Cratering and penetration experiments in Teflon targets at velocities from 1 to 7 km/s

Conference · Wed Feb 01 04:00:00 EST 1995

OSTI ID:42764

Hoerz, F; Bernhard, R P; Cintala, M J; See, T H ^[1]

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1. Lockheed Engineering and Sciences Co., Houston, TX (United States)

Approximately 20 sq m of protective thermal blankets, largely composed of Teflon, were retrieved from the Long Duration Exposure Facility (LDEF) after the spacecraft had spent approximately 5.7 years in space. Examination of these blankets revealed that they contained thousands of hypervelocity impact features ranging from micron-sized craters to penetration holes several millimeters in diameter. The authors conducted impact experiments in an effort to reproduce such features and to -- hopefully -- understand the relationships between projectile size and the resulting crater or penetration-hole diameter over a wide range of impact velocity. Such relationships are needed to derive the size- and mass-frequency distribution and flux of natural and man-made particles in low-Earth orbit. Powder propellant and light-gas guns were used to launch soda-lime glass spheres of 3.175 mm (1/8 inch) nominal diameter (Dp) into pure Teflon FEP targets at velocities ranging from 1 to 7 km/s. Target thickness (T) was varied over more than three orders of magnitude from infinite halfspace targets (Dp/T less than 0.1) to very thin films (Dp/T greater than 100). Cratering and penetration of massive Teflon targets is dominated by brittle failure and the development of extensive spall zones at the target`s front and, if penetrated, the target`s rear side. Mass removal by spallation at the back side of Teflon targets may be so severe that the absolute penetration-hole diameter (Dh) can become larger than that of a standard crater (Dc) at relative target thicknesses of Dp/T = 0.6-0.9. The crater diameter in infinite halfspace Teflon targets increases -- at otherwise constant impact conditions -- with encounter velocity by a factor of V0.44. In contrast, the penetration-hole size in very thin foils (Dp/T greater than 50) is essentially unaffected by impact velocity. Penetrations at target thicknesses intermediate to these extremes will scale with variable exponents of V.

• Research Organization: National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center
• OSTI ID: 42764
• Report Number(s): N--95-23796; NASA-CP--3275-PT-1; L--17430A-PT-1; NAS--1.55:3275-PT-1; CONF-9311137--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRATERS
IMPACT SHOCK
IMPACT TESTS
PARTICULATES
PHYSICAL RADIATION EFFECTS
SPACE VEHICLE COMPONENTS
SPALLATION
TEFLON
THERMAL INSULATION
THIN FILMS