Optimisation of a new ceramic matrix composite (CMC) high temperature fastener by a thermo-mechanical FEM stress analysis

Kurzfassung

As part of a world wide effort to minimise the cost in development and Operation of manned and unmanned space flight, reusability has been a prime focus in all aerospace engineering projects. The development of Reusable Launch Vehicles (RLV) have been an area of interest to Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) - the German Aerospace Center in Stuttgart, Germany. At DLR Stuttgart, the use of extremely high temperature resistant Ceramic Matrix Composite (CMC) material on RLV's Thermal Protection System (TPS) and hot structures has been successfully developed for many years now. To extend this application further, a new patent CMC fastener was subsequently manufactured from DLR's in-house C/C-SiC material to attach the TPS or hot structures to underlying substructures. This has made way for the primary objective of this project. To create a thermo-mechanical Finite Element (FE) analysis using non-linear contact analysis with friction, to model the complex behaviour of contact between the various surfaces, especially the thread surfaces. And subsequently the optimisation of the fastener to alleviate the fastener's loading sustainability and hence minimise the stresses of the fastener. This project provides a detailed report on the different aspects of the fastener and material evolution, the process of generating and analysing the FE models in the FE Software ANSYS v5.6. As a results, a new optimised fastener was designed giving a significant increase in the fastener's strength, or lowered stresses, to satisfy the objectives of this CMC fastener optimisation project.