Mechanics of Advanced Composite Structures
Volume:10 Issue: 1, Winter-Spring 2023

A study on buckling analysis of Marine sandwich panels for interior partition walls with multilayer graphene nanoplatelet (GPL)/polymer composite facesheets is presented in this paper. Three different shapes of square, honeycomb, and re-entrant cellular shape with negative poison ratio are considered for the core layer. It is assumed that facesheets be composed of a polymer matrix reinforced by graphene nanoplatelet (GPL). Halpin-Tsai's micromechanical approach is used to determine the effective Young’s modulus of the top and bottom layers and the rule of mixture for effective Poisson’s ratio and mass density. The wall sandwich plate is modeled based on a new fifth-order shear deformation theory. Hamilton principle is employed to obtain the governing differential equations of motions of plates. The accuracy of the proposed formula and results are verified and proven accurate by the high agreement with the available results in the literature. Based on our results, we indicated the effect of cell configurations of the cellular core on the critical buckling load of marine interior wall sandwich plates. Moreover, the effect of thickness, aspect ratios, graphene nanoplatelet weight fraction, and geometrical parameters on the critical buckling load by the use of Galerkin’s method is illustrated. The findings of this research may be beneficial in creating more efficient engineering applications, especially in the marine and ship industries.

The purpose of this paper is to obtain a model that quickly predicts springback in the three-point bending process of steel / PUR / steel sandwich panels. Firstly, based on the finite element simulation, the springback behavior for different punch radius, length between supports, and foam thickness is established. The results obtained by the finite element analysis show a satisfactory agreement with the experimental results. Secondly, three machine learning approaches are applied, including linear regression (LR), artificial neural network (ANN), and support vector machine (SVM) in order to predict the springback of sandwich panels in the three-point bending process. The performance of these approaches is investigated by using some statistical tools like mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2). The obtained results show that the ANN approach is the best model for predicting the springback of sandwich panels when considering accuracy.

Alumina (Al2O3) nanoparticles were used as the additive for modifying a novolac phenolic resin using the solution mixing method. Different weight percentages of nano alumina 3 and 8 w% were loaded into the resin, called 3ARC and 8ARC nanocomposites, respectively. These nanocomposites were investigated by field emission scanning electron microscopy (FE-SEM), X-ray fluorescence spectroscopy (XRF), energy-dispersive X-ray spectroscopy (EDS), and oxyacetylene flame test (OFT). The FE-SEM images exhibited that at low concentrations (3ARC), the nano alumina particles were dispersed uniformly on the surface of novolac resin; however, at high concentrations, the dispersion was repressed by aggregation in the nanocomposites. OFT proved that with increasing alumina content in the nanocomposite, the back temperature of the sample decreases and thus improves the thermal insulation properties.

In this study, the mechanical properties, microstructure, and fracture behavior of SiC-NanoB4C composites have been investigated with different weight percentages of secondary phase including 0, 0.25, 0.5, 0.75, 1, 2, and 3 wt.% nanoB4C produced by pressureless sintering. At least 1 wt.% of phenolic resin was added to all samples as a carbon source (both as a binder and as a carbon additive). Samples were then sintered for 2h at 2150˚C under an argon atmosphere. The results showed that the composite containing SiC-0.5wt% nanoB4C, sintered at 2150˚C, had the best mechanical properties. In this sample, the relative density was 98.32%, the micro-hardness was 28.6 GPa, Young's modulus was 471.8 GPa and the fracture toughness was 3.7 MPa.√m. Also, the transgranular fracture was observed in the related SEM images. Larger amounts of additives reduced the properties. In order to compare the results better, the temperature and duration of the sintering, the micron-scale size of the B4C additive, the amount of phenolic resin, and the amount of initial sample press were considered as variables.

Composite shells find extensive application in modern civil, aerospace, and marine structures. In order to avoid resonance, such load-carrying shells need to be optimized from a frequency perspective. Composite shell structures often include cutouts for different functional requirements. Obtaining the best combination of design variables like degree of orthotropy, ply orientation, shallowness of the shell, and eccentricity of cutout of laminated shells leads to a problem of combinatorial optimization. This article attempts a numerical study of the free vibration response of composite stiffened hypar shells with cutout using finite element procedure and optimization of different parametric combinations based on the Taguchi approach. Numerical investigations are carried out following the L27 Taguchi design with four design factors, viz., fiber orientation, width/thickness factor of shell, degree of orthotropy, and position of the cutout for different edge constraints. For different shell boundaries considered here, the width/thickness factor emerges as the most influencing factor followed by a degree of orthotropy. The optimum parametric combination for the maximum fundamental frequency of cutout borne stiffened hypar shell is obtained from the analysis.

In this paper buckling response of a sandwich (SW) beam containing functionally graded skins and metal (Type-S) or ceramic core (Type-H) is investigated using a third-order zigzag theory. The variation of material properties in functionally graded (FG) layers is quantified through exponential and power laws. The displacements are assumed using higher-order terms along with the zigzag factors to evaluate the effect of shear deformation. In-plane loads are considered. The governing equations are derived using the principle of virtual work. The model achieves stress-free boundaries unlike higher-order shear deformation theories and is C0 continuous so, does not require any post-processing method. The present model shows an accurate variation of transverse stresses in thickness direction due to the inclusion zigzag factor in assumed displacements and is independent of the number of layers in computing the results. Numerical solutions are arrived at by using three noded finite elements with 7DOF/node for sandwich beams. The novelty of the paper lies in presenting a zig-zag buckling analysis for the FGSW beam with thickness stretching. This paper presents the effects of the power law factor, end conditions, aspect ratio, and lamination schemes on the buckling response of FGM sandwich beams. The numerical results are found to be in accordance with the existing results. The buckling strength was improved by increasing the power law factor for Type S beams while the opposite behavior was seen in type H beams for all types of end conditions. The end conditions played a major role in deciding the buckling response of FGSW beams. Exponential law governed FGSW beam exhibited a little higher buckling resistance for Type S beams, while a little lower buckling resistance was found for Type S beams for almost all lamination schemes and end conditions. Some new results are also presented which will serve as a benchmark for future research in a parallel direction.

Functionally graded material (FGM) is an in-homogeneous composite, constructed from various phases of material elements, often ceramic and metal. This work aims to examine the behavior of free vibration in porous Functionally Graded Beams (FGBs) in 2 directions (2D) by using nth-order shear deformation theory. With the help of Hamilton's principle and Reddy's beam theory, equilibrium equations for free vibration were derived. Boundary conditions such as Simply Supported – Simply Supported (SS), Clamped – Clamped (CC) and Clamped-Free (CF) were employed. A unique shear shape function was derived and nth-order theory was adapted to take into account the effect of transverse shear deformation to get zero shear stress conditions at the top and bottom surfaces of the beam. Based on power law, FGB properties were changed in length and thickness directions. The displacement functions in axial directions were articulated in algebraic polynomials, including admissible functions which were used to fulfill different boundary conditions. Convergence and verification were performed on computed results with findings of previous studies. It was found that the results obtained using the nth-order theory were in agreement and allows for better vibration analysis in a porous material.

This paper is investigated vibration of magneto-electro-elastic (MEE) composite conical shell on a nonlinear elastic foundation and under electric or magnetic potential while the influence of geometrical nonlinearity is taken into account. The conical shell is modeled based on the von Karman approach while the influences of shear deformation and rotary inertia are heeded. Coupled relations of MEE material are utilized to derive the vectors of stress, electric displacement as well as magnetic induction.  Quasi-static Maxwell equations, Gauss' laws as well as thin shell assumptions are used to determine electric and magnetic fields. The nonlinear ordinary differential equation of the shell is derived through the Lagrange approach. Lindstedt-Poincare method and modal analysis are hired in order to obtain nonlinear vibration responses of the MEE composite conical shell. For validation intention, some results of the literature are compared with some results of this study. The effects of several parameters including nonlinear and linear constants of foundation, electric and magnetic potentials, thickness as well as length on the values of fundamental linear frequency, nonlinear parameter, and the curves of nonlinear frequency ratio versus amplitude parameter are investigated. The results show that the increase of the nonlinear constant of elastic foundation or thickness causes the increase of the nonlinear frequency ratio. On the other hand, the nonlinear frequency ratio gets smaller values with an increase in the linear constants of the elastic foundation or length.

This research investigated the effects of graphite content on the sintering behavior of Al-4.5Cu-1.5Mg produced by the shaker mill method. The shaker mill method was chosen because it is able to form uniform nanoparticles in a such short time due to its very high-speed milling. Powder morphology after the shaker mill was investigated. The damaging, fracturing, and cold-welding process during the shaker mill happened in such a shorter time leading to more homogenously dispersed graphite-reinforced Al-4.5Cu-1.5Mg matrix nanocomposite. Sintering under high-purity argon gas for 99.999% was carried out to produce high-density material from 550oC to 620oC. Sintering properties showed that graphite content for more than 0.5wt% decreased sintering density which leads to a lower hardness value. Based on microstructures, a higher amount of graphite is prone to have bigger porosity due to its agglomeration which leads to produced voids between grains. Agglomeration of graphite is still the main challenge for the manufacturing of graphite-reinforced metal matrix nanocomposites. Aluminum carbide Al4C3 was found and it was expected as a result of a reaction between Al and graphite during very high-speed milling. Aluminum carbide acts as an interface between matrix and reinforcement when in certain conditions is able to transfer load from matrix to reinforcement particles leading to improved mechanical properties. Intermetallics of Al-Cu and Al-Mg were also found after sintering.

In this paper, some impact properties including maximum impact force, maximum displacement, specific absorbed energy, and failure mode of composite sandwich panels with aluminum foam core and different skin layers were investigated both numerically and experimentally. To compare the effect of different types of skin layers, in addition to the conventional aluminum layer, glass/epoxy composite with cross-ply and quasi-isotropic layouts was also employed. The experimental low-velocity impact tests were applied using a drop-weight device. All experimental tests were carried out based on the ASTM D7136. The finite element software, ABAQUS/Explicit, was employed to simulate the drop weight impact test of foam sandwiched composite. The finite element model was evaluated by comparing outputs between experimental results and the numerical simulation. Results showed that type of the face sheets and the fiber alignment in the composite surfaces significantly affected the impact behavior such as maximum impact force, failure mode, and absorbed energy. Based on the output results, the composite sheets with a quasi-isotropic skin layer had the highest specific absorbed energy. Moreover, in numerical results, the destruction area indicated more symmetry compared to the experimental ones. Also, the penetration depths of the impactor were completely dependent on the stacking sequence and type of top layer.

The behavior of various CNT distributions with agglomeration effects on FG plates is investigated in this paper under static loading. Here, to model the FG plate third-order shear deformation theory has been used and a FEM code has been developed. In the current higher-order shear deformation theory, transverse shear stresses are represented by quadratic variation along the thickness direction, resulting in no need for a shear correction factor. The properties of randomly oriented nano-inclusions are estimated using the two-parameter agglomeration model of Eshelby-Mori Tanaka. Next, the present approach is implemented with the FEM by employing a C0 continuous isoparametric Lagrangian FE model with seven nodal unknowns per node. The static response of CNT reinforced composite plate with the influence of inclusions is explored by altering the agglomeration parameters and through-thickness CNT distribution pattern. The obtained results suggest that ignoring the agglomeration effect on CNT may result in erroneous results for various static responses. Since the author could not find any results in the static response of CNT-reinforced plates with the agglomeration effect, the proposed model is validated with the results corresponding to the isotropic plate. The impact of several agglomeration phases on the static behavior of a square plate is then studied parametrically.

Radial basis functions (RBFs) with modified radial distance are proposed for vibration analysis of functionally graded materials (FGM) rectangular plates. The displacement field with five variables higher-order shear deformation theory (HSDT) is considered. The governing differential equations (GDEs) and boundary conditions are obtained using Hamilton's principle. The governing differential equations formulations are solved via strong-form solutions. The rectangular plates are analyzed in the framework of the RBF-based meshfree method. The novelty of the present modified method is to analyze the square and rectangular plates without changing the shape parameters. Here, the seventeen different RBFs are available in various literature to demonstrate the accuracy and efficiency of the present method in terms of the number of nodes and computational time. The results of several numerical examples have shown that the present modified RBF-based mesh-free method can lead to much more accurate solutions. Computational times of different RBFs are also analyzed.

n this research, the dry sliding wear behaviour of the Mg-TiO2 nanocomposite is analyzed by conducting a wear test using a pin-on-disc wear testing machine under normal atmospheric conditions. The process parameters considered during the test are the weight fraction of TiO2 nanoparticles, normal load, and sliding speed. The sliding distance and wear track diameter are maintained constant at 1500 m and 90 mm respectively during the test. The performance measures are cumulative wear and coefficient of friction. Taguchi-based Grey relational analysis is employed in this study to optimize the performance of the wear behaviour of the nanocomposite. The design of experiments considered in this study is L9 orthogonal array with each process parameter for three levels. Grey relational grade (GRG) is computed for each experiment and it was found that the maximum GRG of 0.825 is obtained for the process parameter combination A3B2C1 which corresponds to 5wt% TiO2, 1 kg normal load and 1.5 m/s sliding speed respectively. The initial GRG estimated is compared with the predicted and experimental values for the optimum process parameters and it was found that there is an improvement in GRG by 2.2% and 0.77% respectively. ANOVA (Analysis of variance) is carried out to estimate the process parameter that influences the wear behaviour of the nanocomposite significantly and later concluded that the process parameter normal load is the most significant factor other than any other factors.

The temperature-dependent properties and the effect of non-local elasticity in the presence of a magnetic field have been studied in an infinitely long solid conductive circular cylinder. The issue arises in the setting of two relaxation times in extended magneto-thermoelasticity theory. In the presence of a uniform magnetic field in the direction of the axis, the lateral surface is traction-free and subjected to known temperatures. Techniques are employed to determine the answer in the Laplace transform domain. A numerical method based on Fourier series expansions is used to carry out the inversion operation. In addition, graphs depict comparisons to highlight the influence of various elements such as the difference in times and the effect of the non-local coefficient and Empirical material constant.

The current investigation deals with the effect of carbon nanotube (CNT) agglomeration on the free vibration behavior of nanocomposite plates created by inserting various graded distributions of carbon nanotube (CNT) in a polymeric matrix. In this study, affected material properties because of the CNT agglomeration effect were estimated first according to the two-parameter agglomeration model based on the Eshelby-Mori-Tanaka approach for randomly oriented carbon nanotubes, and then a FEM code has been developed to model the FG plate using third-order shear deformation theory. In the used higher-order shear deformation theory, transverse shear stresses are represented by quadratic variation along the thickness direction, resulting in no need for a shear correction factor. Next, the present approach is implemented with the FEM by employing a C0 continuous isoparametric Lagrangian FE model with seven nodal unknowns per node. Finally, the effect of various levels of agglomeration by altering the agglomeration parameters, different CNT distribution patterns across the thickness direction, and various side-to-thickness ratios along with various boundary conditions on the free vibration response of CNT reinforced composite plates explored parametrically. The generated result shows that the CNT agglomeration effect has a significant impact on the natural frequencies of the nanocomposite plate.

The paper demonstrates the applicability of micro indentation as a sensitive method for detecting the effect of the nature of oxides as fillers on the properties of epoxy coatings in comparison with conventional physicochemical methods of infrared spectroscopy (IR) and thermogravimetry (TGA). This applicability was discovered when studying the surface mechanical properties (hardness, elastic modulus, and creep) of epoxy coatings filled with nanoscale oxides TiO2, SiO2, and ZnO. The behavior of the mechanical characteristics of the materials under thermal cycling at temperatures ranging from −40 to +60 °С was evaluated by instrumented indentation with the use of a Fischerscope HM system after 5 and 10 cycles. It is shown that the 10% addition of TiO2 oxide increases the values of hardness and the elastic modulus by 5 and 15%, respectively, while the addition of SiO2 and ZnO decreases them by 7 and 5%. The micromechanical properties of the studied materials depend on the time of the increase in mechanical loading. All the compositions exhibit viscous properties consisting of hardness decrease with the decreasing rate of loading. Thermal cycling decreases the hardness and elastic modulus of the unfilled epoxy coating and those containing SiO2 and ZnO by 12 and 18%, respectively, and it ensures the self-restoration of the hardness of the TiO2-filled coating. All the additives decrease the creep index. Thermal cycling increases the creep index for all the materials under study.

With the progress of various industries, the ever-increasing production of polluting wastewater has faced mankind with the concern of preserving the environment and providing clean water. The simultaneous use of adsorbents such as natural zeolite and nanophotocatalysts is one of the attractive methods. By doing this, while eliminating the limitations of each, synergy in properties occurs and the performance of pollution removal is improved. In this article, TiO2/CuO nanocomposite was deposited on natural zeolite particles. The produced samples were evaluated and compared with different analyses. The results showed that the presence of the TiO2-7.5% CuO (TC) nanoparticles has improved the ability to absorb UV light despite reducing the specific surface area. The performance of the zeolite-TC combination on the removal of methyl orange (MeO) showed acceptable results. The zeolite sample containing 15%TC with a specific surface area of 29 m2/g and band gap of 3.08 eV removed 93% of MeO dye after 120 min.

The current work involves the development of short jute fiber-reinforced polymer matrix composites (PMC) filled with Cenosphere. The short jute fibers were alkali-treated, and proposed composites with both untreated and alkali-treated fibers were prepared. Both kinds of composites have had their erosion wear behavior investigated. For the erosion investigation, an air jet-type test rig was used, and Taguchi's orthogonal arrays were used in the design of trials. The Taguchi technique was used to find the best parameter settings for minimizing erosion rate. The effect of input factors (angle of impact, velocity of impact, and filler percentage) on the erosion resistance of proposed composites was evaluated and statistically analyzed using ANOVA. The size of the erodent, impact velocity, impingement angle, and filler content all have a substantial impact on the wear rate of both types of composites, according to the findings. It is found that velocity of impact (p =0.089) and filler (p =0.246) have a significant impact on erosion wear rate for group A composites and standoff distance (p= 0.194) and filler content (p =0.391) had a significant impact on erosion rate for group B composites. With the addition of the Cenosphere, the erosion behaviour of the samples was significantly improved. The novelty of the present work lies in harnessing an industrial wast cenosphere into a useful filler for PMC in tribological applications.