Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based compos...Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.展开更多
We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After ...We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After compression deformation,allαstructures of titanium were compacted with the emergence of Widmanstatten structures.Coarsened coloniesαof titanium were elongated and waved along the original growth direction,resulting in anisotropy of grains.Pores and Ti/Al intermetallic compounds of aluminum are significantly decreased after hot compression.Meanwhile,a good bonding interface between titanium and aluminum is obtained after hot compression,and the element diffusion is more intense.In addition,the mechanical properties and fracture behaviors of Ti/Al composite material with different clad ratio that is defined as the ratio of the thickness of titanium to that of the Ti/Al composite material are investigated by uniaxial tensile test.The experimental results show that the ultimate tensile strength of Ti/Al composite material is between that of single deposited titanium and aluminum,while the elongation of Ti/Al composite material with low clad ratio is lower than that of single aluminum due to the metallurgical reaction.As the clad ratio increases,the two component layers are harder to separate during deformation,which is resulted from the decrease of the inward contraction stress of three-dimensional stress caused by necking of aluminum.This work may promote the engineering application of Ti/Al bimetallic structures.展开更多
This work focused on the search for biobased materials capable of being used in road techniques as soil inclusions, and on studying the influence of their incorporation on the characteristic parameters of pavement lay...This work focused on the search for biobased materials capable of being used in road techniques as soil inclusions, and on studying the influence of their incorporation on the characteristic parameters of pavement layers. To this end, pineapple, cyperus and imperata plant fibers, due to their endemic availability, were used as reinforcement on sourced materials, notably bar soil, lateritic gravel and silty sand. Complete identification and mechanical tests (Proctor and CBR) were carried out on materials in their natural state (soil) and on composite materials (soil + plant fibers) in the laboratory to determine their classification in road geotechnics, their compaction parameters and their mechanical behavior. Firstly, the various types of 2.5 cm long fibers were incorporated into the different types of soil at mass contents of 1% and 2%. This part of the study showed that the pineapple fiber composite incorporated into class A2 bar soil offered the best results, with a 38% gain in CBR index compared with the natural soil. Pineapple fibers incorporated at 1% in lateritic gravel raise the CBR value of the reinforced soil to 10% of the CBR value of the natural soil and to 7% for silty sand.展开更多
Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing perform...Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing performance,silver coated porous carbon(Ag@PC)is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork.Phase compositions,morphological structure,and microwave absorption capability of the Ag@PC has been explored.Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork,which accelerates graphitization process of the amorphous carbon.The Ag@PC composite without adding polyvinyl pyrrolidone(PVP)exhibits higher dielectric constant and better EM wave dissipating capability.This is because the larger particles of Ag give rise to higher electric conductivity.After combing with frequency selective surface(FSS),the EM wave absorbing performance is further improved and the frequency region below-10 d B is located in8.20-11.75 GHz,and the minimal reflection loss value is-22.5 dB.This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.展开更多
Composite materials exhibit advantages from the combination of multiple properties,which cannot be achieved by a monolithic material.At present,the use of composite materials in miniaturized scale is receiving much at...Composite materials exhibit advantages from the combination of multiple properties,which cannot be achieved by a monolithic material.At present,the use of composite materials in miniaturized scale is receiving much attention in the fields of medicine,electronics,aerospace,and microtooling.A common method for producing miniaturized composite parts is micromanufacturing.There has been,however,no comprehensive literature published that reviews,compares,and discusses the ongoing micromanufacturing methods for producing miniaturized composite components.This study identifies the major micromanufacturing methods used with composite materials,categorizes their subclasses,and highlights the latest developments,new trends,and effects of key factors on the productivity,quality,and cost of manufacturing composite materials.A comparative study is presented that shows the potential and versatility associated with producing composite materials along with possible future applications.This review will be helpful in promoting micromanufacturing technology for fabricating miniaturized products made of composite materials to meet the growing industrial demand.展开更多
The technology of Intelligent cure operation is set forth according to developing tedency of smart material and structure. Intelligent-system-based tool was developed in order to operate the autoclave cure of a fiber ...The technology of Intelligent cure operation is set forth according to developing tedency of smart material and structure. Intelligent-system-based tool was developed in order to operate the autoclave cure of a fiber reinforced thermosetting matrix composite laminate in an optimal manner.The objective function is comforts for minimizing the total cure time,uniforming the temperature distribution,controling exothermal and minimizing the process-induced residual stresses in the laminate.Data is analyzed on-line to determine the trends in real-time.The results from application of this overall strategy for the curing of composites are presented.展开更多
We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability.The new model is motivated by finding the two n...We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability.The new model is motivated by finding the two natural resonance peaks to be inconsistent with the combination of the domain wall resonance and the natural resonance.In the derivation of the model,two relationships are explored:the first one is the relationship between the number of magnetic domains and the permeability,and the second one is the relationship between the natural resonance and the domain wall resonance.This reveals that the ball milling causes the number of magnetic domains to increase and the maximum initial permeability to exist after 10 h of ball milling.An experiment is conducted to demonstrate the reliability of the proposed model.The experimental results are in good agreement with the theoretical calculations.This new model is of great significance for studying the mechanism and applications of the resonance loss for soft magnetic composite materials in high frequency fields.展开更多
new surface infiltrating composite technique has been developed to obtain metal and ceramic composite layer on the surface of metal by traditional casting method. It has been shown that with the new method, a composit...new surface infiltrating composite technique has been developed to obtain metal and ceramic composite layer on the surface of metal by traditional casting method. It has been shown that with the new method, a composite layer with a thickness of 2-5 mm can be obtained. The ceramic particulates distribute uniformly in the matrix. The composite layer is very favorable to wear resistance and thermal resistance展开更多
Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomis...Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous展开更多
The application of mechanical and chemical syntheses in an high-energy vibration mill of the FESTU makes easy the process of the introduction of reinforced powders in castle composite materials on the Al basis. The ob...The application of mechanical and chemical syntheses in an high-energy vibration mill of the FESTU makes easy the process of the introduction of reinforced powders in castle composite materials on the Al basis. The obtained reinforced phases of Al-Ti-C composition have high specific Surface due to peculiarities of explosive mechanical and chemical syntheses. It increases the uniformity of their distribution in a matrix melt during the mixing process and also increases properties of castle composite materials.展开更多
With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weigh...With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weight and increase the payload,composite material structures will be widely used. It is difficult to evaluate the strength and life of composite materials due to their complex mechanism and various phenomena in damage and failure.Meanwhile,the structures of composite materials used in spacecrafts will bear complex loads,including the coupling loads of tension,pressure,bending,shear,and torsion. Static loads,thermal loads,and vibration loads may occur at the same time,which asks for verification requirements to ensure the structure safety. Therefore,it is necessary to carry out a systematic multi-level experimental study. In this paper,the building block approach (BBA) is used to investigate the multilevel composite material structures for spacecrafts. The advanced measurement technology is adopted based on digital image correlation (DIC) and piezoelectric and optical fiber sensors to measure the composite material structure deformation. The virtual experiment technology is applied to provide sufficient and reliable data for the evaluation of the composite material structures of spacecrafts.展开更多
The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elasti...The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspondence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale(SOTS) computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calculating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement approximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.展开更多
In this study,the deformation and stress distribution of printed circuit board(PCB)with different thickness and composite materials under a shock loading were analyzed by the finite element analysis.The standard 8-lay...In this study,the deformation and stress distribution of printed circuit board(PCB)with different thickness and composite materials under a shock loading were analyzed by the finite element analysis.The standard 8-layer PCB subjected to a shock loading 1500 g was evaluated first.Moreover,the finite element models of the PCB with different thickness by stacking various number of layers were discussed.In addition to changing thickness,the core material of PCB was replaced from woven E-glass/epoxy to woven carbon fiber/epoxy for structural enhancement.The non-linear material property of copper foil was considered in the analysis.The results indicated that a thicker PCB has lower stress in the copper foil in PCBs under the shock loading.The stress difference between the thicker PCB(2.6 mm)and thinner PCB(0.6 mm)is around 5%.Using woven carbon fiber/epoxy as core material could lower the stress of copper foil around 6.6%under the shock loading 1500 g for the PCB with 0.6 mm thickness.On the other hand,the stress level is under the failure strength of PCBs with carbon fiber/epoxy core layers and thickness 2.6 mm when the peak acceleration changes from 1500 g to 5000 g.This study could provide a reference for the design and proper applications of the PCB with different thickness and composite materials.展开更多
The oil sorption capacity of composite materials made up of different polymeric fabrics (namely acrylic fabric (AF), polypropylene nonwoven (PP), and silk stocking (SS) as composite out-packing materials) and expanded...The oil sorption capacity of composite materials made up of different polymeric fabrics (namely acrylic fabric (AF), polypropylene nonwoven (PP), and silk stocking (SS) as composite out-packing materials) and expanded perlite (EP) was evaluated for oil removal from the water. The effects of sorbent dosage, desorption time, oil amount in the water, and contact time on composite materials sorption were investigated. The results showed that the optimum quantity of EP was between 0.5 g and 1.0 g for 25 cm2 polymeric fabrics bags. Oil removal efficiency for 6 L/m2 of oil amount in the water was 52%-72%, 44%-63%, and 37%-48% for AF, PP, and SS composite materials, respectively. Oil/water selectivity analysis of different composite materials showed that AF composite material had a very high degree of hydrophobicity and oil sorption capacity of approximately 10.17 g/g. Both oil sorption kinetics and equilibrium studies were carried out, and the equilibrium process of composite materials was described well by the Langmuir isotherm, and the oil sorption kinetics of composite materials showed good correlation coefficients for the pseudo-second order kinetic model. Intra-particle diffusion studies showed that oil sorption mechanism was controlled by the three processes, involving in external liquid membrane diffusion, surface sorption, and intra-particle diffusion.展开更多
BiOIO3 is a layered semiconductor photocatalyst,which has good chemical properties and has attracted wide attention from researchers because of its unique structure.However,pure BiOIO3 has defects such as insufficient...BiOIO3 is a layered semiconductor photocatalyst,which has good chemical properties and has attracted wide attention from researchers because of its unique structure.However,pure BiOIO3 has defects such as insufficient response to visible light and easy recombination of photogenerated electrons.Therefore,in recent years,scholars have tried to modify BiOIO3 to expand its light absorption range,reduce the recombination of photogenerated electron-hole pairs and reduce its limitations,thereby improving its visible light catalytic performance.Current researches focus on the improvement of the catalytic activity of photocatalytic materials from morphology control,precious metal deposition,ion doping and construction of heterojunctions.展开更多
Initially,the materials used in the process of bridge construction were mainly wood,stone,etc.,and gradually the concrete,steel and other types of special materials currently in-use were developed.With the current vig...Initially,the materials used in the process of bridge construction were mainly wood,stone,etc.,and gradually the concrete,steel and other types of special materials currently in-use were developed.With the current vigorous development of science,technology and social economy in China,the development of bridge projects has also been accelerated to a large extent.In recent years,China has not only studied on how to strengthen the performance of concrete,steel and other materials in bridge projects,but also the performance of the recently developed smart,nano-,fibrous and other types of materials.This paper focuses on the application strategy of carbon fiber composite materials in bridge reconstruction projects to serve as a reference.展开更多
Non-destructive testing of composites is an important issue in the modern aircraft industry.Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occ...Non-destructive testing of composites is an important issue in the modern aircraft industry.Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and operation.The continuum model for describing the damaged zone is presented.The slip theory relations used for a continuous distribution of slip planes are applied.At the initial stage,the isotropic background model is used.This model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous addition.In this regime,the govern system of equations becomes rigid.To overcome this difficulty,the explicit-implicit grid-characteristic scheme is proposed.The standard ultrasound diagnostic procedure of damaged composite materials is successfully simulated.Compared with the trivial free-surface fracture model,different reactions on the compression and stretch waves are registered.This approach provided an effective way for the simulation of complex dynamic behavior of damage zones.展开更多
The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies ...The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies of MnO_(2)@C materials can be controlled by controlling the dosages of WS-CTPs and KMnO4.Meanwhile,it is aware that MnO_(2)exists in the MnO_(2)@C materials in an amorphous state.Compared with MnO_(2),MnO_(2)@C materials output a remarkable improvement in electrochemical performance.For instance,MnO_(2)@C-0.3 shows the storage capacity at 965.7 mA h g^(−1)after 300 cycles at a current density of 0.1 A g^(−1).In addition,after 600 cycles at a current density of 1.0 A g^(−1),the storage capacity of MnO_(2)@C-0.3 still keeps 450.3 mA h g^(−1),indicating that MnO_(2)@C-0.3 owns tremendous cycle stability at a high current density.In view of the fact that the coal tar pitches possess great cost advantages,the strategy of using WS-CTPs as a carbon source to cover the metal oxides is a competitive way to expand the application of metal oxides in the fabrication of electrodes of LIBs.展开更多
In this paper,we generalize the direct method of lines for linear elasticity problems of composite materials in star-shaped domains and consider its application to inverse elasticity problems.We assume that the bounda...In this paper,we generalize the direct method of lines for linear elasticity problems of composite materials in star-shaped domains and consider its application to inverse elasticity problems.We assume that the boundary of the star-shaped domain can be described by an explicit C 1 parametric curve in the polar coordinate.We introduce the curvilinear coordinate,in which the irregular star-shaped domain is converted to a regular semi-infinite strip.The equations of linear elasticity are discretized with respect to the angular variable and we solve the resulting semidiscrete approximation analytically using a direct method.The eigenvalues of the semi-discrete approximation converge quickly to the true eigenvalues of the elliptic operator,which helps capture the singularities naturally.Moreover,an optimal error estimate of our method is given.For the inverse elasticity problems,we determine the Lam´e coefficients from measurement data by minimizing a regularized energy functional.We apply the direct method of lines as the forward solver in order to cope with the irregularity of the domain and possible singularities in the forward solutions.Several numerical examples are presented to show the effectiveness and accuracy of our method for both forward and inverse elasticity problems of composite materials.展开更多
基金Funded by the National Natural Science Foundation of China(No.51678254)。
文摘Gypsum was used as substrate,and silica gel was mixed into substrate at a certain mass ratio to prepare humidity-controlling composites;moreover,the moisture absorption and desorption properties of gypsum-based composites were compared with adding different silica gel particle size and proportion.The morphological characteristics,the isothermal equilibrium moisture content curve,moisture absorption and desorption rate,moisture absorption and desorption stability,and humidity-conditioning performance were tested and analyzed.The experimental results show that,compared with pure-gypsum,the surface structure of the gypsum-based composites is relatively loose,the quantity,density and aperture of the pores in the structure increase.The absorption and desorption capacity increase along with the increase of silica gel particle size and silica gel proportion.When 3 mm silica gel particle size is added with a mass ratio of 40%,the maximum equilibrium moisture content of humidity-controlling composites is 0.161 g/g at 98% relative humidity(RH),3.22 times that of pure-gypsum.The moisture absorption and desorption rates are increased,the equilibrium moisture absorption and desorption rates are 2.68 times and 1.61 times that of pure-gypsum at 58.5% RH,respectively.The gypsum-based composites have a good stability,which has better timely response to dynamic humidity changes and can effectively regulate indoor humidity under natural conditions.
基金Funded by the National Natural Science Foundation of China(No.51775068)。
文摘We focused on Ti/Al composite materials fabricated by wire and arc addictive manufacturing,and the microstructure and interface characteristics of them before and after hot compression deformation were compared.After compression deformation,allαstructures of titanium were compacted with the emergence of Widmanstatten structures.Coarsened coloniesαof titanium were elongated and waved along the original growth direction,resulting in anisotropy of grains.Pores and Ti/Al intermetallic compounds of aluminum are significantly decreased after hot compression.Meanwhile,a good bonding interface between titanium and aluminum is obtained after hot compression,and the element diffusion is more intense.In addition,the mechanical properties and fracture behaviors of Ti/Al composite material with different clad ratio that is defined as the ratio of the thickness of titanium to that of the Ti/Al composite material are investigated by uniaxial tensile test.The experimental results show that the ultimate tensile strength of Ti/Al composite material is between that of single deposited titanium and aluminum,while the elongation of Ti/Al composite material with low clad ratio is lower than that of single aluminum due to the metallurgical reaction.As the clad ratio increases,the two component layers are harder to separate during deformation,which is resulted from the decrease of the inward contraction stress of three-dimensional stress caused by necking of aluminum.This work may promote the engineering application of Ti/Al bimetallic structures.
文摘This work focused on the search for biobased materials capable of being used in road techniques as soil inclusions, and on studying the influence of their incorporation on the characteristic parameters of pavement layers. To this end, pineapple, cyperus and imperata plant fibers, due to their endemic availability, were used as reinforcement on sourced materials, notably bar soil, lateritic gravel and silty sand. Complete identification and mechanical tests (Proctor and CBR) were carried out on materials in their natural state (soil) and on composite materials (soil + plant fibers) in the laboratory to determine their classification in road geotechnics, their compaction parameters and their mechanical behavior. Firstly, the various types of 2.5 cm long fibers were incorporated into the different types of soil at mass contents of 1% and 2%. This part of the study showed that the pineapple fiber composite incorporated into class A2 bar soil offered the best results, with a 38% gain in CBR index compared with the natural soil. Pineapple fibers incorporated at 1% in lateritic gravel raise the CBR value of the reinforced soil to 10% of the CBR value of the natural soil and to 7% for silty sand.
基金supported by National Natural Science Foundation of China(No.52103361)Shaanxi University Youth Outstanding Talents Support Plan,Scientific and Technological Plan Project of Xi’an Beilin District(No.GX2143)。
文摘Porous carbon(PC)is a promising electromagnetic(EM)wave absorbing material thanks to its light weight,large specific surface area as well as good dissipating capacity.To further improve its microwave absorbing performance,silver coated porous carbon(Ag@PC)is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork.Phase compositions,morphological structure,and microwave absorption capability of the Ag@PC has been explored.Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork,which accelerates graphitization process of the amorphous carbon.The Ag@PC composite without adding polyvinyl pyrrolidone(PVP)exhibits higher dielectric constant and better EM wave dissipating capability.This is because the larger particles of Ag give rise to higher electric conductivity.After combing with frequency selective surface(FSS),the EM wave absorbing performance is further improved and the frequency region below-10 d B is located in8.20-11.75 GHz,and the minimal reflection loss value is-22.5 dB.This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.
基金The authors would like to thank the Australian Research Council(ARC)for its financial support for the current study.We also acknowledge the use of facilities within the UOW Electron Microscopy Centre.
文摘Composite materials exhibit advantages from the combination of multiple properties,which cannot be achieved by a monolithic material.At present,the use of composite materials in miniaturized scale is receiving much attention in the fields of medicine,electronics,aerospace,and microtooling.A common method for producing miniaturized composite parts is micromanufacturing.There has been,however,no comprehensive literature published that reviews,compares,and discusses the ongoing micromanufacturing methods for producing miniaturized composite components.This study identifies the major micromanufacturing methods used with composite materials,categorizes their subclasses,and highlights the latest developments,new trends,and effects of key factors on the productivity,quality,and cost of manufacturing composite materials.A comparative study is presented that shows the potential and versatility associated with producing composite materials along with possible future applications.This review will be helpful in promoting micromanufacturing technology for fabricating miniaturized products made of composite materials to meet the growing industrial demand.
文摘The technology of Intelligent cure operation is set forth according to developing tedency of smart material and structure. Intelligent-system-based tool was developed in order to operate the autoclave cure of a fiber reinforced thermosetting matrix composite laminate in an optimal manner.The objective function is comforts for minimizing the total cure time,uniforming the temperature distribution,controling exothermal and minimizing the process-induced residual stresses in the laminate.Data is analyzed on-line to determine the trends in real-time.The results from application of this overall strategy for the curing of composites are presented.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11564024,51731001,and 11574122)the Fundamental Research Funds for the Central Universities,China(Grant No.lzujbky-2019-kb06).
文摘We establish a theoretical bimodal model for the complex permeability of flaky soft magnetic composite materials to explain the variability of their initial permeability.The new model is motivated by finding the two natural resonance peaks to be inconsistent with the combination of the domain wall resonance and the natural resonance.In the derivation of the model,two relationships are explored:the first one is the relationship between the number of magnetic domains and the permeability,and the second one is the relationship between the natural resonance and the domain wall resonance.This reveals that the ball milling causes the number of magnetic domains to increase and the maximum initial permeability to exist after 10 h of ball milling.An experiment is conducted to demonstrate the reliability of the proposed model.The experimental results are in good agreement with the theoretical calculations.This new model is of great significance for studying the mechanism and applications of the resonance loss for soft magnetic composite materials in high frequency fields.
文摘new surface infiltrating composite technique has been developed to obtain metal and ceramic composite layer on the surface of metal by traditional casting method. It has been shown that with the new method, a composite layer with a thickness of 2-5 mm can be obtained. The ceramic particulates distribute uniformly in the matrix. The composite layer is very favorable to wear resistance and thermal resistance
文摘Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous
文摘The application of mechanical and chemical syntheses in an high-energy vibration mill of the FESTU makes easy the process of the introduction of reinforced powders in castle composite materials on the Al basis. The obtained reinforced phases of Al-Ti-C composition have high specific Surface due to peculiarities of explosive mechanical and chemical syntheses. It increases the uniformity of their distribution in a matrix melt during the mixing process and also increases properties of castle composite materials.
文摘With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weight and increase the payload,composite material structures will be widely used. It is difficult to evaluate the strength and life of composite materials due to their complex mechanism and various phenomena in damage and failure.Meanwhile,the structures of composite materials used in spacecrafts will bear complex loads,including the coupling loads of tension,pressure,bending,shear,and torsion. Static loads,thermal loads,and vibration loads may occur at the same time,which asks for verification requirements to ensure the structure safety. Therefore,it is necessary to carry out a systematic multi-level experimental study. In this paper,the building block approach (BBA) is used to investigate the multilevel composite material structures for spacecrafts. The advanced measurement technology is adopted based on digital image correlation (DIC) and piezoelectric and optical fiber sensors to measure the composite material structure deformation. The virtual experiment technology is applied to provide sufficient and reliable data for the evaluation of the composite material structures of spacecrafts.
基金Project supported by the National Natural Science Foundation of China(No.11471262)
文摘The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspondence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale(SOTS) computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calculating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement approximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.
基金the support from Ministry of Science and Technology,Taiwan,R.O.C.,through grant MOST-105-2221-E-007-031-MY3.
文摘In this study,the deformation and stress distribution of printed circuit board(PCB)with different thickness and composite materials under a shock loading were analyzed by the finite element analysis.The standard 8-layer PCB subjected to a shock loading 1500 g was evaluated first.Moreover,the finite element models of the PCB with different thickness by stacking various number of layers were discussed.In addition to changing thickness,the core material of PCB was replaced from woven E-glass/epoxy to woven carbon fiber/epoxy for structural enhancement.The non-linear material property of copper foil was considered in the analysis.The results indicated that a thicker PCB has lower stress in the copper foil in PCBs under the shock loading.The stress difference between the thicker PCB(2.6 mm)and thinner PCB(0.6 mm)is around 5%.Using woven carbon fiber/epoxy as core material could lower the stress of copper foil around 6.6%under the shock loading 1500 g for the PCB with 0.6 mm thickness.On the other hand,the stress level is under the failure strength of PCBs with carbon fiber/epoxy core layers and thickness 2.6 mm when the peak acceleration changes from 1500 g to 5000 g.This study could provide a reference for the design and proper applications of the PCB with different thickness and composite materials.
基金National Important Science & Technology Specific Projects of China ( No. 2009ZX07317-006-02,No. 2009ZX07318-008-007)State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology,China ( No. 2013DX06)
文摘The oil sorption capacity of composite materials made up of different polymeric fabrics (namely acrylic fabric (AF), polypropylene nonwoven (PP), and silk stocking (SS) as composite out-packing materials) and expanded perlite (EP) was evaluated for oil removal from the water. The effects of sorbent dosage, desorption time, oil amount in the water, and contact time on composite materials sorption were investigated. The results showed that the optimum quantity of EP was between 0.5 g and 1.0 g for 25 cm2 polymeric fabrics bags. Oil removal efficiency for 6 L/m2 of oil amount in the water was 52%-72%, 44%-63%, and 37%-48% for AF, PP, and SS composite materials, respectively. Oil/water selectivity analysis of different composite materials showed that AF composite material had a very high degree of hydrophobicity and oil sorption capacity of approximately 10.17 g/g. Both oil sorption kinetics and equilibrium studies were carried out, and the equilibrium process of composite materials was described well by the Langmuir isotherm, and the oil sorption kinetics of composite materials showed good correlation coefficients for the pseudo-second order kinetic model. Intra-particle diffusion studies showed that oil sorption mechanism was controlled by the three processes, involving in external liquid membrane diffusion, surface sorption, and intra-particle diffusion.
基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(SJCX20_0935)。
文摘BiOIO3 is a layered semiconductor photocatalyst,which has good chemical properties and has attracted wide attention from researchers because of its unique structure.However,pure BiOIO3 has defects such as insufficient response to visible light and easy recombination of photogenerated electrons.Therefore,in recent years,scholars have tried to modify BiOIO3 to expand its light absorption range,reduce the recombination of photogenerated electron-hole pairs and reduce its limitations,thereby improving its visible light catalytic performance.Current researches focus on the improvement of the catalytic activity of photocatalytic materials from morphology control,precious metal deposition,ion doping and construction of heterojunctions.
文摘Initially,the materials used in the process of bridge construction were mainly wood,stone,etc.,and gradually the concrete,steel and other types of special materials currently in-use were developed.With the current vigorous development of science,technology and social economy in China,the development of bridge projects has also been accelerated to a large extent.In recent years,China has not only studied on how to strengthen the performance of concrete,steel and other materials in bridge projects,but also the performance of the recently developed smart,nano-,fibrous and other types of materials.This paper focuses on the application strategy of carbon fiber composite materials in bridge reconstruction projects to serve as a reference.
基金the financial support of the Russian Science Foundation(No.19-71-10060)。
文摘Non-destructive testing of composites is an important issue in the modern aircraft industry.Composites are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and operation.The continuum model for describing the damaged zone is presented.The slip theory relations used for a continuous distribution of slip planes are applied.At the initial stage,the isotropic background model is used.This model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous addition.In this regime,the govern system of equations becomes rigid.To overcome this difficulty,the explicit-implicit grid-characteristic scheme is proposed.The standard ultrasound diagnostic procedure of damaged composite materials is successfully simulated.Compared with the trivial free-surface fracture model,different reactions on the compression and stretch waves are registered.This approach provided an effective way for the simulation of complex dynamic behavior of damage zones.
基金This work was supported by the University of Science and Technology Liaoning(Grant Nos.601009816-39 and 2017RC03)the Liaoning Province Education Department of China(Grant Nos.601009887-16 and LJKQZ2021126)+1 种基金the National Natural Science Foundation of China(Grant Nos.51672117 and 51672118)the Postdoctoral Foundation Project of Shenzhen Polytechnic(Grant No.6020330007K).
文摘The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies of MnO_(2)@C materials can be controlled by controlling the dosages of WS-CTPs and KMnO4.Meanwhile,it is aware that MnO_(2)exists in the MnO_(2)@C materials in an amorphous state.Compared with MnO_(2),MnO_(2)@C materials output a remarkable improvement in electrochemical performance.For instance,MnO_(2)@C-0.3 shows the storage capacity at 965.7 mA h g^(−1)after 300 cycles at a current density of 0.1 A g^(−1).In addition,after 600 cycles at a current density of 1.0 A g^(−1),the storage capacity of MnO_(2)@C-0.3 still keeps 450.3 mA h g^(−1),indicating that MnO_(2)@C-0.3 owns tremendous cycle stability at a high current density.In view of the fact that the coal tar pitches possess great cost advantages,the strategy of using WS-CTPs as a carbon source to cover the metal oxides is a competitive way to expand the application of metal oxides in the fabrication of electrodes of LIBs.
基金This work was partially supported by the NSFC Projects No.12025104,11871298,81930119.
文摘In this paper,we generalize the direct method of lines for linear elasticity problems of composite materials in star-shaped domains and consider its application to inverse elasticity problems.We assume that the boundary of the star-shaped domain can be described by an explicit C 1 parametric curve in the polar coordinate.We introduce the curvilinear coordinate,in which the irregular star-shaped domain is converted to a regular semi-infinite strip.The equations of linear elasticity are discretized with respect to the angular variable and we solve the resulting semidiscrete approximation analytically using a direct method.The eigenvalues of the semi-discrete approximation converge quickly to the true eigenvalues of the elliptic operator,which helps capture the singularities naturally.Moreover,an optimal error estimate of our method is given.For the inverse elasticity problems,we determine the Lam´e coefficients from measurement data by minimizing a regularized energy functional.We apply the direct method of lines as the forward solver in order to cope with the irregularity of the domain and possible singularities in the forward solutions.Several numerical examples are presented to show the effectiveness and accuracy of our method for both forward and inverse elasticity problems of composite materials.
