David N. Brewer

Ceramic Matrix Composite Combustor Liner Rig Test

The NASA High Speed Research (HSR)/Enabling Propulsion Materials (EPM) program was charged with the responsibility for developing the materials and technologies necessary to meet the High Speed Civil Transport (HSCT) engine requirements. The combustor liner was identified as a critical component for meeting the efficiency and environmental acceptability goals of the HSCT engine. The EPM Ceramic Matrix Composite (CMC) Combustor liner program was tasked with developing and demonstrating a material system and design concept that meets the HSCT environmental, thermal, structural, economic, and durability requirements. Melt Infiltration (MI) SiC/SiC composites were ultimately selected for the combustor liner application. The culmination of this development effort was the delivery and testing of a CMC combustor liner. Testing was performed at NASA Glenn Research Center in the Sector Rig under HSCT operating conditions. The initial results of the rig testing are presented.Copyright

Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions

Abstract : Ten different ceramic matrix composite (CMC) materials were subjected to a constant load and temperature in an air environment. Tests conducted under these conditions are often referred to as stressed oxidation or creep rupture tests. The stressed oxidation tests were conducted at a temperature of 1454 deg C at stresses of 69 MPa, 172 MPa and 50% of each materials ultimate tensile strength. The ten materials included such CMCs as C/SiC, SiC/C, SiC/SiC, SiC/SiNC and C/C. The time to failure results of the stressed oxidation tests will be presented. Much of the discussion regarding material degradation under stressed oxidation conditions will focus on C/SiC composites. Thermogravimetric analysis of the oxidation of fully exposed carbon fiber (T300) and of C/SiC coupons will be presented as well as a model that predicts the oxidation patterns and kinetics of carbon fiber tows oxidizing in a nonreactive matrix.

Characterization of Ceramic Matrix Composite Fasteners Exposed in a Combustor Linear Rig Test

Combustion tests on SiC/SiC CMC components were performed in an aircraft combustion environment using the rich-burn, quick-quench, lean-burn (RQL) sector rig. SiC/SiC fasteners were used to attach several of these components to the metallic rig structure. The effect of combustion exposure on the fastener material was characterized via microstructural examination. Fasteners were also destructively tested, after combustion exposure, and the failure loads of fasteners exposed in the sector rig were compared to those of as-manufactured fasteners. Combustion exposure reduced the average fastener failure load by 50% relative to the as-manufactured fasteners for exposure times ranging from 50 to 260 hours. The fasteners exposed in the combustion environment demonstrated failure loads that varied with failure mode. Fasteners that had the highest average failure load, failed in the same manner as the unexposed fasteners.

Effect of Projectile Materials on Foreign Object Damage of a Gas-Turbine Grade Silicon Nitride

Foreign object damage (FOD) behavior of AS800 silicon nitride was determined using four different projectile materials at ambient temperature. The target test specimens rigidly supported were impacted at their centers by spherical projectiles with a diameter of 1.59 mm. Four different types of projectiles were used including hardened steel balls, annealed steel balls, silicon nitride balls, and brass balls. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to better understand the severity of local impact damage. The critical impact velocity where target specimens fail upon impact was highest with brass balls, lowest with ceramic ball, and intermediate with annealed and hardened steel balls. Degree of strength degradation upon impact followed the same order as in the critical impact velocity with respect to projectile materials. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles and was correlated in terms of critical impact velocity, impact deformation, and impact load.Copyright

Characterization of Ceramic Matrix Composite Fasteners Exposed in a Combustor Liner Rig Test

NASA Glenn Research Center Cleveland, OH ABSTRACT Combustion tests on SiC/SiC CMC components were performed in an aircraft combustion environment using the Rich-burn, Quick-quench, !:ean-burn (RQL) sector rig. SiC/SiC fasteners were used to attach several of these components to the metallic rig structure. The effect of combustion exposure on the fastener material was characterized via microstructural examination. Fasteners were also destructively tested, after combustion exposure, and the failure loads of fasteners exposed in the sector rig were compared to those of as-manufactured fasteners. Combustion exposure reduced the fastener failure load by 50% relative to the as-manufactured fasteners for exposure times ranging from 50 to 260 hours. The fasteners exposed in the combustion environment demonstrated failure loads that varied with fail ure mode. Fasteners that had the highest average failure load, failed in the same manner as the unexposed fasteners. INTRODUCTION A major focus of NASAs Enabling Propulsion Materials (EPM) program was development of an advanced ceramic matrix composites (CMCs) for turbine engine combustor liners. CMCs offer great potential to improve turbine engine performance by reducing cooling requirements and NOx emissions by operating at higher temperatures than materials used for hot structures, such as Ni-base superalloys. A melt-infiltrated SiC fiber reinforced SiC matrix material (MI SiC/SiC) was the result of the collaborative efforts of NASA, General Electric, and Pratt