The Design Space of Superalloy-Based Actively Cooled Combustor Walls for H2-Powered Hypersonic Vehicles

2007 ◽  
Author(s):  
Lorenzo Valdevit ◽  
Natasha Vermaak ◽  
Frank W. Zok ◽  
A. G. Evans
Keyword(s):  
Design Space ◽  
Ceramic Matrix Composites ◽  
Nickel Superalloy ◽  
Hypersonic Vehicles ◽  
Matrix Composites ◽  
Niobium Alloys ◽  
Design Constraint ◽  
Mechanical Loads ◽  
Nickel Copper ◽  
Wide Range

The walls of combustion chambers used for air-breathing hypersonic vehicles are subject to substantial thermo-mechanical loads, and require active cooling by the fuel in conjunction with advanced material systems. Solutions based on metallics are preferable to ceramic matrix composites due to their lower cost and greater structural robustness. Previous work suggested that a number of metallic materials (e.g. Nickel, Copper and Niobium alloys) could be used to fabricate actively cooled sandwich structures that withstand the thermo-mechanical loads for a Mach 7, hydrocarbon-powered vehicle (albeit with different weight efficiencies). However, this conclusion changes when the Mach number is increased. This work explores the feasibility of the Nickel superalloy MARM246 for a wide range of Mach numbers (7–12). Since hydrocarbon fuels are limited to Mach 7–8, Hydrogen is used as the coolant of choice. A previously derived analytical model (appropriately modified for gaseous coolant) is used to explore the design space. The relative importance of each design constraint is assessed, resulting in the distillation of essential guidelines for optimal design.

ANALYSIS OF CERAMIC MATRIX COMPOSITES WITH BRIDGING CRACKS IN THE PRESENCE OF CREEP

1998 ◽  
Vol 22 (4B) ◽  
pp. 447-456
Author(s):  
V. Birman ◽  
L.W. Byrd
Keyword(s):  
Thermal Stresses ◽  
Tensile Load ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Effect Of Temperature ◽  
Uniaxial Tensile ◽  
Matrix Composites ◽  
Mechanical Loads ◽  
Aerospace Applications ◽  
Matrix Cracks

Ceramic matrix composites (CMCs) represent an attractive class of materials, particularly in aerospace applications where a combination of thermal and mechanical loads may present a challenge for a designer. An important feature of these materials is their ability to withstand damage without immediate failure. This emphasizes a significance of studies of damaged CMCs, particularly at high temperatures. In particular, the analysis of creep of CMCs with matrix cracks is important to accurately predict the response and reliability of such materials. The solution presented in this paper concentrates on creep in the presence of bridging cracks and uniaxial tensile load. Residual thermal stresses and the effect of temperature on the rate of creep are incorporated into the formulation.

Mechanical Behavior of Notched SiC/SiC Composites

2001 ◽  
Author(s):  
Gregory N. Morscher ◽  
John Z. Gyekenyesi ◽  
Andrew L. Gyekenyesi
Keyword(s):  
Stress Concentration ◽  
Gas Turbines ◽  
High Stress ◽  
Thermoelastic Stress ◽  
Ceramic Matrix Composites ◽  
Matrix Cracking ◽  
Notch Sensitivity ◽  
Matrix Composites ◽  
High Stress Concentration ◽  
Wide Range

Gas turbine components such as combustor liners or turbine vanes are subject to regions of high stress-concentration, e.g. attachment to the frame or at cooling holes. Ceramic matrix composites (CMCs) are potential materials for high temperature applications in gas turbines. They offer some capability to relieve stress at regions of high stress-concentration via matrix damage accumulation. In this study notch sensitivity was examined for woven SiC fiber reinforced, melt-infiltrated SiC matrix composites with a BN interphase, utilizing either Hi-Nicalon™ fibers or the stiffer Sylramic® fibers. The double-edge notched tensile test approach was used for a wide range of notch sizes and specimen widths. Both composite systems exhibited mild notch sensitivity similar to other CMC systems. Acoustic emission, detected during the tensile tests, indicated that matrix cracking occurred around notches at net-section stresses below the stress where matrix cracking first occurs in unnotched specimens. However, thermoelastic stress analysis did not show any measurable stress relief around notches after the specimens were preloaded.

A TEM investigation of silicon nitride whiskers

1987 ◽  
Vol 45 ◽  
pp. 160-161
Author(s):  
Tapan Roy
Keyword(s):  
Silicon Nitride ◽  
High Resolution ◽  
Ceramic Matrix Composites ◽  
High Resolution Electron Microscopy ◽  
Molten Silicon ◽  
Matrix Composites ◽  
Ceramic Fibers ◽  
Resolution Electron ◽  
Point To Point ◽  
Technological University

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.

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