Thermal conductivity and thermal expansion of graphite fiber/copper matrix composites
The high specific conductivity of graphite fiber/copper matrix (Gr/Cu) composites offers great potential for high heat flux structures operating at elevated temperatures. To determine the feasibility of applying Gr/Cu composites to high heat flux structures, composite plates were fabricated using unidirectional and cross-plied pitch-based P100 graphite fibers in a pure copper matrix. Thermal conductivity of the composites was measured from room temperature to 1073 K, and thermal expansion was measured from room temperature to 1050 K. The longitudinal thermal conductivity, parallel to the fiber direction, was comparable to pure copper. The transverse thermal conductivity, normal to the fiber direction, was less than that of pure copper and decreased with increasing fiber content. The longitudinal thermal expansion decreased with increasing fiber content. The transverse thermal expansion was greater than pure copper and nearly independent of fiber content.
Review of the Thermal Conductivity of Graphite-Reinforced Metal Matrix Composites
The characteristics of graphite-reinforced metal matrix composites (MMCs) are increasingly important in a wide range of technologies. While most of the published studies deal with the mechanical properties of these materials, there have been limited studies characterizing the thermal properties of some of these materials. The effective thermal conductivity is of particular importance for design and applications, and experimental data are summarized and compared with accepted models of composite properties. On the basis of this review, it is evident that the thermal properties of graphite e ber-reinforced MMCs have not been adequately investigated. Modeling techniques based on limited experimental data have identie ed some of the important parameters, but no single model adequately predicts either the longitudinal or the transverse conductivity of these materials. This study presents a review of the experimental and analytical investigations of the thermal conductivity of these materials and concludes with recommendations for emerging and continuing areas of investigation. Nomenclature a = e ber radius d = e ber diameter hc = e ber‐ matrix interface contact conductance k = thermal conductivity L = longitudinal s = vertical e ber separation T = transverse t = horizontal e ber separation V = e ber volume fraction v/o = e ber volume fraction f = angle of departure from longitudinal direction of the composite Subscripts c = composite e = effective f = e ber m = matrix r = radial u = circumferential ’ = perpendicular to e ber direction // = parallel to the e ber direction
Computer-Aided System of Virtual Testing of Gas Turbine Engines
The article describes the concept of a virtual lab that includes subsystem of gas turbine engine simulation, subsystem of experiment planning, subsystem of measurement errors simulation, subsystem of simulator identification and others. The basis for virtual lab development is the computer-aided system of thermogasdynamic research and analysis “ASTRA”. The features of gas turbine engine transient modes simulator are described. The principal difference between the simulators of transient and stationary modes of gas turbine engines is that the energy balance of the compressor and turbine becomes not applicable. The computer-aided system of virtual gas turbine engine testing was created using the developed transient modes simulator. This system solves the tasks of operational (throttling, speed, climatic, altitude) characteristics calculation, analysis of transient dynamics and selection of optimal control laws. Besides, the system of virtual gas turbine engine testing is a clear demonstration of gas turbine engine working process and the regularities of engine elements collaboration. The interface of the system of virtual gas turbine engine testing is described in the article and some screenshots of the interface elements are provided. The developed system of virtual gas turbine engine testing provides means for reducing the laboriousness of gas turbine engines testing. Besides, the implementation of this system in the learning process allows the diversification of lab works and therefore improve the quality of training.