Getting better process parameters with the multiscale modelling of the stabilization process of PAN-precursors during carbon fiber manufacturing

Carbon fibres combine excellent mechanicals properties with low density and are therefore very often used in lightweight constructions. The production of carbon fibres is divided into three parts. First part is the production of the raw material (precursor). The second is the thermal conversion to stabilize the fibre and prepare it for the final step. In the last part the carbonization almost all but carbon atoms are eliminated. Resulting in a fibre material containing over 90% of carbon. Even though carbon fibre has been used since the late 1970s in aerospace application, there is still no general method available to find the optimal production parameters and the trial-and-error approach is most often the only resolution. Therefore, the stabilization process is analysed experimentally and by simulation. With the presented model it is possible to perform a complete simulation of the fibre undergoing all zones of stabilization. The fiber bundle is modeled as several circular fibers with a layer of air in-between. Two thermal mechanisms are considered to be the most important: the exothermic reactions inside the fiber and the convective heat transfer between the fiber and the air. The exothermic reactions inside the fibers are modeled as a heat source. Differential scanning calorimetry measurements have been performed to estimate the amount of heat of the reactions. To shorten the required time of a simulation the number of fibers is decreased by similitude theory. Experiments were conducted to validate the simulation results of the fibre temperature during stabilization. The experiments for the validation were conducted on a pilot scale stabilization oven. To measure the fibre bundle temperature a new measuring method is developed. The comparison of the results show that the developed simulation model gives good approximations for the temperature profile of the fibre bundle during the stabilization process.