• C/SiC Composites
• Ceramic Matrix Composites
• Microwave-Assisted Chemical Vapor Infiltration
• Polymer Infiltration and Pyrolysis
• SiC/SiC Composites
• SMP-10

The growing demand for a new generation of materials characterized by increased toughness, high-temperature stability, low density, remarkable thermal shock resistance, high hardness, and superior corrosion resistance, in various applications such as the aerospace industry, has driven the development of novel Ceramic Matrix Composites (CMCs). In contrast to conventional monolithic ceramics, CMCs mitigate their usual inherent brittleness thanks to the characteristic pseudo-ductile fracture behavior given by a tailored fiber-matrix interfacial domain.

In this study, two different SiC-matrix manufacturing processes for CMCs have been investigated along with the development of a robust CMC preform manufacturing method. First, a 2D 8.5oz 4x4 3K Twill Carbon fiber and a polymeric precursor, Allylhydridopolycarbosilane (SMP-10), developed by Starfire Systems, were employed for the fabrication of Cf/SiC CMCs with various open porosities and sizes using the Polymer Infiltration and Pyrolysis (PIP) method. In this framework, the thermo-physicochemical properties of SMP-10 were thoroughly investigated without the inclusion of fibers to determine the optimized thermal parameters for both the curing and pyrolysis stages.

Subsequently, the final CMCs were manufactured under 0-7 cycles of the PIP densification process with the optimization of each step to investigate changes in density following each densification step. Remarkably, an 84% increase in the relative density was observed after the completion of 7 densification cycles.

As for the second manufacturing technology, SiCf/SiC composites have been produced by an advanced and environmentally friendly Microwave-assisted Chemical Vapor Infiltration (MW-CVI) technique as a part of the European CEM-WAVE project activities (GA n°958170).

In this framework, SiCf/SiC preforms, have been manufactured within the CEM-WAVE project scope by the Fraunhofer ISC (Bayreuth, Germany) partner, using third-generation Hi-Nicalon Type S SiC fibers by the Filament Winding technique. Following this, the SiCf/SiC preforms were infiltrated by subjecting to a 10-hour densification process using the MW-CVI technique, resulting in an 8.8% increase in relative density.

Finally, this thesis work aims to evaluate the combination of these two manufacturing methods, assessing the potential synergy between these two techniques with the aim of improving overall efficiency, and reducing both the total manufacturing time and costs. This integrated approach paves the way for a comprehensive comparative analysis of these two methodologies.

In this work, comprehensive characterization analyses of the precursor were conducted, employing Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. Furthermore, μ-CT and meticulous Scanning Electron Microscopy (SEM) examinations were carried out to investigate the SiC matrix distribution within the preform in order to confirm the inside-out densification pattern, and porosity values and evaluate the structural defects and open porosity values within the as-developed CMC samples, respectively.

It is also important to note that the activities associated with the initial phase, which involved manufacturing Cf/SiC CMCs through PIP techniques, were conducted under the coordination of Professors Andrea Lazzeri and Joanna Wong at the Laboratory of Engineering Materials, University of Calgary, Canada. This part of the research effort was primarily sponsored by the ISSNAF scholarship. Additionally, the second part of the project, focused on creating SiCf/SiC CMCs using the MW-CVI technique, was carried out at the joint IPCF-CNR-DICI labs in Pisa, Italy, in the framework of the European CEM-WAVE project.