To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected t...To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected to flexural load are experimentally compared. The experimental results show that the flexural strength and ductility of the steel reinforced ECC beam are 24.8% and 187.67% times larger than those of the steel reinforced concrete beam, and the substitution of concrete with ECC can significantly delay the propagation of cracks. Additionally, a simplified constitutive model of the ECC material is used to simulate the flexural behaviors of beams by the finite element analysis （FEA）. The results show a good agreement between the simulation and test results. The crack width of the steel reinforced ECC beam can be limited to 0.4 mm under the service load conditions. The application of ductile ECC can significantly increase the flexural performance in terms of flexural strength, deformation capacity and ductility of the beams.展开更多
An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increas...An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increase the ductility and crack resisting ability of the beam. Based on the assumption of the plane remaining plane and the simplified constitutive models of materials, the stress and strain distributions along the depth of the composite beam in different loading stages are comprehensively investigated to obtain calculation methods of the load-carrying capacities for different stages. Also, a simplified formula for the ultimate load carrying capacity is proposed according to the Chinese code for the design of concrete structures. The relationship between the moment and curvature for the composite beam is also proposed together with a simplified calculation method for ductility of the ECC/RC composite beam. Finally, the calculation method is demonstrated with the test results of a composite beam. Comparison results show that the calculation results have good consistency with the test results, proving that the proposed calculation methods are reliable with a certain theoretical significance and reference value.展开更多
Removal of Cr（VI） from aqueous solution by strong alkaline anion exchange fiber （SAAEF） was achieved using batch adsorption experiments. The effect of contact time, initial Cr（VI） concentration and pH was invest...Removal of Cr（VI） from aqueous solution by strong alkaline anion exchange fiber （SAAEF） was achieved using batch adsorption experiments. The effect of contact time, initial Cr（VI） concentration and pH was investigated. The results showed that the maximum adsorption capacity of SAAEF was 187.7 mg/g at pH=1.0. The adsorption capacity increased with Cr（VI） concentration but decreased with pH value when pH〉1.0. Adsorption isotherms at various temperatures were obtained. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models were adopted and the equilibrium data fitted best with the Langmuir isotherm. The constants of these models indicated that the adsorption process involved both chemisorption and physisorption. The values of thermodynamic parameters, including DH, DG and DS, suggested that the adsorption of Cr（VI） on SAAEF was a spontaneous, entropy-driven and endothermic process. Q（iso） was not a constant value, which indicated an inhomogenous energy distribution on SAAEF.展开更多
This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether ...This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP）. The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.展开更多
This article summarizes the comparison between the preparation, structure and mechanical properties of long fiber reinforced thermoplastics （LFT） and short fiber reinforced thermoplastics （SFT）. Both of the experi...This article summarizes the comparison between the preparation, structure and mechanical properties of long fiber reinforced thermoplastics （LFT） and short fiber reinforced thermoplastics （SFT）. Both of the experiment and theory results showed that the mechanical properties of long glass fiber reinforced thermoplastics pellets （LGFRT） have been enhanced better than that of short glass fiber reinforced thermoplastics pellets （SGFRT） manufactured by molding procession. After regulation of the relative humidity by 50 % , the mechanical properties of 30 % （ weight percent） short glass fiber content in SFT （ SFT-PA6-SGF30 ） are similar to that of 40 % long glass fiber content in LFT. Howev- er, the density of the latter is about 17 % lower than that of the former. Thus, the corresponding weight of products is reduced by 13 % ;output rate is increased by 21% , and the cost is therefore significantly lowered. And it has the fol- lowing advantages： impact strength is increased by 87 % ; the proportion is reduced by 20 % ; molding cycle is short- ened by 10 % ;materials cost is saved by 20 % -30 % and the final total cost is saved by 30 % -40 %. So LFT （LFT-PP-LGF40） can replace SFT （SFT-PA6-SGF30） with the similar basic mechanical properties under normal tem- perature or 160 ℃ lower.展开更多
To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite col...To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.展开更多
In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping pr...In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping properties of the samples are improved by controlling both the Zn/Al diffusion degree and the precipitation of the interfacial phases.The results show that the tensile strength of the samples with Zn mass fraction of 10%-30%increases with the increases of both the Zn content and annealing temperature.When the Zn mass fraction increases to 40%,the tensile strength of the sample remains basically unchanged or decreases slightly,and the plasticity decreases gradually.Alloying of Al matrix and the formation of Zn/Al interface layer are mainly responsible for improving the strength of the annealed samples.The damping properties increase with the increases of both the Zn content and annealing temperature.The Zn/Al eutectoid lamella eliminates the detrimental effects on damping properties due to both alloying of the Al matrix and reduction of pure Zn in the Al matrix.The Al-30%Zn sample annealed at 350°C for 0.5 h has good comprehensive properties,including the tensile strength of 330 MPa,the elongation to failure of 10%and the room-temperature damping properties(tanθ)of 0.025.展开更多
In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretica...In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretical analyses of the SRECC beam including crack propagation and stress-strain distributions along the depth of the composite beam in different loading stages are conducted. A theoretical model and simplified design method are proposed to calculate the load carrying capacity. Based on the proposed theoretical model, the relationship between the moment and corresponding curvature is derived. The theoretical results are verified with the finite element analysis. Finally, an extensive parametric study is performed to study the effect of the matrix type, steel shape ratio, reinforced bar ratio, ECC compressive strength and ECC tensile ductility on the mechanical behavior of SRECC beams. The results show that substitution concrete with ECC can effectively improve the bearing capacity and ductility of composite beams. The steel shape and longitudinal reinforcement can enhance the loading carrying capacity, while the ductility decreases with the increase of steel shape ratio. ECC compressive strength has significant effects on both load carrying capacity and ductility, and changing the ultimate strain of ECC results in a very limited variation in the mechanical behavior of SRECC beams.展开更多
This study aims to reveal the mechanism that how the content of steel fibers and strength grades affect the macro performance of the ultra-high performance fiber reinforced cementitious composite （UHPFRCC） and to st...This study aims to reveal the mechanism that how the content of steel fibers and strength grades affect the macro performance of the ultra-high performance fiber reinforced cementitious composite （UHPFRCC） and to study the UHPFRCC durability under the combined effect of loads and environments. Three types of high and ultra-high performance fiber reinforced cement composites with different strength grades （100, 150, 200 MPa） and different steel fiber volume fractions （0%, 1%, 2%, 3%） are prepared. The main properties of mechanical performance and short-term durability are studied. A preloading frame is designed to apply a four- point load external flexural stress with a stress selection ratio of 0.5 for UHPFRCC150 specimens. The results show that the growth in strength grade with a proper content of steel fiber greatly increases the strength and toughness of the HPFRCC and the UHPFRCC while decreasing the dry-shrinkage ratio. For the loaded specimens, the existence of steel fiber can reduce the negative influence of tensile stress on the Cl- penetration resistance of the UHPFRCC in addition to improving its ability to resist the freeze-thaw damage.展开更多
The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced ...The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.展开更多
Given the increasing use of glass mat-reinforced thermoplastic(GMT)composites,the formability of GMT sheets is currently a topic of research.A new sheet forming process for solidified GMT was developed.In this process...Given the increasing use of glass mat-reinforced thermoplastic(GMT)composites,the formability of GMT sheets is currently a topic of research.A new sheet forming process for solidified GMT was developed.In this process,a GMT sheet was sandwiched by dummy metallic sheets during deep drawing.The dummy metallic sheets acted as protective materials and media for heating the GMT sheet.In this study,tensile tests of GMT specimens were carried out under different temperature conditions.The effect of temperature on the tensile deformation was analyzed.The effect of temperature on the deep drawing process of GMT sheets with dummy sheets was further investigated.Finite element method(FEM)was conducted to simulate the deep drawing process.In the drawing force rising stage,the law of drawing force with the depth of the drawing was analyzed using FEM and experiments.展开更多
Introduction:Desmoid-type fibromatosis(DF)is a fibrous tumor characterized by low-grade malignant and easy invasive growth and high recurrence.High-intensity focused ultrasound(HIFU)therapy has been identified as a no...Introduction:Desmoid-type fibromatosis(DF)is a fibrous tumor characterized by low-grade malignant and easy invasive growth and high recurrence.High-intensity focused ultrasound(HIFU)therapy has been identified as a novel non-invasive approach for DF treatment;however,the ultrasonic energy generated by HIFU can cause skin heat injury.Case:A 31-year-old female patient with signs and symptoms of DF received treatment in our institution.The patient had undergone HIFU treatment six times from April 27,2018,to August 21,2019.After HIFU therapy for the third time,she had a third-degree skin burn showing as orange peel-like change and spent three months to promote the recovery of the skin lesions.An intermittent ice-cooling strategy was used to avoid skin damage during the fourth HIFU treatment.This patient did not have any apparent skin injury during the last three HIFU therapy and acquired satisfactory anti-tumor therapeutic effect.Conclusions:There are differences in the thermal selectivity of tumor tissues,which leads to different critical thermal injury temperature values that the tissue can tolerate.Ice-cooling can lower skin tissue temperature and reduce the thermal damage caused by HIFU treatment.展开更多
The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmen...The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.展开更多
This study has developed an efficient method to achieve excellent thermal dimensional stability and desired dimensions of hollow polyester fiber. Firstly,the influence of thermal treatment temperate( 140-180 ℃) on th...This study has developed an efficient method to achieve excellent thermal dimensional stability and desired dimensions of hollow polyester fiber. Firstly,the influence of thermal treatment temperate( 140-180 ℃) on the degree of shrinkage of fiber was investigated. The influence was also analyzed with a 2nd heating to simulate the application situation. It was discovered that the heat treatment at a temperature which was above the application temperature( 2nd heating) would efficiently remove the internal stress in the fiber and improve the thermal dimensional stability.Secondly,the impact of heat treatment temperature on the fiber diameter and the degree of hollowness were studied. The results implied that with a fixed fiber length, higher treatment temperature led to thinner fiber and a lower degree of hollowness.Last but not least,key parameters that could further influence the fiber dimensions were investigated. The results suggested that the fiber diameters and the degree of hollowness could be further controlled by tuning the drawing speed,the spinning meter pump output and cooling status while the spinneret parameters were fixed.展开更多
The use of steel reinforced concrete facade is gradually becoming unpopular because of the damage caused to the elements as a result of corrosion of the steel reinforcement. It is now possible to build lightweight and...The use of steel reinforced concrete facade is gradually becoming unpopular because of the damage caused to the elements as a result of corrosion of the steel reinforcement. It is now possible to build lightweight and slender concrete structures which are invulnerable to corrosion with the use of fiber reinforcements, which are gradually replacing the corrosion prone steel. This paper describes the construction of faqade panels made of rattan cane reinforcements and steel reinforcements, ten number model sized elements of area 0.15 m2 and a depth of 40 mm were considered, with five panels for each reinforcement type. The elements were subjected to incremental load of 1 kN until failure occurred. Deflections were measured for each element, and crack width was measured at failure load. The results for both types of reinforcements when compared showed the rattan cane reinforced panels failing earlier than the steel reinforced panels. However a lower defection and crack width was recorded in the rattan cane reinforced panel. This paper concludes that the lower crack width formed after failure in the rattan cane reinforced panel gave it advantage over the steel reinforced panel, since it has lower space for the ingress of water which is the main agents of corrosion.展开更多
CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing techni...CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.展开更多
The compressive strength and ilexural toughness as well as fracture energy of fiber reinforced highperformance concrete （FRHPC） subjected to different high temperatures were studied. The results showed that after ex...The compressive strength and ilexural toughness as well as fracture energy of fiber reinforced highperformance concrete （FRHPC） subjected to different high temperatures were studied. The results showed that after exposure at 300,600 and 900℃, the concrete mixes retained 88.1% , 41.3% and 10.2% of the original compressive strength on average, respectively. Steel fiber and polypropylene （PP） fiber were both effective in minimizing the damage effect of high temperatures on the compressive strength. The HPC reinforced with steel fibers showed higher flexural toughness and fracture energy before and after the high-temperature exposures. In comparison, PP fibers had minor beneficial effects on the flexural toughness and fracture energy. The mechanical properties of HPC reinforced with hybrid fibers （steel fiber ＋ PP fiber） were equivalent to or better than those of HPC reinforced with steel fibers alone. In addition, the failure pattern of FRHPC beams changed from pull-out of steel fibers at lower temperatures （20, 300 and 600℃） to tensile failure of steel fibers at higher temperature （900 ℃）.展开更多
This paper concerns the bond strength of FRP bars in AAC by the concentric pullout test. Specimens were subjected to compare with mild steel bars. The bond performance including the mode of failure and bond strength w...This paper concerns the bond strength of FRP bars in AAC by the concentric pullout test. Specimens were subjected to compare with mild steel bars. The bond performance including the mode of failure and bond strength was investigated with varying embedment length and surface treatment. Regarding the bond performance, embedment depth has influenced on bond strength as well as the sanded surface. Carbon fiber reinforced polymer （CFRP） pronounced the most promising results with the highest bond strength attained.展开更多
To discuss the applicability of advanced composite carbon fiber reinforced polymer(CFRP) and ultrahigh performance concrete reactive powder concrete(RPC) in super-long span cable-stayed bridges, taking a 1 008 m cable...To discuss the applicability of advanced composite carbon fiber reinforced polymer(CFRP) and ultrahigh performance concrete reactive powder concrete(RPC) in super-long span cable-stayed bridges, taking a 1 008 m cable-stayed bridge with steel girders and steel cables as an example,a new cable-stayed bridge in the same span with RPC girders and CFRP cables was designed,in which the cable's cross section was determined by the principle of equivalent cable capacity and the girder's cross section was determined in virtual of its stiffness, shear capacity and local stability. Based on the methods of finite element analysis,the comparative analysis of these two cable-stayed bridge schemes about static performances,dynamic performances,stability and wind resistance behavior were carried out. The results showed that it was feasible to form a highly efficient,durable concrete cable-stayed bridge with RPC girders and CFRP cables and made its applicable span range expand to 1 000 m long around.展开更多
基金The National Natural Science Foundation of China(No.51278118)the National Basic Research Program of China(973Program)(No.2009CB623200)the Natural Science Foundation of Jiangsu Province(No.BK2012756)
文摘To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected to flexural load are experimentally compared. The experimental results show that the flexural strength and ductility of the steel reinforced ECC beam are 24.8% and 187.67% times larger than those of the steel reinforced concrete beam, and the substitution of concrete with ECC can significantly delay the propagation of cracks. Additionally, a simplified constitutive model of the ECC material is used to simulate the flexural behaviors of beams by the finite element analysis （FEA）. The results show a good agreement between the simulation and test results. The crack width of the steel reinforced ECC beam can be limited to 0.4 mm under the service load conditions. The application of ductile ECC can significantly increase the flexural performance in terms of flexural strength, deformation capacity and ductility of the beams.
基金The National Natural Science Foundation of China(No. 50808043)the National Basic Research Program of China (973 Program) (No. 2009CB623200)Foundation of Jiangsu Key Laboratory of Construction Materials,Program for Special Talents in Six Fields of Jiangsu Province(No. 2011-JZ-010)
文摘An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increase the ductility and crack resisting ability of the beam. Based on the assumption of the plane remaining plane and the simplified constitutive models of materials, the stress and strain distributions along the depth of the composite beam in different loading stages are comprehensively investigated to obtain calculation methods of the load-carrying capacities for different stages. Also, a simplified formula for the ultimate load carrying capacity is proposed according to the Chinese code for the design of concrete structures. The relationship between the moment and curvature for the composite beam is also proposed together with a simplified calculation method for ductility of the ECC/RC composite beam. Finally, the calculation method is demonstrated with the test results of a composite beam. Comparison results show that the calculation results have good consistency with the test results, proving that the proposed calculation methods are reliable with a certain theoretical significance and reference value.
基金Project (20080242009) supported by Basic Research Foundation of Beijing Institute of Technology, China
文摘Removal of Cr（VI） from aqueous solution by strong alkaline anion exchange fiber （SAAEF） was achieved using batch adsorption experiments. The effect of contact time, initial Cr（VI） concentration and pH was investigated. The results showed that the maximum adsorption capacity of SAAEF was 187.7 mg/g at pH=1.0. The adsorption capacity increased with Cr（VI） concentration but decreased with pH value when pH〉1.0. Adsorption isotherms at various temperatures were obtained. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models were adopted and the equilibrium data fitted best with the Langmuir isotherm. The constants of these models indicated that the adsorption process involved both chemisorption and physisorption. The values of thermodynamic parameters, including DH, DG and DS, suggested that the adsorption of Cr（VI） on SAAEF was a spontaneous, entropy-driven and endothermic process. Q（iso） was not a constant value, which indicated an inhomogenous energy distribution on SAAEF.
基金The Scholarship Supported by the China Scholarship Councilthe Technical Research Program from NV Bekaert SA of Belgiumthe National Natural Science Foundation of China(No.50908047)
文摘This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP）. The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.
文摘This article summarizes the comparison between the preparation, structure and mechanical properties of long fiber reinforced thermoplastics （LFT） and short fiber reinforced thermoplastics （SFT）. Both of the experiment and theory results showed that the mechanical properties of long glass fiber reinforced thermoplastics pellets （LGFRT） have been enhanced better than that of short glass fiber reinforced thermoplastics pellets （SGFRT） manufactured by molding procession. After regulation of the relative humidity by 50 % , the mechanical properties of 30 % （ weight percent） short glass fiber content in SFT （ SFT-PA6-SGF30 ） are similar to that of 40 % long glass fiber content in LFT. Howev- er, the density of the latter is about 17 % lower than that of the former. Thus, the corresponding weight of products is reduced by 13 % ;output rate is increased by 21% , and the cost is therefore significantly lowered. And it has the fol- lowing advantages： impact strength is increased by 87 % ; the proportion is reduced by 20 % ; molding cycle is short- ened by 10 % ;materials cost is saved by 20 % -30 % and the final total cost is saved by 30 % -40 %. So LFT （LFT-PP-LGF40） can replace SFT （SFT-PA6-SGF30） with the similar basic mechanical properties under normal tem- perature or 160 ℃ lower.
基金The National Natural Science Foundation of China(No.51278118)the Natural Science Foundation of Jiangsu Province(No.BK2012756)+1 种基金the Key Project of Ministry of Education of China(No.113029A)the Third Five-Year Major Scientific and Technological Project of China Metallurgical Group Corporation
文摘To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.
基金Project(2016YFB0300901)supported by the National Key Research and Development Program of China
文摘In order to develop high strength,high damping and low density Al matrix composites,the Al/Zn composite bar samples with Zn mass fraction of 10%-40%were prepared by powder extrusion.The tensile strength and damping properties of the samples are improved by controlling both the Zn/Al diffusion degree and the precipitation of the interfacial phases.The results show that the tensile strength of the samples with Zn mass fraction of 10%-30%increases with the increases of both the Zn content and annealing temperature.When the Zn mass fraction increases to 40%,the tensile strength of the sample remains basically unchanged or decreases slightly,and the plasticity decreases gradually.Alloying of Al matrix and the formation of Zn/Al interface layer are mainly responsible for improving the strength of the annealed samples.The damping properties increase with the increases of both the Zn content and annealing temperature.The Zn/Al eutectoid lamella eliminates the detrimental effects on damping properties due to both alloying of the Al matrix and reduction of pure Zn in the Al matrix.The Al-30%Zn sample annealed at 350°C for 0.5 h has good comprehensive properties,including the tensile strength of 330 MPa,the elongation to failure of 10%and the room-temperature damping properties(tanθ)of 0.025.
基金The National Natural Science Foundation of China(No.51778183)the National Key Research and Development Program of China(No.2016YFC0701907)the Distinguished Young Scholar Foundation of Jiangsu Province(No.BK20160027)
文摘In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretical analyses of the SRECC beam including crack propagation and stress-strain distributions along the depth of the composite beam in different loading stages are conducted. A theoretical model and simplified design method are proposed to calculate the load carrying capacity. Based on the proposed theoretical model, the relationship between the moment and corresponding curvature is derived. The theoretical results are verified with the finite element analysis. Finally, an extensive parametric study is performed to study the effect of the matrix type, steel shape ratio, reinforced bar ratio, ECC compressive strength and ECC tensile ductility on the mechanical behavior of SRECC beams. The results show that substitution concrete with ECC can effectively improve the bearing capacity and ductility of composite beams. The steel shape and longitudinal reinforcement can enhance the loading carrying capacity, while the ductility decreases with the increase of steel shape ratio. ECC compressive strength has significant effects on both load carrying capacity and ductility, and changing the ultimate strain of ECC results in a very limited variation in the mechanical behavior of SRECC beams.
基金The Technical Research Program from NV Bekaert SA of Belgium (No. 8612000003)the National Natural Science Foundation of China (No. 50908047)
文摘This study aims to reveal the mechanism that how the content of steel fibers and strength grades affect the macro performance of the ultra-high performance fiber reinforced cementitious composite （UHPFRCC） and to study the UHPFRCC durability under the combined effect of loads and environments. Three types of high and ultra-high performance fiber reinforced cement composites with different strength grades （100, 150, 200 MPa） and different steel fiber volume fractions （0%, 1%, 2%, 3%） are prepared. The main properties of mechanical performance and short-term durability are studied. A preloading frame is designed to apply a four- point load external flexural stress with a stress selection ratio of 0.5 for UHPFRCC150 specimens. The results show that the growth in strength grade with a proper content of steel fiber greatly increases the strength and toughness of the HPFRCC and the UHPFRCC while decreasing the dry-shrinkage ratio. For the loaded specimens, the existence of steel fiber can reduce the negative influence of tensile stress on the Cl- penetration resistance of the UHPFRCC in addition to improving its ability to resist the freeze-thaw damage.
基金Funded by key project of the National Natural Science Foundation of China (50238040).
文摘The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.
基金Project(CG2016003001) supported by the Ministry of Human Resources and Social Security of China
文摘Given the increasing use of glass mat-reinforced thermoplastic(GMT)composites,the formability of GMT sheets is currently a topic of research.A new sheet forming process for solidified GMT was developed.In this process,a GMT sheet was sandwiched by dummy metallic sheets during deep drawing.The dummy metallic sheets acted as protective materials and media for heating the GMT sheet.In this study,tensile tests of GMT specimens were carried out under different temperature conditions.The effect of temperature on the tensile deformation was analyzed.The effect of temperature on the deep drawing process of GMT sheets with dummy sheets was further investigated.Finite element method(FEM)was conducted to simulate the deep drawing process.In the drawing force rising stage,the law of drawing force with the depth of the drawing was analyzed using FEM and experiments.
基金supported by the Medical and Health Science and Technology Project of Zhejiang Province(No.2019325236)the Appropriate Technology Cultivation and Promotion Project of Zhejiang Medical and Health Office(2019325236).
文摘Introduction:Desmoid-type fibromatosis(DF)is a fibrous tumor characterized by low-grade malignant and easy invasive growth and high recurrence.High-intensity focused ultrasound(HIFU)therapy has been identified as a novel non-invasive approach for DF treatment;however,the ultrasonic energy generated by HIFU can cause skin heat injury.Case:A 31-year-old female patient with signs and symptoms of DF received treatment in our institution.The patient had undergone HIFU treatment six times from April 27,2018,to August 21,2019.After HIFU therapy for the third time,she had a third-degree skin burn showing as orange peel-like change and spent three months to promote the recovery of the skin lesions.An intermittent ice-cooling strategy was used to avoid skin damage during the fourth HIFU treatment.This patient did not have any apparent skin injury during the last three HIFU therapy and acquired satisfactory anti-tumor therapeutic effect.Conclusions:There are differences in the thermal selectivity of tumor tissues,which leads to different critical thermal injury temperature values that the tissue can tolerate.Ice-cooling can lower skin tissue temperature and reduce the thermal damage caused by HIFU treatment.
文摘The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.
基金Innovation Fund Project of National Commercial Aircraft Manufacturing Engineering Research Center(No.SAM C14-JS-15-048)Natural Science Foundation of Shanghai,China(No.13ZR1400400)the Fundamental Research Funds for the Central Universities,China
文摘This study has developed an efficient method to achieve excellent thermal dimensional stability and desired dimensions of hollow polyester fiber. Firstly,the influence of thermal treatment temperate( 140-180 ℃) on the degree of shrinkage of fiber was investigated. The influence was also analyzed with a 2nd heating to simulate the application situation. It was discovered that the heat treatment at a temperature which was above the application temperature( 2nd heating) would efficiently remove the internal stress in the fiber and improve the thermal dimensional stability.Secondly,the impact of heat treatment temperature on the fiber diameter and the degree of hollowness were studied. The results implied that with a fixed fiber length, higher treatment temperature led to thinner fiber and a lower degree of hollowness.Last but not least,key parameters that could further influence the fiber dimensions were investigated. The results suggested that the fiber diameters and the degree of hollowness could be further controlled by tuning the drawing speed,the spinning meter pump output and cooling status while the spinneret parameters were fixed.
文摘The use of steel reinforced concrete facade is gradually becoming unpopular because of the damage caused to the elements as a result of corrosion of the steel reinforcement. It is now possible to build lightweight and slender concrete structures which are invulnerable to corrosion with the use of fiber reinforcements, which are gradually replacing the corrosion prone steel. This paper describes the construction of faqade panels made of rattan cane reinforcements and steel reinforcements, ten number model sized elements of area 0.15 m2 and a depth of 40 mm were considered, with five panels for each reinforcement type. The elements were subjected to incremental load of 1 kN until failure occurred. Deflections were measured for each element, and crack width was measured at failure load. The results for both types of reinforcements when compared showed the rattan cane reinforced panels failing earlier than the steel reinforced panels. However a lower defection and crack width was recorded in the rattan cane reinforced panel. This paper concludes that the lower crack width formed after failure in the rattan cane reinforced panel gave it advantage over the steel reinforced panel, since it has lower space for the ingress of water which is the main agents of corrosion.
文摘CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.
基金Sponsored by the National Natural Science Foundation of China (Grant No.50278013)
文摘The compressive strength and ilexural toughness as well as fracture energy of fiber reinforced highperformance concrete （FRHPC） subjected to different high temperatures were studied. The results showed that after exposure at 300,600 and 900℃, the concrete mixes retained 88.1% , 41.3% and 10.2% of the original compressive strength on average, respectively. Steel fiber and polypropylene （PP） fiber were both effective in minimizing the damage effect of high temperatures on the compressive strength. The HPC reinforced with steel fibers showed higher flexural toughness and fracture energy before and after the high-temperature exposures. In comparison, PP fibers had minor beneficial effects on the flexural toughness and fracture energy. The mechanical properties of HPC reinforced with hybrid fibers （steel fiber ＋ PP fiber） were equivalent to or better than those of HPC reinforced with steel fibers alone. In addition, the failure pattern of FRHPC beams changed from pull-out of steel fibers at lower temperatures （20, 300 and 600℃） to tensile failure of steel fibers at higher temperature （900 ℃）.
文摘This paper concerns the bond strength of FRP bars in AAC by the concentric pullout test. Specimens were subjected to compare with mild steel bars. The bond performance including the mode of failure and bond strength was investigated with varying embedment length and surface treatment. Regarding the bond performance, embedment depth has influenced on bond strength as well as the sanded surface. Carbon fiber reinforced polymer （CFRP） pronounced the most promising results with the highest bond strength attained.
基金National Natural Science Foundation of China(No.51078134)Natural Science Foundation of Jiangxi Province(No.20114BAB206010)Department of Education Foundation of Jiangxi Province(No.GJJ11449)
文摘To discuss the applicability of advanced composite carbon fiber reinforced polymer(CFRP) and ultrahigh performance concrete reactive powder concrete(RPC) in super-long span cable-stayed bridges, taking a 1 008 m cable-stayed bridge with steel girders and steel cables as an example,a new cable-stayed bridge in the same span with RPC girders and CFRP cables was designed,in which the cable's cross section was determined by the principle of equivalent cable capacity and the girder's cross section was determined in virtual of its stiffness, shear capacity and local stability. Based on the methods of finite element analysis,the comparative analysis of these two cable-stayed bridge schemes about static performances,dynamic performances,stability and wind resistance behavior were carried out. The results showed that it was feasible to form a highly efficient,durable concrete cable-stayed bridge with RPC girders and CFRP cables and made its applicable span range expand to 1 000 m long around.
