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RISS 인기검색어
- 검색키워드
- 저자 : Ammar Melaibari (검색결과 4 건)
- 무료
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Static stability and of symmetric and sigmoid functionally graded beam under variable axial load
Ammar Melaibari,Ahmed B. Khoshaim,Salwa A. Mohamed,Mohamed A. Eltaher 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.5
This manuscript presents impacts of gradation of material functions and axial load functions on critical buckling loads and mode shapes of functionally graded (FG) thin and thick beams by using higher order shear deformation theory, for the first time. Volume fractions of metal and ceramic materials are assumed to be distributed through a beam thickness by both sigmoid law and symmetric power functions. Ceramic–metal–ceramic (CMC) and metal–ceramic–metal (MCM) symmetric distributions are proposed relative to mid-plane of the beam structure. The axial compressive load is depicted by constant, linear, and parabolic continuous functions through the axial direction. The equilibrium governing equations are derived by using Hamilton’s principles. Numerical differential quadrature method (DQM) is developed to discretize the spatial domain and covert the governing variable coefficients differential equations and boundary conditions to system of algebraic equations. Algebraic equations are formed as a generalized matrix eigenvalue problem, that will be solved to get eigenvalues (buckling loads) and eigenvectors (mode shapes). The proposed model is verified with respectable published work. Numerical results depict influences of gradation function, gradation parameter, axial load function, slenderness ratio and boundary conditions on critical buckling loads and mode-shapes of FG beam structure. It is found that gradation types have different effects on the critical buckling. The proposed model can be effective in analysis and design of structure beam element subject to distributed axial compressive load, such as, spacecraft, nuclear structure, and naval structure.
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Nonlocal strain gradient theory for buckling and bending of FG-GRNC laminated sandwich plates
Muhammad Basha,Ahmed Amine Daikh,Ammar Melaibari,Ahmed Wagih,Ramzi Othman,Khalid H. Almitani,Mostafa A. Hamed,Alaa Abdelrahman,Mohamed A Eltaher 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.5
The bending and buckling behaviours of FG-GRNC laminated sandwich plates are investigated by using novel fivevariables quasi 3D higher order shear deformation plate theory by considering the modified continuum nonlocal strain gradient theory. To calculate the effective Young’s modulus of the GRNC sandwich plate along the thickness direction, and Poisson’s ratio and mass density, the modified Halpin-Tsai model and the rule of the mixture are employed. Based on a new field of displacement, governing equilibrium equations of the GRNC sandwich plate are solved using a developed approach of Galerkin method. A detailed parametric analysis is carried out to highlight the influences of length scale and material scale parameters, GPLs distribution pattern, the weight fraction of GPLs, geometry and size of GPLs, the geometry of the sandwich plate and the total number of layers on the stresses, deformation and critical buckling loads. Some details are studied exclusively for the first time, such as stresses and the nonlocality effect.
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Analysis of the machinability of GFRE composites in drilling processes
Usama. A. Khashaba,Mohamed S. Abd-Elwahed,Khaled I. Ahmed,Ismail Najjar,Ammar Melaibari,Mohamed A Eltaher 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.4
Drilling processes in fiber-reinforced polymer composites are essential for the assembly and fabrication of composite structural parts. The economic impact of rejecting the drilled part is significant considering the associated loss when it reaches the assembly stage. Therefore, this article tends to illustrate the effect of cutting conditions (feed and speed), and laminate thickness on thrust force, torque, and delamination in drilling woven E-glass fiber reinforced epoxy (GFRE) composites. Four feeds (0.025, 0.05, 0.1, and 0.2 mm/r) and three speeds (400, 800, and 1600 RPM) are exploited to drill square specimens of 36.6x36.6 mm, by using CNC machine model “Deckel Maho DMG DMC 1035 V, ecoline”. The composite laminates with thicknesses of 2.6 mm, 5.3 mm, and 7.7 mm are constructed respectively from 8, 16, and 24 glass fiber layers with a fiber volume fraction of about 40%. The drilled specimen is scanned using a high-resolution flatbed color scanner, then, the image is analyzed using CorelDraw software to evaluate the delamination factor. Multi-variable regression analysis is performed to present the significant coefficients and contribution of each variable on the thrust force and delamination. Results illustrate that the drilling parameters and laminate thickness have significant effects on thrust force, torque, and delamination factor.
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Experimental and numerical FEM of woven GFRP composites during drilling
Mohamed S. Abd-Elwahed,Usama A. Khashaba,Khaled I. Ahmed,Mohamed A. Eltaher,Ismael Najjar,Ammar Melaibari,Azza M. Abdraboh 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.5
This paper investigates experimentally and numerically the influence of drilling process on the mechanical and thermomechanical behaviors of woven glass fiber reinforced polymer (GFRP) composite plate. Through the experimental analysis, a CNC machine with cemented carbide drill (point angles =118° and 6 mm diameter) was used to drill a woven GFRP laminated squared plate with a length of 36.6 mm and different thicknesses. A produced temperature during drilling “heat affected zone (HAZ)” was measured by two different procedures using thermal IR camera and thermocouples. A thrust force and cutting torque were measured by a Kistler 9272 dynamometer. The delamination factors were evaluated by the image processing technique. Finite element model (FEM) has been developed by using LS-Dyna to simulate the drilling processing and validate the thrust force and torque with those obtained by experimental technique. It is found that, the present finite element model has the capability to predict the force and torque efficiently at various drilling conditions. Numerical parametric analysis is presented to illustrate the influences of the speeding up, coefficient of friction, element type, and mass scaling effects on the calculated thrust force, torque and calculation’s cost. It is found that, the cutting time can be adjusted by drilling parameters (feed, speed, and specimen thickness) to control the induced temperature and thus, the force, torque and delamination factor in drilling GFRP composites. The delamination of woven GFRP is accompanied with edge chipping, spalling, and uncut fibers.
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