Modeling of the pvT-Behavior at high cooling rates

• Applicant: Professor Dr.-Ing. Christian Bonten
• Subject Area: Plastics Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456358867

Nowadays, simulation programs are used to predict the process and component properties on the one hand and to design the components and processing tools in such a way that the products with the required properties are produced on the other hand. Despite the increasing success of injection moulding simulation programs, the process influences on the material behaviour are not yet completely mapped in the simulation and therefore cannot be reliably predicted. Until now, conventional pvT measurement data and their calculation models have been used to calculate shrinkage, warpage and residual stresses. The pvT behaviour is essentially influenced by the prevailing pressure, temperature and cooling speed. Due to the lack of measurement possibilities, however, only the influence of pressure and temperature at a constant, low cooling rate is mathematically described.The objective of the proposed research project is to model pvT data at a constant, very high cooling rate. For this purpose, liquid carbon dioxide (CO2) is to be used as the cooling medium, deviating from the state of the art and research. The use of CO2 as cooling medium promises high, controllable cooling rates, which reach the cooling rates of the injection moulding process. For example, a pvT measuring instrument based on the proven cylinder-piston measuring method is to be developed and manufactured, which will achieve pvT measurements at several 1000 K/min for the first time.On the basis of the new measuring method, the interrelationships are to be fundamentally investigated. For this purpose, experimentally determined material parameters and associated mathematical material models are necessary, which can describe the pvT material behaviour more realistically. Preliminary investigations of the applicant already show first approaches. The model parameters are determined using a new method that takes into account the non-isothermal effects that occur during the cooling process. The new method will be developed for amorphous and semi-crystalline materials. Finally, the developed methodology will be applied to different materials and their influence on the modelling will be analysed. The results of the modelling will be validated by additional analytics (e.g. X-ray diffraction and transition temperature microscopy). A transfer of the gained knowledge and the evaluated mathematical model could subsequently be implemented in process simulation programs.

• DFG Programme: Research Grants