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Yoshiharu Tsujita - One of the best experts on this subject based on the ideXlab platform.

  • temperature dependence of the mean size of polyphenyleneoxide Microvoids as studied by xe sorption and 129xe nmr chemical shift analyses
    Polymer Journal, 2012
    Co-Authors: Hiroaki Yoshimizu, Satoshi Ohta, Tomoko Asano, Tomoyuki Suzuki, Yoshiharu Tsujita
    Abstract:

    129Xe NMR spectra of 129Xe in polyphenyleneoxide, PPO were measured at various temperatures below Tg. From the analysis of 129Xe NMR chemical shifts, the mean volume of individual Microvoids in PPO, v could be determined. The temperature when value of v becomes same as a Xe atom, was very close to Tg of PPO. Temperature dependence of individual microvoid’s volume was very similar with that of CH′, which is obtained by dual-mode sorption model from Xe sorption isotherms and is corresponding to the unrelaxed volume of PPO in the glassy state.

  • characterization of the Microvoids of a tetramethyl polycarbonate polystyrene blend system using xe sorption measurements and 129xe nmr spectroscopy
    Polymer Journal, 2012
    Co-Authors: Hiroaki Yoshimizu, Tomoyuki Suzuki, Takafumi Murakami, Yoshiharu Tsujita
    Abstract:

    Xe sorption properties of tetramethyl bisphenol A polycarbonate (TMPC)/polystyrene (PS) blends indicated the reduction of Microvoids by blending. From the analysis of 129Xe NMR chemical shifts of the 129Xe in these blends, the mean volume of individual Microvoids (v) was calculated. The v values for these blends were smaller than those of predicted by a simple additive rule, as well as the cases of variation of density and Xe sorption properties. This fact indicates that the volume contraction induced by blending for TMPC/PS blends is mainly attributed to contraction volume of individual Microvoids.

  • characterization of Microvoids in ppo ps polymer blend by means of 129xe nmr spectroscopy
    Desalination, 2002
    Co-Authors: Tomoyuki Suzuki, Hiroaki Yoshimizu, Yoshiharu Tsujita
    Abstract:

    Abstract Relationships among 129 Xe NMR chemical shift, Xe sorption properties, and density have been investigated for poly(2,6-dimethyl-1,4-phenylene oxide) / polystyrene miscible blend system in order to evaluate the variation of Microvoids by blending. Xe sorption isotherms of all samples have been explained successfully on the basis of the dual-mode sorption model. Xe sorption properties and densities of blended samples have indicated the reduction of Microvoids by blending. 129 Xe NMR chemical shifts of 129 Xe sorbed in each sample have shown a non-linear low-field shift with increasing total amount of Xe sorption. Estimation of the Microvoids by 129 Xe NMR spectroscopy has been consistent with the results of density and Xe sorption measurements.

  • solubility and permeability of quenched poly 2 6 dimethyl phenyleneoxide with various Microvoids
    Journal of Membrane Science, 1991
    Co-Authors: Yoshiharu Tsujita, Hisao Hachisuka, Tohru Imai, Akira Takizawa, Takatoshi Kinoshita
    Abstract:

    Solubility and permeability of poly(2,6-dimethyl phenyleneoxide) (PPO) membranes glassifled under various quenching conditions were examined with respect to the occurrence of Microvoids in order to clarify the mechanism and enhancement of permeation of glassy polymer membranes. Various PPO membranes were prepared by quenching from various holding temperatures above its glass transition temperature to a temperature in the glassy state, e.g. 0°C. The CO2 sorption in quenched PPO membranes increased with the increase of the holding temperature and was greater than that in slowly cooled PPO membranes. Sorption behavior of quenched PPO membranes was analysed by dual mode sorption model. The increase in sorption was interpreted in terms of increasing microvoid content; in other words Langmuir sorption capacity term caused by the quenching. The permeability of quenched PPO membranes was also enhanced by the increase in size of the Microvoids. The permeability increased with an increase of the holding temperature and was greater than that of slowly cooled PPO membranes. The permeation mechanism is explained by a partial immobilization model.

Zhuping Huang - One of the best experts on this subject based on the ideXlab platform.

  • a constitutive theory of particulate reinforced viscoelastic materials with partially debonded Microvoids
    Computational Materials Science, 2008
    Co-Authors: Jian Kang Chen, Zhuping Huang, Min Yuan
    Abstract:

    Abstract In particulate-reinforced viscoelastic materials, the interfacial debonding between particles and matrix is usually a significant damage mechanism. In this paper, a new theoretical model of constitutive relation for particulate-reinforced viscoelastic materials is proposed. In the new constitutive model, both the reinforced effect of particles and weak effect due to microdamage evolution are taken into account. First, the deformation of a nucleated microvoid due to partially interfacial debonding between a particle and infinite viscoelastic matrix is analyzed in terms of Eshelby’s equivalent inclusion method. Secondly, the porosity of nucleated Microvoids is calculated based on the computation of density function of nucleation rate, in which, the size distribution of particles is assumed to be a logarithmic normal function, and the debonding probability of interface between particles and matrix is assumed to obey Weibull’s distribution. Thirdly, a new definition of average stress and average strain for nucleated Microvoids is proposed with considering the effect of nucleation time. Based on definition, a new constitutive model is suggested. This new model is consistent with experimental results. Finally, the effects of loading rate, interfacial adhesive energy, geometrical parameters of particles, and relaxation time on the constitutive relation are examined numerically. The simulation results indicate that the increase of loading rate, volume fraction of particles, and relaxation time of matrix not only reinforces the stiffness of composites, but also speeds up the evolution of microdamage. Such a competition mechanism should be taken into account when designing particulate-reinforced composites.

  • statistical evolution of Microvoids in particle filled polymers under plate impact
    Key Engineering Materials, 2006
    Co-Authors: Jian Kang Chen, Zhuping Huang
    Abstract:

    Statistical evolution of Microvoids in a particle-filled polymer under plate impact is theoretically studied. Based on the constitutive equations of the material recently obtained by the authors, the velocity of the propagation of one-dimensional strain wave caused by the plate impact is analyzed, and the evolution of the microdamage is calculated. It is shown that the microvoid evolution is influenced by several factors, such as particle size-dispersity, average radius of particles, and the adhesive energy of the interface. The numerical results show that there is a sensitive crest of the impact velocity for microvoid evolution. If the impact velocity reaches the critical value corresponding to the peak value of the crest, the Microvoids accumulation will increase rapidly, and it may lead to the dynamic failure of the material.

  • constitutive relation of particulate reinforced viscoelastic composite materials with debonded Microvoids
    Acta Materialia, 2003
    Co-Authors: Jun Chen, Zhuping Huang
    Abstract:

    Abstract In this paper, the constitutive relation of particulate-reinforced viscoelastic composite materials is studied by considering the evolution of Microvoids. Owing to the difference in mechanical properties between matrix and second phase particles, debonding of particle-matrix interface may occur under the condition of high stress triaxiality. This kind of damage will lead to the nucleation and growth of Microvoids. The reinforcing effect due to rigid particles and the weakening effect due to Microvoids caused by debonding on the overall mechanical properties of particulate-reinforced composites are investigated. Using the energy criterion of interfacial debonding, an expression for the nucleation rate of Microvoids is suggested. Then, the growth of these voids is studied by means of Eshelby’s equivalent inclusion method. It is shown that the strain of the Microvoids depends not only on the remote strain history but also on their nucleation time. By considering the effect of nucleation time, a new definition of an average strain of Microvoids is given. According to the Mori–Tanaka scheme, a macroscopic constitutive relation of the composite material is finally derived. The results show that macroscopic strain rate, particle-size dispersity, relaxation time of matrix, and interface adhesive strength all play key roles in the overall mechanical properties of particulate-reinforced composites.

  • a statistical model of Microvoids evolution in rate sensitive ductile materials solution for high stress triaxiality cases
    International Journal of Damage Mechanics, 1999
    Co-Authors: H L Li, Zhuping Huang
    Abstract:

    Statistical behavior ofthe Microvoids' evolution process in ductile materials is investigated in this article with the emphasis on the discussion about the effect of strain rate-sensitivity of the matrix material. The viscoplastic constitutive relation of the matrix material is assumed to have the overstress form proposed by Perzyna. In the case of high stress triaxiality, the nucleation rate and the growth rate of Microvoids are discussed. Then, based on the balance law of Microvoids' number density, differential equations governing the evolution of Microvoids are obtained and solved with the help of the two kinetic equations describing the nucleation rate and the void growth rate. Thus, the size distribution functions of Microvoids are found from the theoretical analysis, and the effect of strain rate-sensitivity of the matrix on the evolution of Microvoids is examined. The present theoretical prediction provides a reasonable explanation of the experimental phenomena observed by previous researchers.

  • a constitutive model of a particle reinforced viscoelastic composite material with debonded Microvoids
    1999
    Co-Authors: Zhuping Huang, Jian Kang Chen, Huiling Li
    Abstract:

    The statistical behavior of Microvoids’ evolution in a linear viscoelastic material which contains well bonded second phase particles is investigated. The particle size distribution is assumed to obey a logarithmic normal distribution. Because of the difference in mechanical properties between the matrix and the second phase particles, the debonding damage of particle-matrix interface may occur under the action of external loads. This kind of damage will lead to Microvoids’ nucleation and growth. In this paper, the reinforcing effect due to rigid particles and the weakening effect due to Microvoids produced from the debonding on the overall mechanical property of the particle reinforced composite material are studied. By virtue of Eshelby’s equivalent inclusion method and Mori-Tanaka theory, the average normal stress on the particle-matrix interface which governs the void nucleation and the dilational rate of void volume which governs the void growth are calculated. Then, based on the kinetic conditions for the Microvoids’ nucleation and growth as well as the balance law of voids’ number, the distribution functions of the number densities both for perfectly bonded particles and for Microvoids are obtained. Thus, a macroscopic constitutive relation of the considered composite material is derived. It is shown that the macroscopic strain rate,

Jun Chen - One of the best experts on this subject based on the ideXlab platform.

  • constitutive relation of particulate reinforced viscoelastic composite materials with debonded Microvoids
    Acta Materialia, 2003
    Co-Authors: Jun Chen, Zhuping Huang
    Abstract:

    Abstract In this paper, the constitutive relation of particulate-reinforced viscoelastic composite materials is studied by considering the evolution of Microvoids. Owing to the difference in mechanical properties between matrix and second phase particles, debonding of particle-matrix interface may occur under the condition of high stress triaxiality. This kind of damage will lead to the nucleation and growth of Microvoids. The reinforcing effect due to rigid particles and the weakening effect due to Microvoids caused by debonding on the overall mechanical properties of particulate-reinforced composites are investigated. Using the energy criterion of interfacial debonding, an expression for the nucleation rate of Microvoids is suggested. Then, the growth of these voids is studied by means of Eshelby’s equivalent inclusion method. It is shown that the strain of the Microvoids depends not only on the remote strain history but also on their nucleation time. By considering the effect of nucleation time, a new definition of an average strain of Microvoids is given. According to the Mori–Tanaka scheme, a macroscopic constitutive relation of the composite material is finally derived. The results show that macroscopic strain rate, particle-size dispersity, relaxation time of matrix, and interface adhesive strength all play key roles in the overall mechanical properties of particulate-reinforced composites.

Tomoyuki Suzuki - One of the best experts on this subject based on the ideXlab platform.

Hiroaki Yoshimizu - One of the best experts on this subject based on the ideXlab platform.