Mechanics of Advanced Composite Structures
Volume:7 Issue: 1, Winter-Spring 2020

Pursuant to the high usage of rotating the disk in aircraft gas turbine engine, turbo pumps in oil and gas industries, steam and gas turbines in power plants, marine gas turbine and other industrial rotary machines designing and getting under the mechanical and thermal loading casued this design and analysis to be as a special significance. These disks are subjected to mechanical and thermal loads. In this article, four methods, variable material properties (VMP), Galerkin, Runge-Kutta with two different rules compute the amount of displacement, stress, and strain of a rotary disk, which has been applied from a functionally graded material (FGM). The problem in dissimilar states of loading and temperature dependence and independence of the properties has been resolved. Disk properties with the specified function of radius change. Mechanical loading conditions result from the centrifugal disk and blades mounted on it and the effects of shaft pressure and thermal stress caused by temperature difference in the shaft. The results acquired through every four methods are closed together and can be applied to analyse the problems of this type. Combining all loads, the most radial stresses and environmental stresses respectively obtained in the center of the inner and outer radius and inner radius of the disk. Through applying the results can get most optimal design of the (FGM) disk.

This artcile is concerned with thermal buckling and thermal induced free vibration analyses of PCPs (perforated composite plates) with simply supported edges applying a mathematical model. The stiffness and density of PCP are defined locally using Heaviside distribution functions. The governing equations are derived based on CLPT. The present solution gives reasonable results in comparison with the few literatures. In order to inspect the structural behaviour of PCPs subjected to initial thermal loads, many parametric studies have been carried out. Results indicated that the presence of perforations has a significant effect on thermal buckling and thermal induced fundamental frequency.

The composite structural system (RCS) is a new type of moment frame, which is including a combination of concrete columns (RC) and steel beams (S). These structural systems have the advantages of both concrete and steel frames [1]. In previous research on composite structures, there are some studies regarding RCS composite conections, but there is no investigation about seismic resisting system for these systems in aspect of implementation and performance. In this paper, it is investigated about the seismic behavior of the RCS composite bracing frame. To achieve this objective, nonlinear analysis of RCS composite frames with and without bracing has been done using finite element method. The behavior factors of these frames have been calculated after analyzing frames. It can be seen based on the results of the analysis that braces increase the yielding strength, ultimate strength and stiffness of RCS composite frames. Also, the comparison of analytical and experimental results shows that the nonlinear behavior of RCS can be accurately predicted using finite element method.

Several deficient steel structural members require to be strengthened all over the world. In this article, horizontal defects were generated at three locations (top, middle, and bottom) on the middle element and the middle of the side element. Consequently, the effects of the location of such defects on axial behavior of Carbon Fiber Reinforced Polymer (CFRP) strengthened steel Square Hollow Section (SHS) tubular short columns were examined. To this end, a total of 13 steel columns were experimentally examined. The same specimens were simulated applying ABAQUS V.6.14. The samples were no defect (control), 6 non-strengthened columns with defects at different locations, and 6 strengthened specimens with defects. The results indicated that horizontal defects caused a significant decrease in load bearing capacity and initial performance. The damage located at the middle and the middle of the corner elements caused the most reductions on load bearing capacity by 16% and 17%, compared to the control, respectively. The defects on the side element led to greater destruction and bearing capacity decline compared to the middle defects. As a result of axial loading, the area of horizontal defects experienced local buckling, lateral rupture, and axial deformation boost. Carbon Fiber played a key role in ductility and strength increase around the defect by covering it. Applying four CFRP layers declined the stress concentration, delaying the local buckling as a result of high confining strength. The fiber increased bearing capacity by 64% and 37% for the middle and the corner elements, compared to the control.

In this article, in reference to the modified couple stress theory and Euler-Bernoulli beam theory, the free lateral vibration response of a micro-beam carrying a moveable attached mass is investigated. This is a decent model for biological and biomedical applications beneficial to the early-stage diagnosis of diseases and malfunctions of human body organs and enzymes. The micro-cantilever beam is composed of functionally graded materials (FGMs). The material properties are supposed to show variations through-thickness of the beam in consonance to the power of law. Rayleigh-Ritz method is applied in order to explore the natural frequencies of the first three vibration modes. In order to manifest the accuracy of the proposed method, the results are established and juxtaposed with technical literature. Influences of the material length-scale parameter that captures the size-dependency, ratio of the mass of the beam to the mass of the attached mass and power index of the graded material consequent to the vibrational behavior of the system are contemplated. This technical research denotes the value of the material gradation besides to the inertia of an attached mass in the dynamic behavior of the bio-micro-systems. As a result, the adoption of suitable power index, mass ratio and position of the attached mass lead to the superior design of bio-micro-systems persuading early-stage diagnostics.

In this article fluid-structure interaction of vibrating composite piezoelectric plates is investigated. Since the plate is assumed to be moderately thick, rotary inertia effects and transverse shear deformation effects are deliberated by applying exponential shear deformation theory. Fluid velocity potential is acquired using the Laplace equation, and fluid boundary conditions and wet dynamic modal functions of the plate are expanded in terms of finite Fourier series to satisfy compatibility along with the interface between plate and fluid. The electric potential is assumed to have a cosine distribution along the thickness of the plate in order to satisfy the Maxwell equation. After deriving the governing equations applying Hamilton’s principle, the natural frequencies of the fluid-structure system with simply supported boundary conditions are computed using the Galerkin method. The model is compared to the available results in the literature, and consequently the effects of different variables such as depth of fluid, the width of fluid, plate thickness, and aspect ratio on natural frequencies and mode shapes are displayed.

In the current research work synthesis, characterization, mechanical and wear behavior of 5 and 10 wt. % of nano TiO2 particulates reinforced Al7075 alloy composites are inspected. The Al7075 alloy and nano TiO2 particle composites were provided by melt stir system. After the preparation, the prepared composites were analyzed by SEM, EDS, and XRD for inquiring the microstructures and chemical elements. Furthermore, mechanical and wear behavior of as cast Al7075 alloy and Al7075 -5 and 10 wt. % of nano TiO2 composites were examined. Mechanical properties like hardness, UTS, yield quality, and ductility were assessed pursuant to ASTM measures. Pin on disc contraption was applied in order to lead the dry sliding wear tests. The analyses were led by differing loads and sliding speeds for a sliding distance of 3000 m. From the examination, it was discovered that the hardness, extreme strength and yield quality of composites were expanded because of nano TiO2 particles in the Al7075 amalgam grid. In nano TiO2 fortified composites the rate extension was diminished. Moreover, there was an expansion in the volumetric wear misfortune concerning the load, speed and sliding distance for all the readied materials. In order to inspect the fractography and dissimilar wear mechanisms for various test conditions of different compositions, tensile fractured surfaces and the worn surface morphology were analyzed by scanning electron microscope.

A complete investigation on the free vibration of bilayer graphene nanoribbons (BLGNRs) mod-eled as sandwich beams taking into account tensile-compressive and shear effects of van der Waals (vdWs) interactions between adjacent graphene nanoribbons (GNRs) as well as between GNRs and polymer matrix is performed in this research. In this modeling, nanoribbon layers play role of sandwich beam layers and are modeled based upon Euler-Bernoulli theory. To consider effects of vdWs interactions between adjacent GNRs as well as between GNRs and polymer matrix, their equivalent tensile-compressive and shear moduli are considered and utilized in derivation of governing equations instead of employing conventional Winkler and Pasternak effects for elastic medium. The governing equations of motion are derived by considering the assumptions and employing sandwich beam theory, and natural frequencies are obtained by implementing harmonic differential quadrature method (HDQM). A detailed study is performed to examine the influences of the tensile-compressive and shear effects of vdWs interactions between adjacent GNRs as well as between GNRs and polymer matrix on the free vibration of BLGNRs.

In this article, vibration characteristics and the parametric instability of functionally graded material (FGM) plates with cyclic loading in a hygrothermal field are discussed. The plate element is modeled in a finite element by applying the third-order shear deformation hypothesis. The mathematical formulation of the FGM plate is made with two material constituents by applying the power rule to vary in association with the thickness path of the plate. Hamilton’s principle is employed to develop the arbitrary equation of motion, which is converted into periodic constants using the Mathieu Hill equation. The derived equation of movement with the help of Floquet’s theorem is applied to generate the instability and stability separations of the FGM plate in the hygrothermal environment. The current proposed results are compared with existing literature results to assess its validity. The free vibration characteristics are reduced by the rise of moisture absorption and the temperature of the FGM plates in the hygrothermal atmosphere. Hence, the influence of increased parameters increases the parametric instability of FGM plates. Temperature rise and moisture absorption regarding the parametric stability and the uncertainty region of the FGM plates are also observed.

In this article fluid-structure interaction of vibrating composite piezoelectric plates is investigated. Since the plate is assumed to be moderately thick, rotary inertia effects and transverse shear deformation effects are deliberated by applying exponential shear deformation theory. Fluid velocity potential is acquired using the Laplace equation, and fluid boundary conditions and wet dynamic modal functions of the plate are expanded in terms of finite Fourier series to satisfy compatibility along with the interface between plate and fluid. The electric potential is assumed to have a cosine distribution along the thickness of the plate in order to satisfy the Maxwell equation. After deriving the governing equations applying Hamilton’s principle, the natural frequencies of the fluid-structure system with simply supported boundary conditions are computed using the Galerkin method. The model is compared to the available results in the literature, and consequently the effects of different variables such as depth of fluid, the width of fluid, plate thickness, and aspect ratio on natural frequencies and mode shapes are displayed.

The aim of this article is to analyze nonlinear electro-magneto vibration of a double-piezoelectric composite microplate-system (DPCMPS) pursuant to the nonlocal piezoelasticity theory. The two microplates are assumed to be connected by an enclosing elastic medium, which is simulated by the Pasternak foundation. Both of piezoelectric composite microplates are made of poly-vinylidene fluoride (PVDF) reinforced by agglomerated carbon nanotubes (CNTs). The Mori-Tanaka model is employed to compute the mechanical properties of composite. Applying nonlinear strain-displacement relations and contemplating charge equation for coupling between electrical and mechanical fields, the motion equations are derived in consonance to the energy method and Hamilton's principle. These equations can't be solved analytically as a result of their nonlinear terms. Hence, the differential quadrature method (DQM) is employed to solve the governing differential equations for the case when all four ends are clamped supported and free electrical boundary conditions. The frequency ratio of DPCMPS is inspected for three typical vibrational states, namely, out-of-phase, in-phase and the case when one microplate is fixed in the DPCMPS. A detailed parametric study is conducted to scrutinize the influences of the small scale coefficient, stiffness of the internal elastic medium, the volume fraction of the CNTs, agglomeration and magnetic field. The results reveal that with increasing volume fraction of the CNTs, the frequency of the structure increases. This study might be beneficial for the design and smart control of nano/micro devices such as MEMS and NEMS.

Nowadays, functionally graded materials (FGM) are widely used in many industrial, aerospace and military fields. On the other hand, the interest in the use of shrink-fitted assemblies is increasing for designing composite tubes, high-pressure vessels, rectors and tanks. Although extensive researches exist on thick-walled cylindrical shells, not many researches have been done on shrink-fitted thick FGM cylinders. In this paper, an analytical formulation for shrink-fitted of axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory is presented. The stresses and displacement fields in thick cylindrical shells are calculated using the real, Repeated and complex roots of characteristic equation. The displacements and stresses resulted are depicted for a case study. The results show that the material composition variation had evident effects on shrink-fit pressure in the intersection area of two fitted tubes. The value of this pressure affects radial and hoop stress distribution in FG circular cylinders walls.

In this article, microstructural characteristics and mechanical properties of Al-Si-Cu/NCP composites were evaluated. Reinforced nanocomposites with 1 wt% nano-clay were fabricated by the method of the stir casting. Stirring times and temperatures were variable parameters to produce specimens. Consequently, the effect of a T6 heat treatment, which contained solutioning at 490 ºC for 5 hrs, quenching, and aging process at 200ºC for 2 hrs, on tribological behavior and compression properties of nanocomposites was inspected. The microstructural observation was conducted by optical microscopy (OM) and the field emission scanning electron microscopy (FESEM). The acquired results demonstrated that nano-clay particles were distributed in the aluminum matrix. The range of Vickers hardness values was 123 to 158 VHN for nanocomposites. The wear resistance of nanocomposites enhanced when the stirring time and temperature increased to 4 mins and 800 ºC, respectively.  The best compressive mechanical properties correlated to the nanocomposite fabricated at 750 ºC and stirred for 2 mins.  The higher stirring time and temperature resulted in the formation of AlSiFe intermetallic phase which reduced the ultimate compressive strength.

A novel semi analytical method is developed for transient analysis of single-lap adhesive joints with laminated composite adherends subjected to dynamical loads. The presented approach has the capability of choosing arbitrary loadings and boundary conditions. In this model, adherends are assumed to be orthotropic plates that pursuant to the classical lamination theory. Stacking sequences can be either symmetric or asymmetric. The adhesive layer is homogenous and isotropic material and modelled as continuously distributed normal and shear springs. By applying constitutive, kinematics, and equations of motions, sets of governing differential equations for each inside and outside of overlap zones are acquired. By solving these equations, the time dependent shear and peel stresses in adhesive layer as well as deflections, stress resultants, and moment resultants in the adherends are computed. The developed results are successfully compared with the experimental research presented in available literates. It is observed that the time variations of adhesive peel and shear stress diagrams are asymmetric for the case of symmetric applied load with high variation rate. Moreover, it is reported that although the magnitude of applied transverse shear force is reduced to 10% of applied axial force, however a significant increase of 40% in the maximum peel stress attained.

In this article, the thermo-elastic behavior of a functionally graded simple blade subjected to the mechanical and thermal loadings is presented, applying a semi-analytical method and a variable thickness cantilever beam model. A specific temperature gradient is employed between the root and the edges of the beam. It is assumed that the mechanical and thermal properties are longitudinal direction dependent pursuant to volume percent of reinforcement. The approach is composed of several steps, including adoption of first-order shear deformation theory, applying beam division accompanying the longitudinal direction, imposing global boundary conditions, and deliberating the continuity conditions. As a result, longitudinal and transverse displacements, and consequently longitudinal, shear and effective stresses are acquired. The analysis is performed for three different distributions of reinforcement particles and pure matrix. Minimum effective and shear stresses distribution belong to the blade with 0% reinforcement at root and 40% reinforcement at tip surface. It has  also been discovered that application of reinforcement particles have reasonable effect on the longitudinal and transverse deflections.

A functionally graded material beam with generalized boundary conditions is contemplated in the present study in order to examine the deformation and stress behavior under thermal and thermo-mechanical load. Three discrete combinations of functionally graded materials have been deliberate in including a wide range of materials and material properties. The variation of material properties has been taken along the height of the beam cross-section as per power law formulation. The formulation has been derived, applying the principle of virtual work in order to acquire governing equations for FG Timoshenko beams. The development of governing equations is made through applying a unique method of unified formulation (Li [16]) in which the displacement variables are arranged in the form of aindependent variable that subsequently reduces the equations to a single fourth order differential equation similar to the equation given by classical beam theoryand is been extended to thermo-mechanical loading in the present work. The transverse shear stress/ strain for Timoshenko beams have been taken care of within this unified formulation. The formulation employed in this research has been generalized for various loading conditions, and in the present work, thermal and thermo-mechanical load has been pondered where temperature has been varied in accordance with the beam height. Exact solutions of the fourth order differential equation for the deformation and stress have been obtained for three types of boundary conditions viz.- Clamped-Free (C-F), Simply Supported (S-S), and Propped Cantilever (C-S). The study has been extended to cover wide range of temperature distribution so as to include uniform, linear and non-linear temperature profiles. Deformation and stresses, axial stresses, and transverse (shear) stresses have been reported for different power law index values.