The longitude tensile properties of 3-Dimension-4-directional（3D-4d） braided C/Si C composites（CMCs） were investigated with the help of a double scale model. This model involves micro-scale and unit-cell scale. In...The longitude tensile properties of 3-Dimension-4-directional（3D-4d） braided C/Si C composites（CMCs） were investigated with the help of a double scale model. This model involves micro-scale and unit-cell scale. In micro-scale, the tensile properties of fiber tows which involves matrix cracking, interfacial debonding, and fiber failure are studied. The unit-cell scale model can reflect the braided structure and simulate the tensile properties of 3D-4d CMCs by introducing the tensile properties of fiber tows into it. Quasi-static tensile tests of 3D-4d braided CMCs were performed on a PWS-100 test system. The predicted tensile stressstrain curve by the double scale model is in good agreement with that of the experimental results.展开更多
Double-scale model for three-dimension-4 directional（3D-4d） braided C/SiC composites has been proposed to investigate its elastic properties. The double-scale model involves micro-scale that takes fiber/ matrix/poro...Double-scale model for three-dimension-4 directional（3D-4d） braided C/SiC composites has been proposed to investigate its elastic properties. The double-scale model involves micro-scale that takes fiber/ matrix/porosity in fibers tows into consideration with unit cell which considers the 3D-4d braiding structure. Micro-optical photographs of composites have been taken to study the braided structure. Then a parameterized finite element model that reflects the structure of 3D-4d braided composites is proposed. Double-scale elastic modulus prediction model is developed to predict the elastic properties of 3D-4d braided C/SiC composites. Stiffness and eompliance-averaging method and energy method are adopted to predict the elastic properties of composites. Static-tension experiments have been conducted to investigate the elastic modulus of 3D-4d braided C/SiC composites. Finally, the effect of micro-porosity in fibers tows on the elastic modulus of 3D-4d braided C/SiC composites has been studied. According to the conclusion of this thesis, elastic modulus predicted by energy method and stiffness-averaging method both find good agreement with the experimental values, when taking the micro-porosity in fibers tows into consideration. Differences between the theoretical and experimental values become smaller.展开更多
Four samples were chosen by systematic sampling from the range-finders between 1987 and 2003 to test the range-finders’ representativeness of the scoring criteria of CET-4 compositions. The samples were analyzed from...Four samples were chosen by systematic sampling from the range-finders between 1987 and 2003 to test the range-finders’ representativeness of the scoring criteria of CET-4 compositions. The samples were analyzed from the perspectives of transitivity, modality, thematic structure and cohesion. Fisher's Exact Test from the SAS system was used to compare two-sidedly the correct rate and the constituent ratio of these functional usages between two neighboring levels. Statistical results indicate that it is the quality, not the quantity of these functional usages that distinguishes two neighboring levels. The range-finders can basically represent the abstract scoring criteria as far as the four functional systems are concerned. However, the validity of CET-4 writing needs to be improved.展开更多
Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews...Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews the research status of the mechanical models for SMPs,shape-memory nanocomposites and shape-memory polymer composites(SMPCs);it also introduces some spatially deployable structures,such as hinges,beams,and antennae based on SMPCs.In addition,the deformation types of 4D printing structures and the potential applications of this technology in robots and medical devices are also summarized.展开更多
Aluminum 6061 matrix composite reinforced by 35 wt% B4 C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static（0.001 s-1） and dynamic（760-1150 s-1） compress...Aluminum 6061 matrix composite reinforced by 35 wt% B4 C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static（0.001 s-1） and dynamic（760-1150 s-1） compression experiments. The Johnson-Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4 C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4 C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson-Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.展开更多
In this work,we firstly synthesized a CeO_(2)/C_(3)N_(4) photocatalyst with Z-scheme heterojunction by a facile LiC-KCI molten salt method.The synthesized catalyst has an excellent quality for removing organic polluti...In this work,we firstly synthesized a CeO_(2)/C_(3)N_(4) photocatalyst with Z-scheme heterojunction by a facile LiC-KCI molten salt method.The synthesized catalyst has an excellent quality for removing organic pollution of dyes and antibiotics in wastewater.As an example,the CeCN-1:5 prepared with a mass ratio of Ce_(2)(CO_(3))_(3)·xH_(2)O:C_(3)H_(3)N_(6)=1:5 exhibits a methylene blue(MB)removal capacity of 100%within 90 min and tetracycline(TC)removal capacity of 94.6%.After 4 cycles,the CeCN-1:5 keeps a removal efficiency of nearly 100%in 150 min for MB and 85.7%for TC.The kinetics study reveals that the MB removal process with the CeCN-1:5 fits the modified Elovich model with strong adsorption while TC removal fits the first-order model.The large surface area(238 m^(2)/g)and negative zeta potential(-39.3 mV)of CeCN-1:5 contribute to superior adsorption capacity to MB.However,the adsorption of TC is restricted due to the positive surface/pore potential in acidic solution.CeCN-1:5has combined Z-scheme heterojunction and exhibits a low recombination rate of electrons(e^(-))/holes(h^(+))and the photo-generated active radicals of·OH/·O_(2)^(-)that promotes the photocatalytic performance.This novel CeO_(2)/C_(3)N_(4) photocatalyst with an excellent photocatalysis removal activity has an enormous potential for photocatalytic applications.展开更多
基金Funded by the National Basic Research Program of Chinathe National Natural Science Foundation of China(51675266)+3 种基金the Aeronautical Science Foundation of China(2014ZB52024)the Fundamental Research Funds for the Central Universities(NJ20160038)the Jiangsu Innovation Program for Graduate Education(CXLX13_165)the Fundamental Research Funds for the Central Universities
文摘The longitude tensile properties of 3-Dimension-4-directional（3D-4d） braided C/Si C composites（CMCs） were investigated with the help of a double scale model. This model involves micro-scale and unit-cell scale. In micro-scale, the tensile properties of fiber tows which involves matrix cracking, interfacial debonding, and fiber failure are studied. The unit-cell scale model can reflect the braided structure and simulate the tensile properties of 3D-4d CMCs by introducing the tensile properties of fiber tows into it. Quasi-static tensile tests of 3D-4d braided CMCs were performed on a PWS-100 test system. The predicted tensile stressstrain curve by the double scale model is in good agreement with that of the experimental results.
基金Funded by the National Basic Research Program of China,National Natural Science Foundation of China(No.51075204)Funding of Jiangsu Innovation Program for Graduate Education(No.CXLX13_165)+2 种基金the Fundamental Research Funds for the Central Universities,Aeronautical Science Foundation of China(No.2012ZB52026)Research Fund for the Doctoral Program of Higher Education of China(No.20070287039)NUAA Research Funding(No.NZ2012106)
文摘Double-scale model for three-dimension-4 directional（3D-4d） braided C/SiC composites has been proposed to investigate its elastic properties. The double-scale model involves micro-scale that takes fiber/ matrix/porosity in fibers tows into consideration with unit cell which considers the 3D-4d braiding structure. Micro-optical photographs of composites have been taken to study the braided structure. Then a parameterized finite element model that reflects the structure of 3D-4d braided composites is proposed. Double-scale elastic modulus prediction model is developed to predict the elastic properties of 3D-4d braided C/SiC composites. Stiffness and eompliance-averaging method and energy method are adopted to predict the elastic properties of composites. Static-tension experiments have been conducted to investigate the elastic modulus of 3D-4d braided C/SiC composites. Finally, the effect of micro-porosity in fibers tows on the elastic modulus of 3D-4d braided C/SiC composites has been studied. According to the conclusion of this thesis, elastic modulus predicted by energy method and stiffness-averaging method both find good agreement with the experimental values, when taking the micro-porosity in fibers tows into consideration. Differences between the theoretical and experimental values become smaller.
基金This paper is one of the outcomes of the university project ( XB200349)
文摘Four samples were chosen by systematic sampling from the range-finders between 1987 and 2003 to test the range-finders’ representativeness of the scoring criteria of CET-4 compositions. The samples were analyzed from the perspectives of transitivity, modality, thematic structure and cohesion. Fisher's Exact Test from the SAS system was used to compare two-sidedly the correct rate and the constituent ratio of these functional usages between two neighboring levels. Statistical results indicate that it is the quality, not the quantity of these functional usages that distinguishes two neighboring levels. The range-finders can basically represent the abstract scoring criteria as far as the four functional systems are concerned. However, the validity of CET-4 writing needs to be improved.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.11772109,11632005 and 11672086)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.11421091).
文摘Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews the research status of the mechanical models for SMPs,shape-memory nanocomposites and shape-memory polymer composites(SMPCs);it also introduces some spatially deployable structures,such as hinges,beams,and antennae based on SMPCs.In addition,the deformation types of 4D printing structures and the potential applications of this technology in robots and medical devices are also summarized.
基金financially supported by the Key Science and Technology Program of Shanxi Province,China(No.20130321024)the Graduate Innovation Project of Shanxi Province,China(No.B2014005)
文摘Aluminum 6061 matrix composite reinforced by 35 wt% B4 C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static（0.001 s-1） and dynamic（760-1150 s-1） compression experiments. The Johnson-Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4 C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4 C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson-Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.
基金supported by National Natural Science Foundation of China(52164025,51804088,U1812402)Basic Research Program from Science&Technology Department of Guizhou Province([2020]1Y219,[2019]1082)。
文摘In this work,we firstly synthesized a CeO_(2)/C_(3)N_(4) photocatalyst with Z-scheme heterojunction by a facile LiC-KCI molten salt method.The synthesized catalyst has an excellent quality for removing organic pollution of dyes and antibiotics in wastewater.As an example,the CeCN-1:5 prepared with a mass ratio of Ce_(2)(CO_(3))_(3)·xH_(2)O:C_(3)H_(3)N_(6)=1:5 exhibits a methylene blue(MB)removal capacity of 100%within 90 min and tetracycline(TC)removal capacity of 94.6%.After 4 cycles,the CeCN-1:5 keeps a removal efficiency of nearly 100%in 150 min for MB and 85.7%for TC.The kinetics study reveals that the MB removal process with the CeCN-1:5 fits the modified Elovich model with strong adsorption while TC removal fits the first-order model.The large surface area(238 m^(2)/g)and negative zeta potential(-39.3 mV)of CeCN-1:5 contribute to superior adsorption capacity to MB.However,the adsorption of TC is restricted due to the positive surface/pore potential in acidic solution.CeCN-1:5has combined Z-scheme heterojunction and exhibits a low recombination rate of electrons(e^(-))/holes(h^(+))and the photo-generated active radicals of·OH/·O_(2)^(-)that promotes the photocatalytic performance.This novel CeO_(2)/C_(3)N_(4) photocatalyst with an excellent photocatalysis removal activity has an enormous potential for photocatalytic applications.
