DFG-SFOB

This DFG funded project investigates the processing of staple fiber yarns made from recycled carbon fibers (rCF-SF) to organo sheets and the characterization of their pseudo-plastic deformation behavior in thermoforming experiments.

In the first phase of the project, staple fiber yarns made of rCF and PA6 were comprehensively analyzed. The focus was on the material composition, linear weight, as well as thermal properties such as melting and degradation temperatures. Additionally, the compatibility between fiber and matrix was investigated, which was evaluated using single fiber pull-out tests. Subsequently, these yarns were processed in a modified calendaring process, whereby the yarns were heated above the melting temperature of the polymer and stretched by a speed difference between the rolls in order to align the fibers. The impact of total stretch and the number of passes through the calendaring unit on fiber orientation and mechanical properties was examined.

Based on these findings, tapes were produced at varying process temperatures and analyzed in terms of mechanical properties, thermal damage, pore volume and tape quality. These investigations led to thermally undamaged tapes, which met the quality requirements for automated tape laying.

The manufactured tape preforms were further processed into organo sheets using an autoclave and subsequently investigated for their pseudo-plastic deformation behavior in a specially developed test setup for temperature-controlled tensile tests. This experimental setup enables homogeneous heating of the tensile specimens in the loaded area. Once the target temperature has been reached, the high-speed tensile test is carried out and the specimens are then reconsolidated. In these tests, process parameters such as test speed and test temperature as well as the total stretching of the SF-tapes are systematically investigated in order to determine their influence on the pseudo-plastic deformation behavior. The data obtained will be utilized to develop a model that precisely describes the process behavior during thermoforming.