ANSYS APDL Research Articles

Creep-damage modelling for micro gas turbine combustion chambers lifetime prediction

Micro Gas Turbines (MGTs) are nowadays largely used for electrical and thermal energy production in small buildings and households. Their reliability and compactness allow them to operate for thousands of hours with minimal maintenance. However, the long exposure at high temperatures in combustion chambers can promote creep, which can induce thermal fatigue and potential failure of these components. Creep-induced damage in MGTs has not yet been thoroughly investigated, due to the lack of numerical tools able to model these strongly coupled phenomena. This study presents the development of a Fortran-based subroutine integrated into ANSYS APDL. The code allows for a life assessment based on the Lemaitre-Chaboche creep damage model. Secondary creep and stress relaxation are modeled for the high-temperature resistant alloy Inconel718. A new set of temperature-dependent parameters for the Norton equation is provided, and the method to obtain these parameters from creep rupture tests is outlined. The model is validated and shows good agreement with experimental data. The subroutine correctly reproduces visco-plasticity, stress relaxation and damage under typical MGTs operating temperatures. This model constitutes the foundation of a life-assessment analysis for combustion chambers. The results highlight the impact of temperature and creep on the component’s life and the importance of integrating life assessment analysis into the preliminary design of combustion chambers.

Experimental and finite element analyses on the vibration behavior of 3D-printed PET-G tapered beams with fused filament fabrication

PurposeThis study aims to reveal the influences of three-dimensional (3D) printing parameters such as layer heights (0.1 mm, 0.2 mm and 0.4 mm), infill rates (40, 70 and 100%) and geometrical property as tapered angle (0, 0.25 and 0.50) on vibrational behavior of 3D-printed polyethylene terephthalate glycol (PET-G) tapered beams with fused filament fabrication (FFF) method.Design/methodology/approachIn this performance, all test specimens were modeled in AutoCAD 2020 software and then 3D-printed by FFF. The effects of printing parameters on the natural frequencies of 3D-printed PET-G beams with different tapered angles were also analyzed experimentally, and numerically (finite element analysis) via Ansys APDL 16 program. In addition to vibrational properties, tensile strength, elasticity modulus, hardness, and surface roughness of the 3D-printed PET-G parts were examined.FindingsIt can be stated that average surface roughness values ranged between 1.63 and 6.91 µm. In addition, the highest and lowest hardness values were found as 68.6 and 58.4 Shore D. Tensile strength and elasticity modulus increased with the increase of infill rate and decrease of the layer height. In conclusion, natural frequency of the 3D-printed PET-G beams went up with higher infill rate values though no critical change was observed for layer height and a change in tapered angle fluctuated the natural frequency values significantly.Research limitations/implicationsThe influence of printing parameters on the vibrational properties of 3D-printed PET-G beams with different tapered angles was carried out and the determination of these effects is quite important. On the other hand, with the addition of glass or carbon fiber reinforcements to the PET-G filaments, the material and vibrational properties of the parts can be examined in future works.Practical implicationsAs a result of this study, it was shown that natural frequencies of the 3D-printed tapered beams from PET-G material can be predicted via finite element analysis after obtaining material data with the help of mechanical/physical tests. In addition, the outcome of this study can be used as a reference during the design of parts that are subjected to vibration such as turbine blades, drone arms, propellers, orthopedic implants, scaffolds and gears.Social implicationsIt is believed that determination of the effect of the most used 3D printing parameters (layer height and infill rate) and geometrical property of tapered angle on natural frequencies of the 3D-printed parts will be very useful for researchers and engineers; especially when the importance of resonance is known well.Originality/valueWhen the literature efforts are scanned in depth, it can be seen that there are many studies about mechanical or wear properties of the 3D-printed parts. However, this is the first study which focuses on the influences of the both 3D printing parameters and tapered angles on the vibrational behaviors of the tapered PET-G beams produced with material extrusion based FFF method. In addition, obtained experimental results were also supported with the performed finite element analysis.

Case study of shear strengthening of RC Corbels by steel plates using fea

The study aimed to explore the possibility of strengthening RC corbels with many strengthening techniques. The research analyzed the RC corbels behavior under a wide range of variables. The theoretical study consisted of twelve models reinforced with GFRP bars with strengthening by steel plate. Finite element analysis with ANSYS APDL was used to verify five specimens. This research deals with a static nonlinear FE simulation to investigate the behavior of RC Corbels reinforced internally and externally. The verification with experimental work demonstrated a satisfactory agreement in the load-displacement relationship, ultimate load and displacement, and failure mode. The parametric study was implemented which included strengthening the four concrete corbels externally and four corbels internally by a steel plate in many configurations while the remaining three were modeled with varied compressive strength (30, 40, and 50) MPa. The external strengthening included the placing of steel plate externally around the corbel in a U-shaped form and partial strengthening by strips and bottom plate. The models with internal strengthening involved placing the steel plate internally instead of stirrups. The results discovered that the strengthening provided enrichments in the stiffness, ductility, and energy absorption by 37 %, 4 %, and 26 %. In addition, in the case of full external strengthening more than internal retrofitting, there is a maximum improvement in the cracking and ultimate load carrying capacity. The external strengthening was better than internal one due to the confinement effect of the concrete. The stress distribution and crack pattern were affected by the strengthening techniques and more cracks appeared in the corbels with external steel plates.

Nanoresonator vibrational behaviour analysis of single- and double-layer graphene with atomic vacancy and pinhole defects

Nanosensors and actuators are frequently made of graphene. Any defect in the graphene's manufacturing has an impact on its sensing performance and on its dynamic behaviour. Using a molecular dynamics technique, the influence of pinhole defects and atomic defects on the performance parameters of single-layer graphene sheets (SLGSs) and double-layer graphene sheets (DLGSs) with various boundary conditions and lengths is explored. In contrast to the perfect nanostructure of a graphene sheet, defects are described as holes formed by atomic vacancies. As the number of defects increases, the simulation results show that the presence of defects has the greatest impact on the resonance frequency of SLGSs and DLGSs. The influence of pinhole defect (PD) and atomic vacancy defect (AVD) on armchair, zigzag, and chiral SLGSs and DLGSs was investigated in this article using molecular dynamics simulation. The influence of both types of defects is largest when it is adjacent to the fixed support for all three different types of graphene sheets, i.e. armchair, zigzag, and chiral. The structure of the graphene sheet has been created using ANSYS APDL software. In the structure of the graphene sheet, atomic and pinhole defects have been generated. SLG and DLG sheets are modelled using a space frame structure that is identical to a three-dimensional beam. Dynamic analysis of single-layer and double-layer graphene sheets performed with different lengths using the atomistic finite element method. The interlayer separation in the form of Van der Waals interaction is modelled using characteristic spring element (Combin14). The upper and lower sheets of DLGSs are described as elastic beams connected by a spring element. With atomic vacancy defect for the bridged boundary condition, the highest frequency of 2.86 × 108 Hz was found for zigzag DLG (20 0) and with same boundary condition for pinhole defect 2.79 × 108 Hz frequency achieved. In a single-layer graphene sheet with an atomic vacancy and cantilever boundary condition, the maximum efficiency was 4.13 × 103 Hz for SLG (20 0), while in a pinhole defect, it produced 2.73 × 107 Hz. Moreover, the elastic parameters of beam components are calculated using the mechanical properties of covalent bonds between carbon atoms in the hexagonal lattice. The model has been tested against previous research. The focus of this research is to develop a mechanism for determining how defects affect graphene frequency band in application as nano resonators.

Optimization of Pile Driver Frame Based on Sensitivity Analysis

The optimization of the pile driver frame is very important to the overall performance of the pile driver. This paper examines the large body structure of a model of a hydraulic static pile driver as the research object. ANSYS APDL finite element software is used to perform static analysis and sensitivity analysis on the large body structure of the pile driver. On the premise of meeting the design requirements, according to the most dangerous working conditions of the pile driver, the size optimization of the frame structure of the pile driver is carried out based on sensitivity analysis. The mathematical model is established with the plate thickness as the design variable, the strength and stiffness of the body structure as the constraints, and the minimum mass of the body structure as the objective function. The optimization results show that the optimization design model based on sensitivity analysis not only meets the strength and stiffness conditions of the large structure, but also reduces the structural mass by 22.1% and greatly reduces the production cost.

Numerical and experimental methodologies to investigate the damage progression inside the axisymmetric composite cylinders with cutouts under torsion

Torsional performance and damage progression inside the long and hollow axisymmetric composite cylinders with different cutouts sizes are investigated via experimental and numerical methods. Acoustic emission, Digital image correlation, and Infrared thermography are deployed to investigate failure propagation. Four acoustic sensors adhere to different locations, and the frequency-based analysis is performed for the damage classification. The cumulative energy data of each sensor is correlated with the nearby strain gauge data to identify the cause of failure. Among all the classified failure types, the predominant failure is matrix cracking which is caused by shear stresses. The percentage of each failure type varies at different locations of the cylinder, and global failure is caused by the simultaneous occurrence of these failure events. Thermography analysis measures the temperature change due to the failure and provides the imprints of the failure initiated by certain damage activities. The thermograms reveal the damage propagation around the cutout and post-global failure postmortem. A material degradation-based progressive damage analysis is performed through Ansys APDL using Hashin failure criteria. The reliability of the performed study is exhibited by comparing the full-field displacement maps and torque-rotation curves of the experimental and numerical analysis.

TÍNH TOÁN THIẾT KẾ VÀ TỐI ƯU HÓA KẾT CẤU KHUNG MÁY IN 3D BÊ TÔNG KÍCH THƯỚC LỚN DẠNG CỔNG TRỤC

This article presents the structural analysis and design optimization of the frame of a large-scale 3D concrete printer for construction. A finite element model of the frame of the 3D printer with various operating conditions was established using NX Nastran and Ansys APDL software. The script code for automated calculation of the deflection and natural frequency of the structure was built in the integrated Matlab-Ansys APDL language. The influence of different design parameters on the behavior of the structure is clearly evaluated with the aid of script code. Then, the optimal mathematical model of the X and Z axis structure is built with the criteria of the minimum mass, four constraints, and six variables as design parameters. The problem is solved by the genetic algorithm. Based on the optimal set of parameters and the standard box steel size table, a reasonable design option was selected, with the mass reduced by 70.6 % compared to the design option based on early experience.

Use of MAXFEA-ANSYS tool to study the Electro-Magnetic behaviour of the new ST40 inner vacuum chamber proposal during a plasma VDE

Tokamak Energy Ltd. is developing compact fusion power plants based on two promising technologies, Spherical Tokamaks (STs) and High Temperature Superconductors (HTS), with the aim to build a first demonstrative plant by the 2030′s. On its path to fusion power, Tokamak Energy is presently operating ST40, a new generation ST that is currently the highest field device of its kind. In the near future, an important ST40 upgrade is planned and foresees the manufacturing and the installation of a new vacuum chamber, called IVC2. This upgrade will allow the exploitation of ST40 to its maximum performances enabling Double Null (DN) diverted operations with up to 2 MA of plasma current and 3 T of toroidal field. IVC2 is currently in the final design stage. The necessity to analyse in detail the Electro-Magnetic (EM) behaviour of this component under the loads coming from plasma disruptions has recently emerged in order to verify the design or drive further modifications. In this context, a study to analyse the EM response of IVC2 during a plasma Vertical Displacement Event (VDE) has been carried out using the MAXFEA code in combination with ANSYS APDL, following a recent workflow development. The main output of this study is the evaluation of the transient EM force density in IVC2 and other components for subsequent mechanical assessments. The aim of this paper is to present the results of this analysis to show the successful application of this procedure in the context of ST40 project.

Free vibration analysis of curved asymmetric sandwich structures

This study deals with free vibration analysis of asymmetric sandwich structures that have different curvature angles. Polyvinyl chloride (PVC) foam, carbon fiber, and glass fiber were used as the core and surface sheets of the sandwich structures, respectively. The finite element method is used for the study. Commercially available software ANSYS apdl is employed to investigate the vibration study of curved asymmetric sandwich structures. Firstly, the accuracy of the finite element method is determined by making a comparison with the literature. Following that, the first six natural frequencies of sandwich structures were obtained for various sandwich configurations to examine the effects of asymmetry and curvature angle on the sandwich structures' characteristics. To achieve that two different configurations of sandwich structures are modeled. Each configuration has 5 different sandwich structures whose curvature angles are 0,15,30,45 and 60 degrees. All of the sandwich structures were modeled and solved using ANSYS apdl. Results show the impact of asymmetry and curvature angles on sandwich structure free vibration behavior. Also, it was obtained that free vibration analysis of curved sandwich structure can be performed by the proposed method accurately, which is hard to obtain by the analytical method and expensive by the experimental method. Using this method one can investigate different scenarios in a short time. Also, one can use this method before production to see if it is good for application.

Microstructure evolution and underlying thermal behavior of high-content TiC reinforced titanium matrix composites fabricated by laser directed energy deposition

Titanium matrix composites (TMCs) with high-content TiC have a wide prospect in the aerospace industry due to their high strength, hardness, and wear resistance. The comprehensive properties of TMCs are mainly determined by the morphology and distribution of TiC reinforcements. Hence, the effects of laser directed energy deposition (LDED) process parameters on the TiC morphology and the properties of TMCs were discussed in detail by simulations and experiments in this study. A finite element model was established by ANSYS APDL to explain the complicated phenomena during LDED of high-content TiC (60 wt%) reinforced Ti6Al4V composites. The effects of process parameters on the temperature field and grain solidification behavior were studied. As the scan speed increased, the maximum temperature gradient (G)·solidification rate (R) value increased from 6.2 × 103 to 1.4 × 104 °C/s, which caused the size of TiC to decrease gradually. The maximum G/R value decreased from 1285.5 to 491.9 °C·s/mm2, resulting in the morphology of TiC changing from dendritic to granular grains. 60 wt% TiC/Ti6Al4V composites free of pores and cracks were successfully fabricated by LDED. It was found that the TMCs were nearly dense (99.48%) with uniform dispersed TiC. Irregular-shape TiC particles were melted and then precipitated in the form of submicron lamellar and granular phases, which was consistent with simulations. At the optimized parameter, TMCs with an average hardness of 549.0 HV0.5 were obtained, and the wear resistance of this sample was improved by 53% compared to LDED-processed Ti6Al4V.

MWCNTs polymer nanocomposite with enhanced thermomechanical properties and electrical insulation for effective encapsulation

This study presents the effect of the variation in weight fraction of multiwall carbon nanotubes (MWCNTs) in polymer with the objective of enhancing the thermo-mechanical properties along with the electrical insulating properties. Polymer multi-walled nanocomposites (PMWCNC) and MWCNTs/Al2O3 bi-layer nanocomposites were prepared by solution mixing method with ultrasonication and magnetic stirring, then molded in vertical sandwich molds, made of acrylic and aluminum sheet as per ASTM standards. The tensile strength of PMWCNC was enhanced by 32%, 23%, 15%, and 5% compared to unmodified epoxy with the incorporation of 1 wt%, 0.75 wt%, 0.5 wt%, and 0.25 wt% of MWCNTs. The dispersion morphology of MWCNTs in epoxy was observed with field emission-scanning electron microscope (FE-SEM). The thermogravimetric analyzer (TGA) investigation found that increasing the weight percentage of MWCNTs resulted in improved thermal stability. The enhanced electrical conductivity of PMWCNC caused by the addition of MWCNTs was countered through the deposition of a thin film layer of alumina-filled polymer nanocomposite on the top surface of PMWCNC to retain the electrical insulation properties. The representative volume element (RVE) technique was employed to predict the effective modulus of nanocomposite based on the various constituent properties, weight fractions and interfacial behavior between MWCNTs and epoxy with the help of finite element analysis. Additionally, Modified Mori-Tanaka (MMT) micromechanics scheme was used to find the effective elastic modulus of the nanocomposite with the help of the MATLAB code. The elastoplastic behavior of polymer nanocomposites was also simulated in ANSYS APDL through the Voce model. The enhanced thermomechanical properties while retaining the electrical insulation properties suggest that the MWCNTs-based polymer would make the electronic chip more reliable.

Modeling and analysis of tapered composite beams with piezoelectric energy harvester: Numerical and experimental investigations

In the present study, a numerical and experimental investigation is carried out on vibration-based energy harvesting from unimorph cantilever tapered composite beams. A uniform and various configurations of a tapered composite structure embedded with piezoelectric material are considered to identify the electrical energy generated by the piezoelectric material when dynamic energy is imparted on the structure. Lead zirconate titanate (PZT) of 5-H grade piezoelectric material is considered to be embedded on a cantilever beam made of glass fiber reinforced polymer matrix composite. The numerical modeling and analysis are performed on the composite structure embedded with PZT to calculate the total amount of electrical energy that can be generated by the PZT material using commercially available ANSYS APDL software. Various parametric studies are also carried out to investigate the effects of varying the location of the PZT patch and the configuration of the PZT patches on the electrical energy developed by the PZT. Further, the power generated through unimorph composite structure with PZT material connected in series and parallel are explored.

Application of simulation methods on vibration analysis of a bus driver seat using the quarter car 3DOF model subjected under harmonic excitation

Vibration of bus driver's seat subjected under harmonic excitation, 3DOF (3 degrees of freedom) dynamic model is employed to carry out the calculation by 3 simulation methods. Mathematical model - numerical using Matlab programming language (Numerical model), Multi Body Dynamics (MBD) using Matlab Simmechanics tool (MBD model) and finite element model using Ansys APDL (FEM model) are employed. The strengths and limitations of each method are analyzed through the process of building models and retrieving the resulting data. The evaluation indexes include the response of driver's seat acceleration, response of the seat suspension's relative displacement and the seat suspension's vibration isolation ability according to two investigated cases of natural frequency and damping ratio. The obtained results from all 3 methods have no difference and the evaluation indexes are suitable according to the studies on vehicle vibration response. The Numerical model method requires the user to perform complex mathematical modeling. The MBD model method using Matlab Simmechanics is simpler, using built-in function blocks, requiring declarations to establish the exact initial equilibrium position of the mass elements. The FEM model method using Ansys APDL with keypoints and lines describing the model elements requires precise setting of the displacement of each keypoint. However, both the MBD and FEM model methods are only effective when investigating the response in the time domain for a particular instance of the excitation frequency. When analyzing the response in the frequency domain, which requires accessing and synthesizing data of many cases in the investigated frequency range, these two methods have many limitations in the calculation process, specifically, in performing complex computations with many loops and variables. Solving problems also takes longer than numerical method using mathematical model. The obtained results are analyzed in the time domain, frequency domain, and the value domain of the driver's seat suspension parameters. This result serves as a basis for developing the design of the driver's seat suspension system with nonlinear spring and shock absorber, and the selection of a calculation method suitable for each problem in the field of vehicle vibration.

Effect of design parameters on the ultimate strength and collapse behaviour of stiffened panels

Research about stiffened panel applications in ships has massively progressed with the amount of several methods to analyze it. Various studies had been conducted on stiffened panels using Finite Element Method (FEM). However, none have thoroughly explored the most optimal and efficient analysis methods and settings. Given the growing importance o f FEM in reliability analysis for ship structures, particularly stiffened panels, a comprehensive study comparing different approaches is o f paramount significance. Such research would not only streamline timeconsuming procedures but also offer invaluable recommendations to advance the field's understanding and practical applications. In this paper, a finite element analysis study was done to analyze the influence o f several parameter modeling o f stiffened panels not only to achieve the models' ultimate strength value and collapse behavior but also to offer practical recommendations on the most optimal and efficient methods for analyzing stiffened panels through FEM. Conducting modification o f three variations o f the model configuration, four variations o f boundary condition, and four variations o f transverse stiffener modeling to compare each other. Running time consumed when simulations are calculated in ANSYS APDL was also being considered. The results showed a significant difference in modifying the model configuration's case, while in contrast, the modification o f boundary conditions and transverse stiffener modeling only showed a slight difference in ultimate strength value. In addition, modification o f transverse stiffener geometry only gave the difference by around 0.5 MPa. The model configuration case (A1 v A2) showed the most remarkable running time difference, which reached six times difference.

Numerical analysis of axial compressed multifaceted concrete-filled tube elements

The object of study is multifaceted steel concrete- filled poles. The subject of research is the bearing capacity and parameters of the stress-strain state of multifaceted steel concrete- filled poles. The purpose of the research is to numerically study the features of the operation of multifaceted concrete-filled structures under axial compression. Are discussed the features of creating a computational finite element model of such structures in ANSYS APDL. Analytical methods are described for determining the parameters of the nonlinearity of the materials used, as well as the physical and mechanical characteristics of concrete operating under compression conditions. On specific examples the change in the bearing capacity for the object of study under various conditions of materials adhesion (friction coefficient μ varied within 0.1...0.6 with step 0.1). Is analyzed the "unified" analytical method for determining the bearing capacity of steel multifaceted concrete-filled structures, indicating the degree of variability of ultimate compressive load depending on the variation in the number of faces and thickness of the metal wall of the multifaceted model. The considered features of creating a computational model in the ANSYS APDL finite element analysis system, using various laws of deformation of steel and concrete, made it possible to determine the qualitative and quantitative levels of variability of their bearing capacity, which in combination will allow designers of such structures to reach a qualitatively new level when creating structures based on pipe concrete elements.

2D and 3D numerical investigation on contact stress behaviour on different combinations of gear pair

Polyamide (PA6) polymer gear tremendously expanded its usage in power transmission applications. PA6 gear were engaged with different combinations of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) were utilized in those applications. Normally gears are subjected to Hertzian contact stress due to their non-conformal contact and ANSYS is one of the widely used Finite Element Analysis (FEA) tool to determine the contact stress behaviour of those gears. Even though numerous 2D and 3D FEA investigation were performed to determine the gear contact stress behaviour, the occurrence of surface and subsurface stresses for different combination of gear pair was not explored especially for PA6 gears. Thus, the work attempted to study the surface and subsurface contact stress behaviour of three combination of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) using 2D (plane stress with thickness condition) and 3D FE analysis (ANSYS APDL). The optimum mesh sizes were selected from the convergence study and further simulations were performed. From the analysis, the stress was observed maximum at the contact pitch point for 2D analysis, whereas, 3D analysis showed the maximum stress at a depth below the contact surface (subsurface stress) for all the combinations of gear pairs. Different trend pattern was obtained between the stress plot of 2D (surface stress) and 3D (subsurface stress) analysis for all the gear pairs. The variation in depth occurrence of maximum stress was observed for Steel-PA6 (0.16 mm depth), PA6-Steel (0.16 mm depth) and PA6-PA6 (0.25 mm depth) gear pairs. And, the Polymer – Polymer (PA6-PA6) gear pair exhibited higher depth occurrence compared to Steel – PA6 and PA6 – Steel gear pairs.

Crack detection in reinforced concrete beams under loading using deformed shape curvature method

Structural health monitoring (SHM) helps to detect anomalies on the structure early, thereby creating favorable conditions for repairing or replacing damaged components in a timely manner, estimating the remaining life of the building, and limiting any potential consequences to a minimum. Nowadays, science and technology in the field of civil engineering have advanced significantly. The development of effective and reliable methods for damage detection has been a remarkable research topic for many years. This study presents a method of detecting the position and width of crack zones for reinforced concrete (RC) beams using the curvature of the deformed shape as input data. A 4-point bending test of an RC beam is simulated using ANSYS APDL software. The simulation results are verified by comparing with experimental results to verify the numerical simulation's reliability. The change in the deformed shape curvature in the RC beam is analyzed with different loading levels. Then, a set of damage identification indices based on the difference in the deformed shape curvature is proposed to evaluate the method’s accuracy. The results show that the deformed shape curvature method has high accuracy in identifying the location and the width of the crack zones in the RC beam under loading.

Compressive stiffness of L-stubs in contact with rigid and flexible foundations

The rotational stiffness of bolted connections is influenced by the stiffness of T-stubs loaded in tension. Except for column base plate, the stiffness of T-stubs loaded in compression is assumed infinite and the centre of compression is fixed at the centre of the beam flange. Nevertheless, this assumption leads to inconsistent conclusions for bolted circular flange connections, double web angle connections… The relative stiffness of the tensile and compressive areas should be considered. Simple expressions of the compressive stiffness of L-stubs and T-stubs have been derived recently based on refined beam model in contact with a rigid foundation. However, the end-plate can be in contact with a flexible foundation. In the present paper simple analytical expressions are proposed to calculate the compressive stiffness of L-stubs in contact with rigid or flexible foundations. For this purpose, a refined beam model resting on Winkler foundation is firstly derived. Then, this model is used to analyse L-stubs in contact with flexible or rigid supports. Simplifications are proposed for the contact pressure distribution and also the compressive stiffness. The analytical propositions are compared against finite element calculations performed with ANSYS APDL.

Maximum Quasi-Static Indentation Stress Analysis of Flax/Epoxy and Glass/Epoxy Polymer Composites

The use of fibres is constantly expanding to satisfy the demands of various industries.Both synthetic and natural fibresoffer benefits that are best suited tospecific applications. Synthetic fibresare preferablethan the natural fibresbecause they have greater mechanical properties. However, in their application, synthetic fibresnegatively influencethe environment as they are non-biodegradablematerial. Asa result, the demand and usage of natural fibreskeep increasing as an alternativeto the synthetic fibres. The usage of natural fibres reducesnegative impact on the environmental, though their properties are not as good as synthetic fibres. ANSYS APDL, one of the FEA analysis software, is used to perform quasi-static indentation (QSI)testmodellingin this research work. The purpose of this study is to determine the influence of fibreorientations of 0°, 15°, 30°, 45°, 60°, 75°, and 90°, as well as the effect of the supporting ply angle, 0°, on the mechanical properties of Flax FRP composite. For layup sequences of [(+θ, -θ)2]Sand [(±θ)2,04]S, it was observed that maximum strength increases from 0° to 90° fibreorientation. Meanwhile, in a QSI test, the highest strength of Flax FRP was found at 45° for both [(+θ, -θ)2]Sand [(±θ)2,04]Slayup sequences, with 94.20 MPa and 96.80 MPa,respectively. The effect of fibrevolume fraction(Vf), such as Glass FRP composites with fibrevolume fractions of 30% and 60%,shows that the fibrevolume fraction for 60% has a better performance than 30%. Therefore, composites with a higher fibrevolume fraction show better maximum strength and lower deformability. The results of modellingand simulation work on Flax FRP composites can aid in developingnew materials that are more sustainable than conventional techniques by anticipating the mechanical behaviourof natural FRP composites.

Optimal design of geometrically nonlinear structures using topology optimization

This study deals with comparing the stiffness design of geometrically nonlinear structures and linear structures using topology optimization. Bi-directional Evolutionary Structures Optimization (BESO) is used for the design process. The geometrically nonlinear behavior of the structures is analyzed using a total Lagrangian finite element formulation and the equilibrium is achieved by Newton-Raphson iterative scheme. The topology optimization of linear and nonlinear modeling is performed. The sensitivity of the objective function is found with the adjoint method and the optimization problem is solved using BESO’s update method. Objective function of complementary work is evaluated. A special technique, the continuation method, is applied to eliminate the instability of nonlinear structure optimization. ANSYS APDL is also used to do FEA of optimal topology to verify the effectiveness of geometrically nonlinear modelling. The results show that differences in stiffness of structures optimized using linear and nonlinear modelling are generally small but it can be large in some cases, especially structure highly involving buckling behaviour.