Accession Number : ADA188000

Title :   Ultra-Low Expansion Metal Matrix Composites.

Descriptive Note : Final rept. 4 Aug 78-30 Sep 80,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR MFG AND PRODUCTIVITY

Personal Author(s) : Suh, Nam P ; Saka, Nannaji ; Boustani, Joseph

PDF Url : ADA188000

Report Date : Apr 1981

Pagination or Media Count : 141

Abstract : The satisfactory performance of mirror substrates of High Energy Large Optics (HALO) and High Energy Laser Optics (HELO) requires that the distortion of these substrates (due to temperature variations) be less than 0.1 um per meter (ideally zero thermal expansion) in the temperature range 150-300L. In addition they should have high thermal conductivity, high microyield strength and low density. Moreover, they should be extremely resistant to outgasing. A thermoelastic analysis has been carried out to compute the coefficient of thermal expansion (CTE). Exact equations for stresses, strains and CTE have been derived for a two phase composite. The results indicate that the thermal expansion coefficient of the composite is a sensitive function of the CTE's of the constituent phases and insensitive to the elastic moduli of Poisson's ratios. It is shown that to produce ultra low to zero CTE materials two phases, one with low positive CTE and the other with large negative CTE, are required. Further, the amount of the matrix and dispersed phases should be controlled to within a few percent.

Descriptors :   *METAL MATRIX COMPOSITES, THERMAL EXPANSION, DISPERSING, PHASE, MODULUS OF ELASTICITY, HIGH ENERGY, OPTICS, YIELD STRENGTH, LOW DENSITY, DISTORTION, EQUATIONS, LASERS, OPTICS, CONDUCTIVITY, THERMAL CONDUCTIVITY, PHASE TRANSFORMATIONS, THERMOCLINES, CERAMIC MATERIALS, VAPORIZATION, POWDER METALS, NICKEL, NIOBATES, BONDING

Subject Categories : Laminates and Composite Materials
      Optics
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE