Browsing by Author "Dayyani, Iman"

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    Comparison of GA and topology optimization of adherend for adhesively bonded metal composite joints
    (Elsevier, 2021-05-13) Arhore, Edore G.; Yasaee, Mehdi; Dayyani, Iman
    This paper investigates the effect of the outer adherend geometry on the strength of an adhesively bonded joint. The investigation was carried out by optimizing the joint geometry using two different numerical optimization methods. In genetic algorithm (GA) optimization with high fidelity explicit finite element analysis (FEA) and topology optimization (TOP). Both procedures were utilized on a simplified pseudo-2D model as well as a full-scale 3D model. The results showed that the outer adherend geometry directly affects the strength of a joint subjected to tensile load. For joints subjected to bending load, the geometry had little to no effect on the strength of the joint. The GA optimization process produced identical geometry for both 2D and 3D models. However, the TOP process produced different optimum geometries. The optimum joints produced by the TOP process offered the highest strength overall, while the optimum GA joint produced the best strength to weight ratio. The reasons for these results and other features of the optimized designs, including interface stress, failure mechanisms and computational efficiency are discussed in detail.
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    Computational analysis and design of an aerofoil with morphing tail for improved aerodynamic performance in transonic regime
    (Cambridge University Press, 2022-01-10) Rana, Zeeshan; Mauret, F.; Sanchez-Gil, J. M.; Zeng, Kai; Hou, Z.; Dayyani, Iman; Könözsy, László Z.
    This article focuses on the aerodynamic design of a morphing aerofoil at cruise conditions using computational fluid dynamics (CFD). The morphing aerofoil has been analysed at a Mach number of 0.8 and Reynolds number of 3×106 , which represents the transonic cruise speed of a commercial aircraft. In this research, the NACA0012 aerofoil has been identified as the baseline aerofoil where the analysis has been performed under steady conditions at a range of angles of attack between 0∘ and 3.86∘ . The performance of the baseline case has been compared to the morphing aerofoil for different morphing deflections ( wte/c=[0.005−0.1] ) and start of the morphing locations ( xs/c=[0.65−0.80] ). Further, the location of the shock wave on the upper surface has also been investigated due to concerns about the structural integrity of the morphing part of the aerofoil. Based upon this investigation, a most favourable morphed geometry has been presented that offers both, a significant increase in the lift-to-drag ratio against its un-morphed counterpart and has a shock location upstream of the start of the morphing part.
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    Crashworthiness and dimensional stability analysis of zero Poisson’s ratio fish cells lattice structures
    (Elsevier, 2023-11-03) Jha, Ashutosh; Cimolai, Guglielmo; Dayyani, Iman
    The present article introduces Zero Poisson's Ratio (ZPR) Fish Cells metamaterial and investigates the effects of Poisson's Ratio on the crashworthiness of Positive (PPR), Negative (NPR), and Zero Poisson's Ratio lattice structures. High-fidelity Finite Element models of the proposed sandwich structures are built, based on identical domains for unit cells. Impact performances of lattice structures are addressed for low (2 m/s) and high (5 m/s) impact velocities in three orthogonal directions. The parameters investigated for crashworthiness include impactor's penetration depth, von Mises stress distribution, edges deformation and dimensional stability. Numerical results demonstrate that, unlike PPR and NPR models, the Fish Cells ZPR model possesses greater lateral stability and structural integrity with minimal edge deformations in all three directions. This leads to reduced lateral impact transfer to adjacent components and localised damaged zones, increasing the life span of structural components while reducing maintenance and repair downtime. Experimental analyses are conducted on the Fish Cells metamaterial through a drop tower test for demonstrating agreement with simulations and validation of the proposed modelling approach.
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    Cylindrical helical cell metamaterial with large strain zero Poisson’s ratio for shape morphing analysis
    (IOP Publishing, 2023-09-22) Qin, Qing; Dayyani, Iman
    In this paper, a novel cylindrical metamaterial with helical cell exhibiting zero Poisson's ratio (ZPR) in two different directions is introduced. Detailed Computer-aided design modelling of a curved optimised spring element is demonstrated for numerical and experimental analysis. High fidelity finite element models are developed to assess the homogenisation study of Poisson's ratios, normalised Young's modulus and torsion behaviour, demonstrating the curvature effect and independency of mechanical behaviour of cylindrical optimised spring element metamaterial from tessellation numbers. Buckling and frequency analysis of the cylindrical metamaterial with spring element are compared with equivalent shell cylinders. Moreover, experimental analysis is performed to validate the large strain ZPR and deformation mechanism demonstrated in numerical simulations. Finally, radical shape morphing analysis under different bending conditions for cylindrical metamaterial with helical cell is investigated, including deformation and actuation energy and compared with positive and negative Poisson's ratio cylinders formed by honeycomb and auxetic cells.
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    Data: Modeling and performance evaluation of sustainable arresting gear energy recovery system for commercial aircraft
    (Cranfield University, 2023-08-07 11:48) Deja, Jakub; Skote, Martin; Dayyani, Iman
    Datasets showing the system performance for different aircraft
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    Effect of functionally-graded interphase on the elasto-plastic behavior of nylon-6/clay nanocomposites; a numerical study
    (Elsevier, 2020-03-08) Bazmara, Maziyar; Silani, Mohammad; Dayyani, Iman
    In nanocomposites, the interphase thickness may be comparable to the size of nano-particles, and hence, the effect of interphase layers on the mechanical properties of nanocomposites may be substantial. The interphase thickness to the nano-particle size ratio and properties variability across the interphase thickness are the most important affecting parameters on the overall behavior of nanocomposites. In this study, the effect of properties variability across the interphase thickness on the overall elastic and elasto-plastic properties of a polymeric clay nanocomposite (PCN) using a functionally graded (FG) interphase is investigated in detail. The results of the computational homogenization on the mesoscopic level show that Young's modulus variation of the interphase has a significant effect on the overall elastic response of nanocomposites in a higher clay weight ratio (Wt). Moreover, strength variation through the interphase has a notable effect on the elasto-plastic properties of PCNs. Also, the increase or decrease in stiffness of interphase from clay to matrix and vice versa have a similar effect in the overall behavior of nanocomposites.
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    Energy harvesting frictionless brakes for short-haul aircraft: thermal and electromagnetic feasibility of an axial-flux machine for a landing gear drive system
    (AIAA, 2023-06-08) Deja, Jakub; Akbari, Amir; Dayyani, Iman; Stote, Martin; Lowther, David
    The aviation industry is currently responding to climate change with, among other technologies, electrification of aircraft, and the corresponding onboard electrical architecture provides an opportunity for electromagnetic brakes. The present work introduces a multistage yokeless and segmented armature (YASA) electric machine that replaces friction brakes and harvests kinetic energy throughout a landing. The study establishes the optimal trade-off between weight and electromagnetic torque and translates it into the design requirements for the development of an electric machine. Electromagnetic modeling is conducted using a quasi-3D transient approach and static 3D validation. The results reach 120 Nm/kg active material torque density at approximately 50 A/mm² current density. The proposed solution enables fitting an electric machine that decelerates an aircraft at autobrake level LOW for Airbus and the "1" and "2" settings for Boeing. A thermal analysis follows, where a novel cruise altitude cooling method is proposed.
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    Fish Cells, a new zero Poisson’s ratio metamaterial - Part I: Design and experiment
    (SAGE, 2020-06-17) Zadeh, Mohammad Naghavi; Dayyani, Iman; Yasaee, Mehdi
    A novel cellular mechanical metamaterial called Fish Cells that exhibits zero Poisson’s ratio in both orthogonal in-plane directions is proposed. Homogenization study on the Fish Cells tessellation is conducted and substantially zero Poisson’s ratio behavior in a homogenized tessellation is shown by numerical analysis. Experimental investigations are performed to validate the zero Poisson’s ratio feature of the metamaterial and obtain force–displacement response of the metamaterial in elastic and plastic zone. A detailed discussion about the effect of the numerical model approach and joints on the structural response of the metamaterial is presented. Morphing skin is a potential application for Fish Cells metamaterial because of the integration benefits of zero Poisson’s ratio design. The structural integrity of the Fish Cells is investigated by studying the stiffness augmentation under tension and in presence of constraints on transverse edges. Finally, geometrical enhancements for improved integrity of the Fish Cells are presented that result in substantially zero stiffness augmentation required for morphing skins.
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    Fish Cells, a new zero Poisson’s ratio metamaterial - part II: Elastic properties
    (SAGE, 2020-07-27) Naghavi Zadeh, Mohammad; Dayyani, Iman; Yasaee, Mehdi
    Fish Cells as a new metamaterial with zero Poisson’s ratio in two planar directions is introduced with application in morphing aircraft skin. In order to tailor the design of this metamaterial for arbitrary loadings, equivalent elastic properties of the Fish Cells metamaterial are derived and analyzed using analytical and numerical methods. The admissible range of geometric parameters is presented and variation of elastic properties with parameters is studied. The effective elastic modulus of the metamaterial is derived analytically and verified with finite element models. The in-plane and transverse shear modulus of the metamaterial are evaluated using finite element analysis where accurate periodic boundary conditions for in-plane shear loading are investigated. The lower and upper bounds of the transverse shear modulus are derived based on strain and complementary energy relations which are verified with finite element results. As zero Poisson’s ratio behavior of the Fish Cells topology is proved, derivative geometries from this topology with zero Poisson’s ratio behavior are also presented.
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    Fuzzy finite element model updating of the DLR AIRMOD test structure
    (Elsevier, 2017-08-12) Haddad Khodaparast, H; Govers, Y; Dayyani, Iman; Adhikari, S; Link, M; Friswell, M; Mottershead, J; Sienz, J
    This article presents the application of finite-element fuzzy model updating to the DLR AIRMOD structure. The proposed approach is initially demonstrated on a simulated mass-spring system with three degrees of freedom. Considering the effect of the assembly process on variability measurements, modal tests were carried out for the repeatedly disassembled and reassembled DLR AIRMOD structure. The histograms of the measured data attributed to the uncertainty of the structural components in terms of mass and stiffness are utilised to obtain the membership functions of the chosen fuzzy outputs and to determine the updated membership functions of the uncertain input parameters represented by fuzzy variables. In this regard, a fuzzy parameter is introduced to represent a set of interval parameters through the membership function, and a meta model (kriging, in this work) is used to speed up the updating. The use of non-probabilistic models, i.e. interval and fuzzy models, for updating models with uncertainties is often more practical when the large quantities of test data that are necessary for probabilistic model updating are unavailable.
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    Graphic abstract
    (Cranfield University, 2022-06-07 12:41) Deja, Jakub; Dayyani, Iman; Skote, Martin
    Modelling and Performance Evaluation of Sustainable ArrestingGear Energy Recovery System for Commercial Aircraft
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    Identification of the key design inputs for the FEM-based preliminary sizing and mass estimation of a civil aircraft wing box structure
    (Elsevier, 2021-12-14) You, Chao; Yasaee, Mehdi; He, Shun; Yang, Daqing; Xu, Yigeng; Dayyani, Iman; Ghasemnejad, Hessam; Guo, Shijun; Webb, Phil; Jennings, James; Federico, Giovanni
    FEM-based preliminary structural sizing has been successfully carried out for a typical single-aisle wing box structure using MSC Nastran, by considering various load cases representing typical aircraft manoeuvres, engine loads, landing and ground handling conditions. The strength, buckling and fatigue criteria have been applied as the design constraints for sizing. The resultant total mass and the structural (static and modal) behaviour of the sized wing box model have been verified against a validated high-fidelity wing box model. A sensitivity analysis has been performed to evaluate the influence of the number of design fields and the selected design inputs (i.e. load cases and design constraints) on the accuracy of sizing and mass estimation of the wing box. This sensitivity analysis has also been extended to the static and modal behaviour of the wing box structure obtained from sizing. It provides an insight into the significance of considering the buckling and fatigue constraints, aircraft rolling loads, engine loads and landing loads in sizing, in addition to the commonly-applied 2.5 g aircraft pull-up loads under the strength constraint. The findings of this study highlight the trade-off between the sizing efficiency and accuracy of a civil aircraft wing for modelling purposes.
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    Large strain zero Poisson’s ratio spring cell metamaterial with critical defect analysis and variable stiffness distributions
    (Elsevier, 2013-05-12) Qin, Qing; Dayyani, Iman
    This paper presents novel metamaterial skins formed by 3D Spring Cells exhibiting zero Poisson’s ratio in two directions with no stress concentration on joints. Precise CAD models are generated to perform numerical and experiment analysis. High-fidelity Finite element models are developed to assess the homogenisation study of zero Poisson’s ratio. Moreover, the analytical method is also used to present for normalised Young’s modulus. Parametric study for the effect of parameter on normalised Young’s modulus and Poisson’s ratio is demonstrated based on analytical method. Pure shear analysis is demonstrated to show the off-axis loading behaviour. Structural defect analysis is investigated with regarding to its deformation mechanism under tensile strain. Furthermore, variable stiffness distribution of Spring Cell metamaterials is demonstrated while maintaining large strain zero Poisson’s ratio. The frequency and buckling analysis of metamaterials formed by spring cells are investigated and compared with equivalent shell. Moreover, their mechanical behaviours including buckling and frequency are investigated. Experiment analysis is performed to validate the force–displacement, Poisson’s ratio and deformation mechanisms discussed in numerical simulations. Finally, construction material analysis is taking to investigate the relations between metamaterial Poisson’s ratio and Young’s modulus and variety types of construction material.
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    Modelling and performance evaluation of sustainable arresting gear energy recovery system for commercial aircraft
    (Taylor & Francis, 2022-11-21) Deja, Jakub; Dayyani, Iman; Skote, Martin
    A significant amount of kinetic energy is dissipated during each commercial aircraft landing. To improve energy efficiency and environmental sustainability, the kinetic energy can instead be converted to electricity by utilizing the arresting gear systems. This paper presents a novel design that couples an arresting gear system to electrical generators. The results show that the system can successfully recover aircraft kinetic energy and is applicable to different aircraft sizes ranging from Airbus A319 up to A380. Beyond system performance, wider context technical aspects including system integration into grid with multiple energy storage possibilities, safety and passenger comfort are discussed.
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    More electric aircraft conversion to all-electric during ground operations: battery powered landing gear drive system
    (IEEE, 2023-03-28) Deja, Jakub; Dayyani, Iman; Nair, Varun; Skote, Martin
    Raising awareness about environmental issues moves the aerospace industry towards electrification and the corresponding solutions are already present at some airports. However, commercial aircraft are the missing links in claiming the all-electric ground operations. They rely on fossil fuels without any electric alternative due to the technological inability to store large amounts of energy while maintaining low weight of batteries. The issue diminishes if an electric system uses only a fraction of energy normally consumed by the engines and comprises kinetic energy recovery. Accordingly, this paper demonstrates the landing gear drive system for a narrowbody air-plane which has the sustainable and economic means to replace all onboard engines throughout ground operations. The system is simulated in MATLAB/Simulink and leads to the kinematic results which are based on the real drive cycles. The kinematics are subsequently used to estimate the overall on-ground power and energy demand of a more electric aircraft (MEA). The impact is maximized with the components scaled according to performance metrics and two-speed gear ratio optimization. The net fuel advantage is demonstrated for different ground operation modes, taxi times and flight path lengths.
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    Multi-material topology optimization for composite metal aircraft structures
    (2017-08-31) Liu, Cheng; Yasaee, Mehdi; Dayyani, Iman
    This paper investigates an optimization routine for lightweight composite-metal hybrid aircraft structures. This routine is developed based on two existing topology optimization approaches, Moving Morphable Components (MMC) and level set method updated by a reaction diffusion equation. The proposed method overcomes the weakness of conventional multi-material optimizers by introducing some rules of material distribution, that enhance the manufacturability of the optimal structure. It is achieved by optimizing the main structural frame using uniform-width components first, leaving the joints as void together with the remaining design domain, and following by a conventional topology optimization using single-material level set approach. A commonly used beam model is optimized to demonstrate the key ideas of the proposed routine.
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    Multi-objective optimization for the geometry of trapezoidal corrugated morphing skins
    (Springer, 2016-05-11) Dayyani, Iman; Friswell, M. I.
    Morphing concepts have great importance for the design of future aircraft as they provide the opportunity for the aircraft to adapt their shape in flight so as to always match the optimal configuration. This enables the aircraft to have a better performance, such as reducing fuel consumption, toxic emissions and noise pollution or increasing the maneuverability of the aircraft. However the requirements of morphing aircraft are conflicting from the structural perspective. For instance the design of a morphing skin is a key issue since it must be stiff to withstand the aerodynamic loads, but flexible to enable the large shape changes. Corrugated sheets have remarkable anisotropic characteristics. As a candidate skin for a morphing wing, they are stiff to withstand the aerodynamic loads and flexible to enable the morphing deformations. This work presents novel insights into the multi-objective optimization of a trapezoidal corrugated core with elastomer coating. The geometric parameters of the coated composite corrugated panels are optimized to minimize the in-plane stiffness and the weight of the skin and to maximize the flexural out-of-plane stiffness of the skin. These objective functions were calculated by use of an equivalent finite element code. The gradient-based aggregate method is selected to solve the optimization problem and is validated by comparing to the GA multi-objective optimization technique. The trend of the optimized objectives and parameters are discussed in detail; for example the optimum corrugation often has the maximum corrugation height. The obtained results provide important insights into the design of morphing corrugated skins.
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    Multi-objective shape optimization of large strain 3D helical structures for mechanical metamaterials
    (Elsevier, 2022-02-18) Cimolai, Guglielmo; Dayyani, Iman; Qin, Qing
    The need for mechanical metamaterials with large strain range and lightweight properties are evidenced to engineering applications. In this regard, novel helical structures are proposed as suitable unit cell’s components of mechanical metamaterials. Three-dimensional helical structures composed of varying coil numbers, defined in a cylindrical spatial domain are shape optimized through genetic algorithm in a finite element script for conflicting objectives of minimum mass and maximum tensile range. The superior performance of the shape optimized helical structure is highlighted in terms of structural rigidity, large deformation capability, buckling and vibrational modal analysis in compare to equivalent coil springs of identical weight and comparable domain. Deformation mechanism is analyzed carefully to justify the improved performances of proposed structure. Tensile and compressive experimental analysis are undertaken to validate the enhanced strain ranges. One dimensional metamaterials implementations with various tessellation arrangements are simulated. Results show that the proposed design can effectively generate lightweight substitutes of metamaterials unit cells ligaments to improve the strain range performance. Planar and lattice metamaterial concepts employing shape optimized helical structure are illustrated to demonstrate the possibilities of promoting lightweight structural integrities in the design of mechanical metamaterials.
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    Multi-objective topology optimization and structural analysis of periodic spaceframe structures
    (Elsevier, 2020-02-05) Lim, Jarad; You, Chao; Dayyani, Iman
    Reduction of structural weight provides significant benefits in many engineering applications. While methods to optimise structural shape and topology of both continuous solids and discrete frame structures have existed for a while, the advent of additive layer manufacturing processes has enabled more complex geometries to be feasible. In this paper, a periodic spaceframe structure is designed for minimum mass and maximum effective flexural and torsional rigidities. A method of parametrising the spaceframe through its constituent unit cells is proposed, and Genetic Algorithm (GA) multi-objective optimisation is used to optimise its topology, size and geometry as a generic structure. The superior performance of the topology optimised periodic spaceframe is highlighted in terms of structural rigidity, large deformation capability, buckling and vibrational modal analysis in compare to equivalent beam structures of identical weight and comparable domain. The results show that the proposed method can effectively generate lightweight substitute structures of great mechanical performance in many beam structures applications, such as: aircraft wing spars. The periodic spaceframe is applied into a conventional aircraft wing structure to demonstrate the possibilities of promoting weight saving in the design of civil aircraft wings.
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    Neural network assisted Ga optimization of adhesively bonded composite joints
    (Unknown, 2022) Arhore, Edore G.; Yasaee, Mehdi; Dayyani, Iman