NASA Langley Research Center
Hampton, Virginia

Materials

	Langley Home Page
	Space Environments &Technology Archive System Home Page
	Space Environments &Effects Home Page
	NASA Home Page

If you would like to receive further information on SETAS, or have suggestions on what information you would like to see accessible through this archive, please fill out the SETAS request form. SETAS Request Information

Responsible Parties: Page Content: William H. Kinard Page Construction: Thomas H. See

As part of Materials Special Investigation Group activities, Boeing Defense and Space Group studied the various metals flown on LDEF; the MSIG summarized principal investigators' metals studies as well. The results of these efforts are contained in the report entitled Effects of Space Exposure on Metals Flown on the Long Duration Exposure Facility, NASA CR, 1995. A brief summary of this report is contained here.

Almost all composite materials flown on LDEF were test specimens. The only non-experimental specimens among the composite materials are: (1) fiberglass shims used with the wire harness clamps on the interior of LDEF, (2) the fiberglass/epoxy viscous damper shroud mounted on LDEF's interior, and (3) the outer Teflon^®/fiberglass thermal blankets covering the batteries on experiment AO138. The fiberglass shims, shielded from LDEF's exterior environment, were only exposed to vacuum and thermal cycling. Minimal analysis was performed on the shims which showed all shims remained intact. The the viscous damper shroud was intact and appeared visually to be in excellent condition post-flight. The only measurement on this hardware was a measurement of peel strength of the aluminum tape which covered the fiberglass shroud. The tape was in good condition post-flight and the peel strength was nominal. Results from testing of the two AO138 Teflon/fiberglass thermal blankets, exposed on LDEF's trailing edge (tray B03), showed some erosion of the Teflon matrix. Because of the minimal atomic oxygen exposure, the erosion was thought to be induced by the combination of UV and thermal cycling.

The recession rate of organic resin matrix materials were observed by several investigators to be substantially higher than recession rates of the graphite fibers. The lower erosion rate of the graphite fibers also causes the average recession rate for these materials on LDEF to be lower than was predicted using results from short term exposures on the Space Shuttle. Fiberglass materials exhibited behavior similar to A-276 paints. The glass fibers uncovered during atomic oxygen induced erosion of the matrix resin act as a protective barrier, as do the A-276 pigment particles on eroded A-276.

Selected composite specimens were coated to achieve protection from atomic oxygen and/or to alter the basic optical properties of the composite. These types of specimens were flown on experiments S0010 and M0003. Coatings used include sputter-coated nickel, aluminum film, SiO_x, white paints, and leafing aluminum. Each coating protected the underlying composite substrate, even though a variety of changes were visible on the white paints.

Uncoated composites lost a maximum of about one (1) ply under the worst exposure conditions. Resin materials eroded faster than the fibers. Resin material which remained was essentially unchanged in chemical properties relative to ground control specimens. Mechanical properties of flight specimens decreased in proportion to thickness loss. Trailing-edge specimens suffered no degradation of engineering performance.

Coated composites survived well; coatings as thin as 1600 angstroms protected composites on the leading edge from any mass loss. In certain cases, the coatings suffered damage and/or were degraded by the exposure, but in all cases the underlying composite material was undamaged, except for the occasional impact, and suffered no loss in mechanical properties.

LDEF Archive System Home Page