal. Robust thermal prediction tools in different dimensions are presented, and validated with experiments with very good agreement to simulation values. The deformation behaviour of an industrial compaction roller on convex and concave tooling is studied and a simulation model of the roller developed that is able to accurately predict the deformation behaviour and pressure distribution under the roller. With the individual thermal and mechanical models a sequentially coupled thermal-mechanical model with geometry update is developed that is able to capture the continuous placement process, including the result variables compaction pressure, contact time and process temperature. Further, an analytical relationship between adhesive failure and compaction pressure, process temperature and feed rate is found, with good agreement to experimental results from literature.