B. Höck, M. Regnet, S. Bickelmaier, F. Henne, M.G.R. Sause, T. Schmidt, G. Geiss

Due to the request for lower weight and lower costs for future space structures, MT Aerospace (MTA) is developing a forward-looking manufacturing process for a new generation of composite pressure vessels using thermoplastic tape-laying. This technology promises advantages such as a shorter cycle time and a high level of automation. The manufacturing technology is based on a lay-up head which is equipped with a diode laser which locally melts the matrix of the laminate and the incoming tape. The local temperature distribution measured by a thermo-camera is used for laser control. The focal point of the laser is followed by a consolidation roller which induces the required consolidation pressure during solidification of the thermoplastic matrix. At the end of a track the tape will be cut using by the lay-up head. Thus the component is finished directly after the fiber placement, no further curing process is needed. In several optimization loops the process parameters such as tape tension, nip-point temperature or placement speed have been studied and optimized, leading to a significant improvement of the laminate quality and the mechanical properties. The optimized parameters are used for the manufacturing of two technology demonstrators, which consist each of a pressure vessel with only one dome and an integrated skirt. These demonstrators will be connected using a bolted joint. For the skirt and the segment joint reinforcement layers are needed. To ensure the quality of the laminate the pressure vessels will be inspected using air-coupled ultrasonic testing in a reflection mode. The advantage of this method is the contactless testing of the parts. At MTA the FEM software Abaqus is used to analyze the composite pressure vessel in detail. In contrast to common low fidelity modeling approaches each composite layer of the cross- hoop and skirt layup is discretized with at least one individual element row, i.e. local effects at the end of skirt reinforcement layers can be investigated. The distribution of winding angles and layer thicknesses along the meridian is consequently considered according Clairaut's equation. With this approach the interaction between the demonstrator body and the skirt is reproduced accurately and a high resolution of ply stress results is achieved. A final burst test of both demonstrators will be accompanied by acoustic emission acquisition. AE analysis offers the possibility to localize the failure and to distinguish between fiber breakage, matrix cracking and interfacial failure, based on a validated pattern recognition method. This method showed promising results during material characterization on coupon level and hence will be applied to the signals detected during burst testing of the pressure vessel. Finally the results from the burst test will be compared to the FEM analysis results.

Deutscher Luft- und Raumfahrtkongress 2014, Augsburg

Conference Paper

englisch

manufacturing technology, pressure vessel

Proceedings of 13th European Conference on Spacecraft Structures, Materials + Environmental Testing; SP-727 June 2014; ESA Communications; ESTEC, Noordwijk 2014

ESA Communications; ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands, 2014

978-92-9221-291-9

1609-042X

externe Resource

05.12.2014