Thermal Qualification of the UHTCMCs Produced Using RF-CVI Technique with VMK Facility at DLR

Vinothini Venkatachalam,Sergej Blem,Jon Binner,Ali Gülhan

doi:10.3390/jcs6010024

Abstract

Ultra high-temperature ceramic matrix composites (UHTCMCs) based on carbon fibre (Cf) have been shown to offer excellent temperature stability exceeding 2000 °C in highly corrosive environments, which are prime requirements for various aerospace applications. In C3Harme, a recent European Union-funded Horizon 2020 project, an experimental campaign has been carried out to assess and screen a range of UHTCMC materials for near-zero ablation rocket nozzle and thermal protection systems. Samples with ZrB2-impregnated pyrolytic carbon matrices and 2.5D woven continuous carbon fibre preforms, produced by slurry impregnation and radio frequency aided chemical vapour infiltration (RF-CVI), were tested using the vertical free jet facility at DLR, Cologne using solid propellants. When compared to standard CVI, RFCVI accelerates pyrolytic carbon densification, resulting in a much shorter manufacturing time. The samples survived the initial thermal shock and subsequent surface temperatures of >2000 °C with a minimal ablation rate. Post-test characterisation revealed a correlation between surface temperature and an accelerated catalytic activity, which lead to an understanding of the crucial role of preserving the bulk of the sample.

Highlights

The recent return of supersonic flight to aviation could significantly shorten longhaul flight times [1,2,3,4,5]
This paper focuses on a route to Cf -ultra-high temperature ceramic-matrix composites (UHTCMCs) that involved the tailored slurry impregnation of carbon fibre preforms with zirconium diboride (ZrB2 ) with the remaining porosity being filled with pyrolytic carbon using the relatively low temperature (~1000 ◦ C), near net-shape, chemical vapour infiltration (CVI) process) [3,17]
The resulting ZrB2 impregnated preforms were densified with pyrolytic carbon (PyC) using radio frequency aided chemical vapour infiltration (RF-CVI) with heating provided by an EasyHeat induction furnace operating at 4.2 kW maximum power in the frequency range of 150–400 kHz

Summary

Introduction

The recent return of supersonic flight to aviation could significantly shorten longhaul flight times [1,2,3,4,5]. The leading edges of these vehicles, as well as the nozzles of solid or hybrid rocket motors, must resist the harsh temperature, chemical and mechanical environments created by high-performance solid propellants to be commercially successful [6,7]. A modern group of materials, the ultra-high temperature ceramic-matrix composites (UHTCMCs), are a new subfield within the broader grouping of ceramic matrix composites and are potential candidates for such applications [8]. They combine the benefits of CMCs, such as high-temperature strength and stiffness, low specific weight and damage tolerance with oxidation and ablation resistance at extreme temperatures, e.g., >2000 ◦ C [9]. The processing and engineering of these UHTCMCs is very challenging,

Methods

Discussion

Conclusion