The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional...The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional fabrics to manufacturing integral three-dimensional near-netshaped textile preforms are high cost and database deficiency.To reduce the cost of weaving three-dimensional preforms,and make full use of the potential of conventional looms,a rig was designedwhich can convert two-dimensional woven fabric to particular three-dimensional preforms wherethe yarn is orientated in the directions of maximum stress.展开更多
Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled pre...Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.展开更多
Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by th...Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.展开更多
With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming ...With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.展开更多
Dispersoid formation and microstructural evolution in an oxide dispersion-strengthened CoCrFeMnNi high-entropy alloy(HEA)using a newly designed multistep sintering process are investigated.The proposed multistep sinte...Dispersoid formation and microstructural evolution in an oxide dispersion-strengthened CoCrFeMnNi high-entropy alloy(HEA)using a newly designed multistep sintering process are investigated.The proposed multistep sintering consists of a dispersoid preforming heat treatment of as-milled 0.1 wt%Y_(2)O_(3)-CoCrFeMnNi high-entropy alloy powders at 800℃,followed by sintering at 800–1000℃ under uniaxial pressure.In the conventional single-step sintered bulk,the coarsened BCC Y_(2)O_(3)dispersoids mainly form with an incoherent interface with the HEA matrix.In contrast,finer FCC Y_(2)O_(3)dispersoids,an atypical form of Y_(2)O_(3),are formed in the matrix region after multistep sintering.Nucleation of FCC Y_(2)O_(3)disper-soids is initiated on the favorable facet,the{111}plane of the austenitic matrix,with the formation of a semi-coherent interface with the matrix during the dispersoid preforming heat treatment and it maintains its refined size even after sintering.It is found that dispersoid preforming prior to sintering appears promising to control the finer dispersoid formation and refined grain structure.展开更多
文摘The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional fabrics to manufacturing integral three-dimensional near-netshaped textile preforms are high cost and database deficiency.To reduce the cost of weaving three-dimensional preforms,and make full use of the potential of conventional looms,a rig was designedwhich can convert two-dimensional woven fabric to particular three-dimensional preforms wherethe yarn is orientated in the directions of maximum stress.
基金Supported by Jiangsu Provincial Frontier Leading Technology Basic Research Project(Grant No.BK20212007)Aero-Engine and Gas Turbine Basic Science Center(Grant No.P2022-B-IV-014-001)+1 种基金China Postdoctoral Program Fund(Grant No.1005/YBA23044)China Postdoctoral Assistance Fund(Grant No.1005/YBA23031)。
文摘Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.
基金supported by the Materials&Components Technology Development Program(10080187)funded by the Ministry of Trade,Industry&Energy(MI,Korea)。
文摘Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.
文摘With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.
基金supported by the National Research Foundation of the Ministry of Science and ICT(MSIT)of the Republic of Korea(Nos.2021R1A2C2014025,2020R1A5A6017701,and 2022M3H4A1A02076759)。
文摘Dispersoid formation and microstructural evolution in an oxide dispersion-strengthened CoCrFeMnNi high-entropy alloy(HEA)using a newly designed multistep sintering process are investigated.The proposed multistep sintering consists of a dispersoid preforming heat treatment of as-milled 0.1 wt%Y_(2)O_(3)-CoCrFeMnNi high-entropy alloy powders at 800℃,followed by sintering at 800–1000℃ under uniaxial pressure.In the conventional single-step sintered bulk,the coarsened BCC Y_(2)O_(3)dispersoids mainly form with an incoherent interface with the HEA matrix.In contrast,finer FCC Y_(2)O_(3)dispersoids,an atypical form of Y_(2)O_(3),are formed in the matrix region after multistep sintering.Nucleation of FCC Y_(2)O_(3)disper-soids is initiated on the favorable facet,the{111}plane of the austenitic matrix,with the formation of a semi-coherent interface with the matrix during the dispersoid preforming heat treatment and it maintains its refined size even after sintering.It is found that dispersoid preforming prior to sintering appears promising to control the finer dispersoid formation and refined grain structure.
