Equation-of-state data at extremely high pressure is required for the analysis of many problems pertaining to physics, geophysics, astrophysics, etc. The conventional method used to obtain such data is to impact one flat plate of material against another flat plate at a very high velocity. A shock wave is thus produced in the target plate and the pressure can be deduced by measuring the impact velocity and the shock velocity. American, Russian, and British researchers have used explosive to propel the driver plate to velocities of about 5 km/sec; however, the Russians do not indicate how they accelerate their driver plates for their highest velocities (14–15 km/sec). The present paper describes an experimental technique in which a 20-mm light-gas gun has been used to accelerate a driver plate against a target at velocities up to 8 km/sec. Tests have been conducted using Fansteel 77 drivers, and Hugoniot data have been obtained for Fansteel 77, tungsten, and gold to about 6-Mbar pressure. The technique is very attractive in that x-ray photographs show that the driver plate is not deformed just prior to impact and has an angle of attack less than 0.5 deg. Also, an analysis of all possible errors in measurement of impact velocity, shock velocity, etc. shows that, with the present technique, Hugoniot data can be obtained to an accuracy of about 1%.

c ONSIDERING T H E valuable information whichmay be derived either directly or indirectly from sublimation data, it is rather surprising that there is so little quantitative information available in the literature on the sublimation process. Apparently, no compilation of such data has been attempted. This summary of most of the available data, although not exhaustive, is the first serious attempt a t a tabulation for organic compounds.The variation of sublimation pressure with temperature may be represented to a first approximation by where p is the pressure of the saturated vapor in millimeters of mercury a t the absolute temperature T(T = to C. + 273.18). The constants A and B are related to the heat of sublimation and the entropy of sublimination (assuming these to be constant) in the following way:is the gas constant, 1.986 cal. per gram mole. The values of A and B are quoted to an accuracy a t least sufficient to reproduce sublimation pressures over the quoted temperature ranges to within the accuracy of the original observations. The AH and A S values derived from A and B are less certain if only because of the limitations in the relations used. Table I contains all the compounds for which full details are available. In cases where the authors have given an equation but have not deduced values for the heat and entropy of sublimation such values have been calculated and appear in bold face. The constants A and B are validfor the temperature ranges quoted for each compound. I t is obviously difficult to assess the quality of many of the results quoted, but an assessment has been attempted and the data considered most acceptable are footnoted. In arriving a t these conclusions the following facts were taken into account: In recent years there has been a considerable advance in the quality of the equipment available for the measurement of sublimation pressures.The adverse effect of impurities on the accuracy of the measurements was not fully appreciated by a considerable number of authors.In cases where doubts exist as to the validity of the results published, the data has been ignored.Failure by certain authors to ensure complete saturation in the air-flow method would invalidate their results.The effusion method is less sensitive to impurities than methods involving the use of a gauge.The fact that comparatively few measurements which have been described survive a critical appraisal, results in the paucity of reliable data. Table I1 contains a list of compounds for which limited sublimation pressure data are available. In the references given no heats or entropy values have been calculated for these compounds. ACKNOWLEDGMENT

SynopsisUniaxial strain and uniaxial stress preloadings were performed on quartz phenolic i i i order to assess the effect of an impulsive preload on the subsequent uniaxial stress behavior of a composite material. In these tests observable damage was limited to the phenolic matrix. As a result, postpreload experiments on the specimen under uniaxial stress correlated the dependence of the fracture strength with the extent of thedamage to the phenolic matrix as well as the direction of the reload relative to the fiber layup.

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