Developing a multifunctional, wireless sensor system for monitoring the process parameters during the production of carbon-fiber reinforced composites

• Applicants: Professor Dr.-Ing. Martin Vossiek; Professor Dr.-Ing. Gerhard Ziegmann
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Plastics Engineering ; Polymer Materials
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417571210

In a previous projec, a direct relation between the degree of curing of resin systems and their dielectric characteristics at 24 GHz was proven by correlating the curing curves of an innovate reaction kinetics model with permittivity curves. In addition, a novel batteryless, wireless 24GHz sensor for recording in-situ the permittivity and temperature during curing within a fiber composite structure was developed and successfully tested experimentally.Given that this sensor is suitable only for use in non-conductive fiber-reinforced composites (FRCs), the present project will investigate the extent to which it can be successfully adapted for use in FRCs with conductive carbon fibers (CFs), as carbon fiber reinforced composite structures must operate to the highest standards in structural components.The problem with carbon fiber reinforced polymers (CFRPs) is that the radio signal between sensor and scanner is highly attenuated by the conductive fibers. The attenuation depends mainly on the polarization of the electromagnetic fields and the fiber arrangement.In order to classify the effects of different textile layers, fiber volume ratios and polarizations, they will be characterized with, and without curing epoxy resin at different temperatures by means of a quasi-optical transmission system. This will determine at which configurations the material cannot be irradiated without additional measures. The transmissivity should be improved by introducing dielectric channels above the antennas. To this end, a concept is required for constructing the channels and for precisely inserting them before the structure is infused, so as to minimize any effects on the structural load capacity of the surrounding component. The sensor operating frequency should be increased, as well, in order to minimize the dimensions of sensor and channels – thus moderating the structural impact. Due to the newly added requirements, only the basic principle of operation for the sensor from the previous project can be applied in the new project. The sensor itself and the dielectric channels must be completely redesigned.A linked simulation model needs to be designed to first compute the mechanical impact of the embedded sensor and the associated channel on complex structures, and to determine the effects of sensor geometry and boundary-layer adhesion. The simulation thus supports the empirical optimization of sensor loading with respect to geometry and boundary layer.Based on the test results for the sensor components and structural mechanics, the final wireless sensor will be designed, assembled and tested in a fiber-composite curing process. Finally, the novel sensor will be tested in a real infusion process to verify its practical usability.

• DFG Programme: Research Grants