The Fabrication and Performance of Cost-Effective C/C Composites Using Low-Pressure Re-Impregnation and Pyrolysis

Abstract

Carbon-carbon (C/C) composites exhibit considerable promise for hypersonic, rocket, aero and gas turbine engine applications, yet their fabrication can be challenging and costly due to extended processing times and other factors. In this study, we present an innovative and costefficient approach that leverages low-pressure mesophase pitch re-impregnation and pyrolysis for synthesising C/C composites. Our investigation encompasses a multi-faceted analysis: Optical microscopy and image processing software are employed to evaluate the microstructures of the fabricated material, thermogravimetric analysis (TGA) is used to assess material weight loss during pyrolysis, and Raman spectroscopy is utilised to analyse graphitic crystallinity. Furthermore, we examine the C/C composite’s flexural strength and ablation rates through three-point bend testing and exposure to an oxyacetylene flame torch, respectively. After three low-pressure densification cycles, we achieve a material bulk density of 1.62 ± 0.1 g/cm3, resulting in average flexural and short beam strengths of 126 ± 6 and 8.0 ± 0.5 MPa, respectively. A heat flux of 3 MW/m2 for two minutes resulted in a linear ablation rate of 0.0016 ± 0.0001 mm/s. These findings collectively underscore the feasibility of cost-effective C/C composite fabrication for demanding aerospace and engine technologies.

Keywords: C/C composite, fabrication, ablation, mesophase pitch