Functionally Graded Materials Research Articles

Exploring Advanced Functionalities of Carbon Fiber-Graded PEEK Composites as Bone Fixation Plates Using Finite Element Analysis.

This study aims to address the challenges associated with conventional metallic bone fixation plates in biomechanical applications, such as stainless steel and titanium alloys, including stress shielding, allergic reactions, corrosion resistance, and interference with medical imaging. The use of materials with a low elastic modulus is regarded as an effective approach to overcome these problems. In this study, the impact of different types of chopped carbon fiber-reinforced polyether ether ketone (CCF/PEEK) functionally graded material (FGM) bone plates on stress shielding under static and instantaneous dynamic loading was explored using finite element analysis (FEA). The FGM bone plate models were established using ABAQUS and the user's subroutine USDFLD and VUSDFLD, and each model was established with an equivalent overall elastic modulus and distinctive distributions. The results revealed that all FGM bone plates exhibited lower stress shielding effects compared to metal bone plates. Particularly, the FGM plate with an elastic modulus gradually increased from the centre to both sides and provided maximum stress stimulation and the most uniform stress distribution within the fractured area. These findings offer crucial insights for designing implantable medical devices that possess enhanced mechanical adaptability.

POD method for solving elastodynamics problems of functionally gradient materials based on radial integration boundary element method

Functionally graded materials (FGMs) are widely utilized due to their excellent mechanical properties, prompting a need to explore the dynamic response of FGMs. To accurately and efficiently analyze elastodynamics problems, the radial integration boundary element method (RIBEM) is coupled with the proper orthogonal decomposition (POD) method in this paper. The POD method can transform a high-dimensional model into a low-dimensional system with high precision. Using the basic solution (Kelvin solution), the governing partial differential equation for the linear elastic dynamics problem of FGMs is transformed into a boundary-domain integral equation. The radial integration method is employed to convert the domain integral arising from material inhomogeneity and inertia terms into an equivalent boundary integral. This establishes a solution for the elastic dynamics problem of FGMs without the need for internal grid RIBEM. The Newmark time integration scheme is applied to solve the second-order ordinary differential equations. The displacement field obtained by RIBEM is utilized to construct the snapshots matrix, from which the POD reduced-order model is established. Numerical examples validate that the POD method significantly reduces the model's order, enhancing computational efficiency while also demonstrating the high accuracy of the POD method.

A strong, machinable, and multifunctional Ti3SiC2-(Ti3SiC2-Cf) composite: Gradient architecture and mechanical properties

Ti3SiC2, as one of the most typical MAX ceramics, has been extensively studied as a potential high-temperature structural material. However, the restrictive relations between strength and toughness of Ti3SiC2 and Ti3SiC2-based materials have hampered their industrial applications. Herein, we reported the successful fabrication of Ti3SiC2–(Ti3SiC2–Cf) functionally graded materials (FGM) via hot-press sintering Ti3SiC2 and short Cf-derived preceramic papers. The microstructure evolution as well as the effect of sintering temperature on phase composition and interfacial reaction were investigated. Flexural strength and fracture toughness from ambient temperature to 1000 °C of the graded composites were determined to evaluate the mechanical performance. The results have shown that chemical reactions occurred between carbon fibers and Ti3SiC2 matrix, which leads to the formation of SiC interfaces with strong covalent bonds. The newly developed Ti3SiC2–(Ti3SiC2–Cf) graded composite materials exhibited excellent comprehensive performance as compared to that of monolithic Ti3SiC2. The flexural strength and fracture toughness of the graded composite at room temperature can be reached to 526 MPa and 7.46 MPa m1/2, respectively. However, there is no significant change in flexural strength and fracture toughness from RT to 1000 °C. The fracture micrographs also reveal that fiber breaking、pulling out and debonding are the primary mechanisms that contribute to the superior mechanical properties of composites. The exceptional performance demonstrated in Ti3SiC2–(Ti3SiC2–Cf) graded materials also makes them attractive choices for a variety of heatproof devices in aerospace sectors.

Artificial neural networks coupled with numerical approach for the stability prediction of non-uniform functionally graded microscale cylindrical structures

Functionally graded materials (FGMs) have garnered significant attention in research due to their potential for creating innovative materials with diverse applications. This study focuses on investigating the behavior of steel-concrete functionally graded structures under axial loading, specifically exploring nonlinear buckling. The research considers cylindrical structures with simply-supported boundary conditions and analyzes four different configurations with varying thickness. The governing equations are derived using the modified couple stress theory, incorporating assumptions of nonlinear von-Kármán theory coupled with classical beam theory. Numerical solutions are obtained using the general differential quadrature (GDQ) method. A notable aspect of this work is the use of Artificial Neural Networks (ANN) to predict nonlinear buckling forces, greatly enhancing the accuracy and efficiency of the predictions. This approach offers a novel method for analyzing concrete structures. The results are validated by comparing them with data from other published works, using dimensionless parameters for consistent comparisons. The findings provide a comprehensive analysis of various parameters, including wall thickness function and porosity, on the buckling stability of the cylindrical structure. Both numerical and ANN approaches are employed to report the effects. The study concludes that the uniform thickness cylinder exhibits the highest resistance to axial loading, resulting in buckling.

Mathematical Formulation and Numerical Simulation of the Mechanical Behavior of Ceramic/Metal (TiB/Ti) FG Sheets Subjected to Spherical Indenter

The main motivation for the present work is to provide an improved description of the response of Functionally Graded (FG) structures under a spherical indenter, considering material nonlinearities. This is achieved through the implementation of elastoplastic material behavior using integration points to avoid the division of the structure into multiple layers. The current paper proposes a numerical investigation into the mechanical response of functionally graded materials (FGMs) in contact with a rigid hemispherical head indenter. The numerical model considers both the Mori–Tanaka model and self-consistent formulas of Suquet to accurately model the smooth variation of material properties through the thickness of the elastoplastic FG material. The model execution involves a UMAT user material subroutine to implement the material behavior into ABAQUS/Standard. The user material UMAT subroutine is employed to introduce material properties based on the integration points, allowing for an accurate representation and analysis of the material’s behavior within the simulation. The developed numerical model is validated through a comparison with experimental results from the literature, showing a good correlation that proves the efficiency of the proposed model. Then, a parametric study is conducted to analyze the effect of the indenter dimension, the indentation depth and the gradient index on the indentation force, the contact pressure evolution, von Mises equivalent stress and equivalent plastic strain distributions located on the vicinity of the contact zone. The results showed that the elastoplastic response of TiB/Ti FG plates is significantly influenced by the gradient index, which determines the properties of the FG composite through the thickness. These results may help development engineers choose the optimal gradation for each industrial application in order to avoid contact damage.

Free vibration analysis of functionally graded shallow shells with variable thickness and physical neutral surface effects

The study and manufacture of functionally graded (FG) shallow shells with the variable thickness are essential for the actual application of these types of structures. Previously, many researchers have developed different approaches to analyzing the mechanical behaviors of the FG structures, in which the thickness parameter has been assumed to be constant. Moreover, studies on these types of structures with the variable thickness are still quite limited. For this reason, this paper provides an effective and simple approach via mathematical formulations for analyzing the free vibrational responses of FG shallow shells with the variable thickness. Also, the presence of porosities that can occur during the fabrication of FG materials is considered. One of the highlights here is to consider the influence of the physical neutral surface. Before conducting the analysis of these FG structures, firstly, it is important to establish governing equations based on the classical shell theory. These essential equations are used for the FG shallow shells. Then, by setting the Navier solution with the help of simply supported boundary conditions, the natural frequencies are obtained. Finally, the numerical examples will be given to illustrate the effects of porosity coefficient, material and geometry parameters as well as the physical neutral surface on the natural frequencies. In addition, two numerical examples for verification will also be performed and thereby show the accuracy of the current method and model. It is hoped that the main results of this study can be useful not only to designers and researchers but also to be extended to more complex problems.

Exploration into the microstructural, mechanical, and biological characteristics of the functionally graded 3Y-TZP/Ti6Al4V system as a potential material for dental implants

This study investigated the mechanical, microstructural, and biological properties of 3Y-TZP/Ti6Al4V functionally graded material (FGM) fabricated by the spark plasma sintering (SPS) method. For this purpose, 11 layers of 100-x vol% Ti6Al4V/x vol% Yttria stabilized zirconia (YSZ) (x = 0 to 100) were sintered at 1450 °C and a pressure of 30 MPa for 8 min. To investigate the properties of each layer in more detail, 11 batches of 100-x vol% (Ti6Al4V)/x vol% YSZ (x = 0 to 100) composites were sintered separately with the same sintering conditions mentioned for the FGM sample. Phase identification of the FGM sample showed the formation of Ti3O, c-ZrO2, and Zr3O phases as by-products. A schematic model was proposed for the formation of the mentioned phases with the aid of thermodynamic calculations. The formation of these phases was confirmed by microstructural and elemental tests. The results of the relative density of the samples showed that these values were obtained for each layer above 99%. The microhardness of 590 ± 18 Vickers was obtained for Ti6Al4V; by increasing the amount of 3Y-TZP, this value reached 1510 ± 24 Vickers for the YSZ sample. The fracture toughness value for Ti6Al4V was 39.2 ± 2 MPa m0.5, which was significantly reduced to 4.84 ± 1 MPa m0.5 by adding 10 vol% YSZ. After that, with the further increase of YSZ, this value increased slowly. A similar trend was observed for the bending strength of the samples. By increasing 3Y-TZP from 0 to 30 vol%, the bending strength was decreased from 1556 ± 32 to 272 ± 62 MPa. By further increasing the amount of 3Y-TZP from 30 to 100 vol%, an increase in the bending strength was observed in the samples, which reached 1180 ± 71 MPa for the YSZ sample. The FGM sample showed a brittle fracture despite a metal layer, but a higher bending strength (982 ± 44 MPa) was obtained for this structure than the composite samples. The biological results show that increasing YSZ content leads to a decrease in antimicrobial activity. Additionally, all samples demonstrated high biocompatibility based on MTT cytotoxicity tests after 1 and 7 days of culture.

Modelling functionalized drug release for a spherical capsule

Advances in material design have led to the rapid development of novel materials with increasing complexity and functions in bioengineering. In particular, functionally graded materials (FGMs) offer important advantages in various fields of application. In this work, we consider a heterogeneous reaction-diffusion model for an FGM spherical drug release system that generalizes the multi-layer configuration to arbitrary spatially-variable coefficients. Our model proposes a possible form for the drug diffusivity and reaction rate functions exhibiting fixed average material properties and a drug release profile that can be continuously varied between the limiting cases of a homogeneous system (constant coefficients) and two-layer system (stepwise coefficients). A semi-analytical solution is then used to solve the model, which provides closed-form expressions for the drug concentration and drug release profiles in terms of generalized Fourier series. Our results show how the release rate of the proposed FGM drug release system can be controlled and continuously varied between a fast (homogeneous) and slow (two-layer) release while maintaining the same averaged values for the diffusivity and reaction rate.

Resistance of ceramic / metal Functionally Graded Materials in the flame of a combustion chamber under harsh thermal and environmental conditions

Ceramic/metal Functionally Graded Materials (FGM) are efficient systems to increase the performance of materials used in thrusters, which operate under harsh thermal and environmental conditions. In this context, an experimental study has been carried out to firstly develop the FGM using atmospheric plasma spraying process and secondly investigate the resistance of the materials in the flame of a combustion chamber under oxidising atmosphere. Several configurations of FGM have been tested, in order to analyse the influence of the different layer thickness and composition, on their resistance. The link between the different FGM configurations and their endurance in the combustion flame has been established. The best performance was demonstrated with a thin ceramic layer of rich yttria stabilised hafnia deposited on the top surface. All the configurations showed an excellent resistance with limited degradation signs.

Fabrication of Functionally Graded Materials through Severe Plastic Deformation of Powders: Process, Significance, and Future Development

Functionally graded materials (FGMs) are a remarkable invention in materials science and engineering, that offers unique properties useful in various applications. Having the ability to gradually change properties, like composition, microstructure, or mechanical properties of materials, gives FGMs unparalleled adaptability, making them suited for a wide range of high-strength applications. One of the novel methods of creating FGMs is to use severe plastic deformation (SPD) techniques on powdered materials. The SPD of powders involves a few critical steps; The process begins with selecting materials with varied compositions and phases then mixing the powders, cold compaction, SPD methods, and, if necessary, heat treatment. The process is completed with characterization and testing, to evaluate the microstructure and characteristics of the final FGM formed. FGMs will continue transforming materials engineering and pushing the boundaries of their applications in many engineering fields and industries since they exhibit attractive capabilities like improved efficiency, durability, and performance. Therefore, this article explores the process of fabricating FGMs by SPD and emphasizes its significance and future trends in FGM production.

Numerical analysis of an experimental ballistic test of Al/SiC functionally graded materials

Metal/ceramic functionally graded materials (FGMs) have been increasingly used for impact-resistant applications because of their ability to combine the strength of both components. However, understanding the local response of FGMs under ballistic impact conditions remains a complex nonlinear problem. Moreover, performing experimental investigations is difficult due to technical limitations in measuring critical parameters such as stress, strain, and pressure. That is why research in this field also concentrates on modeling methodologies, such as numerical simulations. In this study, a finite element model (FEM) was implemented to investigate the behavior of a particular metal/ceramic-based FGM impacted with fragment-simulating projectiles (FSPs). The studied FGMs, exhibiting an elastoplastic behavior, were composed of aluminum (Al) and silicon carbide (SiC). The ceramic volume fraction (Vc) varies according to a power-law distribution, through the thickness. Their effective material properties were evaluated using a homogeneization-based self-consistent method. FGM’s dynamic behavior was described using the dynamic Tamura-Tomota-Ozawa model (DTTO). The numerical simulations were in good correlation with experimental results. The importance of the DTTO model's introduction and the calibration of the plastic strain criterion in the failure modeling of FGMs were highlighted. In addition, it was observed that the variation in the composition exponent and grading continuity of mechanical properties has a significant effect on the predicted ballistic limit. It was finally noted that a linearly-composed 5-layerbased specimen exhibited a higher level of ballistic resistance.

Static Convergence Behaviour of Discrete Kirchhoff-Mindlin Triangular Element on Rectangular Functionally Graded Material Plates

Rapid infrastructure development is consistent with the increase in innovation in structural elements. One of the main parameters in infrastructure development is materials. An advanced composite material called Functionally Graded Material (FGM) has been widely used. FGM is composed of the combination of two or more materials. FGM increases the bond strength between the layers compared to conventional composite materials, eliminating stress at the interface layers, and reducing cracks. However, further studies are required to understand the behaviour of the FGM plate. Finite element analysis (FEA) was considered to evaluate the convergence behaviour of the FGM plates. The Discrete Kirchhoff-Mindlin Triangular (DKMT) element is employed in the analysis. Studies regarding the FGM plates with the DKMT element were limited to square shapes and skew shapes. Thus, this study aims to study the convergence behaviour of the rectangular FGM plates composed of ceramic and metal. The FEA was carried out in different types of meshing, ratio a/h, ratio a/b, the power-law index, and boundary conditions. The analysis results indicate that the application of the DKMT element in analyzing the FGM plates gives good asymptotic and convergence behaviour. Thus, this method has proved reliable and sustainable.

Influence of laser power on mechanical properties of FGM of SS316L and IN625 fabricated by direct metal deposition

Direct Metal Deposition (DMD) is a metal Additive Manufacturing (AM) process. It is used for producing sustainability Functionally Graded Materials (FGM) and repairing of sophisticated parts. In this present research, a commercially available DMD machine deposited three partial FGM blocks of size 26 mm wide × 34 mm thick × 32 mm heights. The commonly influence parameters on Ultimate Tensile Strength (UTS) are scan velocity and laser power. The powders used for deposition were Stainless Steel 316L (SS316L), Inconel 625 (IN625), and their three different compositions. ASTM E8 tensile samples were cut from those blocks by wire cut-EDM. Micro-tensile tests were carried out on ASTM E8 samples using a SHIMADZU micro-tensile machine. The results revealed that partial FGM sample-2 had high sustainability UTS of 532 MPa as compared to remaining two samples. It is illustrated that for joining two dissimilar materials to obtain high UTS thick layered (i.e., thickness more than 1 mm) gradient path method should be selected at the medium laser power available on the DMD machine. However, the sample-3 has higher hardness at high laser power.

Evaluation of mechanical properties of Ni/BaTiO3 functionally graded material

A Ni-BaTiO3 functionally graded material (FGM) was elaborated from 5 separate layers, ranging from 0 to 100 wt.% Ni content, by Spark Plasma Sintering (SPS) method. To estimate the variation of mechanical properties in the FGM thickness, 5 homogenous mixtures (100% BaTiO3, 75% BaTiO3-25% Ni, 50% BaTiO3 - 50% Ni, 25% BaTiO3-75% Ni and 100% Ni) were sintered. The density, the Vickers hardness, the Young's modulus and Poisson ratio were measured. In order to observe the impact of polarization on their properties (in future work), non-destructive tests are performed in this study. Results from monolithic pellet are gathered to identify the power law that governs the variation of this property in the FGM thickness. The results show that each property has its own power law.

Static Behavioral Studies of a 2D Taper Beam using Finite Elements Comprised of Functionally Graded Materials

The study examines the thermal and structural properties of beams made of functionally graded materials (FGMs) using the Finite Element Analysis (FEA) method and Reddy’s beam theory. The distribution of material qualities in thickness and length directions is influenced by mechanical and thermal loads. We calculate the stress and deflection of FG beams with a uniform load distribution. Quantitative results demonstrating the effects of multiple factors are provided by the Fusion 360 software. These include the change from alumina (ceramic) to aluminum (metal), boundary conditions, volume fraction distribution, and geometric features.

A meshfree TSDT-based approach for modeling a skew plate

Taking into account new frontiers in materials technology to improve construction materials, we investigate the bending analysis of a Functionally Graded Material (FGM) skew plate using a meshless approach based on Third-order Shear Deformation Theory (TSDT). We assume that the material distribution is functionally graded across the thickness of the skew plate. The proposed approach uses both mixture rule theory and the meshless method. The mixture rule theory is used to estimate the effective material properties of the skew plate.

Experimental Investigation and Fuzzy Logic Modelling of Mechanical Characteristics in Aluminium Die Cast-14 Incorporating Functionally Graded Material (FGM) with Boron Carbide (B4C)

Experimental Investigation and Fuzzy Logic Modelling of Mechanical Characteristics in Aluminium Die Cast-14 Incorporating Functionally Graded Material (FGM) with Boron Carbide (B4C)

Napredak i budući trendovi aditivne proizvodnje žicom i električnim lukom (WAAM)

Over the past three decades, extensive research has been conducted on WAAM (Wire and Arc Additive Manufacturing), a production technology that traces its origins back almost a century with its initial patent. This technology has garnered increasing attention due to its capability to fabricate large near-net-shape metal products. The utilization of existing welding equipment for the heat source and material feedstock in WAAM offers the advantage of lower initial investment costs. Originally gaining prominence in the aerospace industry, it primarily focused on the utilization of lightweight metal alloys. However, recent advancements have broadened the scope of WAAM to encompass numerous products, including functionally graded materials (FGMs) and the combination of diverse alloys. This study seeks to unveil the latest breakthroughs and potential avenues in WAAM technology, offering valuable insights and recommendations for future research endeavors.

Analiza elastično-plastičnog naprezanja skupljajućih debelih FGM cilindara

This paper addresses the stress analysis of shrink-fitted thick-walled cylinders made of functionally graded material (FGM). Analytical solutions are provided for the elastic-plastic behavior of shrink-fitted axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory and plasticity laws. Due to the material's functional gradation, mechanical characteristics like Young's modulus, yield stress, and plastic parameters are controlled by a power function along the wall thickness. Considering a plane strain case, elastic-perfectly plastic model and Von Mises yield criterion; theoretical solutions are obtained for both elastic and plastic phases. The radial, hoop, axial, and equivalent Von Mises stresses are obtained for up to 25%, 50%, and 75% of cylinder plasticization for the elastic and plastic zones. Stresses are given in terms of interference and geometrical and mechanical parameters of the assembly. In addition, the interferences to start plastic deformation and the full plastic collapse of the cylinder are discussed. Moreover, the effect of the gradient index on the contact pressure and both the start of yield and plastic collapse pressures are conducted. The analytical results found in the current research are compared with the numerical solutions carried out by Ansys Workbench. Both results show a good agreement.

Analytical solutions for the thermo-mechanical bending of FG beams using a higher order shear deformation theory (HSDT)

The aim of this paper is to analyze a thermo-mechanical behavior of functionally graded beam in thermal environment. Therefore, this research work investigates a thermal, mechanical and thermo-mechanical bending of functionally graded beam resting on simple supports and using a higher order shear deformation theory. the proposed kinematic uses only three variables, which is even less than the first order shear deformation theory (FSDT) and the conventional higher order shear deformation theories (HSDTs). The present model adopts a new displacement field, The material properties of the FG beam are varied along the thickness direction according to the power law distribution (P-FGM). The governing equations for the thermo-mechanical bending investigation are obtained through the principal of virtual work and solved via Navier-type solution method was used to obtain results. All the results are presented in non-dimensional form and validated it by developing the classical beam theory (CBT), and other higher order theories. Parametric studies are thus elaborated to see the influence of the characteristic’s geometries and mechanical in particular: thickness of the FG beam, material index and ratio (width, length).