In this study the mechanical properties of bronze COMPOSITES reinforced with basalt fibers were studied. Basalt fibers are sensitive to the strengthening of the bronze was used in powder metallurgy. Samples were sintered at 850oC in reducing atmosphere (H2-%25N2) for 30 minutes. The effects of basalt fibers volume fraction on the friction properties and tensile properties of the COMPOSITES were investigated. The best tensile and wear properties of basalt fibers is visible in the samples containing 9%. The fracture surfaces of the samples were examined by electron microscopy.

The present paper describes the study of nonlinear bending characteristics of smart Functionally Graded (FG) PLATES combined with piezoelectric COMPOSITES. Material properties for the base FG plate are considered to vary along the thickness direction following the power-law principle. In this analysis, commercially available active fiber composite (AFC) material is utilized as the piezoelectric composite. A finite element (FE) model is made for the FG plate combined with AFC material. Simulation models for the smart FG PLATES are also developed using ANSYS software taking into account the effect of temperature on the material properties. Nonlinear deformations for the smart FG plate for various values of power index and different boundary conditions are presented for thermo-mechanical loading conditions considering the properties to be temperature as well as position dependent. Efforts are made to examine the performance of AFC patches towards control of nonlinear deflections. Various configurations for the smart FG PLATES are considered and the best location for placing the AFC patches is identified based on the efficiency of AFC material for controlling nonlinear deformations of the FG PLATES.

In the slitting method, a small width slit is created incrementally through the thickness of the stressed specimen and the released strains in each increment are recorded by a strain gauge. Compliance coefficients relate the measured strains to the residual stresses. This paper investigates the important parameters influencing the calculation of compliance coefficients for isotropic PLATES and laminated COMPOSITES by finite element analysis. First, the process of slitting in isotropic materials is simulated using two and three-dimensional finite element models. The results show complete agreement between these two models. Calculation of average strain at the strain gauge location is necessary for the calculation of compliance coefficients. For this purpose, strain-based and displacement-based methods are used. In addition, the effect of slit width on compliance coefficients is checked. Then, released strains by strain gauges with different gauge-lengths are compared with each other. The results show that the strain gauges with smaller gauge-lengths can record higher values of released strain and consequently increase the precision of measurements. Lastly, compliance coefficients for two glass/epoxy and carbon/epoxy laminates are calculated using the proposed three-dimensional model.

In this article, the dispersion of propagation waves in an arbitrary direction in laminated composite PLATES is studied in the framework of elasticity. Three-dimensional field equations of elasticity are considered, and the characteristic equation is obtained on employing the continuity of displacements and stresses at the layers' interfaces. Obtained characteristic equation is further simplified by making use of the properties of the block matrices. Some important particular cases such as of free waves on reducing PLATES to single layer and the surface waves when thickness tends to infinity are also discussed. Numerical results are also obtained and represented graphically.

In the central hole drilling method, the calibration factors relate the released strains to the residual stresses. In order to calculate the residual stresses for isotropic materials, two calibration factors from released strains are enough. However, for composite materials nine calibration factors are needed. These factors are presented in a matrix format and determining them for orthotropic materials is a tedious task. In this article, a new method for calculating the calibration factors for measuring the residual stresses in different material systems is presented. The simulated hole drilling method can be used instead of experimental techniques. In this method the process of hole drilling, using a finite element method, is simulated. The drilling location is simulated by a finite element technique and after applying the initial load in the form of residual stresses, the elements in the hole area are deleted from the model. Then, the strain around the hole area under the strain gages are calculated. The two and three dimensional simulations of the hole drilling method for isotropic materials are presented. The calibration factors are calculated and compared with those available in the standards. The results show a difference about 0.3% between the two methods. The simulation of the hole drilling process for the orthotropic materials, by different Poisson’s ratio, different shear stiffness and different module of elasticity is performed. For orthotropic materials, using the method presented in this study, the calibration coefficient matrix is obtained. The results are compared with the available analytical results. The consistency of the results show the reliability of the modeling process presented in this research. Also for laminated composite materials the presented method is utilized and the calibration coefficient matrix is obtained. Different laminated COMPOSITES with various lay ups and materials are considered. Using the simulated hole drilling method and calculating the residual strains around the hole area and calculating the calibration coefficient matrix, the residual stresses due to curing process are calculated. In this study different laminated COMPOSITES are simulated and by finding the calibration coefficient matrix, the residual stresses are obtained. The results are compared with the available experimental data and a very good correlation is obtained. The main advantage of the presented method is the capability to simulate the residual stresses in orthotropic materials with any degree of orthotropy. This method is able to simulate the behavior of different strain gages with different sizes and hole diameters. Simulation of the residual stresses for components and parts with complicated geometry is an application of this method. For very small components where measurement by with experimental methods is not possible, the SCHD method can calculate the calibration factors and therefore the residual stresses can be obtained. The calculation of the residual stresses in complicated specimens is another capability of the method presented in this study. Also, if the gradient of the variation of the residual stresses is too high, the SCHD University College of Engineering, University of Tehran 5 method is a suitable method to measure the residual stresses. Moreover, this method can be used to measure the calibration factors for calculation of non-uniform stresses through the thickness of the thick components.

In this paper, a numerical method is developed in order to predict the crack growth in multi-layerd COMPOSITES. Reddy's layerwise theory is em employed to truly calculate the the interlaminar stresses and afterward the accuracy of results are satisfied by Abaqus finite element software. Then the capability of solving problems in the presence of delamination, as the most important cause of COMPOSITES failure, is added to the elaborated model. In fallows, the J-integral method, which the integral is independent of the path around a crack, is introduced and by using the this method, the initially layerwised model is improved. Also, failure in structure is controlled by strain energy release rate; This means that firstly the process of computing total stiffness matrix of structure using layerwise element is described and nodal displacements and stress-strain fields in elements are extracted. Subsequently the possibility of predicting the crack growth is achieved by calculating the 3D J-integral using the criterion of strain energy release rate at crack front. Finally, the developed numerical model is validated by comparing the its results with the results of available analytical models and it is perceived that the model, despite being unique, is more similar to some of the analytical solutions.

In this study, free vibration analysis of laminated composite skew PLATES with embedded shape memory alloys under thermal loads is presented. The PLATES are assumed to be made of NiTi/Graphite/ Epoxy with temperature- dependent properties. The thermo- mechanical behavior of shape memory alloy wires is predicted by employing one-dimensional Brinson’s model. The governing equations are derived based on first- order shear deformation theory and solved using generalized differential quadrature technique as an efficient and accurate numerical tool. Some examples are provided to show the accuracy and efficiency of the applied numerical method by comparing the present results with those available in the literature. A parametric study is carried out to demonstrate the influence of skew angle, pre- strain and volume fraction of shape memory alloys, temperature, and stacking sequence of layers on the natural frequencies of the structure. Results represent that shape memory alloys can change the vibrational characteristics of shape memory alloy hybrid composite skew PLATES by a considerable amount. The numerical results also reveal that the effect of shape memory alloy wires on natural frequencies of composite PLATES with simply supported boundaries is higher than those with clamped boundaries.

In this study, an analysis of fiber reinforced, symmetrically laminated composite PLATES containing circular holes has been carried out. First, the stress state of a layer in a laminated plate is studied. After obtaining the stress state for each layer due to the uniaxial loading of a plate, the stress concentrations around a circular hole are studied. A number of diagrams are drawn to show the stress concentrations around a hole for layers having different oriented fibers using different material pairs with different E1/E2 ratios (ratio of elasticity modulus of fiber direction to that of transverse direction). Graphs are given for various E1/E2 values for the circumferential stress values around the hole versus angular location of points for two different fiber orientation angles. Second, the failure of the laminated composite plate is studied. To determine the “first–ply failure” of a laminated plate, Tsai-Hill failure criterion is employed to find minimum bearing circumferential stresses and where they occur as a function of the fiber orientation angle.

This study aims at flutter characteristics of orthotropic PLATES subjected to supersonic flow. The plate is subjected to uniform in-plane forces (Nx, Ny) and its edges are assumed to be elastically restrained (with various degree) against rotation. This type of boundary conditions covered a wide range of B.C's from simply support to clamped supports. The analytical solution is obtained using classical plate theory. Frequency equations of these systems are very large and difficult to solve. A simple method of solving this type of equations has been used in order to investigate the flutter characteristics of 011hotropic PLATES. The effect of plate geometry, material propel1ies, in-plane load and boundary condition are presented and discussed.      

This paper offers a method for weight optimization of multilayer fiber composite PLATES under the action of lateral loadings. The objective is to design a fiber composite plate of minimum thickness which can sustain multiple static loadings applied normal to its surface without exhibiting failure of any kind in anyone of its layers. In this investigation, fiber orientation angles are treated as discrete variables, which can vary only by pre-assigned increments. The thicknesses of layers are treated as continuous variables. The optimization procedure is based on a two stage strategy; in the first of which only the angles of layers, and in the second, the layer thicknesses are treated as variables. The two distinct stages that are executed separately in every iteration, is capable of consecutively choosing new layers (as identified by their orientation angles) of minimum possible thicknesses to be added to the set of layers in the laminate, provided those orientation angles prove to be the most useful. Reduction of the total thickness is treated as the criterion of usefulness of a new layer to be added to the set already at hand. The priorities exercised in the choice of new layers for inclusion in the set, allow an optimal state of stacking order to be achieved. At the same time, minimum total thickness criterion for acceptance of a new layer would exclude all unnecessary layers from the set. The end result would be a laminate of minimum total thickness whose layers appear in their proper position in the stack and with proper angle orientations. The maximum number of layers required in a set is arrived at by the rejection of all possible candidate angles, signaling the end of the optimization process. Thus the least total thickness, corresponding to the order in which layers of different angle orientation should be stacked, as the end result is achieved with no limitations imposed on the variation of orientation angles. Several examples are shown to demonstrate the operation of the algorithm.