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The present work deals with the study of the damping capacity of b-metastable Ti–(24–26) Nb alloys. In this work, several methods have been used to characterize this damping. The impact tests were carried out using two test benches: high-speed impacts were carried out using a vertical firing pressure gun and low-velocity impacts were studied with a bullet drop test. In addition, an original approach of a dynamic mechanical analysis (DMA) is proposed in order to obtain more in-depth understanding of the relationship between microstructure, deformation mechanisms, and damping capacity. The specimens are studied at different microstructure states: single β, dual-phase β + α″, and martensitic phase. A correlation is established between the evolution of the damping factor as function of the applied strain and the occurrence of the corresponding deformation mechanisms. The stress-in-duced martensite mechanism contributes to the improvement of the damping factor.The highest damping capacity is observed for the dual-phase specimen (β + α″). It is shown that the contribution of both the reorientation martensite variants and stress-induced martensitic transformation lead to a damping capacity higher than a single deformation mechanism one.

The present study aims at developing a new Shape Memory Alloy (SMA) autonomous torsion actuator that exhibits Two-Way reversible memory effect Assisted by SuperElasticity. The developed actuator noted hereafter TWASE is composed by a single NiTi compact component having two distinct SMAs parts on one single axis: a SuperElastic part (length L SE ) and a Shape Memory Effect part (length L SME ). The proposed design ensures twisting the actuator when heated, this activates then the superelastic part putting back the actuator into its original shape as a result of a decrease in temperature. Hence, the actuator moves and goes back to the initial position autonomously (self-reversible). It has been established that the actuation efficiency is strongly dependent on the length ratio (k SME ) of the SME part with respect to the total length of the torsion actuator. Experimentally, an actuator with a length ratio of 3/5 has been developed and tested. The actuator’s axis is subjected to a specific heat treatment for obtaining a SMA wire with two distinct zones. A FE analysis using a proper UMAT subroutine into Abaqus software has been performed to predict the kinematics and the thermomechanical response of the actuator and finally to optimize it accordingly. The developed computational model captures the actuator responses and the subsequent optimizations are carried out leading to the improved specifications, which are confirmed experimentally. The experimental validation has been carried out using a prototype set-up of a torsion bench built by 3D printing. The actuation response of TWASE is numerically analyzed for several length ratio configurations. Based on the numerical simulations, the performance of the actuator has been optimized in terms of rotation angle and length ratio. The best ratio of shape memory to superelastic parts in the actuator has been predicted to 1/4 for obtaining the expected two-way reversible memory effect (TWASE).

To use wood as a structural element in vehicles, it is necessary to measure its physical properties locally in order to deduce its mechanical behaviour. Density is one of the characteristics that influences the most the mechanical properties, and it is on its measurement that this study will focus, using a technology that is still little studied for this application: terahertz radiation. Measurements using a Terahertz radar on samples will allow to obtain maps of the optical index and absorption coefficient, these values being linked to the density of the samples. The present study will consider wood species with various global densities and exhibiting local density pattern (growth rings) to assess the prediction of the density.

Among various industries, the construction sector has one of the greatest impacts on the environment. Minimizing the resource use and the waste outputs in this sector could be fulfilled by applying circular economy (CE) strategies. Although research on CE in the construction sector has increased in recent years, there have not been remarkable adjustments by applying these strategies to the construction industry. The purpose of this study was to examine the impacts of using CE strategies in the construction sector. A framework was adapted to guide the application of different CE strategies at the end-of-life of buildings. The framework was assessed by a case study of a residential building in mass timber. This study evaluated the application of CE strategies from the environmental aspect with the life cycle assessment (LCA) method. The results confirmed that circular strategies can deliver lower environmental impacts.

Improving the strength-to-ductility trade-off remains the prime driving force for the development of advanced high-strength steel. Traditionally research breakthroughs are focused on the microstructure and relative phase composition. Herein, laser hardening is applied to ductile ferritic steel to introduce straight and corrugated martensitic reinforcements, effectivelgenerating architectured steel sheets. Tensile behavior of laser-architectured samples is studied both using finite-element method simulation and mechanical testing to reveal the effect of laser-induced corrugations on strength and necking strain. The results show that with the same reinforced volume fraction of 24%, an increase in corrugation height/period leads to a gain in necking strain with a loss in yield strength and ultimate tensile stress. This beneficial effect on necking strain is due to the corrugation unbending process which introduces so-called geometric work hardening during tension. Extended simulations are carried out on various corrugation heights/periods and the evolution trends of ultimate tensile strength and necking change with different reinforced volumes. This study proposes a perspective on corrugation-reinforced architectured materials. Corrugation parameters can be chosen to tailor the mechanical behavior of laser-architectured materials. ANR JCJC SCOLASTIC (ANR-16-CE08-0009)

The present study is based on the patent FR3052379A1, which consists of rolling and gluing green veneers to form structural size hollow tubes. The objective was to study the drying behavior of circular hollow tubes and investigate the method of crack detection using image correlation from green conditions to equilibrium moisture content. The manufactured tubes are composed of six plies. Three different configurations of global grain angle orientations with respect to the tube longitudinal axis are used: {0, 0, 0}°, {10, 0, 10}°, and {− 10, 0, 10}°. Each grain angle was made up of two plies. The tubes deformation and crack formation due to drying shrinkage were measured using a stereo digital image correlation system. The stereo correlation is suitable for measuring tangential shrinkage and studying the opening and/or closing of cracks on the surface of the tubes subjected to internal moisture variations and blocked deformations. The influence of grain angle was discussedin this paper; however, due to the very few numbers of samples, no conclusive findings can be made. The completion of this study was made possible thanks to the financial support of the Carnot Arts Institute. The authors also thank the Xylomat technical platform of the Xylomat scientific network financed by the ANR-10-EQPX-16 XYLOFOREST which was widely used to carry out this study.

To prevent the occurrence of localized necking, the concept of forming limit diagram is often used, thus playing an important role in sheet metal forming processes. The aim of the present study is to develop a numerical tool for the theoretical prediction of forming limit diagrams, which would be a cost-efective procedure as compared to experimental measurements. The proposed numerical tool is based on the Marciniak and Kuczyński imperfection approach combined with the Gurson–Tvergaard–Needleman damage model, which is implemented into the MATLAB program within the framework of plane-stress conditions. Forming limit diagrams have been predicted by assuming both geometric (thickness) as well as material initial imperfections in the Marciniak and Kuczyński imperfection approach. These forming limit diagrams, for different sizes of geometric or material imperfections, are also compared with the forming limit diagram obtained by using the bifurcation theory. It is shown that the bifurcation-based forming limit diagram provides an upper bound as compared to the Marciniak and Kuczyński imperfection approach predictions. The results also reveal that irrespective of the imperfection type considered in the Marciniak and Kuczyński imperfection approach, the corresponding forming limit diagram tends to that predicted by bifurcation theory when the size of initial imperfection tends to zero. Additionally, the predicted ductility limits are lowered as the magnitude of initial imperfection increases; however, the decrease in the ductility limits at balanced biaxial tension is more signifcant than for the other strain-path ratios. The results for the forming limit diagrams indicate that the predicted ductility limits are more sensitive to the initial imperfection in the thickness and the isotropic hardening coefficient as compared to the other types of material imperfections. Moreover, the initial imperfection in the critical porosity is the most infuential one among the Gurson–Tvergaard–Needleman damage parameters. PAKISTAN HIGHER EDUCATION COMMISSION (HEC)

The effect of molecular weight on the crystallization behavior of poly(lactic acid) (PLA) both isothermally and non-isothermally was studied using differential scanning calorimetry and polarized optical microscopy. Two distinct crystal forms (α and α′) were investigated under normal conditions of crystallization for different molecular weights. Using microscopy, the growth rate of spherulites was measured and the nucleation rate was estimated. Heterogeneous nucleation and morphology with a variant α and α′ forms have been proposed. Spherulites from low molecular mass PLA contained more interlamellar amorphous phase. In addition, the results showed more rapid crystallization of α′ than the α form in isothermal conditions.

In order to predict the lifetime of railtrack components, numerical models are required to better describe the apparition of microstructural defects that lead to material failure. In pearlitic steels, the severe mechanical loading or/and the local temperature increase result in the formation of a hard and brittle phase that is prone to cracking, which is called White Etching Layer (WEL). The current study proposes a phenomenological model, based on the microstructural evolution, to describe the mechanically-induced-WEL kinetics of formation. First, a detailed multiscale microstructural characterization was performed in order to identify suitable microstructural indicators for the WEL formation. The grain size, orientation and morphology, and internal disorientation were characterized for different steps of mechanical WEL formation. This could be achieved thanks to the use of a dedicated test bench that allows to monitor the wheel–rail contact condition (sliding, number of cycles, and contact pressure) independently. The proposed model was validated using tests performed in extreme load and sliding conditions. The numerical and experimental results indicate that the most severe conditions (contact pressure and sliding ratio) catalyze WEL formation, and that the same deformation state can be achieved through different loading paths. This work is part of the multi-disciplinary project MOPHAB, which aims to improve our knowledge and understanding of the mechanisms leading to the formation of the white etching layer in the materials used to construct railways and to develop corresponding numerical models. This project was supported by IRT Railenium and other industrial partners (RATP: Régie Autonome des Transports Parisiens, France, SNCF: Société Nationale des Chemins de Fer Francais, France, SAARSTAHL rail).

First of all, this article aimed to evidence the role of a modified printer developed for continuous carbon fibre reinforced PolyAmide (cCF/PA6-I) together with the use of a fully open slicing step on the printing quality and the longitudinal/transverse tensile and in-plane shear properties. A comprehensive assessment of the microstructure and properties with a similar material (cCF/PA6-I), but produced with a commercial printer (i.e., Markforged® MarkTwo) has been achieved. Our customised printer and the open slicer used have made possible to better control the print conditions (i.e., layer height and distance between filaments), to reduce the porosity from more than 10% to about 2% and improve the mechanical properties. Moreover, the understanding of the behaviour of these 3D printed composites with wide-ranging external temperatures is mandatory for future use in a severe environment and/or development of new thermally active 4D printed composites. The 3D printed cCF/PA6-I composites have been then thermomechanically characterised along different printing directions (0, 90 and ± 45°) from −55 to +100 °C. Unlike the longitudinal properties that hardly change with temperature, the transverse and in-plane shear stiffness and strength of these 3D printed composites were particularly sensitive to temperature variations, with decreases of 25–30% and 30–55%, respectively. This was due to the high sensitivity of the polymer matrix, the fibre/matrix and interfilament interfaces when the composites were loaded along those directions, because damages induced by internal thermal stresses. Fractography has also been carried out to reveal damage mechanisms. The authors would like to thank IRT Saint Exupery, the European Space Agency (ESA contract 4000133620) for financial support. Antoine le Duigou wish also to thank the French Ambassady in Japan and the PHC SAKURA program.

Cast aluminium alloys, and more widely cast materials, are frequently used in industry. The casting process allows for complex geometries of parts, but, on the downside, often causes materials voids. It is well known these material defects are harmful for material fatigue performances, but the nature of these defects, in a statistical manner, are more seldom studied. This paper aims at proposing a methodology for finding the underlying characteristics of the defect population (size and spatial distribution) and determine their implication on fatigue behaviour in the presence of stress/strain gradients (notched specimens). To do so, various statistical tools are brought from different fields, such as point processes, and applied to experimentally observed defect distributions (by μCT tomography on virgin test specimens). The population of defects is clearly identified, and it is shown these defects are not randomly distributed, but rather in cluster. It is also shown there is no strong link between the defect size an it’s location. Knowing the statistics of the defect population, it is then possible to confront the result of fatigue tests (and the observed initiating defects) with the simulated defect population: the fatigue crack initiation mechanisms, which favour (sub-) surface rather than core initiating defects, reduce the size of the active zone and therefore artificially shift the defect size distribution (by reducing their number).

International audience; As a first step to devise a hybrid process for the production of TiC wear coatings on 316L, consisting of magnetron sputtering followed by titanium carburization, interfacial reactivity between stainless steel and titanium has to be finely understood. Systematic comparisons were carried out on diffusion couples of increasing chemical and geometrical complexity (Fe/Ti, 316L/Ti, and 316L/sputtered Ti), highlighting the formation mechanisms of interfacial structures. Transmission and scanning electron microscopy composition profiles revealed that long-range microstructures in titanium are the result of iron diffusion and oxygen impurities interactions. FeTi and Fe2Ti intermetallics formation is first kinetically driven, then favors thermodynamic stability, leading to compositional changes during thermal cycles. Their growth is shown to be non-diffusion controlled. These compounds act as diffusion barriers for chromium, and traps for carbon, indirectly generating a complex layered structure at the interface. Differences between bulk and sputtered titanium are exclusively linked to the latter smaller scale, including destabilized diffusion fronts, and superficial TiO formation by oxygen rejection after iron diffusion.

Impellers are referred to as a core component of turbomachinery. The use of impellers in various applications is considered an integral part of the industry. So, increased performance and the optimization of impellers have been the center of attention of a lot of studies. In this regard, studies have been focused on the improvement of the efficiency of rotary machines through aerodynamic optimization, using high-performance materials and suitable manufacturing processes. As such, the use of polymers and polymer composites due to their lower weight when compared to metals has been the focus of studies. On the other hand, methods of the manufacturing process for polymer and polymer composite impellers such as conventional impeller manufacturing, injection molding and additive manufacturing can offer higher economic efficiency than similar metal parts. In this study, polymeric and polymer composites impellers are discussed and conclusions are drawn according to the manufacturing methods. Studies have shown promising results for the replacement of polymers and polymer composites instead of metals with respect to a suitable temperature range. In general, polymers showed a good ability to fabricate the impellers, however in more difficult working conditions considering the need for a substance with higher physical and mechanical properties necessitates the use of composite polymers. However, in some applications, the use of these materials needs further research and development.

Balanites aegyptiaca est une espèce caractéristique et emblématique des zones sèches d’Afrique et d’Asie. Elle revêt une grande importance socio-économique dans toute sa zone naturelle de répartition du fait de ses multiples usages. Toutefois, les propriétés technologiques de son bois sont mal connues, d’où des utilisations parfois inappropriées mais qui pourraient être élargies. Afin de mieux adapter ses applications à ses caractéristiques, nous avons déterminé les indicateurs de stabilité physique (masse volumique, infradensité, retrait radial total, retrait tangentiel total, retrait volumique total et point de saturation des fibres) et les indicateurs de comportement mécanique (module d’élasticité longitudinal, contrainte de rupture en flexion et compression) de ce bois. Quatre-vingt-treize éprouvettes prélevées dans 13 arbres provenant des zones sahélienne et soudanienne tchadiennes, et de la zone sahélienne sénégalaise ont été testées. Les résultats obtenus montrent que, pour les trois provenances, le bois de B. aegyptiaca est mi-lourd (797 kg/m3) avec une stabilité dimensionnelle moyenne : l’anisotropie de retrait est supérieure à 2 (2,2), le retrait radial total et le retrait tangentiel total sont moyens, respectivement égaux à 4 % et 8,5 %. Ses caractéristiques mécaniques sont moyennes (contraintes de rupture en compression et flexion statique respectivement égales à 49,4 MPa et 104,5 MPa) à faible (module d’élasticité longitudinal de 10 473 MPa). Une comparaison des résultats obtenus en fonction des zones de prélèvement a mis en évidence des tendances variables selon les caractéristiques étudiées. Ces variations entre les trois provenances restent cependant limitées. Les résultats de l’étude montrent que le bois de B. aegyptiaca pourrait être utilisé de façon appropriée sous forme de matériau pour une plus large gamme d’emplois, sous réserve de la mise en place d’une gestion adaptée permettant sa restauration par plantation.

A strategy of CO2-assisted extrusion foaming of PMMA-based materials was established to minimize both foam density and porosities dimension. First a highly CO2-philic block copolymer (MAM: PMMA-PBA-PMMA) was added in PMMA in order to improve CO2 saturation before foaming. Then the extruding conditions were optimized to maximize CO2 uptake and prevent coalescence. The extruding temperature reduction led to an increase of pressure in the barrel, favorable to cell size reduction. With the combination of material formulation and extruding strategy, very lightweight homogeneous foams with small porosities have been produced. Lightest PMMA micro foams (ρ = 0.06 g cm−3) are demonstrated with 7 wt% CO2 at 130°C and lightest blend micro foams (ρ = 0.04 g cm−3) are obtained at lower temperature (110°C, 7.7 wt% CO2). If MAM allows a reduction of Tfoaming, it also allows a much better cell homogeneity, an increase in cell density (e.g., from 3.6 107 cells cm−3 to 2 to 6 108 cells cm−3) and an overall decrease in cell size (from 100 to 40 μm). These acrylic foams produced through scCO2-assisted extrusion has a much lower density than those ever produced in batch (ρ ≥ 0.2 g cm−3). ANR : AAPG PRCE 2018CE06 0030,2019

The ductile failure of crystalline materials is strongly linked to the growth of intragranular voids. The estimation of the overall yield criterion thus requires to take into account the anisotropic plastic behavior of the single crystal. In the framework of the kinematic limit-analysis approach, this problem has been considered up to now with Gurson-type isotropic trial velocity fields. In the present work, a different class of piecewise constant velocity fields is proposed based on a detailed analysis of FFT numerical results on the strain localization in porous single crystals with periodic distributions of voids. This original approach is implemented for the model 2D problem of a square or hexagonal array of cylindrical voids in a hexagonal close-packed single crystal with in-plane prismatic slip systems. For equibiaxial loadings, the assumption of discontinuous velocity field provides a good approximation of the smooth jumps observed in the numerical results. Consistently, this new proposal leads to a significant improvement on the macroscopic yield stress with respect to the estimate based on an isotropic velocity field. Our theoretical estimate almost coincides with the FFT numerical results for all the unit-cells and crystalline orientations considered.

The element boron is widely used in many industrial fields (semiconductor industry, glass industry, etc.). In order to assess the environmental impact of industrial products containing boron from cradle to grave, it is necessary to consider the impact of borate minerals on the environment. The literature on this subject is quite poor and the inventory of data on the life cycle of boron mining is very scarce. This article presents a synthesis of a literature review on this topic and provides easy access to important data on boron use and production capacities of Turkish boron facilities. The scope of Turkey has been chosen because the country has the largest deposits of borate ores in the world. The literature review is based on the analysis of sixty-three theses and fourteen reports in the fields of mining engineering, geology and earth sciences, environmental sciences, and chemical engineering. The production capacities from 1985 to 2016 (most recent data) and supporting data for each facility were studied using bibliometrics analysis. The data were then evaluated by calculating a data quality matrix, the coefficient of dispersion, and the standard deviations. We have found that the data compiled is generally of good quality. The values of the production capacities ±2.3 tons have 95% chance to be the real values of the production capacities of the boron industry in Turkey. The data obtained constitute a basis for enriching models in the field of life cycle assessment (LCA), sustainability, and/or material flow analysis (MFA) applied to borate mineral processing. 2232 International Fellowship for Outstanding Researchers Program of TÜB ̇ITAK (Project No: 118C219).

International audience; This study investigates the mechanical and thermophysical performance of cement mortars incorporating microencapsulated phase change materials (mPCMs), which consist of an aqueous dispersion of 100% bio-based fine core–shell particles. A specific protocol was used to manufacture the mortar samples, which ensures a homogeneous particle distribution and prevents microcapsule leakage. The addition of mPCMs to the mortar causes both a decrease in density, an increase in porosity, and a substantial loss of mechanical strength. Conversely, hot-disk characterization revealed a large improvement in the thermal performance. The system containing 8 wt% mPCMs exhibits a good balance between its mechanical and thermal properties.

Al-7Si-0.5Mg aluminum alloy semi-solid slurry with good spherical grains was prepared by gas induced semi-solid process (GISS) and the effects of both holding time and medium alloy addition on the microstructure of the semi-solid slurry were investigated. These two parameters have a great influence on the solid fraction, the size and the sphericity of the grains. With holding time increased from 85 s to 270 s, the solid phase fraction of the semi-solid slurry decreased from ~0.77 to ~0.67, the average grain size increased from ~95 μm to ~225 μm and the average shape factor decreased from ~0.80 to ~0.33. When medium alloy addition varied in the range of 0.5–2.0 wt%, a better slurry microstructure was obtained at about 1.5 wt%. Compared with the conventional liquid die-casting, the semi-solid die-casting improved the mechanical properties of tensile bars; yield strength, tensile strength and elongation of tensile bars reached ~240 MPa, ~307 MPa and ~8.8% after heat treatment, respectively. In conclusion, GISS process can prepare the semi-solid slurry with uniform and round microstructure, and the semi-solid die-casting can improve mechanical properties of Al-7Si-0.5Mg aluminum alloy.

The investigation of humidity movement during drying or imbibition processes represents a serious challenge for several industries, such as the wood-based material industry and paper industry. Recently, several studies have been conducted on the efficiency contactless Terahertz technique (THz) to map the water content. In this study, this technique based on coupling infrared camera and developed Tera-Thermo-Converter, is used for the estimation of mass diffusion coefficient within hygroscopic materials initially dry. A water vapour water content excitation device is designed to excite the samples in a THz semitransparent enclosure during the monitoring. The recorded infrared films showed a pronounced mitigation of the signal over time, indicating penetration of vapour through the sample. Processing image techniques such as the four-image, algorithm and Singular Value Decomposition (SVD) and averaging are used to obtain the space-time water content map. A simplified one-dimensional model of mass transfer is proposed to estimate the diffusion coefficient using two inverse methods: a) a statistical method based on Bayesian approach, and b) a minimization method based on Levenberg‒Marquardt algorithm (LM). The results showed that THz imaging technique coupled with the appropriate processing and the adequate modelling, is able not only to map the water content field but also to monitor the transient transfer and estimate the diffusion coefficient without contact.

Extending the fused filament fabrication process to highly filled thermoplastics in metallic powder used in metal injection molding is a promising method to produce small series. However, the lack of adhesion between deposited filaments can cause ruptures during the fabrication or debinding process. We designed a simple device to measure the shear strength required to tear off a filament deposited on a substrate. This device makes it possible to quickly determine the processing window for a good welding of filaments. We developed a 2D thermal simulation using the finite difference method while integrating the enthalpy of fusion and crystallization kinetics of the material. We then fitted it to the thermal measurements at depths of 0.45 and 0.75 mm under the substrate surface using small-diameter thermocouples. Simulation results highlight the key role of the thermal contact resistance between the filament and the substrate in the evolution of the interface temperature. This provides essential information to explain the process window that can be determined experimentally. The characteristic time of macromolecule diffusion was determined by rheological measurements and was found to be too small to play a role in filament bonding for the simulated cooling rates for the studied material. The methodology introduced in this work was used to improve highly filled polymers interlayer adhesion, but it can be used to improve other filled or unfilled polymers

In this review paper, recent developments in the Fused Filament Fabrication (FFF) approach are provided for composite materials. Influencing parameters in FFF process such as road width, print speed, layer thickness, feed rate and build temperature of the model (both liquefier and envelope temperature), fiber orientation, the layer position, volume frac-tion, and infill orientation have been studied. These considered parameters in the strength/bonding or physicochemical characterizations of FFF-fabricated parts have been presented in detail. An overview of the mechanical properties of printed parts for different composite material systems is presented and discussed. Three types of reinforced polymers in FFF process have been considered: filled reinforced polymers, continuous fiber-reinforced poly-mers, and short fiber reinforced polymers.

International audience; 3D-printed continuous ramie fiber reinforced polypropylene composites (CRFRPP) are expected to ensure good mechanical properties while meeting the requirements of environmental friendliness and sustainability. To promote the wide industrial application of CRFRPP, this work investigated the effects of printing parameters (extrusion flow rate, printing temperature, layer thickness and printing speed) on the interfacial properties of CRFRPP. The interlayer and intralayer interfacial properties of CRFRPP with different printing parameters were studied using the design of experiment approach. Machine learning methods and response surface methodology prediction were also carried out based on the experimental results to bridge the printing parameters and interfacial properties. According to the prediction results, the printing parameters were optimized to improve the production efficiency while ensuring the desired interfacial performance. At last, the bending tests were conducted to investigate how the difference in interfacial properties can be translated to the mechanical performance. The results found that printed specimens with weak interfacial strength suffered interlaminar delamination failure when subjected to bending loads, greatly weakening the mechanical properties of the composites.

This paper presents an innovative methodology of material characterization under high strain rate (order of 10$^7$s$^{–1}$) laser shock loading coupled with microstructural and mechanical material features. To that scope, experimental and simulation analyses have been conducted for Al alloys (AA7075-T6 and AA2017-T4) and dissimilar Friction Stir Welded (FSWed) AA7075-AA2017 joint, under shock pressure of 4.5 GPa (laser power density of 3.5 GW/cm$^2$). In order to perform proper in-depth material model simulation of these alloys and dissimilar pairs, Johnson–Cook (J-C) material model has been coupled with Grüneisen equation of state using the non-linear explicit code LS-DYNA. For the first time, we provided a way to differentiate between material behaviour in the cross-section and the in-plane rolling and welding direction. What is more, we have provided the link between microstructural features and mechanical properties such as microhardness, residual stresses and the identified material parameters. By achieving this goal, the bigger difference between studied planes was confirmed for strain hardening modulus, strain hardening exponent and strain rate sensitivity parameters. Obtained results and proposed methodology indicate high potential to predict material properties and behaviour of dynamically stressed parts and at the same time can be used for optimization of LSP process.

Carburization assisted by laser processing is a promising method to strengthen metallic materials. Direct laser beam carburization is implemented for the first time on thin AISI 430 ferritic stainless steel (FSS) sheets with graphite coating under different conditions. Microstructural morphology, phase constitution, carbon content, microhardness, and tensile behavior are investigated to evaluate the laser carburization effect. The carburized zone presents different morphologies according to the linear energy density of the laser beam. The least carbon content is around 0.4 wt% in the carburized zone where austenite becomes the leading phase. Delta ferrite is found in a cellular carburized area, which resembles a duplex microstructure. The hardness of carburized zone has been at least increased by 130%, the yield strength and ultimate tensile strength of a fully carburized sample can be increased by respectively 90% and 85%. This hardening effect is driven by the precipitation of carbides formed during solidification offering pinning points for dislocations and grain boundaries. These improvements could be useful to modify locally ferritic stainless steel to meet industrial needs such as wear-resistant surfaces.

Corrosion is a major concern for the aeronautic industry and providing structures with the intrinsic ability to monitor autonomously their health state is a major actual academic and industrial challenge. In this paper, detection, localization, and quantification of a damage representative of a corrosion damage using Lamb waves emitted and received by piezoelectric elements for the purpose of structural health monitoring of aeronautics aluminum structures is addressed. Semi-spherical holes of different sizes representing a calibrated corrosion pit are manufactured on a 2024 aluminum plate with four piezoelectric sensors bonded on it. Lamb waves are then recorded with one element used as an actuator and the other ones being used as sensors. A dedicated recording system provided by Cedrat Technologies is used to acquire Lamb waves data. It is demonstrated on this representative example that by using actual algorithms from the SHM literature, it is possible to detect, localize, and quantify this damage representative of an actual corrosion damage. These preliminary results are very encouraging before monitoring actual corrosion and fatigue damages which constitutes the main objective of the COQTEL project. ANR COQTEL

International audience; Measuring the viscoelastic behavior of polymers in the vicinity of a surface or under confinement is an experimental challenge. Simple rheological tests of nanolayered films of polyethylene/polyamide 6 compatibilized in situ during the coextrusion process enabled the probing of these interfacial properties. Taking advantage of the different melting points and of the multiplication of the number of interfaces, a drastic increase of dynamic moduli was reported when increasing the interphase volume fraction in the films. A solid-like behavior for the interphase was identified. The complex viscosity of nanolayered films as a function of angular frequency was quantitatively captured for all samples using a weighted mixing law of bulk and interphase viscosities, without additional adjusting parameters, highlighting the interfacial synergy developed in nanolayered polymer films.

This paper deals with the thermal ageing of ELIUM® based composites filled with mineral fillers (aluminium trihydrate in particular) and corresponding matrices. The ageing of thin films and thick blocks was investigated by gravimetry. The comparison of matrices with an incremental complexity highlighted the effect of comonomers and thermal stabilizers. In all cases, unzipping was shown to be the predominant source of mass loss but oxidation seems also to be involved in the case of ageing under air. The existence of this latter was confirmed by the existence of a brown surface layer. This oxidized layer was shown to be deeper for filled composites than unfilled matrices, suggesting that fillers favor the oxygen diffusion into the bulk.

Corrosion is a major concern for the aeronautic industry and providing structures with the intrinsic ability to monitor autonomously their health state is a major actual academic and industrial challenge. In this paper, detection, localization, and quantification of a damage representative of a corrosion damage using Lamb waves emitted and received by piezoelectric elements for the purpose of structural health monitoring of aeronautics aluminum structures is addressed. Semi-spherical holes of differ- ent sizes representing a calibrated corrosion pit are manufactured on a 2024 aluminum plate with four piezoelectric sensors bonded on it. Lamb waves are then recorded with one element used as an actuator and the other ones being used as sensors. A dedicated recording system provided by Cedrat Technologies is used to acquire Lamb waves data. It is demonstrated on this representative example that by using actual algorithms from the SHM literature, it is possible to detect, localize, and quantify this damage representative of an actual corrosion damage. These preliminary results are very encouraging before monitoring actual corrosion and fatigue damages which constitutes the main objective of the COQTEL project. H2020 REMAP

International audience; The stainless clad steel materials (particularly A283-Gr-C hot-rolled to austenitic stainless steel plate SA240 TP 316L) have become widely used in the fabrication of heat exchangers, pressure vessels, and other components owing to their very interesting properties and low production cost. These cladded materials are mostly joined using multi-pass welding techniques. The temperature distribution that supervenes during welding affects the microstructures and the mechanical properties and may generate residual stresses in the heat-affected zone of the welded plates. Since limited experimental data are available in the literature regarding the complex cases of multi-pass welding of cladded steel materials, a thorough experimental study was performed in order to evaluate the temperature distribution on the welded plates. In fact, eight K-type thermocouples were fixed at different distances from the weld centerline in order to record the temperature evolution along longitudinal, transversal, and thickness directions during the welding process. Due to the unavoidable effects of the generated heat fluxes that always follow the welding, several dimensional changes were occurred on the welded plates. In this study, the longitudinal shrinkage and the angular distortion generated during the welding process by the effect of the heat fluxes were investigated. Then, tensile and bending tests were performed in order to check the welded plate reliability. It was found that (i) the welded joint presents a higher mechanical tensile strength than the parent metal and (ii) no separations, fractures, or tearing appear on the weld joint surface after the bending test.

The joining of stainless clad steel plates (SCSPs) by welding processes is relatively difficult due to differences in the chemical compositions and the physical and mechanical properties between both the carbon and the stainless steels comprising the clad material. These welded structures often suffer from several structural integrity problems such as bulging phenomena that can appear after bending tests, in the welded zone, due to the presence of a local hardening zone (LHZ). The main purpose of this paper is to investigate the origin of the LHZ typically produced in the welded joint of SCSPs after the bending operation. Optical micrographs revealed the presence of a typical pearlitic-ferritic structure in the welded zone filled with E7018 metal and a dendritic δ-ferrite structure solidified under a skeletal form in the welded zone filled with ER316L metal. The microstructure of the weld metal transition zone (WMTZ) filled with ER309L metal shows the presence of martensitic laths as well as cellular and columnar structures. In addition, the WMTZ revealed the presence of three types of grain boundaries, which are formed during the gas tungsten arc welding process: solidification sub-grain boundary, solidification grain boundary, and migrated grain boundary. Vickers microhardness measurements performed along the thickness of the welded joint showed that the highest microhardness value (406 HV) was observed at the WMTZ. The significant increase of the microhardness value in this transition zone was attributed to the presence of martensitic laths as well as cellular and columnar structures.

The consumption of most metals continues to rise following ever-increasing population growth, affluence and technological development. Sustainability considerations urge greater resource efficiency and retention of metals in the economy. We model the fate of a yearly cohort of 61 extracted metals over time and identify where losses are expected to occur through a life-cycle lens. We find that ferrous metals have the longest lifetimes, with 150 years on average, followed by precious, non-ferrous and specialty metals with 61, 50 and 12 years on average, respectively. Production losses are the largest for 15 of the studied metals whereas use losses are the largest for barium, mercury and strontium. Losses to waste management and recycling are the largest for 43 metals, suggesting the need to improve design for better sorting and recycling and to ensure longer-lasting products, in combination with improving waste-management practices. Compared with the United Nations Environmental Programme’s recycling statistics, our results show the importance of taking a life-cycle perspective to estimate losses of metals to develop effective circular economy strategies. We provide the dataset and model used in a machine-readable format to allow further research on metal cycles ADEME BRGM

Knowledge of material emissivity maps and their true temperatures is of great interest for contactless process monitoring and control with infrared cameras when strong heat transfer and temperature change are involved. This approach is always followed by emissivity or reflections issues. In this work, we describe the development of a contactless infrared imaging technique based on the pyro-reflectometry approach and a specular model of the material reflection in order to overcome emissivities and reflections problems. This approach enables in situ and real-time identification of emissivity fields and autocalibration of the radiative intensity leaving the sample by using a black body equivalent ratio. This is done to obtain the absolute temperature field of any specular material using the infrared wavelength. The presented set up works for both camera and pyrometer regardless of the spectral range. The proposed method is evaluated at room temperature with several heterogeneous samples covering a large range of emissivity values. From these emissivity fields, raw and heterogeneous measured radiative fluxes are transformed into complete absolute temperature fields.

In the pursue of smart structures for cyber-physical health management of lightweight engineering structures, a number of structural health monitoring methods have been developed. Each SHM technique has different coverage and sensitivity to certain types of damage. In particular, the structural degradation of composites under fatigue loading is multi-causal and intricate, and none of the techniques alone is able to fully capture the fatigue degradation phenomenon. This paper presents the considerations and results in a fusing strategy of two different SHM techniques, distributed optical strain sensing and guided wave, on the in-situ monitoring of an aircraft wing structure under compression-compression fatigue loading. The emergence and growth of localized damage (disbond of stiffener foot) and the degradation of mechanical performance (stiffness degradation) caused by the accumulation of distributed fatigue damage have been monitored in the synergy of the two different SHM techniques. The result shows that the fusion strategy unveils the fatigue degradation phenomenon in a more extensive manner than using two techniques separately. H2020 REMAP

The deployment of Deep Learning (DL) strategies is particularly advantageous in Structural Health Monitoring (SHM) based of lamb Wave (LW) propagation due to the high quantity of data collected by the network of piezoelectric transducers (PZT) during all the life cycle of the composite structure. However, such strategies rely on large training databases, difficult to collect experimentally. The use of numerical simulations faces that issue, but the modelsnever fit perfectly to the real structures, leading to error of diagnostic. We propose here to use Transfer Learning (TL) approaches to reduce the predictions errors of a Convolutional Neural Network (CNN) trained with numerical data. The network predicts the size and the position of a damage on a composite plate equipped with PZT. It is trained on a large source database composed of different damage scenarios on a composite plate. A second smaller target database is generated with small variations on the mechanic properties and PZT positions to simulate manufacturing uncertainties. Those uncertainties lead to prediction errors of the CNN. A Domain Adaptation (DA) based on Optimal Transport (OT) is used to project the target data on the source domain and therefore reduces the predictions error of the CNN. These TL approach should allow us to close the gap between experimental and numerical data. FUI MONARQUE

Plywood made of poplar are limited to indoor usages since poplar exhibits a rather low natural durability. Recently, wood heat treatments are applied to improve properties such as decay susceptibility and dimensional stability. Hence, to extend the potential of applications of this engineered wood product to outdoor end uses, and new markets accordingly, this study examines the potential of exposing poplar plywood to heat treatment. Plywood panels were glued with two kind of adhesives to compare their respective ability to resist the heat treatment. Those different plywoods were heat treated in saturated steam conditions at 215 °C for 2 hours following the ThermoWood® process up to a 14% mass loss. The durability improvement brought by the heat treatment was assessed in order to evaluate any possible outdoor uses for such plywoods. The authors acknowledge Jean Perche from Bois Durables de Bourgogne Company for his contribution in the thermal modification processes. This study was performed thanks to the partnership build by BOPLI (https://artsetmetiers.fr/fr/bopli-bourgogne-placage-innovation). The authors would also like to thank the Xylomat Technical Platform from the Xylomat Scientific Network funded by ANR-10-EQPX-16 XYLOFOREST.

Micromachining allows the production of micro-components with complex geometries in various materials. However, it presents several scientific issues due to scale reduction compared to conventional machining. These issues are called size effects. At this level, micromachining experiments raise technical difficulties and significant costs. In this context, numerical modeling is widely used in order to study these different size effects. This article presents four different numerical models of micro-cutting of hardened steel, a Smooth Particle Hydrodynamics (SPH) model and three finite element (FE) models using three different formulations: Lagrangian, Arbitrary Eulerian–Lagrangian (ALE) and Coupled Eulerian–Lagrangian (CEL). The objective is to study the effect of tool edge radius on the micro-cutting process through the evolution of cutting forces, chip morphology and stress distribution in different areas and to compare the relevance of the different models. First, results obtained from two models using FE (Lagrangian) and SPH method were compared with experimental data obtained in previous work. It shows that the different numerical methods are relevant for studying geometrical size effects because cutting force and stress distribution correlate with experimental data. However, they present limits due to the calculation approaches. For a second time, this paper presents a comparison between the four different numerical models cited previously in order to choose which method of modeling can present the micro-cutting process.

This paper describes a new single-shear specimen (SSS) and method to characterize the dynamic shear behavior of bulk metals using a traditional Split Hopkinson Pressure Bar (SHPB). By this method, the shear behavior of materials can be tested conveniently over a wide range of strain rates within 105 s−1. This technique was applied to a 304 austenitic stainless steel (ASS) under shear strain rates from 0.001 s−1 to 38700 s−1 at room temperature. Based on finite element (FE) simulations, it was found that the deformation of the specimen shear zone was dominated by shear stress/strain components. Stress state parameters represented by stress triaxiality η and Lode angle parameter θ - were found very close to zero, indicating a deformation mode of simple shear. Besides, an obvious gap existed between the local deformation behavior in the specimen shear zone and the macroscopic stress-strain relations measured by the strain gauges on the SHPB bars. A correction coefficient method was adopted to extract the real shear behavior from the experimentally obtained force-displacement data. Through comparisons between the tested and simulated stress-strain curves, a good agreement was obtained.

Fused filament fabrication (FFF), an additive manufacturing technique, is used to produce prototypes and a gradually more important processing route to get final products. Due to the layer-by-layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed. Thus, it is strongly in conjunction with the temperature development of the filaments during the deposition sequence. This study gives out an in-process set-up enabling to record temperature profile of two adjacent filaments or a sequence of deposition in various locations during FFF process. The main characteristic of the presented procedure is the possibility of obtaining a global temperature profile resulted from an IR-camera; parallel to those recorded using a K-type thermocouple. Needless to say that a K-type thermocouple accurately records the local temperature at the interface of adja cent filaments. Conversely, an IR-camera signifies the temperature profile on the captured surface. The obtained results showed that there is a remarkable difference between the cooling rate and re-heating peaks. The primary out come of this study is the consideration of results accuracy and the possibility of working on optimization of the obtained temperature profile. Altogether it helps optimize inter-layer strength while assessing the temperature evolution.

Este artículo se encuentra disponible en la siguiente URL: http://www.aimspress.com/article/10.3934/matersci.2020.4.364 The aim of this paper is to leverage the main surface topological descriptors to classify tape surface profiles, through the modelling of the evolution of the degree of intimate contact along the consolidation of pre-impregnated preforms associated to a composite forming process. It is well-known at an experimental level that the consolidation degree strongly depends on the surface characteristics (roughness). In particular, same process parameters applied to di erent surfaces produce very di erent degrees of intimate contact. It allows us to think that the surface topology plays an important role along this process. However, solving the physics-based models for simulating the roughness squeezing occurring at the tapes interface represents a computational e ort incompatible with online process control purposes. An alternative approach consists of taking a population of di erent tapes, with di erent surfaces, and simulating the consolidation for evaluating for each one the progression of the degree of intimate contact –DIC– while compressing the heated tapes, until reaching its final value at the end of the compression. The final goal is creating a regression able to assign a final value of the DIC to any surface, enabling online process control. The main issue of such an approach is the rough surface description, that is, the most precise and compact way of describing it from some appropriate parameters easy to extract experimentally, to be included in the just referred regression. In the present paper we consider a novel, powerful and very promising technique based on the topological data analysis –TDA– that considers an adequate metrics to describe, compare and classify rough surfaces.

Log temperature appreciably influences veneer quality during the rotary peeling process. The assessment of the thermal properties of green wood is complex and typically requires the sawing of small calibrated samples. This study introduced a simple approach based on an inverse identification method to determine the global log thermal diffusivity online and without the time-consuming extraction of wooden samples that is commonly used to perform diffusivity experiments. This method was applied to green Douglas fir logs and resulted in an average thermal diffusivity of 0.175 ± 0.021 mm2.s-1. This method was found to be suitable for both heartwood and sapwood and thus can provide a globally applicable diffusivity assessment method. This global parameter is essential to optimizing the soaking time and improving the subsequent veneer production quality. As log-soaking preprocessing requires an immense input of energy, this time-optimization strategy will allow sizable cost reduction and ecological improvement. Région Bourgogne-Franche-Comté Ministère de l'Agriculture et de l'Alimentation

This research work investigates the possibility to use a hygroscopic model based on Fick’s law to predict the global moisture content variations an historical violin undergoes during a concert. To set up the model to work some input are required such as: the object geometries, the wood species used, the thicknesses, the moisture diffusion coefficients, the permeability of varnished surfaces, the anhydrous masses of the moisture exchanging parts, the sorption isotherms, information often far from being available or measurable. At a first extent, the model was run on the environmental conditions recorded during nine concerts played with the “Cannone” violin (1743) and the computed mass variations compared with the mass variations recorded during the same concerts. The model, set with simplifying conditions and with diffusion coefficients from literature, has shown a very little predictive capacity. On the other hand, the model was tuned on the experimental data using an inverse procedure for moisture diffusion coefficient identification. After the tuning the model has shown a very good predictive ability showing how Fick’s low can be profitably used to assess the mass transfer in a complex heritage object such as a violin. This paper highlights the possibility to successfully use the Fick’s law to model mass transfer in a violin but also makes evident how such models must be tuned with real measurements in order to be effective.

International audience; We report that 316L austenitic stainless steel fabricated by direct laser deposition (DLD), an additive manufacturing (AM) process, have a higher yield strength than that of conventional 316L while keeping high ductility. More interestingly, no clear anisotropy in tensile properties was observed between the building and the scanning direction of the 3D printed steel. Metallographic examination of the as-built parts shows a heterogeneous solidification cellular microstructure. Transmission electron microscopy observations coupled with Energy Dispersive X-ray Spectrometry (EDS) reveal the presence of chemical micro-segregation correlated with high dislocation density at cell boundaries as well as the in-situ formation of well-dispersed oxides and transition-metal-rich precipitates. The hierarchical heterogeneous microstructure in the AM parts induces excellent strength of the 316L stainless steel while the low staking fault energy of the as-built 316L promotes the occurrence of abundant deformation twinning, in the origin of the high ductility of the AM steel. Without additional post-process treatments, the AM 316L proves that it can be used as a structural material or component for repair in mechanical construction.

International audience; To reinforce the environmental standards, we need to strengthen the lightening of vehicles and to generalize new composite materials in order to reduce weight. To use these innovative composite materials in the mass production of automotive parts, it is essential to propose a predictive approach of the S-N curves, which must be established for each new composite formulation and for several types of microstructure within real components. Although these preliminary characterizations consume time and money, this paper proposes two hybrid methodologies to predict the fatigue life during the fatigue test. Both methodologies are based on micromechanical modeling which is developed under monotonous loading with fatigue effects under different amplitudes. The suggested methodology is based on an experimental analysis of monotonic behavior under fatigue loading and on multi-scale modeling of damage. In the results, the proposed model and the used approaches are in good agreement with the experimental results.

Ti and its alloys have a variety of applications in aerospace industry and medical implants. The formation of hydride has been used in biomedical areas and can significantly influence the mechanical performance of materials. In this work, we investigate the orientation dependence of hydride precipitation in commercially pure titanium via interrupted in-situ electron backscatter diffraction (EBSD) measurements. The results reveal that hydrides during hydrogen charging at room temperature exhibit two types of orientation relationships with α-titanium, i.e., { 0001 } α / / { 1 1 ¯ 1 } δ 1 2 ¯ 10 > α / / 110 > δ with interface plane { 10 1 ¯ 3 } α / / { 1 1 ¯ 0 } δ (B-type), and {0001}α//{001}δ 1 2 ¯ 10 > α / / 110 > δ with interface plane { 10 1 ¯ 0 } α / / { 1 1 ¯ 0 } δ (P-type). Significant orientation dependence of hydride precipitation is observed, especially when { 10 1 ¯ 3 } , { 10 1 ¯ 0 } , {0001} or { 11 2 ¯ 0 } planes of the parent grains are parallel to the diffusion surface. The displacement gradient tensor based accommodation shows that the orientation dependence is attributed to the strain relaxation of hydride transition. Three types of hydride platelets are characterized: parallel hydride platelets (Type I), crossed hydride platelets (Type II) and clustered hydride platelets (Type III). The multiple morphologies of hydride platelets resulting from the hydride variant selection and interaction are dependent on the crystal orientation of the matrix.

The a -> b phase transformation upon heating in the Ti-5553 alloy with lamellar-nodular bimodal microstructure was tracked in situ with high energy X-ray diffraction. Rapid heating at 10, 50 and 100 °C s-1 from room temperature to 1050 °C was tested. Phase transformation on heating was studied by a combined analysis of the microstructural features that provides estimates of mass fractions, mean lattice parameters and full width at half maximum for the two phases. In comparison with equilibrium conditions, the experimental mass fractions reveal a shift of the transformation domain toward high temperatures when the heating rate increases. Also, the dissolution of the a phase is largely impacted by its morphology, the transformation being faster for a lamellae. The combined analysis of mean lattice parameters and full width at half maximum suggests that the a -> b phase transformation on heating is diffusion controlled. The b phase therefore inherits the solute content of the adjacent parent a phase, leading to chemical heterogeneities in the b phase regardless of the heating rate.

Purpose The accessibility to most metals is crucial to modern societies. In order to move towards more sustainable use of metals, it is relevant to reduce losses along their anthropogenic cycle. To this end, quantifying dissipative flows of mineral resources and assessing their impacts in life cycle assessment (LCA) has been a challenge brought up by various stakeholders in the LCA community. We address this challenge with the extension of previously developed impact assessment methods and evaluating how these updated methods compare to widely used impact assessment methods for mineral resource use. Methods Building on previous works, we extend the coverage of the average dissipation rate (ADR) and lost potential service time (LPST) methods to 61 metals. Midpoint characterization factors are computed using dynamic material flow analysis results, and endpoint characterization factors, by applying the market price of metals as a proxy for their value. We apply these methods to metal resource flows from 6000 market data sets along with the abiotic depletion potential and ReCiPe 2016 methods to anticipate how the assessment of dissipation using the newly developed methods might compare to the latter two widely used ones. Results and discussion The updated midpoint methods enable distinguishing between 61 metals based on their global dissipation patterns once they have been extracted from the ground. The endpoint methods further allow differentiating between the value of metals based on their annual average market prices. Metals with a high price that dissipate quickly have the highest endpoint characterization factors. The application study shows that metals with the largest resource flows are expected to have the most impacts with the midpoint ADR and LPST methods, metals that are relatively more expensive have a greater relative contribution to the endpoint assessment. Conclusion The extended ADR and LPST methods provide new information on the global dissipation patterns of 61 metals and on the associated potentially lost value for humans. The methods are readily applicable to resource flows in current life cycle inventories. This new information may be complementary to that provided by other impact assessment methods addressing different impact pathways when used in LCA studies. Additional research is needed to improve the characterization of the value of metals for society and to extend the methods to more resources.

The success of biomedical implantation is linked to osseointegration, depending on the mechanical loading of the bone interface. The large difference in stiffness between the host bone (30 GPa) and the usual implant material (over 100 GPa), as well as the absence of mechanical stress at the surrounding bone, induce a stress shielding effect, which leads to bone atrophy and implant loss. A recent work has shown the possibility to produce so-called second-generation titanium alloys. β-type Ti alloys have been studied for biomedical applications, due to the composition of non-cytotoxic elements. Some TiNb alloys can reach after heat treatment a Young’s modulus close to 35 GPa, which is really close to bone’s one. Unfortunately, titanium and its alloys are well known for their poor machinability due to the hardness and low thermal conductivity. Machined surfaces of titanium alloys are also easily damaged (micro cracks, build-up edge, plastic deformation, heat-affected zones, and tension residual stresses) during the process. Studying process parameters is important to avoid these phenomena. The machinability of TiNb (turning, milling) has not been studied to date. Therefore, in this study, we examined the behavior of the TiNb titanium alloy for applications as a biomaterial in micro-cutting. Orthogonal cutting tests were performed on austenite and martensite states TiNb alloys and compared with Ti40 pure titanium. The aim was to evaluate the influence of the alloys and the cutting parameters on the evolution of the cutting forces, specific cutting energy, friction coefficient which are good indicators of machinability.

International audience; Modelling the physical behaviour of fibrous materials still remains a great challenge because it requires to evaluate the inner structure of the different phases at the phase scale (fibre or matrix) and the at constituent scale (fibre). X-ray Computed Tomography (CT) imaging can help to characterize and to model these structures, since it allows separating the phases, based on the grey level of CT scans. However, once the fibrous phase has been isolated, automatically separating the fibres from each other is still very challenging. This work aims at proposing a method which allows separating the fibres and localizing the fibre-fibre contacts for various fibres geometries, that is: straight or woven fibres, with circular or non circular cross sections, in a way that is independent of the fibres orientations. This method uses the local orientation of the structure formed by the fibrous phase and then introduces the misorientation angle. The threshold of this angle is the only parameter required to separate the fibres. This paper investigates the efficiency of the proposed algorithm in various conditions, for instance by changing the image resolution or the fibre tortuosity on synthetic images. Finally, the proposed algorithm is applied to real images or samples made up of synthetic solid fibres.

Bonding of parts produced by fused filament fabrication (FFF) significantly depends on the temperature profile of filaments depositing one top of each other. It is necessary to evaluate the temperature profile during fabrication of structures using both theoretical and experimental approaches. This work describes the overall heat transfer (using finite volume method) that exists in such a process by taking into account the possible phenomena that are developing during the manufacturing sequence: conduction between filaments, conduction between filament and support, and convection with the environment. Although the developed model is general and applicable to both amorphous and semi-crystalline polymers and/or composites, the recordings of temperature variation at the interface of adjacent filaments of a printed vertical wall of PLA illustrated good agreement by implementing very small K-type thermocouples in parallel. It is particularly concerning the occurrence of re-heating peaks during the deposition of new filaments onto previously deposited ones. The sensitivity of the developed code to the operating conditions is shown by variation of several parameters. This makes it easy to apply it for optimization purposes. Theoretical modeling and experimental data presented in this study help better understanding of heat transfer existing in polymer/composite additive manufacturing, and can be valuable to predict more accurately the bond quality and apply the obtained findings for further steps.