Fodil Meraghni

Bio: Fodil Meraghni is an academic researcher from University of Lorraine. The author has contributed to research in topics: Materials science & Finite element method. The author has an hindex of 29, co-authored 127 publications receiving 2296 citations. Previous affiliations of Fodil Meraghni include Georgia Tech Lorraine & Arts et Métiers ParisTech.

Mechanical behaviour of cellular core for structural sandwich panels

Abstract: This paper deals with the analysis of the mechanical properties of the core materials for sandwich panels. In this work, the core is firstly a honeycomb and secondly tubular structure. This kind of core materials are extensively used, notably in automotive construction (structural components, load floors...). For this study, three approaches are developed: a finite element analysis, an analytical study and experimental tests. Structural members made up of two stiffs, strong skins separated by a lightweight core (foam, honeycomb, tube...) are known as sandwich panels. The separation of the skins by the core increases the inertia of the sandwich panel, the flexure and shear stiffness. This increase is obtained with a little increase in weight, producing an efficient structure to resist bending and buckling loads. A new analytical method to analyse sandwich panels core will be presented. These approaches (theoretical and experimental) are used to determine elastic properties and ultimate stress. A parameter study is carried out to determine elastic properties as a function of geometrical and mechanical characteristics of basic material. Both theoretical and experimental results are discussed and a good correlation between them is obtained.

Multiscale fatigue damage characterization in short glass fiber reinforced polyamide-66

Abstract: This paper aims at studying fatigue damage behavior of injection molded 30 wt% short glass fiber reinforced polyamide-66 composite (PA66/GF30). The evolution of dynamic modulus, hysteresis area, cyclic creep and temperature during fatigue tests were analyzed and discussed. Damage analyses by X-ray micro-computed tomography ( μ CT) technique on interrupted fatigue tests at several percentages of total fatigue life were performed to further understand the damage mechanisms and evolution during fatigue loading. It can be observed that experimental results related to the evolution of dynamic modulus, strain, temperature and energy dissipation are important and consistently complement each other for damage evaluation of PA66/GF30. During fatigue loading, diffuse damage occurs over the entire specimen though the damage does not necessarily exhibit the same level between different locations inside the specimen. The μ CT analysis of voids characteristics demonstrates that the damage continuously increases during fatigue loading. The damage is developed notably along fiber interface in the form of fiber/matrix interfacial debonding.

In situ damage mechanisms investigation of PA66/GF30 composite: Effect of relative humidity

Abstract: Damage mechanisms of injection molded polyamide-66/short glass fiber 30 wt% composite (PA66/GF30) were analyzed using in situ SEM mechanical tests on specimens conditioned under three relative humidity contents (RH = 0%, 50% and 100%). The validity of these in situ analyses was confirmed by Xray micro-computed tomography (mu CT) observations on tensile loaded specimens. Experimental results demonstrated that relative humidity (RH) conditions influence strongly the damage level and damage mechanisms. Indeed, for specimen with RH = 0%, damage initiation occurs at significantly higher load level than those in RH = 50% and RH = 100% specimens. The higher relative humidity condition also results in higher damage level. Damage chronologies have been proposed as damage initiation in the form of fiber-matrix debonding occurs at fiber ends and more generally at locations where fibers are close to each other due to the generation of local stress concentration (for all studied RH contents), and first fiber breakages occur (RH = 0%). These debonded zones further propagate through fiber-matrix interface (for all studied RH contents), and new fiber breakages develop (RH = 0%). At high relative flexural stress, matrix microcracks appear and grow regardless the RH contents. For RH = 100%, these microcracks are also accompanied by many matrix deformation bands. Subsequently, they lead to the damage accumulation and then to the final failure.

Overview of Identification Methods of Mechanical Parameters Based on Full-field Measurements

Abstract: This article reviews recently developed methods for constitutive parameter identification based on kinematic full-field measurements, namely the finite element model updating method (FEMU), the constitutive equation gap method (CEGM), the virtual fields method (VFM), the equilibrium gap method (EGM) and the reciprocity gap method (RGM) Their formulation and underlying principles are presented and discussed These identification techniques are then applied to full-field experimental data obtained on four different experiments, namely (i) a tensile test, (ii) the Brazilian test, (iii) a shear-flexural test, and (iv) a biaxial test Test (iv) features a non-uniform damage field, and hence non-uniform equivalent elastic properties, while tests (i), (ii) and (iii) deal with the identification of uniform anisotropic elastic properties Tests (ii), (iii) and (iv) involve non-uniform strain fields in the region of interest

Critical factors on manufacturing processes of natural fibre composites

Abstract: Elevated environmental awareness of the general public in reducing carbon footprints and the use nonnaturally decomposed solid wastes has resulted in an increasing use of natural materials, biodegradable and recyclable polymers and their composites for a wide range of engineering applications. The properties of natural fibre reinforced polymer composites are generally governed by the pre-treated process of fibre and the manufacturing process of the composites. These properties can be tailored for various types of applications by properly selecting suitable fibres, matrices, additives and production methods. Besides, due to the complexity of fibre structures, different mechanical performances of the composites are obtained even with the use of the same fibre types with different matrices. Some critical issues like poor wettability, poor bonding and degradation at the fibre/matrix interface (a hydrophilic and hydrophobic effect) and damage of the fibre during the manufacturing process are the main causes of the reduction of the composites’ strength. In this paper, different manufacturing processes and their suitability for natural fibre composites, based on the materials, mechanical and thermal properties of the fibres and matrices are discussed in detail.