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T E Tay - One of the best experts on this subject based on the ideXlab platform.
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traction Separation Laws for progressive failure of bonded scarf repair of composite panel
Composite Structures, 2011Co-Authors: Mohd Ridha, V B C Tan, T E TayAbstract:Abstract Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–Separation Law is used, but the influence of adhesive strength is not significant when exponential softening traction–Separation Law is used.
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Traction–Separation Laws for progressive failure of bonded scarf repair of composite panel
Composite Structures, 2011Co-Authors: Mohd Ridha, V B C Tan, T E TayAbstract:Abstract Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–Separation Law is used, but the influence of adhesive strength is not significant when exponential softening traction–Separation Law is used.
Viggo Tvergaard - One of the best experts on this subject based on the ideXlab platform.
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Effect of plastic anisotropy on crack growth resistance under mode 1 loading
International Journal of Fracture, 2004Co-Authors: Viggo Tvergaard, Brian Nyvang LegarthAbstract:Crack growth in a solid with plastic anisotropy is modeled by representing the fracture process in terms of a traction-Separation Law specified on the crack plane, and crack growth resistance curves are calculated numerically. A phenomenological elastic-viscoplastic material model is applied, using one of two different anisotropic yield criteria to account for the plastic anisotropy. The analyses are carried out for conditions of small scale yielding, with mode I loading conditions far from the crack-tip. Different initial orientations of the principal axes relative to the crack plane are considered and it is found that the steady-state fracture toughness is quite sensitive to the type of anisotropy and to the angle of inclination of the principal axes relative to the crack plane.
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studies of void growth in a thin ductile layer between ceramics
Computational Mechanics, 1997Co-Authors: Viggo TvergaardAbstract:The growth of voids in a thin ductile layer between ceramics is analysed numerically, using an axisymmetric cell model to represent an array of uniformly distributed spherical voids at the central plane of the layer. The purpose is to determine the full traction-Separation Law relevant to crack growth by a ductile mechanism along the thin layer. Plastic flow in the layer is highly constrained by the ceramics, so that a high level of triaxial tension develops, leading in some cases to cavitation instabilities. The computations are continued to a state near the occurrence of void coalescence.
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on the toughness of ductile adhesive joints
Journal of The Mechanics and Physics of Solids, 1996Co-Authors: Viggo Tvergaard, J W HutchinsonAbstract:Crack propagation along one of the interfaces between a thin ductile adhesive layer and the elastic substrates it joins is considered. The layer is taken as being elastic-plastic, and the fracture process of the interface is modeled by a traction-Separation Law, characterized by the peak Separation stress 6 and the work of Separation per unit area To. Crack growth resistance curves for mode I loading of the adhesive joint are computed, with emphasis on steady-state toughness, as a function of three extrinsic effects : layer thickness, layer-substrate modulus mismatch, and initial residual stress in the layer. Conditions under which Separation first occurs well ahead of the initial crack tip are discussed. 1. SPECIFICATION OF THE MODEL This paper continues the study begun by Tvergaard and Hutchinson (1994) in which an embedded fracture zone model is applied to the mode I fracture of an adhesive joint comprised of a thin elastic-plastic metal layer joining two elastic substrates. The present work employs the model to investigate the influence on joint toughness of both the elastic mismatch between the layer and the substrates and the residual stress in the layer. As in the earlier study, the thickness of the ductile layer is another extrinsic variable which comes into play. The approach adopted was first introduced by Needleman (1987) to study particle debonding in metal matrices and subsequently by Tvergaard and Hutchinson (1992, 1993) to model crack growth resistance in homogeneous solids and along interfaces. A traction-Separation Law simulating the fracture process is embedded within an elastic-plastic continuum as a boundary condition along the line extending ahead of the crack. In the case of an interface joining dissimilar materials, the Separation Law necessarily involves both the normal and shear tractions and the two associated relative displacements of the surfaces across the interface.
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the relation between crack growth resistance and fracture process parameters in elastic plastic solids
Journal of The Mechanics and Physics of Solids, 1992Co-Authors: Viggo Tvergaard, J W HutchinsonAbstract:CKA~K growth initiation and subsequent resistance is computed for an elastic-plastic solid with an idealized traction Separation Law specified on the crack plane to characterize the fracture process. The solid is specified by its Young’s modulus, E, Poisson’s ratio, v, initial tensile yield stress, (or, and strain hardening exponent, N. The primary parameters specifying the traction-Separation Law of the fracture process are the work of Separation per unit area, To. and the peak traction, 6. Highly refined calculations have been carried out for resistance curves. K,(Arr), for plane strain, mode I growth in small-scale yielding as dependent on the parameters characterizing the elastic-plastic properties of the solid and its fracture process. With K,, = [El-,/( I ~ v’)] ’ 2 as the intensity needed to advance the crack in the absence ofplasticity, K,J& is presented in terms of its dependence on the two most important parameters, d/nr and N, with special emphasis on initiation toughness and steady-state toughness, Three applications of the results are made : to predict toughnesss when the fracture process is void growth and coalescence, to predict the role of plasticity on interface toughness for similar materials bonded together, and to illuminate the role of plasticity in enhancing toughness in dual-phase solids. The regime of applicability of the present model to ductile fracture due to void growth and coalescence, wherein multiple voids interact within the fracture process zone, is complementary to the regime of applicability of models describing the interaction between a single void and the crack tip. The two mechanism regimes are delineated and the consequence of a transition between them is discussed.
Stefanie Reese - One of the best experts on this subject based on the ideXlab platform.
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Cohesive zone modeling for mode I facesheet to core delamination of sandwich panels accounting for fiber bridging
Composite Structures, 2018Co-Authors: Daniel Höwer, Bradley A. Lerch, Brett A. Bednarcyk, Evan J. Pineda, Stefanie Reese, Jaan-willem SimonAbstract:Abstract A new cohesive zone traction-Separation Law, which includes the effects of fiber bridging, has been developed, implemented with a finite element (FE) model, and applied to simulate the delamination between the facesheet and core of a composite honeycomb sandwich panel. The proposed traction-Separation Law includes a standard initial cohesive component, which accounts for the initial interfacial stiffness and energy release rate, along with a new component to account for the fiber bridging contribution to the delamination process. Single Cantilever Beam tests on aluminum honeycomb sandwich panels with carbon fiber reinforced polymer facesheets were used to characterize and evaluate the new formulation and its finite element implementation. These tests, designed to evaluate the mode I toughness of the facesheet to core interface, exhibited significant fiber bridging and large crack process zones, giving rise to a concave downward/concave upward pre-peak shape in the load–displacement curve. Unlike standard cohesive formulations, the proposed formulation captures this observed shape, and its results have been shown to be in excellent quantitative agreement with experimental load–displacement results, representative of a payload fairing structure, as well as local strain fields measured with digital image correlation.
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Two-scale modeling of joining of the aluminum alloys by a cohesive zone element technique
2016Co-Authors: Yinan Zuo, Stephan Wulfinghoff, Stefanie ReeseAbstract:The roll bonding of aluminum sheets is numerically investigated. In the first part of the paper, a cohesive zone element formulation in the framework of zero-thickness interface elements is developed. Based on a traction-Separation Law, this enables the modeling of bonding and debonding on both macroscale and microscale. Simulations on microscale are done to show the mechanism of bonding and the influence of different factors on the bonding strength.
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joining of the alloys aa1050 and aa5754 experimental characterization and multiscale modeling based on a cohesive zone element technique
Journal of Materials Processing Technology, 2014Co-Authors: Reza Kebriaei, Ivaylo N Vladimirov, Stefanie ReeseAbstract:Abstract The microstructure of two widely used engineering materials is experimentally and numerically investigated. Experimental measurements at the macroscopic scale are used for the validation of the micromechanical crystal plasticity computations. A major point of the paper is the development of a cohesive zone element formulation in the framework of zero-thickness interface elements. This enables the realistic modeling of bonding and debonding based on a traction-Separation Law. The ability of the cohesive zone element in describing the interface behavior is illustrated by means of several numerical examples, including the process of roll bonding.
J W Hutchinson - One of the best experts on this subject based on the ideXlab platform.
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on the toughness of ductile adhesive joints
Journal of The Mechanics and Physics of Solids, 1996Co-Authors: Viggo Tvergaard, J W HutchinsonAbstract:Crack propagation along one of the interfaces between a thin ductile adhesive layer and the elastic substrates it joins is considered. The layer is taken as being elastic-plastic, and the fracture process of the interface is modeled by a traction-Separation Law, characterized by the peak Separation stress 6 and the work of Separation per unit area To. Crack growth resistance curves for mode I loading of the adhesive joint are computed, with emphasis on steady-state toughness, as a function of three extrinsic effects : layer thickness, layer-substrate modulus mismatch, and initial residual stress in the layer. Conditions under which Separation first occurs well ahead of the initial crack tip are discussed. 1. SPECIFICATION OF THE MODEL This paper continues the study begun by Tvergaard and Hutchinson (1994) in which an embedded fracture zone model is applied to the mode I fracture of an adhesive joint comprised of a thin elastic-plastic metal layer joining two elastic substrates. The present work employs the model to investigate the influence on joint toughness of both the elastic mismatch between the layer and the substrates and the residual stress in the layer. As in the earlier study, the thickness of the ductile layer is another extrinsic variable which comes into play. The approach adopted was first introduced by Needleman (1987) to study particle debonding in metal matrices and subsequently by Tvergaard and Hutchinson (1992, 1993) to model crack growth resistance in homogeneous solids and along interfaces. A traction-Separation Law simulating the fracture process is embedded within an elastic-plastic continuum as a boundary condition along the line extending ahead of the crack. In the case of an interface joining dissimilar materials, the Separation Law necessarily involves both the normal and shear tractions and the two associated relative displacements of the surfaces across the interface.
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the relation between crack growth resistance and fracture process parameters in elastic plastic solids
Journal of The Mechanics and Physics of Solids, 1992Co-Authors: Viggo Tvergaard, J W HutchinsonAbstract:CKA~K growth initiation and subsequent resistance is computed for an elastic-plastic solid with an idealized traction Separation Law specified on the crack plane to characterize the fracture process. The solid is specified by its Young’s modulus, E, Poisson’s ratio, v, initial tensile yield stress, (or, and strain hardening exponent, N. The primary parameters specifying the traction-Separation Law of the fracture process are the work of Separation per unit area, To. and the peak traction, 6. Highly refined calculations have been carried out for resistance curves. K,(Arr), for plane strain, mode I growth in small-scale yielding as dependent on the parameters characterizing the elastic-plastic properties of the solid and its fracture process. With K,, = [El-,/( I ~ v’)] ’ 2 as the intensity needed to advance the crack in the absence ofplasticity, K,J& is presented in terms of its dependence on the two most important parameters, d/nr and N, with special emphasis on initiation toughness and steady-state toughness, Three applications of the results are made : to predict toughnesss when the fracture process is void growth and coalescence, to predict the role of plasticity on interface toughness for similar materials bonded together, and to illuminate the role of plasticity in enhancing toughness in dual-phase solids. The regime of applicability of the present model to ductile fracture due to void growth and coalescence, wherein multiple voids interact within the fracture process zone, is complementary to the regime of applicability of models describing the interaction between a single void and the crack tip. The two mechanism regimes are delineated and the consequence of a transition between them is discussed.
Mohd Ridha - One of the best experts on this subject based on the ideXlab platform.
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traction Separation Laws for progressive failure of bonded scarf repair of composite panel
Composite Structures, 2011Co-Authors: Mohd Ridha, V B C Tan, T E TayAbstract:Abstract Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–Separation Law is used, but the influence of adhesive strength is not significant when exponential softening traction–Separation Law is used.
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Traction–Separation Laws for progressive failure of bonded scarf repair of composite panel
Composite Structures, 2011Co-Authors: Mohd Ridha, V B C Tan, T E TayAbstract:Abstract Repair of composites has become of considerable importance recently as modern commercial airliners employ much more composites in their airframes then previously. Major maintenance, repair, and overhaul (MRO) centers must contend with issues of damage tolerance, efficiency, integrity and cost of repairs. Computational methods have been developed to sufficiently sophisticated levels to aid in the design, evaluation and optimization of proposed repair schemes before they are implemented, potentially saving time and cost. In this paper, parametric studies on progressive failure analysis of a bonded scarf repair of a composite panel was performed. The study finds that finite element models with an appropriate material property degradation scheme using the micromechanics of failure criterion are able to predict the failure load of undamaged and damaged specimen. Results of the parametric studies on adhesive properties suggest that the failure stress of a repaired composite panel is more sensitive to the strength of the cohesive elements than to its toughness when a linear or trapezoidal softening traction–Separation Law is used, but the influence of adhesive strength is not significant when exponential softening traction–Separation Law is used.
