0000000000636585
AUTHOR
Xiaojing Gong
Design and optimization of bonded patch repairs of laminated composite structures
International audience; The present study proposes a method for design optimization of external patched repairs. The tensile behavior of notched specimens with patched repair was studied using finite element analysis and compared with experimental results. It was found that high stress concentrations along the transverse edges of circular patches and/or at the longitudinal edges of the hole leads to early damage initiation in the parent plate. The damage initiation site and its propagation depend on the patch in-plane stiffness. The optimal patch design can be characterized by a strength ratio R*. The overall design of the patch repair can be considered using a dimensionless design paramete…
Tensile behaviour of patch-repaired CFRP laminates
The present study examines the tensile behaviour of composite structures repaired by bonding external patches. Various patches of different stacking sequences placed on both sides of the parent plate were considered. Damage development and the failure process of the repaired plates were analyzed and a parent plate fracture model has been proposed. Optimised patch repairs were calculated by finite element modelling. It was found that high stress concentration along the longitudinal edges of circular patches and/or at the transverse edges of the hole leads to early damage initiation in the parent plate. However, the position of damage initiation and the process of damage progression depend pa…
Test de délaminage de composites en mode III pur du type ERCT
International audience; Les matériaux composites sont de plus en plus utilisés dans le domaine des transports. Ils permettent de réaliser des structures légères économes en carburant. La connaissance approfondie de leur comportement mécanique est essentielle pour assurer un dimensionnement des structures optimisé. Les travaux présentés ici concernent le délaminage des composites, c’est un mode d’endommagement très fréquent de ces matériaux. En mécanique de la rupture, on distingue trois mode de sollicitation, le mode I d'ouverture de la fissure, le mode II de glissement perpendiculaire au fond de fissure et le mode III de glissement parallèle au fond de fissure. De nombreux travaux de reche…
Effet de l'orientation des fibres des plis adjacents sur la résistance au délaminage en mode I pur = Effect of the fibre's orientation of adjacent ply on pure mode I fracture toughness
National audience; Ce travail concerne l'étude de l'effet de l'orientation des fibres des plis adjacents à la fissure dans une éprouvette DCB (Double Cantilever Beam) sur la résistance au délaminage en mode I pur. Afin d'isoler l'influence de l'orientation l'étude porte sur des stratifiés particuliers ayant tous les mêmes matrices de comportement global A B D. Les résultats expérimentaux montrent une grande variation de résistance au délaminage GIC et des courbes R selon l'orientation des plis situés de part et d'autre du plan de fissure. Une modélisation par éléments finis permet de mettre en évidence l'importance de l'état de contraintes locales et donc de l'endommagement au voisinage du …
Application of cohesive-zone models to delamination behaviour of composite material
International audience; The parameters of cohesive elements have to be chosen correctly in the simulation of composite delamination by finite element method: such as interface strength, interface stiffness and shape of cohesive law. The purpose of this work is to investigate their influence on the accuracy of the results obtained. A three-dimensional cohesive-zone model has been established using Ls-dyna to simulate Double-Cantilever-Beam mode I (DCB) and Edge-Notched-Flexure mode II (ENF) tests. The influence of these parameters of cohesive element on the maximum load and the slope of load-displacement curve have been discussed by comparing experimental and numerical results. Four traction…
Tensile behaviour of anti-symmetric CFRP composite
Abstract This paper addresses the response of a 17-ply anti-symmetric carbon/epoxy composite subjected to uniaxial tensile loading. Hashin ply damage model is adopted to describe the damage behaviour of the plies, whereas damage initiation and progression of the interfaces are characterised by mixed-mode cohesive damage model. Force-displacement curves obtained numerically and experimentally show good agreement. Results show that all laminae and interfaces experience the damage except laminae with 0o fibre. In addition, damage is concentrated at the tab and central regions of the tensile specimen. Edge delamination is observed in all interfaces.
Fiber bridging in DCB specimens and its effects on R-curves of a glass/epoxy composite
International audience
Evolution de la participation du mode II dans le cas d'un délaminage en mode mixte I+II d'un composite stratifié verre/époxy
International audience
R-Curve Modelling of Mode I Delamination in Multidirectional Carbon/Epoxy Composite Laminates
In the present work, the mode I delamination behaviour of a quasi-isotropic quasi-homogeneous carbon/epoxy composite laminate with adjacent plies of 0o//45o is studied numerically. To describe the R-curve behaviour observed during crack propagation, a linear-exponential traction-separation law is proposed, where the fracture toughness and the increment in the fracture energy could be considered separately in the model. This model is then implemented in the finite element simulation of the delamination process in the composite laminate. Numerical results indicate that with the incorporation of the fibre bridging effect leads to a well-predicted force-displacement response of the composite la…
Strength prediction of a triaxially braided composite
The architecture of textile reinforcement affects the deformation and failure behavior of the textile reinforced composites. This paper presents an approximate method that incorporates the in-plane periodic meso structure of the textile composite in finite element models. In this approach, the representative unit cell (RUC) of a textile composite is divided into sub-cells. Instead of obtaining a homogeneous equivalent, these sub-cells are idealized and represented with laminates of different layups using shell elements. In this way, an RUC can be constructed with a small number of elements. This method holds the promise of creating a textile composite FE model with an improved accuracy with…
Moisture Effects on Patch Bonded Composite Repairs
The present work investigated the effects of moisture absorption on the residual tensile strength of unnotched, notched and double-patch repaired carbon/epoxy composites. Patches were bonded to the parent plate using Araldite2015 adhesive. Specimens were aged in demineralised water at 70°C and tested at moisture content of 0% (dry), 3%, 6% and 7%. Results showed that upon ageing, a maximum of 11% and 17% of strength reduction was found in unnotched and repaired specimens, respectively. On the contrary, a maximum of 15% increment in strength was observed in notched specimens. In addition, good fits to the experimental data were found using the proposed residual strength model, with the maxim…
Effects of fiber orientation of adjacent plies on the mode I crack propagation in a carbon-epoxy laminates
Abstract The influence of ply orientation on the resistance to mode I delamination of multidirectional composite laminates can be assessed by Double Cantilever Beam (DCB) tests. However, one of the difficulties associated with such a study is the change in overall elastic parameters occurring when modifying local ply orientations. The present work uses laminates with special stacking sequences allowing for isolating the orientation parameter. Multidirectional DCB specimens were designed so as to obtain an uncoupled quasi isotropic and quasi-homogeneous elastic behavior, with the same properties for the entire laminate and the two sub laminates separated by the pre crack at mid-plane. The re…
Modélisation numérique de structures composites réparées par collage de patchs externes en traction
National audience; Request PDF on ResearchGate \textbar On Dec 30, 2014, Lingling Peng and others published Modélisation numérique de structures composites réparées par collage de patchs externes en traction