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Guoqiang Li - One of the best experts on this subject based on the ideXlab platform.
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a self healing Particulate Composite reinforced with strain hardened short shape memory polymer fibers
Polymer, 2013Co-Authors: Guoqiang Li, Pengfei ZhangAbstract:Abstract A Particulate Composite dispersed with thermoplastic particles and strain hardened short shape memory polymer fibers was prepared to evaluate its ability to repeatedly heal wide-opened cracks per the two-step close-then-heal (CTH) self-healing scheme. A two-step coating approach was used to enhance the shape fixity and workability of the cold-drawn programmed short polyurethane fibers. The relationship between recovery-stress and recovery-strain was experimentally determined by partially constrained shape recovery test. Notched beam specimens were prepared and fracture-healing was conducted up to five cycles. It is found that the Composite was able to heal the wide-opened crack repeatedly with considerable healing efficiency. It is also found that the healing efficiency increases as the fiber length increases, but in a reduced increasing rate. The recovery stress-recovery strain of the strain hardened shape memory polymer fiber behaves nonlinearly. The coated fiber is more effective than the uncoated fiber in closing wide-opened cracks when the recovery strain is within a certain range.
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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.
C. T. Liu - One of the best experts on this subject based on the ideXlab platform.
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8th ASCE Specialty Conference on Probabilistic Mechanics and Structural Reliability PMC2000-297 DETERMINATION OF EQUIVALENT INITIAL FLAW SIZE IN A Particulate Composite MATERIAL
2015Co-Authors: C. T. Liu, J. N. YangAbstract:In this study, a method for determining the initial flaw size in a Particulate Composite material is developed. The results of analyses indicate that the initial flaw size and the critical flaw size follow the second asymptotic distribution of maximum value. It also indicates that on the first approximation, it can be assumed that the initial flaw size and the critical flaw size are independent of specimen thickness
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Multi-Scale Strain Measurements of a Particulate Composite Material
Recent Advances in Solids and Structures, 2002Co-Authors: C. T. Liu, C. W. Smith, G. RavichandranAbstract:In this study, the strain fields on two different length scales in a Particulate Composite material containing hard particles embedded in a rubbery matrix were investigated, using two different techniques. The experimental results were analyzed and are discussed.Copyright © 2002 by ASME
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Investigating the Constraint Effect in a Particulate Composite Material
Computational Weld Mechanics Constraint and Weld Fracture, 2002Co-Authors: C. T. LiuAbstract:In this study, the effect of constraint on the critical Mode I stress intensity factor for the onset of crack growth was investigated in a Particulate Composite material, containing hard particles in a rubbery matrix. Uniaxial specimens with different specimen thicknesses and initial crack lengths were tested under a constant strain rate of 8 cm/cm/min at room temperature. The tested data was analyzed and the results are discussed.Copyright © 2002 by ASME
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The Effects of Pressure on Fracture of a Rubbery Particulate Composite
2000Co-Authors: T. C. Miller, C. T. LiuAbstract:Abstract : Rubbery Particulate Composites used in aerospace consist of a rubbery matrix with a large volume of embedded particles. Cracks may form in these Composites and cause catastrophic failure of the component. If we can better predict their fracture, expensive components with questionable cracks may be usable. Research on fracture of these Composites has been ongoing but has been inhibited by their unique behavior. The large deformations and the material inhomogeneity make using conventional experimental techniques and related analytical methods difficult, and matrix viscoelasticity requires careful consideration of strain rates and temperatures. Most experimental research on the fracture of rubbery Particulate Composites has been under ambient pressure conditions IA, although the effect of pressure is important since service conditions involve high pressure during critical portions of the component life. This work studies the pressure effect on a Particulate Composite. We tested the Composite for fracture properties in a pressure chamber, and investigated the initiation of crack growth and the growth rate.
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Determination of Equivalent Initial Flaw Size in a Particulate Composite Material
2000Co-Authors: C. T. Liu, J. N. YangAbstract:Abstract : In this study, a method for determining the initial flaw size in a Particulate Composite material is developed. The results of analyses indicate that the initial flaw length and the critical flaw size follow the second asymptotic distribution of maximum value. It also indicates that on the first approximation, it can be assumed that the initial flaw size and the critical flaw size is independent of specimen thickness.
Stefan Barta - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity and limiting oxygen index of basic rubber blend/aluminium hydroxide Particulate Composite
Plastics Rubber and Composites, 1999Co-Authors: Stefan Barta, J Bielek, Peter DieškaAbstract:Measurements of the effective thermal conductivity and the limiting oxygen index of a basic rubber blend/aluminium hydroxide Particulate Composite have been presented and interpreted in the frame of the percolation theory. The experimental data of the thermal conductivity were fitted by the equation for effective thermal conductivity and from this fitting, the threshold percolation was obtained. From the fitting of the experimental data of the limiting oxygen index, the interval in which the threshold percolation lies was obtained. It was shown that the threshold percolation obtained from measurement of the effective thermal conductivity also lies in that interval.
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thermal conductivity and limiting oxygen index of basic rubber blend aluminium hydroxide Particulate Composite
Plastics Rubber and Composites, 1999Co-Authors: Stefan Barta, J Bielek, Peter DieškaAbstract:Measurements of the effective thermal conductivity and the limiting oxygen index of a basic rubber blend/aluminium hydroxide Particulate Composite have been presented and interpreted in the frame of the percolation theory. The experimental data of the thermal conductivity were fitted by the equation for effective thermal conductivity and from this fitting, the threshold percolation was obtained. From the fitting of the experimental data of the limiting oxygen index, the interval in which the threshold percolation lies was obtained. It was shown that the threshold percolation obtained from measurement of the effective thermal conductivity also lies in that interval.
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Study of thermophysical and mechanical properties of Particulate Composite polyethylene‐CaCO3
Journal of Applied Polymer Science, 1997Co-Authors: Stefan Barta, J Bielek, Peter DieškaAbstract:Starting from the formulae for effective parameters of the Particulate Composite derived within the average field approximation, the formula for the percolation threshold is derived. The maximum value of the percolation threshold is 1/3 in the case of the isotropic granules of globular shape. Further, the experimental data obtained from the measurement of effective thermal conductivity and elastic shear modulus of the Particulate Composite polyethylene-CaCO 3 cannot be interpreted in the framework of the average field approximation. For this reason it was necessary to modify the formulae for effective parameters, and they were able to describe the experiment.
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Effective Young’s modulus and Poisson’s ratio for the Particulate Composite
Journal of Applied Physics, 1994Co-Authors: Stefan BartaAbstract:Relations for effective Young’s modulus and for effective Poisson’s ratio of the multicomponent Particulate Composite in the framework of the average field approximation are derived. In the case of a binary system, the existence of the percolation phase transition is shown and relations for effective parameters of a percolating system are analyzed in detail.
Tanguy Rouxel - One of the best experts on this subject based on the ideXlab platform.
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Evidence and modeling of mechanoluminescence in a transparent glass Particulate Composite
Applied Physics Letters, 2015Co-Authors: Marion Dubernet, Yann Gueguen, Patrick Houizot, Fabrice Célarié, Jean-christophe Sangleboeuf, Hervé Orain, Tanguy RouxelAbstract:Mechanoluminescence (ML) of a transparent alkali-phosphate glass Composite with SrAl2O4:Eu, Dy particles is reported. Uniaxial compression experiments show the linear dependence of the mechanoluminescence intensity with the mechanical power. A theoretical model, based on the physics of delayed processes (in analogy of viscoelasticity), is proposed. This model accurately predicts the ML intensity changes induced by a complex mechanical loading and provides a convincing description of the mechanoluminescence response.
Pengfei Zhang - One of the best experts on this subject based on the ideXlab platform.
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a self healing Particulate Composite reinforced with strain hardened short shape memory polymer fibers
Polymer, 2013Co-Authors: Guoqiang Li, Pengfei ZhangAbstract:Abstract A Particulate Composite dispersed with thermoplastic particles and strain hardened short shape memory polymer fibers was prepared to evaluate its ability to repeatedly heal wide-opened cracks per the two-step close-then-heal (CTH) self-healing scheme. A two-step coating approach was used to enhance the shape fixity and workability of the cold-drawn programmed short polyurethane fibers. The relationship between recovery-stress and recovery-strain was experimentally determined by partially constrained shape recovery test. Notched beam specimens were prepared and fracture-healing was conducted up to five cycles. It is found that the Composite was able to heal the wide-opened crack repeatedly with considerable healing efficiency. It is also found that the healing efficiency increases as the fiber length increases, but in a reduced increasing rate. The recovery stress-recovery strain of the strain hardened shape memory polymer fiber behaves nonlinearly. The coated fiber is more effective than the uncoated fiber in closing wide-opened cracks when the recovery strain is within a certain range.