Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade compone...Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade components.In this paper,a dynamic model of 3D 4-directional braided composite thin plates considering braiding directions is established.Based on Kirchhoff's plate assumptions,the displacement variables of the plate are expressed.By incorporating the braiding directions into the constitutive equation of the braided composites,the dynamic model of the plate considering braiding directions is obtained.The effects of the speeds,braiding directions,and braided angles on the responses of the plate with fixed-axis rotation and translational motion,respectively,are investigated.This paper presents a dynamic theory for calculating the deformation of 3D braided composite structures undergoing both translational and rotational motions.It also provides a simulation method for investigating the dynamic behavior of non-isotropic material plates in various applications.展开更多
Three-dimensional(3D)braided composites have significant potential for use in engineering structural materials.However,conventional 3D braiding machines are insufficient for designing composites with complex geometrie...Three-dimensional(3D)braided composites have significant potential for use in engineering structural materials.However,conventional 3D braiding machines are insufficient for designing composites with complex geometries.This paper proposes a programmable design methodology for 3D rotary braiding machines using circle-cutting and combination strategies.By introducing varying numbers of incisions on the circle,a diverse range of horn gears can be designed.Different combinations of these cut-circles allow the horn gears to be assembled into various 3D rotary braiders.The parametric equation for the braider plate is derived,showing that a combination strategy involving two cut-circles is feasible for braider design,whereas integrating three cut-circles simultaneously is impossible for a single machine.The construction of an automatic 6-3 type 3D braiding machine demonstrates the effectiveness of the proposed design strategy.This flexible braider design approach provides a practical solution for producing 3D braided composites with complex geometries.展开更多
This paper aims to experimentally and numerically probe fatigue behaviours and lifetimes of 3D4D(three-dimensional four-directional)braided composite I-beam under four-point flexure spectrum loading.New fatigue damage...This paper aims to experimentally and numerically probe fatigue behaviours and lifetimes of 3D4D(three-dimensional four-directional)braided composite I-beam under four-point flexure spectrum loading.New fatigue damage models of fibre yarn,matrix and fibre–matrix interface are proposed,and fatigue failure criteria and PFDA(Progressive Fatigue Damage Algorithm)are thus presented for meso-scale fatigue damage modelling of 3D4D braided composite I-beam.To validate the aforementioned model and algorithm,fatigue tests are conducted on the 3D4D braided composite I-beam under four-point flexure spectrum loading,and fatigue failure mechanisms are analyzed and discussed.Novel global–local FE(Finite Element)model based on the PFDA is generated for modelling progressive fatigue failure process and predicting fatigue life of 3D4D braided composite I-beam under four-point flexure spectrum loading.Good agreement has been achieved between experimental results and predictions,demonstrating the effective usage of new model.It is shown that matrix cracking and interfacial debonding initially initiates on top surface of top flange of I-beam,and then gradually propagates from the side surface of top flange to the intermediate web along the braiding angle,and considerable fiber breakage finally causes final fatigue failure of I-beam.展开更多
Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sed...Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sedimentary architecture is highly complex.In this paper,a flume experiment was conducted to reveal the detailed depositional process and establish a fine sedimentary architecture model for sandy braided rivers.The result showed that(1)Three types of braid channels,including the lateral migration channel,the confluence channel,and the deep incised channel,were recognized based on geometry,scale,distribution,and spatial patterns;they are interconnected,forming a complex channel network.(2)Braid channels were characterized by lateral migration,abandonment,filling,and chute cutoff.Lateral migration of channels shaped the braid bars and dominated the formation,growth,and reworking of braid bars.(3)Controlled by the fast and frequent variations of the braid channel network,braid bars were continuously formed,reworked,reshaped,and composited of multiple accretions with different types,orientations,scales,and preservation degrees.Symmetrical and asymmetrical braid bars pre-sented significantly different composition patterns.(4)Dominated by the continuous reworking of braid channels,temporary deposits were limited preserved,braid channel deposits account for 54.3 percent of the eventually preserved braided river deposits,and four types of amalgamate patterns were recognized.Braid bars were cut and limited preserved,only accounting for 45.7 percent of the eventually preserved braided river deposits.(5)During the experiment,only 28 percent of near-surface temporary deposits were eventually preserved in fragmented forms with the final experimental braided river;the shape,spatial patterns,and most of the deposits observed during the depositional process were largely reworked and poorly preserved.(6)The scale of eventually preserved braid bars and braid channels is significantly smaller than the temporary deposits from geomorphic observations.The aspect ratio of the eventually preserved braid bars and the width-to-depth ratio of the eventually preserved braid channel are also significantly different from that of the temporary ones measured from topography data.展开更多
In order to solve the problem of oily wastewater,the poly(m-phenyleneisophthalamide)(PMIA)braided tube reinforced(PBR)poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)(PFA)hollow fiber membrane with thermal and...In order to solve the problem of oily wastewater,the poly(m-phenyleneisophthalamide)(PMIA)braided tube reinforced(PBR)poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)(PFA)hollow fiber membrane with thermal and solvent resistant property was prepared via no-solvent green method.The membrane surface and pore structure was optimized by changing the sintering temperature and graphene(GE)content.The morphologies showed that the spherical surface with good lipophilicity was formed,and the excellent mechanical strength with a favorable interface bonding state could be obtained due to the PFA melts permeating into the supporting layer.The doping of GE produced synergistic effects with the sintering temperature owing to its good thermal conductivity and pore formation.The PBR-PFA/GE hollow fiber membrane exhibited good hydrophobicity and lipophilicity with more than 97%separation efficiency for different oil products at-0.02 MPa.With the addition of GE,the average pore size first increases and then decreases,and the porosity gradually decreases.In addition,the hollow fiber membrane showed high separation ability to the water-in-oil emulsion,and maintained a stable flux recovery rate after recycling,making it possible to apply in the field of oily wastewater treatment.展开更多
The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by b...The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.展开更多
Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled pre...Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.展开更多
Three-dimensional（3 D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3D braided composite...Three-dimensional（3 D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3D braided composites are analyzed, and the possible approach of improving the properties of the materials is presented, that is, a new type of 3D full 5-directional braided composites is developed. The methods of making this type of preform are proposed. It is pointed out that the four-step braiding which is the most possible to realize industrialized production almost has no effect on the composites＇ properties. By analyzing the simulation model,the advantages of the material compared with the 3D 4-directional and 5-directional materials are presented. Finally, a microstructural model is analyzed to lay the foundation for the future theoretical analysis of these composites.展开更多
BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, g...BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, greatly influence nerve regeneration and functional recovery. OBJECTIVE： To observe the influence of conduit parameters and coating methods on torsion properties in an in vitro-degradation environment and at normal temperature. DESIGN, TIME AND SE＇I-FING： An in vitro, comparative study using repeated measures was performed at the College of Textiles, Donghua University, China from January 2005 to December 2007. MATERIALS： PGLA fiber and yarn （Shanghai Bio-TianQing, China）, as well as torsion property testing instrument （LaiZhou Electronic Instrument, China）, were used in the present study. METHODS： A total of 16 types of conduits were constructed according to braiding structures （regular/triaxial）, angles （50°/55°/60°/65°）nd coating methods （coated/uncoated）. At normal temperature, torsion properties of all conduits were tested at a predefined constant angle of 90°. Coated and uncoated conduits, which were triaxial and 65°, were incubated in a 5% CO2 incubator at 37 ℃ to simulate an in vitro degradation environment, and then torsion properties were tested at 4, 7, 11, 14, 17, 21,24, and 28 days in culture. MAIN OUTCOME MEASURES： Maximal torsion strength and torsion strength-torsion angle curve of conduits at normal temperature, as well as torsion strength-torsion angle curve, loss of torsion strength, and change in maximal torsion strength in an in vitro degradation environment. RESULTS： At normal temperature, the torsion properties of the triaxial structure were superior to the regular structure. Coated conduits performed better than uncoated ones, and the larger braiding angles exhibited superior torsion properties （P 〈 0.05）. In the in vitro degradation environment, with degradation time, torsion strength of uncoated conduits was deceased gradually and the loss of torsion strength was increased fast. Torsion strength of coated conduits was increased first and decreased afterwards; the loss of torsion strength was decreased slowly till 14 days; both became identical after 14 days （P 〉 0.05）. CONCLUSION： Torsion properties of coated conduits with a triaxial structure and large braiding angle were superior to uncoated conduits with regular structures and small braiding angles.展开更多
Let （C, C） be a braided monoidal category. The relationship between the braided Lie algebra and the left Jacobi braided Lie algebra in the category （C, C） is investigated. First, a braided C2-commutative algebra i...Let （C, C） be a braided monoidal category. The relationship between the braided Lie algebra and the left Jacobi braided Lie algebra in the category （C, C） is investigated. First, a braided C2-commutative algebra in the category （C, C） is defined and three equations on the braiding in the category （C, C） are proved. Secondly, it is verified that （A, [, ] ） is a left （strict） Jacobi braided Lie algebra if and only if （A, [, ] ） is a braided Lie algebra, where A is an associative algebra in the category （C, C）. Finally, as an application, the structures of braided Lie algebras are given in the category of Yetter-Drinfel＇d modules and the category of Hopf bimodules.展开更多
The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. ...The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. The creep curve appears as expected, and can be defined two phases, namely, the primary phase and the secondary phase. For each sample, strain increases with time rapidly, and then the strain rate decreases and appears to approach a constant rate of change (steady-state creep). The experiment results show that the creep resistant properties are improved while the braiding angle decreases or the fiber volume fraction increases, and that the five-directional braiding structure offers better creep resistant properties than the four-directional braiding structure.展开更多
D braiding technology has stimulated a great deal of interest in the world at large and been widely used in aerospace, military, civil construction and medical fields. Although 3 D braided composites have many good f...D braiding technology has stimulated a great deal of interest in the world at large and been widely used in aerospace, military, civil construction and medical fields. Although 3 D braided composites have many good features, their features are very complicated. Optic fiber sensors can be multi braided into 3 D braided composites to fulfill a new kind of 3 D smart composites to monitor RTM process, study mechanical behaviors and damage states after molding, and monitor its own condition during service life. Since optic performances of optic fibers have direct and important relation to the performances of optic fiber sensors, experimental research is done to devise a method to incorporate the optic fiber into a 3 D structure. The optical performances of the braided optic fibers are tested and compared with the original one to study the optic performances of optic fibers, before their being braided into composites and after the RTM process.展开更多
The positions of braiding carrier in track and column braiding are represented by a diagrammatic braiding plan and a corresponding lattice-array is defined. A set is then formed so that the permutation analysis can be...The positions of braiding carrier in track and column braiding are represented by a diagrammatic braiding plan and a corresponding lattice-array is defined. A set is then formed so that the permutation analysis can be performed to represent the movement of carriers in a braiding process. The process of 4-step braiding is analyzed as an example to describe the application of the proposed method by expressing a braiding cycle as a product of disjoint cycles. As a result, a mapping relation between the disjoint cycles and the movement of carriers is deduced. Following the same analysis principles, a process of 8-step braiding and the corresponding initial state of the lattice-array is developed. A successful permutation analysis to the process manifests the general suitability of the proposed method.展开更多
This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the spa...This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the space spiral curve, a three-dimensional parametrical geometrical model is constructed. The finite element model is built by using the beam-beam contact elements and 3D beam elements. The constituent nitinol wires are assumed to be linear elastic material. The finite element analysis figures out that the radial stiffness of the stent and the stress distribution of the wires are influenced by all the structural parameters. The helix pitch of the wires is the most important factor. Under the condition of the same load and other structural parameters remaining unchanged, when the number of wires is 24, the stress of the wire crosssection is at the minimum. A comparison between the vitro experimental results and the analytical results is conducted, and the data is consistent, which proves that the current finite element model can be used to appropriately predict the mechanical performance of the braided esophageal stents.展开更多
As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the b...As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.展开更多
The question of how the category of entwined modules can be made into a braided monoidal category is studied. First, the sufficient and necessary conditions making the category into a monoidal category are obtained by...The question of how the category of entwined modules can be made into a braided monoidal category is studied. First, the sufficient and necessary conditions making the category into a monoidal category are obtained by using the fact that if （A, C, ψ） is an entwining structure, then A × C can be made into an entwined module. The conditions are that the algebra and coalgebra in question are both bialgebras with some extra compatibility relations. Then given a monodial category of entwined modules, the braiding is constructed by means of a twisted convolution invertible map Q, and the conditions making the category form into a braided monoidal category are obtained similarly. Finally, the construction is applied to the category of Doi-Hopf modules and （α, β ）-Yetter-Drinfeld modules as examples.展开更多
The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its ...The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.展开更多
This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship betw...This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship between the braid structure and braiding parameters. Based on microscopic observations, we divide a three-dimensional braid structure into three representative regions, i.e., the interior, surface and corner, and treat the three regions, respectively. Three types of microstructural unit-cell models are then established. The surface characteristics and the relationship between the interior and surface unit-cells have been derived. Good agreement has been obtained between the calculated and measured values of fiber volume fraction of the braided composite samples.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12372071 and 12372070)the Aeronautical Science Fund of China(No.2022Z055052001)the Foundation of China Scholarship Council(No.202306830079)。
文摘Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade components.In this paper,a dynamic model of 3D 4-directional braided composite thin plates considering braiding directions is established.Based on Kirchhoff's plate assumptions,the displacement variables of the plate are expressed.By incorporating the braiding directions into the constitutive equation of the braided composites,the dynamic model of the plate considering braiding directions is obtained.The effects of the speeds,braiding directions,and braided angles on the responses of the plate with fixed-axis rotation and translational motion,respectively,are investigated.This paper presents a dynamic theory for calculating the deformation of 3D braided composite structures undergoing both translational and rotational motions.It also provides a simulation method for investigating the dynamic behavior of non-isotropic material plates in various applications.
基金funded by the Shanghai Natural Science Foundation of Shanghai Municipal Science and Technology Commission(20ZR1400600)the Fundamental Research Funds for the Central Universities(2232023G-06)through collaborative research with the Advanced Fibrous Materials Lab(AFML)at the University of British Columbia.
文摘Three-dimensional(3D)braided composites have significant potential for use in engineering structural materials.However,conventional 3D braiding machines are insufficient for designing composites with complex geometries.This paper proposes a programmable design methodology for 3D rotary braiding machines using circle-cutting and combination strategies.By introducing varying numbers of incisions on the circle,a diverse range of horn gears can be designed.Different combinations of these cut-circles allow the horn gears to be assembled into various 3D rotary braiders.The parametric equation for the braider plate is derived,showing that a combination strategy involving two cut-circles is feasible for braider design,whereas integrating three cut-circles simultaneously is impossible for a single machine.The construction of an automatic 6-3 type 3D braiding machine demonstrates the effectiveness of the proposed design strategy.This flexible braider design approach provides a practical solution for producing 3D braided composites with complex geometries.
基金supported by the National Natural Science Foundation of China(No.12472340).
文摘This paper aims to experimentally and numerically probe fatigue behaviours and lifetimes of 3D4D(three-dimensional four-directional)braided composite I-beam under four-point flexure spectrum loading.New fatigue damage models of fibre yarn,matrix and fibre–matrix interface are proposed,and fatigue failure criteria and PFDA(Progressive Fatigue Damage Algorithm)are thus presented for meso-scale fatigue damage modelling of 3D4D braided composite I-beam.To validate the aforementioned model and algorithm,fatigue tests are conducted on the 3D4D braided composite I-beam under four-point flexure spectrum loading,and fatigue failure mechanisms are analyzed and discussed.Novel global–local FE(Finite Element)model based on the PFDA is generated for modelling progressive fatigue failure process and predicting fatigue life of 3D4D braided composite I-beam under four-point flexure spectrum loading.Good agreement has been achieved between experimental results and predictions,demonstrating the effective usage of new model.It is shown that matrix cracking and interfacial debonding initially initiates on top surface of top flange of I-beam,and then gradually propagates from the side surface of top flange to the intermediate web along the braiding angle,and considerable fiber breakage finally causes final fatigue failure of I-beam.
基金funded by two projects of the National Natural Science Foundation of China(No.41802123,42130813).
文摘Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sedimentary architecture is highly complex.In this paper,a flume experiment was conducted to reveal the detailed depositional process and establish a fine sedimentary architecture model for sandy braided rivers.The result showed that(1)Three types of braid channels,including the lateral migration channel,the confluence channel,and the deep incised channel,were recognized based on geometry,scale,distribution,and spatial patterns;they are interconnected,forming a complex channel network.(2)Braid channels were characterized by lateral migration,abandonment,filling,and chute cutoff.Lateral migration of channels shaped the braid bars and dominated the formation,growth,and reworking of braid bars.(3)Controlled by the fast and frequent variations of the braid channel network,braid bars were continuously formed,reworked,reshaped,and composited of multiple accretions with different types,orientations,scales,and preservation degrees.Symmetrical and asymmetrical braid bars pre-sented significantly different composition patterns.(4)Dominated by the continuous reworking of braid channels,temporary deposits were limited preserved,braid channel deposits account for 54.3 percent of the eventually preserved braided river deposits,and four types of amalgamate patterns were recognized.Braid bars were cut and limited preserved,only accounting for 45.7 percent of the eventually preserved braided river deposits.(5)During the experiment,only 28 percent of near-surface temporary deposits were eventually preserved in fragmented forms with the final experimental braided river;the shape,spatial patterns,and most of the deposits observed during the depositional process were largely reworked and poorly preserved.(6)The scale of eventually preserved braid bars and braid channels is significantly smaller than the temporary deposits from geomorphic observations.The aspect ratio of the eventually preserved braid bars and the width-to-depth ratio of the eventually preserved braid channel are also significantly different from that of the temporary ones measured from topography data.
基金funding provided by the National Natural Science Foundation of China(52103035,52173038).
文摘In order to solve the problem of oily wastewater,the poly(m-phenyleneisophthalamide)(PMIA)braided tube reinforced(PBR)poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)(PFA)hollow fiber membrane with thermal and solvent resistant property was prepared via no-solvent green method.The membrane surface and pore structure was optimized by changing the sintering temperature and graphene(GE)content.The morphologies showed that the spherical surface with good lipophilicity was formed,and the excellent mechanical strength with a favorable interface bonding state could be obtained due to the PFA melts permeating into the supporting layer.The doping of GE produced synergistic effects with the sintering temperature owing to its good thermal conductivity and pore formation.The PBR-PFA/GE hollow fiber membrane exhibited good hydrophobicity and lipophilicity with more than 97%separation efficiency for different oil products at-0.02 MPa.With the addition of GE,the average pore size first increases and then decreases,and the porosity gradually decreases.In addition,the hollow fiber membrane showed high separation ability to the water-in-oil emulsion,and maintained a stable flux recovery rate after recycling,making it possible to apply in the field of oily wastewater treatment.
基金National Natural Science Foundation of China(No.52273054)Shanghai Natural Science Foundation,China(No.20ZR1402200)。
文摘The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.
基金Supported by Jiangsu Provincial Frontier Leading Technology Basic Research Project(Grant No.BK20212007)Aero-Engine and Gas Turbine Basic Science Center(Grant No.P2022-B-IV-014-001)+1 种基金China Postdoctoral Program Fund(Grant No.1005/YBA23044)China Postdoctoral Assistance Fund(Grant No.1005/YBA23031)。
文摘Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.
文摘Three-dimensional（3 D）braided composites are a kind of advanced ones and are used in the aeronautical and astronautical fields more widely. The advantages, usages, shortages and disadvantages of 3D braided composites are analyzed, and the possible approach of improving the properties of the materials is presented, that is, a new type of 3D full 5-directional braided composites is developed. The methods of making this type of preform are proposed. It is pointed out that the four-step braiding which is the most possible to realize industrialized production almost has no effect on the composites＇ properties. By analyzing the simulation model,the advantages of the material compared with the 3D 4-directional and 5-directional materials are presented. Finally, a microstructural model is analyzed to lay the foundation for the future theoretical analysis of these composites.
文摘BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, greatly influence nerve regeneration and functional recovery. OBJECTIVE： To observe the influence of conduit parameters and coating methods on torsion properties in an in vitro-degradation environment and at normal temperature. DESIGN, TIME AND SE＇I-FING： An in vitro, comparative study using repeated measures was performed at the College of Textiles, Donghua University, China from January 2005 to December 2007. MATERIALS： PGLA fiber and yarn （Shanghai Bio-TianQing, China）, as well as torsion property testing instrument （LaiZhou Electronic Instrument, China）, were used in the present study. METHODS： A total of 16 types of conduits were constructed according to braiding structures （regular/triaxial）, angles （50°/55°/60°/65°）nd coating methods （coated/uncoated）. At normal temperature, torsion properties of all conduits were tested at a predefined constant angle of 90°. Coated and uncoated conduits, which were triaxial and 65°, were incubated in a 5% CO2 incubator at 37 ℃ to simulate an in vitro degradation environment, and then torsion properties were tested at 4, 7, 11, 14, 17, 21,24, and 28 days in culture. MAIN OUTCOME MEASURES： Maximal torsion strength and torsion strength-torsion angle curve of conduits at normal temperature, as well as torsion strength-torsion angle curve, loss of torsion strength, and change in maximal torsion strength in an in vitro degradation environment. RESULTS： At normal temperature, the torsion properties of the triaxial structure were superior to the regular structure. Coated conduits performed better than uncoated ones, and the larger braiding angles exhibited superior torsion properties （P 〈 0.05）. In the in vitro degradation environment, with degradation time, torsion strength of uncoated conduits was deceased gradually and the loss of torsion strength was increased fast. Torsion strength of coated conduits was increased first and decreased afterwards; the loss of torsion strength was decreased slowly till 14 days; both became identical after 14 days （P 〉 0.05）. CONCLUSION： Torsion properties of coated conduits with a triaxial structure and large braiding angle were superior to uncoated conduits with regular structures and small braiding angles.
基金The National Natural Science Foundation of China(No.10871042)
文摘Let （C, C） be a braided monoidal category. The relationship between the braided Lie algebra and the left Jacobi braided Lie algebra in the category （C, C） is investigated. First, a braided C2-commutative algebra in the category （C, C） is defined and three equations on the braiding in the category （C, C） are proved. Secondly, it is verified that （A, [, ] ） is a left （strict） Jacobi braided Lie algebra if and only if （A, [, ] ） is a braided Lie algebra, where A is an associative algebra in the category （C, C）. Finally, as an application, the structures of braided Lie algebras are given in the category of Yetter-Drinfel＇d modules and the category of Hopf bimodules.
文摘The long-term creep behavior of polymer-matrix 3-D braided composites was studied by using the tensile creep test method, and the effect of braiding structure, braiding angle and fiber volume fraction were discussed. The creep curve appears as expected, and can be defined two phases, namely, the primary phase and the secondary phase. For each sample, strain increases with time rapidly, and then the strain rate decreases and appears to approach a constant rate of change (steady-state creep). The experiment results show that the creep resistant properties are improved while the braiding angle decreases or the fiber volume fraction increases, and that the five-directional braiding structure offers better creep resistant properties than the four-directional braiding structure.
文摘D braiding technology has stimulated a great deal of interest in the world at large and been widely used in aerospace, military, civil construction and medical fields. Although 3 D braided composites have many good features, their features are very complicated. Optic fiber sensors can be multi braided into 3 D braided composites to fulfill a new kind of 3 D smart composites to monitor RTM process, study mechanical behaviors and damage states after molding, and monitor its own condition during service life. Since optic performances of optic fibers have direct and important relation to the performances of optic fiber sensors, experimental research is done to devise a method to incorporate the optic fiber into a 3 D structure. The optical performances of the braided optic fibers are tested and compared with the original one to study the optic performances of optic fibers, before their being braided into composites and after the RTM process.
文摘The positions of braiding carrier in track and column braiding are represented by a diagrammatic braiding plan and a corresponding lattice-array is defined. A set is then formed so that the permutation analysis can be performed to represent the movement of carriers in a braiding process. The process of 4-step braiding is analyzed as an example to describe the application of the proposed method by expressing a braiding cycle as a product of disjoint cycles. As a result, a mapping relation between the disjoint cycles and the movement of carriers is deduced. Following the same analysis principles, a process of 8-step braiding and the corresponding initial state of the lattice-array is developed. A successful permutation analysis to the process manifests the general suitability of the proposed method.
基金The National Natural Science Foundation of China(No.51005124)the Opening Foundation of Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments(No.JS-NB-2009-1-1)
文摘This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the space spiral curve, a three-dimensional parametrical geometrical model is constructed. The finite element model is built by using the beam-beam contact elements and 3D beam elements. The constituent nitinol wires are assumed to be linear elastic material. The finite element analysis figures out that the radial stiffness of the stent and the stress distribution of the wires are influenced by all the structural parameters. The helix pitch of the wires is the most important factor. Under the condition of the same load and other structural parameters remaining unchanged, when the number of wires is 24, the stress of the wire crosssection is at the minimum. A comparison between the vitro experimental results and the analytical results is conducted, and the data is consistent, which proves that the current finite element model can be used to appropriately predict the mechanical performance of the braided esophageal stents.
文摘As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.
基金Specialized Research Fund for the Doctoral Program of Higher Education(No.20060286006)the National Natural Science Founda-tion of China(No.10571026)
文摘The question of how the category of entwined modules can be made into a braided monoidal category is studied. First, the sufficient and necessary conditions making the category into a monoidal category are obtained by using the fact that if （A, C, ψ） is an entwining structure, then A × C can be made into an entwined module. The conditions are that the algebra and coalgebra in question are both bialgebras with some extra compatibility relations. Then given a monodial category of entwined modules, the braiding is constructed by means of a twisted convolution invertible map Q, and the conditions making the category form into a braided monoidal category are obtained similarly. Finally, the construction is applied to the category of Doi-Hopf modules and （α, β ）-Yetter-Drinfeld modules as examples.
基金Supported by the National High Technology Research and Development Program of China(2012AA112201)
文摘The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.
文摘This paper describes a study of three-dimensional braids produced by a four-step 1 × 1 method. An analytical approach is employed in conjunction with experimental investigations to establish the relationship between the braid structure and braiding parameters. Based on microscopic observations, we divide a three-dimensional braid structure into three representative regions, i.e., the interior, surface and corner, and treat the three regions, respectively. Three types of microstructural unit-cell models are then established. The surface characteristics and the relationship between the interior and surface unit-cells have been derived. Good agreement has been obtained between the calculated and measured values of fiber volume fraction of the braided composite samples.
