Hamdy A Ashour

Materials developed for space application to sustain both of Mechanical loads and space environmental threats. The Electron Beam (EB) was selected to represent one of the most hazardous space environment parameters subjected to the Spacecraft (SC) components; the charged particle flux which predicted according to the space mission and its orbit parameters. The candidate materials for this study based on the carbon fiber/epoxy which was enhanced by adding Reduced Graphene Oxide (RGO) and investigate its resistance to EB. RGO addition was varies in three different compounds with different preparation methods; (RGO-24N, RGO-33C and RGO-G270). The RGO additives were dispersed in the epoxy matrix. Each sample was subjected to Integrated Current Transformer (ICT) electron beam at a constant dose of 100 kGy. The mechanical properties of Nano composites were tested by a Universal Testing System (UTS) and were correlated to the variation of their constituent molecular structure obtained by Fourier Transform Infrared (FTIR) spectroscopy, Dynamic Mechanical Analysis (DMA) and Electric Resistivity (ER). The results revealed an enhancement in the mechanical properties of epoxy mthe atrix after the addition of RGO except for (RGO-33C) and preservation of the Mechanical properties even after irradiation.

Environmental space threats are becoming more critical as they affect the optical, thermal, and electrical properties of the reinforced fiber polymeric-based materials in spacecraft. Three different Nano-particles Alumina (Al2,O3), Multiwall Carbon Nanotubes (MWCNT), and Reduced Graphene Oxide (RGO) were added to the epoxy matrix and then reinforced by bidirectional carbon fiber plain to form carbon fiber/epoxy by hand lay-up using autoclave curing technique to make three different reinforced materials. In this paper, the electrical, optical, and thermal properties of the carbon fiber/Epoxy Nanocomposite were studied. Fourier transform infrared (FTIR) was performed to evaluate the structural changes in the newly synthesized materials. The optical, thermal, and electrical properties were tested by UV-visible Spectroscopy, Photo-acoustic spectroscopy (PA), and Keithley 2635A respectively. The results showed an enhancement in the electrical, optical, and thermal properties of the epoxy...

An open field experiment was carried out during 2015 and 2016 seasons at the experimental nursery of the Ornamental Horticulture Department, Faculty of Agriculture, Cairo University, Egypt. The purpose of present research was to investigate the effect of foliar application of nano silicon with different concentrations and gypsum soil application on growth, flowering and chemical constituents of Jatropha integerrima plants irrigated with different levels of saline water. The concentrations of saline water were (1000, 2000 and 4000 ppm), in addition to tap water (270 ppm) as a control, simultaneously plants were received monthly foliar application of nano silicon 1 and 2 mM or soil application of gypsum at 20 g/plant, either applied individually or in combination.The results showed that, elevating salt concentration in irrigation water decreased vegetative growth characteristics, flowering traits, leaves anatomy and chemical constituents. In contrast, increasing salinity of irrigation...

This paper proposes a general compressive strength criterion for anisotropic rock materials under multiaxial states of stress. The proposed criterion is a generalization of the Von Mises' criterion for yielding of ductile metals, which has also been used previously as a strength criterion for brittle fracture in the spirit of both being limits of linear elastic behavior. The presently proposed criterion takes into consideration the effects of the confining pressure, the various stress components, and the material anisotropy on rock material failure in a multiaxial stress state. To verify the applicability of the proposed criterion, it has been used to construct the failure envelopes for several types of rock materials. Consequently, the constructed failure envelopes and the corresponding experimental results have been compared. In all cases, a close agreement with the experimental results has been achieved. This result demonstrates the versatility and applicability of the propos...

This work presents an assessment of the potential and economical feasibility of adopting wind energy as a renewable source of energy in Qatar. An analysis is presented for the long term measured wind speed (1976-1989) at Doha International Airport. The average annual wind speed was found to be about 4.4 m/s, which indicates the suitability of utilizing only small wind turbine generators, efficiently. Such small generators can be implemented for water pumping and to produce sufficient electricity to meet vital, limited needs of remote locations, such as isolated farms, which do not have access to the national electricity grid. An economical assessment is presented which takes into consideration the interest recovery factor, the life time of the wind energy conversion system (WECS), the investment rate and operation and maintenance costs. The results indicate that the cost of electricity generation from the wind in Qatar compares favorably to that from fossil fuel resources.

This work presents an analysis for the creep buckling problem of geometrically imperfect rectangular flat plates under biaxial compression with simple support boundary conditions. The analysis is based on a non-dimensional form of Donnell-type equations for a slightly imperfect flat plate. The elastic constitutive equations for a thin plate are employed. The basic elastic equilibrium equations in the middle surface displacement components are derived through the employment of the principle of virtual displacements. For creep deformations, Odqvist's constitutive equations for steady creep are employed. Based on the present analysis, a computer program has been developed for the creep buckling of flat plates. The plate ends are assumed to be simply supported. The applied loading is assumed to be biaxial compression. Numerical results are presented for imperfect isotropic plates under both unaxial and biaxial compression. For unaxially compressed plates, the present results are gen...

This work presents an assessment of the potential and economical feasibility of adopting off-shore/on-shore wind energy as a renewable source of energy in Qatar. An analysis is presented for the long term measured on-shore wind speed (1976–2000) at Doha International ...