Fraunhofer Institute for Material and Beam Technology IWSHigh-rate Capable, Efficient Lightweight Fuselage Shells, Novel Design Principles and Technology Modules, Integrally Optimized and Validated for Damage-tolerant, Rivet-free Structural Joining Technologies
Problem Statement
To achieve the ambitious climate goals of the aviation industry, future aircraft generations must be built significantly lighter. Existing manufacturing and design methods using riveted joints do not fully exploit the lightweight potential of Carbon Fiber Reinforced Plastics (CFRP). Furthermore, the desired high production rates lack continuous, industrialized process chains for rivet-free joining technologies. In addition, innovative and automated construction methods require new validated design and verification methods to ensure the approval and safety of these advanced structures.
Project Objectives
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.
Realization
The collaborative work is divided into five main work packages: Requirements and Design Principles, Holistic Design and Manufacturing Solutions, Holistic Assembly and Integration Concepts, Certification Methodology and Generic Technologies, and Validation and 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.
Subproject at Fraunhofer IWS and Fraunhofer IFAM
Fraunhofer IWS and Fraunhofer IFAM are working on the development of inline pretreatment and in-situ quality assurance methods for the cleaning/activation of CFRP surfaces, as well as an automated process chain for secure, high-rate capable, paste adhesive bonding of a thermoset CFRP fuselage longitudinal joint – from concept to a testable component – as an alternative to riveting. Fraunhofer IFAM contributes a module for calculating the damage tolerance of adhesive joints to the design and verification procedures for the new construction methods.
To achieve this, 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.
Surface defects on CFRP-surfaces shall be detected and classified inline including localized pretreatment and compensation to speed-up paint processes and to improve their efficiency. The aim is to replace time and cost-consuming post-processing and re-work to achieve high-rate capability. In parallel, measurement methods are being upgraded in combination with automated evaluation methods in order to check the quality of pretreated surfaces for adhesive bonding processes.
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 aerospace industry through the integration of innovative in-situ quality standards and automated adhesive bonding processes.