Production-oriented tolerance management for composite parts

The production of high quality and highly-stressed fiber composite components demands complex requirements for fabrication. Process parameters and disruptive factors are influencing part quality and geometry, due to the material characteristics being formed during the manufacturing process. So the main quality aims are fulfilling design demands at simultaneous cost-efficient implementation. The tolerance management coordinates the different needs of design and production. It gives all necessary geometrical and manufactural specifications and instructions for each specific case. The production of varying industrial goods shows major differences. Therefore the used tolerance management concept needs to be adapted for each individual process. Especially the tolerance modeling, essential element of tolerance analysis and optimization, is closely linked with materials, structure and production method. For fiber composites chemical, physical and mechanical elements need to be included in the tolerance chain. The tolerance modeling and optimization is based on statistical production data and probabilistic methods, due to the highly statistical scattering. A production-orientated tolerance management is the combination of these methods with manufacturing boundary conditions. Within the scope of this thesis, an adapted concept is developed. Identification of key characteristic, parameter research, impact analysis, optimization and verification are the major steps. Popular methods of quality assurance, process modeling and probabilistic process optimization are combined and adapted for the production-orientated tolerance management concept. For specialization, the production process of thick laminates with one-side heatable, open tooling is selected. As industrial example the manufacturing of rotor blades for wind turbines is used. Aim of the production-orientated tolerance management is the reduction of manufacturing variances by application of optimized process parameters. Therefore simulation modules to predict fiber volume ratio, process temperature and process-induced deviations are implemented in a tolerance modelling chain. The key characteristic of the application example is the deviation of blind bonding of a rotor blade for wind turbines. The developed tolerance chain includes manufacturing boundary conditions as well as statistical production data. With virtual experiments, the modeled tolerance chain is verified and the fiber volume ratio is optimized. Its reproducible achievement via adjusted process parameters is the result of the optimization. The thesis proofs, that the production- orientated tolerance management is able to achieve a cost efficient improvement of complex production processes. © 2018 Deutschen Forschungsanstalt fur Luft-und Raumfahrt. All rights reserved.