Integrated sensors secure and monitor the manufacture of thick-walled CFRP structures.


“CFRP Booster Housing,” manufactured using a digitally-controlled vacuum infusion process. (© Fraunhofer LBF)

“Infusion 4.0” a project funded by the Federal Ministry of Economics and Energy, shows how effective fiber-optic sensors are in monitoring the vacuum infusion process during the production of large composite components. Together with its project partner, MT Aerospace AG, the Fraunhofer Institute for Structural Durability and System Reliability LBF has made the previously-hidden process steps visible and digitally controllable, thereby increasing process reliability. This new, efficient manufacturing technology supports reliable and fast development of aerospace products.

Using CFRP booster housings, MT Aerospace AG in Augsburg, Germany, manufactures large CRFP components (carbon fiber-reinforced plastic) using vacuum infusion processes. In vacuum infusion, a dry-wrapped pre-form is inserted in a vacuum bag and is infiltrated with resin while slowly rotating in an oven. Intelligent sensors are required in order to monitor the flow front of the in-flowing resin and to optimize processes. Scientists from Fraunhofer LBF and their industrial partners are embedding fiber-optic sensors into the component as early as the winding process in various 3-dimensional positions. These then control resin distribution during this important production step.

The Digital Twin Plays an Important Role

Each sensor fiber contains several of the more than 60 glass fiber sensors. The flow front is the line when the resin first gets in contact with the dry fibers. The signals are transmitted from the rotating part in the oven to an outside computer in situ in order to digitally monitor the process. A digital representation of the sensor position on the component shows when the flow front reaches the sensor. “We are receiving transparent information for the manufacturing process of these thick-walled parts for the first time. This increases process reliability for vacuum infusion processes,” explains Martin Lehmann, Research Associate at Fraunhofer LBF.

The new manufacturing process makes previously hidden processes visible and digitally controllable, thereby increasing process stability. Information gained by resin flow monitoring ensures reproducibility and quality of the new product, enabling timely intervention if required during production. Production ramp-up can be accelerated with this improved control. This increases the company’s competitiveness.

Screenshot of the digital twin during flow front detection. (© Fraunhofer LBF)

Integrated sensors monitor the flow front process and reduce manufacturing costs

In addition, the new technology makes future automated control of manufacturing processes in Industry 4.0 possible. Integrated sensors provide structural monitoring (structural health monitoring, or SHM) even from the earliest phase of the product lifecycle.

This “Infusion 4.0” project idea won third place in the Innospace Masters Challenge offered by the German Aerospace Center (DLR) in 2017. It was a finalist at the 2018 German Aviation Innovation Award for research needs in this environment. The project’s successful completion in October 2019 confirmed the Darmstadt scientists’ approaches as well as those of their Augsburg colleagues.

The “Infusion 4.0 – Flow front detection in the vacuum infusion process of a CFRP booster housing using fiber optic sensors” was funded by the Federal Ministry of Economics and Energy and approved by a resolution of the German Bundestag.

Förderer und Partner

Das Projekt »Infusion 4.0 – Fließfronterkennung im Vakuuminfusionsprozess eines
CFK-Boostergehäuses mit faseroptischen Sensoren«, wurde laut Beschluss des Deutschen Bundestages vom Bundesministerium für Wirtschaft und Energie gefördert.

“Erstmals erhalten wir im Herstellungsprozess solch dickwandiger Teile transparente Informationen und erhöhen die Prozesssicherheit von Vakuuminfusionsprozessen.” Dipl.-Ing. Martin Lehmann