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http://hdl.handle.net/10985/8514
Architecture and materials selection in multi-materials design
BARACCHINI, Paul; GUILLEBAUD, Claire; KROMM, François-Xavier; WARGNIER, Hervé; MONTEMURRO, Marco; CATAPANO, Anita
The design process involving both the architecture and the materials represents an hard task mainly due to the high number of potential configurations, thus requiring firstly the development of new and more rigorous approaches but also the development of new tools. To this purpose, we present in this work a new strategy for the design of architectured materials. Such a strategy relies on one hand on the construction of some databases for the selection of both geometrical patterns and materials, and on the other hand on the use of well-known analytical models to describe the physical behaviour of the multi-material. In order to prove its effectiveness, we apply our strategy to the problem of the least-weight design of a multilayer plate that has to meet thermal, electrical and mechanical requirements. Moreover, we use a genetic algorithm, as a numerical tool, to perform the solution search for our problem. Numerical results show that we can obtain optimum configurations characterised by a weight saving up to 59% keeping the same (or even superior) thermal, electrical and stiffness properties than those of a monolithic reference plate.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/85142014-01-01T00:00:00ZBARACCHINI, PaulGUILLEBAUD, ClaireKROMM, François-XavierWARGNIER, HervéMONTEMURRO, MarcoCATAPANO, AnitaThe design process involving both the architecture and the materials represents an hard task mainly due to the high number of potential configurations, thus requiring firstly the development of new and more rigorous approaches but also the development of new tools. To this purpose, we present in this work a new strategy for the design of architectured materials. Such a strategy relies on one hand on the construction of some databases for the selection of both geometrical patterns and materials, and on the other hand on the use of well-known analytical models to describe the physical behaviour of the multi-material. In order to prove its effectiveness, we apply our strategy to the problem of the least-weight design of a multilayer plate that has to meet thermal, electrical and mechanical requirements. Moreover, we use a genetic algorithm, as a numerical tool, to perform the solution search for our problem. Numerical results show that we can obtain optimum configurations characterised by a weight saving up to 59% keeping the same (or even superior) thermal, electrical and stiffness properties than those of a monolithic reference plate.A new multi-scale optimisation strategy for designing variable angle tow composites by integrating manufacturing constraints
http://hdl.handle.net/10985/12874
A new multi-scale optimisation strategy for designing variable angle tow composites by integrating manufacturing constraints
MONTEMURRO, Marco
In this work a multi-scale two-level (MS2L) optimisation strategy for optimising variable angle tow (VAT) composites is presented. In the framework of the MS2L methodology [1], [2], [3] 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 design strategy is characterised on the one hand by the refusal of simplifying hypotheses and classical rules usually employed in the framework of the design process of laminates, and on the other hand by a proper and complete mathematical formalisation of the optimum design problem at each characteristic scale (meso-macro). The MS2L strategy relies on the use of the polar formalism (extended to the case of higher-order theories [4], [5]) for the description of the anisotropic behaviour of the composite. The real advantage in using the Verchery's polar method is in the fact that the elastic response of the structure at the macro-scale is described in terms of tensor invariants, the so-called polar parameters, having a precise physical meaning (which is linked to the elastic symmetries of the material) [4]. On the other hand the MS2L strategy relies on the use of a particular genetic algorithm (GA) able to deal with a special class of huge-size optimisation problems (from hundreds to thousands of design variables) defined over a domain of variable dimension, i.e. optimisation problems involving a variable number of design variables [6]. The MS2L strategy has been improved in order to integrate all types of requirements (mechanical, manufacturability, geometric, etc.) within the first-level problem [3]. Several modifications have been introduced in the theoretical and numerical framework of the MS2L design procedure at both first and second levels [2], [3]. At the first level (laminate macroscopic scale) of the procedure, where the VAT laminate is modelled as an equivalent homogeneous anisotropic plate whose mechanical behaviour is described in terms of polar parameters (which vary locally over the structure), the major modifications focus on: 1) the utilisation of higher-order theories (First-order Shear Deformation Theory (FSDT) framework [4], [5] for taking into account the influence of the transverse shear stiffness on the overall mechanical response of VAT composites; 2) the utilisation of B-spline surfaces for obtaining a continuous point-wise variation of the laminate polar parameters; 3) a proper mathematical formalisation of the manufacturability constraints linked to the AFP process in the framework of the B-spline representation and in terms of laminate polar parameters. Regarding the second-level problem (laminate mesoscopic scale, i.e. the ply level) the main modifications is the utilisation of B-spline surfaces for obtaining a continuous point-wise variation of the fibres-path within each ply. Accordingly, the second-level problem (the lay-up design) can now be formulated as an unconstrained minimisation problem as all the requirements (geometrical, technological, mechanical, etc.) are satisfied since the first step of the MS2L strategy. All of these modifications imply several advantages for the resolution of the related optimisation problems (both at first and second level of the strategy) as detailed in [3]. 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/10985/128742017-01-01T00:00:00ZMONTEMURRO, MarcoIn this work a multi-scale two-level (MS2L) optimisation strategy for optimising variable angle tow (VAT) composites is presented. In the framework of the MS2L methodology [1], [2], [3] 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 design strategy is characterised on the one hand by the refusal of simplifying hypotheses and classical rules usually employed in the framework of the design process of laminates, and on the other hand by a proper and complete mathematical formalisation of the optimum design problem at each characteristic scale (meso-macro). The MS2L strategy relies on the use of the polar formalism (extended to the case of higher-order theories [4], [5]) for the description of the anisotropic behaviour of the composite. The real advantage in using the Verchery's polar method is in the fact that the elastic response of the structure at the macro-scale is described in terms of tensor invariants, the so-called polar parameters, having a precise physical meaning (which is linked to the elastic symmetries of the material) [4]. On the other hand the MS2L strategy relies on the use of a particular genetic algorithm (GA) able to deal with a special class of huge-size optimisation problems (from hundreds to thousands of design variables) defined over a domain of variable dimension, i.e. optimisation problems involving a variable number of design variables [6]. The MS2L strategy has been improved in order to integrate all types of requirements (mechanical, manufacturability, geometric, etc.) within the first-level problem [3]. Several modifications have been introduced in the theoretical and numerical framework of the MS2L design procedure at both first and second levels [2], [3]. At the first level (laminate macroscopic scale) of the procedure, where the VAT laminate is modelled as an equivalent homogeneous anisotropic plate whose mechanical behaviour is described in terms of polar parameters (which vary locally over the structure), the major modifications focus on: 1) the utilisation of higher-order theories (First-order Shear Deformation Theory (FSDT) framework [4], [5] for taking into account the influence of the transverse shear stiffness on the overall mechanical response of VAT composites; 2) the utilisation of B-spline surfaces for obtaining a continuous point-wise variation of the laminate polar parameters; 3) a proper mathematical formalisation of the manufacturability constraints linked to the AFP process in the framework of the B-spline representation and in terms of laminate polar parameters. Regarding the second-level problem (laminate mesoscopic scale, i.e. the ply level) the main modifications is the utilisation of B-spline surfaces for obtaining a continuous point-wise variation of the fibres-path within each ply. Accordingly, the second-level problem (the lay-up design) can now be formulated as an unconstrained minimisation problem as all the requirements (geometrical, technological, mechanical, etc.) are satisfied since the first step of the MS2L strategy. All of these modifications imply several advantages for the resolution of the related optimisation problems (both at first and second level of the strategy) as detailed in [3]. 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.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 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.A NURBS-BASED TOPOLOGY OPTIMIZATION METHOD INCLUDING ADDITIVE MANUFACTURING CONSTRAINTS
http://hdl.handle.net/10985/12539
A NURBS-BASED TOPOLOGY OPTIMIZATION METHOD INCLUDING ADDITIVE MANUFACTURING CONSTRAINTS
COSTA, Giulio; PAILHES, Jerome; MONTEMURRO, Marco
In this work, the Solid Isotropic Material with Penalization (SIMP) topology optimization (TO) method is revisited and reformulated within the mathematical framework of NURBS functions. This implies several advantages: firstly, a NURBS surface allows exploiting an implicitly defined filter zone; secondly, the number of optimization variables (i.e. the parameters defining the NURBS surface) is relatively small when compared to the classical SIMP approach. Finally the TO can be carried out by including non-linearity (either geometric or material) or non-conventional manufacturing constraints, as those related to the Additive Manufacturing (AM) technology. In this work the TO is applied to a standard benchmark.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/125392017-01-01T00:00:00ZCOSTA, GiulioPAILHES, JeromeMONTEMURRO, MarcoIn this work, the Solid Isotropic Material with Penalization (SIMP) topology optimization (TO) method is revisited and reformulated within the mathematical framework of NURBS functions. This implies several advantages: firstly, a NURBS surface allows exploiting an implicitly defined filter zone; secondly, the number of optimization variables (i.e. the parameters defining the NURBS surface) is relatively small when compared to the classical SIMP approach. Finally the TO can be carried out by including non-linearity (either geometric or material) or non-conventional manufacturing constraints, as those related to the Additive Manufacturing (AM) technology. In this work the TO is applied to a standard benchmark.Multi-scale characterisation of material properties of composite fabrics through modal tests
http://hdl.handle.net/10985/12540
Multi-scale characterisation of material properties of composite fabrics through modal tests
CAPPELLI, Lorenzo; GUILLAUMAT, Laurent; MONTEMURRO, Marco; DAU, Frédéric
One of the main issues of composite materials is related to the difficulty of characterising the material properties at mesoscopic and microscopic scales. Classical mechanical tests are not able to provide the full set of 3D properties : these tests can provide only the in-plane elastic properties of the constitutive lamina. Therefore, to go beyond the main restrictions imposed by standard destructive tests, this work deals with the problem of characterising the material properties of a multilayer composite plate, through a non-destructive modal test performed at the macro-scale : a multi-scale identification strategy (MSIS) is proposed. The MSIS aims at identifying the constitutive properties by exploiting the information restrained in the composite macroscopic dynamical response. The MSIS relies on the strain energy homogenisation technique of periodic media and on a gradient-based algorithm to perform the solution search. The identification problem is stated as a constrained inverse problem, where the objective function depends upon both experimental and numerical natural frequencies of the specimen. In this background, the optimisation variables are both geometrical and material properties of the constitutive phases composing the representative volume element. The effectiveness of the approach will be proven through a campaign of tests conducted on multilayer composites.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/125402017-01-01T00:00:00ZCAPPELLI, LorenzoGUILLAUMAT, LaurentMONTEMURRO, MarcoDAU, FrédéricOne of the main issues of composite materials is related to the difficulty of characterising the material properties at mesoscopic and microscopic scales. Classical mechanical tests are not able to provide the full set of 3D properties : these tests can provide only the in-plane elastic properties of the constitutive lamina. Therefore, to go beyond the main restrictions imposed by standard destructive tests, this work deals with the problem of characterising the material properties of a multilayer composite plate, through a non-destructive modal test performed at the macro-scale : a multi-scale identification strategy (MSIS) is proposed. The MSIS aims at identifying the constitutive properties by exploiting the information restrained in the composite macroscopic dynamical response. The MSIS relies on the strain energy homogenisation technique of periodic media and on a gradient-based algorithm to perform the solution search. The identification problem is stated as a constrained inverse problem, where the objective function depends upon both experimental and numerical natural frequencies of the specimen. In this background, the optimisation variables are both geometrical and material properties of the constitutive phases composing the representative volume element. The effectiveness of the approach will be proven through a campaign of tests conducted on multilayer composites.Multi-scale identification of elastic properties for anisotropic media through a global hybrid evolutionary-based inverse approach
http://hdl.handle.net/10985/12937
Multi-scale identification of elastic properties for anisotropic media through a global hybrid evolutionary-based inverse approach
CAPPELLI, Lorenzo; GUILLAUMAT, Laurent; MONTEMURRO, Marco; DAU, Frédéric
One of the main issues of composite materials is related to the difficulty of characterising the full set of material properties at both mesoscopic and microscopic scales. Indeed, classical mechanical tests (traction/compression, 3 or 4 points bending tests, etc.) are not able to provide the full set of 3D material properties of composites. Furthermore, these tests can provide only the in-plane elastic properties of the constitutive lamina (i.e at. the laminate mesoscopic scale). Therefore, in order to go beyond the main restrictions imposed by standard destructive tests, this work deals with the problem of characterising the material properties of a composite plate made of unidirectional fibre-reinforced laminae (at each characteristic scale), through a single non-destructive modal test performed at the macroscale, i.e. that of the specimen (the laminate). To face such a problem a general multi-scale identification strategy (MSIS) is proposed. The MSIS aims at identifying the constitutive properties at both micro and meso scales by exploiting the information restrained in the macroscopic dynamical response of the laminate (e.g. in terms of its eigenfrequencies). The MSIS relies on the one hand on the strain energy homogenisation technique of periodic media (for determining the effective elastic properties of the lamina as a function of the geometrical and material properties of the microscopic constitutive phases) and on the other hand on a special hybrid algorithm (genetic algorithm + gradient-based algorithm) in order to perform the solution search for the considered problem. The identification problem is stated as a constrained inverse problem (a least-square constrained problem), where the objective function depends upon both the measured and evaluated (from finite element analysis) natural frequencies of the laminated plate. In this background, the optimisation variables are both geometrical and material properties of the constitutive phases composing the representative volume element (RVE) of the composite. The effectiveness of the proposed approach will be proven through a campaign of experimental/numerical tests conducted on standard laminates made of unidirectional plies.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/129372017-01-01T00:00:00ZCAPPELLI, LorenzoGUILLAUMAT, LaurentMONTEMURRO, MarcoDAU, FrédéricOne of the main issues of composite materials is related to the difficulty of characterising the full set of material properties at both mesoscopic and microscopic scales. Indeed, classical mechanical tests (traction/compression, 3 or 4 points bending tests, etc.) are not able to provide the full set of 3D material properties of composites. Furthermore, these tests can provide only the in-plane elastic properties of the constitutive lamina (i.e at. the laminate mesoscopic scale). Therefore, in order to go beyond the main restrictions imposed by standard destructive tests, this work deals with the problem of characterising the material properties of a composite plate made of unidirectional fibre-reinforced laminae (at each characteristic scale), through a single non-destructive modal test performed at the macroscale, i.e. that of the specimen (the laminate). To face such a problem a general multi-scale identification strategy (MSIS) is proposed. The MSIS aims at identifying the constitutive properties at both micro and meso scales by exploiting the information restrained in the macroscopic dynamical response of the laminate (e.g. in terms of its eigenfrequencies). The MSIS relies on the one hand on the strain energy homogenisation technique of periodic media (for determining the effective elastic properties of the lamina as a function of the geometrical and material properties of the microscopic constitutive phases) and on the other hand on a special hybrid algorithm (genetic algorithm + gradient-based algorithm) in order to perform the solution search for the considered problem. The identification problem is stated as a constrained inverse problem (a least-square constrained problem), where the objective function depends upon both the measured and evaluated (from finite element analysis) natural frequencies of the laminated plate. In this background, the optimisation variables are both geometrical and material properties of the constitutive phases composing the representative volume element (RVE) of the composite. The effectiveness of the proposed approach will be proven through a campaign of experimental/numerical tests conducted on standard laminates made of unidirectional plies.Simultaneous shape and material optimization of sandwich panels with honeycomb core for additive manufacturing
http://hdl.handle.net/10985/9922
Simultaneous shape and material optimization of sandwich panels with honeycomb core for additive manufacturing
DOROSZEWSKI, Dominique; MONTEMURRO, Marco; CATAPANO, Anita
This works deals with the problem of the optimum design of a sandwich plate composed of CFRP faces and Al honeycomb core. The proposed design strategy is a multi-scale numerical optimization procedure that does not make use of any simplifying assumption to find a global optimum configuration of the system. The goal of such a procedure consists in simultaneously optimizing the shape of the unit cell of the honeycomb core (meso-scale) and the geometrical as well as the material parameters of the CFRP laminated skins (meso and macro scales). To prove its effectiveness, the multi-scale optimization strategy is applied to the problem of the least-weight design of a sandwich panel 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 of the core, on the global buckling load of the panel and geometrical as well as manufacturability constraints linked to the fabrication process of the honeycomb core.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/99222015-01-01T00:00:00ZDOROSZEWSKI, DominiqueMONTEMURRO, MarcoCATAPANO, AnitaThis works deals with the problem of the optimum design of a sandwich plate composed of CFRP faces and Al honeycomb core. The proposed design strategy is a multi-scale numerical optimization procedure that does not make use of any simplifying assumption to find a global optimum configuration of the system. The goal of such a procedure consists in simultaneously optimizing the shape of the unit cell of the honeycomb core (meso-scale) and the geometrical as well as the material parameters of the CFRP laminated skins (meso and macro scales). To prove its effectiveness, the multi-scale optimization strategy is applied to the problem of the least-weight design of a sandwich panel 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 of the core, on the global buckling load of the panel and geometrical as well as manufacturability constraints linked to the fabrication process of the honeycomb core.Corrigendum to "An extension of the polar method to the First-order Shear Deformation Theory of laminates" [Compos. Struct. 127 (2015) 328-339]
http://hdl.handle.net/10985/9920
Corrigendum to "An extension of the polar method to the First-order Shear Deformation Theory of laminates" [Compos. Struct. 127 (2015) 328-339]
MONTEMURRO, Marco
Corrigendum to "An extension of the polar method to the First-order Shear Deformation Theory of laminates" [Compos. Struct. 127 (2015) 328-339]
This is a Corrigendum to a previous publication entitled: "An extension of the polar method to the First-order Shear Deformation Theory of laminates"
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/99202015-01-01T00:00:00ZMONTEMURRO, MarcoCorrigendum to "An extension of the polar method to the First-order Shear Deformation Theory of laminates" [Compos. Struct. 127 (2015) 328-339]Low-velocity impact tests on carbon/epoxy composite laminates: A benchmark study
http://hdl.handle.net/10985/11386
Low-velocity impact tests on carbon/epoxy composite laminates: A benchmark study
PANETTIERI, Enrico; FANTERIA, Daniele; FROUSTEY, Catherine; MONTEMURRO, Marco
Low-velocity impacts (LVI) on composite laminates pose significant safety issues since they are able to generate extended damage within the structure, mostly delaminations and matrix cracking, while being hardly detectable in visual inspections. The role of LVI tests at the coupon level is to evaluate quantities that can be useful both in the design process, such as the delamination threshold load, and in dealing with safety issues, that is correlating the internal damage with the indentation depth. This paper aims at providing a benchmark of LVIs on quasi-isotropic carbon/epoxy laminates; 2 laminates are tested, 16 and 24 plies and a total of 8 impact energies have been selected ranging from very low energy impacts up to around 30 J. Delamination threshold loads, shape and extension of délaminations as well as post-impact 3D measurements of the impacted surface have been carried out in order to characterize the behavior of the considered material system in LVIs. The analysis of test results relevant to the lowest energies pointed out that large contact force fluctuations, typically associated to delamination onset, occurred but ultrasonic scans did not reveal any significant internal damage. Due to these unexpected results, such tests were further investigated through a detailed FE model. The results of this investigation highlights the detrimental effects of the dissipative mechanisms of the impactor. A combined numericale-experimental approach is thus proposed to evaluate the effective impact energies.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/113862016-01-01T00:00:00ZPANETTIERI, EnricoFANTERIA, DanieleFROUSTEY, CatherineMONTEMURRO, MarcoLow-velocity impacts (LVI) on composite laminates pose significant safety issues since they are able to generate extended damage within the structure, mostly delaminations and matrix cracking, while being hardly detectable in visual inspections. The role of LVI tests at the coupon level is to evaluate quantities that can be useful both in the design process, such as the delamination threshold load, and in dealing with safety issues, that is correlating the internal damage with the indentation depth. This paper aims at providing a benchmark of LVIs on quasi-isotropic carbon/epoxy laminates; 2 laminates are tested, 16 and 24 plies and a total of 8 impact energies have been selected ranging from very low energy impacts up to around 30 J. Delamination threshold loads, shape and extension of délaminations as well as post-impact 3D measurements of the impacted surface have been carried out in order to characterize the behavior of the considered material system in LVIs. The analysis of test results relevant to the lowest energies pointed out that large contact force fluctuations, typically associated to delamination onset, occurred but ultrasonic scans did not reveal any significant internal damage. Due to these unexpected results, such tests were further investigated through a detailed FE model. The results of this investigation highlights the detrimental effects of the dissipative mechanisms of the impactor. A combined numericale-experimental approach is thus proposed to evaluate the effective impact energies.