Laboratory of Mechanics Physics of Materials

The incorporation of nanofillers makes it possible to permanently modify the properties of the adhesive. Nanoparticles with structures of less than 100 nanometers can be incorporated in suitable amounts up to 30% by volume into liquid adhesives without significantly changing the rheology. Fine and nanometric particles of Si02 are now increasingly incorporated into aqueous adhesive dispersions. The objective of this study is to analyze numerically by the three-dimensional finite element method, the intensity and distribution of von Mises, shear and peeling stresses in a nanostructured adhesive joint which ensures the assembly of two plates in Aluminum alloy 2024-T3. This adhesive is epoxy DER 331 in nature, filled with spherical silica nanoparticles (SiO2) of same size, the content of which varies from 0% to 30%. These silica nanoparticles are injected into the adhesive in the liquid state in a homogeneous way in order to see their effects on the mechanical behavior of the epoxy-nanosilica composite. The stresses are also evaluated according to the length of the adhesive lap and its thickness when crossing the crack front. The results obtained numerically by the finite element method show that the addition of nanoparticles in the epoxy matrix with ductile behavior contributes to the improvement of the mechanical properties of the epoxy-nanosilica composite, by increasing its mechanical resistance to the propagation of cracks. The presence of nanoparticles makes it possible to slow down the propagation of the crack.

The present work analyzes the free vibration response of functionally graded (FG) plates made of Aluminum (Al) and Alumina (Al2O3) with different porosity distributions, as usually induced by a manufacturing process. The problem is tackled theoretically based on a higher-order shear deformation plate theory, while proposing a Navier-type approximation to solve the governing equations for simply-supported plates with different porosity distributions in the thickness direction. The reliability of the proposed theory is checked successfully by comparing the present results with predictions available from literature based on further first-order or higher-order theories. A large parametric study is performed systematically to evaluate the effect of different mechanical properties, such as the material indexes, porosity volume fractions, porosity distributions, and length-to-thickness ratios, on the free vibration response of FG plates, as useful for the design purposes of most engineered materials and composite applications.

This paper presents an analytical solution based on higher order shear deformation plate theory method for investigation of vibration behavior of a functionally graded plate. Here, the types of even porosity distribution are considered. It has been observed that during the manufacture of (FGP), micro-voids and porosities can occur inside the material. Hamilton's principle will be used herein to determine the equations of motion. Since, the plate are simply supported the Navier procedure will be retained. Then the proposed numerical approach is implemented to achieve the frequency parameters of the plate. In this work, a detailed numerical study is conducted to examine the effects of porosity coefficient on fundamental frequencies of the plate for different thickness ratios, geometric ratio and material properties and material power index.

After trans-tibial amputation (TTA) the patient needs prosthesis to maintain mobility, unfortunately, people with this type of amputation often experience skin degradation due to the pressures and shear stresses in the stump-prosthesis interface. The purpose of this study was to reduce the contact pressures and shear stresses at the stump-prosthetic interface In order to design a satisfactory and comfortable prosthesis for the patient. To achieve this we built a trans-tibial finite element model (FE) (stump, socket, and bone, liner) to investigate the stresses at the stump-prosthetic interface. This (FE) model allows comparing the effect of three types of the prosthetic liner (gel liner, Polyurethane foam liner, liner with two layers of foam (foam polyurethane - natural rubber latex foam)) on the contact pressure and shear stress at the stump-prosthetic interface. By modifying the liner thickness (from 3 to 9 mm) in all three cases, one also aim to determine the effect of liner thickness variation on the distribution and intensity of the contact pressure and the shear stress at the stump-prosthetic interface. The comparison of the stresses and their distribution at the stump-prosthesis interface in each case will allow us to determine the optimal prosthesis. The liner with two layers of foam (polyurethane - latex) achieves the best balance between the ability to support the patient’s weight and low stress values at the stump-prosthetic interface, the contact pressure and shear stress values have not been exceeded 42.12 kpa and 15.4 kpa. In general, it can be said that the thickness of the liner was effective in reducing the stresses at the stump-prosthetic interface, in all three cases of liner.

The repair technique has presented its effectiveness in the reduction of the stresses at the level of stresses concentration areas. The search for a patch and suitable adhesive for a good transfer of load has pushed researchers to develop many ideas, which relate the form, the nature, the stacking sequence of the patch and the adhesive type to give a better combination of choice between the patch and the adhesive. Our work fits in this context; the objective is to analyze by the method of finite elements the behavior in the rupture of a damaged plate in the presence of defect of bonding. The analysis of J-Integral and stresses in the tow substrates adhesive and patch shows clearly that their values depends strongly on the position of the default essentially when it’s located close to the free edge of the free edge of the adhesive or the crack.

This study investigates the incorporation of algae-based activated carbon into polyurethane foam to improve a biocomposite for gasoil sorption. The biocomposites were thoroughly analyzed using various techniques to examine the properties of both the blank foam and the algae activated carbon foam with a carbon content of 4.41 mass% and particle diameter of 500 µm. These techniques included Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), and density analysis. The TGA analysis revealed that the biocomposites had an impact on the onset temperature (Tonset) of the foams. Higher concentrations of the biocomposites resulted in a decrease in Tonset from approximately 310 °C in the blank foam (PUF0) to 300 °C in the composite (PUF3B). The final residue percentage also decreased from around 20% in PUF0 to 10% in PUF3B. Density analysis showed that the apparent density of the foam increased from 0.016 g/cm3 in the blank foam to 0.020 g/cm3 in the biocomposite (PUF3B), while the real density slightly decreased from 0.092 g/cm3 to 0.076 g/cm3, indicating a reduction in overall porosity from 82.5% to 74.4%. All foams that were modified showed an increase in their ability to absorb gasoil in a PUF/gasoil/water system. The optimized biocomposite (PUF1B), with 1.14 mass% of 500 µm algae carbon, displayed the highest sorption capacity, starting at approximately 50 g/g at 1.5 h and increasing to 53 g/g over 72 h. The analysis of adsorption kinetics revealed that by utilizing adsorption isotherms, particularly the Langmuir isotherm, a more accurate fit to the data was achieved. This allowed for the prediction of the maximum gasoil adsorption capacity. This study aims to further develop, analyze, and utilize biocomposites made from algae-based activated carbon and polyurethane. These materials offer a sustainable and environmentally friendly approach to cleaning up oil spills.

PMMA has important micro structural heterogeneities such as cavities, and its elastic behavior is greatly affected by the presence of defects that may imply its weakening and cause failure. In areas of high concentrations of stress and due to the presence of cavities, micro cracks appear after crushing cavities due to patient movements, and grow and weld to each other until they form a macro     fissure that propagates until the total removal of the prosthesis.. In this study, the existence of a crack emanating from  a cavity with a diameter of 0.7 mm was assumed; our assessment takes into account two parameters, the position of the crack in the cement and we calculated the stress intensity factor (SIF) in the proximal part of orthopedic cement.

In this paper, the effect of corrosion on the performance of the bonded composite patch repair in aluminum alloy A5083 marine structure was investigated using three dimensional finite element methods. To this end, two patches made in carbon/epoxy and boron/epoxy, bonded on corroded plates with and without crack, were tested under different applied loads. The effect of both corrosion and cracked materials on the damage of the adhesive FM73, was also highlighted. The obtained results show that, the corrosion has a significant effect on the quality repair performance. Indeed, it is proved that, the rate of damage increases with the increase of the applied load, and is more significant in the case of plates cracked and repaired by carbon/epoxy patch. Hence, the best performances were obtained using boron/epoxy patches

Abstract In this work, the finite element method was used to determine the stress intensity factors as a function of crack propagation in metal matrix composite structure, A three-dimensional numerical model was developed to analyze the effect of the residual stresses induced in the fiber and in the matrix during cooling from the elaboration temperature at room temperature on the behavior out of the composite. Added to commissioning constraints, these internal stresses can lead to interfacial decohesion (debonding) or damage the matrix. This study falls within this context and allows cracks behavioral analysis initiated in a metal matrix composite reinforced by unidirectional fibers in ceramic. To do this, a three-dimensional numerical model was analyzed by method of finite element (FEM). This analysis is made according to several parameters such as the size of the cracking defects, its propagation, its interaction with the interface, the volume fraction of the fibers (the fiber-fiber interdistance), orientation of the crack and the temperature.

This paper introduces a numerical methodology for classifying and identifying types of bio-based materials through experimental thermal characterization. In contrast to prevailing approaches that primarily focus on thermal conductivity, our characterization methodology encompasses several thermal parameters. In this paper, the physical characteristics of seven types of bio-based concrete were analyzed, focusing on the thermal properties of palm- and esparto-fiber-reinforced concrete. The proposed method uses artificial intelligence techniques, specifically the k-means clustering approach, to segregate data into homogeneous groups with shared thermal characteristics. This enables the elucidation of insights and recommendations regarding the utilization of bio-based insulation in building applications. The results show that the k-means algorithm is able to efficiently classify the reference concrete (RC) with a performance of up to 71%. Additionally, the technique is more accurate when retaining only six centroids, which, among other things, allows all the characteristics associated with each type of concrete to be grouped and identified. Indeed, whether for k clusters k = 7 or k = 5, the technique was not able to predict the typical characteristics of 2% or 3% esparto concrete (EC).

The contact pressure at the socket–residual limb interface is the most critical parameter for evaluating the comfort of a leg prosthesis. Experimental studies have analyzed this parameter for typical postures and during walking on a flat surface of an amputee; however, experimental tests require a real socket prototype equipped with transducers. To optimize socket design, this work presents a virtual approach based on a digital avatar of a patient wearing a lower limb prosthesis. Our study integrates two different types of simulations: the first concerns the femur with an implant, the second without an implant, and includes the evaluation of pressure at the socket–residual limb interface using finite element analyses (FEA). The objective of this study is to understand the distribution of loads and stresses at the interface between the residual limb and the prosthesis. The lower contact pressure is represented by CPRESS, while CSHEAR1 is the frictional shear stress component in the first local tangent direction, and CSHEAR2 is the frictional shear stress component in the second local tangent direction.

C Composite materials are most often used for lengthier and thin structures susceptible to buckle. The optimization is often carried out taking into consideration the resistance to buckling and tensile loads for minimum displacement i.e maximization of the tensile load for composite assembly joint. It well known that nowadays that composite material in structural mechanics is widely used in many industrial sectors such as in aerospace and aeronautic, automobile, marine  industries as well as in and civil engineering. Composite materials are attractive due to their advantages and performance i.e: lighter weights, high resistance to thermal and mechanical loads, resistance to corrosion and wear. In this paper an investigation is focused on the problem of hybrid assembly joint (bolted –bonded) composite structures. The aim is the optimization of the main influencing parameters. A bonded assembly has only one advantage which is its lightness; on the other hand bolted assembly has the inconvenient of increasing the weight of the structure and stress concentrators. In practice certain structural designs require the use of hybrid assembly for safety and reliability. The objective of this study is to optimize the influencing factors using both Genetic Algorithm and design of experiments for high mechanical performance of hybrid composite assembly.

In this investigation, fatigue criterion was established to predict crack-initiation at the tip of a notch in aged hardening aluminum alloy. This criterion was used to predict the residual lifetime in aeronautical structures using concept of local stress at notch and subjected to constant amplitude loading characterized by mean stress. Charpy V-notch specimens were taken from sheet plate and the notch radius accurately machined at value of 0.2mm. The local stresses were determined numerical and validated analytically. In experimental investigation, the V-notched specimens were loaded in four point bending fatigue with a load ratio R=0.1 and variation in amplitude loading.

Bone is a living material with a complex hierarchical structure that gives it remarkable mechanical properties. The bone undergoes constant mechanical and physiological stress, so its quality and its resistance to fracture evolve constantly over time through the process of bone remodelling. Bone quality is not only defined by bone mineral density but also by mechanical properties as well as micro architecture. The aim of this work is to model the fracture of the femur bone under a quasi-static and dynamic solicitation in order to create a digital model simulating the fractures of this element due to an accident. This modelling will contribute to improve the design of the means of transport to bring a better security to the passages. To achieve this goal, the modelling by the finite element method is performed to study the mechanical behaviour of bone structure and predict femur fractures.

PMMA has important micro structural heterogeneities such as cavities, and its elastic behavior is greatly affected by the presence of defects that may imply its weakening and cause failure. In areas of high concentrations of stress and due to the presence of cavities, micro cracks appear after crushing cavities due to patient movements, and grow and weld to each other until they form a macro     fissure that propagates until the total removal of the prosthesis.. In this study, the existence of a crack emanating from  a cavity with a diameter of 0.7 mm was assumed; our assessment takes into account two parameters, the position of the crack in the cement and we calculated the stress intensity factor (SIF) in the proximal part of orthopedic cement.