THE DEPENDENCE OF THE COMPRESSION MODULUS OF ICE-SIX AND THE COEFFICIENT OF VOLUME EXPANSION ON PRESSURE AND TEMPERATURE

This pioneering study investigated the partial derivatives of the dependence of the compression modulus of ice-six on pressure and temperature, and the coefficient of volume expansion on the temperature at high pressure and low temperature. Ice six is documented on the phase diagram between the pressures 600 and 2000 MPa and between the temperatures 110 and 330 K. The pressure and temperature dependence of the all-round compression module was practically implemented in a multilayer cylinder-piston vessel. The change in the relative volume of the sample was measured using a transducer which converts linear translational motion into electrical pulses. The pressure of the sample was measured by measuring the electrical resistance of tin and gallium conductors and phase transition points of polymorphic ice modifications. The temperature of this ice-six modification was determined by a graduated copperconstantan thermocouple. Moreover, in this paper, the Debye characteristic temperatures of ice-six and the Gruneisen constant are estimated.

The Thermal Conductivities of Periodic Fibrous Composites as Defined by a Mathematical Model

In this paper, a geometric body-centered model to simulate the periodic structure of unidirectional fibrous composites is presented. To this end, three prescribed configurations are introduced to predict in a deterministic manner the arrangement of internal and neighboring fibers inside the matrix. Thus, three different representative volume elements (RVEs) are established. Furthermore, the concept of the interphase has been taken into account, stating that each individual fiber is encircled by a thin layer of variable thermomechanical properties. Next, these three unit cells are transformed in a unified manner to a coaxial multilayer cylinder model. This advanced model includes the influence of fiber contiguity in parallel with the interphase concept on the thermomechanical properties of the overall material. Then, by the use of this model, the authors propose explicit expressions to evaluate the longitudinal and transverse thermal conductivity of this type of composite. The theoretical predictions were compared with experimental results, as well as with theoretical values yielded by some reliable formulae derived from other workers, and a reasonable agreement was found.