Thermal Expansion Measurment

FIGURE 34.15 Thermal expansion characteristics of several polycrystalline ceramics. 

FIGURE 34.14 Schematic of a double pushrod differential dilatometer. 

FIGURE 34.16 Typical data for thermal expansion of a commercial silicate glass. 

FIGURE 34.17 Stresses generated in a layered structure due to differences in a. 

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All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

Thermal Expansion Measurement. Thermal expansion measurements were made with a laser interferometer dilatometer (2Q) with a strain resolution of approximately 2x10 6. The temperature cycle for all tests went from room temperature to a maximum of 121°C (except where noted), down to -157°C and back to room temperature. Thermal strain data were taken at approximately 20°C increments with a 30-minute hold at each temperature to allow the specimen and interferometer to reach thermal... 

Tests of a graphite-reinforced polyimide composite (C6000/PMR15) did not show any effect of radiation exposure (1 MEV electrons 6x109 rad total dose) on the thermal expansion behavior (14). DMA curves for unirradiated and irradiated composites were essentially identical over the temperature range of the thermal expansion measurements. 

Crosslinked low-density polyethylene foams with a closedcell structure were investigated using differential scanning calorimetry, scanning electron microscopy, density, and thermal expansion measurements. At room temperature, the coefficient of thermal expansion decreased as the density increased. This was attributed to the influence of gas expansion within the cells. At a given material density, the expansion increased as the cell size became smaller. At higher temperatures, the relationship between thermal expansion and density was more complex, due to physical transitions in the matrix polymer. Materials with high density and thick cell walls were concluded to be the best for low expansion applications. 16 refs. 

Chemical Family a group of elements that share similar chemical properties and share the same column in the periodic table, for example, halogens, alkali earth Chirality condition that describes the handedness of a molecule or whether a molecule exists in forms that can be superimposed on each other Chlorofluorocarbons also called CFCs, compounds consisting of chorine, fluorine, and carbon that are responsible for stratospheric ozone destruction Coagulation precipitation or separation from a dispersed state Coefficient of Thermal Expansion measure of the rate at which a substance will expand when heated... 

Thermal Fit and Residual Stresses. Thermal expansion measurements arc typically carried out on dilaiumeiric equipment consisting of a fused quartz pusher rod inside a tube of the same material. 

D. Havlik, W. Schranz, M. Haluska, H. Kuzmany, and P. Rogl, Thermal expansion measurements of C60-C70 mized crystals, Sol. State Comm. 104, 775-779 (1997). 

G. Ruffino, Thermal Expansion Measurement by Interferometry , pp. 689-706 in Compendium of Thermophysical Property Measurement Methods, Volume 1, Survey of Measurement Techniques ( K. D. Maglic, A. Cezairliyan, and V. E. Peletsky, eds.), Plenum Press, NY, (1984). 

Dannis, M. L. Thermal expansion measurements and transition temperatures. II. An automatic recording systems. J. Appl. Polymer Sci. 4, 249—250 (1960). 

Havlik D., Schranz W., Haluska M., Kuzmany N., Rogl P. Thermal expansion measurements of C6o-C70 mized crystals // Sol. State Comm. 1997. Vol. 104. P. 

Figure 3 - The linear thermal expansion measured for two blends of PIP and...

Certain features of the study were emphasized such as the fact that although the PuOi.ei phase was assumed b.c.c., the powder patterns were not good enough to show the superstructure lines. Also the eutectoid in the proposed diagram of Chikalla et al. (22) was not observed in the x-ray studies. No satisfactory explanation of electrical resistivity and thermal expansion measurements which led to this earlier construction has emerged. Gardner et al. (26) also looked for but did not see any indication of ordered intermediate phases at low temperatures such as were described above for the rare earth oxides nor did they observe a failure of the miscibility gap to close as would have occurred if the end members, PuOi.oi and PuOi.gg, had different symmetries. They could... 

Snow, A.W. Armistead, J. A simple dilatometer for thermoset cure shrinkage and thermal expansion measurements. J. Appl. Polym. Sci. 1994, 52, 401. 

Figure 2 Coefficient of linear thermal expansion (measured at 20 - 750°C)...

In this technique, commonly known as TMA, a vertical probe (flat, 0.140" diameter) is placed on the sample and thermal expansion measured as the sample is heated or cooled. The vertical probe is balanced in oil suspension and a certain weight is added to the probe to arrive at a net zero weight on the sample. Additional weight may be placed on the probe to improve the signal/noise ratio, but this affects the results as does spring loading in the horizontal dilatometer. Strain gauge techniques were also examined by us and were found to be less useful.(4)... 

Incidentally, the thermal expansivity measured at constant temperature and pressure, viz. Oj and a, and the thermal pressure coefficients measured at constant temperature and volume, viz. and P, remain the same in arrested as well as in internal equilibrium, i.e. a.j. = ttp = a and p.j, = p = p. In non-equilibrium, i.e. in the states between the two extremes of arrested and internal equilibrium, one finds in general that ol and p.. p. ... 

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