The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Bin Liu - One of the best experts on this subject based on the ideXlab platform.
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a Cohesive law for carbon nanotube polymer interfaces based on the van der waals force
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: Liying Jiang, Yonggang Huang, Keh Chih Hwang, Hanqing Jiang, G. Ravichandran, Huajian Gao, Bin LiuAbstract:We have established the Cohesive law for interfaces between a carbon nanotube (CNT) and polymer that are not well bonded and are characterized by the van der Waals force. The tensile Cohesive strength and Cohesive energy are given in terms of the area density of carbon nanotube and volume density of polymer, as well as the parameters in the van der Waals force. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. For a CNT in a finite polymer matrix, the tensile Cohesive Stress remains the same, but the shear Cohesive Stress depends on both opening and sliding displacements, i.e., the tension/shear coupling. The simple, analytical expressions of the Cohesive law are useful to study the interaction between CNT and polymer, such as in CNT-reinforced composites. The effect of polymer surface roughness on the Cohesive law is also studied.
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A Cohesive law for carbon nanotube/polymer interfaces based on the van der Waals force
Journal of the Mechanics and Physics of Solids, 2006Co-Authors: Liying Jiang, Yonggang Huang, Keh Chih Hwang, Hanqing Jiang, G. Ravichandran, Huajian Gao, Bin LiuAbstract:We have established the Cohesive law for interfaces between a carbon nanotube (CNT) and polymer that are not well bonded and are characterized by the van der Waals force. The tensile Cohesive strength and Cohesive energy are given in terms of the area density of carbon nanotube and volume density of polymer, as well as the parameters in the van der Waals force. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. For a CNT in a finite polymer matrix, the tensile Cohesive Stress remains the same, but the shear Cohesive Stress depends on both opening and sliding displacements, i.e., the tension/shear coupling. The simple, analytical expressions of the Cohesive law are useful to study the interaction between CNT and polymer, such as in CNT-reinforced composites. The effect of polymer surface roughness on the Cohesive law is also studied.
Kaixin Liu - One of the best experts on this subject based on the ideXlab platform.
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Crack propagation in viscoplastic polymers: Heat generation in near-tip zone and viscoplastic Cohesive model
Applied Physics Letters, 2015Co-Authors: Yuansha Chen, Kaixin LiuAbstract:We develop a precise experimental method to measure the full-field heat-generating process near moving (mode I) crack tips in polycarbonate films and present the experimental image of crack tip structure in viscoplastic polymers. A viscoplastic Cohesive model is constructed to analyze the mechanical state and temperature increase in near-tip zone during steady crack propagation. The Cohesive Stress in this model is uniquely characterized by viscoplastic constitutive equation instead of traction-separation displacement relationship or constant yield Stress, which greatly differs from previous models. Our proposed model's prediction of temperature increase agrees well with the experimental result.
Liying Jiang - One of the best experts on this subject based on the ideXlab platform.
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A Cohesive Law for Carbon Nanotube/Polymer Interface Accounting for Chemical Covalent Bonds
Mathematics and Mechanics of Solids, 2010Co-Authors: Liying JiangAbstract:The influence of chemical bonds formed between a single-walled carbon nanotube (CNT) and a polymer matrix upon the interface behavior has been studied through the development of an interfacial Cohesive law. By using the interatomic potential directly, the tensile Cohesive Stress and Cohesive energy for the interface with opening mode separation are expressed in terms of the area density of the carbon atoms of the CNT, the volume density of the polymer molecules, the material constants of the CNT and the polymer matrix, the parameters in the van der Waals potential, and the Brenner potential and the chemical bond density. This Cohesive law avoids any phenomenological assumption between the normal traction and interface opening displacement. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. The Cohesive properties, such as the total Cohesive energy, have increased significantly, which results in a stronger interfac...
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a Cohesive law for carbon nanotube polymer interface accounting for chemical covalent bonds
Mathematics and Mechanics of Solids, 2010Co-Authors: Liying JiangAbstract:The influence of chemical bonds formed between a single-walled carbon nanotube (CNT) and a polymer matrix upon the interface behavior has been studied through the development of an interfacial Cohesive law. By using the interatomic potential directly, the tensile Cohesive Stress and Cohesive energy for the interface with opening mode separation are expressed in terms of the area density of the carbon atoms of the CNT, the volume density of the polymer molecules, the material constants of the CNT and the polymer matrix, the parameters in the van der Waals potential, and the Brenner potential and the chemical bond density. This Cohesive law avoids any phenomenological assumption between the normal traction and interface opening displacement. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. The Cohesive properties, such as the total Cohesive energy, have increased significantly, which results in a stronger interfac...
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A Cohesive law for multi-wall carbon nanotubes
Philosophical Magazine, 2007Co-Authors: Liying Jiang, Yonggang Huang, Kuo Chu Hwang, Bo LiuAbstract:We have established the Cohesive law for carbon nanotube (CNT) walls in multi-wall CNTs. The interactions between CNT walls are characterized by the van der Waals force. The tensile Cohesive strength and Cohesive energy are given in terms of the area density of CNT and parameters in the van der Waals force. For an infinitely long CNT, the shear Cohesive Stress between CNT walls vanishes, and the tensile Cohesive Stress depends only on the opening displacement. For a finite CNT, the tensile Cohesive Stress remains the same, but the shear Cohesive Stress depends on both opening and sliding displacements, i.e. the tension/shear coupling. The simple, analytical expressions of the Cohesive law are useful to study the interaction between walls in multi-wall CNTs.
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a Cohesive law for carbon nanotube polymer interfaces based on the van der waals force
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: Liying Jiang, Yonggang Huang, Keh Chih Hwang, Hanqing Jiang, G. Ravichandran, Huajian Gao, Bin LiuAbstract:We have established the Cohesive law for interfaces between a carbon nanotube (CNT) and polymer that are not well bonded and are characterized by the van der Waals force. The tensile Cohesive strength and Cohesive energy are given in terms of the area density of carbon nanotube and volume density of polymer, as well as the parameters in the van der Waals force. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. For a CNT in a finite polymer matrix, the tensile Cohesive Stress remains the same, but the shear Cohesive Stress depends on both opening and sliding displacements, i.e., the tension/shear coupling. The simple, analytical expressions of the Cohesive law are useful to study the interaction between CNT and polymer, such as in CNT-reinforced composites. The effect of polymer surface roughness on the Cohesive law is also studied.
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A Cohesive law for carbon nanotube/polymer interfaces based on the van der Waals force
Journal of the Mechanics and Physics of Solids, 2006Co-Authors: Liying Jiang, Yonggang Huang, Keh Chih Hwang, Hanqing Jiang, G. Ravichandran, Huajian Gao, Bin LiuAbstract:We have established the Cohesive law for interfaces between a carbon nanotube (CNT) and polymer that are not well bonded and are characterized by the van der Waals force. The tensile Cohesive strength and Cohesive energy are given in terms of the area density of carbon nanotube and volume density of polymer, as well as the parameters in the van der Waals force. For a CNT in an infinite polymer, the shear Cohesive Stress vanishes, and the tensile Cohesive Stress depends only on the opening displacement. For a CNT in a finite polymer matrix, the tensile Cohesive Stress remains the same, but the shear Cohesive Stress depends on both opening and sliding displacements, i.e., the tension/shear coupling. The simple, analytical expressions of the Cohesive law are useful to study the interaction between CNT and polymer, such as in CNT-reinforced composites. The effect of polymer surface roughness on the Cohesive law is also studied.
Kolluru V. L. Subramaniam - One of the best experts on this subject based on the ideXlab platform.
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Influence of Cohesive Stresses on shear capacity of reinforced SFRC beams without stirrups: A discrete crack approach
Engineering Fracture Mechanics, 2019Co-Authors: Sahith Gali, Kolluru V. L. SubramaniamAbstract:Abstract An experimental investigation on the fracture behavior and the dilatant crack opening in the shear response of concrete with discrete steel fiber reinforcement is presented. Hooked-ended steel fibers are used at 0.5% and 0.75% volume fractions. From the experimental fracture response of steel fiber reinforced concrete beams, the Cohesive Stress-crack opening relationship is derived using the cracked hinge model. Load tests are conducted on laboratory-sized reinforced concrete beams without steel stirrups, designed to fail in shear. The crack growth and propagation in the shear behavior of concrete with and without fibers are evaluated from displacements measured using digital image correlation (DIC). The in-situ dilatant behavior of the shear crack is established from the slip and the crack opening displacements measured across the critical shear crack. A discrete crack-based formulation with internal contact forces on the crack faces and Cohesive Stress from fibers is developed for predicting the shear capacity of a reinforced concrete beam. The discrete crack-based model is derived using the physical observation on cracks in the reinforced concrete beams. The prediction of the model includes an increase in the contact forces with an increase in the fiber force at peak shear resistance with an increasing volume fraction of fibers. The additional contact forces mobilized across the crack by the fibers maintains the shear transfer across the crack and hence the load carrying capacity is sustained for a larger crack opening. The model derived from laboratory-sized specimens accurately predicts the scaling of the shear capacity with the size of the beam.
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analysis for multi linear Stress crack opening Cohesive relationship application to macro synthetic fiber reinforced concrete
Engineering Fracture Mechanics, 2017Co-Authors: Chiranjeevi K Reddy, Kolluru V. L. SubramaniamAbstract:Abstract An analytical formulation for flexure behaviour of concrete considering a multi-linear Stress-crack separation (σ-w) relationship is developed using the cracked hinge model. An inversion procedure for obtaining the multi-linear Cohesive Stress response from the flexural load response of a beam is presented. The procedure is applied to obtain the σ-w relationship for macro-synthetic fiber reinforced concrete. An experimental investigation of the crack propagation in flexural response of macro-synthetic fiber reinforced concrete is presented using the digital image correlation technique. The post-cracking response of macro-synthetic fiber reinforced concrete during the initial softening and the subsequent load recovery is experimentally shown to be associated with a hinge-type behaviour and is produced by crack closing Stresses contributed by fibers. From the optical measurements the hinge length is identified with a zone of length equal to twice the aggregate size. Using the measured hinge length, the multi-linear σ-w relationship for macro-synthetic fiber reinforced concrete obtained by matching the experimental and the analytical load responses exhibits a Stress recovery following initial softening. The Cohesive Stress subsequently decreases following the recovery at large crack separation. The crack closing Stresses contributed by the pullout of fibers produce Stress recovery in the σ-w relationship and are primarily active after the formation of the hinge resulting in significant contribution to fracture energy at large crack openings. There is a good correlation in the fracture energy obtained from load response and the σ-w relationship at different values of crack opening displacements.
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Influence of variation in the local interface fracture properties on shear debonding of CFRP composite from concrete
Journal of Adhesion Science and Technology, 2016Co-Authors: Kolluru V. L. Subramaniam, Michel Ghosn, Mohamad Ali-ahmadAbstract:AbstractThe debonding mode of failure, which is observed in concrete beams strengthened using externally attached CFRP composite sheets, is investigated using the direct shear test. The Mode II, Cohesive Stress-crack relative slip relationship is established using full-field displacements obtained from digital image correlation. The interface crack is associated with a Cohesive Stress-transfer zone of fixed length. The load capacity of the CFRP composite bonded to concrete is attained when the Cohesive crack is fully established. The acoustic emission monitored during the interface fracture initiation and propagation indicates that microcracking events accumulate at a constant rate up to failure. The variations in the local fracture parameters are quantified and are adequately represented using the normal probability distribution. A numerical analysis of the direct-shear debonding response of CFRP composite attached to a concrete substrate is performed to study the influence of the variability of the loca...
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an understanding of the width effect in frp concrete debonding
Strain, 2011Co-Authors: Kolluru V. L. Subramaniam, Christian Carloni, Lucio NobileAbstract:: The scaling of the ultimate load in fibre-reinforced polymer (FRP)–concrete debonding with the relative width of the FRP is experimentally investigated in this paper. Shear debonding tests are performed to evaluate the Cohesive Stress transfer between the adherents during the interface crack growth which produces debonding. Concrete specimens with two different widths and different widths of FRP are used in the experimental programme. The nominal Stress at debonding increases with the FRP-to-concrete width ratio. For a given width of FRP composite sheet, lower debonding Stress is obtained from concrete specimens with a larger width. The strain distribution on the FRP and concrete free surface at different stages of debonding was determined using a full-field optical technique known as digital image correlation. The contribution of the two factors, the boundary effect and the restraint from the surrounding concrete, was studied from the measured strain distribution. The strain distributions across the FRP composite sheet and the concrete within the Cohesive Stress transfer zone associated with the interface crack are shown to be very inhomogeneous. A region of constant width associated with high shear strains is found at the edge of the FRP sheet during the entire debonding process. The increase in the ultimate nominal Stress at debonding is shown to be due to the decrease in the proportion of the total width of the FRP occupied by the edge region. It is shown that the boundary region within the FRP is of a fixed width. The width of concrete close to the edge of the FRP involved in Stress transfer, however, increases with the width of FRP. It is established that when the FRP-to-concrete width ratio is smaller than 0.5, the level of restraint from concrete increases with the FRP width.
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An Understanding of the Width Effect in FRP–Concrete Debonding
Strain, 2011Co-Authors: Kolluru V. L. Subramaniam, Christian Carloni, Lucio NobileAbstract:: The scaling of the ultimate load in fibre-reinforced polymer (FRP)–concrete debonding with the relative width of the FRP is experimentally investigated in this paper. Shear debonding tests are performed to evaluate the Cohesive Stress transfer between the adherents during the interface crack growth which produces debonding. Concrete specimens with two different widths and different widths of FRP are used in the experimental programme. The nominal Stress at debonding increases with the FRP-to-concrete width ratio. For a given width of FRP composite sheet, lower debonding Stress is obtained from concrete specimens with a larger width. The strain distribution on the FRP and concrete free surface at different stages of debonding was determined using a full-field optical technique known as digital image correlation. The contribution of the two factors, the boundary effect and the restraint from the surrounding concrete, was studied from the measured strain distribution. The strain distributions across the FRP composite sheet and the concrete within the Cohesive Stress transfer zone associated with the interface crack are shown to be very inhomogeneous. A region of constant width associated with high shear strains is found at the edge of the FRP sheet during the entire debonding process. The increase in the ultimate nominal Stress at debonding is shown to be due to the decrease in the proportion of the total width of the FRP occupied by the edge region. It is shown that the boundary region within the FRP is of a fixed width. The width of concrete close to the edge of the FRP involved in Stress transfer, however, increases with the width of FRP. It is established that when the FRP-to-concrete width ratio is smaller than 0.5, the level of restraint from concrete increases with the FRP width.
Yuansha Chen - One of the best experts on this subject based on the ideXlab platform.
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Crack propagation in viscoplastic polymers: Heat generation in near-tip zone and viscoplastic Cohesive model
Applied Physics Letters, 2015Co-Authors: Yuansha Chen, Kaixin LiuAbstract:We develop a precise experimental method to measure the full-field heat-generating process near moving (mode I) crack tips in polycarbonate films and present the experimental image of crack tip structure in viscoplastic polymers. A viscoplastic Cohesive model is constructed to analyze the mechanical state and temperature increase in near-tip zone during steady crack propagation. The Cohesive Stress in this model is uniquely characterized by viscoplastic constitutive equation instead of traction-separation displacement relationship or constant yield Stress, which greatly differs from previous models. Our proposed model's prediction of temperature increase agrees well with the experimental result.