Masahiro Sato

Combustion Gas Heating Tests of C/C Composites Coated with SiC Layer

In order to examine the applicability of carbon fiber/carbon matrix composites coated with a silicon carbide layer (C/C‐SiCs) to an advanced nozzle for the future reusable rocket engines, two series of combustion gas heating tests were conducted using a small rocket combustor. In the first series of heating tests, five different kinds of C/C‐SiCs were tested with specimens in the shape of a square plate for material screening. In the second series of heating tests, two selected C/C‐SiCs were tested with specimens in the shape of a small nozzle. The effectiveness of an interlayer between a C/C composite and a SiC layer, which was introduced to improve the durability based on the concept of functionally graded materials (FGMs), can be observed. The typical damage mode was also pointed out in the results of heating test using the small nozzle specimens.

Performance and damage evaluation of a regeneratively cooled thrust engine coated with ZrO2/Ni functionally graded materials (evaluation test results of a chamber partially coated with ZrO2/Ni FGM made by the electroforming method)

A combustion chamber partially coated with ZrO 2 /Ni functionally graded materials (FGM) was cyclically tested, using a bipropellant of nitrogen tetroxide (NTO)/ monomethyl hydrazine (MMH) at a chamber pressure (P c ) of 0.9 MPa, to show the effect of such coatings on the life span of the chamber. This thermal barrier coatings were applied using a process that employed the electroforming method. The C * efficiency (ηC * ) for the durability tests of the partially ZrO 2 /Ni FGM-coated chamber was 97% at P c =0.9 MPa and mixture ratio (MR) of NTO/MMH=1.65. At the cylindrical section of the chamber, the thermal barrier coating subsequent to composed of pure ZrO 2 remained partially intact. However, the inner surface coating of the chamber throat section suffered premature delamination. The typical damage mode observed in a carbon fiber-reinforced carbon matrix (C/C) chamber of a bipropellant engine in our previous study was also seen near the injector face. In the cycle durability tests, the damage to the coating was inspected by means of the Replica method. After a total of 260 firing tests, a profile of the coating damage was obtained by means of a computer-aided micro-analyzer (CMA) system.