Engineering topics

Wohl, C. J.

Publications and source records attributed to Wohl, C. J..

4 records

NASA NTRS2020

Patch Plate Materials Compatibility Assessment

Lunar dust proved to be a greater problem during the Apollo missions than was originally anticipated. The highly angular, charged dust particles stuck to seals, radiators, and visors; clogged mechanisms; and abraded space suits. As reported by Apollo 12 astronaut Pete Conrad "We must have had more than a hundred hours suited work with the same equipment, and the wear was not as bad on the training suits as it is on these flight suits in just the eight hours we were out.". Dust clinging to surfaces was also transport-ed into habitable spaces leading to lung and eye irritation of the astronauts. The Apollo astronauts were on the Lunar surface less than 24 hours and experienced many dust related problems. With the Artemis program, we are planning longer stays on the surface, with more activities that have the potential to put the astronauts and equipment in contact with greater quantities of Lunar dust. The success of these missions will depend on our understanding of material interactions with Lunar dust and the development of ways to mitigate dust effects in cases where exposure to dust will lead to failure of components, unacceptable loss of power or thermal control, unacceptable loss of visibility, or health issues. Through the Lunar Surface In-novation Initiative (LSII), we are initiating a Patch Plate Materials Compatibility Assessment project. The overall goal of the three year project is to develop passive approaches to mitigate Lunar dust adhesion to surfaces for technologies that are currently at TRL levels 2-3 to bring them to TRL level 5 through ground-based assessment, culminating in a demonstration flight experiment on a Commercial Lunar Payload Services (CLPS) lander in 2022-2023. This paper discusses the detailed technical objectives and approach for this project. References: Gaier, J.R. "The Effects of Lunar Dust on EVA Systems During the Apollo Missions," NASA/TM-2005-213610/REV1, (2005), Apollo 12 Technical Crew Debriefing, December 1, 1969, pp. 10-54.

Miller, S. K. R.↗

NASA NTRS2010

Laser Surface Preparation for Adhesive Bonding of Aerospace Structural Composites

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical pre-bonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

Belcher, M. A.↗

NASA NTRS2010

Laser Surface Preparation and Bonding of Aerospace Structural Composites

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical prebonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

Belcher, M. A.↗

NASA NTRS2008

Oxygen Plasma Modification of Poss-Coated Kapton(Registered TradeMark) HN Films

The surface energy of a material depends on both surface composition and topographic features. In an effort to modify the surface topography of Kapton(Registered TradeMark) HN film, organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), were spray-coated onto the Kapton(Registered TradeMark) HN surface. Prior to POSS application, the Kapton(Registered TradeMark) HN film was activated by exposure to radio frequency (RF)-generated oxygen plasma. After POSS deposition and solvent evaporation, the films were exposed to various durations of RF-generated oxygen plasma to create a topographically rich surface. The modified films were characterized using optical microscopy, attenuated total reflection infrared (ATR-IR) spectroscopy, and high-resolution scanning electron microscopy (HRSEM). The physical properties of the modified films will be presented.

Wohl, C. J.↗