Engineering topics
Publications and source records attributed to Hunter, A. B..
Characterization of model compounds, monomers, resin solutions and cure cycles of PMR-15 polyimide are performed. Successful separation of various reaction products is also accomplished by liquid chromatography. The PMR-15 cure analysis is performed by fourier transform spectroscopy and gas chromatograph - mass spectrometry. Characterization receiving inspection tests for Quality Control are recommended.
Quality assurance methods for graphite epoxy/prepregs were developed. Liquid chromatography, differential scanning calorimetry, and gel permeation chromatography were investigated. These methods were applied to a second prepreg system. The resin matrix formulation was correlated with mechanical properties. Dynamic mechanical analysis and fracture toughness methods were investigated. The chromatography and calorimetry techniques were all successfully developed as quality assurance methods for graphite epoxy prepregs. The liquid chromatography method was the most sensitive to changes in resin formulation. The were also successfully applied to the second prepreg system.
Controls on the PMR-15 resin and/or prepreg were established to ensure a solid base for the subsequent process development task. The effort was divided into subtasks which included evaluation of commercially available graphite/PMR-15 polyimide prepregs, detailed evaluation of materials and selection of chemical test procedures. During the initial phase of the program a variability problem was detected in the PMR-15 resin. The manufacturing and/or storage of the PMR-15 resin/esters was identified as the chief cause for the variability.
The work included establishing controls on the polymer, the prepreg, composite fabrication, and quality assurance, as well as fabrication of structural elements to demonstrate the developed materials and processes. The fabricated structures were hat sections, I-beam sections, honeycomb sandwich structures, and molded graphite-reinforced fittings. The graphite/PMR-15 polyimide system was shown to be well suited for use in the 550-600 F temperature range; the processing techniques developed were proved and found potentially useful for other commercially available systems.
Investigation was made into the reproducibility of PMR polyimide/graphite prepreg reinforcement and the influence of these variabilities on processing characteristics and final composite properties. The purpose of these investigations was to establish specification controls and limits of acceptance/rejection on incoming materials. Prepreg samples were chemically analyzed and the results compared to the processing and property results of the resulting composites. The findings from these comparisons are discussed.
The space support equipment that supports the lunar roving vehicle during the flight to the moon and permits the vehicle to be deployed from the lunar module onto the lunar surface with a minimum amount of astronaut participation is discussed. The design and evolution of the equipment are reviewed. The success of the overall lunar roving vehicle design, including the space support equipment, was demonstrated on the Apollo 15 and 16 missions.