Papers by Mahrez AIT
Engineering Failure Analysis, 2022
Due to the harshness and unpredictability of the tidal site environment, the damage induced by an... more Due to the harshness and unpredictability of the tidal site environment, the damage induced by an accidental impact should be considered in the certification of composite cylindrical structures intended to be used in the design of the composite MJM tidal turbine concept. The first part of this paper deals with the effect of different failure criteria based on quadratic stress functions on the low-velocity impact response of thick filament wound glass/epoxy cylindrical structures. A user defined material model (VUMAT) applied to three-dimensional solid elements was implemented into the finite element software Abaqus-Explicit to explore the effect of failure criteria on the predicted dynamic response with intralaminar damage. The investigated failure criteria include the two-dimensional Hashin criteria presented by Hashin in 1973 and extended to the three dimensional case by including analytically the out-of-plane stress terms (criteria denoted "Hashin 3D"), the three-dimensional Hashin criteria described by Hashin in 1980 (criteria denoted "Hashin 3D 1980"), the Puck matrix transverse criterion coupled to Hashin criteria (criteria denoted "Hashin-Puck") and Chang-Chang criteria (criteria denoted "Chang & Chang 1987"). The intralaminar damage model includes damage onset based on quadratic failure criteria, damage evolution, and element deletion from the solid mesh. FEA analyses are carried out with different low-level impact energies. The numerical results show different impact responses as well as the damage characteristics, particularly the matrix cracking through the thickness. In the second part, the bilinear cohesive zone model (CZM) is employed for modelling the interlaminar damage. The combination of the intralaminar damage model with the interlaminar model is applied using an uncoupled methodology. By comparison with the experimental force-time curves, interface properties used in the cohesive model have been estimated numerically using a reverse methodology and a baseline FEA model. The modelling approach has proven to be capable of reproducing experimental results with good accuracy. The modelling outcomes and predicted damage are therefore intended to be applied in the design loop and development of the MJM tidal turbine prototype, where thick filament wound glass/epoxy cylinders are subjected to low-velocity stones impact.
A Progressive Damage Modelling of Glass/Epoxy Cylindrical Structure Subjected to Low-Velocity Impact, 2021
Due to the harshness and unpredictability of the tidal site environment, the damage induced by an... more Due to the harshness and unpredictability of the tidal site environment, the damage induced by an accidental impact should be considered in the certification of composite cylindrical structures intended to be used in the design of the composite MJM tidal turbine concept. The first part of this paper deals with the effect of different failure criteria based on quadratic stress functions on the low-velocity impact response of thick filament wound glass/epoxy cylindrical structures. A userdefined material model (VUMAT) applied to three-dimensional solid elements was implemented into the finite element software Abaqus-Explicit to explore the effect of failure criteria on the predicted dynamic response with intralaminar damage. The investigated failure criteria include the two-dimensional Hashin criteria presented by Hashin in 1973 and extended to the threedimensional case by including analytically the out-of-plane stress terms (criteria denoted "Hashin 3D"), the three-dimensional Hashin criteria described by Hashin in 1980 (criteria denoted "Hashin 3D 1980"), the Puck matrix transverse criterion coupled to Hashin criteria (criteria denoted "Hashin-Puck") and Chang-Chang criteria (criteria denoted "Chang & Chang 1987"). The intralaminar damage model includes damage onset based on quadratic failure criteria, damage evolution, and element deletion from the solid mesh. FEA analyses are carried out with different low-level impact energies. The numerical results show different impact responses as well as the damage characteristics particularly the matrix cracking through the thickness. In the second part the bilinear cohesive zone model (CZM) is employed for modelling the interlaminar damage. The combination of the intralaminar damage model with the interlaminar model is applied using an uncoupled methodology. By comparison with the experimental force-time curves, interface properties used in the cohesive model have been estimated numerically using a reverse methodology and a baseline FEA model. The modelling approach has proven to be capable of reproducing experimental results with good accuracy. The modelling outcomes and predicted damage are therefore intended to be applied in the design loop and development of the MJM tidal turbine prototype where thick filament wound glass/epoxy cylinders are subjected to low-velocity stones impact.
A propeller in-house panel method code coupled with the blade element momentum theory (BEM) was u... more A propeller in-house panel method code coupled with the blade element momentum theory (BEM) was used to design a bare tidal turbine which reaches 88% of the Betz limit. The addition of a duct at the same overall cross section area has been investigated. The numerical results show that the ducted turbine’s power coefficient, which was computed using the overall cross section area, can be slightly increased if a camber duct profile with a flare angle is used. The hydrodynamic pressure obtained with the panel method code was then implemented as boundary conditions into the FE model in order to compute the static mechanical behavior of the composite duct. However several iterations of material distribution have been performed to satisfy two main criteria which are the damage initiation 24 ème Congrès Français de Mécanique Brest, 26 au 30 Août 2019 according to Hashin criteria and the maximum deflexion at the exit of the duct. This approach leads to introduce the ducted configuration pre...
Understanding of damage processes lead to improve safety and efficiency of composite structures.
Congrès Français de Mécanique Brest, 2019
The concept of underwater turbine, called tidal current turbine, designates the device which allo... more The concept of underwater turbine, called tidal current turbine, designates the device which allows the conversion of kinetic energy produced by marine currents into electric energy. This study shows that the world of marine propellers presents an interesting avenue of research with regard to the hydrodynamic behaviour of tidal current turbines. As a marine propeller has to be adapted to a specific ship, a tidal current turbine has to be adapted to a specific site [1]. We chose the most promising site on the French coasts, the race of Alderney. The main numerical tool is a propeller code based on the potential flow model. Putting aside the structure constraints, the design of tidal turbine is restricted by the hydrodynamic efficiency which means that flow separation and cavitation occurrence have to be avoided. An optimization procedure has allowed us to obtain a bare turbine geometry presenting a power coefficient (Cp) reaching 88% of the Betz (see (a)) and avoiding cavitation (see
Numerical Prediction of the Impact Behaviour of Composite Ducted Tidal Turbine
This work presents a numerical study of the impact behaviour of an all composite ducted tidal tur... more This work presents a numerical study of the impact behaviour of an all composite ducted tidal turbine. The numerical analysis has been performed by means of advanced numerical models implemented into Abaqus/Explicit. The modelling procedure in term of intralaminar damage model was implemented using the VUMAT subroutine which has been validated through comparison with experimental data available. A submodeling approach has been used to reduce significantly the computational time. The main objective of the numerical approach presented in this study is to propose a structural design methodology leading to improve the design efficiency and reduce the certifications cost of ducted tidal turbine, keeping in mind a commercial scalability of the MJM concept (Mahrez-Mostapha &Jean-Marc design). The proposed approach reveals some interesting points concerning the severity of the impact damage and the safety of the duct.
Numerical Investigation of the Damage in Composite Materials Under Dynamic Loads Using a Combination of Intralaminaire and Interlaminaire Model
Numerical finite element method using solid elements discretisation is increasingly used to simul... more Numerical finite element method using solid elements discretisation is increasingly used to simulate the impact behaviour of composite materials. In order to describe the intralaminar damage of composite materials, a three dimensional damage model is investigated. The purpose of this work is to explore the effect of the failure criteria on the dynamic failure properties of carbone fibre composite laminate. The intralaminar damage model is performed with different failure criteria including the two-dimensional Hashin criteria extended to the three-dimensional case and the three-dimensional Hashin criteria for the fibres coupled with the Puck criteria for the matrix. The two criteria were than incorporated in a VUMAT subroutine implemented in the explicit finite element code Abaqus. Furthermore, the delamination is simulated by the bilinear cohesive zone model (CZM) available in the finite element code Abaqus. To validate the material model implemented in the VUMAT subroutine and the effect of its association with the CZM, the numerical impact computations performed for various incident velocities were compared to the experimental measurements available in the literature. The results show that the impact response in term of residual velocity presents some difference due essentially to the effect of the criteria used in the intralaminar model. The Hashin criteria for the fibres associated with the Puck criteria for the matrix presents good agreement with the experimental data. The association of the intralaminar model with the CZM leads to a slightly larger value of the residual velocity. This research work outlines the importance of the use of appropriate failure criteria at high velocity impact analysis.
To convert the kinetic energy of marine current into electricity, the most sensible generator is ... more To convert the kinetic energy of marine current into electricity, the most sensible generator is a horizontal axis turbine. The know-how and the tools used for marine propulsion devices find a new range of applications in this field. An academic panel method code developed for the design of bare and ducted marine propellers was applied to design a marine current turbine. The turbine dimension and the tidal current velocity have been taken to fit the conditions in the Race of Alderney. The wing section theory and the optimum rotor theory based on the blade element momentum were used to obtain the design condition and a first geometry approaching the Betz limit for a bare rotor. The panel method was then used to verify the power coefficient obtained in the presence of the 3D effects and if the cavitation constraints are respected. Subsequently, the same panel code was used to verify if the addition of a duct could improve the power output per unit surface.
VI International Conference on Computational Methods in Marine Engineering. Marine 2015, Rome, It... more VI International Conference on Computational Methods in Marine Engineering. Marine 2015, Rome, Italy.
DESIGN OF COMPOSITE DUCTED HORIZONTAL AXIS TIDAL TURBINE
The marine current turbine is the mechanical device that captures the kinetic energy of marine cu... more The marine current turbine is the mechanical device that captures the kinetic energy of marine current to generate electrical power. A panel method program coupled with the blade element momentum theory (BEM) was used to design a bare tidal turbine which reaches 88% of the Betz limit. The addition of a duct for a same overall cross section area has been investigated. The numerical results show that the ducted turbine’s power coefficient, which was computed using the overall cross section area, can be slightly increased if a camber duct profile with a flare angle is used. The hydrodynamic pressure obtained with the panel method code were then implemented as boundary conditions to a finite element analysis (FEA) in order to compute the mechanical behavior, stress distribution and deflection of the duct in composite material. The Hashin criterion was used for damage prediction.
The marine current turbine is the mechanical device that captures the kinetic energy of marine cu... more The marine current turbine is the mechanical device that captures the kinetic energy of marine current to generate electrical power. This paper presents the application of an academic panel method code based on potential flow theory for the analysis of marine current turbines and the proposition of full scale bare and ducted design. The aim of this work is also to analyze the effect of the addition of a duct at the same overall section with bare turbine on the hydrodynamic performance. The numerical results show that the ducted turbine’s power coefficient, computed on the overall cross section, can be slightly increased through the use of a camber duct profile.
Thesis Chapters by Mahrez AIT
Study of Composites Ducts for Optimal Design of an Horizontal Axis Tidal Turbine
Teaching Documents by Mahrez AIT
Conference Presentations by Mahrez AIT
There are many areas of Europe in which extreme tidal currents are observed.
This work presents a numerical study of the impact behaviour of an all composite ducted tidal tur... more This work presents a numerical study of the impact behaviour of an all composite ducted tidal turbine. The numerical analysis has been performed by means of advanced numerical models implemented into Abaqus/Explicit. The modelling procedure in term of intralaminar damage model was implemented using the VUMAT subroutine which has been validated through comparison with experimental data. A submodeling approach has been used to reduce significantly the computational time. The main objective of the numerical approach presented in this study is to propose a structural design methodology leading to improve the design efficiency and reduce the certifications cost of ducted tidal turbine, keeping in mind a commercial scalability of the MJM concept (Mahrez-Mostapha &Jean-Marc design). The proposed approach reveals some interesting points concerning the severity of the impact damage and the safety of the duct. The results performed in this study concern only the degradation of the zone in contact with the impactor and the region in front of it but the procedure could be applied to other zone of the duct regardless of the impact scenario.
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Papers by Mahrez AIT
Thesis Chapters by Mahrez AIT
Teaching Documents by Mahrez AIT
Conference Presentations by Mahrez AIT