Engineering topics

Smiser, L. W.

Publications and source records attributed to Smiser, L. W..

8 records

NASA NTRS1986

Attaching Metal Fasteners to Silica Tiles

Stress distributed so high load borne. Fastener bonded in densified hole or captured in plug of similar refractory material, which in turn bonded in hole in parent tile. Plug or bonding distributes mechanical load from fastener to broad region surrounding fastener, reducing local stress concentration and likelihood of breakage. Bonded-plug method has been successful in attaching mechanical fasteners to porous silica refractory tiles used on outer surface of Space Shuttle orbiter.

Holt, J. W.↗

NASA NTRS1985

Bonding Heat-Resistant Fabric to Tile

Acid etching, densification, and silica cement ensure strong bond. Key step in preparation for bonding to glazed tile is etching quartz fabric and tile with acid. This increases adhesion of silica cement used to form bond. Procedures use high-temperature materials exclusively and therefore suitable for securing flexible seals and heat barriers around doors and viewing ports in furnaces and kilns.

Holt, J. W.↗

NASA NTRS1983

Improving Surface Strength of Insulating Tiles

Procedure for improving tile resistance to impact damage described in new report on tile densification. Developed for Space Shuttle reusable surface insulations, procedure has potential application when space restrictions necessitate thin layers of insulation with low thermal conductivity. Examples are advanced heat engines, such as adiabatic diesel and automotive gas turbine, as well as fast-heating high-temperature ovens.

Holt, J. W.↗

NASA NTRS1982

Method for repair of thin glass coatings

A method of repairing cracks or damaged areas in glass, in particular, glass coatings provided on tile. The method includes removing the damaged area using a high speed diamond burr drilling out a cavity that extends slightly into the base material of the tile. All loose material is then cleaned from the drilled out cavity and the cavity is filled adjacent the upper surface of the coating with a filler material including chopped silica fibers mixed with a binder. The filler material is packed into the cavity and a repair coating is applied by means of a brush or sprayed thereover. The repair includes borosilicate suspended in solution. Heat is applied at approximately 2100 F. for approximately five minutes for curing the coating, causing boron silicide particles of the coating to oxidize forming a very fluid boron-oxide rich glass which reacts with the other frits to form an impervious, highly refractory layer.

Holt, J. W.↗

NASA NTRS1981

Porous tooling process for manufacture of graphite/polyimide composites

A porous tooling system was selected for the processing of Graphite/PMR-15 Polyimide laminates in thickness up to 3.2 mm. (0.125 inch). This tool system must have a reasonable strength, permeability dimensional stability, and thermal conductivity to accomplish curing at 600 F and 200 psi and 200 psi autoclave temperature and pressure. A permeability measuring apparatus was constructed and permeability vs. casting water level determined to produce tools at three different permeability levels. On these tools, laminates of 5, 11, and 22 plies (.027, .060, and 0.121 inch) were produced and evaluated by ultrasonic, mechanical, and thermal tests to determine the effect of the tool permeability on the cured laminates. All tools produced acceptable laminates at 5 and 11 plies but only the highest permeability produced acceptable clear ultrasonic C-Scans. Recommendations are made for future investigations of design geometry, and strengthening techniques for porous ceramic tooling.

Smiser, L. W.↗

NASA NTRS1975

Fundamental studies on the nature and properties of ceramic fiber insulation

Silica and mullite fibers used to fabricate reusable surface insulation (RSI) for the space shuttle orbiter may devitrify/recrystallize within the temperature range anticipated upon reentry. This is shown to be dependent upon impurity level, temperature, and time at temperature. It is determined that the effects of the material improvement and optimization program are positive. The degree of crystallinity is shown to have a predominant effect upon the strength of fabricated RSI tile, and limits are determined. Models are developed to predict tensile strengths and shrinkage rates of silica tile based upon readily measurable parameters. Thermal cycling which simulates reentry results in an increase in the crystallinity and in the porosity of tile coatings.

Mueller, J. I.↗

NASA NTRS1973

Pore Structure Analysis of RSI Tile

Mercury porosimetry gives a means of characterizing RSI tile pore structure in terms of porosity, pore size distribution, bulk density, specific surface area, mean pore diameter, and mean fiber diameter. It also allows the determination of the effects of heat treatment on these parameters. It is limited in application to open-pored structures, however, since any closed pore volume is ignored.

Whittemore, O. J., Jr.↗

NASA NTRS1973

Characterization of RSI coating

X-ray diffraction analyses on mullite, silica, and ceramic mullite fiber coating materials to investigate the effects of thermal cycling, show that ceramic mullite fiber coating porosity is little affected by cycling to 1250 C and that material pores are mostly smaller than 15 nm. Some mullite coatings experience a slight increase in crystobalite with somewhat increased porosity. Silica coatings show a marked tendency to precipitate cristobalite with increased porosity and dimensional instability.

Miller, A. D.↗