Investigation on the influence of process parameters on the pseudo-plastic deformation behavior of staple fiber organic sheets

The study describes the investigation of the pseudo-plastic deformation behavior of unidirectionally reinforced organic sheets based on recycled carbon fibers (rCF) with a length of 80 mm and polyamide 6 (PA6). The non-isothermal, temperature-controlled tensile tests were carried out by using a specially developed test module and a high-speed tensile machine. In the test module, the unidirectional test specimens were heated by conduction through heating plates and the tensile test was started automatically once the target temperature was reached. The test module enables an ideal laboratory simulation of a thermoforming process, as both the tensile force and the displacement rate are applied simultaneously, preventing any acceleration within the specimen. An increase in the heating plate temperature leads to a reduction of the maximum stress. At the same time, an increase in the test speed causes an increase of the required stress due to the increased strain rate. While a positive effect on the homogeneity of the pseudo-plastic deformation was observed with increasing heating plate temperature, no significant influence of the test speed on deformation homogeneity could be identified. To fully exploit the pseudo-plastic deformation behavior, sufficiently high processing temperatures are required during the entire process. The positive effect of the material temperature on the homogeneity of the pseudo-plastic deformation was confirmed in the thermoforming tests. By increasing the tool temperature and adding an insulating silicone top layer, the homogeneity could be further improved.