Experimental and Numerical Investigation of Crystallization Kinetics in Selective Laser Sintering

The selective laser sintering process depends on tight coupling between thermal history and polymer crystallization to achieve parts with good mechanical properties. This study experimentally examines crystallization of carbon fiber reinforced polyamide $11$ during selective laser sintering. Differential scanning calorimetry is used to experimentally characterize crystallization kinetics under isothermal and non isothermal conditions. The kinetics are coupled with a numerical print scale thermal model. Results show strong sensitivity of relative crystallinity to temperature and cooling history. Crystallization exhibits both primary and secondary mechanisms, with slower secondary crystallization becoming dominant at later stages of crystallization. A Dual Nakamura formulation is chosen to represent primary and secondary crystallization and is fitted to experimental data. The model shows good agreement with independent non-isothermal measurements at low cooling rates. Numerical simulations resolve temperature fields and relative crystallinity during printing and cooling. Thermal gradients and cooling rates drive spatial variation of crystallization across the build volume. The combined experiments and simulations can guide process parameter selection and part placement to improve consistency and mechanical performance.