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  • 1
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    Glass fiber addition strengthens low-density ablative compositions (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Approximately 15% of E-glass fibers was added to compositions under test and greatly improved char stability. Use of these fibers also reduced thermal strains which, in turn, minimized char shrinkage and associated cracks, subsurface voids, and disbonds. Increased strength allows honeycomb core reinforcement to be replaced by equivalent amount of glass fibers.
    Keywords: MATERIALS
    Type: LAR-11288
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Investigation of forming curved ablative panels from flat panels for space shuttle (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The purpose of this study was to determine the feasibility of reforming flat ablative panels to a curved configuration. The study indicated that if the panels could be shaped to a radius of 2.54 m (100 in.) then 88.7% of the surface area of the orbiter could be covered, and that if they could be shaped to a radius of 3.81 m (150 in.) then 77.2% of the surface could be covered. Two basic approaches were followed to determine the best method for forming the flat panels to a curved shape. The first was to determine if partially cured panels could be formed, allowing the forming heat cycle to complete the curing of the ablator. The second method was to form fully cured flat panels into the desired curvature through a secondary heat cycle. Measurements made on the panels during storage indicated that they continued to straighten out over time. This was attributed to residual stresses locked into the panels that had not been fully relaxed by the heat cycle.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-CR-112135 , MCR-72-188
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Investigation of low-cost ablative heat shield fabrication for space shuttles (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Improvements in the processes and design to reduce the manufacturing costs for low density ablative panels for the space shuttle are discussed. The areas that were studied included methods of loading honeycomb core, alternative reinforcement concepts, and the use of reusable subpanels. A review of previous studies on the fabrication of low-cost ablative panels and on permissible defects that do not affect thermal performance was conducted. Considerable differences in the quoted prices for ablative panels, even though the various contractors had reported similar fabrication times were discovered. How these cost differences arise from different estimating criteria and which estimating assumptions and other costs must be included in order to arrive at a realistic price are discussed.
    Keywords: MACHINE ELEMENTS AND PROCESSES
    Type: NASA-CR-112045 , MCR-72-51
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Low-cost ablative heat shields for space shuttles (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Low cost replaceable ablative heat shield panels for space shuttles
    Keywords: SPACE VEHICLES
    Type: NASA-CR-111800
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
    Electronic Resource
    Electronic Resource
    Development of a radiopaque denture base material (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 253-265 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Radiopaque glass-resin composites were made for evaluation as denture base materials. The addition of silane-treated, radiopaque, powdered glass to clear poly(methyl methacrylate) resulted in composites that had greater optical translucency than commercially available pink denture base resins. These formulations could be pigmented and opacified to produce materials that simulated oral soft tissues in color and translucency.Other composites were made using various monomer, polymer and glass combinations. Those made from mixes of BIS-GMA, methyl methacrylate, poly(methyl methacrylate), and radiopaque glass had excellent translucency but handling characteristics were less than ideal.Removal of very small glass particles (less than a few μm) appeared to improve optical translucency.A radiographic survey of 12 specimens that contained from 29 to 57% of the radiopaque glass, indicated that all had sufficient radiopacity to aid in localization of swallowed or aspirated dentures made from such materials.Finishing procedures on composite specimens were more difficult and timeconsuming and did not produce surfaces as smooth as those obtained on poly(methyl methacrylate). The finished surfaces felt smooth to the tongue but might stain more easily in the mouth.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050312
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The need for radiopaque denture base materials: A review of the literature (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 245-252 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for esthetic and functionally acceptable radiopaque denture base materials is reflected by numerous reports of patients who ingested or aspirated portions of dentures and reports of difficulties encountered in the removal of these dentures because they could not be located radiographically.The type of denture most commonly ingested or aspirated is a maxillary partial consisting of a palatal piece to which is attached one or more anterior teeth. It may or may not have clasps. Ingestion or aspiration of the foreign body commonly occurs when either broken or ill-fitting dentures are being worn. Few cases have been reported where patients swallowed portions of complete dentures.Previous attempts at providing radiopacity have included addition of heavy metal salts or radiopaque inserts to denture base resins. None of these attempts has been entirely successful.Elimination of dentures as foreign bodies requires a greater effort toward preventive measures by the dentist and the patient. When dentures are swallowed or inhaled, the dentist should immediately seek medical assistance for the patient. The common symptomless period following ingestion or aspiration should not lead the dentist to believe that there will not be serious subsequent complications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050311
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Physical properties of a radiopaque denture base material (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 335-357 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Physical properties were determied for radiopaque composite denture base materials consisting of poly (methyl methacrylate) as thematrix and 30, 40, and 50% by weight fo a singlane-treated barum fluoride-containing glass powder as the reinforcing filler. Specimens without glass were include for comparision.All of the materials met the requirements of Amerrican ental Association Specification No. 12 for Denture Base Polymer except that t6he material containing 50% glass had less deflection than the minimum required at the 5000-gm load in transverse testing.There was little or no difference among thematerials with respect to hardness, in denation resistance, water sorption, color stability, and resistance to drop impact.Addition of glass of the 30% level decreased the transevers strenght while 50% means with no glass. In general, the addition of glass increased the time to reach only slight effect on densities, and Young's, bulk, shear, and flexural moduli, had only slight effect on solubility and decreased the cold-cure repairability and the coefficient of linear thermal expanision.The solubility of the glass power was aboutfour times that of powdered porcelain teeth after 24 hr, and totaled 0.55% afeter 5 days.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050406
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  • 8
    Electronic Resource
    Electronic Resource
    Radiopaque denture base materials technic dentures (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 359-371 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Technic dentures were made using composite base materials containing 30,40, and 50 weight % of a silance-treated, readiopaque, powdered glass as the reinforcing filler and poly (methyl methacrylate) as the matrix. Dentures containing no glass were included for comparison. Molar-to-molar dimensional changes, effects of silance treatment fo the procelain teeth and handling and finishing characteristics were determined.Dentures containing glass had less dimensional change during curing and subsequent water storage than those without glass. Thick upper dentrues exhibited the least change and thin lowers, the most. The Differences in the magnitudes of the changes would not be clinically noticeable.Silance treatment fo the procelain teeth in thick upper dentures resulted in breakage of theposterior teeth in almost all instances. posterior teeth also freactured in thick upper dentures containing 40 and 50% of the silance-treated glass even though the teeth were not treatedwith silance.Mixing and molding properties of the composite materials, while acceptabgle, were slightly inferior to thematerial containing ono glass. Finiching characteristics were definitelyinferior in that it was more difficult and time-consuming to attain the fial surfaces and these surfaces were not as smooth as smooth as those in dentures without glass.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050407
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