Screen-Printed Sensor Inlays for Monitoring Bondlines in CFRP-Components

Adhesive bonding is a promising approach for joining lightweight composite components. However, the reliability remains a major challenge, because failures due to fatigue are difficult. In this study, we report on the integration of a screen-printed sensor on polyetherimide substrate into the adhesive layer during CFRP fabrication, enabling in-situ monitoring of potential crack propagation due to internal strain measurement under service loading. The sensor concept is based on the comparison of strain measurements in two different sensor rows to detect deviations in the sensor signal that indicate damage. This work marks the first successful fabrication by screenprinting of a fully polyetherimide-based sensor inlay that exhibits excellent adhesion to the epoxy matrix in CFRP. We used carbon-based inks that withstand the harsh conditions during the co-curing during the CFRP-prepreg-autoclave process. After the integration process, the sensors remained fully functional and achieved a gauge factor of up to 49.