• C/C-SiC
• Ceramic Matrix Composite
• CMC
• Thermomechanical
• validation method

The ceramic matrix composite (CMC) C/C-SiC has found many applications such as: propeller disc brakes, hot gas liners, re-entry nose cap, nozzles for rockets, jet vanes for thrust vector control of solid propellant rockets, and for spacecraft structures. In order to integrate this material in the designs for products in this field, the material must be properly characterized, and thermomechanical models associated with these designs must be validated with experimental values. At department of Ceramic Composites and Structures (BT-KVS) in the Institute of Structures and Design of DLR in Stuttgart, filament wound C/C-SiC structures are currently under development. A validation method was developed, which was specifically intended to validate thermomechanical FEM models of heated C/C-SiC tubes.
Experiments were designed with special consideration of the modelling and simulation processes. Filament wound C/C-SiC tubes, and seam welded stainless steel tubes were used as samples in the investigation. The axial temperature distributions were measured along the inner and outer surfaces, and curves were fitted to the data in order to provide a thermal boundary condition in the models. The emissivity of several surfaces was determined over the temperature range of 200–800◦C during the experimental work, and these reference values were used to obtain the temperature of the sample from measurements made by using infrared spectrometry. The flow phenomena in the physical problem was studied by infrared imaging, and by using a projection shadowgraph method; these methods are presented in detail, and some examples that illustrate the methods’ usefulness are presented with the intention that they be used in future projects. CTscans made of the samples before and after the tests are presented and compared with a discussion about the effects of oxidation, and relevant analytical models for porous flow are presented for future modelling of the oxidation processes. The radial displacement of the sample along the outer surface was measured by photogrammetry.
This work includes the development of three analytical models for the thermomechanical structural problem; of which one was implemented in a script that provided results that were in close agreement with the simulation results; the results were of the same shape and order of magnitude as those measured by photogrammetry.
An investigation was performed to determine the general trends of the stress and the radial displacement across the wall of a filament wound tube of similar geometry with different winding angle sequences. The general trends observed are explained, and the usefulness of the analytical model and the scripts created are presented.
The agreement between the different facets of the investigation inspires confidence in that the validation method works, and that the analytical model produced is useful. Several reasons are suggested for the discrepancy in the values obtained. Recommendations are made for future work as a continuation of the present work, and possible avenues for application of the tools hereby provided are suggested.