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Mohamed Taktak

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University of Zagreb

Uppsala University

University of East London

University of Leicester

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

Macquarie University

Universidade Federal do Rio Grande do Sul

Swansea University

Jesper Hoffmeyer

University of Copenhagen

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Papers by Mohamed Taktak

Comparing Simulation and Theory for Scattering Matrix

Lecture notes in mechanical engineering, 2024

Simulation of the Acoustic Fields and Directivities Radiated from a Set of Elementary Sources

Springer eBooks, Aug 22, 2021

Acoustic performance evaluation for ducts containing porous materials

Applied Acoustics, Apr 1, 2019

The study of the sound propagation in duct systems containing a porous material is important beca... more The study of the sound propagation in duct systems containing a porous material is important because they are used in many industrial applications. The acoustic behavior of this kind of ducts which are supposed two-port systems can be modeled by many matrices like the reflection, transmission, mobility, transfer and scattering matrices. In this work, Theoretical and experimental methods are used to evaluate the acoustic performance of duct systems containing one or two porous materials. To reach this goal, the Transmission coefficient was calculated by determining transfer and scattering matrices. The comparison between theoretical and experimental results shows a good agreement between results with some differences due to the no respect of the hypothesis of the rigidity of the duct. A parametric study allowed estimating the more influent parameters on the acoustic behavior of duct systems containing porous materials.

Investigations on Crack Propagation and Strain Energy Release Rate in Notched Woven-Ply Thermoplastic Laminates at High-Temperature

International Journal of Applied Mechanics, Sep 1, 2016

The strain energy release rate [Formula: see text] is of prime importance in composite materials ... more The strain energy release rate [Formula: see text] is of prime importance in composite materials fracture mechanics. In order to experimentally and numerically evaluate this parameter in the case of quasi-isotropic and angle-ply (AP) woven-ply thermoplastic (TP) laminates, single edge notched (SEN) specimens have been subjected to monotonic tensile loading at [Formula: see text] when the toughness and the viscous behavior of the (TP) matrix are exacerbated. From the simulation standpoint, a particular attention was paid to the type of meshing as well as its refinement in the vicinity of the crack tip where the triaxiality rate leads to significant stress concentrations. For this purpose, a linear spectral viscoelastic and a generalized Norton-type viscoplastic models have been used. A comparison between two types of meshing (radiant and concentric) has been conducted. Both types of meshing allow us to define crowns in order to represent the surface of the integration ring around the crack tip. These crowns are necessary to evaluate the strain energy release rate [Formula: see text] in opening mode using [Formula: see text]-integral computation. Both overstress and overstrain profiles near the crack tip were investigated and validated using theoretical stress fields derived from the linear elastic fracture mechanics (LEFM) framework and overstrain fields obtained from digital image correlation (DIC) to verify the model’s ability to provide accurate mechanical fields at singularity zones.

Uncertainty and sensitivity analysis of porous materials acoustic behavior

Applied Acoustics, 2019

In practice, the functioning errors of a system can be avoided by a good choice of its parameters... more In practice, the functioning errors of a system can be avoided by a good choice of its parameters since the design step. To reach this objective, uncertainty and sensitivity studies applied to a model describing the system can reveal the inputs parameters that cause the most significant variation of the model outputs. Thereby, necessary precautions can be taken to avoid the effect of the most influential parameters causing the faulty operation of the system. In this work, uncertainty and sensitivity analyzes are applied to a theoretical model predicting the acoustic behavior of a porous material synthesized by an agricultural waste based on sugar cane. The first analysis leads to the assessment propagation of errors through the model by using the Monte Carlo simulation. The second one consists on assigning to each model input a sensitivity index by two methods called Sobol and McKay.

Flexural Fatigue of Bio-Based Composites

Lecture notes in mechanical engineering, Nov 25, 2017

The paper presents an investigation of the mechanical fatigue behavior of a bio-based composite w... more The paper presents an investigation of the mechanical fatigue behavior of a bio-based composite with an interleaved natural viscoelastic layer. The material used is a unidirectional laminate with different orientations. It is composed of a GreenPoxy resin reinforced with long flax fibers. A viscoelastic layer made of natural rubber has been introduced at the middle layer of the laminate. Different configurations of unidirectional specimens were tested in static tests. The mechanical properties such as the characteristics at failure of the structures with and without natural rubber were determined and compared. The effect of the insertion of the viscoelastic layer in the studied composite on the stiffness, hysteresis loops and loss factors were investigated during cyclic fatigue tests. A comparison of the fatigue behavior of the composite with and without viscoelastic layer was made. The results show that the composite with an interleaved natural viscoelastic layer presents an interesting damping properties considering the high values of the loss factors obtained from cyclic fatigue tests.

Acoustic Liners Behavior Investigation Using the Multimodal Scattering Matrix

International Review of Aerospace Engineering, Dec 31, 2015

In this paper, the acoustic behavior of Helmholtz’s resonator type liner used in aeronautics appl... more In this paper, the acoustic behavior of Helmholtz’s resonator type liner used in aeronautics applications is presented. The aim of this work is to study how the liner properties can be modified by the mounting conditions on the wall of a cylindrical duct element. To achieve this objective the measured multi-port scattering matrix, power acoustic dissipations are compared with results performed by FEM assuming axi-symmetry and a uniform and locally reacting material which impedance is measured or resulting from a model. Results show that in plane wave conditions the agreement between experiment and theory is satisfying but that a large discrepancy occurs when higher order mode is incident on the liner element pointing out a modification of the acoustic properties of the lined wall.

Determination of J-R curves by load separation criterion in highly ductile TP-based composites under high temperature conditions

Composite Structures, Dec 1, 2017

Propriétés dynamiques d'un composite en fibres de lin avec une couche viscoélastique naturelle

HAL (Le Centre pour la Communication Scientifique Directe), Jun 28, 2017

L'utilisation des matériaux composites bio-sourcés ont connus un fort développement ces dernières... more L'utilisation des matériaux composites bio-sourcés ont connus un fort développement ces dernières années. En les comparant aux matériaux composites synthétiques conventionnels, ces nouveaux matériaux naturels présentent de nombreux avantages, parmi lesquels leur biodégradabilité, leur faible densité et leur module de traction et de flexion relativement élevé. Le but de cette étude est d'analyser les propriétés d'amortissement des composites en fibres de lin. Des essais vibratoires ont été réalisées durant les quels les fréquences naturelles et les amortissements modaux ont été évalués. Une autre partie de l'étude consiste à évaluer l'effet de l'insertion d'une couche viscoélastique (en caoutchouc naturel) sur le comportement dynamique de ces bio-composites. Les résultats montrent que l'insertion de cette couche a une influence significative sur le comportement en vibration, la rigidité en flexion et les facteurs d'amortissement du composite.

Characterization of the Mechanical and Vibration Behavior of Flax Composites with an Interleaved Natural Viscoelastic Layer

Applied condition monitoring, Sep 4, 2018

This study presents an analysis of the mechanical and vibration behavior of a flax fibre reinforc... more This study presents an analysis of the mechanical and vibration behavior of a flax fibre reinforced composites with and without an interleaved natural viscoelastic layer. Two types of elastic and viscoelastic cross ply laminates [02/902]s and [02/902/NR]s have been characterized experimentally using different mechanical and vibrational tests. The elastic laminate is composed of natural long flax fibre and greenpoxy resin while the viscoelastic laminate is composed of a natural viscoelastic layer and two elastic composites. First, both types of specimen composites were studied using uni-axial tensile tests under the same conditions. A comparison between the two composites behaviors has been realized. Then, Acoustic Emission (AE) has been often used for the identification and characterization of micro failure mechanisms and damage in laminates. Finally, experimental vibration analyses were carried out on the composites with and without an interleaved natural viscoelastic layer. Throughout a series of resonance vibration tests, the evolution of the Young modulus and the modal damping were evaluated. The effect of the viscoelastic layer on the mechanical and vibration behavior of the elastic composite has been investigated and analyzed. It has been shown that the viscoelastic layer improves with a significant way the modal properties of the flax fibre reinforced composite.

Effect of an Interleave Natural Viscoelastic Layer on the Dynamic Behaviour of a Bio-Based Composite

Advanced Composites Letters, Nov 1, 2017

The purpose of the present letter is to analyse the damping properties of a bio-based composite w... more The purpose of the present letter is to analyse the damping properties of a bio-based composite with flax fibre. Damping parameters were investigated using beam test specimens and an impulse technique. Through a series of resonance vibration tests, the natural frequencies and modal damping were evaluated. The second part of the work was to investigate the effect of an interleave viscoelastic layer made of natural rubber on the dynamic behaviour of the composite. A comparison of the different results was performed; it shows that the viscoelastic layer had a significant influence on vibration behaviour, bending stiffness and damping factors.

Experimental analysis of the linear and nonlinear vibration behavior of flax fibre reinforced composites with an interleaved natural viscoelastic layer

Composites Part B-engineering, Oct 1, 2018

An analysis of the linear and nonlinear vibration responses of composites with delaminations is p... more An analysis of the linear and nonlinear vibration responses of composites with delaminations is presented. The effect of delamination size on the linear and nonlinear vibration response is studied. The composite material used in this paper is a glass fibre reinforced plastic (GFRP) having delaminations at the plies interfaces. The experimental procedure consists in inducing the specimen on its resonance flexural modes with different excitation levels (amplitudes) for six bending modes and for each delamination length. The presence of the nonlinearity introduced by the delamination was clearly identified by the variation of natural frequencies for increasing excitation levels. Then, nonlinear elastic parameters for progressive delamination length were determined and discussed for the first six bending modes. The linear and the nonlinear elastic parameters were compared in their sensitive modes.

Numerical and Experimental Characterization of the Dynamic Properties of Flax Fiber Reinforced Composites

International Journal of Applied Mechanics, Jul 1, 2016

In this paper, the damping properties of flax fiber reinforced composites were investigated. Thro... more In this paper, the damping properties of flax fiber reinforced composites were investigated. Throughout a series of resonance vibration tests, the natural frequencies and the modal damping were evaluated. A numerical modelling was also produced by using a finite element model to determine the energies dissipated in each layer of the laminate structure in order to calculate the damping factors. The results obtained for the dynamic properties of flax fiber reinforced composites from experimental data and numerical analysis method show close agreement. The effect of fiber orientations on the damping behavior for this material was investigated. Another part of our work was to insert a thin viscoelastic layer within the flax fiber laminate. The interposition of this viscoelastic layer had a significant influence on the vibration behavior, bending stiffness and damping factors.

Characterization of the vibrational behaviour of flax fibre reinforced composites with an interleaved natural viscoelastic layer

Applied Acoustics, Dec 1, 2017

In this study, the vibration and damping performances of flax fibre reinforced composites with an... more In this study, the vibration and damping performances of flax fibre reinforced composites with an interleaved natural viscoelastic layer are investigated. The experimental analysis is studied using beam test specimens and an impulse technique in flexural vibration. Damping modeling is developed using finite element analysis which evaluates the different energies dissipated in the material directions of the layers. The results obtained show that this analysis corresponds closely to experimental results. Finally, a parametric study is carried out using finite element analysis, to investigate the effects of flax fibre directions, thickness and Young's modulus of the natural viscoelastic layer.

Finite element method for the stress analysis of isotropic cylindrical helical spring

European Journal of Mechanics - A/Solids, 2005

This paper presents an efficient two nodes finite element with six degrees of freedom per node, c... more This paper presents an efficient two nodes finite element with six degrees of freedom per node, capable to model the total behaviour of a helical spring. The formulation, which includes the shear deformation effects, is based on the assumed forces hybrid approach. The resultant forces approximation verifies exactly the resultant equilibrium equations. The developed model proves its accuracy compared with other elements. This element permits to get the distribution of different stresses along the spring and through the wire surface by only one element.

Computation of the scattering matrix of guided acoustical propagation by the Wave Finite Element approach

Applied Acoustics, 2016

Abstract This work aims to study the guided acoustical propagation. The Wave Finite Element metho... more Abstract This work aims to study the guided acoustical propagation. The Wave Finite Element method is applied rather than the classic Finite Element method. Finite Element libraries are used for an elementary portion modelling. The dynamic stiffness matrix is then calculated. Periodicity conditions lead to a simple eigenvalue problem and the wave basis can be extracted. The dynamic stiffness matrix of the coupling elements corresponding to the lined parts can be also calculated considering the acoustical impedance. The use of the coupling’s conditions provides the scattering matrix. Within the framework of this method, the dispersion curves, the evolution of the scattering coefficients and the forced response to pressure excitations for both single and coupled waveguides can be represented, and compared to the FE method. The WFE method, treated in literature, and its main interests are reviewed, while adding the impedance notion into the calculation of the scattering matrix.

Estimation of Dynamic System's Excitation Forces by the Independent Component Analysis

International Journal of Applied Mechanics, 2012

This paper deals with a numerical investigation for the estimation of dynamic system's excita... more This paper deals with a numerical investigation for the estimation of dynamic system's excitation sources using the independent component analysis (ICA). In fact, the ICA concept is an important technique of the blind source separation (BSS) method. In this case, only the dynamic responses of a given mechanical system are supposed to be known. Thus, the main difficulty of such problem resides in the existence of any information about the excitation forces. For this purpose, the ICA concept, which consists on optimizing a fourth-order statistical criterion, can be highlighted. Hence, a numerical procedure based on the signal sources independency in the ICA concept is developed. In this work, the analytical or the finite element (FE) dynamic responses are calculated and exploited in order to identify the excitation forces applied on discrete (mass-spring) and continuous (beam) systems. Then, estimated results obtained by the ICA concept are presented and compared to those achieved...

Optimization of the transmission loss of a multilayer panels using the genetic algorithm

ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik

An optimization method of the acoustic absorption of multilayer panels composed of porous, elasti... more An optimization method of the acoustic absorption of multilayer panels composed of porous, elastic, and viscoelastic materials is presented in this paper. The used objective functions consist on the maximizing of the sound Transmission Loss (TL) and the minimization of the mass of the configuration. For this, the genetic algorithm was used coupled with an analytical computation of transfer matrix of the studied panel. This study aimed to found the optimal values of the thicknesses of each layer with a total thickness which should not exceed 30 mm. The others parameters are keeping constant. The developed method was applied to a two‐layer panel. The obtained results are analyzed giving sources to choose between the studied configurations.

Experimental vibratory analysis of a rotating segmented wind turbine blade using common test equipment

Journal of the Brazilian Society of Mechanical Sciences and Engineering

An Improved Scattering Matrix Algorithm for Sound Propagation Inside Lined Ducts

Lecture notes in mechanical engineering, Aug 20, 2022

Comparing Simulation and Theory for Scattering Matrix

Lecture notes in mechanical engineering, 2024

Simulation of the Acoustic Fields and Directivities Radiated from a Set of Elementary Sources

Springer eBooks, Aug 22, 2021

Acoustic performance evaluation for ducts containing porous materials

Applied Acoustics, Apr 1, 2019

The study of the sound propagation in duct systems containing a porous material is important beca... more The study of the sound propagation in duct systems containing a porous material is important because they are used in many industrial applications. The acoustic behavior of this kind of ducts which are supposed two-port systems can be modeled by many matrices like the reflection, transmission, mobility, transfer and scattering matrices. In this work, Theoretical and experimental methods are used to evaluate the acoustic performance of duct systems containing one or two porous materials. To reach this goal, the Transmission coefficient was calculated by determining transfer and scattering matrices. The comparison between theoretical and experimental results shows a good agreement between results with some differences due to the no respect of the hypothesis of the rigidity of the duct. A parametric study allowed estimating the more influent parameters on the acoustic behavior of duct systems containing porous materials.

Investigations on Crack Propagation and Strain Energy Release Rate in Notched Woven-Ply Thermoplastic Laminates at High-Temperature

International Journal of Applied Mechanics, Sep 1, 2016

The strain energy release rate [Formula: see text] is of prime importance in composite materials ... more The strain energy release rate [Formula: see text] is of prime importance in composite materials fracture mechanics. In order to experimentally and numerically evaluate this parameter in the case of quasi-isotropic and angle-ply (AP) woven-ply thermoplastic (TP) laminates, single edge notched (SEN) specimens have been subjected to monotonic tensile loading at [Formula: see text] when the toughness and the viscous behavior of the (TP) matrix are exacerbated. From the simulation standpoint, a particular attention was paid to the type of meshing as well as its refinement in the vicinity of the crack tip where the triaxiality rate leads to significant stress concentrations. For this purpose, a linear spectral viscoelastic and a generalized Norton-type viscoplastic models have been used. A comparison between two types of meshing (radiant and concentric) has been conducted. Both types of meshing allow us to define crowns in order to represent the surface of the integration ring around the crack tip. These crowns are necessary to evaluate the strain energy release rate [Formula: see text] in opening mode using [Formula: see text]-integral computation. Both overstress and overstrain profiles near the crack tip were investigated and validated using theoretical stress fields derived from the linear elastic fracture mechanics (LEFM) framework and overstrain fields obtained from digital image correlation (DIC) to verify the model’s ability to provide accurate mechanical fields at singularity zones.

Uncertainty and sensitivity analysis of porous materials acoustic behavior

Applied Acoustics, 2019

In practice, the functioning errors of a system can be avoided by a good choice of its parameters... more In practice, the functioning errors of a system can be avoided by a good choice of its parameters since the design step. To reach this objective, uncertainty and sensitivity studies applied to a model describing the system can reveal the inputs parameters that cause the most significant variation of the model outputs. Thereby, necessary precautions can be taken to avoid the effect of the most influential parameters causing the faulty operation of the system. In this work, uncertainty and sensitivity analyzes are applied to a theoretical model predicting the acoustic behavior of a porous material synthesized by an agricultural waste based on sugar cane. The first analysis leads to the assessment propagation of errors through the model by using the Monte Carlo simulation. The second one consists on assigning to each model input a sensitivity index by two methods called Sobol and McKay.

Flexural Fatigue of Bio-Based Composites

Lecture notes in mechanical engineering, Nov 25, 2017

The paper presents an investigation of the mechanical fatigue behavior of a bio-based composite w... more The paper presents an investigation of the mechanical fatigue behavior of a bio-based composite with an interleaved natural viscoelastic layer. The material used is a unidirectional laminate with different orientations. It is composed of a GreenPoxy resin reinforced with long flax fibers. A viscoelastic layer made of natural rubber has been introduced at the middle layer of the laminate. Different configurations of unidirectional specimens were tested in static tests. The mechanical properties such as the characteristics at failure of the structures with and without natural rubber were determined and compared. The effect of the insertion of the viscoelastic layer in the studied composite on the stiffness, hysteresis loops and loss factors were investigated during cyclic fatigue tests. A comparison of the fatigue behavior of the composite with and without viscoelastic layer was made. The results show that the composite with an interleaved natural viscoelastic layer presents an interesting damping properties considering the high values of the loss factors obtained from cyclic fatigue tests.

Acoustic Liners Behavior Investigation Using the Multimodal Scattering Matrix

International Review of Aerospace Engineering, Dec 31, 2015

In this paper, the acoustic behavior of Helmholtz’s resonator type liner used in aeronautics appl... more In this paper, the acoustic behavior of Helmholtz’s resonator type liner used in aeronautics applications is presented. The aim of this work is to study how the liner properties can be modified by the mounting conditions on the wall of a cylindrical duct element. To achieve this objective the measured multi-port scattering matrix, power acoustic dissipations are compared with results performed by FEM assuming axi-symmetry and a uniform and locally reacting material which impedance is measured or resulting from a model. Results show that in plane wave conditions the agreement between experiment and theory is satisfying but that a large discrepancy occurs when higher order mode is incident on the liner element pointing out a modification of the acoustic properties of the lined wall.

Determination of J-R curves by load separation criterion in highly ductile TP-based composites under high temperature conditions

Composite Structures, Dec 1, 2017

Propriétés dynamiques d'un composite en fibres de lin avec une couche viscoélastique naturelle

HAL (Le Centre pour la Communication Scientifique Directe), Jun 28, 2017

L'utilisation des matériaux composites bio-sourcés ont connus un fort développement ces dernières... more L'utilisation des matériaux composites bio-sourcés ont connus un fort développement ces dernières années. En les comparant aux matériaux composites synthétiques conventionnels, ces nouveaux matériaux naturels présentent de nombreux avantages, parmi lesquels leur biodégradabilité, leur faible densité et leur module de traction et de flexion relativement élevé. Le but de cette étude est d'analyser les propriétés d'amortissement des composites en fibres de lin. Des essais vibratoires ont été réalisées durant les quels les fréquences naturelles et les amortissements modaux ont été évalués. Une autre partie de l'étude consiste à évaluer l'effet de l'insertion d'une couche viscoélastique (en caoutchouc naturel) sur le comportement dynamique de ces bio-composites. Les résultats montrent que l'insertion de cette couche a une influence significative sur le comportement en vibration, la rigidité en flexion et les facteurs d'amortissement du composite.

Characterization of the Mechanical and Vibration Behavior of Flax Composites with an Interleaved Natural Viscoelastic Layer

Applied condition monitoring, Sep 4, 2018

This study presents an analysis of the mechanical and vibration behavior of a flax fibre reinforc... more This study presents an analysis of the mechanical and vibration behavior of a flax fibre reinforced composites with and without an interleaved natural viscoelastic layer. Two types of elastic and viscoelastic cross ply laminates [02/902]s and [02/902/NR]s have been characterized experimentally using different mechanical and vibrational tests. The elastic laminate is composed of natural long flax fibre and greenpoxy resin while the viscoelastic laminate is composed of a natural viscoelastic layer and two elastic composites. First, both types of specimen composites were studied using uni-axial tensile tests under the same conditions. A comparison between the two composites behaviors has been realized. Then, Acoustic Emission (AE) has been often used for the identification and characterization of micro failure mechanisms and damage in laminates. Finally, experimental vibration analyses were carried out on the composites with and without an interleaved natural viscoelastic layer. Throughout a series of resonance vibration tests, the evolution of the Young modulus and the modal damping were evaluated. The effect of the viscoelastic layer on the mechanical and vibration behavior of the elastic composite has been investigated and analyzed. It has been shown that the viscoelastic layer improves with a significant way the modal properties of the flax fibre reinforced composite.

Effect of an Interleave Natural Viscoelastic Layer on the Dynamic Behaviour of a Bio-Based Composite

Advanced Composites Letters, Nov 1, 2017

The purpose of the present letter is to analyse the damping properties of a bio-based composite w... more The purpose of the present letter is to analyse the damping properties of a bio-based composite with flax fibre. Damping parameters were investigated using beam test specimens and an impulse technique. Through a series of resonance vibration tests, the natural frequencies and modal damping were evaluated. The second part of the work was to investigate the effect of an interleave viscoelastic layer made of natural rubber on the dynamic behaviour of the composite. A comparison of the different results was performed; it shows that the viscoelastic layer had a significant influence on vibration behaviour, bending stiffness and damping factors.

Experimental analysis of the linear and nonlinear vibration behavior of flax fibre reinforced composites with an interleaved natural viscoelastic layer

Composites Part B-engineering, Oct 1, 2018

An analysis of the linear and nonlinear vibration responses of composites with delaminations is p... more An analysis of the linear and nonlinear vibration responses of composites with delaminations is presented. The effect of delamination size on the linear and nonlinear vibration response is studied. The composite material used in this paper is a glass fibre reinforced plastic (GFRP) having delaminations at the plies interfaces. The experimental procedure consists in inducing the specimen on its resonance flexural modes with different excitation levels (amplitudes) for six bending modes and for each delamination length. The presence of the nonlinearity introduced by the delamination was clearly identified by the variation of natural frequencies for increasing excitation levels. Then, nonlinear elastic parameters for progressive delamination length were determined and discussed for the first six bending modes. The linear and the nonlinear elastic parameters were compared in their sensitive modes.

Numerical and Experimental Characterization of the Dynamic Properties of Flax Fiber Reinforced Composites

International Journal of Applied Mechanics, Jul 1, 2016

In this paper, the damping properties of flax fiber reinforced composites were investigated. Thro... more In this paper, the damping properties of flax fiber reinforced composites were investigated. Throughout a series of resonance vibration tests, the natural frequencies and the modal damping were evaluated. A numerical modelling was also produced by using a finite element model to determine the energies dissipated in each layer of the laminate structure in order to calculate the damping factors. The results obtained for the dynamic properties of flax fiber reinforced composites from experimental data and numerical analysis method show close agreement. The effect of fiber orientations on the damping behavior for this material was investigated. Another part of our work was to insert a thin viscoelastic layer within the flax fiber laminate. The interposition of this viscoelastic layer had a significant influence on the vibration behavior, bending stiffness and damping factors.

Characterization of the vibrational behaviour of flax fibre reinforced composites with an interleaved natural viscoelastic layer

Applied Acoustics, Dec 1, 2017

In this study, the vibration and damping performances of flax fibre reinforced composites with an... more In this study, the vibration and damping performances of flax fibre reinforced composites with an interleaved natural viscoelastic layer are investigated. The experimental analysis is studied using beam test specimens and an impulse technique in flexural vibration. Damping modeling is developed using finite element analysis which evaluates the different energies dissipated in the material directions of the layers. The results obtained show that this analysis corresponds closely to experimental results. Finally, a parametric study is carried out using finite element analysis, to investigate the effects of flax fibre directions, thickness and Young's modulus of the natural viscoelastic layer.

Finite element method for the stress analysis of isotropic cylindrical helical spring

European Journal of Mechanics - A/Solids, 2005

This paper presents an efficient two nodes finite element with six degrees of freedom per node, c... more This paper presents an efficient two nodes finite element with six degrees of freedom per node, capable to model the total behaviour of a helical spring. The formulation, which includes the shear deformation effects, is based on the assumed forces hybrid approach. The resultant forces approximation verifies exactly the resultant equilibrium equations. The developed model proves its accuracy compared with other elements. This element permits to get the distribution of different stresses along the spring and through the wire surface by only one element.

Computation of the scattering matrix of guided acoustical propagation by the Wave Finite Element approach

Applied Acoustics, 2016

Abstract This work aims to study the guided acoustical propagation. The Wave Finite Element metho... more Abstract This work aims to study the guided acoustical propagation. The Wave Finite Element method is applied rather than the classic Finite Element method. Finite Element libraries are used for an elementary portion modelling. The dynamic stiffness matrix is then calculated. Periodicity conditions lead to a simple eigenvalue problem and the wave basis can be extracted. The dynamic stiffness matrix of the coupling elements corresponding to the lined parts can be also calculated considering the acoustical impedance. The use of the coupling’s conditions provides the scattering matrix. Within the framework of this method, the dispersion curves, the evolution of the scattering coefficients and the forced response to pressure excitations for both single and coupled waveguides can be represented, and compared to the FE method. The WFE method, treated in literature, and its main interests are reviewed, while adding the impedance notion into the calculation of the scattering matrix.

Estimation of Dynamic System's Excitation Forces by the Independent Component Analysis

International Journal of Applied Mechanics, 2012

This paper deals with a numerical investigation for the estimation of dynamic system's excita... more This paper deals with a numerical investigation for the estimation of dynamic system's excitation sources using the independent component analysis (ICA). In fact, the ICA concept is an important technique of the blind source separation (BSS) method. In this case, only the dynamic responses of a given mechanical system are supposed to be known. Thus, the main difficulty of such problem resides in the existence of any information about the excitation forces. For this purpose, the ICA concept, which consists on optimizing a fourth-order statistical criterion, can be highlighted. Hence, a numerical procedure based on the signal sources independency in the ICA concept is developed. In this work, the analytical or the finite element (FE) dynamic responses are calculated and exploited in order to identify the excitation forces applied on discrete (mass-spring) and continuous (beam) systems. Then, estimated results obtained by the ICA concept are presented and compared to those achieved...

Optimization of the transmission loss of a multilayer panels using the genetic algorithm

ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik

An optimization method of the acoustic absorption of multilayer panels composed of porous, elasti... more An optimization method of the acoustic absorption of multilayer panels composed of porous, elastic, and viscoelastic materials is presented in this paper. The used objective functions consist on the maximizing of the sound Transmission Loss (TL) and the minimization of the mass of the configuration. For this, the genetic algorithm was used coupled with an analytical computation of transfer matrix of the studied panel. This study aimed to found the optimal values of the thicknesses of each layer with a total thickness which should not exceed 30 mm. The others parameters are keeping constant. The developed method was applied to a two‐layer panel. The obtained results are analyzed giving sources to choose between the studied configurations.

Experimental vibratory analysis of a rotating segmented wind turbine blade using common test equipment

Journal of the Brazilian Society of Mechanical Sciences and Engineering

An Improved Scattering Matrix Algorithm for Sound Propagation Inside Lined Ducts

Lecture notes in mechanical engineering, Aug 20, 2022