Carbone/epoxy interface debond growth using the Contour Integral/Cohesive zone method

Cohesive zone models (CZM) are widely used for modeling the damages interfacial. In this study, a three-dimensional finite element (FE) model is developed to study numerically the energy release rate (ERR) by the J integral method. The simulation of a tensile test (in the direction of fiber) on a fibrous composite is performed using the damage model. The results obtained from the Integral Contour/Cohesive zone model are compared with those obtained previously and the results show a good agreement with the reference one obtained (J-integral and VCCT method). These analyses are studied according to several parameters such as: the debonding angles, the fiber volume fraction which is studied by varying distance between the broken fiber and the neighboring fibers, comparing two different representative volume elementary (RVE) (square and hexagonal motives). This study goes into the context and allows the analysis of the fiber/matrix interfacial crack behavior in a fiber micro-composite. The obtained results have demonstrated that the ERR and the intensity of the mechanical stresses depend not only on the level of the mechanical loading applied, but also on the angle of the debonding at the fiber/matrix interface

Experimental and Numerical Study of Fracture Behavior under Mixed-Mode of Al-Alloy AA3003 Not Welded and Welded by FSW Process

International audienceThis study presents an experimental and computational analysis of fracture under mixed-mode conditions in aluminum alloy AA3003 using the Compact Tension Shear CTS specimen, both not welded and Friction stir welded. Mixed-mode fracture experiments were performed using the CTS specimen and an ARCAN loading device based on Richard's principle suitable for mixed-mode. The approach of linear elastic fracture mechanics allows for a better understanding of mixed-mode failure and the evaluation of the stress intensity parameters KI and KII. The variation of the stress intensity factor KI, KII is influenced by the pre-cracks length. The comparison between experimental results and the numerical results of simulation shows that there is a good agreement between these results

J-integral evaluation of repaired cracks in AA7075-T6 structures subjected to uniaxial tensile stresses

Bonded repairs using composite patches over metallic structures have been evaluated as a cost effective method to increase the life of damaged structures. The J-integral is a widely applied fracture mechanics parameter relating to the energy release associated with crack growth and is a measure of the deformation intensity at the crack tip. In practice, the calculated J-integral can be compared with a critical value for the material under consideration to predict fracture. This study aimed at providing an overview of the behavior of a cracked plate of AA7075-T6 alloy repaired with a boron-epoxy patch bonded with FM73 Adhesive layer. The Finite Element Method (FEM) using Abaqus Software 6.14 predicted the performance. The results show a considerable decrease in the value of the J-integral. This is due to the beneficial effect of the patch on the stress state at the crack tip. The best results were obtained from a uni-directional composite fibres orientation of 0°, where the fibers oriented parallel to the direction of load. A parametric analysis has been carried out to evaluate the effect of lay-up, load variation and crack mouth opening on the J-integral. It was found that the crack mouth opening displacement (CMOD) was reduced by 90–97%.https://www.elsevier.com/locate/polytest2020-08-01hj2019Materials Science and Metallurgical Engineerin

XFEM and CZM modeling to predict the repair damage by composite patch of aircraft structures: Debonding parameters

International audienceIn this work, a model based on the combination of two approaches XFEM and CZM, has been used to predict the damage of repairs by composite patch (patch/adhesive/plate assembly). This degradation is analyzed in terms of adhesive damage considering both initiation and propagation of interfacial debonding. The interfacial cohesive zone of the patch/adhesive/plate system is defined by its cohesive properties and its resistance to debonding estimated from the displacement‐load curves. This study highlights, as a function of the adhesive properties of the plate/patch interface, the competition between two degradation mechanisms: adhesive damage (through a mechanism of initiation and propagation of patch debonding from the plate) and plate damage (through a phenomenon of crack initiation and propagation emanating from notch). It also highlights, depending on the nature of the interface, four physical parameters: the bending deflection of the repaired plate, the displacement path of the patch‐reinforced plate, the debonding resistance and the interfacial shear stresses, characteristic of the adhesive joint damage and their interactions with the interface. This is the originality of this study. Results show that XFEM simulations based on the CZM model allow adequate prediction of the damage of the patch/adhesive/plate assemblies