Fracture Analysis of a Special Cracked Lap Shear (CLS) Specimen with Utilization of Virtual Crack Closure Technique (VCCT) by Finite Element Methods

Some of the most important characteristics due to a fracture investigation of a special specimen are taken into account. Debonding considerations for a composite/steel cracked lap shear (CLS) specimen by utilization of finite element methods (FEM) as well as a virtual crack closure technique (VCCT) approach have been investigated. Strain energy release rate, delamination load case and direct cycle fatigue analysis have taken into consideration in this study, and the corresponding simulations have been done by ABAQUS/Standard. Linear elastic fracture criteria are used for validation of numerical results from the simulation. For comparison of three different categories of analysis, some special characteristics such as effective energy release rate ratio, bond state, time at bond failure and opening behind crack tip at bond failure have been illustrated. In this work, a detailed analysis of a special CLS specimen debonding by using VCCT and FEM is presented and varied results for validation of this kind of combination are obtained and have been discussed.Scopu

Thermo-mechanical vibration of rotating axially functionally graded nonlocal Timoshenko beam

The free vibration analysis of rotating axially functionally graded nanobeams under an in-plane nonlinear thermal loading is provided for the first time in this paper. The formulations are based on Timoshenko beam theory through Hamilton's principle. The small-scale effect has been considered using the nonlocal Eringen's elasticity theory. Then, the governing equations are solved by generalized differential quadrature method. It is supposed that the thermal distribution is considered as nonlinear, material properties are temperature dependent, and the power-law form is the basis of the variation of the material properties through the axial of beam. Free vibration frequencies obtained are cantilever type of boundary conditions. Presented numerical results are validated by comparing the obtained results with the published results in the literature. The influences of the nonlocal small-scale parameter, angular velocity, hub radius, FG index and also thermal effects on the frequencies of the FG nanobeams are investigated in detail.Scopu

Post-buckling of higher-order stiffened metal foam curved shells with porosity distributions and geometrical imperfection

Based on third-order shear deformation shell theory, the present paper investigates post-buckling properties of eccentrically stiffened metal foam curved shells/panels having initial geometric imperfectness. Metal foam is considered as porous material with uniform and non-uniform models. The single-curve porous shell is subjected to in-plane compressive loads leading to post-critical stability in nonlinear regime. Via an analytical trend and employing Airy stress function, the nonlinear governing equations have been solved for calculating the post-buckling loads of stiffened geometrically imperfect metal foam curved shell. New findings display the emphasis of porosity distributions, geometrical imperfectness, foundation factors, stiffeners and geometrical parameters on post-buckling properties of porous curved shells/panels.Scopu

Post-buckling analysis of geometrically imperfect tapered curved micro-panels made of graphene oxide powder reinforced composite

The present research investigates post-buckling behavior of geometrically imperfect tapered curved micro-panels made of graphene oxide powder (GOP) reinforced composite. Micro-scale effects on the panel structure have been included based on strain gradient elasticity. Micro-panel is considered to be tapered based on thickness variation along longitudinal direction. Weight fractions of uniformly and linearly distributed GOPs are included in material properties based on Halpin-Tsai homogenization scheme considering. Post-buckling curves have been determined based on both perfect and imperfect micro-panel assumptions. It is found that post-buckling curves are varying with the changes of GOPs weight fraction, geometric imperfection, GOP distribution type, variable thickness parameters, panel curvature radius and strain gradient.Scopu

Analysis of nonlinear vibrations of CNT- /fiberglass-reinforced multi-scale truncated conical shell segments

The truncated conical shell segments made from multi-scale epoxy/carbon nanotube/fiberglass material are studied in this research in the view of evaluating nonlinear free vibration behavior. Incorporating random dispersion of carbon nanotubes (CNTs) and parallel alignment of glass fibers, a three-dimensional (3D) Mori-Tanaka micro-mechanic method has been utilized for defining the hybrid material properties. For defining the configuration of truncated conical shell segments, a semi-vertex angle and also an open angle are used in the thin shell formulation. With the usage of Jacobi elliptic functions, exact values of nonlinear vibration frequencies have been derived which are more accurate compared to familiar approximate solutions. A specific attention is drawn to the impacts of fiber volume, fiber directions, semi-vertex angle, CNT weight fraction, and CNT aspect ratio on nonlinear free vibrations of multi-scale truncated conical shell segments. Communicated by Jie Yang.The first and second authors would like to thank Fidar Project Qaem (FPQ) for providing the fruitful and useful help.Scopu

Nonlinear vibrations of variable thickness curved panels made of multi-scale epoxy/fiberglass/CNT material using Jacobi elliptic functions

This article deals with nonlinear vibration study of variable thickness cylindrical panels made of multi-scale composite materials containing epoxy matrix, glass fibers, and carbon nanotubes (CNTs). The elastic properties of multi-scale material have been defined in the context of 3D Mori-Tanaka scheme considering unidirectional aligned macro-fibers and randomly oriented CNTs. It is considered that the panel thickness is varying in axial direction and may have linear and parabolic changes. The governing equations of variable thickness curved panel have been stablished using thin shell theory containing geometric nonlinearity. Then, Jacobi elliptic functions are proposed for solving the governing equations since they leads to exact frequency-amplitude curves of the curved panels. It is reported that frequency-amplitude curves are varying with the changes of CNT weight fraction, fiber orientation, fiber volume, variable thickness parameters, panel curvature radius, and length-to-radius ratio of CNTs.The first and second authors would like to thank FPQ (Fidar project Qaem) for providing the fruitful and useful help.Scopu

Investigating nonlinear vibrations of multi-scale truncated conical shell segments with carbon nanotube/fiberglass reinforcement using a higher order conical shell theory

This research deals with the nonlinear vibration analysis of functionally graded carbon nanotubes and fiber-reinforced composite truncated conical shell segments based upon third-order shear deformation theory. A detailed procedure for obtaining material properties of the multi-scale carbon nanotube/fiber-reinforced composite based on the three-dimensional Mori-Tanaka scheme has been provided. The truncated conical shell segments have been reinforced by distributed carbon nanotubes in the thickness direction according to uniform, linear, and nonlinear functions. The nonlinear equations have been solved via both Galerkin's technique and Jacobi elliptic function method. Based on the numerical results, the effects of diverse carbon nanotube distribution, fiber volume, fiber orientation, and semi-vertex and open angles of the segment on vibrational frequencies of the truncated conical shell have been studied.Scopu

Geometrically nonlinear vibration analysis of eccentrically stiffened porous functionally graded annular spherical shell segments

This article investigates nonlinear free vibrations of porous functionally graded (FG) annular spherical shell segments surrounded by elastic medium and reinforced by circumferential stiffeners. Porous FG material contains distributed even and un-even porosities and is modeled based on refined power-law function. The governing equations of stiffened porous annular spherical shell segments have been derived according to thin shell theory with the geometrical nonlinear in von Karman-Donnell sense and the smeared stiffeners method. An analytical trend has been provided for solving the nonlinear governing equations. Obtained results demonstrate the significance of porosity distribution, geometric nonlinearity, foundation factors, stiffeners and curvature radius on vibration characteristics of porous FG annular spherical shell segments.The first and second authors would like to thank FPQ (Fidar project Qaem) for providing the fruitful and useful help.Scopu

Assessment of transient vibrations of graphene oxide reinforced plates under pulse loads using finite strip method

Based on a refined shear deformation finite strip, transient vibrations of graphene oxide powder (GOP) reinforced plates due to external pulse loads have been investigated. The plate has uniformly and linearly distributed GOPs inside material structure. Applied pulse loads have been selected as sinusoidal, linear and blast types. Such pulse loads result in transient vibrations of the GOP-reinforced plates which are not explored before. Finite strip method (FSM) has been performed for solving the equations of motion and then inverse Laplace transform technique has been employed to derive transient responses due to pulse loading. It is reported in this study that the transient responses of GOP-reinforced plates are dependent on GOP dispersions, GOP volume fraction, type of pulse loading, loading time and load locations.Scopu

Investigating nonlinear forced vibration behavior of multi-phase nanocomposite annular sector plates using Jacobi elliptic functions

A multi-scale epoxy/CNT/fiberglass annular sector plate is studied in this paper in the view of determining nonlinear forced vibration characteristics. A 3D Mori-Tanaka model is employed for evaluating multi-scale material properties. Thus, all of glass fibers are assumed to have uni-direction alignment and CNTs have random diffusion. The geometry of annular sector plate can be described based on the open angle and the value of inner/outer radius. In order to solve governing equations and derive exact forced vibration curves for the multi-scale annular sector, Jacobi elliptic functions are used. Obtained results demonstrate the significance of CNT distribution, geometric nonlinearity, applied force, fiberglass volume, open angle and fiber directions on forced vibration characteristics of multi-scale annular sector plates.Scopu