Studies on Fibre Orientation of Carbon Fibre Preforms for Fabrication of C/SiC Fasteners

Abstract

Continuous carbon fibre-reinforced silicon carbide (C/SiC) ceramic matrix composites (CMCs) are one of the most promising candidate materials for many high-temperature applications, particularly as thermo-structural hardware for aerospace and aircraft applications. However, the major challenge lies in joining these composites to the airframe for their application as re-usable thermal protection systems for re-entry vehicles. This necessitates development of suitable fastening mechanisms which can withstand the aero-thermal loads of structures during re-entry conditions. Conventionally used high-temperature fasteners are molybdenum based and they suffer from problems related to oxidation at temperatures above 800 °C in air. Thus for such applications, C/SiC fasteners are considered more reliable due to the oxidation resistance offered up to 1650 °C. This study highlights the importance of fibre orientation in continuous C/SiC composite used for fabricating C/SiC fasteners for futuristic re-entry launch vehicles. The study describes fabrication of four different types of continuous fibre-oriented C/SiC composites viz., 2D stitched, 3D woven, 4D NOOBED and 5D NOOBED configurations via chemical vapour infiltration (CVI) route, and compares their tensile property at room temperature so as to find out a suitable preform for fabrication of C/ SiC fasteners. It was found that 2D stitched preform-based C/SiC specimen gave the highest tensile strength (157 ± 14 MPa), followed by 3D woven preform-based specimen (130 ± 25 MPa), while the tensile strength of 4D-and 5D-based specimens was very low. Through this study, two carbon fibre preforms viz., 2D stitched and 3D woven are selected for realizing C/ SiC fasteners. The role of pyrocarbon interphase coating on carbon fibres, in obtaining high mechanical properties is also understood.

Effects of preform structure on microstructure and mechanical properties of long/short fiber‐coupled C/C–SiC composites

“…Among these factors, the structure of the carbon‐fiber preform significantly impacts both the mechanical properties and the densification process of C/C–SiC composites 17,18 . The orientation and volume fraction of carbon fiber directly affects the mechanical properties of the composite, with the content of long fiber bundles in the axial direction enhancing the tensile properties of C/C–SiC composites in that direction 19 . However, the impact of fiber volume fraction on other mechanical properties of C/C–SiC composites, such as flexural, compressive, and interlaminar shear properties, is not fully understood, despite their importance in practical applications.…”

“…Furthermore, the pore structure of different carbon‐fiber preforms can directly affect the densification process of C/C–SiC composites, 19 because the preparation methods of C/C–SiC composite mainly involve chemical vapor infiltration (CVI) method, precursor impregnation and pyrolysis (PIP) method, and reactive melt infiltration (RMI) method. These methods all use gaseous or liquid sources to infiltrate the porous network structure of the carbon‐fiber preform, leading to the generation of carbon and silicon carbide through thermally induced reactions 17,20,21 .…”