Free vibration of simply supported circular cylindrical shell made of Functionally Graded Material (FGM) under internal pressure was investigated. The effective material properties are assumed to vary continuously along the thickness direction according to a volume fraction power law distribution. First order shear deformation theory based on Love's first approximation theory was utilized in the equilibrium equations. The effects of FGM parameters such as material configuration and power law exponent, internal pressure as well as geometrical parameters such as thickness to radius and length to radius ratios on the vibration behavior were investigated. The validation of the results was achieved by comparing with those available in the literature. The results show that the vibration characteristics of Functionally Graded (FG) shells are greatly influenced by FGM parameters. Also, internal pressure and geometrical parameters considerably influence the frequency behavior regarded to different values of FGM parameters. Manuscript profile

Abstract: Alumina (Al2O3) is one of the most practical ceramics used in making ceramic-metal armours. To improve the properties of alumina, some other materials are added to it. In this paper, SiC material as Nano powder is added to alumina, and four armour samples of this new ceramic with different volume fractions (V.F. ) including 0%, 5%, 10% and 15% of SiC particles are made. Then, the samples are warmed up by hot press and their fracture toughness, bending strength and density are measured. Then, it is found that the armour sample made of alumina with V.F. of 10% of SiC particles shows more desirable properties as compared to the other armour samples. So, the computer simulation and ballistic test are done using alumina with V.F. of 10% of SiC particles and the obtained results are compared with those of ballistic test of pure alumina. In the simulations, it is observed that the pure alumina with the thickness of 10 mm and aluminum substrate of thickness 4.8 mm is broken due to the normal impact of a projectile with 800 m/s speed, but the new armour made of the present new ceramic is able to withstand the same conditions and no fracture is observed after impact. The ballistic tests were also done using the present new ceramic-Aluminum armour samples with ceramic thicknesses of 6, 8 and 10 mm, respectively to determine the smallest thickness at which the fracture is occurred. It was found that the armour with the ceramic layer thickness of 6 mm got fractured, whereas the others were able to withstand the conditions of the ballistic test. Manuscript profile

The main target of this paper is to obtain an optimum wedge angle for best static and dynamic performance of a V-shaped clamp band separation mechanism. For this purpose, by using the finite element method, the proper 3D model for V-clamp band mechanism has been modelled and analysed in Abaqus/Explicit solver. In order to study the effect of wedge angle on bending and axial stiffness of V-clamp joint, many quasi-static analyses with different wedge angles were accomplished so the relation between wedge angle and axial stiffness of V-clamp joint under symmetric bending loading is extracted. In the next step, dynamic analyses were accomplished so the relation between wedge angle and separation time (duration between trigging moment and the time of disconnecting between flanges and wedged clamps) is extracted. For verification, this project results have been compared with the results of other researches and good agreement is observed. The results show that the optimal wedge angle for obtaining maximum stiffness together with minimum spring back disconnection time for the V-clamp band mechanism is 20˚. Manuscript profile

In this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and clamp-clamp boundary conditions and the results are compared with each other. To solve the problem, the equilibrium Equations of motions are written according to the classical shells theory and after simplification, the structural stiffness and mass matrices and the frequency Equation are derived using Galerkin method. The results obtained in this paper, are compared with the results available in the literatures, and the results of experimental and finite element methods and good agreement is observed. Manuscript profile

Nowadays grid structures are considered as one of the most useful composites because of their various applications. Since grid structures are vulnerable to impact loads, they should be investigated under such loadings. The present paper studies the low-velocity impact loading of sandwich panels with grid-stiffened cores using both experimental and numerical simulations. In addition to the impact behaviour and the resultant damage of the sandwich panels, the behaviour of these structures under three-point bending was studied before and after the impact loading. The results were provided for impact and bending loadings separately. Then the effect of impact loadings on bending strength was investigated and it was found that the impact loading decreases the bending strength. A consistency between numerical and experimental results was also observed, which confirms the applicability of the Finite Element Method (FEM) in simulating the behaviour of such structures under impact and bending loads, while saving lots of time, efforts and costs. Manuscript profile

The present study investigates the deformation of FGM plates under blast load. Hamilton's principle is used to obtain the dynamic Equations. The two constituent phases, ceramic and metal, vary across the wall thickness according to a prescribed power law. Boundary conditions are assumed to be Simply Supported (SS). The type of explosive loading considered is a free in-air spherical air burst and creates a spherical shock wave that travels radially outward in all directions. For the pressure time of the explosion loading, Friedlander’s exponential relation has been used. In order to determine the response analytically, the stress potential field function is considered. Using the Galerkin method, the final Equations are obtained as nonlinear and nonhomogeneous second-order differential Equations. The effect of temperature including thermal stress resultants and different parameters on the dynamic response have been investigated. Results have been compared with references and validated. Results showed that the amplitude of the center point deflection of the FGM plate is less than the pure metal plates when exposed to blast load, by increasing the volumetric index percentage of FGM, center point deflection is increased and in the FGM plates, deformation of symmetrical plates is smaller than the asymmetric plates. Also by applying the damping coefficient of the FGM plates, the amplitude of center point deflection is reduced, and by increasing the aspect ratio of the FGM plate, its center point deflection against explosion waves is reduced and by considering the effects of thermal resultant forces and moments, center point deflection is increased. Manuscript profile

The current study presents a mathematical modeling for sandwich panels with foam filled orthogonally rib-stiffened core using Heaviside distribution functions. The governing equations of the static problem have been derived based on classical lamination theory. The present model contains three displacement variables considering all of the stiffness coefficients. A closed form solution using Galerkin’s method is presented for simply supported sandwich panels with foam filled orthogonally rib-stiffened core subjected to uniform lateral static pressure. Compared to previous researches, the present work is comprehensive enough to be used for symmetric, unsymmetric, laminated or filament wound panels with orthogrid stiffeners. The accuracy of the solution is checked both through comparisons with previous works, and the results of simulation with ABAQUS software. Manuscript profile