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J.m. Emery - One of the best experts on this subject based on the ideXlab platform.

  • A simple cohesive zone Model that generates a Mode-Mixity dependent toughness
    International Journal of Solids and Structures, 2014
    Co-Authors: E.d. Reedy, J.m. Emery
    Abstract:

    A simple, Mode-Mixity dependent toughness cohesive zone Model (MDGc CZM) is described. This phenomenological cohesive zone Model has two elements. Mode I energy dissipation is defined by a traction–separation relationship that depends only on normal separation. Mode II (III) dissipation is generated by shear yielding and slip in the cohesive surface elements that lie in front of the region where Mode I separation (softening) occurs. The nature of predictions made by analyses that use the MDGc CZM is illustrated by considering the classic problem of an elastic layer loaded by rigid grips. This geometry, which Models a thin adhesive bond with a long interfacial edge crack, is similar to that which has been used to measure the dependence of interfacial toughness on crack-tip Mode-Mixity. The calculated effective toughness vs. applied Mode-Mixity relationships all display a strong dependence on applied Mode-Mixity with the effective toughness increasing rapidly with the magnitude of the Mode-Mixity. The calculated relationships also show a pronounced asymmetry with respect to the applied Mode-Mixity. As a result, this dependence is similar to that observed experimentally, and calculated results for a glass/epoxy interface are in good agreement with published data that was generated using a test specimen of themore » same type as analyzed here.« less

  • A simple cohesive zone Model that generates a Mode-Mixity dependent toughness
    International Journal of Solids and Structures, 2014
    Co-Authors: E.d. Reedy, J.m. Emery
    Abstract:

    AbstractA simple, Mode-Mixity dependent toughness cohesive zone Model (MDGc CZM) is described. This phenomenological cohesive zone Model has two elements. Mode I energy dissipation is defined by a traction–separation relationship that depends only on normal separation. Mode II (III) dissipation is generated by shear yielding and slip in the cohesive surface elements that lie in front of the region where Mode I separation (softening) occurs. The nature of predictions made by analyses that use the MDGc CZM is illustrated by considering the classic problem of an elastic layer loaded by rigid grips. This geometry, which Models a thin adhesive bond with a long interfacial edge crack, is similar to that which has been used to measure the dependence of interfacial toughness on crack-tip Mode-Mixity. The calculated effective toughness vs. applied Mode-Mixity relationships all display a strong dependence on applied Mode-Mixity with the effective toughness increasing rapidly with the magnitude of the Mode-Mixity. The calculated relationships also show a pronounced asymmetry with respect to the applied Mode-Mixity. This dependence is similar to that observed experimentally, and calculated results for a glass/epoxy interface are in good agreement with published data that was generated using a test specimen of the same type as analyzed here

E.d. Reedy - One of the best experts on this subject based on the ideXlab platform.

  • A simple cohesive zone Model that generates a Mode-Mixity dependent toughness
    International Journal of Solids and Structures, 2014
    Co-Authors: E.d. Reedy, J.m. Emery
    Abstract:

    A simple, Mode-Mixity dependent toughness cohesive zone Model (MDGc CZM) is described. This phenomenological cohesive zone Model has two elements. Mode I energy dissipation is defined by a traction–separation relationship that depends only on normal separation. Mode II (III) dissipation is generated by shear yielding and slip in the cohesive surface elements that lie in front of the region where Mode I separation (softening) occurs. The nature of predictions made by analyses that use the MDGc CZM is illustrated by considering the classic problem of an elastic layer loaded by rigid grips. This geometry, which Models a thin adhesive bond with a long interfacial edge crack, is similar to that which has been used to measure the dependence of interfacial toughness on crack-tip Mode-Mixity. The calculated effective toughness vs. applied Mode-Mixity relationships all display a strong dependence on applied Mode-Mixity with the effective toughness increasing rapidly with the magnitude of the Mode-Mixity. The calculated relationships also show a pronounced asymmetry with respect to the applied Mode-Mixity. As a result, this dependence is similar to that observed experimentally, and calculated results for a glass/epoxy interface are in good agreement with published data that was generated using a test specimen of themore » same type as analyzed here.« less

  • A simple cohesive zone Model that generates a Mode-Mixity dependent toughness
    International Journal of Solids and Structures, 2014
    Co-Authors: E.d. Reedy, J.m. Emery
    Abstract:

    AbstractA simple, Mode-Mixity dependent toughness cohesive zone Model (MDGc CZM) is described. This phenomenological cohesive zone Model has two elements. Mode I energy dissipation is defined by a traction–separation relationship that depends only on normal separation. Mode II (III) dissipation is generated by shear yielding and slip in the cohesive surface elements that lie in front of the region where Mode I separation (softening) occurs. The nature of predictions made by analyses that use the MDGc CZM is illustrated by considering the classic problem of an elastic layer loaded by rigid grips. This geometry, which Models a thin adhesive bond with a long interfacial edge crack, is similar to that which has been used to measure the dependence of interfacial toughness on crack-tip Mode-Mixity. The calculated effective toughness vs. applied Mode-Mixity relationships all display a strong dependence on applied Mode-Mixity with the effective toughness increasing rapidly with the magnitude of the Mode-Mixity. The calculated relationships also show a pronounced asymmetry with respect to the applied Mode-Mixity. This dependence is similar to that observed experimentally, and calculated results for a glass/epoxy interface are in good agreement with published data that was generated using a test specimen of the same type as analyzed here

Winston O. Soboyejo - One of the best experts on this subject based on the ideXlab platform.

  • Mode Mixity Dependence of Interfacial Fracture Toughness in Organic Electronic Structures
    IEEE Transactions on Device and Materials Reliability, 2014
    Co-Authors: Tiffany M. Tong, Nima Rahbar, Winston O. Soboyejo
    Abstract:

    This paper presents the results of a combined experimental and theoretical study of interfacial fracture in organic electronic structures. Interfacial fracture toughness is investigated as a function of Mode Mixity using Brazil disk specimens. The measured fracture toughness values are then compared with predictions determined from crack-tip shielding estimates and atomic force microscopy measurements of adhesion between layers that are relevant to organic electronic structures. The interfacial and layer fracture mechanics are elucidated before discussing the implications for the design of robust organic electronic structures.

  • Adhesion between a suspended polymeric film and a metallic substrate: Experiments and Models
    Journal of Materials Research, 2012
    Co-Authors: Emily Hampp, Wanliang Shan, George Papandreou, Cynthia A. Maryanoff, Winston O. Soboyejo
    Abstract:

    This paper presents the results of a combined experimental, theoretical, and computational study of the adhesion between suspended polymeric films and a substrate in a Model drug-eluting stent. Atomic force microscope is used to measure the pull-off force between the polymer and the substrate. The adhesion energy was then obtained from the measured pull-off forces and adhesion theories. Subsequently, the adhesion energy was incorporated into interfacial fracture mechanics zone Model that was used to determine Mode Mixity dependence of the interfacial fracture toughness. The Mode Mixity-dependent fracture toughness conditions were then integrated into finite element Models that were used to compute the critical push-out force of the suspended polymeric films. The predicted push-out forces were in good agreement with the results obtained from the experiments.

  • Mixed Mode fracture of marble/adhesive interfaces
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
    Co-Authors: Nima Rahbar, M. Jorjani, C. Riccardelli, George Segan Wheeler, I. Yakub, Winston O. Soboyejo
    Abstract:

    This paper presents the results of a combined experimental and theoretical study of the fracture of marble/adhesive interfaces that are relevant to the historic preservation and the conservation of marble artifacts. Thermoplastic and thermosetting adhesives are considered in this study as well as combinations of the two applied in sequence. The Mode Mixity dependence of interfacial fracture toughness is measured using Brazil-nut specimens. This dependence is also explained using a crack-shielding Model that accounts for the crack profiles and the contact between mating asperities.

Christian Berggreen - One of the best experts on this subject based on the ideXlab platform.

  • the effects of shear and near tip deformations on interface fracture of symmetric sandwich beams
    Engineering Fracture Mechanics, 2018
    Co-Authors: Luca Barbieri, Roberta Massabo, Christian Berggreen
    Abstract:

    Abstract The effects of shear on energy release rate and Mode Mixity in a symmetric sandwich beam with isotropic layers and a debond crack at the face-sheet/core interface are investigated through a semi-analytic approach based on two-dimensional elasticity and linear elastic fracture mechanics. The semi-analytic expressions for the shear components of energy release rate and Mode Mixity phase angle which have been derived in Li et al. (2004) for bi-material beams are extended to sandwich beams and the necessary numerical coefficients derived through accurate finite element analyses. The expressions are combined with earlier results for sandwich beams subjected to bending moments and axial forces in order to obtain solutions for general loading conditions and for an extensive range of geometrical and material properties. The physical and mechanical significance of the terms of the energy release rate which depend on the shear forces are explained using structural mechanics concepts and introducing crack tip root rotations to account for the main effects of the near tip deformations. The results are applicable to laboratory specimens used for the characterization of the fracture properties of sandwich composites for civil, marine, energy and aeronautical applications, provided the lengths of the crack and the ligament ahead of the crack tip are above minimum lengths which are defined in the paper.

  • the effects of shear and near tip deformations on interface fracture of symmetric sandwich beams
    arXiv: Soft Condensed Matter, 2018
    Co-Authors: Luca Barbieri, Roberta Massabo, Christian Berggreen
    Abstract:

    The effects of shear on energy release rate and Mode Mixity in a symmetric sandwich beam with isotropic layers and a debond crack at the face sheet/core interface are investigated through a semi-analytic approach based on two-dimensional elasticity and linear elastic fracture mechanics. Semi-analytic expressions are derived for the shear components of energy release rate and Mode Mixity phase angle which depend on four numerical coefficients derived through accurate finite element analyses. The expressions are combined with earlier results for three-layer configurations subjected to bending-moments and axial forces to obtain solutions for sandwich beams under general loading conditions and for an extensive range of geometrical and material properties. The results are applicable to laboratory specimens used for the characterization of the fracture properties of sandwich composites for civil, marine, energy and aeronautical applications, provided the lengths of the crack and the ligament ahead of the crack tip are above minimum lengths. The physical and mechanical significance of the terms of the energy release rate which depend on the shear forces are explained using structural mechanics concepts and introducing crack tip root rotations to account for the main effects of the near tip deformations.

  • energy release rate and Mode Mixity of face core debonds in sandwich beams
    AIAA Journal, 2013
    Co-Authors: George A. Kardomateas, Christian Berggreen, Leif A. Carlsson
    Abstract:

    Closed-form algebraic expressions for the energy-release rate and the Mode Mixity are obtained for a debonded sandwich (trimaterial). The most general case of an “asymmetric” sandwich is considered (i.e., the bottom face sheet not necessarily of the same material or thickness as the top face sheet). The energy-release rate is obtained by use of the J-integral, and the expression is derived in terms of the forces and moments at the debond section. Regarding the Mode Mixity, a closed-form expression is derived in terms of the geometry, material, and applied loading, and it is proven that, in the trimaterial case, just as in the bimaterial case, the Mode Mixity can be obtained in terms of a single scalar quantity ω, which is independent of loading; the ω value for a particular geometry and material can be extracted from a numerical solution for one loading combination. Thus, this analysis extends the existing formulas in the literature, which are for either a delamination in a homogeneous composite or an int...

  • Energy-Release Rate and Mode Mixity of Face/Core Debonds in Sandwich Beams
    AIAA Journal, 2013
    Co-Authors: George A. Kardomateas, Christian Berggreen, Leif A. Carlsson
    Abstract:

    Closed-form algebraic expressions for the energy-release rate and the Mode Mixity are obtained for a debonded sandwich (trimaterial). The most general case of an “asymmetric” sandwich is considered (i.e., the bottom face sheet not necessarily of the same material or thickness as the top face sheet). The energy-release rate is obtained by use of the J-integral, and the expression is derived in terms of the forces and moments at the debond section. Regarding the Mode Mixity, a closed-form expression is derived in terms of the geometry, material, and applied loading, and it is proven that, in the trimaterial case, just as in the bimaterial case, the Mode Mixity can be obtained in terms of a single scalar quantity ω, which is independent of loading; the ω value for a particular geometry and material can be extracted from a numerical solution for one loading combination. Thus, this analysis extends the existing formulas in the literature, which are for either a delamination in a homogeneous composite or an int...

  • face core interface fracture characterization of mixed Mode bending sandwich specimens
    Fatigue & Fracture of Engineering Materials & Structures, 2011
    Co-Authors: Amilcar Quispitupa, Christian Berggreen, Leif A. Carlsson
    Abstract:

    Debonding of the core from the face sheets is a critical failure Mode in sandwich structures. This paper presents an experimental study on face/core debond fracture of foam core sandwich specimens under a wide range of mixed Mode loading conditions. Sandwich beams with E-glass fibre face sheets and PVC H45, H100 and H250 foam core materials were evaluated. A methodology to perform precracking on fracture specimens in order to achieve a sharp and representative crack front is outlined. The mixed Mode loading was controlled in the mixed Mode bending (MMB) test rig by changing the loading application point (lever arm distance). Finite element analysis was performed to determine the Mode-Mixity at the crack tip. The results showed that the face/core interface fracture toughness increased with increased Mode II loading. Post failure analysis of the fractured specimens revealed that the crack path depends on the Mode-Mixity at the crack tip, face sheet properties and core density.

V.n. Shlyannikov - One of the best experts on this subject based on the ideXlab platform.

  • generalization of mixed Mode crack behaviour by the plastic stress intensity factor
    Theoretical and Applied Fracture Mechanics, 2017
    Co-Authors: V.n. Shlyannikov, A.p. Zakharov
    Abstract:

    Abstract An elastic–plastic finite element analysis is performed for cruciform specimens of two configurations and a compact tension–shear specimen subjected to mixed Mode I/II loading. A Ramberg–Osgood stress–strain relation is used to characterise the properties of two types of steel and titanium and aluminium alloys. For the specified geometry of the specimen considered, the governing parameter of the elastic–plastic crack-tip stress field In factor, the stress triaxiality, and the plastic stress intensity factor are determined as a function of Mode Mixity and elastic–plastic material properties. Special emphasis is put on the analysis of the effect of specimen geometry. Analytical and numerical results are compared for the complete range of mixed-Mode loading. A correlation between the plastic stress intensity factor and the constraint parameter based on the numerical analysis is found. Coupling between Mode Mixity and material nonlinearity is indicated. The applicability of the plastic stress intensity factor approach to large-scale yielding analysis is also discussed.

  • multiaxial crack growth rate under variable t stress
    Engineering Fracture Mechanics, 2014
    Co-Authors: V.n. Shlyannikov, A.p. Zakharov
    Abstract:

    Abstract Fatigue crack growth rate are studied through experiments and numerical computations under different biaxial and mixed-Mode loading conditions. Cruciform specimens under biaxial loading and compact tension–shear specimens are considered. The different degrees of Mode Mixity from pure Mode I to pure Mode II are given by the combinations of the far-field stress level, load biaxiality and inclined crack angle. For the particular specimen geometries considered, the T-stress and the numerical constant of the plastic stress field distributions In are obtained as a function of the dimensionless crack length, load biaxiality and Mode Mixity. A method is also suggested for calculating the plastic stress intensity factor for any mixed-Mode I/II loading based on the T-stress and power law solutions. It is further demonstrated that the plastic stress intensity factor accounting for the in-plane and out-of-plane constraint effect can be used to characterize the multiaxial crack growth rate for a variety of specimen geometries.

  • Characterization of crack tip stress fields in test specimens using Mode Mixity parameters
    International Journal of Fracture, 2014
    Co-Authors: V.n. Shlyannikov, Alexei V. Tumanov
    Abstract:

    The aim of this study is to represent the combined effect of Mode Mixity, specimen geometry and relative crack length on the $$T$$ T -stress, elastic–plastic stress fields, integration constant $$I_{n}$$ I n , angle of initial crack extension, and the plastic stress intensity factor. The analytical and numerical results are obtained for the complete range of mixed Modes of loading between Mode I and Mode II. For comparison purposes, the reference fields for plane mixed-Mode problems governing the asymptotic behavior of the stresses and strains at the crack tip are developed in a power law elastic–plastic material. For the common experimental fracture mechanics specimen geometries considered, the numerical constant of the plastic stress field $$I_{n}$$ I n and the $$T$$ T -stress distributions are obtained as a function of the dimensionless crack length and Mode Mixity. A method is also suggested for calculating the plastic stress intensity factor for any mixed-Mode I/II loading based on the $$T$$ T -stress and power law solutions. It is further demonstrated that in both plane stress and the plane strain, the plastic stress intensity factor can be used to characterize the crack tip stress fields for a variety of specimen geometries and different mixed-Mode loading. The applicability of the plastic stress intensity factor to analysis of the in-plane and out-of-plane constraint effect is also discussed.

  • An inclined surface crack subject to biaxial loading
    International Journal of Solids and Structures, 2011
    Co-Authors: V.n. Shlyannikov, Alexei V. Tumanov
    Abstract:

    Abstract The elastic–plastic stress fields and Mode Mixity parameters for semi-elliptical surface cracks on biaxial loaded plates have been investigated using detailed three-dimensional finite element calculations. Different degrees of Mode Mixity are given by combinations of the far-field stress level, biaxial stress ratio and inclined crack angle. These analyses were performed for different surface flaw geometries to study the combined load biaxiality and Mode Mixity effects on the crack-front stress fields and the size and shape of the plastic zones. It is clear from considering the local stress distributions along the crack front that the elastic crack tip singularities have been derived for several particular cases of mixed Mode biaxial loading. By theoretical analysis, the new formulae have been introduced for both the elastic and plastic Mode-Mixity parameters, accounting for ratios between the I/II, II/III and III/I Modes. Particular attention was paid to the strong variations of the Mode-Mixity parameters along the semi-elliptical surface crack front. The mixed-Mode behavior of the crack growth direction angle along the semi-elliptical crack front for different combinations of biaxial loading and inclination crack angles was also determined. It was done using methods based on the maximum tangential stress and the strain energy density criteria.