A finite element model based on the layer wise THEORY of Reddy is developed for the analysis of delamination in the [90.0] S cross-ply laminated beams. The Heaviside step function was adopted in the formulation to express the discontinuous interlaminar displacement fields of delaminated layers. Also, to accommodate the moderately large rotations of the beam, the von Karman type nonlinear strain field is used in the formulation. The finite element model is verified by comparing the present solutions with those available in the literature. It is shown that the present finite element model is able to capture accurate local stress fields and the strain energy release rates. Then the model is used to study delaminated cross-ply laminates under bending loads. The influence of boundary conditions and number of layers on the strain energy release rates is studied. Also, the growth of delamination is investigated for a pure bending case, and the mode of delamination growth is identified. The influence of geometric nonlinearity on the delamination growth is also investigated as the delamination advances. It is found that geometric nonlinearity does not significantly alter the delamination kinematics and strain energy release rates.

In this study, an analytical solution is presented to calculate inter laminar stresses in long symmetric cross-ply composite laminates subjected to uniform axial strain and thermal loading. At first, the most general form of layer wise-based displacement field is extracted by a successive integration of elastic strain–displacement relations and imposing the physical restrictions based on deformation patterns of these laminates. The equilibrium equations are then derived by using the principle of minimum total potential energy and solved analytically in order to obtain three-dimensional stress field in the laminated plate. Finally, various numerical examples are investigated in order to validate the efficiency and accuracy of the layer wise THEORY in predicting the interlaminar stresses. For the assessment of the accuracy of the proposed method, the interlaminar stresses are also calculated within the framework of a 3D finite element analysis using the Abaqus software. The corresponding numerical results are in good agreement with those obtained through the layer wise THEORY. All results indicate that the presented approaches have a good prediction capability of interlaminar stresses in interior regions of the laminate and theirs high stress concentration near its free edges that can cause delamination failure.

In this study, the buckling and postbuckling behavior of composite laminates with piezoelectric layers subjected to compressive in-plane loading have been investigated. The effects of coupled electro-mechanical field on the postbuckling and bifurcation point in cross-ply and general lay-up sequences have been studied using LAYERWISE THEORY (LWT). The LWT used in this study for analyzing the piezo-composite laminate is based on the assumptions of the first order shear deformation THEORY (FSDT). In order to obtain the equilibrium equations, the principle of minimum potential energy has been employed. The obtained nonlinear equilibrium equations have been solved using Newton-Raphson iterative algorithm. Furthermore, the three dimensional finite element analysis has been performed to examine the accuracy of the results obtained using the proposed method. The obtained analytical results are in good agreement with those achieved through the finite element analysis. Obtained results showed that, location of the piezoelectric layers have significant effect on the buckling and postbuckling behavior of the composite plates. Moreover, number of degrees of freedom which is used in proposed method are less than finite element method which, decreased the computational time cost.

In this study, the analytical solution of interlaminar stresses near the free edges of a general (symmetric and unsymmetric layups) cross-ply composite laminate subjected to pure bending loading is presented based on Reddy’s LAYERWISE THEORY (LWT) for the first time. First, the reduced form of displacement field is obtained for a general cross-ply composite laminate subjected to a bending moment by elasticity THEORY. Then, first-order shear deformation THEORY of plates and LWT is utilized to determine the global and local deformation parameters appearing in the displacement fields, respectively. One of the main advantages of the developed solution based on the LWT is exact prediction of interlaminar stresses at the boundary layer regions. To show the accuracy of this solution, three-dimensional elasticity bending problem of a laminated composite is solved for special set of boundary conditions as well. Finally, LWT results are presented for edge-effect problems of several symmetric and unsymmetric cross-ply laminates under the bending moment. The obtained results indicate high stress gradients of interlaminar stresses near the edges of laminates.

In this paper, transient heat transfer analysis in composite metal cylindrical vessel will be investigated using the LAYERWISE THEORY and differential quadrature method. For this purpose, five samples from the metallic cylindrical vessel and composite metal cylindrical vessel has been under transient heat transfer analysis. Thermal conditions of governing the issue has been extracted from a practical and experimental conditions. The aim of this research is study and investigate the behavior of heat transfer in the vessels mentioned. Therefore, the governing equations of heat transfer is achieved in a multilayered cylindrical vessel. Due to the different behavior of multilayer cylindrical in heat transfer, the analysis is to be done using the LAYERWISE THEORY in order to obtain more accuracy. Then, the governing equations of heat transfer are derived for this vessel and are solved by differential quadrature method. In differential quadrature method, to solve the governing relations, these equations must be in the form of the matrix equations. The MATLAB programming code to be used to solve this matrix equations. After extracting result, temperature changes and heat transfer behavior in multilayer cylindrical vessel versus time have been discussed. To validate the resulting solution of the LAYERWISE THEORY and differential quadrature method, modeling and numerical analysis of heat transfer in Abaqus finite element software done and the results of this software were compared with the solution of differential quadrature. Finally, the results of this study have been compared with exact solution of heat transfer equations in the several reference.

In the present paper, dynamic behavior of a multilayer composite plate with viscoelastic structural damping is investigated against a low-velocity impact by a spherical indenter. Hertz contact law is refined to include effect of the lower layers on the stiffness of the contact region and used in a non-linear form. Voltra hierarchical integral is employed for modeling the viscoelastic material and the LAYERWISE THEORY and non-linear strain-displacement relations are used to model the plate more accurately. To solve the governing integro-differential equations, a combination of the finite element method, trapezoidal integration method for the Volterra integrals, and the Newmark numerical time integration method is used. In the results section, effects of the various viscoelasticity parameters and the indenter velocity on the time histories of the contact force, indentation, and lateral deflection of the plate are investigated. Results show that due to the damping nature of the viscoelastic materials, the plate rigidity and contact force increase whereas the maximum lateral deflection and the indentation decrease. Furthermore, higher contact forces do not necessarily indicates higher indentations.

One of the factors that can be the link between our intentions and actions and their external consequences is human agency, which indicates the conscious design and intentional execution of actions by the individual in order to influence future events.Objective and Method: This research with a developmental approach of psychometric method and method 1, examines the psychometric indices of the Human Factor Characteristics Scale using the classical THEORY of test score measurement and the graduated question-answer THEORY. The purpose of this study, which included high school students in Tehran, was selected by cluster sampling of 500 people as a sample size and statistical analysis was performed on 481 data. To collect the data, the ion Human Agent Characteristics Scale (2011) was used and the research questions were evaluated using IRTPRO and SPSS software.Results:The assumption of local independence based on Pearson x2 index was established by applying Simjima's calibrated question-answer THEORY and the assumption of being one-dimensional based on the analysis of multidimensional question-answer THEORY. Diagnosis parameters with question-answer approach and classical approach Test score Both item 25 approach had the lowest and item 2 had the highest diagnosis parameter. The answer thresholds for all the questions were so far apart that no option was covered by the other option, and the options were independently selected by individuals at intervals of theta. The total scale was calculated with Cronbach's alpha of 0.945, intentionality of 0.894, foresight of 0.780, self-reactivity of 0.871 and rethinking of 0.762. Also, the role of each item in internal consistency was investigated by the loop method, which all questions had a favorable role in internal consistency of this scale. The value of the validity coefficient obtained from the question-answer THEORY was obtained by marginal method for intentionality 0.92, forethought 0.85, self-reaction 0.91, rethinking 0.83..

In the present paper, responses of a multilayer viscoelastic composite plate against a low-velocity impact by a rigid spherical indenter is investigated. In this regard, a novel energy formulation that is suitable for impact analysis and accounts for the potential energy due to indentation is proposed and employed, for the first time. First, Hertz contact law is refined to include effect of the lower layers on the stiffness of the contact region. Voltra hierarchical integral is employed for modeling the viscoelastic material and a LAYERWISE THEORY capable of considering the transverse flexibility of the layers is used to accurately model the plate behavior. To solve the governing integro-differential equations, the finite element method, trapezoidal integration method, and Newmark numerical time integration method are used. In the results section, effects of the various viscoelasticity parameters and the indenter velocity on the time histories of the contact force, indentation, and lateral deflection of the plate are investigated. Results show that due to the damping nature of the viscoelastic materials, the plate rigidity and contact force increase whereas the maximum lateral deflection and the indentation decrease. Furthermore, higher contact forces do not necessarily indicates higher indentations.