Experimental and numerical thermo-structural analyses on SiC/SiCN filament-wound cylinders (Masterarbeit)

Abstract

Ceramic matrix composites (CMCs) are a class of advanced materials able to offer improved fracture toughness, high-temperature resistance and excellent strength-to-weight ratios compared to traditional monolithic ceramics. Among several types, non-oxide SiC/SiCN composites have demonstrated great potential to be applied as hot structures in turbine engines thanks to their high mechanical strength and oxidation resistance. In this context, the Department of Ceramic Composites and Structures (BT-KVS) of DLR Stuttgart is currently involved in a project concerning feasibility studies on the application of SiC/SiCN tubes into micro gas turbines. This work represents a research study in the development of an in-house experimental method for the validation of numerical simulations based on CMC tubes. An experimental mechanical and thermal characterization is performed on SiC/SiCN cylinders manufactured via filament-winding and PIP process. The aim of the characterization is to retrieve the in-plane laminate properties and then obtain the unidirectional lamina properties by means of an inverse Classical Laminate Theory (CLT) approach. These properties will feed a thermo-structural FEM model whose predictions will be compared with the outputs of experimental in-situ observations, based on infrared thermography and Digital Image Correlation (DIC) techniques. In order to pursue the project objective, high-temperature experiments are performed on SiC/SiCN and stainless steel cylindrical specimens. The final results showed that the conceptualized experimental methodology is well-placed but has room for improvement, achievable with adjustments to the testing rig and to the inner temperature analysis method. Moreover, it is pointed out how the limitations of the conducted material characterization and the use of some modeling strategies affected the numerical and experimental results matching.