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

• Final Report Year: 2023

Final Report Abstract

With the increasing need for lightweight construction in the aerospace and automotive industries, composite structures are becoming a sought-after option due to their high strength-to-weight ratio, which in turn depends on the interaction between fibers and matrix during the curing phase of the thermoset matrix. Therefore, monitoring this process is an important aspect of research in this area. In recent years, different methods for in situ monitoring of fiber composites have been investigated. Considering these research results, the aim of the project was the development of a passive, wireless, in situ sensor, which enables the current degree of curing of epoxy resin in the carbon fiber composite to be monitored. The findings from the previous project were used as the starting point for the sensor design. In addition, the sensor was designed for a higher operating frequency, thereby miniaturizing the sensor and consequently reducing the weakening of the composite material due to the embedded sensor. The central difference to the previous project lies in the development of an in-situ sensor for monitoring the current degree of curing of carbon fiberreinforced composite materials. Due to the conductivity of the carbon fibers, the sensor's antennas have been augmented with dielectric channels, maintaining wireless sensor operation. The influence of the geometry of the dielectric channels on the mechanical properties of the carbon fiber composite material (CFRP) was investigated. To be able to design and optimize the sensor in a simulative way, the materials involved were characterized with regard to their electrical properties. The individual components were then designed, and their functionality verified by simulations and measurements. The geometry and dimensions of the dielectric channels were chosen as a compromise between electrical functionality and weakening of the composite material. A parametric model was developed to optimized force-lines along the fibers around the sensor and thus optimizing sensor geometry to minimize stress-accumulation. The obtained geometry was further validated using finite-element analysis and mechanical testing for improved performance of a composite sample embedded with a dummygeometry. Based on this model, the geometry of the sensor, which combines the previously designed individual components, was optimized. The sensor was tested under controlled climate conditions in the CFRP network. Depending on the current degree of cure of the epoxy matrix, the resonance frequency and the amplitude of a resonator integrated in the sensor change, which confirms the sensor concept for monitoring the degree of curing in real time.

Publications

• “Innovative drahtlose Sensorkonzepte für das in-situ Monitoring von Aushärtevorgängen in Epoxidharzsystemen und Faserverbundbauteilen,” in Tagungsband 4. Symposium Materialtechnik, Fortschrittsberichte der Materialforschung und Werkstofftechnik. Düren:Shaker Verlag, 2021, S. 698–711.
  B. Dorbath; J. Groh; J. Schür & M. Vossiek
  
• “Mechanical performance evaluation of carbon fiber composites equipped with an in-situ wireless sensor body” in Verbundwerkstoffe - 23. Symposium Verbundwerkstoffe und Werkstoffverbunde, DGM, 19.07.2022 - 22.07.2022
  G. S. Dutta; B. Dorbath; G. Ziegmann & M. Vossiek
  
• Passive, Wireless In Situ Millimeterwave Sensor With Mounted Dielectric Channels for Cure Monitoring of Carbon Fiber-Reinforced Polymers. IEEE Sensors Journal, 23(20), 24438-24451.
  Dorbath, Benedikt; Schür, Jan; Ziegmann, Gerhard & Vossiek, Martin
  
• Single-Fed Additively Manufactured Conical Horn Antenna with Circular Polarization for Millimeter-Wave Applications. 2023 17th European Conference on Antennas and Propagation (EuCAP), 1-5. IEEE.
  Dorbath, Benedikt; Lomakin, Konstantin; Pfahler, Tim; Schür, Jan & Vossiek, Martin
  
• “Mechanical Performance Evaluation of Fiber Composites Equipped with In- Situ Wireless Sensor Bodies,” Tagungsband 5. Symposium Materialtechnik, 2023. ISBN 978-3-8440-9105-2.
  G. S. Dutta; G. Ziegmann; W. Li; B. Dorbath; M. Vossiek & J. Guhathakurta
  
• Transmission Loss Analysis of Unidirectional Carbon Fiber-Reinforced Polymers for Millimeter Waves for Linear and Circular Polarization. IEEE Transactions on Microwave Theory and Techniques, 72(3), 1729-1738.
  Dorbath, Benedikt; Schür, Jan & Vossiek, Martin