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Guoqiang Li - One of the best experts on this subject based on the ideXlab platform.
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Damage healing ability of a shape-memory-polymer-based particulate composite with small thermoplastic contents
Smart Materials and Structures, 2012Co-Authors: Jones Nji, Guoqiang LiAbstract:The purpose of this study is to investigate the potential of a shape-memory-polymer (SMP)-based particulate composite to heal structural-length Scale Damage with small thermoplastic additive contents through a close-then-heal (CTH) self-healing scheme that was introduced in a previous study (Li and Uppu 2010 Comput. Sci. Technol. 70 1419–27). The idea is to achieve reasonable healing efficiencies with minimal sacrifice in structural load capacity. By first closing cracks, the gap between two crack surfaces is narrowed and a lesser amount of thermoplastic particles is required to achieve healing. The particulate composite was fabricated by dispersing copolyester thermoplastic particles in a shape memory polymer matrix. It is found that, for small thermoplastic contents of less than 10%, the CTH scheme followed in this study heals structural-length Scale Damage in the SMP particulate composite to a meaningful extent and with less sacrifice of structural capacity.
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a biomimic shape memory polymer based self healing particulate composite
Polymer, 2010Co-Authors: Guoqiang LiAbstract:Abstract In a previous study, a biomimic two-step self-healing scheme (close-then-heal (CTH)) by mimicking human skin has been proposed for self-healing structural-length Scale Damage [Li and Uppu. Composites Science and Technology 2010; 70: 1419–1427]. The purpose of this study is to validate this idea by fabricating a composite with thermoplastic particles (Copolyster) dispersed in a shape memory polymer matrix ( Veriflex Polystyrene). In this particulate composite, the confined shape recovery of the shape memory matrix is utilized for sealing (closing) cracks and the thermoplastic particles are used for molecular-length Scale healing. In this study, 6% by volume of thermoplastic particles was used. Beam specimens were prepared and programmed by compression in the longitudinal direction to 6.7% of pre-strain. Structural-length Scale Damage was then created by producing a notch in the programmed beam specimens per ASTM D 5045. The notched beam specimens were then tested to fracture. The fractured specimens were healed per the close-then-heal mechanism and tested again to fracture. This fracture-healing test lasted for 5 cycles. The healing efficiency was evaluated per the peak-bending load. SEM was used to examine healed cracks at micro-length Scale while EDS was used to evaluate molecular-length Scale healing. It is found that over 65% of the peak bending load can be repeatedly recovered and the structural-length Scale Damage (notch) is healed at molecular-length Scale.
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thermomechanical characterization of a shape memory polymer based self repairing syntactic foam
Polymer, 2010Co-Authors: Guoqiang Li, Damon NettlesAbstract:Abstract While the current self-healing approaches such as micro-capsules, hollow fibers, thermally reversible covalent bonds, ionomers, incorporation of thermoplastic particles, etc., are very effective in self-healing micro-length Scale Damage, self-healing of structural Scale or macro-length Scale Damage remains one of the grand challenges facing the self-healing community. We believe that self-healing of structural Damage may need multiple steps, at least two steps: close then heal (CTH), similar to the biological healing of wounds in the skin. In a previous study [1] , it has been proven that the confined shape recovery functionality of a shape memory polymer (SMP) based syntactic foam can be utilized to repair structural Damage such as impact Damage repeatedly, efficiently, and almost autonomously. The purpose of this study is to investigate the effect of various design parameters on the closing efficiencies of both the pure SMP and the SMP based syntactic foam. A systematic test program is implemented, including glass transition temperature (Tg) determination by dynamic mechanical analysis (DMA), isothermal compressive constitutive behavior at various temperatures, and stress-controlled uniaxial compression programming and shape recovery. During thermomechanical cycle testing, two stress levels are utilized for programming and three confinement conditions (fully confined, partially confined, and free) are investigated for shape recovery. It is found that the programming stress is restored under confined recovery conditions, which helps in fully closing the crack; the foam shifts the Tg higher and increases the stiffness at temperatures above the Tg; higher programming stresses lead to slightly higher shape fixity but lower shape recovery in free recovery cases; a higher programming stress also results in a higher peak stress for confined recovery conditions; while the peak stress recovered is controlled by thermal stress, the final stress recovered is controlled by the programming stress, which is stored and recovered using an entropic mechanism. This study lays a solid foundation for using shape memory polymer based composites to self-repair macro-length Scale Damage.
Damon Nettles - One of the best experts on this subject based on the ideXlab platform.
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thermomechanical characterization of a shape memory polymer based self repairing syntactic foam
Polymer, 2010Co-Authors: Guoqiang Li, Damon NettlesAbstract:Abstract While the current self-healing approaches such as micro-capsules, hollow fibers, thermally reversible covalent bonds, ionomers, incorporation of thermoplastic particles, etc., are very effective in self-healing micro-length Scale Damage, self-healing of structural Scale or macro-length Scale Damage remains one of the grand challenges facing the self-healing community. We believe that self-healing of structural Damage may need multiple steps, at least two steps: close then heal (CTH), similar to the biological healing of wounds in the skin. In a previous study [1] , it has been proven that the confined shape recovery functionality of a shape memory polymer (SMP) based syntactic foam can be utilized to repair structural Damage such as impact Damage repeatedly, efficiently, and almost autonomously. The purpose of this study is to investigate the effect of various design parameters on the closing efficiencies of both the pure SMP and the SMP based syntactic foam. A systematic test program is implemented, including glass transition temperature (Tg) determination by dynamic mechanical analysis (DMA), isothermal compressive constitutive behavior at various temperatures, and stress-controlled uniaxial compression programming and shape recovery. During thermomechanical cycle testing, two stress levels are utilized for programming and three confinement conditions (fully confined, partially confined, and free) are investigated for shape recovery. It is found that the programming stress is restored under confined recovery conditions, which helps in fully closing the crack; the foam shifts the Tg higher and increases the stiffness at temperatures above the Tg; higher programming stresses lead to slightly higher shape fixity but lower shape recovery in free recovery cases; a higher programming stress also results in a higher peak stress for confined recovery conditions; while the peak stress recovered is controlled by thermal stress, the final stress recovered is controlled by the programming stress, which is stored and recovered using an entropic mechanism. This study lays a solid foundation for using shape memory polymer based composites to self-repair macro-length Scale Damage.
Wolfgang Grill - One of the best experts on this subject based on the ideXlab platform.
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Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation
International Journal of Solids and Structures, 2011Co-Authors: Amit Shelke, Sunanda Banerjee, Tribikram Kundu, Umar Amjad, Wolfgang GrillAbstract:Abstract In recent years early detection of structural Damage (detecting incubation of Damage) has received great attention in the structural health monitoring field. However, extraction of lower Scale information to quantify the degree of Damage is a challenging task, especially when the detection is based on macro-Scale acoustic wave signals. All materials exhibit dependence on the intrinsic length Scale. An attempt is made in this paper to extract lower Scale feature from the macro-Scale wave signal using nonlocal elasticity theory. The Christoffel solution has been modified using nonlocal parameters. The dispersion curves are generated for anisotropic solids using perturbation parameter through nonlocal theory. Dispersion curves are sensitive to initiation of Damage in anisotropic solids at the intrinsic-length Scale. In this paper detection of initiation of Damage in a 4 mm carbon composite plate is demonstrated by employing nonlocal perturbation parameter and formulating a new Nonlocal Damage Index (NDI). The nonlocal theory is used to demonstrate the early prediction of failure of the system and to show progressive evolution of the Damage.
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Erratum: Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation (International Journal of Solids and Structures (2011) 48 (1219-1228))
International Journal of Solids and Structures, 2011Co-Authors: Amit Shelke, Sunanda Banerjee, Tribikram Kundu, Umar Amjad, Wolfgang GrillAbstract:Corrigendum to ‘‘Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation’’ [Int. J. Solids Struct. 48 (2011) 1219–1228] Amit Shelke a,⇑, Sourav Banerjee , Tribikram Kundu , Umar Amjad , W. Grill b Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, United States b Institute of Experimental Physics II, University of Leipzig, Germany
Bin Sun - One of the best experts on this subject based on the ideXlab platform.
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A numerical method for improving seismic resistance of concrete based on its meso-Scale Damage mechanisms
International Journal of Computational Materials Science and Engineering, 2019Co-Authors: Bin SunAbstract:In this study, reliable image-based meso-Scale Damage evolution simulation of concrete can be executed by considering its heterogeneous meso-components. Meso-Scale Damage evolution of concrete with different meso-components are simulated and analyzed here, which can be used to optimize seismic resistance of concrete. As a case study, seismic Damage process of a reinforced concrete (RC) column with different meso-component parameters are simulated. From the simulation results, it can be seen that improvement of the properties of interfacial transition zone (ITZ) can significantly improve the seismic performance of RC columns. The established reliable Damage evolution simulation of concrete can supply a useful numerical tool to study the method for improving seismic performance of RC column such as optimizing concrete’s meso-model parameters.
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A numerical method for improving seismic resistance of concrete based on its meso-Scale Damage mechanisms
International Journal of Computational Materials Science and Engineering, 2019Co-Authors: Bin SunAbstract:In this study, reliable image-based meso-Scale Damage evolution simulation of concrete can be executed by considering its heterogeneous meso-components. Meso-Scale Damage evolution of concrete with...
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Adaptive concurrent multi-Scale FEM for trans-Scale Damage evolution in heterogeneous concrete
Computational Materials Science, 2015Co-Authors: Bin SunAbstract:Abstract This paper presents a new adaptive concurrent multi-Scale FEM (ACMFEM) to simulate the trans-Scale failure processes from material Damage in meso-Scale to local failure area in macro-Scale and eventually to global failure for concrete structures. The method can carry out automatically trans-Scale coupling analysis on the failure process without user intervention. As cases studies of the method, the trans-Scale failure processes of a L-shaped concrete component subjected to gradually increasing displacement loading and reinforced concrete (RC) column under seismic loading are simulated by using the developed method. The results show that, the developed method can be used to reveal the trans-Scale failure mechanism of concrete structures by considering the process from material Damage in meso-Scale to local failure area in macro-Scale and eventually to global failure in structural Scale; and it is reliable in simulation on evolving Damage and failure in concrete structures with the adaptive capability as well as better computational efficiency.
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a multi Scale Damage model for fatigue accumulation due to short cracks nucleation and growth
Engineering Fracture Mechanics, 2014Co-Authors: Bin SunAbstract:Abstract A multi-Scale fatigue Damage evolution model is proposed for describing both the behaviour of short fatigue cracks nucleation and growth in micro-Scale and fatigue Damage evolution reflecting the progressive deterioration process of metal components and structures in macro-Scale. The model is verified through the experimental data of fatigue Damage. It was found that, the model can offer a new reasonable explanation of the effect of load sequence on fatigue life, and also can predict the fatigue life during fatigue Damage accumulation due to short cracks nucleation and growth in metal components and structures.
Sunanda Banerjee - One of the best experts on this subject based on the ideXlab platform.
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Precursor/incubation of multi-Scale Damage state quantification in composite materials: using hybrid microcontinuum field theory and high-frequency ultrasonics
IEEE transactions on ultrasonics ferroelectrics and frequency control, 2013Co-Authors: Sunanda Banerjee, Riaz AhmedAbstract:A systematic framework for incubation of Damage- state quantification in composites is almost absent in the current practice. Identification and quantification of the material state at its early stage has become significantly important in the field of structural health monitoring. Interaction between the intrinsic material state and ultrasonic wave signals, e.g., nonlinear ultrasonic, higher harmonic generation, etc., in metals are quite well known and well documented in the literature. However, it is extremely challenging to quantify the precursor to Damage state in composite materials. Thus, in this paper, a comparatively simple but efficient novel approach is proposed to quantify the "incubation of Damage" state using scanning acoustic microscopy. The proposed approach exploits the hybrid microcontinuum field theory to quantify the intrinsic (multi-Scale) Damage state. Defying the conventional route of bottom-up multi-Scale modeling methods, a hybrid top-down approach is presented, which is then correlated to the ultrasonic signature obtained from the materials. A parameter to quantify incubation of Damage at meso-Scale has been identified in this paper. The intrinsic length-Scale-dependent parameter called "Damage entropy" closely resembles the material state resulting from fatigue, extreme environments, operational hazards or spatio-temporal variability, etc. The proposed quantification process involves a fusion between micromorphic physics and high-frequency ultrasonics in an unconventional way. The proposed approach is validated through an experimental study conducted on glass-fiber reinforced polymer composites which are mechanically fatigued. Specimens were characterized under a scanning acoustic microscope at 50 and 100 MHz. The imaging data and the sensor signals are characterized to quantify the incubation of Damage state by the new parameter Damage entropy.
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Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation
International Journal of Solids and Structures, 2011Co-Authors: Amit Shelke, Sunanda Banerjee, Tribikram Kundu, Umar Amjad, Wolfgang GrillAbstract:Abstract In recent years early detection of structural Damage (detecting incubation of Damage) has received great attention in the structural health monitoring field. However, extraction of lower Scale information to quantify the degree of Damage is a challenging task, especially when the detection is based on macro-Scale acoustic wave signals. All materials exhibit dependence on the intrinsic length Scale. An attempt is made in this paper to extract lower Scale feature from the macro-Scale wave signal using nonlocal elasticity theory. The Christoffel solution has been modified using nonlocal parameters. The dispersion curves are generated for anisotropic solids using perturbation parameter through nonlocal theory. Dispersion curves are sensitive to initiation of Damage in anisotropic solids at the intrinsic-length Scale. In this paper detection of initiation of Damage in a 4 mm carbon composite plate is demonstrated by employing nonlocal perturbation parameter and formulating a new Nonlocal Damage Index (NDI). The nonlocal theory is used to demonstrate the early prediction of failure of the system and to show progressive evolution of the Damage.
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Erratum: Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation (International Journal of Solids and Structures (2011) 48 (1219-1228))
International Journal of Solids and Structures, 2011Co-Authors: Amit Shelke, Sunanda Banerjee, Tribikram Kundu, Umar Amjad, Wolfgang GrillAbstract:Corrigendum to ‘‘Multi-Scale Damage state estimation in composites using nonlocal elastic kernel: An experimental validation’’ [Int. J. Solids Struct. 48 (2011) 1219–1228] Amit Shelke a,⇑, Sourav Banerjee , Tribikram Kundu , Umar Amjad , W. Grill b Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, United States b Institute of Experimental Physics II, University of Leipzig, Germany
