Glenn Research Center at Lewis Field 1 STANDARDIZATION EFFORTS FOR MECHANICAL TESTING AND DESIGN OF ADVANCED CERAMICS AND COMPONENTS NES Working Group Meeting September 2004 NASA GRC Jon Salem NASA GRC

Glenn Research Center at Lewis Field 2 OUTLINE  Standards Being Developed Under NTSP: - Machining Practices for Ceramics - Determination of Slow Crack Growth Parameters  Motivations: - Failure of a leading edge - Failure of a sapphire solar concentrator - Test specimens for a combustion facility window  Status & Related Standardization Efforts in ASTM C28, ISO TC206, and NASA GRC

Glenn Research Center at Lewis Field 3 FAILURE OF A LEADING EDGE  Sharp Leading Edges are Needed : - maneuverability - aerodynamics - Re-entry vehicles - airframes  Issues : - higher edge temperatures - more oxidation, etc.  Candidate Materials are UHTC’s (Ultra-High Temperature Ceramics)

Glenn Research Center at Lewis Field 4 FAILURE OF A LEADING EDGE  Testing of UHTC Edge Segments Resulted in Failures: Failed test component showing thermocouple hole.  Bad design or a more basic issue? 2 mm

Glenn Research Center at Lewis Field 5 FAILURE OF A LEADING EDGE  Fractographic investigations indicate that the thermocouple hole was poorly machined: Crack network on inside walls of the thermocouple hole.  Could standards have prevented the failure? 10 m m

Glenn Research Center at Lewis Field 6 FAILURE OF A LEADING EDGE  Holes were made via electro-discharge machining.  EDM results in localized surface damage.  No EDM guidelines for ceramics.  Machining techniques in current standards are test specimen specific (e.g. flexure beams).  Literature indicates that other techniques with follow-up treatment could eliminate machining damage.  Need for machining guidelines.

Glenn Research Center at Lewis Field 7 TEST SPECIMENS FOR A COMBUSTION FACILITY WINDOW Space Station Fluids and Combustion Facility Combustion Integrated Rack:  Mission - Supports a wide range of microgravity combustion investigations.

Glenn Research Center at Lewis Field 8 BACKGROUND Combustion Chamber and Subsystems Fuel/Oxidizer Management Assembly (FOMA) Gas Distribution Exhaust Vent Optics Bench Combustion Chamber Rack Closure Door** SAMS RTS** Active Rack Isolation Subsystem (ARIS)* Environmental Control (ECS) Air Thermal Control** Fire Detection* & Suppression** Water Thermal Control** Gas Interfaces (GN2, VES, VRS)** Input/Output Processor (IOP)** Experiment Specific Chamber Insert Optics Bench Slides** Window Section 4”

Glenn Research Center at Lewis Field 9 TEST SPECIMENS FOR A COMBUSTION FACILITY WINDOW  Window is required to transmit 1 to 5 micron IR.  Candidate material is sapphire.  Two sets of test specimens were made according to commonly used scratch-dig specification.  Testing indicated minimal scatter in one test set and substantial scatter in the other set.

Glenn Research Center at Lewis Field 10 TEST SPECIMENS FOR A COMBUSTION FACILITY WINDOW  Strength and crack growth test results:  Too much scatter to determine crack growth parameters. R-plane setA-plane set Stress Rate,, MPa/s

Glenn Research Center at Lewis Field 11 TEST SPECIMENS FOR A COMBUSTION FACILITY WINDOW  X-ray topography indicate subsurface damage and a “short finish” in one test sets:  Could standards have reduced the scatter? 4 mm 0.20 mm

Glenn Research Center at Lewis Field 12 TEST SPECIMENS FOR A COMBUSTION FACILITY WINDOW  Scratch-dig specifications do not require removal of damage created during previous polishing stage.  Sufficient removal reduces damage from the early polishing stages:  Guidelines requiring stages of removal should help!  Also, a standard for SCG parameters is needed.

Glenn Research Center at Lewis Field 13 STATUS  SCG Parameters Standard: - Balloted in spring (ASTM) - Re-ballot in November  Machining Guide: - draft completed - Needs to be put in the new format

Glenn Research Center at Lewis Field 14 NASA-RELATED STANDARDS for ADVANCED CERAMICS  ASTM Standards NASA Helped Develop: C Practice for Fabricating Ceramic Reference Specimens Containing Seeded Voids C1239 – 95 Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters C Test Method for Determination of Slow Crack Growth Parameters by Constant Stress-Rate Testing C Test Methods for the Determination of Fracture Toughness of Advanced Ceramics C Test Method for Monotonic Equibiaxial Flexural Strength Testing Of Advanced Ceramics Above Standards used for SSME bearings, FEANICS windows, FCF windows.

Glenn Research Center at Lewis Field 15 Potential Future Work  Standards of Interest to NASA & ASTM:  Determination of the inert strength.  Determination of elevated temperature fracture toughness (proposed).  Determination of elevated temperature monotonic equibiaxial strength.  Equibiaxial strength of very thin plates (fuel cells and substrates).

Glenn Research Center at Lewis Field 16 SUMMARY  Many NASA missions use advanced ceramic materials (ISS, SSME, RSC).  Standards for advanced ceramics have been and are being developed by NASA, ASTM, and ISO.  A need exists for the development of new standards for advanced ceramics and ceramic composites.