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In the past 30 years, wind turbine blades (WTB) have undergone significant development, increasing their size and introducing composites into manufacturing processes and using numerical simulation to assess their strength and structural integrity, helped increasing the number of installed wind turbine units as well as reducing the cost of wind generated energy. In this paper a DLoad subroutine was developed to assess monitor and evaluate the structural integrity of a large wind turbine blade under numerous static load scenarios. The fatigue study was carried using the finite element method, and the DLoad subroutine developed was used with ABAQUS finite Element analysis Software, and performed perfectly. The results show that the proposed layup parameters and the chosen composite materials gives to the wind turbine the desired structural strength. Furthermore, the DLoad subroutine for the fatigue study shows that the higher is the applied force the faster the blade fail. While, Hashin Criterion shows that the distribution of damage for the matrix and the fiber is all over the blade, but the failure only occurs after reaching an energy threshold which depends on the composite materials and the layup parameters used. Therefore, the chosen layup model will allow the wind turbine blade to withstand the extreme climatic conditions in the sea.

In this study various samples were fabricated by increasing the amount of CNT from 0% to 5%. The bulk mechanical properties of the samples were measured using DMA. Alternatively, the local mechanical properties were assessed using nanoindentation technique. There is a clear trend that the behavior of the material is dependent of carbon fillers before, during and after percolation threshold. The bulk mechanical properties were reduced after the percolation threshold due to CNT agglomeration. Then the samples were exposed to acid solution for one week and one month. Regardless the amount of CNT in the matrix, there is always a gradient of properties from the skin to the core of the sample. There is a net reduction of in physical properties. However, the level of degradation was a dependent of the amount of CNT in the host polymer. At higher concentration the CNTs behave as a barrier. However due to the formation of porosity around the CNT agglomerates, the acid diffusion encounters preferential path ways. . Both techniques lead to the same observation..

Composite materials are attracting increasing interest from many industrial sectors, and their use is becoming more widespread. The naval industry, for example, remains a large field of investigation for composite materials due to their mechanical properties, able to reach very interesting performance levels. Composites are often composed of plies arranged according to loading directions and forming structures called laminates; these directions can have a great effect on the structural behavior of the composite. For this, the study carried out in this article, consists in determining orientations and stacking sequences effect on the mechanical performance of a glass/epoxy composite panel, with a thickness of 8 mm containing 12 plies of the same thickness and different orientations, inclined at an angle of 10° and impacting the water at a velocity of V = 8 m/s.

Since carbon nanotubes and carbon fibers were discovered, the number of research works on these composite materials has exploded, and that’s the reason behind using them in this article as reinforcement to improve the mechanical, electrical and thermal behaviors of materials, to enable their use as Nano-sensors in several new applications. This article aims to describe the structure of these materials and their multi-functionality. An analytical estimation of physical properties was presented, using the homogenization technique. Then, a numerical study in Abaqus, to determine thickness and volume fraction effect of CNts on the behavior of composite materials.

International audience; For several decades, composite materials have been used in different applications due to their multiple advantages. It has become necessary to understand the dynamic behavior of these materials under critical loads. In-plane (IP) and out-of-plane (OP) dynamic compression tests were investigated on a cubic specimen of composite joints under low to high strain rates using the Split Hopkinson Pressure Bars (SHPB) technique. The specimens consist of two adherents (glass/polyester composite) assembled by an adhesive with different thicknesses (1 and 2 mm). During the experimental tests, the high-speed camera was used to check the damage history and the failure mechanisms on adhesively bonded composite joints. The sample surface temperatures were monitored using an infrared camera (IR). For bonding of two composite substrates, it can be noted that the thickness of the adhesive has a significant effect on the dynamic behavior and the kinetics of the damage. It has been concluded that the damage was localized at the level of the layers in the case of in-plane loading and the level of the adhesive zone in the case of out-of-plane loading. The thermomechanical behavior of cubic specimens of adhesively bonded joints subjected to dynamic compression has been studied. The results underline the sensitivity of the dynamic behavior of the adhesively bonded joints to the strain rate, the loading direction and the appearance of heat dissipation linked to the increase in temperature following the initiation of damage. This rise of temperature can dangerously approach the glass transition temperature of the matrix.

International audience; The structural design of spars for horizontal axis wind turbine blades to achieve satisfactory levels of performance starts with the knowledge of aerodynamic forces acting on the blades. The present paper proposes a comparative study of the geometries of three spars designed for a 48 m long composite blade. The spars are evaluated under compression, bending loads as well as on free vibration. Different Subroutines have been developed and coupled with Finite Element Analysis (FEA) software to analyze the mechanical performances and the qualities of each one of the three designed spars. In other words, it seeks not only to define the behavior and response of each one of the spars and the effect of composite materials on the improvement of the structure stiffness and weight, but also to determine the suitable spars type for the wind turbine blade and the results shows that the Box spars offers a compromise of the main parameters.

International audience; The first phase of this work aims to use the right additive nano-fillers choices, such as exfoliated Graphite (ExG), increasing the mechanical, electrical, and thermal performances. In this work, we are interested in quantifying the effect particles' size on a polymer matrix's performance. For this, three sets of exfoliated polymers filled with Graphite, characterized by three particle sizes, called meshes 50, 100, and 150, were investigated. In this analysis, exfoliated Graphite reinforced polymers were subjected to indentation tests to define local mechanical properties. The sample is an epoxy 862 matrix reinforced with exfoliated graphite additives. For each specific size, the additives are mixed in percentages of 0% in the act of control, 0.5%, 4%, 8%, and 16% by weight. Matching pure polymers, polymers reinforced by exfoliated Graphite have proven to have significant improvements in local elastic properties (such as modulus, hardness, stiffness, etc.). Results showed that the reinforced epoxy's local mechanical properties are affected by the size and the percentage of nano-additives. Through the inspection of the load-displacement curve, it can be concluded that the nano-additive has a significant influence on the plastic mechanical properties of the sample. Therefore, the size of nanoparticles has significantly improved in material properties.

International audience; The tidal current turbine is the most efficient way to extract energy from the sea. This system can be prone to critical loads such as impact accidental in the installation and maintenance phase. Indeed, several complex modes of damage susceptible to harming the stability of the structure are studied to conceive hybrid composite nozzles with better resistance to damage. For this reason, two scenarios of low-velocity impact of a hybrid composite nozzle (glass/carbon) were investigated. In both cases, the impact was realized in the region of the trailing edge of the nozzle, and the results obtained were compared between three different laminated. On the other hand, damage modeling was formulated using the finite element method based on the Hashin criteria. Energy conservation of the nozzle was verified to validate the numerical model. Also, the effects of the impact velocity and the panel's flexibility on the initiation and propagation of damage have been studied. Depending on the results, the stacking sequence significantly influences the formation of damage. However, the results show that the hybrid nozzle with CGG (carbon/glass/glass) stacking has a higher impact resistance compared to other laminates.

International audience; The purpose of this paper is to study the mechanical behaviour of a multi-layered composite tubular structure with various orientations subjected to internal hydrostatic pressure. The first part of this paper is devoted to studying stress analysis using the analytical approach. The 3 D analysis of the composite pipe originally made with carbon/epoxy is studied and compared with a pipe made of E-glass/epoxy; each layer is examined with five orientations. The hoop, axial, longitudinal, transversal, and shear stresses are obtained for each layer of the composite pipe simultaneously. The hybrid composite pipe is done to take advantage of the properties of each fiber and the studied hybridisation. `To validate some cases of the presented results, a numerical model is developed in ANSYS workbench software; this particular model is characterized by very close to the theoretical results. Throughout the investigation, it is observed that the behaviour of composite carbon/epoxy is the most resistant compared to glass/epoxy, and the results obtained in the case of hybrid shows that the variability of the stacking sequences generates the variation of the behaviour on composite hybrid pipe. It can be increased the design material utilisation and working pressure level by winding angle variation or hybridized between stacking sequences. The ability of this new 3 D model to simulate the stress evolution in the full-scale composite tubular structure under internal pressure events were demonstrated.

The structural, thermal, and mechanical properties of unreinforced and reinforced polylactic acid (PLA) were investigated. The PLA was a biopolymer that was reinforced with four fillers (i.e., graphene oxide (GO) and silver (Ag); vermiculite (VMT) and silver (Ag); and two organically modified vermiculites). The processing technique for the production of the composite materials were carefully planned. The PLA nanocomposites were investigated by examining their morphological aspects, changes in PLA phases and transitions and, most importantly, the effect on certain final properties. X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that the sample was completely amorphous. Thermogravimetric analysis (TGA) results indicated that the presence of reinforcing particles in the PLA matrix did not affect the thermal degradation of these composites. Furthermore, the local mechanical properties were investigated using the microindentation method to evaluate the effect of different nanofillers. Scanning electron microscopy (SEM) and a VHX-500 optical digital microscope (Keyence International, Mechelen, Belgium) were also used to examine the surface morphology of the PLA polymer composites. These results can help to select suitable fillers to enhance the PLA performance of biopolymers.

International audience; Tidal current turbine is one of the innovative and emerging technologies of marine renewable energies because it offers constant and predictable energy source that can be very beneficial, especially for commercial scale production of electrical power. Hydrofoils (HF) are essential elements of tidal current turbine (TCT) and should be properly designed as they play a vital role in improving the turbine output and providing adequate resistance to the blade structure. In connection with the hydrofoil designs, it is noteworthy that the primary objectives in their designs are to increase the coefficient of lift and to reduce the coefficients of drag and pitching moment, thus delaying the cavitation phenomenon. In this paper, the technology developments of the hydrofoil designs used in the horizontal axis TCT industry are reviewed, including the hydrodynamics design and the mechanical structure design. Besides, an up-todate review and the newest achievements of marine TCT technologies with their developing histories are further explored. Included are also reviews on the numerical models used to assess the performance of TCT and optimization methods applied to design the hydrofoils. This in turn significantly contributes to a better knowledge on the recent designs of TCT hydrofoils for the researchers working in the marine turbine energy domain. Such information could also have important implications in the design of more sophisticated hydrofoils for the exploitation in diverse tidal current energy technologies for reaching a sustainable future.

International audience; Despite having vast structural applications, Composites are not exempt from limitations and are susceptible to deforming during operation. Therefore, it is essential to develop in-situ monitoring systems to avoid their catastrophic failure or high repairing cost. So, the objective of this study was to monitor the deformation behavior of composites subjected to cyclic flexural deformation in real-time using a Nylon/Ag fiber sensor. Nylon/Ag fiber sensor was integrated at different direction i.e. 0°, +45°, 90°, -45° gradually between each ply of the composite specimens which were then machined in star shape where each leg signified the direction of the sensor. These specimens were then tested under cyclic flexural deflection at the strain rate of 2mm/min for 10 cycles. Mechanical results of composite specimens and electrical response of each Nylon/Ag sensor fiber showed excellent repeatability however, each Nylon/Ag fiber sensor showed a specific resistance behavior because of their respective position. The increase or decrease in the resistance of the fiber sensor signified the presence of tensile or compressive strain respectively and the intensity of the signal quantified the amount of deformation. The results confirmed that the fiber sensor showed good potential as flexible sensor reinforcement in composites for in-situ monitoring, identification and quantification of the deformation.

International audience; In this work, two desalination systems combined with a solar energy cycle, MED-PF and MED-PF-TVC are analyzed and evaluated thermo-economically. Solar energy is directly transferred from the solar collector field via the evaporator heat exchanger to MED-PF. In the second technique, the thermal energy produced is transmitted to the steam ejector of the MED-PF-TVC. The comparisons are handled according to 5000 m3/day of distilled product as a case study. A reduction in consumption and specific energy costs is possible due to the reduction in the value of the compression ratio and the increase in the number of evaporators.

International audience; Tidal energy has clear potential in producing large amounts of energy as the world's capacity exceeds 120 GW. Despite being one of the oldest renewable energy sources exploited by man, the technology is still in its pre-commercialisation stage and so lags behind other renewable sources such as wind and geothermal energy in terms of development and energy produced. One of the emerging energy extraction technologies in the tidal energy field is the Horizontal Axis Hydrokinetic Turbine (HAHT) which harness tidal stream energy the same way Horizontal Axis Wind Turbine (HAWT) extract energy from the wind. While HAHT has been the topic of many researches over the past decade, design of hydrofoils plays a vital role in increasing the structural strength of the blade and maximizing the output of the marine current turbines. In this context, a numerical investigation is conducted in this research in which new hydrofoil for marine current turbines underwater conditions was designed and evaluated. The turbine blade is designed using XFLR5 code and QBlade which is a Blade-Element Momentum solver with a blade design feature. Then, the hydrodynamic performance of hydrofoil was tested using Computational Fluid Dynamics (CFD) consisting of lift and drag coefficients, and velocities distribution. The results showed that the new design of the hydrofoil of marine current turbine blade maintained a CPower value of 50% more from normal range at the TSR 5 to 9 and 51% more at TSR = 6,5 in the performance curve.

International audience; Throughout their operating life, offshore wind turbine blades are subjected to considerable wind forces. In order to ensure their durability and strength the intrados and extrados are bounded around spars, which are the skeleton that provide the necessary rigidity to the blade. Wind turbine blades are complex structures given the various scientific fields involved in their study, from aerodynamic to composite fatigue and failure analysis. Wind turbine blade is under coupled process of forces, so when we have the same natural frequency for the blade and exciting forces, the resonance is occurred. Which make the modal analysis of the blade of great importance, hence the scope of the present work, which deal with determining, the natural modes shapes and frequencies of three spars forms during free vibration, as well as for a 5MW horizontal axis floating wind turbine blade, to prevent and avoid resonance effect, using ABAQUS Finite element analysis software. The results show that the resonance effect does not occur for the blade and the proposed layup model provide enough resistance to the structure.

The covid-19 outbreak has caused a shortage of masks and other healthcare products for the general public around the globe. In addition, it has also affected the supply of personal protective equipment (PPE) used by healthcare services because of a sudden increase in their demand. This significant disruption in the global supply chain of these products resulted in, leaving many staff and patients without protection. The additive manufacturing (AM) industry is going through extraordinary times and can provide emergency responses to help deal with the global crisis caused by the COVID-19 pandemic. The objective of the present work is therefore to perform an up-to-date review to determine the capacity of AM to provide exclusive benefits for the medical healthcare supplies sector to fight this current situation. In this review, it is found that AM technology has proved that it can be used as a volume manufacturing technology for the ongoing crisis. However, the standardization and certification are appeared to represent the main challenges for adopting the AM in healthcare against COVID-19. Furthermore, additively manufactured materials for medical applications must be developed for medical environments. Most printed medical products for COVID-19 require biocompatibility evaluation and shall prove their ability to sterilize. Finally, this review concluded that AM technology can fulfill the requirements of face masks and ventilator parts for healthcare systems for proper controlling and treating of COVID-19 patients when the safety and efficacy of these devices are ensured.

Pressurized hybrid composite pipe structures, produced by filament wound subjected to impact loads , were numerically investigated. A combined 3D-FE Model based on the use of interlaminar and intralaminar damage models is established. Intralaminar damages such as matrix cracking and fibre failures are predicted using 3D Hashin criteria, whereas interlaminar damage (delamination) was evaluated using cohesive zone elements. The damage model was coded and implemented as a user-defined material subroutine (VUMAT) for Abaqus/Explicit. Numerical results in the form of contact force, displacement and energy dissipated compare well with the experimental results. Predicted matrix damage in each cross-ply of hybrid composite pipe and delamination onset were also presented in this paper. The ability of this new 3D model to simulate the damage evolution in the full-scale pressurized hybrid composite pipe under low-velocity impact events were demonstrated throughout comparison with existing experimental results published.

Biocomposites based on thermoplastic polymers and natural fibers have recently been used in wind turbine blades, to replace non-biodegradable materials. In addition, carbon nanofillers, including carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are being implemented to enhance the mechanical performance of composites. In this work, the Mori–Tanaka approach is used for homogenization of a polymer matrix reinforced by CNT and GNP nanofillers for the first homogenization, and then, for the second homogenization, the effective matrix was used with alfa and E-glass isotropic fibers. The objective is to study the influence of the volume fraction Vf and aspect ratio AR of nanofillers on the elastic properties of the composite. The inclusions are considered in a unidirectional and random orientation by using a computational method by Digimat-MF/FE and analytical approaches by Chamis, Hashin–Rosen and Halpin–Tsai. The results show that CNT- and GNP-reinforced nanocomposites have better performance than those without reinforcement. Additionally, by increasing the volume fraction and aspect ratio of nanofillers, Young’s modulus E increases and Poisson’s ratio ν decreases. In addition, the composites have enhanced mechanical characteristics in the longitudinal orientation for CNT- reinforced polymer and in the transversal orientation for GNP-reinforced polymer.

The high mechanical performance of filament wound hybrid composite pipes can be adversely affected by their low resistance to accidental impact. Loads of dynamic origin are dangerous and cause consequences on the operation of pipes because the damage is often not detected and can affect the structural integrity of composite pipes. In this work, a finite element (FE) model of pressurized hybrid composite pipe is developed and performed to predict the damage initiation and evolution under low-velocity impact through simulations with ABAQUS/Explicit. Hashin’s failure theory is used as failure criterion. At the first stage, load–time histories, and impactor displacement time limits are estimated in an FE model. The numerical results are confronted with the experimental values published in the literature. Once the model was validated, damage initiation and propagation were analyzed, where it is observed that damage mainly occurs by matrix cracking, damage evolution in the matrix in tension, compression and shear are presented and discussed in detail.

International audience; The 3D printing technology used for small tidal and wind turbines has great potential to change and overcome certain weaknesses in traditional manufacturing techniques. In rural areas and isolated communities, small turbine systems could be locally fabricated and assembled by using additive manufacturing machines and also can be employed to decrease residential energy consumption. The objective of the paper is to study the thermomechanical performance of 3D printing of a small-scale tidal turbine blade and their process using Digimat-AM because more research efforts are needed in this area. In this work, the tidal turbine blade is printed by using the selective laser sintering (SLS) method with polyamide 12 (PA12) and polyether ether ketone (PEEK) polymers reinforced by carbon beads (CB) and glass beads (GB). This research examines conceptual considerations of small tidal turbines including material properties and aerodynamic parameters. Once the finite element evaluation has been completed, the deflection, residual stresses, temperature distribution, and the deformed blade or warpage can be obtained. It is concluded that PA12-CB has warpage higher than PA12-GB by 3.78%, and PEEK-CB has warpage lower than PEEK-GB by 8.4%. Also, the warpage of PA12-CB is lower than PEEK-CB by 10.31%, and the warpage of PA12-GB is lower than PEEK-GB by 20.95%. Therefore, the lowest warpage is observed for PA12-GB. Finally, the results showed that 3D printing presents an excellent opportunity in the design and development of tidal energy systems in the future.

International audience; Smart textiles have generated significant importance because of the advent of portable devices and easy computing, however, they did not replace the conventional electronics on the whole however, this development is now advanced to the fabrication of wearable technologies. The aim of this research paper was to develop a flexible microscale conductive fiber for real-time strain monitoring applications. This conductive fiber was developed by depositing conductive silver (Ag) nanoparticles on the surface of Nylon-6 polymer yarn by electroless plating process to achieve smallest uniform coating film over each filament of the Nylon yarn without jeopardizing the integrity of each material. The sensitivity of this Nylon/Ag conductive fiber was calculated experimentally and gauge factor was found to be in the range of 21-25 which showed that it had high sensitivity to the applied strain. Then, Nylon/Ag conductive fiber was tested up to fracture under tensile loading and a good agreement between mechanical and electrical response was observed with reproducibility of the results. The results demonstrated the way to design a cost-effective microscale smart textile for strain monitoring. This Nylon/Ag conductive fiber can then be used in a wide range of high strain applications such as in-situ structural health monitoring or for medical monitoring because of their high sensitivity, flexibility, and stability.