The relations of bulk modulus, shear modulus, Young's modulus and the Poisson's ratio with porosity of foam plastics are determined by a three phase spheroidal model commonly used in Composite Mechanics. The r...The relations of bulk modulus, shear modulus, Young's modulus and the Poisson's ratio with porosity of foam plastics are determined by a three phase spheroidal model commonly used in Composite Mechanics. The results are compared with those using differential scheme. It is shown that the material properties derived from the present model normally are larger than those obtained by differential scheme for foam plastics with identical porosity. The differences in shear moduli and Young's moduli obtained by the two methods are small but they are larger for bulk moduli of incompressible matrix and Poisson's ratios. The Young's moduli of high density foam plastics derived by the present model agree better with experimental ones.展开更多
Novel microcellular foams using thin plasticized PC sheet were prepared by compression molding. The measurement results showed that T of plasticized PC was decreased and the molecular chain mobility was increased. Dec...Novel microcellular foams using thin plasticized PC sheet were prepared by compression molding. The measurement results showed that T of plasticized PC was decreased and the molecular chain mobility was increased. Decrease in T and increase in chains mobility were contributed to the widen of foaming temperature window. Effects of processing conditions on cell size, cell density and relative density were also investigated. The experimental results show that the temperature, tributyl citrate and foaming agent content have more effects on the structures and morphology of the plasticized PC microcellular foam. Effects of experimental conditions on cell size distribution have also been discussed.展开更多
Water-blown polyurethane rigid foams are getting more and more attention,because the traditional blowing agent HCFC141b has already been abolished to prevent the ozone layer from destruction.However,the polyurethane r...Water-blown polyurethane rigid foams are getting more and more attention,because the traditional blowing agent HCFC141b has already been abolished to prevent the ozone layer from destruction.However,the polyurethane rigid foams blown by water have serious defects,i.e.friability and resulting lower adhesion strength.Thus,the purpose of this study is to resolve the problems by chemical plastication.The maleate was added to polyol-premix containing water or to polyisocyanate,with both of which maleate does not react.To prove the reaction when polyol-premix and polyisocyanate were mixed,the model composite was synthesized and analyzed by IR,NMR and ESI(MS).Furthermore,a series of water-blown polyurethane rigid foams added different amount maleate were successfully prepared.By testing impact strength and adhesion strength of the foams,the actual effect of adding maleate was obtained.展开更多
The compressive mechanical properties of syntactic foams reinforced by hollow plastic beads were studied by the quasi-static compression test. The failure mechanism of syntactic foams was also investigated by macrosco...The compressive mechanical properties of syntactic foams reinforced by hollow plastic beads were studied by the quasi-static compression test. The failure mechanism of syntactic foams was also investigated by macroscopic and microscopic observation on the fractured specimens. The experimental results show that the density of syntactic foams is still the key factor affecting their mechanical properties. The macroscopic and microscopic observation on the fractured specimens indicates that the main failure mode is the elastic-plastic collapse caused by shear.展开更多
为了将新型泡沫混凝土动态弹塑性损伤模型应用到防护结构中,首先开展组合式防护结构预制孔装药爆炸试验;随后利用新泡沫混凝土材料模型对试验进行数值模拟验证,并将新模型的模拟结果与LS-DYNA中Soil and Foam模型的模拟结果进行对比;最...为了将新型泡沫混凝土动态弹塑性损伤模型应用到防护结构中,首先开展组合式防护结构预制孔装药爆炸试验;随后利用新泡沫混凝土材料模型对试验进行数值模拟验证,并将新模型的模拟结果与LS-DYNA中Soil and Foam模型的模拟结果进行对比;最后,基于验证的数值模型,开展以梯度泡沫混凝土作为分配层的组合式防护结构预制孔装药爆炸的数值模拟,探讨梯度泡沫混凝土层界面层数和排列方式对组合式防护结构抗爆性能的影响。结果表明,新泡沫混凝土材料模型的模拟结果与试验结果吻合良好,与Soil and Foam模型相比,新模型在应力波传播和损伤破坏方面预测更好,泡沫混凝土层界面层数和排列方式对作用在主体结构上的应力以及分配层的损伤破坏情况有一定的影响。展开更多
To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants ...To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants and TEGDN(trimethyleneglycol dinitrate) propellants are measured by the gravimetric method,and SEM(scanning electron microscope) is used to observe the morphology of foamed propellants.The result shows that a large amount of CO_2 could be dissolved in NC-based propellants.The experimental results also reveal that the energetic plasticizer TEGDN exerts an important influence on the pore structure.The triaxial tensile failure mechanism for solid-state nucleation is used to explain the nucleation of NC-based propellants in the sol id state.Since some specific foaming behaviors of NC-based propellants can not be explained by the failure mechanism,a solid-state nucleation mechanism which revises the triaxial tensile failure mechanism is proposed and discussed.展开更多
The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive ...The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.展开更多
基金Supported by the National Natural Science Foundation of China and Laboratory for Nonlinear Mechanics of Continuous Media,Institute of Mechanics,Chinese Academy of Sciences.
文摘The relations of bulk modulus, shear modulus, Young's modulus and the Poisson's ratio with porosity of foam plastics are determined by a three phase spheroidal model commonly used in Composite Mechanics. The results are compared with those using differential scheme. It is shown that the material properties derived from the present model normally are larger than those obtained by differential scheme for foam plastics with identical porosity. The differences in shear moduli and Young's moduli obtained by the two methods are small but they are larger for bulk moduli of incompressible matrix and Poisson's ratios. The Young's moduli of high density foam plastics derived by the present model agree better with experimental ones.
基金Funded by the Natural Science Foundation of Hubei Provincial Science&Technologies Department(2010CDB04604)
文摘Novel microcellular foams using thin plasticized PC sheet were prepared by compression molding. The measurement results showed that T of plasticized PC was decreased and the molecular chain mobility was increased. Decrease in T and increase in chains mobility were contributed to the widen of foaming temperature window. Effects of processing conditions on cell size, cell density and relative density were also investigated. The experimental results show that the temperature, tributyl citrate and foaming agent content have more effects on the structures and morphology of the plasticized PC microcellular foam. Effects of experimental conditions on cell size distribution have also been discussed.
文摘Water-blown polyurethane rigid foams are getting more and more attention,because the traditional blowing agent HCFC141b has already been abolished to prevent the ozone layer from destruction.However,the polyurethane rigid foams blown by water have serious defects,i.e.friability and resulting lower adhesion strength.Thus,the purpose of this study is to resolve the problems by chemical plastication.The maleate was added to polyol-premix containing water or to polyisocyanate,with both of which maleate does not react.To prove the reaction when polyol-premix and polyisocyanate were mixed,the model composite was synthesized and analyzed by IR,NMR and ESI(MS).Furthermore,a series of water-blown polyurethane rigid foams added different amount maleate were successfully prepared.By testing impact strength and adhesion strength of the foams,the actual effect of adding maleate was obtained.
基金the National Natural Science Foundation of China(No. 50473013)
文摘The compressive mechanical properties of syntactic foams reinforced by hollow plastic beads were studied by the quasi-static compression test. The failure mechanism of syntactic foams was also investigated by macroscopic and microscopic observation on the fractured specimens. The experimental results show that the density of syntactic foams is still the key factor affecting their mechanical properties. The macroscopic and microscopic observation on the fractured specimens indicates that the main failure mode is the elastic-plastic collapse caused by shear.
文摘为了将新型泡沫混凝土动态弹塑性损伤模型应用到防护结构中,首先开展组合式防护结构预制孔装药爆炸试验;随后利用新泡沫混凝土材料模型对试验进行数值模拟验证,并将新模型的模拟结果与LS-DYNA中Soil and Foam模型的模拟结果进行对比;最后,基于验证的数值模型,开展以梯度泡沫混凝土作为分配层的组合式防护结构预制孔装药爆炸的数值模拟,探讨梯度泡沫混凝土层界面层数和排列方式对组合式防护结构抗爆性能的影响。结果表明,新泡沫混凝土材料模型的模拟结果与试验结果吻合良好,与Soil and Foam模型相比,新模型在应力波传播和损伤破坏方面预测更好,泡沫混凝土层界面层数和排列方式对作用在主体结构上的应力以及分配层的损伤破坏情况有一定的影响。
基金funded by the priority academic program development of Jiangsu Higher Education Institutions
文摘To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants and TEGDN(trimethyleneglycol dinitrate) propellants are measured by the gravimetric method,and SEM(scanning electron microscope) is used to observe the morphology of foamed propellants.The result shows that a large amount of CO_2 could be dissolved in NC-based propellants.The experimental results also reveal that the energetic plasticizer TEGDN exerts an important influence on the pore structure.The triaxial tensile failure mechanism for solid-state nucleation is used to explain the nucleation of NC-based propellants in the sol id state.Since some specific foaming behaviors of NC-based propellants can not be explained by the failure mechanism,a solid-state nucleation mechanism which revises the triaxial tensile failure mechanism is proposed and discussed.
文摘The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.
