Numerical and semi-analytical modelling of the process induced distortions in pultrusion

The geometrical changes of the processed material (process induced distortions) are a critical issue in pultrusion, since they affect the process dynamics (mainly the pull force), as well as the mechanical properties and geometrical precision of the final product. Hence, a detailed understanding of the mechanical behavior generating the distortions during the process is eventually required. In the present study, two different modelling approaches are implemented and compared to calculate the development of the distortions during the pultrusion of a graphite/epoxy composite rod. In both cases, the temperature and the degree of cure distributions are obtained from the thermo-chemical analysis, using a finite element and a finite volume approach, respectively. Process induced distortions have been computed solving a sequential stress-strain finite element model, in the former case. In the latter, the transient distortions are inferred adopting a semi-analytical procedure, i.e. post processing numerical results by means of analytical methods. The predictions of the process induced distortion development using the aforementioned methods are found to be qualitatively close to each other. Furthermore, the location of the detachment between the heating die and the part due to shrinkage is also investigated.