No abstract

The Young's and shear moduli of arc-cast zirconium carbidegraphite alloys were measured as a function of graphite content and were found to depend strongly on the microstructure of the alloys. Attempts to fit several theoretical analyses to the data were unsuccessful. The simplified physical models from which these analyses were derived limit their usefulness in predicting elastic behavior for materials having complex microstructures.

The effect of exposure to the laboratory atmosphere on the fracture stress and Young's modulus of polycrystalline magnesium oxide was studied. The observed degradation of mechanical properties was attributed to chemical attack by atmospheric water vapor. The rate and extent of degradation depended on the amount and nature of porosity in the specimens. 2 2600 9 1

Young's and shear moduli of MgO-pore and MgO-nickel-pore composites were measured at low concentrations of the included phases. The effect of these phases was greater than was predicted from theory. The deviation of the experimental data from theory was explained on the basis of the shape of the included phases. The Young's and shear moduli for fully dense MgO were 3060 and 1305 kbars, respectively.

This technical documentary report has been reviewed and is approved for publication and dissemination. The conclusions and findings contained herein do not necessarily represent an official Air Force position.