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L. Douminge,X. Feaugas,J. Bernard,S. Mallarino 한국물리학회 2013 Current Applied Physics Vol.13 No.8
A fluorescence probe, inserted in a solid polymeric matrix, is used to follow the first steps of photodegradation by fluorescence spectroscopy. The competition between cross-linking and chain breaking during the degradation entail physical modifications in the macromolecular chains. These modifications usually followed by gel permeation spectroscopy can be studied by extrinsic florescence spectroscopy. Due to the high sensitivity of the fluorescent probe to the polymer matrix evolution, all the structural modifications can be investigated. In particular during the first photo-degradation steps, a correlation with activation energy necessary to the chain mobility is used to understand the sensibility of the fluorescent probe.
Impact of composite patch on the J-integral in adhesive layer for repaired aluminum plate
Kaci, D. Ait,Madani, K.,Mokhtari, M.,Feaugas, X.,Touzain, S. Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.6
The aim of this study is to perform a finite element analysis of the Von Mises stresses distribution in the adhesive layer and of the J-Integral for a damaged plate repaired by a composite patch. Firstly, we study the effect of the fiber orientation, especially the position of the layers that have orientation angle different of $0^{\circ}$ from the first layer which is in all cases of our study oriented at ($0^{\circ}$) on the J-Integral. Secondly, we evaluate the effects of the mechanical properties of the patch and the use of a hybrid patch on the reduction of stresses distribution and J-Integral. The results show clearly that the stacking sequence for the composite patch must be selected to absorb optimally the stresses from the damaged area and to position the various layers of the composite under the first layer whose fibers orientation will remain in all cases equal to $0^{\circ}$. The use of a hybrid composite reduces significantly the J-Integral and the stresses in both damaged plate and the adhesive layer.
Aicha Benchiha,Kouider Madani,Sebastien Touzain,Xavier Feaugas,Mohan Ratwani 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.4
The determination of the stress intensity factor at the crack tip is one of the most widely used methods to predict the fatigue life of aircraft structures. This prediction is more complicated for repaired cracks with bonded composite patch. This study is used to compute the stress intensity factor (SIF) and crack opening displacement (COD) for cracks repaired with single and double-sided composite patches. The effect of the presence of disbond region in adhesive at the crack was taken into consideration. The results show that there is a considerable reduction in the asymptotic value of the stress-intensity factors and the crack opening displacement at the crack tip. The use of a double-sided patch suppresses the bending effect due to the eccentricity of the patch on one side only.
L. Douminge,S. Mallarino,S. Cohendoz,X. Feaugas,J. Bernard 한국물리학회 2010 Current Applied Physics Vol.10 No.4
Artificial ageing of high density polyethylene (HDPE) exposed to ultra-violet irradiation has been investigated by fluorescence spectroscopy. In the case of HDPE, fluorescence spectroscopy requires the addition of fluorophore, (rhodamine 101 laser dye). The spectral features of fluorescence are very sensitive to the interaction between the exited molecules and the polymer matrix. Under wavelength close to 254 nm, the diffusion of oxygen can introduce groups such as C-O, C=O and C(=O)O into the molecular chains. Thus entail structural and chemical modifications such as polymeric chain breaking, cross linking and oxidation. In the present work, we clearly illustrate the fact that fluorescence spectroscopy is very worthwhile in particular to follow the early stages of photo-degradation.
A new analytical approach for optimization design of adhesively bonded single-lap joint
M. Elhannani,K. Madani,M. Mokhtari,S. Touzain,X. Feaugas,S. Cohendoz 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.2
In this study the three-dimensional nonlinear finite element method was used to analyze the stresses distribution in the adhesive layer used to joint two Aluminum 2024-T3 adherends. We consider in this study the effect of different parameters witch directly affect the values of different stresses. The experimental design method is used to investigate the effects of geometrical parameters of the single lap joint in order to achieve an optimization of the assembly with simple lap joint. As a result, it can be said that both the geometrical modifications of the adhesive and adherends edge have presented a significant effect at the overlap edge thereby causing a decrease in peel and shear stresses. In addition, an analytical model is also given to predict in a simple but effective way the joint strength and its dependence on the geometrical parameters. This approach can help the designers to improve the quality and the durability of the structural adhesive joints.