Free vibration analysis of open-cell FG porous beams: analytical, numerical and ANN approaches

Emrah Madenci,Yasin Onuralp Özkılıç 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.2

This paper constitutes an attempt to explore the influence of porosity on free vibration analysis of functionally graded (FG) beams with different boundary conditions using different efficient analytical and numerical approaches. The material properties of open-cell FG porous beams are estimated using a modified power-law with two different types of porosity distributions through the thickness direction of the FG beam namely even and non-even distributions. Hamilton’s principle is used to derive the equations of motion of the FG porous beam with high-order shear deformation theory. The state-space approach is utilized to solve the problem in the analytical solution section. In addition to the theoretical solution, a simulation based on a displacement type of finite element method (FEM) was utilized to verify the analytical solution. For this purpose, three-dimensional shell beams were modeled using ABAQUS for the solution of the vibration problem of the FG porous beam. Furthermore, the Artificial Neural Networks (ANNs) technique is used to predict the effects of porosity distributions, porosity coefficient, slenderness ratio and boundary conditions on natural frequency variations of porous FG beam. The ANNs technique allows for an investigation of the effects of various parameters, including beam characteristics, material properties, geometric details and porosity distributions.

Experimental tensile test and micro-mechanic investigation on carbon nanotube reinforced carbon fiber composite beams

Emrah Madenci,Yasin Onuralp Ozkilic,Ahmad Hakamy,Abdelouahed Tounsi Techno-Press 2023 Advances in nano research Vol.14 No.5

Carbon nanotubes (CNTs) have received increased interest in reinforcing research for polymer matrix composites due to their exceptional mechanical characteristics. Its high surface area/volume ratio and aspect ratio enable polymer-based composites to make the most of its features. This study focuses on the experimental tensile testing and fabrication of carbon nanotube reinforced composite (CNTRC) beams, exploring various micromechanical models. By examining the performance of these models alongside experimental results, the research aims to better understand and optimize the mechanical properties of CNTRC materials. Tensile properties of neat epoxy and 0.3%; 0.4% and 0.5% by CNT reinforced laminated single layer (0°/90°) carbon fiber composite beams were investigated. The composite plates were produced in accordance with ASTM D7264 standard. The tensile test was performed in order to see the mechanical properties of the composite beams. The results showed that the optimum amount of CNT was 0.3% based on the tensile capacity. The capacity was significantly reduced when 0.4% CNT was utilized. Moreover, the experimental results are compared with Finite Element Models using ABAQUS. Hashin Failure Criteria was utilized to predict the tensile capacity. Good conformance was observed between experimental and numerical models. More importantly is that Young' Moduli of the specimens is compared with the prediction Halpin-Tsai and Mixture-Rule. Although Halpin-Tsai can accurately predict the Young's Moduli of the specimens, the accuracy of Mixture-Rule was significantly low.

Free vibration and static analyses of metal-ceramic FG beams via high-order variational MFEM

Emrah Madenci 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.5

There is not enough mixed finite element method (MFEM) model developed for static and dynamic analysis of functionally graded material (FGM) beams in the literature. The main purpose of this study is to develop a reliable and efficient computational modeling using an efficient functional in MFEM for free vibration and static analysis of FGM composite beams subject to high order shear deformation effects. The modeling of material properties was performed using mixture rule and Mori-Tanaka scheme which are more realistic determination techniques. This method based on the assumption that a two phase composite material consisting of matrix reinforced by spherical particles, randomly distributed in the beam. To explain the displacement components of the shear deformation effects, it was accepted that the shear deformation effects change sinusoidal. Partial differential field equations were obtained with the help of variational methods and then these equations were transformed into a novel functional for FGM beams with the help of Gâteaux differential derivative operator. Thanks to the Gâteaux differential method, the compatibility of the field equations was checked, and the field equations and boundary conditions were reflected to the function. A MFEM model was developed with a total of 10 degrees of freedom to apply the obtained functional. In the numerical applications section, free vibration and flexure problems solutions of FGM composite beams were compared with those predicted by other theories to show the effects of shear deformation, thickness changing and boundary conditions.

Buckling performance of pultruded glass fiber reinforced polymer profiles infilled with waste steel fiber reinforced concrete under axial compression

Emrah Madenci,Sabry Fayed,Walid Mansour,Yasin Onuralp Özkılıç 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.5

This study reports the results of a series of tests of pultruded glass fiber reinforced polymer (P-GFRP) box section composite profile columns, geometrically similar with/without concrete core, containing 0-1-2-3% steel fiber, with different lengths. The recycled steel wires were obtained from waste tyres. The effects of steel fiber ratio on the collapse and size effect of concrete filled P-GFRP columns under axial pressure were investigated experimentally and analytically. A total of 36 columns were tested under compression. The presence of pultruded profile and steel wire ratio were selected as the primary variable. The capacity of pultruded profiles with infilled concrete are averagely 9.3 times higher than the capacity of concrete without pultruded profile. The capacity of pultruded profiles with infilled concrete are averagely 34% higher than that of the pultruded profiles without infilled concrete. The effects of steel wire ratio are more pronounced in slender columns which exhibit buckling behavior. Moreover, the proposed analytical approach to calculate the capacity of P-GFRP columns successfully predicted the experimental findings in terms of both pure axial and buckling capacity.

Free vibration analysis of carbon nanotube RC nanobeams with variational approaches

Madenci, Emrah Techno-Press 2021 Advances in nano research Vol.11 No.2

There is not enough mixed finite element method (MFEM) model developed for dynamic analysis of carbon nanotube reinforced (CNTRC) composite beams in the literature. In the present study, free vibration analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) nanobeams is carried out in the framework of variational formulations. The rule of mixture is employed to estimate the effective material properties of single-walled CNT reinforced nanobeams. Four kinds of CNT distribution of un-axially aligned reinforcement material are investigated in the through-thickness direction of the nanobeams. There are the uniform distribution (UD) and functionally graded distributions FG-O, FG-X and FG-Ʌ of CNTs in the thickness direction of the nanobeams (z axis direction) are assumed here for the analysis. The Hamilton's principle is used to derive governing differential equations based on trigonometric shear deformation beam theory. The effective functional has been constituted for FG-CNTRC nanobeams through a scientific procedure based on the Gâteaux differential. A simple mixed finite element formulation is utilized for the formulation of free vibration problems of FG-CNTRC nanobeams with different boundary conditions. The results of the present method are compared with others from the literature where a good agreement has been found. An effective energy functional and the mixed finite element formulation for FG-CNTRC nanobeams are the original contributions of this study.

Optimization of flexure stiffness of FGM beams via artificial neural networks by mixed FEM

Emrah Madenci,Şaban Gülcü 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.5

Artificial neural networks (ANNs) are known as intelligent methods for modeling the behavior of physical phenomena because of it is a soft computing technique and takes data samples rather than entire data sets to arrive at solutions, which saves both time and money. ANN is successfully used in the civil engineering applications which are suitable examining the complicated relations between variables. Functionally graded materials (FGMs) are advanced composites that successfully used in various engineering design. The FGMs are nonhomogeneous materials and made of two different type of materials. In the present study, the bending analysis of functionally graded material (FGM) beams presents on theoretical based on combination of mixed-finite element method, Gâteaux differential and Timoshenko beam theory. The main idea in this study is to build a model using ANN with four parameters that are: Young’s modulus ratio (Et/Eb), a shear correction factor (ks), power-law exponent (n) and length to thickness ratio (L/h). The output data is the maximum displacement (w). In the experiments: 252 different data are used. The proposed ANN model is evaluated by the correlation of the coefficient (R), MAE and MSE statistical methods. The ANN model is very good and the maximum displacement can be predicted in ANN without attempting any experiments.

A refined functional and mixed formulation to static analyses of fgm beams

Emrah Madenci 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.4

In this study, an alternative solution procedure presented by using variational methods for analysis of shear deformable functionally graded material (FGM) beams with mixed formulation. By using the advantages of Gâteaux differential approaches, a refined complex general functional and boundary conditions which comprises seven independent variables such as displacement, rotation, bending moment and higher-order bending moment, shear force and higher-order shear force, is derived for general thick-thin FGM beams via shear deformation beam theories. The mixed-finite element method (FEM) is employed to obtain a beam element which have a 2-nodes and total fourteen degrees-of-freedoms. A computer program is written to execute the analyses for the present study. The numerical results of analyses obtained for different boundary conditions are presented and compared with results available in the literature.

Variational approximate for high order bending analysis of laminated composite plates

Emrah Madenci,Atilla Özütok 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.1

This study presents a 4 node, 11 DOF/node plate element based on higher order shear deformation theory for lamina composite plates. The theory accounts for parabolic distribution of the transverse shear strain through the thickness of the plate. Differential field equations of composite plates are obtained from energy methods using virtual work principle. Differential field equations of composite plates are obtained from energy methods using virtual work principle. These equations were transformed into the operator form and then transformed into functions with geometric and dynamic boundary conditions with the help of the Gâteaux differential method, after determining that they provide the potential condition. Boundary conditions were determined by performing variational operations. By using the mixed finite element method, plate element named HOPLT44 was developed. After coding in FORTRAN computer program, finite element matrices were transformed into system matrices and various analyzes were performed. The current results are verified with those results obtained in the previous work and the new results are presented in tables and graphs.

Analytical nonlocal elasticity solution and ANN approximate for free vibration response of layered carbon nanotube reinforced composite beams

Emrah Madenci,Saban Gulcu,Kada Draiche Techno-Press 2024 Advances in nano research Vol.16 No.3

This article investigates the free vibration behavior of carbon nanotube reinforced composite (CNTRC) beams embedded using variational analytical methods and artificial neural networks (ANN). The material properties of layered functionally graded CNTRC (FG-CNTRC) beams are estimated using nonlocal parameters modified power-law with different types of CNT distributions through the thickness direction of the beam. Adopting Eringen's nonlocal elasticity theory to capture the small size effects, the nonlocal governing equations are derived and solved using the analytical method. And also, the problem was analyzed using the ANN method. The architecture of the proposed ANN model is 3-9-1. In the experiments, we used 112 different data to predict the natural frequency using ANN. Based on the nonlocal differential constitutive relations of Eringen, the equations of motion as well as the boundary conditions of the beam are derived using Hamilton's principle. The classical beam theory is used to formulate a governing equation for predicting the free vibration of laminated CNTRC beams. According to the experimental results, the prediction ability of the ANN model is very good and the natural frequency can be predicted in ANN without attempting any experiments.

Improving Bond Performance of Near-Surface Mounted Steel Ribbed and Threated Rods in the Concrete

Sabry Fayed,Emrah Madenci,Yasin Onuralp Özkiliç,Mohamed H. Zakaria 한국콘크리트학회 2024 International Journal of Concrete Structures and M Vol.18 No.2

In this study, the experimental findings of twenty pull-out tests on the bond efficiency of threaded/ribbed steel rods used in near-surface mounting (NSM) are presented. On a groove (20 × 20 mm) that was slotted in one of the sides of a concrete block measuring 250 × 250 × 200 mm, a pull-out experiment was performed. The primary factors are the slot-filling materials (substrate concrete and epoxy paste), bonded length (equal to 5, 7, 10, and 15 times the rod diameter), surface pattern conditions (conventional ribbed reinforcing rebar and threaded bolt), use of nuts or rings welded at the free end of the bonded length, and use of straight or spiral wire welded along the length of the bonded length. The tested specimens' ultimate bond strength, slip, bond stress–slip response, failure patterns, stiffness, and ductility are recorded and assessed. The results showed that the ultimate bond strength and corresponding slip of ribbed rods cemented with epoxy were higher by 11.11% and 199%, respectively, than those of ribbed rods submerged in the substrate. Over the controls, all NSM epoxy-rods exhibited a greater ductility. As the bonded length increased, the ultimate bond strength of NSM rods fell by 12–32%. As the bonded length increased, the stiffness decreased. On the other hand, the ductility of NSM epoxy-rods increased as the bonded length increased. All applied schemes such as nuts, rings, longitudinal bars, and spiral bars significantly improved the ultimate bond strength (maximum = 25.93%) and corresponding slip (maximum = 166.67%) of NSM threaded rods as compared to the control ones.