Mechanics of Advanced Composite Structures
Volume:9 Issue: 2, Summer-Autumn 2022

This study describes the use of duck bone gelatin in a taro starch mixture to produce biodegradable films. Films were produced using duck bone gelatin in various percentages (0%, 5%, 15%, 25%, and 35% of the total solid weight) and added with glycerol as a plasticizer and the solution casting method. Parameters observed were tensile strength, percent elongation, thickness, moisture content, and surface morphology of the product was observed by scanning electron microscopy (SEM) analysis. Adding duck bone gelatin to biodegradable films based on taro starch had a significant effect (p<0.05) on tensile strength, percent elongation, and moisture content, but it did not affect (p>0.05) on thickness. The biodegradable film with a 5% duck bone gelatin concentration produced the highest tensile strength of 11.333 MPa and the highest percent elongation of 17.100%. Thickness values for all additions of duck bone gelatin concentration ranged from 0.191 to 0.194 mm, and the highest moisture content produced at 35% duck bone gelatin concentration was 4.079%. The surface morphology of the biodegradable film with a 5% duck bone gelatin concentration with the highest tensile strength value shows a flat, solid but slightly rough cross-section which may be caused by the flexibility of the gelatin film.

Carbon fiber reinforced plastics (CFRP) are now being used in primary structures of airplanes, ships, and automotive engineering and for applications that demand sustained high reliability and strength during long-term operations. The present work provides a three-dimensional (3D) model that has been established for the simulation of the multidirectional carbon fiber reinforced plastic (CFRP) composite layer which enables understanding of the mechanical properties at failure using finite element simulation software ANSYS. The matrix is considered isotropic and elastic-plastic. Moreover, the carbon fiber is considered transversely isotropic and linear elastic for the finite element modeling. The maximum stress-strain criterion is used to determine the failure of fiber and matrix of composite layer for both analytical and modeling analysis. The modeling result shows that the elastic modulus in fiber orientation is significantly higher. Numerical and analytical results of nonlinear mechanical stress and the distribution on the multilayer show good agreement with experimental results.

In this paper, the nonlinear torsional vibrations and internal resonances of nanorods are investigated by considering the surface energy effects. For this purpose, Hamilton’s principle is implemented to derive the nonlinear governing equation of motion based on the von-Kármán relations. Hamilton's principle includes the strain energy and the kinetic energy of the nanorod surface and bulk. The strain and kinetic energies of the nanorod bulk are obtained using the classical theory of elasticity, and those of the nanorod surface are obtained using the surface elasticity theory. The surface energy parameters, including the surface density and the surface Lame constants, are included in the equations by the surface elasticity theory. Then, the multi-mode Galerkin method is used to convert the partial differential equation of motion to an ordinary differential equation. The Multiple-scale method is employed to solve the governing equations of motion for fixed-free and fixed-fixed end conditions. To investigate the technique presented in this paper, circular nanorods made of aluminum and silicon have been used. The effect of surface energy parameters on the torsional frequencies of nanorods is investigated for different values of length, radius, frequency number, and amplitude of the nonlinear vibrations. In addition, the cases in which internal resonances occur are reported, and some numerical data are given. The results obtained in this research may be helpful for the better design of nanoelectromechanical devices such as nano-bearings and rotary servo motors.

The article presents non-axisymmetric free vibration results of porous bi-directional functionally graded (BDFG) plates. The bi-directional grading index changes with the thickness (z-) and radial (r-) directions and porosity distributions are classified as uniform or non-uniform type. A displacement field model is formulated based on First-order Shear Deformation Theory (FSDT). Hamilton’s principle is used to develop the governing equations for porous BDFG plates. The spatial discretization of the proposed mathematical model in five variables is carried out using the fast converging Differential Quadrature Method (DQM).  The numerous examples demonstrate the accuracy and stability of the present DQM model by comparing the reported results available in the literature. The influence of aspect ratios, boundary conditions, and porosity distributions on the free vibration response of porous bi-directional functionally graded material plates is investigated intensively. These findings reveal that increasing the porosity volume fraction significantly impacts the mechanical properties of porous bi-directional functionally graded plates.

Hybrid laminates have been utilized in vast applications, namely aircraft, automotive, and other areas of light weight and high strength requirement. There are various types of hybrid laminates and an assessment of these laminates for their application is necessary. Experimental testing as per ASTM is expensive since it is destructive testing. In addition, the hybridization of basalt, a promising fibre along with other fibres has shown better laminate properties. Basalt-carbon epoxy hybrid laminated composites are a comparably inexpensive and sustainable alternative to conventional carbon fibre epoxy composites. Thus, in this paper, the evaluation of the new and advanced basalt-carbon epoxy hybrid laminated composites under static loading was conducted using Finite Element Analysis. Mechanical properties of basalt-carbon epoxy hybrid laminated composites such as tensile and compression strength, flexure strength, interlaminar, and in-plane shear strength were evaluated through different static test simulations. Specimens having different stack-up sequences and fibre orientations were analysed for failure based on Tsai-Wu failure criteria using commercial finite element software ANSYS Composite Pre-Post (ACP) and ANSYS Mechanical. The outcome of this work shows that laminates with basalt fibres on the inner side and carbon fibres on the outer side provided a better alternative with around 90-98% equivalent strength to pure carbon laminates in various mechanical strength tests. In addition, the lay-up of specimen C2 [02C/+45B/0B]S was found to be the optimal stacking arrangement. Using specimen C2 as a substitute to pure carbon fibre laminate not only provides almost equivalent strength but also reduces the cost by up to 40%. The comparable strength property of specimen C2 was due to the placement of 0o carbon fibre at the outer faces of the composite.

This study investigates the size-dependent free vibration analysis of multi-layered graphene sheets based on exponential shear deformation theory (ESDT), which considers the effects of rotary inertia and transverse shear deformations. In order to capture the effects of length scale parameter on the vibrational behavior of the structure, modified strain gradient elasticity theory is utilized. An elastic multiple-plate model is assumed in which the nested plates are coupled with each other through the van der Waals interlayer forces. The governing equations of motion are derived by implementing Hamilton’s principle and then are solved with the Navier approach. To verify the present model, results in specific cases are compared with the available papers in the literature and excellent agreement is seen. Finally, the effects of various parameters such as aspect ratio, thickness ratio, Winkler modulus, shear modulus, and size effects on the natural frequencies of a multi-layered graphene sheet are presented and discussed in detail.

Friction Surfacing (FS) is a method to create coatings on surfaces, a commonly used approach for improving the surface properties of materials. This study investigated the deposition of an Al/SiC composite coating of AA2030 aluminum alloy and 250 μm SiC particles on a plain carbon steel substrate by FS. Holes of a 3.5 mm diameter were made in the AA2030 rod and filled with SiC powder. This consumable rod was then pressed on the surface of an St37 plate with an axial force of 450 N. The rod was rotated and moved around to coat the surface of the St37 substrate with a layer of Al/SiC composite. The results showed that SiC particles break down and get evenly dispersed over the surface. The deposited composite coating offered 41.6% better wear resistance and up to 70% better corrosion resistance than the non-composite coating. The electrochemical impedance analysis showed two time constants in the Nyquist plots.

Anti-reflective (AR) coatings that reduce surface reflectance have attracted more attention in a variety of applications. In this work, the structural and optical properties of MgF2/Cu bilayer film as an AR coating on an aluminum substrate deposited by sputtering were investigated. The structural and morphological properties were studied by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) respectively. The XRD patterns showed that the coating is composed of pure and crystalline phases. The FESEM and map images show a smooth coating with a uniform distribution of elements. The optical properties of the coating have been investigated by studying the reflectance spectra of the coating. The coverage showed the lowest reflection at high wavelengths. The adhesion strength of the films on the aluminum substrate was determined by a cross-cut test, which obtained a value of 5B for each coating, which indicates the excellent strength of the coatings.

This study explores the bending analysis of porous functionally graded material (FGM) rectangular plate resting on two parameters elastic foundation based on the higher-order shear deformation theory (HSDT) and subjected to various types of transverse load.The material properties of porous FGM rectangular plates are assumed to be graded in the thickness direction according to modified power-law distribution in terms of the porosity fractions and grading index. The energy principle develops governing differential equations (GDEs) of the plate. The derived formulation is implemented numerically using the strong formulation, and the multiquadric radial basis function (MQ-RBF) based meshfree method for discretizing the GDEs. The MQ-RBF improved by modifying the radial distance between the interpolation. A code has been developed in MATLAB (2019) to obtain the results. The influence of the span to thickness ratio, aspect ratio, transverse loading type, porosity fraction, grading index, and elastic foundation coefficients on the bending response of porous FGM rectangular plate. New numerical results can provide benchmarks for future analyses of porous FGM plates on elastic foundations.

This paper is focused on the study of nonlinear vibration of rotating laminated composite cross-ply cylindrical shells on a nonlinear rotating elastic foundation. In this study, FSDT is employed while the geometrical nonlinearity of the cylindrical shell is modeled considering the von Karman approach. It should be mentioned that this study is accomplished considering the influences of initial hoop tension as well as Coriolis and Centrifugal accelerations. The nonlinear equation of the rotating laminated composite cross-ply cylindrical shell is extracted via the Ritz method and then is written in the state space form. Then, modal analysis and the multiple scales method are applied to the nonlinear vibration equation in the state space form to obtain relations for nonlinear forward and backward frequency ratios. Validation of the results of this study is investigated considering some results published in the literature and good agreement is observed. Finally, the effects of the nonlinear and linear constants of the rotating foundation, radius, total thickness, length, and rotation speed on the linear frequencies, nonlinear parameters, and the curves of nonlinear frequency ratios versus amplitude parameters are acquired. The results show that the increase of the nonlinear constant of the rotating foundation doesn’t influence the linear frequencies. Besides, linear frequencies increase with increase of the linear constants of the rotating elastic foundation and decrease with increase of the radius or total thickness. Furthermore, the increase of the nonlinear constant of the rotating elastic foundation or total thickness leads to an increase in nonlinear parameters and nonlinear frequency ratios. Conversely, the increase of the linear constants of the rotating foundation or the radius leads to a decrease in nonlinear parameters and frequency ratios. Moreover, the increase in amplitude parameters leads to an increase in the nonlinear frequency ratios.

In this paper, the author studied free transverse vibration of a thin isotropic simply-supported functionally graded (FG) rectangular plate with porosity effect based on classical plate theory. The plate is considered to be elastically restrained against rotation. It is assumed that the material properties of the graded plate are porosity-dependent. An even porosity distribution is considered for analysis purposes. Due to the asymmetry of material in the thickness direction, the neutral surface is not the same as the geometrical mid-plane of the plate. The concept of the physical neutral surface of the FG plate along with classical plate theory is used to formulate the problem. Hence, the physical neutral surface is taken as the reference plane. The first three dimensionless frequencies of the plate are obtained using the Rayleigh-Ritz method. Boundary characteristic orthogonal polynomials (eigenfunctions), generated using the Gram-Schmidt process, are used in the Rayleigh-Ritz method. A parametric study shows that porosity and material distribution parameters have remarkable effects on the free vibration response of the plate. Results are compared with those of simply-supported FG plates.

This study aims to examine the mechanical and tribological behaviors of short glass fibers (SGFs) and short carbon fibers (SCFs) reinforced single-layer hybrid epoxy composites. Here, the hybrid composites reinforced SGFs and SCFs in two different ratios (5 wt.% and 10 wt.%) were produced by the hand layup method. In addition, only glass or carbon fiber reinforced composites were produced in the same proportions to compare with hybrid composites. To investigate the flexural bending strength of composites (E5GF, E10GF, E5CF, and E10CF) and hybrid composites (E5GCF and E10GCF), 3-point bending tests were conducted. Izod impact tests were performed to analyze the impact energy absorbing behaviors of specimens. The wear performance of samples was assessed by using 10 and 20N loads. Moreover, the morphology of broken and worn surfaces of samples was analyzed by a scanning electron microscope. According to test results, E10GCF hybrid composites had nearly 27.36% and 29.67% better flexural strength and impact energy-absorbing compared to (E10GF) glass fiber reinforced composites, respectively. However, only 10 wt.% carbon-reinforced composites showed the highest wear resistance and smooth worn surface among all the samples. Therefore, for structural applications, hybrid epoxy composites can be the favorite but for tribological purposes reinforcing epoxy with only carbon fiber should be advantageous.

Cone shells due to their special aerodynamic shape are the main component for air-space transport and submarine structures. The application of composite materials in these structures leads to achieving lower strength-to-weight ratios. Due to the type of application, most of these structures are under external pressure. The purpose of this paper is to achieve an empirical relationship between buckling pressures and the impact of various factors on the strain. The four factors that are going to be evaluated in this article are cone size, number of layers, number of layers of longitudinal reinforcement (Stringer), and number of circular reinforcement (Ring). To achieve this goal truncated composite cone samples, longitudinal and circular reinforcements are made of woven glass fiber with epoxy resin. The experiments are based on the RSM method in optimization. The results of this paper showed that the longitudinal reinforcements are not effective on buckling pressure.

In this study, the effect of different molar ratios of primary powders and arc melting setting time on the synthesis of Ti3SiC2 powder has been investigated. For this purpose, Silicon Carbide (SiC), Titanium (Ti), graphite (C) and aluminum (Al) powders with molar ratios of 3Ti:1.2SiC:0.8C, 3Ti:1.2SiC: 0.8C:0.1Al and 3Ti:1.2CiC:0.8C:0.3Al were mixed by a planetary mill under an argon atmosphere for 5h. The resulting mixture was formed with a press and subjected to arc melting at 1, 3, 5, and 10s. In samples containing Al additive, the purity of Ti3SiC2 increases with increasing arc melting setting time up to 5s, and the purity decreases with increasing the arc time. The best result was obtained in the sample 3Ti:1.2SiC:0.8C:0.1Al containing 83.6 wt% of Ti3SiC2, which was obtained during the 5s arc melting.

Nowadays fire has become one of the large prominent threats to buildings and concrete structures in the world. In this research, an experimental study was performed to examine the spalling phenomenon and residual mechanical properties of fiber toughened Ultra-High-Performance Concrete (polypropylene (PPF) and steel fibers (SF)). Moreover, the effect of high temperatures, namely, 250 ºC and 500 ºC for 2.5 hours and 5 hours has been studied for each mix of samples. This research discussed the results of compressive strength, flexural tensile strength, and splitting strength. Weight loss of the specimens and the effect of hybrid fibers incorporation (PPF and SF) behavior Ultra-High-Performance Concrete at high temperature were studied. The study concludes that the residual resistance of UHPC decreases as the temperature increases. Also, increasing the heating time resulted in lowering the residual concrete strength. The addition of the optimum percentage of PPF (0.8%) results in a remarkable effect on decreasing the risk of spalling in the UHPFRC. Polypropylene fibers provide channels in the concrete for this reduced pore pressures and the risk of spalling. Incorporating hybrid fiber seems to enhance the resistance of UHPFRC to explosive spalling due to the significant increase of permeability in UHPFRC. In addition to that, the steel fibers will increase the ductility of the UHPFRC and render it more able to withstand the high internal pressures which were experimentally confirmed by this work.

This paper investigates the influence of temperature on the active vibration control of laminated composite cantilever beams using collocative experimental and simulation techniques. The system identification toolbox of the MATLAB simulation tool is utilized to obtain the transfer function of the plant model. The adequate vibration attenuation of the glass-epoxy cantilever beam operating in various thermal environments is achieved using the proportional (P) and proportional-integral-derivative (PID) controllers. The vibration attenuation characteristics of the developed control algorithms are comprehensively investigated for a wide temperature range of –20 °C to 60 °C using PZT-5H patches. Particular emphasis is given to the vibration control of the fundamental natural frequency of the laminated composite cantilever beam. The obtained results of open and closed-loop models are presented in both time and frequency domains. The results indicate that for all the temperatures considered, the PID controller is found to be more effective in vibration attenuation than the P controller. The vibration attenuation performance of the cantilever beam considerably improved at the higher magnitude of temperature values. The natural frequency of the system is reduced continuously with an increase in temperature.

The effect of friction and rotational speed parameters changes on the transient thermoelastic response of a rotating functionally graded cylinder with a short length subjected to thermal and mechanical loads are studied based on the First order shear deformation theory (FSDT). It is assumed that the cylinder is located on a friction bed and is rotating due to an external torque. The material property is assumed to be variable along radius according to a volume fraction distribution. Because temperature changes are unstable the changes in parameters are applied when the cylinder has reached a steady state. In the following, radial, longitudinal and angular displacement diagrams, as well as effective stresses due to changes in coefficient of friction and rotational velocities for longitudinal and radial directions, are drawn. The results show that these changes have significant effects on the measured parameters and in many industrial applications, these coefficients are not constant during the work period and have changed.

A simply supported (SS) functionally graded piezoelectric material (FGPM) plate in a 2D domain has been analyzed for stress and displacement by a Semi-analytical approach. In-plane variation in stresses and displacements is assumed to be trigonometric. The elasticity approach is used and no simplifying assumption is made on the stress and displacement fields in the through-thickness direction. The FGPM plate is subjected to a transverse electro-mechanical load whose intensity remains constant in the out-of-plane direction. Thus, the plate is under plane stress and plane strain conditions of elasticity. Exponential law or power law has been considered for smooth gradation of material properties in the through-thickness direction. The formulation is a set of first-ordered ordinary differential equations (ODE), which has been solved using numerical integration. Exact outcomes in the literature have been used to correlate and validate the present model results. Additional investigation has been carried out on FGPM plates and beams and results are provided for future reference.