The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Toshiyuki Hashida - One of the best experts on this subject based on the ideXlab platform.
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effect of fiber volume fraction on the off Crack Plane fracture energy in strain hardening engineered cementitious composites
Journal of the American Ceramic Society, 1995Co-Authors: Mohamed Maalej, Toshiyuki HashidaAbstract:In this paper, the results of an experimental study on the effect of fiber volume fraction on the off-Crack-Plane fracture energy in a strain-hardening engineered cementitious composite (ECC) are presented. Unlike the well-known quasi-brittle behavior of fiber-reinforced concrete, ECC exhibits quasi-ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material is microCracked but continues to strain-harden locally. The areal dimension of the damage zone has been observed to be on the order of 1,000 cm{sup 2} in double cantilever beam specimens. The energy absorption of the off-Crack-Plane inelastic deformation process has been measured to be more than 50% of the total fracture energy of up to 34 kJ/m{sup 2}. This magnitude of fracture energy is the highest ever reported for a fiber cementitious composite.
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Effect of Fiber Volume Fraction on the Off‐Crack‐Plane Fracture Energy in Strain ‐Hardening Engineered Cementitious Composites
Journal of the American Ceramic Society, 1995Co-Authors: Mohamed Maalej, Toshiyuki HashidaAbstract:In this paper, the results of an experimental study on the effect of fiber volume fraction on the off-Crack-Plane fracture energy in a strain-hardening engineered cementitious composite (ECC) are presented. Unlike the well-known quasi-brittle behavior of fiber-reinforced concrete, ECC exhibits quasi-ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material is microCracked but continues to strain-harden locally. The areal dimension of the damage zone has been observed to be on the order of 1,000 cm{sup 2} in double cantilever beam specimens. The energy absorption of the off-Crack-Plane inelastic deformation process has been measured to be more than 50% of the total fracture energy of up to 34 kJ/m{sup 2}. This magnitude of fracture energy is the highest ever reported for a fiber cementitious composite.
Mohamed Maalej - One of the best experts on this subject based on the ideXlab platform.
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effect of fiber volume fraction on the off Crack Plane fracture energy in strain hardening engineered cementitious composites
Journal of the American Ceramic Society, 1995Co-Authors: Mohamed Maalej, Toshiyuki HashidaAbstract:In this paper, the results of an experimental study on the effect of fiber volume fraction on the off-Crack-Plane fracture energy in a strain-hardening engineered cementitious composite (ECC) are presented. Unlike the well-known quasi-brittle behavior of fiber-reinforced concrete, ECC exhibits quasi-ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material is microCracked but continues to strain-harden locally. The areal dimension of the damage zone has been observed to be on the order of 1,000 cm{sup 2} in double cantilever beam specimens. The energy absorption of the off-Crack-Plane inelastic deformation process has been measured to be more than 50% of the total fracture energy of up to 34 kJ/m{sup 2}. This magnitude of fracture energy is the highest ever reported for a fiber cementitious composite.
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Effect of Fiber Volume Fraction on the Off‐Crack‐Plane Fracture Energy in Strain ‐Hardening Engineered Cementitious Composites
Journal of the American Ceramic Society, 1995Co-Authors: Mohamed Maalej, Toshiyuki HashidaAbstract:In this paper, the results of an experimental study on the effect of fiber volume fraction on the off-Crack-Plane fracture energy in a strain-hardening engineered cementitious composite (ECC) are presented. Unlike the well-known quasi-brittle behavior of fiber-reinforced concrete, ECC exhibits quasi-ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material is microCracked but continues to strain-harden locally. The areal dimension of the damage zone has been observed to be on the order of 1,000 cm{sup 2} in double cantilever beam specimens. The energy absorption of the off-Crack-Plane inelastic deformation process has been measured to be more than 50% of the total fracture energy of up to 34 kJ/m{sup 2}. This magnitude of fracture energy is the highest ever reported for a fiber cementitious composite.
Nancy R Sottos - One of the best experts on this subject based on the ideXlab platform.
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Autonomic healing of carbon fiber/epoxy interfaces.
ACS applied materials & interfaces, 2014Co-Authors: Amanda R. Jones, Scott R. White, Alicia Cintora, Nancy R SottosAbstract:A maximum of 91% recovery of interfacial shear strength (IFSS) is achieved for carbon fiber/epoxy interfaces functionalized with capsules containing reactive epoxy resin and ethyl phenyl acetate (EPA). We find a binder is necessary to improve the retention of capsules on the carbon fiber surface. Two different methods for applying the binder to the carbon fiber surface are investigated. Healing efficiency is assessed by recovery of IFSS of a single functionalized fiber embedded in a microdroplet of epoxy. Debonding of the fiber/matrix interface ruptures the capsules, releasing resin and EPA solvent into the Crack Plane. The solvent swells the matrix, initiating transport of residual amine functionality from the matrix for further curing with the epoxy resin delivered to the Crack Plane. The two binder protocols produce comparable results, both yielding higher recovery of IFSS than samples prepared without a binder.
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full recovery of fiber matrix interfacial bond strength using a microencapsulated solvent based healing system
Composites Science and Technology, 2013Co-Authors: Amanda R. Jones, Scott R. White, Benjamin J Blaiszik, Nancy R SottosAbstract:Abstract Full recovery of interfacial bond strength after complete fiber/matrix debonding is achieved with a microencapsulated solvent-based healing chemistry. The surface of a glass fiber is functionalized with microcapsules containing varying concentrations of reactive epoxy resin and ethyl phenylacetate (EPA) solvent. Microbond specimens consisting of a single fiber and a microdroplet of epoxy are tested, and the interfacial shear strengths (IFSSs) during the initial (virgin) debonding and subsequent healing events are measured. Debonding of the fiber/matrix interface ruptures the capsules, releasing resin and solvent into the Crack Plane. The solvent swells the matrix, initiating transport of residual amine functionality for further curing with the epoxy resin delivered to the Crack Plane. Using a resin-solvent ratio of 3:97, we achieve a maximum of 100% IFSS recovery–a significant enhancement over prior work that reported 44% average recovery of IFSS with microencapsulated dicyclopentadiene (DCPD) monomer and Grubbs’ 1st Generation catalyst healing agents. The effects of capsule coverage, resin-solvent ratio, and capsule size on recovery of IFSS are also determined, providing guidelines for integration of this healing system into high fiber volume fraction structural composites. High healing efficiencies were achieved with capsules as small as 0.6 μm average diameter.
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Delivery of two-part self-healing chemistry via microvascular networks
Advanced Functional Materials, 2009Co-Authors: Kathleen S. Toohey, Christopher J. Hansen, Scott R. White, Jennifer A Lewis, Nancy R SottosAbstract:Multiple healing cycles of a single Crack in a brittle polymer coating are achieved by microvascular delivery of a two part, epoxy-based self-healing chemistry. Epoxy resin and a mine-based curing agents are transported to the Crack Plane through two sets of independent vascular networks embedded within a ductile polymer substrate beneath the coating. The two reactive components remain isolated and stable in the vascular networks until Crack formation occurs in the coating under a mechanical load. Both healing components are wicked by capillary forces into the Crack Plane, where they react and effectively bond the Crack faces closed. Healing efficiencies of over 60% are achieved for up to 16 intermittent healing cycles of a single Crack, which represents a significant improvement over systems in which a single monomeric healing agent is delivered.
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retardation and repair of fatigue Cracks in a microcapsule toughened epoxy composite part i manual infiltration
Composites Science and Technology, 2005Co-Authors: Eric Brown, Scott R. White, Nancy R SottosAbstract:Abstract As a first step towards a new Crack healing methodology for cyclic loading, this paper examines two promising Crack-tip shielding mechanisms during fatigue of a microcapsule toughened epoxy. Artificial Crack closure is achieved by injecting precatalyzed monomer into the Crack Plane to form a polymer wedge at the Crack tip. The effect of wedge geometry is also considered, as dictated by Crack loading conditions during infiltration. Crack-tip shielding by a polymer wedge formed with the Crack held open under the maximum cyclic loading condition (Kmax) yields temporary Crack arrest and extends the fatigue life by more than 20 times. Hydrodynamic pressure and viscous damping as a mechanism of Crack-tip shielding are also investigated by injecting mineral oil into the Crack Plane. Viscous fluid flow leads to retardation of Crack growth independent of initial loading conditions. The success of these mechanisms for retarding fatigue Crack growth demonstrates the potential for in situ self-healing of fatigue damage.
Veera Sundararaghavan - One of the best experts on this subject based on the ideXlab platform.
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a grain boundary interaction model for microstructurally short fatigue Cracks
International Journal of Fatigue, 2018Co-Authors: Shardul Panwar, J F Adams, J E Allison, J W Jones, Veera SundararaghavanAbstract:Abstract In this paper, we present a phenomenological model for simulating the effect of a grain boundary on Crack growth along crystallographic Planes. This model combines various geometrical features of the interaction between the Crack Plane and the grain boundary Plane. The tilt and twist misorientations, calculated at a grain boundary, between a Crack Plane and a favorable Plane in the next grain are incorporated into this model, as are the Schmid factor of the next grain and a critical Crack transmission stress. A model calibration procedure is demonstrated based on experimental short fatigue Crack growth data measured in a high performance wrought magnesium alloy. The proposed combined GB interaction model is shown to accurately predict the short fatigue Crack growth retardation and arrest at grain boundaries in this alloy.
Viggo Tvergaard - One of the best experts on this subject based on the ideXlab platform.
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Crack growth resistance for anisotropic plasticity with non-normality effects
International Journal of Solids and Structures, 2006Co-Authors: Viggo Tvergaard, Brian Nyvang LegarthAbstract:AbstractFor a plastically anisotropic solid a plasticity model using a plastic flow rule with non-normality is applied to predict Crack growth. The fracture process is modelled in terms of a traction–separation law specified on the Crack Plane. A phenomenological elastic–viscoplastic material model is applied, using one of two different anisotropic yield criteria to account for the plastic anisotropy, and in each case the effect of the normality flow rule is compared with the effect of non-normality. Conditions of small scale yielding are assumed, with mode I loading conditions far from the Crack-tip, and various directions of the Crack Plane relative to the principal axes of the anisotropy are considered. It is found that the steady-state fracture toughness is significantly reduced when the non-normality flow rule is used. Furthermore, it is shown that the predictions are quite sensitive to the value of the maximum angle of deviation from normality in the non-normality flow rule
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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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theoretical investigation of the effect of plasticity on Crack growth along a functionally graded region between dissimilar elastic plastic solids
Engineering Fracture Mechanics, 2002Co-Authors: Viggo TvergaardAbstract:Abstract The influence of a functionally graded layer joining dissimilar elastic–plastic solids is studied in relation to interface Crack growth. Conditions of small scale yielding are considered, and the boundary conditions applied on the outer edge of the region analysed are displacements for the elastic oscillating stress singularity fields corresponding to a sharp interface. A cohesive zone model is used to represent the fracture process, where the work of separation per unit area and the peak stress are basic parameters. Only Crack growth on the initial Crack Plane parallel to the graded layer is analysed, but different locations of the Crack Plane relative to the layer are considered to obtain a parametric understanding. Crack growth resistance curves are illustrated, and the dependence of the steady-state fracture toughness on mode mixity is presented for several combinations of material parameters.
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Theoretical investigation of the effect of plasticity on Crack growth along a functionally graded region between dissimilar elastic–plastic solids
Engineering Fracture Mechanics, 2002Co-Authors: Viggo TvergaardAbstract:Abstract The influence of a functionally graded layer joining dissimilar elastic–plastic solids is studied in relation to interface Crack growth. Conditions of small scale yielding are considered, and the boundary conditions applied on the outer edge of the region analysed are displacements for the elastic oscillating stress singularity fields corresponding to a sharp interface. A cohesive zone model is used to represent the fracture process, where the work of separation per unit area and the peak stress are basic parameters. Only Crack growth on the initial Crack Plane parallel to the graded layer is analysed, but different locations of the Crack Plane relative to the layer are considered to obtain a parametric understanding. Crack growth resistance curves are illustrated, and the dependence of the steady-state fracture toughness on mode mixity is presented for several combinations of material parameters.
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effect of t stress on mode i Crack growth resistance in a ductile solid
International Journal of Solids and Structures, 1994Co-Authors: Viggo Tvergaard, J W HutchinsonAbstract:Abstract An elastic-plastic Crack growth model, with a traction-separation law specified on the Crack Plane to characterize the fracture process, is used to study the effect of the non-singular T -stress, acting parallel to the Crack Plane. The work of separation per unit area and the peak normal stress are the two main parameters used to characterize the fracture process, and Crack growth resistance curves are calculated numerically for a number of values of the peak stress to initial yield stress ratio, and for different levels of strain hardening. Small-scale yielding in Plane strain is considered with the remote field specified by a constant value of the T -stress, applied initially, and an increasing magnitude of the mode I stress intensity factor. It is shown that the predicted T -stress dependence of the fracture toughness during Crack growth is qualitatively similar to experimental observations, even though the experiments go beyond small-scale yielding.