Determination of physical properties and thermal conductivity of graphite foam with image analysis

Since pore network structures of porous materials have irregular shapes and may vary in size, the accurate characterization and virtual 3D reconstruction of these materials are of great importance for a deeper understanding of the structure and subsequent calculations. In this study, the scanning electron microscope (SEM) and X-ray microcomputed tomography (µCT) images of a graphite foam sample are used for image analysis method (IAM) and virtual 3D reconstruction as non-destructive scientific tools with high accuracy. The morphological characterization and determination of effective pore diameter, porosity, specific surface area (SSA), and effective thermal conductivity (ETC) of POCO graphite foam are investigated. By examining the results obtained from the method of image analysis, it is found that there is a good agreement among the IAM results

Electro-magneto-thermo-mechanical Behaviors of a Radially Polarized FGPM Thick Hollow Sphere

ABSTRACT In this study an analytical method is developed to obtain the response of electro-magneto-thermoelastic stress and perturbation of a magnetic field vector for a thick-walled spherical functionally graded piezoelectric material (FGPM). The hollow sphere, which is placed in a uniform magnetic field, is subjected to a temperature gradient, inner and outer pressures and a constant electric potential difference between its inner and outer surfaces. The thermal, piezoelectric and mechanical properties except the Poisson's ratio are assumed to vary with the power law functions through the thickness of the hollow sphere. By solving the heat transfer equation, in the first step, a symmetric distribution of temperature is obtained. Using the infinitesimal electro-magnetothermo-elasticity theory, then, the Navier's equation is solved and exact solutions for stresses, electric displacement, electric potential and perturbation of magnetic field vector in the FGPM hollow sphere are obtained. Moreover, the effects of magnetic field vector, electric potential and material in-homogeneity on the stresses and displacements distributions are investigated. The presented results indicate that the material in-homogeneity has a significant influence on the electro-magneto-thermo-mechanical behaviors of the FGPM hollow sphere and should therefore be considered in its optimum design

Flexural Behavior of Functionally Graded-Graphene Reinforced Composite Plates

A first order shear deformation theory based finite element numerical investigation on flexure behaviour of functionally graded thin, moderately thick and thick composite plates reinforced with graphene platelets (GPLs) is presented in this paper. The maximum deflection plays a major role in the design of composite structures. Therefore, maximum deflection and percentage maximum deflection ratio of reinforced to unreinforced composite plate are investigated for a range of GPL distribution patterns along plan and thickness directions of the composite plate. Modified Halpin-Tsai equation is used to determine the effective Young’s modulus for each layer in thickness direction for different distribution patterns. The rule of mixture is used to calculate effective mass density and Poisson’s ratio for each layer. Initially, the results from this study are verified by comparing with the reported results from the literature. Thereafter, validated methodology is used to conduct case study for a simply supported plate, focusing on the effect of thickness, GPL distribution patterns along plan and thickness directions, percentage weight fraction of GPL on the maximum deflection and percentage maximum deflection ratio of reinforced to unreinforced composite plate. It is found that by adding just 1% weight fraction of GPL, the maximum deflection can be reduced by almost 65% to 90% for all thicknesses and distribution patterns considered

Forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by CNTs based on MCST with temperature-variable material properties

ABSTRACT: In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes (CNTs) under magnetic field based on modify couple stress theory (MCST) with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton's principle and then computed these equations by using Navier's solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nano-composite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery. Keywords: Forced vibration analysis, Nano-composite rotating pressurized microbeam, Carbon nanotubes, Modify couple stress theory, Temperature-variable material propertie