Manufacture and Thermomechanical Characterization of Wet Filament Wound C/C‐SiC Composites

The paper presents manufacture of C/C‐SiC composite materials by wet filament winding of C‐fibres with a water based phenolic resin with subsequent curing via autoclave as well as pyrolysis and liquid silicon infiltration (LSI). Almost dense C/C‐SiC composite materials with different winding angles ranging from ±15° to ±75° could be obtained with porosities lower than 3% and densities in the range of 2 g/cm3. Thermomechanical characterization via tensile testing at room temperature and at 1300 °C revealed higher tensile strength at elevated temperature than at room temperature. Thus, C/C‐SiC material obtained by wet filament winding and LSI‐processing has excellent high temperature strength for high temperature applications. Crack patterns during pyrolysis, microstructure after siliconisation and tensile strength strongly depend on the fibre/matrix interface strength and winding angle. Moreover, calculation tools for composites, such as classical laminate and inverse laminate theory can be applied for structural evaluation and prediction of mechanical performance of C/C‐SiC structures

Mechanische Charakterisierung von faserkeramischen Materialien unter Hochtemperaturbedingungen (Masterarbeit)

Im Rahmen dieser Masterarbeit wird ein Versuchsaufbau zusammengestellt, um CMCs unter Hochtemperatur mechanisch zu charakterisieren. Es werden anschlieÿend Flachproben aus C/C-SiC mit verschiedenen Faserorientierungen und Rohrproben aus SiC/SiC unter verschiedenen Versuchsbedingungen getestet. Dazu werden zum einen Zugversuche und zum anderen zyklische Zugversuche durchgeführt. Der Temperaturbereich für die C/C-SiCProben liegt dafür bei Raumtemperatur und einem Hochtemperaturbereich von 1300 - 1600°C. Die SiC/SiC-Rohrproben werden bei 1200 °C getestet. Hierzu wird für beide Probengeometrien ein geeignetes Gripping-Konzept ermittelt. Anschlieÿend werden die Mikrostruktur und Bruchfläche von den C/C-SiC-Proben zerstörungsfrei untersucht. Die darauf folgende Auswertung der Ergebnisse ermöglicht ein Verständnis für das Materialverhalten der C/C-SiC-Faserkeramik für verschiedene Faserorientierungen und Thermallasten. Die Resultate aus den Untersuchungen der SiC/SiC-Rohrproben validieren das hierfür gewählte GrippingKonzept, welches einerseits durch die Reproduzierbarkeit der Ergebnisse und andererseits durch den Abgleich der erhaltenen Werte mit der Fachliteratur gestützt wird

Manufacture and Thermomechanical Characterisation of Wet Filament Wound C/C-SiC Composites

Ceramic matrix composites based on wet filament winding and LSI-processing are attractive candidates (C/C-SiC) for many applications in aerospace. Therefore, commercial C-fibres and a water-based phenolic resin were used for wet filament winding on a mandrel and subsequent curing in an autoclave, followed by pyrolysis to a C-matrix and liquid silicon infiltration (LSI) to form a C-SiC-matrix. By applying wet filament winding the mechanical properties can be tailor-designed according to the chosen fibre orientation since C/C-SiC is a fibre dominant and damage tolerant CMC material. Wet filament winding was performed on a mandrel with winding angles of +/-15°, +/-30° and +/-45°, +/-60° and +/-75° were made possible by cutting samples in perpendicular direction. Tubes in wet state were cut in axial direction, flattened and cured on a flat plate without applying additional pressure, such as warm pressing, in order to obtain similar curing conditions to tubes. Mechanical and thermomechanical characterisation of flat specimen of C/C-SiC composites was performed by using an Indutherm universal testing machine using inductive heating of samples and a laser extensometer for measuring of displacement under inert conditions. Testing of tensile specimens was performed at room temperature as well as high temperatures up to 1600°C. In addition, microstructural characterization was performed by SEM