Moisture diffusion in carbon fiber composites changes the mechanical properties of the composite. Therefore, a monitoring method of the actual content of moisture in the composite is important. However, at the moment there are no online methods established. A common method is the measurement of the mass changes due to water uptake. This method is not suitable for online monitoring of a real composite part in service. We demonstrate that miniaturized flexible interdigital sensors are suitable for moisture measurement inside the carbon fiber composite. These sensors are directly integrated inside the composite. It was already demonstrated that these can be successfully used for resin-curing monitoring as a primary application. Here we demonstrate that the same sensors are also suitable for moisture measurement inside the material. In order to do so, we expose samples with and without integrated sensors to hot-wet conditions and measure the dielectric changes with the sensors and the mass gain. The moisture concentration and the measured admittance can be directly correlated to each other. This demonstrates that the sensors can be used for moisture measurement as a secondary application. In addition, it is shown that the sensors have the potential to measure the moisture locally inside the material.

No abstract

No abstract

No abstract

Fiber composite components play an important role in the turnaround in energy policy as well as in stopping global warming. Therefore, it is essential to improve the manufacturing efficiency of these components. RFID technology is spreading to digitize and organize processes in production and logistics more efficiently. Since cure monitoring is a crucial factor in the manufacturing of composite components, the question arises whether the RFID technology is applicable for cure monitoring. This paper presents two methods of how an into glass fiber-reinforced plastics integrated RFID transponder could monitor the curing. Following the assumption that the change in permittivity of the glass fiber-reinforced plastic during curing influence the RFID signal, experiments in a measuring chamber (low-interference environment) were conducted. It was investigated whether the optimal response frequency of the integrated RFID transponder changes and whether the received signal strength indicator (RSSI) changes at a specific frequency during curing. As a reference method, the dielectric analysis as a well-known method for cure monitoring was used and compared with the RFID measurements. The results indicate that the optimal response frequency remains constant but the RSSI increases and possess a very high linear correlation with the measurement of the dielectric analysis in a low-interference environment. Consequently, the RFID technology is applicable to monitor the curing of glass fiber-reinforced plastics by measuring the RSSI in a low-interference environment.