HELIOS – High-Rate, Efficient Lightweight Fuselage Shells, Novel Design Methods & Technologies for Damage-Tolerant, Rivet-Free Structural Joining

Project objective

The overall project "HELIOS" aims at the development and validation of novel design principles and technologies for weight-optimized and high-rate capable CFRP fuselage shells. The core of the project is the design of a fuselage shell architecture based on rivet-free joining technologies such as the bonding of longitudinal seams and the hybrid welding of frame-to-skin connections. By the end of the project duration, technological feasibility is to be demonstrated. Furthermore, the process chains shall be evaluated regarding their lightweight potential, high-rate capability and cost-efficiency.

Click here to learn more of the joint project HELIOS, funded by the German Federal Ministry for Economic Affairs and Energy within the framework of the Aviation Research Program LuFo VII-1.

Implementation

The work in the consortium is divided into five main work packages:

1. Requirements & design principles
2. Holistic design & manufacturing solutions
3. Holistic assembly & integration concepts
4. Certification methodology & generic technologies
5. Validation & evaluation

Airbus Operations GmbH is the consortium leader of this project. All consortium partners from industry and research are developing key technologies, including innovative rivet-free joining processes, adapted design and certification methods, as well as automated procedures for quality assurance. The results will be tested and evaluated through structural tests and non-destructive testing on demonstrators.

The consortium consists of the following partners: Airbus Operations GmbH, Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR), Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V. (Fraunhofer IFAM, Fraunhofer IWS), INVENT Innovative Verbundwerkstoffe Realisation und Vermarktung neuer Technologien GmbH, MICOR Gesellschaft für industrielle Wärme und Trockentechnik mbH, SWMS Systemtechnik Ingenieurgesellschaft mbH, TU Braunschweig, TU Hamburg, Universität Stuttgart, Wölfel Engineering GmbH + Co. KG.

Fraunhofer IFAM

Fraunhofer IWS

Subproject at Fraunhofer IFAM and Fraunhofer IWS

As part of the joint project “HELIOS”, Fraunhofer IFAM and Fraunhofer IWS are developing inline pre-treatment and in-situ quality assurance (QA) methods for the cleaning or activation of CFRP surfaces before painting and bonding as well as an automated process chain for secure, high-rate capable, paste adhesive bonding of a thermoset (TS) CFRP fuselage longitudinal joint – from concept to a testable component – as an alternative to riveting. Fraunhofer IFAM contributes a module for simulating the damage tolerance of adhesive joints to the design and verification procedures for the new construction methods.

During the adhesive bonding process, IR emitters are spectrally modified using the DLIP (Direct Laser Interference Patterning) method to enable reproducible adhesive curing based on thermal convection. Additionally, an integrated tooling solution is being developed to allow temperature sensing and control, as well as the application of a defined contact pressure, precise bond line thickness adjustment, and control over the curing profile. Furthermore, feasibility studies are being conducted to assess the transferability of the process to Fiber Reinforced Plastics (FRP) with hybridized thermoplastic surfaces, enabling entirely new manufacturing routes for both existing and novel, disruptive aerospace components. Ultimately, a section of a real half-shell structure is to be joined in an automated process.

To accelerate and improve the efficiency of painting processes on CFRP surfaces, surface defects are analyzed and identified inline as well as locally pre-treated and compensated for in a targeted manner. This is intended to avoid time-consuming as well as cost-intensive rework and enable a high process rate. Accompanying this, measurement methods are being further developed in combination with automated evaluation procedures to reliably verify the quality of, among other things, pre-treated surfaces for adhesive bonding processes.

Another module of the project involves the automatic quality assessment of CFRP components based on ultrasound data. For this purpose, the original data as well as compressed datasets are algorithmically analyzed and used to classify potential defects and anomalies. A key challenge here is the availability of large amounts of data with reliable ground-truth labeling, which is necessary for training and validating the evaluation algorithms. To address this, additional realistic, simulated ultrasound measurements are generated, enabling a systematic investigation and optimization of the evaluation methods.

Conclusion

The development of high-rate capable production processes, along with the reduction of production waste and resource consumption, contributes not only to cost efficiency but also to the reduction of CO₂ emissions. Looking ahead, this approach opens up new possibilities for environmentally friendly aircraft components and, in particular, offers the potential to revolutionize manufacturing methods in the aviation industry through the integration of innovative in-situ quality standards and automated adhesive bonding processes.