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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Thu, 30 May 2024 19:14:03 GMT2024-05-30T19:14:03ZVariable-stiffness composites optimisation under multiple design requirements and loads
http://hdl.handle.net/10985/25063
Variable-stiffness composites optimisation under multiple design requirements and loads
IZZI, Michele Iacopo; MONTEMURRO, Marco; CATAPANO, Anita
The aim of this paper is twofold. On the one hand, it presents a methodology for the deterministic optimisation of a general class of variable-stiffness composite (VSC) structures, including a solution obtained by using laminĂ¦ with a curvilinear fibres-path and variable-thickness, by considering different design requirements under multiple load cases. The considered framework is the multi-level design methodology based on the polar parameters (PPs) to describe the macroscopic behaviour of the VSC structure. Particularly, only the first-level problem is addressed in this work: the design variables are, thus, the PPs and the thickness of the VSC laminate, whose spatial distribution is described via basis spline (B-spline) surfaces. The goal is to minimise the mass of the VSC structure subject to design requirements on feasibility, strength, first buckling load and maximum curvature of the fibres-path. This latter is formulated as an equivalent (conservative) constraint in the PPs space, regardless of the fibres-path within each lamina. Moreover, a general formulation of the gradient of the requirements related to buckling load and strength is proposed, which takes advantage from the main properties of B-spline entities and PPs. On the other hand, this paper aims to propose a new benchmark problem that is representative of a panel belonging to the fuselage of a standard civil aircraft subjected to multiple loading conditions. To this end, a wide campaign of numerical tests has been performed by considering a sensitivity analysis of the optimised solution to: (a) the integer parameters involved in the definition of the B-spline entities describing the distribution of the PPs and, possibly, of the thickness, (b) the type of VSC structure, (c) the type of deterministic optimisation algorithm. The results can be used as a database to assess the effectiveness of different design strategies against the optimised solutions presented in this paper.
Wed, 01 Nov 2023 00:00:00 GMThttp://hdl.handle.net/10985/250632023-11-01T00:00:00ZIZZI, Michele IacopoMONTEMURRO, MarcoCATAPANO, AnitaThe aim of this paper is twofold. On the one hand, it presents a methodology for the deterministic optimisation of a general class of variable-stiffness composite (VSC) structures, including a solution obtained by using laminĂ¦ with a curvilinear fibres-path and variable-thickness, by considering different design requirements under multiple load cases. The considered framework is the multi-level design methodology based on the polar parameters (PPs) to describe the macroscopic behaviour of the VSC structure. Particularly, only the first-level problem is addressed in this work: the design variables are, thus, the PPs and the thickness of the VSC laminate, whose spatial distribution is described via basis spline (B-spline) surfaces. The goal is to minimise the mass of the VSC structure subject to design requirements on feasibility, strength, first buckling load and maximum curvature of the fibres-path. This latter is formulated as an equivalent (conservative) constraint in the PPs space, regardless of the fibres-path within each lamina. Moreover, a general formulation of the gradient of the requirements related to buckling load and strength is proposed, which takes advantage from the main properties of B-spline entities and PPs. On the other hand, this paper aims to propose a new benchmark problem that is representative of a panel belonging to the fuselage of a standard civil aircraft subjected to multiple loading conditions. To this end, a wide campaign of numerical tests has been performed by considering a sensitivity analysis of the optimised solution to: (a) the integer parameters involved in the definition of the B-spline entities describing the distribution of the PPs and, possibly, of the thickness, (b) the type of VSC structure, (c) the type of deterministic optimisation algorithm. The results can be used as a database to assess the effectiveness of different design strategies against the optimised solutions presented in this paper.A multi-scale approach for the optimum design of sandwich plates with honeycomb core. Part II: the optimisation strategy
http://hdl.handle.net/10985/8493
A multi-scale approach for the optimum design of sandwich plates with honeycomb core. Part II: the optimisation strategy
MONTEMURRO, Marco; CATAPANO, Anita
This work deals with the problem of the optimum design of a sandwich panel. The design strategy that we propose is a numerical optimisation procedure that does not make any simplifying assumption to obtain a true global optimum configuration of the system. To face the design of the sandwich structure at both meso and macro scales, we use a two-level optimisation strategy: at the first level we determine the optimal geometry of the unit cell of the core together with the material and geometric parameters of the laminated skins, while at the second level we determine the optimal skins lay-up giving the geometrical and material parameters issued from the first level. The two-level strategy relies both on the use of the polar formalism for the description of the anisotropic behaviour of the laminates and on the use of a genetic algorithm as optimisation tool to perform the solution search. To prove its effectiveness, we apply our strategy to the least-weight design of a sandwich plate, satisfying several constraints: on the first buckling load, on the positive-definiteness of the stiffness tensor of the core, on the ratio between skins and core thickness and on the admissible moduli for the laminated skins.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/84932014-01-01T00:00:00ZMONTEMURRO, MarcoCATAPANO, AnitaThis work deals with the problem of the optimum design of a sandwich panel. The design strategy that we propose is a numerical optimisation procedure that does not make any simplifying assumption to obtain a true global optimum configuration of the system. To face the design of the sandwich structure at both meso and macro scales, we use a two-level optimisation strategy: at the first level we determine the optimal geometry of the unit cell of the core together with the material and geometric parameters of the laminated skins, while at the second level we determine the optimal skins lay-up giving the geometrical and material parameters issued from the first level. The two-level strategy relies both on the use of the polar formalism for the description of the anisotropic behaviour of the laminates and on the use of a genetic algorithm as optimisation tool to perform the solution search. To prove its effectiveness, we apply our strategy to the least-weight design of a sandwich plate, satisfying several constraints: on the first buckling load, on the positive-definiteness of the stiffness tensor of the core, on the ratio between skins and core thickness and on the admissible moduli for the laminated skins.Thermo-mechanical homogenisation of cork-based composites: variability in materials properties and propagation of uncertainty
http://hdl.handle.net/10985/16435
Thermo-mechanical homogenisation of cork-based composites: variability in materials properties and propagation of uncertainty
DELUCIA, Marco; PAILHES, Jerome; MONTEMURRO, Marco; CATAPANO, Anita
The last decades have been characterized by a growth of raw material demand, in particular due to the consumerism in developed countries and to the fast industrialization of emerging economies. Nowadays, with the aim to minimise the environmental impact due to the consistent reduction of primary resources, the main objective in the research field of industrial materials is replacing synthetic and non-renewable materials by natural and renewable ones showing similar or even better properties. In the last years, among natural, renewable and biodegradable materials, cork has attracted the attention of both scientific and industrial communities thanks to its remarkable properties as lightness, excellent thermal and acoustic insulating capabilities mainly due to its honeycomb-like microstructure. Cork is extracted from the outer bark of Quercus Suber L. and in its natural form can be directly exploited to produce small and limited size products, e.g. cork stoppers. With the purpose to extend its field of application, cork is often used in the form of particles embedded in polymeric matrix in order to obtain cork-based agglomerates or composites [1]. Main design parameters as the density, the material properties, the fraction and the size of cork particles, the material of polymeric matrix, the manufacturing process and the overall packing density affect the thermomechanical properties of cork-based agglomerates [2]. The aim of the present work is to propose a general and efficient multi-scale numerical homogenisation strategy capable of determining the effective thermal and mechanical properties of cork-based agglomerates. A 2D (Fig.1) as well as a 3D finite element model (Fig.2) based on Voronoi's tessellation algorithm have been built and the strain energy homogenisation technique has been used for both models to determine the elastic and thermal properties of cork-based composites. In these models, parameters defining the representative volume element (RVE) are: the grain shape, grain orientation, grain matrix and cork material properties, volume fraction of the components, as well as the properties of the grain/matrix interface. Moreover, it must be pointed out that in cork-based composites, some of these parameters, as the mechanical properties of cork as well as the number, size and distribution of pores within the agglomerate, exhibit a high variability. In particular, the variability of density, porosity and chemical composition of the outer bark of Quercus Suber L. (which are strongly affected by the geographical location of cork production) explains the natural variability of the mechanical as well as thermal properties of cork. Therefore this aspect is of paramount importance when modelling and designing cork-based composite structures. For this reason, the variability of the properties mentioned above has been introduced in the FE model through a suitable probability density function [3]. More precisely, the Monte Carlo method has been used to study the effect of the variability of the model inputs on the equivalent thermo-elastic behaviour of the cork-based agglomerate at the macroscopic scale [4]. The result of the analysis has been interpreted in a statistical manner: the probability of every output quantity depends on the input probabilities and their correlations. Effective thermo-mechanical properties of different cork-based composites have been estimated and numerical results have been compared to the experimental ones in order to show the effectiveness of the proposed strategy.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/164352019-01-01T00:00:00ZDELUCIA, MarcoPAILHES, JeromeMONTEMURRO, MarcoCATAPANO, AnitaThe last decades have been characterized by a growth of raw material demand, in particular due to the consumerism in developed countries and to the fast industrialization of emerging economies. Nowadays, with the aim to minimise the environmental impact due to the consistent reduction of primary resources, the main objective in the research field of industrial materials is replacing synthetic and non-renewable materials by natural and renewable ones showing similar or even better properties. In the last years, among natural, renewable and biodegradable materials, cork has attracted the attention of both scientific and industrial communities thanks to its remarkable properties as lightness, excellent thermal and acoustic insulating capabilities mainly due to its honeycomb-like microstructure. Cork is extracted from the outer bark of Quercus Suber L. and in its natural form can be directly exploited to produce small and limited size products, e.g. cork stoppers. With the purpose to extend its field of application, cork is often used in the form of particles embedded in polymeric matrix in order to obtain cork-based agglomerates or composites [1]. Main design parameters as the density, the material properties, the fraction and the size of cork particles, the material of polymeric matrix, the manufacturing process and the overall packing density affect the thermomechanical properties of cork-based agglomerates [2]. The aim of the present work is to propose a general and efficient multi-scale numerical homogenisation strategy capable of determining the effective thermal and mechanical properties of cork-based agglomerates. A 2D (Fig.1) as well as a 3D finite element model (Fig.2) based on Voronoi's tessellation algorithm have been built and the strain energy homogenisation technique has been used for both models to determine the elastic and thermal properties of cork-based composites. In these models, parameters defining the representative volume element (RVE) are: the grain shape, grain orientation, grain matrix and cork material properties, volume fraction of the components, as well as the properties of the grain/matrix interface. Moreover, it must be pointed out that in cork-based composites, some of these parameters, as the mechanical properties of cork as well as the number, size and distribution of pores within the agglomerate, exhibit a high variability. In particular, the variability of density, porosity and chemical composition of the outer bark of Quercus Suber L. (which are strongly affected by the geographical location of cork production) explains the natural variability of the mechanical as well as thermal properties of cork. Therefore this aspect is of paramount importance when modelling and designing cork-based composite structures. For this reason, the variability of the properties mentioned above has been introduced in the FE model through a suitable probability density function [3]. More precisely, the Monte Carlo method has been used to study the effect of the variability of the model inputs on the equivalent thermo-elastic behaviour of the cork-based agglomerate at the macroscopic scale [4]. The result of the analysis has been interpreted in a statistical manner: the probability of every output quantity depends on the input probabilities and their correlations. Effective thermo-mechanical properties of different cork-based composites have been estimated and numerical results have been compared to the experimental ones in order to show the effectiveness of the proposed strategy.A multi-scale approach for the optimum design of sandwich plates with honeycomb core. Part I: homogenisation of core properties
http://hdl.handle.net/10985/8498
A multi-scale approach for the optimum design of sandwich plates with honeycomb core. Part I: homogenisation of core properties
MONTEMURRO, Marco; CATAPANO, Anita
This work deals with the problem of the optimum design of a sandwich panel. The design process is based on a general two-level optimisation strategy involving different scales: the meso-scale for both the unit cell of the core and the constitutive layer of the laminated skins and the macro-scale for the whole panel. Concerning the meso-scale of the honeycomb core, an appropriate model of the unit cell able to properly provide its effective elastic properties (to be used at the macro-scale) must be conceived. To this purpose, in this first paper, we present the numerical homogenisation technique as well as the related finite element model of the unit cell which makes use of solid elements instead of the usual shell ones. A numerical study to determine the effective properties of the honeycomb along with a comparison with existing models and a sensitive analysis in terms of the geometric parameters of the unit cell have been conducted. Numerical results show that shell-based models are no longer adapted to evaluate the core properties, mostly in the context of an optimisation procedure where the parameters of the unit cell can get values that go beyond the limits imposed by a 2D model.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/84982014-01-01T00:00:00ZMONTEMURRO, MarcoCATAPANO, AnitaThis work deals with the problem of the optimum design of a sandwich panel. The design process is based on a general two-level optimisation strategy involving different scales: the meso-scale for both the unit cell of the core and the constitutive layer of the laminated skins and the macro-scale for the whole panel. Concerning the meso-scale of the honeycomb core, an appropriate model of the unit cell able to properly provide its effective elastic properties (to be used at the macro-scale) must be conceived. To this purpose, in this first paper, we present the numerical homogenisation technique as well as the related finite element model of the unit cell which makes use of solid elements instead of the usual shell ones. A numerical study to determine the effective properties of the honeycomb along with a comparison with existing models and a sensitive analysis in terms of the geometric parameters of the unit cell have been conducted. Numerical results show that shell-based models are no longer adapted to evaluate the core properties, mostly in the context of an optimisation procedure where the parameters of the unit cell can get values that go beyond the limits imposed by a 2D model.A Cellular Potts energy-based approach to analyse the influence of the surface topography on single cell motility
http://hdl.handle.net/10985/19921
A Cellular Potts energy-based approach to analyse the influence of the surface topography on single cell motility
THENARD, Thomas; MESNARD, Michel; ALLENA, Rachele; CATAPANO, Anita
cellular scale level, the cell behaviour, especially its migration, is affected by the specificities of the surface of the substrate, such as the stiffness of the surface and its roughness topography. The latter has been shown to have a great impact on various cell mechanisms, such as the cell adhesion, migration, or proliferation. In fact, the mere presence of micro roughness leads to an improvement of those mechanisms, with a better integration of the implants. However, the phenomena behind those improvements are still not clear. In this paper, we propose a three-dimensional (3D) model of a single cell migration using a Cellular Potts (CP) model to study the influence of the surface topography on cell motility. To do so, various configurations were tested, such as: (i) a substrate with a random roughness, (ii) a substrate with a rectangular groove pattern (parallel and perpendicular to the direction of motion), (ii) a substrate with a sinusoidal groove pattern. To evaluate the influence of the surface topography on cell motility, for each configuration, the cell speed and shape as well as the contact surface between the cell and the substrate have been quantified. Our numerical results demonstrate that, in agreement with the experimental observations of the literature, the substrate topography has an influence on the cell efficiency (i.e. cell speed), orientation and shape. Besides, we also show that the increase of the contact surface alone in presence of roughness is not enough to explain the improvement of cell migration on the various rough surfaces. Finally, we highlight the importance of the roughness dimension on cell motility. This could be a critical aspect to consider for further analyses and applications, such as surface treatments for medical applications.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/199212021-01-01T00:00:00ZTHENARD, ThomasMESNARD, MichelALLENA, RacheleCATAPANO, Anitacellular scale level, the cell behaviour, especially its migration, is affected by the specificities of the surface of the substrate, such as the stiffness of the surface and its roughness topography. The latter has been shown to have a great impact on various cell mechanisms, such as the cell adhesion, migration, or proliferation. In fact, the mere presence of micro roughness leads to an improvement of those mechanisms, with a better integration of the implants. However, the phenomena behind those improvements are still not clear. In this paper, we propose a three-dimensional (3D) model of a single cell migration using a Cellular Potts (CP) model to study the influence of the surface topography on cell motility. To do so, various configurations were tested, such as: (i) a substrate with a random roughness, (ii) a substrate with a rectangular groove pattern (parallel and perpendicular to the direction of motion), (ii) a substrate with a sinusoidal groove pattern. To evaluate the influence of the surface topography on cell motility, for each configuration, the cell speed and shape as well as the contact surface between the cell and the substrate have been quantified. Our numerical results demonstrate that, in agreement with the experimental observations of the literature, the substrate topography has an influence on the cell efficiency (i.e. cell speed), orientation and shape. Besides, we also show that the increase of the contact surface alone in presence of roughness is not enough to explain the improvement of cell migration on the various rough surfaces. Finally, we highlight the importance of the roughness dimension on cell motility. This could be a critical aspect to consider for further analyses and applications, such as surface treatments for medical applications.Multi-scale optimisation of thin-walled structures by considering a global/local modelling approach
http://hdl.handle.net/10985/19269
Multi-scale optimisation of thin-walled structures by considering a global/local modelling approach
IZZI, Michele Iacopo; FANTERIA, Daniele; PAILHES, Jerome; MONTEMURRO, Marco; CATAPANO, Anita
In this work, a design strategy for optimising thin-walled structures based on a global-local finite element (FE) modelling approach is presented. The preliminary design of thin-walled structures can be stated in the form of a constrained non-linear programming problem (CNLPP) involving requirements of different nature intervening at the different scales of the structure. The proposed multi-scale optimisation (MSO) strategy is characterised by two main features. Firstly, the CNLPP is formulated in the most general sense by including all design variables involved at each pertinent scale of the problem. Secondly, two scales (with the related design requirements) are considered: i) the structure macroscopic scale, where low-fidelity FE models are used; ii) the structure mesoscopic scale (or component-level), where more accurate FE models are involved. In particular, the mechanical responses of the structure are evaluated at both global and local scales, avoiding the use of approximated analytical methods. The MSO is here applied to the least-weight design of an aluminium fuselage barrel of a wide-body aircraft. Fully parametric global and local FE models are interfaced with an in-house metaheuristic algorithm. Refined local FE models are created only for critical regions of the structure, automatically detected during the global analysis, and linked to the global one thanks to the implementation of a sub-modelling approach. The whole process is completely automated and, once set, it does not need any further user intervention.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10985/192692020-01-01T00:00:00ZIZZI, Michele IacopoFANTERIA, DanielePAILHES, JeromeMONTEMURRO, MarcoCATAPANO, AnitaIn this work, a design strategy for optimising thin-walled structures based on a global-local finite element (FE) modelling approach is presented. The preliminary design of thin-walled structures can be stated in the form of a constrained non-linear programming problem (CNLPP) involving requirements of different nature intervening at the different scales of the structure. The proposed multi-scale optimisation (MSO) strategy is characterised by two main features. Firstly, the CNLPP is formulated in the most general sense by including all design variables involved at each pertinent scale of the problem. Secondly, two scales (with the related design requirements) are considered: i) the structure macroscopic scale, where low-fidelity FE models are used; ii) the structure mesoscopic scale (or component-level), where more accurate FE models are involved. In particular, the mechanical responses of the structure are evaluated at both global and local scales, avoiding the use of approximated analytical methods. The MSO is here applied to the least-weight design of an aluminium fuselage barrel of a wide-body aircraft. Fully parametric global and local FE models are interfaced with an in-house metaheuristic algorithm. Refined local FE models are created only for critical regions of the structure, automatically detected during the global analysis, and linked to the global one thanks to the implementation of a sub-modelling approach. The whole process is completely automated and, once set, it does not need any further user intervention.On the effective integration of manufacturability constraints within the multi-scale methodology for designing variable angle-tow laminates
http://hdl.handle.net/10985/11438
On the effective integration of manufacturability constraints within the multi-scale methodology for designing variable angle-tow laminates
MONTEMURRO, Marco; CATAPANO, Anita
In this work a multi-scale two-level (MS2L) optimisation strategy for optimising VAT composites is presented. In the framework of the MS2L methodology, the design problem is split and solved into two steps. At the first step the goal is to determine the optimum distribution of the laminate stiffness properties over the structure (macroscopic scale), while the second step aims at retrieving the optimum fibres-path in each layer meeting all the requirements provided by the problem at hand (mesoscopic scale). The MS2L strategy has been improved in order to integrate all types of requirements (mechanical, manufacturability, geometric, etc.) within the first-level problem.The proposed approach relies on: a) the polar formalism for describing the behaviour of the VAT laminate, b) the iso-geometric surfaces for describing the spatial variation of both the laminate stiffness properties (macro-scale) and the layers fibres-path (meso-scale) and c) an hybrid optimisation tool (genetic and gradient-based algorithms) to perform the solution search. The effectiveness of the MS2L strategy is proven through a numerical example on the maximisation of the first buckling factor of a VAT plate subject to both mechanical and manufacturability constraints.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/114382017-01-01T00:00:00ZMONTEMURRO, MarcoCATAPANO, AnitaIn this work a multi-scale two-level (MS2L) optimisation strategy for optimising VAT composites is presented. In the framework of the MS2L methodology, the design problem is split and solved into two steps. At the first step the goal is to determine the optimum distribution of the laminate stiffness properties over the structure (macroscopic scale), while the second step aims at retrieving the optimum fibres-path in each layer meeting all the requirements provided by the problem at hand (mesoscopic scale). The MS2L strategy has been improved in order to integrate all types of requirements (mechanical, manufacturability, geometric, etc.) within the first-level problem.The proposed approach relies on: a) the polar formalism for describing the behaviour of the VAT laminate, b) the iso-geometric surfaces for describing the spatial variation of both the laminate stiffness properties (macro-scale) and the layers fibres-path (meso-scale) and c) an hybrid optimisation tool (genetic and gradient-based algorithms) to perform the solution search. The effectiveness of the MS2L strategy is proven through a numerical example on the maximisation of the first buckling factor of a VAT plate subject to both mechanical and manufacturability constraints.A multi-scale approach for the simultaneous shape and material optimisation of sandwich panels with cellular core
http://hdl.handle.net/10985/10674
A multi-scale approach for the simultaneous shape and material optimisation of sandwich panels with cellular core
DOROSZEWSKI, Dominique; MONTEMURRO, Marco; CATAPANO, Anita
This work deals with the problem of the optimum design of a sandwich panel made of carbon-epoxy skins and a metallic cellular core. The proposed design strategy is a multi-scale numerical optimisation procedure that does not make use of any simplifying hypothesis to obtain a true global optimum configuration of the system. To face the design of the sandwich structure at both meso and macro scales, a two-level optimisation strategy is employed: at the first level the goal is the determination of the optimum shape of the unit cell of the core (meso-scale) together with the material and geometric parameters of the laminated skins (macro-scale), while at the second level the objective is the design of the skins stacking sequence (skin meso-scale) meeting the geometrical and material parameters provided by the first-level problem. The two-level strategy is founded on the polar formalism for the description of the anisotropic behaviour of the laminates, on the NURBS basis functions for representing the shape of the unit cell and on the use of a genetic algorithm as optimisation tool to perform the solution search. To prove its effectiveness, the multi-scale strategy is applied to the least-weight design of a sandwich plate subject to constraints of different nature: on the positive-definiteness of the stiffness tensor of the core, on the admissible material properties of the laminated faces, on the local buckling load of the unit cell, on the global buckling load of the panel and geometrical as well as manufacturability constraints related to the fabrication process of the cellular core.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/106742016-01-01T00:00:00ZDOROSZEWSKI, DominiqueMONTEMURRO, MarcoCATAPANO, AnitaThis work deals with the problem of the optimum design of a sandwich panel made of carbon-epoxy skins and a metallic cellular core. The proposed design strategy is a multi-scale numerical optimisation procedure that does not make use of any simplifying hypothesis to obtain a true global optimum configuration of the system. To face the design of the sandwich structure at both meso and macro scales, a two-level optimisation strategy is employed: at the first level the goal is the determination of the optimum shape of the unit cell of the core (meso-scale) together with the material and geometric parameters of the laminated skins (macro-scale), while at the second level the objective is the design of the skins stacking sequence (skin meso-scale) meeting the geometrical and material parameters provided by the first-level problem. The two-level strategy is founded on the polar formalism for the description of the anisotropic behaviour of the laminates, on the NURBS basis functions for representing the shape of the unit cell and on the use of a genetic algorithm as optimisation tool to perform the solution search. To prove its effectiveness, the multi-scale strategy is applied to the least-weight design of a sandwich plate subject to constraints of different nature: on the positive-definiteness of the stiffness tensor of the core, on the admissible material properties of the laminated faces, on the local buckling load of the unit cell, on the global buckling load of the panel and geometrical as well as manufacturability constraints related to the fabrication process of the cellular core.A new paradigm for the optimum design of variable angle tow laminates
http://hdl.handle.net/10985/11387
A new paradigm for the optimum design of variable angle tow laminates
MONTEMURRO, Marco; CATAPANO, Anita
In this work the authors propose a new paradigm for the optimum design of variable angle tow (VAT) composites. They propose a generalisation of a multi-scale two-level (MS2L) optimisation strategy already employed to solve optimisation problems of anisotropic structures characterised by a constant stiffness distribution. In the framework of the MS2L methodology, the design problem is split into two sub-problems. At the first step of the strategy the goal is to determine the optimum distribution of the laminate stiffness properties over the structure, while the second step aims at retrieving the optimum fibres-path in each layer meeting all the requirements provided by the problem at hand. The MS2L strategy relies on: a) the polar formalism for describing the behaviour of the VAT laminate, b) the iso-geometric surfaces for describing the spatial variation of the stiffness properties and c) an hybrid optimisation tool (genetic and gradient-based algorithms) to perform the solution search. The effectiveness of the MS2L strategy is proven through a numerical example on the maximisation of the first buckling factor of a VAT plate subject to both mechanical and manufacturability constraints.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/113872016-01-01T00:00:00ZMONTEMURRO, MarcoCATAPANO, AnitaIn this work the authors propose a new paradigm for the optimum design of variable angle tow (VAT) composites. They propose a generalisation of a multi-scale two-level (MS2L) optimisation strategy already employed to solve optimisation problems of anisotropic structures characterised by a constant stiffness distribution. In the framework of the MS2L methodology, the design problem is split into two sub-problems. At the first step of the strategy the goal is to determine the optimum distribution of the laminate stiffness properties over the structure, while the second step aims at retrieving the optimum fibres-path in each layer meeting all the requirements provided by the problem at hand. The MS2L strategy relies on: a) the polar formalism for describing the behaviour of the VAT laminate, b) the iso-geometric surfaces for describing the spatial variation of the stiffness properties and c) an hybrid optimisation tool (genetic and gradient-based algorithms) to perform the solution search. The effectiveness of the MS2L strategy is proven through a numerical example on the maximisation of the first buckling factor of a VAT plate subject to both mechanical and manufacturability constraints.Optimal design of sandwich plates with honeycomb core
http://hdl.handle.net/10985/8504
Optimal design of sandwich plates with honeycomb core
MONTEMURRO, Marco; CATAPANO, Anita
This work deals with the problem of the optimum design of a sandwich structure composed of two laminated skins and a honeycomb core. The goal is to propose a numerical optimisation procedure that does not make any simplifying hypothesis in order to obtain a true global optimal solution for the considered problem. In order to face the design of the sandwich structure at both meso and macro scales, we use a two-level optimisation strategy. At the first level, we determine the optimum geometry of the unit cell together with the material and geometric parameters of the laminated skins, while at the second level we determine the optimal skins lay-up giving the geometrical and material parameters issued from the first level. We will illustrate the application of our strategy to the least-weight design of a sandwich plate submitted to several constraints: on the first buckling load, on the positive-definiteness of the stiffness tensor of the core, on the ratio between skins and core thickness and on the admissible moduli for the laminated skins.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/85042014-01-01T00:00:00ZMONTEMURRO, MarcoCATAPANO, AnitaThis work deals with the problem of the optimum design of a sandwich structure composed of two laminated skins and a honeycomb core. The goal is to propose a numerical optimisation procedure that does not make any simplifying hypothesis in order to obtain a true global optimal solution for the considered problem. In order to face the design of the sandwich structure at both meso and macro scales, we use a two-level optimisation strategy. At the first level, we determine the optimum geometry of the unit cell together with the material and geometric parameters of the laminated skins, while at the second level we determine the optimal skins lay-up giving the geometrical and material parameters issued from the first level. We will illustrate the application of our strategy to the least-weight design of a sandwich plate submitted to several constraints: on the first buckling load, on the positive-definiteness of the stiffness tensor of the core, on the ratio between skins and core thickness and on the admissible moduli for the laminated skins.