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Bilinear approximations to the mode II delamination cohesive law using an inverse method

Dourado, N.; Moura, M. F. S. F. de; Morais, A. B. de; Pereira, A. B.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.39%
Cohesive zone modelling has proved to be a powerful tool to model delamination problems in high performance composites. Application to mode II delamination is of particular interest due to the large fracture process zone. In this paper, bilinear approximations to the mode II delamination cohesive law were determined for two carbon/epoxy composites. This was achieved by an inverse method that consisted of making Finite Element Analyses fit experimental load-displacement curves measured in well-known End-Notched Flexure tests. The optimal parameters of the bilinear cohesive law were determined by a genetic algorithm. The results showed the adequacy of the bilinear cohesive law and of the methodology employed.

Mode I cohesive zone model for delamination in composite beams

Morais, A. B. de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.12%
A cohesive zone model was developed for mode I delamination in composite beams. The present model is an extension of a beam on elastic foundation analysis similar to the one that led to the well-known corrected beam theory data reduction scheme. In particular, it is demonstrated that the shear foundation considered in most formulations can actually be discarded, thereby allowing a much simpler model implementation. The present model agrees very well with finite element analyses of double cantilever beam and moment-loaded double cantilever beam specimens with a wide range of properties.

Cohesive zone beam modelling of mixed-mode I-II delamination

Morais, A. B. de
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.28%
Two cohesive zone beam models were developed for mixed-mode I-II delamination. The models were assessed by application to the moment-loaded double cantilever beam specimen, for which exact solutions are available. The main difficulties were caused by the very different distributions of the normal and shear tractions in the vicinity of the crack tip. This generated considerable local mode-mix variations along the cohesive zone. The separation controlled damage formulation was more sensitive to those difficulties, which could even compromise the accuracy of results. Instead, the energy controlled damage formulation proved to be robust and thus best suited for cohesive zone beam modelling of delamination.

Microstructure and microtexture assessment of delamination phenomena in charpy impact tested specimens

Haskel,Hudison Loch; Pauletti,Ederson; Martins,Juliana de Paula; Carvalho,André Luis Moreira de
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2014 EN
Relevância na Pesquisa
37.58%
In this article the delamination phenomena, which occurs in the X70 steel during fracture process from the Charpy impact tests, was investigated. Microstructure, microtexture and Taylor factor map analyses were performed by scanning electron microscopy, light microscopy and electron backscatter diffraction, respectively. In a cross-section of two fractured surface regions namely, in the perpendicular and parallel regions to the propagation fracture direction where delamination occurred, it was possible to notice that delamination showed a key role in the anisotropy of impact toughness between the L-T and T-L orientations. The results also revealed that the cause of the delamination can be attributed to the presence of microstructural banding and elongated ferrite grains aligned in a rolling direction. The presence of (100)[011] and (111)[110] crystallographic orientations, with Taylor factors close to 2.7 and 4.5, respectively, were identified in the delamination region. They contribute to the occurrence of cleavage delamination during the fracture process.

Delamination Cysts: A Predictor of Acetabular Cartilage Delamination in Hips with a Labral Tear

Gdalevitch, Marie; Smith, Karen; Tanzer, Michael
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.71%
The treatment and prognosis of labral tears of the hip depend primarily on whether there is concomitant injury of the adjacent acetabular articular cartilage. We asked whether a delamination cyst on the preoperative plain radiographs correlated with delamination of the acetabular articular cartilage at the time of hip arthroscopy. We reviewed the preoperative radiographs of 125 consecutive hips that had a labral tear at hip arthroscopy for the presence of a delamination cyst. A delamination cyst was defined as an acetabular subchondral cyst either directly adjacent to a lateral acetabular cyst or in relation to a subchondral crack in the anterosuperior portion of the acetabulum. All patients with acetabular cartilage delamination at arthroscopy were identified. There were 16 patients with delamination cysts on radiographs and 15 patients with cartilage delamination at arthroscopy. A delamination cyst on the preoperative anteroposterior and/or frog lateral radiographs of the hip accurately predicted acetabular cartilage delamination, especially in hips with labral tears not caused by a major trauma. A delamination cyst is a previously unrecognized and novel radiographic sign that can preoperatively identify acetabular cartilage delamination in patients with labral tears...

A Stretch/Bend Method for In Situ Measurement of the Delamination Toughness of Coatings and Films Attached to Substrates

He, M. Y.; Hutchinson, John W.; Evans, Anthony G.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.12%
A stretch/bend method for the in situ measurement of the delamination toughness of coatings attached to substrates is described. A beam theory analysis is presented that illustrates the main features of the test. The analysis is general and allows for the presence of residual stress. It reveals that the test produces stable extension of delaminations, rendering it suitable for multiple measurements in a single test. It also provides scaling relations and enables estimates of the loads needed to extend delaminations. Finite element calculations reveal that the beam theory solutions are accurate for slender beams, but overestimate the energy release rate for stubbier configurations and short delaminations. The substantial influence of residual stress on the energy release rate and phase angle is highly dependent on parameters such as the thickness and modulus ratio for the two layers. Its effect must be included to obtain viable measurements of toughness. In a companion paper, the method has been applied to a columnar thermal barrier coating deposited onto a Ni-based super-alloy.; Engineering and Applied Sciences

The Influence of Transient Thermal Gradients and Substrate Constraint on Delamination of Thermal Barrier Coatings

Hutchinson, John W.; Sundaram, S.; Johnson, C. A.; Lipkin, D. M.
Fonte: American Society of Mechanical Engineers Publicador: American Society of Mechanical Engineers
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.47%
A systematic study of factors affecting the delamination energy release rate and mode mix of a thermal barrier coating attached to a substrate is presented accounting for the influence of thermal gradients combined with rapid hot surface cooling. Transient thermal gradients induce stress gradients through the coating and substrate, which produce overall bending if the substrate is not very thick and if it is not constrained. Due to their influences on the coating stresses, substrate thickness and constraint are important aspects of the mechanics of delamination of coating-substrate systems, which must be considered when laboratory tests are designed and for lifetime assessment under in-service conditions. Temperature gradients in the hot state combined with rapid cooling give rise to a maximum energy release rate for delamination that occurs in the early stage of cooling and that can be considerably larger than the driving force for delamination in the cold state. The rates of cooling that give rise to a large early stage energy release rate are identified.; Engineering and Applied Sciences

Lifetime Assessment for Thermal Barrier Coatings: Tests for Measuring Mixed Mode Delamination Toughness

Hutchinson, Robert G.; Hutchinson, John W.
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.47%
Mechanisms leading to degradation of the adherence of thermal barrier coatings (TBC) used in aircraft and power generating turbines are numerous and complex. To date, robust methods for the lifetime assessment of coatings have not emerged based on predictions of the degradation processes due to their complexity. In the absence of mechanism-based predictive models, direct measurement of coating adherence as a function of thermal exposure must be a component of any practical approach toward lifetime assessment. This paper outlines an approach to lifetime assessment of TBC that has taken shape in the past few years. Most TBC delaminations occur under a mix of mode I and mode II cracking conditions, with mode II delamination being particularly relevant. Direct measurement of TBC delamination toughness has been challenging, but recent progress has made this feasible. This paper surveys a range of potentially promising tests for measuring the mode dependence of delamination toughness with particular emphasis on toughness under mode II conditions.; Engineering and Applied Sciences

Detection of delamination damage in a composite laminate beam utilising the principle of strain compatibility

Wildy, S.; Cazzolato, B.; Kotooussov, A.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
37.12%
This paper presents an experimental investigation of a new method for damage detection based on the most fundamental concept in continuum mechanics: strain compatibility. Compliance with this principle implies a deformed material is free from discontinuities, which are indicative of many types of structural damage. Therefore the principle of strain compatibility, in its ability to identify discontinuities, is very promising as a new foundation for future research into non-destructive evaluation and structural health monitoring technologies. The proposed method has many advantages compared to existing damage detection techniques, such as its invariance to material properties, type and intensity of loading, and the geometry of the structure. In this paper, a proposed formulation of the strain compatibility equation for beam structures, which is invariant to loading intensity, is presented. An experimental investigation of the proposed algorithm was conducted on a delaminated cantilever beam, utilising a PSV-3D scanning laser vibrometer. The experiment demonstrated that the strain compatibility technique can accurately locate delamination damage in composite beam structures.; Stuart Wildy, Benjamin Cazzolato and Andrei Kotousov

Modelling of delamination damage in composite beams

Herath, Manudha Thiyunuwan; Bandyopadhyay, Kaustav; Logan, Joshua Desmond
Fonte: Engineers Australia Publicador: Engineers Australia
Tipo: Conference paper
Publicado em //2010 EN
Relevância na Pesquisa
37.47%
Composite structures have gained importance in engineering applications due to their favourable mechanical properties, for example laminate materials are widely used in many applications. However, for laminate materials, the presence of the layers makes the structures prone to delamination damage, which can be hard to detect with conventional detection techniques. An important aspect of any damage detection technique is an understanding of the mechanical behaviour of the ‘damaged’ material or component. This can be best achieved through theoretical modelling. This paper focuses on modelling delamination in composite beams using finite element analysis model and an analytical Euler-beam model. Several beam models with different delamination sizes were developed and analysed using FEA software ANSYS. The curvature plots obtained were analysed using the mathematical formulations of the governing equations. Finally, a simple 1-D beam model with delamination was developed to understand the mechanical behaviour of the delaminated component. The developed theory is later intended to be integrated with a new damage detection technique using a scanning laser doppler vibrometer.; Manudha T. Herath, Kaustav Bandyopadhyay and Joshua D. Logan

Delamination prediction in orthogonal machining of carbon long fiber-reinforced polymer composites

Santiuste, Carlos; Olmedo, Álvaro; Xoldani, Xavier; Miguélez, Henar
Fonte: SAGE Publicador: SAGE
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em 17/07/2012 ENG
Relevância na Pesquisa
37.12%
Machining processes of composites are common operations in industry involving elevated risk of damage generation in the workpiece. Long fiber reinforced polymer composites used in high-responsibility applications require safety machining operations guaranteeing workpiece integrity. Modeling techniques would help in the improvement of machining processes definition; however, they are still poorly developed for composites. The aim of this paper is advancing in the prediction of damage mechanisms involved during cutting, including out-of-plane failure causing delamination. Only few works have focused on three-dimensional simulation of cutting; however, this approach is required for accurate reproduction of the complex geometries of tool and workpiece during cutting processes. On the other hand, cohesive interactions have proved its ability to simulate out-of-plane failure of composites under dynamic loads, as impact events. However, this interlaminar interaction has not been used up to date to model out-of-plane failure induced during chip removal. In this paper, both a classical damage model and cohesive interactions are implemented in a three-dimensional model based on finite elements, in order to analyze intralaminar and interlaminar damage generation in the simplified case of orthogonal cutting of carbon LFRP composite. More realistic damage predictions using cohesive interactions were observed. The strong influence of the stacking sequence on interlaminar damage has been demonstrated.; Financial support for this work has been provided by the Ministry of Science and Innovation of Spain under the projects DPI2011-25999 and TRA2010-19573.

Delamination prediction in orthogonal machining of carbon long fiber-reinforced polymer composites

Santuiste, Carlos; Olmedo, Álvaro; Soldani, Xavier; Miguélez, Henar
Fonte: SAGE Publications Publicador: SAGE Publications
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em /07/2012 ENG
Relevância na Pesquisa
37.12%
Machining processes of composites are common operations in industry involving elevated risk of damage generation in the workpiece. Long fiber reinforced polymer composites used in high-responsibility applications require safety machining operations guaranteeing workpiece integrity. Modeling techniques would help in the improvement of machining processes definition; however, they are still poorly developed for composites. The aim of this paper is advancing in the prediction of damage mechanisms involved during cutting, including out-of-plane failure causing delamination. Only few works have focused on three-dimensional simulation of cutting; however, this approach is required for accurate reproduction of the complex geometries of tool and workpiece during cutting processes. On the other hand, cohesive interactions have proved its ability to simulate out-of-plane failure of composites under dynamic loads, as impact events. However, this interlaminar interaction has not been used up to date to model out-of-plane failure induced during chip removal. In this paper, both a classical damage model and cohesive interactions are implemented in a three-dimensional model based on finite elements, in order to analyze intralaminar and interlaminar damage generation in the simplified case of orthogonal cutting of carbon LFRP composite. More realistic damage predictions using cohesive interactions were observed. The strong influence of the stacking sequence on interlaminar damage has been demonstrated.; Financial support for this work has been provided by the Ministry of Science and Innovation of Spain under the projects DPI2011 25999 and TRA2010 19573.

Numerical prediction of delamination in CFRP drilling

Feito Sánchez, Norberto; López-Puente, Jorge; Santiuste, Carlos; Miguélez, Henar
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article
Publicado em /02/2014 ENG
Relevância na Pesquisa
37.47%
Delamination is one of the undesired effects of machining using non appropriate cutting parameters or worn drill. Finite element modeling of drilling of Carbon Fiber Reinforced Polymer (CFRP) composites is an interesting tool for damage prediction. Recently, complete modeling of the process including the rotatory movement of the drill, penetration in the composite plate and element erosion has been developed in the scientific literature. Computational cost of these complex models is a great disadvantage when comparing them with simplified models that consider the drill acting like a punch that pierces the laminate. In this paper both complete and simplified models were developed and compared in terms of delamination prediction. The simplified model, presenting reduced computational cost, slightly overestimates the delamination factor when compared with the complex model. The influence on delamination of thrust force, clamping area at the bottom surface of the laminate and the stacking sequence is studied using the simplified model.; This work was supported by the Ministry of Economy and Competitiveness of Spain under the Project DPI2011-25999.

The proper generalized decomposition for the simulation of delamination using cohesive zone model

METOUI, Sondes; PRULIERE, Etienne; AMMAR, Amine; DAU, Frédéric; IORDANOFF, Ivan
Fonte: Wiley Publicador: Wiley
EN
Relevância na Pesquisa
37.12%
The use of cohesive zone models is an efficient way to treat the damage, especially when the crack path is known a priori. This is the case in the modeling of delamination in composite laminates. However, the simulations using cohesive zone models are expensive in a computational point of view. When using implicit time integration scheme or when solving static problems, the non-linearity related to the cohesive model requires many iterations before reaching convergence. In explicit approaches, the time step stability condition also requires an important number of iterations. In this article, a new approach based on a separated representation of the solution is proposed. The Proper Generalized Decomposition is used to build the solution. This technique, coupled with a cohesive zone model, allows a significant reduction of the computational cost. The results approximated with the PGD are very close to the ones obtained using the classical finite element approach.

Asymmetric delamination and convective removal numerical modeling: Comparison with evolutionary models for the Alboran sea region

Valera, J. L.; Negredo, A. M.; Villaseñor, Antonio
Fonte: Birkhäuser Verlag Publicador: Birkhäuser Verlag
Tipo: Artículo Formato: 824230 bytes; application/pdf
ENG
Relevância na Pesquisa
37.28%
Convective removal and mantle delamination are geodynamical mechanisms proposed to explain the presence of extension in the Alboran Sea within a regional context of compression. Using a new thermo-mechanical algorithm, we present here a quantitative evaluation and comparison of conceptual models based on these geodynamical mechanisms. In contrast to the in situ convective removal process, the laterally propagating delamination mechanism is shown here to be consistent with first-order features of the Alboran Sea such as the thinning/thickening distribution, intermediate-depth seismicity and upper mantle structure imaged by seismic tomography. The lower crust is predicted to reach depths of 100–150 km in some areas, due to mechanically-driven viscous drag of the downwelling mantle.; This work was funded by the Spanish Plan Nacional del MEC projects CTM2006- 13666-C02-02/MAR and CTM2005-08071-C03-03/MAR; and funding for UCM Research Groups. This is a contribution of the Consolider-Ingenio 2010 team CSD2006- 00041 (TOPO-IBERIA). J. L. Valera acknowledges the support of a UCM grant. Figure 2 has been made with the graphic program P developed by Wim Spakman. Calculations were partially carried out in the Fiswulf cluster of the Faculty of Physics.; Peer reviewed

Analyzing objects in images for estimating the delamination influence on load carrying capacity of composite laminates

Durão, Luís Miguel; Magalhães, António G.; Tavares, João Manuel R. S.; Torres Marques, A.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2008 ENG
Relevância na Pesquisa
37.28%
The use of fiber reinforced plastics has increased in the last decades due to their unique properties. Advantages of their use are related with low weight, high strength and stiffness. Drilling of composite plates can be carried out in conventional machinery with some adaptations. However, the presence of typical defects like delamination can affect mechanical properties of produced parts. In this paper delamination influence in bearing stress of drilled hybrid carbon+glass/epoxy quasi-isotropic plates is studied by using image processing and analysis techniques. Results from bearing test show that damage minimization is an important mean to improve mechanical properties of the joint area of the plate. The appropriateness of the image processing and analysis techniques used in the measurement of the damaged area is demonstrated.

Analysis of delamination growth with discontinuous solid-like shell elements

Remmers, Joris J C; Wells, G N; De Borst, R
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Conferência ou Objeto de Conferência
EN
Relevância na Pesquisa
37.28%
In Mang, H. A., Rammerstorfer, F. G., and Eberhardsteiner, J., editors, Proceedings of the Fifth World Congress on Computational Mechanics (WCCM V), Austria. Vienna University of Technology.; In this contribution a new finite element is presented for the simulation of delamination growth in thin layered composite materials. The element is based on the solid-like shell element, a volume element that can be used in very thin applications due to a higher order displacement field in thickness direction. The delamination crack is incorporated in this element as a jump of the displacement field by means of the partition of unity method. The kinematics of the element as well as the finite element formulation are described. The performance of the element is demonstrated by means of two examples.

Analysis of delamination growth with discontinuous finite elements

Remmers, Joris J C; Wells, G N; De Borst, R
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Conferência ou Objeto de Conferência
EN
Relevância na Pesquisa
37.39%
In 2nd European Conference on Computational Mechanics (CDROM), Cracow, Poland.; Delamination is one of the most important failure mechanisms in laminates. Normally, it is modelled using interface elements. These elements are placed between two layers that are modelled with continuum elements. The interface elements are equipped with a softening or damage model in order to simulate debonding. This method has some drawbacks, both in a numerical and in a mechanical sense. A recent alternative is to simulate the crack by adding a discontinuous displacement mode to the continuum elements according to the partition of unity method. The elements do not contain the discontinuity prior to cracking, but when the ultimate stress in the bulk material is exceeded, delamination is initiated and additional degrees-of-freedom are activated. Beside this, a slightly different implementation is examined also. A discontinuity is predefined and has an initial dummy stiffness. Delamination is initiated when the tractions in the discontinuity exceed a threshold value. The results of both versions of this partition of unity model are compared mutually and with conventional interface elements by means of two examples.

Mode I and mode II delamination properties of glass/vinyl-ester composite toughened by particulate modified interlayers

Stevanovic, Dejan; Kalyanasundaram, Shankar; Lowe, Adrian; Jar, P-Yue
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.39%
Various vinyl-ester (VE)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were used for interlayer-toughening of a glass/VE composite to increase delamination resistance of the base material under mode I and mode II loading. Dry ABS powder was mixed with the liquid resin in four weight ratios: 3.5, 7, 11 and 15 phr (parts per hundred parts of resin) while the layer thickness was varied within the range of 150-500 μm. Firstly, mode I fracture toughness and tensile properties of the VE/ABS blends were assessed. By using the Raman Spectroscopy technique a chemical reaction was discovered which occurred during ABS-VE mixing: i.e. butadiene transition from the ABS particles to the VE. A butadiene saturation was discovered to occur in the VE beyond 7% ABS particle content. Both mode I and mode II fracture toughness were significantly improved with application of the interlayers. Mode I fracture toughness was found to be a function of layer thickness and particle content variations. The latter dominated G Ic after the saturation point. On the other hand mode II fracture toughness was found to be independent of the layer thickness (within the used layer thickness range) and only moderately influenced by the particle content. Important Toughening mechanisms were plastic deformation and micro-cracking of the layer materials. Evidence of both mechanisms has been found using optical and scanning electron microscopy (SEM).

Simulation of delamination growth under high cycle fatigue using cohesive zone models

Camanho,Pedro P.; Turon,Albert; Costa,Josep
Fonte: Sociedade Portuguesa de Materiais Publicador: Sociedade Portuguesa de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
37.12%
A cohesive zone model is proposed for the simulation of delamination growth in composite materials under high-cycle fatigue loading. The basis for the formulation is an interfacial constitutive law that links fracture mechanics and damage mechanics relating the evolution of the damage variable, d, with the crack growth rate, da/dN. The cohesive zone model is implemented in ABAQUS finite element code and used in the simulation of carbon-epoxy test specimens cyclically loaded in mode I, mode II and mixed-mode I and II. The accuracy of the model is assessed by comparing the predictions with experimental data.