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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.

Discharge Machining is a non-traditional machining technique and usually applied for hard metals and complex shapes that difficult to machining in the traditional cutting process. This process depends on different parameters that can affect the material removal rate and surface roughness. The electrode material is one of the important parameters in Electro –Discharge Machining (EDM). In this paper, the experimental work carried out by using a composite material electrode and the workpiece material from a high-speed steel plate. The cutting conditions: current (10 Amps, 12 Amps, 14 Amps), pulse on time (100 µs, 150 µs, 200 µs), pulse off time 25 µs, casting technique has been carried out to prepare the composite electrodes copper-sliver. The experimental results showed that Copper-Sliver (weight ratio70:30) gives better results than commonly electrode copper, Material Removal Rate (MRR) Copper-Sliver composite electrode reach to 0.225 gm/min higher than the pure Copper electrode. The lower value of the tool wear rate achieved with the composite electrode is 0.0001 gm/min. The surface roughness of the workpiece improved with a composite electrode compared with the pure electrode.

International audience; Generally, when marine vessels encounter the water surface on entry and subsequently re-enter the water at high speed, this can subject the bottom section of the vessels to high hydrodynamic loads, especially over very short durations. This phenomenon generates high hydrodynamic loads, which can cause a catastrophic failure in the structure. In contrast, the interaction between deformable structures and free water surface can be modified the fluid flow and changed the estimated hydrodynamic loads comparing with rigid body, due to appearance of hydroelastic effects. These effects are considered active challenge areas in structural ship design. This work presents an experimental study of the water impact for composite laminate wedge at different constant entry velocities. The aim of this study is to investigate the dynamic structural response of panels and predicts the hydrodynamic loads to meet the specific requirements of marine vessels. In order to better describe hydroelastic influence, two composite panels with different thicknesses namely 8 mm and 13 mm are subjected under constant impact velocities of 4, 6 and 8 m/s with the deadrise angle of 10 degrees. The obtained experimental results were indicated that more flexible panels had a higher peak force and significant dynamic noise compared with higher stiffness panels. In addition, the maximum deformation occurred in the centre and close to the chine edge of the panel due to changes in local velocity and local deadrise angle. For this reason, special attention requires in both design phase and operation phase.

International audience; In this work, polymer laminated composites based on Epon 862 Epoxy resin, T300 6 k carbon fibers and carbon nanotubes (CNTs) were tested with the aim to elucidate the effect of CNTs on impact properties including impact force and capacity to absorb impact energy. The polymer matrix was reinforced by a random distribution of CNTs with fraction ranging from 0.5 to 4.wt%. Composite panels were manufactured by using the infusion process. Taylor impact test was used to obtain the impact response of specimens. Projectile manufactured from a high strength and hardened steel with a diameter of 20 mm and 1.5 kg of mass was launched by a compressed gas gun within the velocity of 3 m/s. Impact force histories and absorbed energy of specimens were recorded. A numerical model was employed to simulate the impact performance. This model has been accomplished by forming a user established subroutine (VUMAT) and executing it in ABAQUS software. Finally, the effect of CNTs amount on dynamic properties of laminated composites was discussed.

International audience; Slamming is a dynamic phenomenon in which a high magnitude pulse peak pressure occurs in a short time duration when the bottom structure of a ship impacted against the sea surface. This phenomenon can cause damage in the structure due to fluid-structure interaction (FSI) thus, plays a vital role in designing and manufacturing of ships for naval applications. In this paper, high performance sandwich structure, having many opportunities and challenges for the marine structural design, were studied experimentally using a high-speed shock test machine to examine the water entry problem. In addition, a velocity control system was used to calibrate and preserve the approximately uniform velocity throughout the slamming impact. Sandwich panels with different thicknesses i.e. 27 mm and 37 mm therefore, having different stiffness's were exposed under constant impact velocities of 6 and 8 m/s at the deadrise angle 10°. Experimental results were then compared and verified by the numerical investigation based on explicit Smoothed Particle Hydrodynamics (SPH) method. This study focuses on the overall structural response, deformation, and hydrodynamic response of the structure during the dynamic impact designed for naval applications.

Springback is considering as one of the most common problems in metal forming processes, which poses an inaccuracy of product angle during assembling of parts. The estimation of the springback is difficult to predict for formed parts, since it depends on many factors such as the mechanical properties, the sheet thickness and the die angle. In this work, experimental investigation for different thickness and holding time have been studied and analysed. Samples of (Aluminium, brass, and C1004 Steel) specimens with 80 mm length, 50 mm width and 2, 3 and 6mm of thickness selected in this study. Using bending die with angle value (730 and 900) pulled three pieces of each different holding times. Three pieces for each metals were hold with three times (2, 4, 6 minutes). The results show that in a given thickness configuration, the springback reduced with increasing of the punch hold time for all thicknesses selected.

Statistical process control techniques are extensively used to describe statistics dada to monitor and satisfy the specifications of product and process. This approach capable to decide the amount of the variations in the case of frequent mistakes of the production process. Consequently, this approach can be monitored the production process and keep sure that the production locates inside this acceptable range and indicate directly that the process became under control. This means that the SPC considered an active method to monitor, examine and control variation in processes. In this paper, a computerized system is constructed to determine the manipulate charts and process capability which representing the predominant tool to monitor the rotational mechanical parts product machined by turning machine. A critical quality characteristic (variables) used in the work is dimensions to be measure and examining this process.

Composite materials are used in many marine structures such as renewable marine energy conversion systems because of their fairly good mechanical properties and especially their low densities compared to traditional materials. The most advanced features currently available in finite element (FE) Abaqus/Explicit have been employed to simulate the behavior of the composite nozzle under hydrodynamic and impact loading. A hydrodynamic analysis was considered to design the nozzle turbine and the hydrodynamic pressure obtained was then implemented as boundary conditions to a FE code. The goal of this article is to evaluate the durability of composite materials of a ducted tidal turbine under critical loads (hydrodynamic and hydrostatic pressures) with the implementation of a failure criterion using the finite element analysis (FEA). The mechanical behavior was analyzed for two materials (Carbon–epoxy/ Glass–polyester). This has been accomplished by forming a user-created routine (VUMAT) and executing it in the ABAQUS software. Keywords: Marine composite structures, Ducted tidal turbine, Finite element analysis, VUMAT

International audience; Delamination progressive in carbon nanotubes reinforced composites under applied Short Beam Shear test was studied. Experimental characterization was carried out using ASTM D2344 standard norms for different carbon nanotubes mass fractions ranging from 0 to 4%. Failure modes and the delamination were experimentally characterized by scanning electron microscopy and Kayence microscopy to assess the failure behavior. The numerical model was created under ABAQUS software based on the cohesive zone models. The numerical model was formulated according to the damage mechanics. In these models, the cohesive interaction was implanted between elements of each fabric ply to control the initiation and the propagation of the delamination for different carbon nanotubes fractions. The force–displacement curves vs. carbon nanotubes added were obtained for the numerical model and shown to be in good agreement with the experimental data. The effect of carbon nanotubes on the progressive delamination was elucidated.

International audience; Polymer composite pipes can be exposed to the thermomechanical loading due to hot and cold fluid flow, which results in the degradation of their properties. In this paper, effect on mechanical properties of composite pipes under different temperatures ranging from −40 to 80 °C is studied experimentally. The composite pipes consist of glass/epoxy tubes having 86 mm internal diameter and 6.2 mm of thickness with ±55° glass filament winding, intended for offshoring applications. TEMA TTC machine and split disk are used for uniaxial tensile tests and the thermal aging is considered with the help of SERVONTAN climatic chamber. Thermal aging is carried out on these specimens in climatic chamber for 8 h at different temperatures and then uniaxial test is performed. Experimental results have shown degradation in the mechanical properties of polymer pipes with an increase in the temperature. For pipes at colder temperature, the rigidity of composite increases progressively with the temperature and results in drastic decrease in the displacement at break. Also there is a decrease in the yield stress and an increase in yield strain with an increase in the temperature.

International audience; The interaction between deformable structures and free water surfaces can modify the fluid flow and change the estimated hydrodynamic loads in relation to rigid bodies, due to the appearance of hydroelastic effects. The flexibility and damage failure modes in composite materials introduce additional complexity for predicting hydrodynamic loads when interactive with water. This is considered to be a key challenge when using these materials in marine applications. Therefore, particular attention should be paid to this fact in the design phase and over their period of use. The aim of this work is to study the structural behavior and the effect of the flexibility of composite panels on hydrodynamic loads and the dynamic deformation response experimentally and numerically. To study these effects, composite panels with two different rigidities were subjected to various impact velocities and investigated. It should be noted that all the panels tested at a10° deadrise angle. A high velocity shock machine was used to maintain constant velocity during water entry at impact velocities of 4 m/s, 6 m/s, 8 m/s and 10 m/s. The general analysis of experimental results indicated that compared to the higher stiffness panels, the more flexible panel has a higher peak force as velocity increases. This has been attributed to the change in local velocity and local deadrise angle along the water-panel interface. The numerical model was implemented based on the Coupled Eulerian–Lagrangian Model (CEL) built-in Abaqus/Explicit finite element software. The numerical results showed a good agreement compared with experimental data for both the hydrodynamic force and the deformation response. These quantitative structural-loading data can provide a clear guide for maritime ship design.

International audience; The deformable composite structures subjected to water-entry impact can be caused a phenomenon called hydroelastic effect, which can modified the fluid flow and estimated hydrodynamic loads comparing with rigid body. This is considered very important for ship design engineers to predict the global and the local hydrodynamic loads. This paper presents a numerical model to simulate the slamming water impact of flexible composite panels using an explicit finite element method. In order to better describe the hydroelastic influence and mechanical properties, composite materials panels with different stiffness and under different impact velocities with deadrise angle of 100 have been studied. In the other hand, the inertia effect was observed in the early stage of the impact that relative to the loading rate. Simulation results have been indicated that the lower stiffness panel has a higher hydroelastic effect and becomes more important when decreasing of the deadrise angle and increasing the impact velocity. Finally, the simulation results were compared with the experimental data and the analytical approaches of the rigid body to describe the behavior of the hydroelastic influence.

International audience; The use of composite materials begin to normalize in various sectors, however, these structures are very susceptible to degradation of their properties and consequently a catastrophic failure. The response of deformable composite subjected to water-entry impact can cause a phenomenon called hydro-elastic effect due to water-flexible laminate interaction. This phenomenon may be large enough to cause the damage in composite panels. This paper employs the finite element method to simulate the behavior of composite wedges under slamming impact with presence of damage. To investigate this situation, the hydro-elastic influence has been analysis as both kinematic effect due to deflection of the composite panel and dynamic effect caused by the interaction between the water and the structure. On the other hand, damage modeling was formulated based on continuum damage mechanics for intra-laminar damage. A user-defined material subroutine VUMAT has been incorporated into explicit Abaqus FE software to enhance the damage simulation, which includes Hashin criteria for degradation of the panel stiffness with failure onset criteria and fracture mechanics. To reinforce the methodology adopted, numerical results are compared with the previous experimental data. A good agreement was observed. Effects of impact velocity and the panels flexibility on the damage have been investigated.

International audience; Sandwich structures have been widely used in marine applications due to their properties such as high weight/strength ratio. In contrast, the failure mechanism of these structures has a significant effect on the local and global dynamic responses. In the present study, sandwich panels with polymeric skins and PVC foam cores subjected to slamming impact are investigated experimentally and numerically. A high speed shock machine is used to keep approximately a constant velocity during the impact event. The dynamic resistance was analysed in terms of hydrodynamic loads, dynamic deformation and failure mechanisms for different impact velocities. On the other hand, the slamming model was implemented in Abaqus/Explicit software based on Coupled Eulerian Lagrangian model approach. In addition, different damage modes are incorporated in the numerical model, including the intralaminar, debonding in skin/core interface, and core shear to cover all possible damage modes throughout structures. Two failure criteria (Hashin criteria for the laminate composite and Christensen criteria for the core in sandwich structure) are defined and integrated into VUMAT sub-routine. In addition, the cohesive zone model is used to predict the debonding skin/core. A good agreement in both hydrodynamic loads and damage prediction were found between numerical and experimental results.