Sofiane Guessasma | Institut National de la Recherche Agronomique (original) (raw)
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Papers by Sofiane Guessasma
Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfe... more Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfer at interface is a key limiting factor for better mechanical performance. Finite element computation provides quantification of load transfer. Exact topography of spikelet is needed to proper evaluation of mechanical performance. Limited benefits of carbon nanotubes but prime role of spikelet chemical treatment. a b s t r a c t Date palm residues capabilities in civil engineering are evaluated by combining numerical and experimental approaches. Date palm spikelet originated from Elghers variety is added to mortar as a raw material or after chemical modification. Evaluation of reinforcement effect is performed using mechanical testing. Finite element modelling is considered to predict the interfacial behaviour and mechanical performance under various structural and mechanical hypotheses. Experimental results show limited effect of untreated spikelet on mortar performance for volume reinforcement of 1%. Larger contents result in severe degradation of mechanical performance compared to reference mortar. The addition of carbon nanotubes improves slightly the performance. Chemical treatment using both NaOH and CaO results in reinforced effect of spikelet. Numerical predictions show limited load transfer across the matrix/ untreated spikelet interface and large interface stiffness for those formulations including small spikelet, CNT and chemical treatment.
Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features... more Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features of weld lines in a short glass fiber reinforced polymer. The main originality of this work is related to the evaluation of local structural and mechanical characteristics in zones
of unmastered heterogeneities. Complete and incomplete injection molded plates are considered to investigate weld lines with and without process-induced porosity. Using a helical scanning trajectory, the full 3D microstructure is obtained at centimetric scale to cover a large zone including first contact between colliding fronts at a voxel size of 3 μm. Microstructure
analyses show that weld line area is ill-ordered at the fiber and structure length scales. Near the first contact point, fiber orientations show the signature of vortexes, which mark the presence of repulsive forces. The presence of micrometric porosity is only confirmed in incomplete plates. μ-CT images are used as inputs to
create a full-scale finite element model for assessing strain localization. Predicted principal strains are compared to digital image correlation measurements performed during uniaxial tensile tests.
Full-scale modeling combined to 3D high-resolution imaging proves high potential to correlate local fiber heterogeneities with strain localization effects
– Three-dimensional printing offers varied possibilities of design that can be bridged to optimis... more – Three-dimensional printing offers varied possibilities of design that can be bridged to optimisation tools. In this review paper, a critical opinion on optimal design is delivered to show limits, benefits and ways of improvement in additive manufacturing. This review emphasises on design constrains related to additive manufacturing and differences that may appear between virtual and real design. These differences are explored based on 3D imaging techniques that are intended to show defect related processing. Guidelines of safe use of the term ''optimal design'' are derived based on 3D structural information.
Our concern is to reveal the extent of structural imperfections of Additive Manufacturing (AM) by... more Our concern is to reveal the extent of structural imperfections of Additive Manufacturing (AM) by considering 3D imaging technique based on X-ray micro-tomography. Blocks of Acrylonitrile Butadiene Styrene (ABS) polymer are processed using Fused Deposition Modelling (FDM) with different printing orienta-tions. Image analysis is applied to the stacks of 3D printed blocks to quantify structural attributes such as porosity content and connectivity. The results show that pore connectivity represents the most important structural characteristic of FDM. The adopted commercial solution is able to produce acceptable porosity contents below 6% regardless of the printing orientation. Finite element results indicate the presence of expected transverse symmetry. The examination of the extent of such anisotropy is in well agreement with the observed structural imperfections mainly the porosity content. However, these predictions do not match the wide variations in mechanical performance described in the literature. The finite element analysis guides the next research step towards quantification of the imperfect bonding nature between filaments in FDM.
Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfe... more Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfer at interface is a key limiting factor for better mechanical performance. Finite element computation provides quantification of load transfer. Exact topography of spikelet is needed to proper evaluation of mechanical performance. Limited benefits of carbon nanotubes but prime role of spikelet chemical treatment. a b s t r a c t Date palm residues capabilities in civil engineering are evaluated by combining numerical and experimental approaches. Date palm spikelet originated from Elghers variety is added to mortar as a raw material or after chemical modification. Evaluation of reinforcement effect is performed using mechanical testing. Finite element modelling is considered to predict the interfacial behaviour and mechanical performance under various structural and mechanical hypotheses. Experimental results show limited effect of untreated spikelet on mortar performance for volume reinforcement of 1%. Larger contents result in severe degradation of mechanical performance compared to reference mortar. The addition of carbon nanotubes improves slightly the performance. Chemical treatment using both NaOH and CaO results in reinforced effect of spikelet. Numerical predictions show limited load transfer across the matrix/ untreated spikelet interface and large interface stiffness for those formulations including small spikelet, CNT and chemical treatment.
Materials Chemistry and Physics, 2005
The paper studies the effect of high-velocity oxy-fuel thermal spraying parameters, in particular... more The paper studies the effect of high-velocity oxy-fuel thermal spraying parameters, in particular spray distance and oxygen flow rate, on coating porosity and magnetic properties of FeSi and FeSiB deposits using the artificial neural network methodology. The magnetic properties correlated to coating porosity were obtained using an optimized network structure. The predicted results permitted to point out the role of
We report a new approach to measure orthotropic properties of short glass fibre reinforced thermo... more We report a new approach to measure orthotropic properties of short glass fibre reinforced thermoplastics at the macroscopic scale taking into account all microstructural details. 3D imaging technique based
on X-ray micro-tomography is used to assess fibrous architecture of an injected part at different positions
characterised by different fibre flow histories. Finite element computation is used as a multiscale process,
firstly by computing orthotropic parameters at a micro-scale for hundreds of bi-phasic 3D domains composing the macrostructure of the composite at all studied positions. Results are implemented in a second
finite element computation as a collection of orthotropic material models composing the heterogeneous
structure of the composite
Journal of Food Engineering, 2010
Food Research International, 2013
ABSTRACT We studied the masticatory behaviour of five commercial brittle cereal foods, with diffe... more ABSTRACT We studied the masticatory behaviour of five commercial brittle cereal foods, with different formulations, shapes and mechanical properties, chewed by an individual. The investigation of oral behaviour consisted in a simultaneous recording of jaw kinematics and muscle activity by electromyography (EMG) and we also determined the food size distribution at the swallowing point by image analysis. Similar behaviour was found for the evolution of all criteria, and especially the predominance of compression, which could be attributed to the brittle behaviour of the foods. The amplitude of the jaw motion decreased with the number of chewing cycles, or sequence duration, whereas the maximum mastication force led to the larger fragments of cereal foods when bolus was close to the swallowing point. Despite similar texture, mechanical properties, assessed by Kramer shear cell, influenced mastication work and bolus homogeneity.
Engineering Fracture Mechanics, 2011
Composites Science and Technology, 2011
Advanced Materials Research, 2012
ABSTRACT The mechanical properties and microstructure of modified mortar and concrete using Carbo... more ABSTRACT The mechanical properties and microstructure of modified mortar and concrete using Carbon NanoTubes (CNT) are experimentally studied at 7, 14, 28 and 90 curing days. Part of the formulation, CNT are dispersed in a liquid solution. Different concentrations ranging from 0.01% to 0.06% and 0.003% up to 0.01% are used for mortar and concrete, respectively. Mechanical testing of the modified materials reveals that maximum compressive strength is obtained for CNT concentrations close to 0.01%wt and 0.003%wt for mortar and concrete, respectively. The microstructural characterisation of the modified materials suggests that CNT act as bridges between pores and cracks leading to a reduction in porosity and in turn an increase of compressive strength.
In this work, we investigate the effect of hemp fibre and shive addition on modified mortars micr... more In this work, we investigate the effect of hemp fibre and shive addition on modified mortars microstructure and
mechanical performance. The mortar formulation is adjusted with different percentages and lengths of either
hemp fibres or shives. Workability of fresh modified mortars is carried out using two main techniques including
maniabilimeter and flow table experiments. Microstructural effects are revealed using X-ray μ-tomography
where the pore content and 3D spatial arrangement and content of hemp are all investigated. Mechanical
performance is derived from bending and compression testing at different curing times. Results show the
potential of using natural fibres as substitutes leading, in this study, to improvement of mechanical strength
but deterioration of stiffness. Superior mechanical performance with compression full strengths as large as
66 MPa is achieved using high-energy ball milling process of fly ashes that are added to unmodified mortar.
Results show also that optimal formulations need to involve both hemp fillers and milled fly ashes. These
formulations reveal superior mechanical performance compared to all tested conditions after only 7 curing days.
In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Ga... more In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Gas
welding (TIG) problem combining an experimental and a three-dimensional simulation approaches.
Optimal conditions are used to weld stainless steel (304L) sheets in butt configuration. Both instrumental
monitoring and metallographic investigation of the welded material are carried out. The modelling of the
heat source is performed by a mobile Gaussian surface source exhibiting a bi-elliptical shape. This source
is implemented in a three-dimensional finite element model to compute heat flux and temperature
fields. The comparison between the experimental and numerical thermal cycles shows a fair agreement.
Predicted temperature fields and heat flux distributions are discussed. Conversion of isotherms into
microstructural information shows that the size of the fusion zone is four times smaller than the heat
affected zone dimension. The metallographic analysis confirms the expected microstructural evolutions
but highlights differences between observed and predicted extents of the heat affected zone.
Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfe... more Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfer at interface is a key limiting factor for better mechanical performance. Finite element computation provides quantification of load transfer. Exact topography of spikelet is needed to proper evaluation of mechanical performance. Limited benefits of carbon nanotubes but prime role of spikelet chemical treatment. a b s t r a c t Date palm residues capabilities in civil engineering are evaluated by combining numerical and experimental approaches. Date palm spikelet originated from Elghers variety is added to mortar as a raw material or after chemical modification. Evaluation of reinforcement effect is performed using mechanical testing. Finite element modelling is considered to predict the interfacial behaviour and mechanical performance under various structural and mechanical hypotheses. Experimental results show limited effect of untreated spikelet on mortar performance for volume reinforcement of 1%. Larger contents result in severe degradation of mechanical performance compared to reference mortar. The addition of carbon nanotubes improves slightly the performance. Chemical treatment using both NaOH and CaO results in reinforced effect of spikelet. Numerical predictions show limited load transfer across the matrix/ untreated spikelet interface and large interface stiffness for those formulations including small spikelet, CNT and chemical treatment.
Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features... more Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features of weld lines in a short glass fiber reinforced polymer. The main originality of this work is related to the evaluation of local structural and mechanical characteristics in zones
of unmastered heterogeneities. Complete and incomplete injection molded plates are considered to investigate weld lines with and without process-induced porosity. Using a helical scanning trajectory, the full 3D microstructure is obtained at centimetric scale to cover a large zone including first contact between colliding fronts at a voxel size of 3 μm. Microstructure
analyses show that weld line area is ill-ordered at the fiber and structure length scales. Near the first contact point, fiber orientations show the signature of vortexes, which mark the presence of repulsive forces. The presence of micrometric porosity is only confirmed in incomplete plates. μ-CT images are used as inputs to
create a full-scale finite element model for assessing strain localization. Predicted principal strains are compared to digital image correlation measurements performed during uniaxial tensile tests.
Full-scale modeling combined to 3D high-resolution imaging proves high potential to correlate local fiber heterogeneities with strain localization effects
– Three-dimensional printing offers varied possibilities of design that can be bridged to optimis... more – Three-dimensional printing offers varied possibilities of design that can be bridged to optimisation tools. In this review paper, a critical opinion on optimal design is delivered to show limits, benefits and ways of improvement in additive manufacturing. This review emphasises on design constrains related to additive manufacturing and differences that may appear between virtual and real design. These differences are explored based on 3D imaging techniques that are intended to show defect related processing. Guidelines of safe use of the term ''optimal design'' are derived based on 3D structural information.
Our concern is to reveal the extent of structural imperfections of Additive Manufacturing (AM) by... more Our concern is to reveal the extent of structural imperfections of Additive Manufacturing (AM) by considering 3D imaging technique based on X-ray micro-tomography. Blocks of Acrylonitrile Butadiene Styrene (ABS) polymer are processed using Fused Deposition Modelling (FDM) with different printing orienta-tions. Image analysis is applied to the stacks of 3D printed blocks to quantify structural attributes such as porosity content and connectivity. The results show that pore connectivity represents the most important structural characteristic of FDM. The adopted commercial solution is able to produce acceptable porosity contents below 6% regardless of the printing orientation. Finite element results indicate the presence of expected transverse symmetry. The examination of the extent of such anisotropy is in well agreement with the observed structural imperfections mainly the porosity content. However, these predictions do not match the wide variations in mechanical performance described in the literature. The finite element analysis guides the next research step towards quantification of the imperfect bonding nature between filaments in FDM.
Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfe... more Acceptable performance of modified mortars with moderate date palm spikelet content. Load transfer at interface is a key limiting factor for better mechanical performance. Finite element computation provides quantification of load transfer. Exact topography of spikelet is needed to proper evaluation of mechanical performance. Limited benefits of carbon nanotubes but prime role of spikelet chemical treatment. a b s t r a c t Date palm residues capabilities in civil engineering are evaluated by combining numerical and experimental approaches. Date palm spikelet originated from Elghers variety is added to mortar as a raw material or after chemical modification. Evaluation of reinforcement effect is performed using mechanical testing. Finite element modelling is considered to predict the interfacial behaviour and mechanical performance under various structural and mechanical hypotheses. Experimental results show limited effect of untreated spikelet on mortar performance for volume reinforcement of 1%. Larger contents result in severe degradation of mechanical performance compared to reference mortar. The addition of carbon nanotubes improves slightly the performance. Chemical treatment using both NaOH and CaO results in reinforced effect of spikelet. Numerical predictions show limited load transfer across the matrix/ untreated spikelet interface and large interface stiffness for those formulations including small spikelet, CNT and chemical treatment.
Materials Chemistry and Physics, 2005
The paper studies the effect of high-velocity oxy-fuel thermal spraying parameters, in particular... more The paper studies the effect of high-velocity oxy-fuel thermal spraying parameters, in particular spray distance and oxygen flow rate, on coating porosity and magnetic properties of FeSi and FeSiB deposits using the artificial neural network methodology. The magnetic properties correlated to coating porosity were obtained using an optimized network structure. The predicted results permitted to point out the role of
We report a new approach to measure orthotropic properties of short glass fibre reinforced thermo... more We report a new approach to measure orthotropic properties of short glass fibre reinforced thermoplastics at the macroscopic scale taking into account all microstructural details. 3D imaging technique based
on X-ray micro-tomography is used to assess fibrous architecture of an injected part at different positions
characterised by different fibre flow histories. Finite element computation is used as a multiscale process,
firstly by computing orthotropic parameters at a micro-scale for hundreds of bi-phasic 3D domains composing the macrostructure of the composite at all studied positions. Results are implemented in a second
finite element computation as a collection of orthotropic material models composing the heterogeneous
structure of the composite
Journal of Food Engineering, 2010
Food Research International, 2013
ABSTRACT We studied the masticatory behaviour of five commercial brittle cereal foods, with diffe... more ABSTRACT We studied the masticatory behaviour of five commercial brittle cereal foods, with different formulations, shapes and mechanical properties, chewed by an individual. The investigation of oral behaviour consisted in a simultaneous recording of jaw kinematics and muscle activity by electromyography (EMG) and we also determined the food size distribution at the swallowing point by image analysis. Similar behaviour was found for the evolution of all criteria, and especially the predominance of compression, which could be attributed to the brittle behaviour of the foods. The amplitude of the jaw motion decreased with the number of chewing cycles, or sequence duration, whereas the maximum mastication force led to the larger fragments of cereal foods when bolus was close to the swallowing point. Despite similar texture, mechanical properties, assessed by Kramer shear cell, influenced mastication work and bolus homogeneity.
Engineering Fracture Mechanics, 2011
Composites Science and Technology, 2011
Advanced Materials Research, 2012
ABSTRACT The mechanical properties and microstructure of modified mortar and concrete using Carbo... more ABSTRACT The mechanical properties and microstructure of modified mortar and concrete using Carbon NanoTubes (CNT) are experimentally studied at 7, 14, 28 and 90 curing days. Part of the formulation, CNT are dispersed in a liquid solution. Different concentrations ranging from 0.01% to 0.06% and 0.003% up to 0.01% are used for mortar and concrete, respectively. Mechanical testing of the modified materials reveals that maximum compressive strength is obtained for CNT concentrations close to 0.01%wt and 0.003%wt for mortar and concrete, respectively. The microstructural characterisation of the modified materials suggests that CNT act as bridges between pores and cracks leading to a reduction in porosity and in turn an increase of compressive strength.
In this work, we investigate the effect of hemp fibre and shive addition on modified mortars micr... more In this work, we investigate the effect of hemp fibre and shive addition on modified mortars microstructure and
mechanical performance. The mortar formulation is adjusted with different percentages and lengths of either
hemp fibres or shives. Workability of fresh modified mortars is carried out using two main techniques including
maniabilimeter and flow table experiments. Microstructural effects are revealed using X-ray μ-tomography
where the pore content and 3D spatial arrangement and content of hemp are all investigated. Mechanical
performance is derived from bending and compression testing at different curing times. Results show the
potential of using natural fibres as substitutes leading, in this study, to improvement of mechanical strength
but deterioration of stiffness. Superior mechanical performance with compression full strengths as large as
66 MPa is achieved using high-energy ball milling process of fly ashes that are added to unmodified mortar.
Results show also that optimal formulations need to involve both hemp fillers and milled fly ashes. These
formulations reveal superior mechanical performance compared to all tested conditions after only 7 curing days.
In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Ga... more In this study, we focus on the determination of the heat transfer properties in Tungsten-Inert-Gas
welding (TIG) problem combining an experimental and a three-dimensional simulation approaches.
Optimal conditions are used to weld stainless steel (304L) sheets in butt configuration. Both instrumental
monitoring and metallographic investigation of the welded material are carried out. The modelling of the
heat source is performed by a mobile Gaussian surface source exhibiting a bi-elliptical shape. This source
is implemented in a three-dimensional finite element model to compute heat flux and temperature
fields. The comparison between the experimental and numerical thermal cycles shows a fair agreement.
Predicted temperature fields and heat flux distributions are discussed. Conversion of isotherms into
microstructural information shows that the size of the fusion zone is four times smaller than the heat
affected zone dimension. The metallographic analysis confirms the expected microstructural evolutions
but highlights differences between observed and predicted extents of the heat affected zone.