2017 Vol. 34, No. 1
2017, 34(1): 1-11.
doi: 10.13801/j.cnki.fhclxb.20160328.012
Abstract:
Excellent specific stiffness, good thermal stability and diversiform designability are obvious characteristics of carbon fiber composite(CFRP), which make it a new ideal material for the lightweight reflectors, especially for large diameter and high resolution space reflectors. The present situation of the research of optical mirrors in our country and on abroad was briefly introduced. Then according to the characteristics of mirrors, selection requirements of carbon fiber composite for mirror and foreign prepreg system commonly used were introduced. Manufacturing method of carbon fiber composite optical mirror is different from that of the traditional optical materials. Usually, the high efficiency, fast and low cost replication process is used for carbon fiber composite mirror. The optical replication of carbon fiber composite mirrors, and factors affecting the accuracy of replicated mirror were emphatically introduced, and the factors including the mould, prepreg layup, deformation of mirror, fiber print-through, dimensional stability and size of mirror, etc. And the corresponding control measures to reduce the influence degree were put forward for the former five factors. Causes and solutions of mirror fiber print-through, and the key to control dimensional stability of mirror were focused.
Excellent specific stiffness, good thermal stability and diversiform designability are obvious characteristics of carbon fiber composite(CFRP), which make it a new ideal material for the lightweight reflectors, especially for large diameter and high resolution space reflectors. The present situation of the research of optical mirrors in our country and on abroad was briefly introduced. Then according to the characteristics of mirrors, selection requirements of carbon fiber composite for mirror and foreign prepreg system commonly used were introduced. Manufacturing method of carbon fiber composite optical mirror is different from that of the traditional optical materials. Usually, the high efficiency, fast and low cost replication process is used for carbon fiber composite mirror. The optical replication of carbon fiber composite mirrors, and factors affecting the accuracy of replicated mirror were emphatically introduced, and the factors including the mould, prepreg layup, deformation of mirror, fiber print-through, dimensional stability and size of mirror, etc. And the corresponding control measures to reduce the influence degree were put forward for the former five factors. Causes and solutions of mirror fiber print-through, and the key to control dimensional stability of mirror were focused.
2017, 34(1): 12-22.
doi: 10.13801/j.cnki.fhclxb.20160523.017
Abstract:
The excellent mechanical properties of carbon nanotube (CNT) make it a preferred reinforcement for composites. The mechanical properties of CNT/polymer composites are greatly determined by the interfacial bonding characteristics. Both research methods and research progresses of the interfacial bonding characteristics of CNT/polymer composites were reviewed in this paper. Microscopic characterization techniques, raman spectroscopy analysis technology and nano-mechanical pull-out method were used in the experiment. Molecular simulation method simulated the pull-out process of CNT from the polymer matrix by applying displacement and force to CNT. The effects of polymer matrix (including type, crystal structure and density) and CNT (including chirality, diameter and functional processing) on the interfacial bonding characteristics of CNT/polymer composites were summarized and the signi-ficant future research directions of this field were prospected.
The excellent mechanical properties of carbon nanotube (CNT) make it a preferred reinforcement for composites. The mechanical properties of CNT/polymer composites are greatly determined by the interfacial bonding characteristics. Both research methods and research progresses of the interfacial bonding characteristics of CNT/polymer composites were reviewed in this paper. Microscopic characterization techniques, raman spectroscopy analysis technology and nano-mechanical pull-out method were used in the experiment. Molecular simulation method simulated the pull-out process of CNT from the polymer matrix by applying displacement and force to CNT. The effects of polymer matrix (including type, crystal structure and density) and CNT (including chirality, diameter and functional processing) on the interfacial bonding characteristics of CNT/polymer composites were summarized and the signi-ficant future research directions of this field were prospected.
2017, 34(1): 23-30.
doi: 10.13801/j.cnki.fhclxb.20160315.007
Abstract:
A novel flame retardant containing phosphorous 2-methyl-3-(10-oxo-10H-9-oxa-10λ5-phospha-phenan-thren-10-yl)-propionic acid 2-hydroxy-ethyl ester(DOPOHM) was synthesized by 9-oxa-10-phospha-phenanthr ene 10-oxide(DOPO) and hydroxyethyl methacrylate (HEMA), and the flame retardant materials (ZnB-DOPOHM/AR) via were prepared via DOPOHM and various of ZnB adding into acrylate resin(AR). The thermal stability and flame retardant level of composites was characterized by TGA and LOI test. The synergies mechanism between DOPOHM and ZnB was studied by SEM, XPS and EDS. The degradation activation energies(Ea) of composites were calculated by Horowitz-Metzger theory. The results indicate that the thermal stability and LOI of composites is improved by ZnB content increasing. Moreover, the char layer after combustion become more compact and smooth due to effects of both two additives. The synergies mechanism reveal that progress of catalysis effect of decomposed phosphine on matrix occur on the surface of ZnO and B2O3 produced by ZnB, which is verified by ZnO-P2O5 existence. The calculated results show that ZnO and B2O3 positive catalytic role and synergic phosphine-catalyzed reinforce capability of char produced.
A novel flame retardant containing phosphorous 2-methyl-3-(10-oxo-10H-9-oxa-10λ5-phospha-phenan-thren-10-yl)-propionic acid 2-hydroxy-ethyl ester(DOPOHM) was synthesized by 9-oxa-10-phospha-phenanthr ene 10-oxide(DOPO) and hydroxyethyl methacrylate (HEMA), and the flame retardant materials (ZnB-DOPOHM/AR) via were prepared via DOPOHM and various of ZnB adding into acrylate resin(AR). The thermal stability and flame retardant level of composites was characterized by TGA and LOI test. The synergies mechanism between DOPOHM and ZnB was studied by SEM, XPS and EDS. The degradation activation energies(Ea) of composites were calculated by Horowitz-Metzger theory. The results indicate that the thermal stability and LOI of composites is improved by ZnB content increasing. Moreover, the char layer after combustion become more compact and smooth due to effects of both two additives. The synergies mechanism reveal that progress of catalysis effect of decomposed phosphine on matrix occur on the surface of ZnO and B2O3 produced by ZnB, which is verified by ZnO-P2O5 existence. The calculated results show that ZnO and B2O3 positive catalytic role and synergic phosphine-catalyzed reinforce capability of char produced.
2017, 34(1): 31-39.
doi: 10.13801/j.cnki.fhclxb.20160315.008
Abstract:
The graphene was decorated by carbon nanotubes (MWCNTs) and zinc hydroxystannate(ZHS), respectively. The hybrid nanoparticles were used as the core, the surfactant KH560 as the corona and polyether amine M2070 as the canopy. The solvent-free (GNS-MWCNTs)@M2070 and solvent-free (GNS-ZHS)@M2070 nanofluids were prepared, respectively. Then both of them with mass fraction is 2.0 wt% were added into the epoxy resin(EP) to prepare (GNS-MWCNTs)@M2070/EP and (GNS-ZHS)@M2070/EP composites. The flame retardant property of the composites was characterized by the cone calorimeter test. The results show that the value of FIGRA index of pure EP, (GNS-MWCNTs)@M2070/EP and (GNS-ZHS)@M2070/EP are 3.682, 3.118 and 4.391 kW(m2·s)-1, respectively. Compared with (GNS-MWCNTs)@M2070/EP, (GNS-ZHS)@M2070/EP has a lower smoke productiom rate(SPR), total smoke production(TSR) and carbon monoxide production(COP), which confirms that the ZHS deposited on the graphene sheet layers solvent-free nanofluid can better improve the flame retardant property of the epoxy resin.
The graphene was decorated by carbon nanotubes (MWCNTs) and zinc hydroxystannate(ZHS), respectively. The hybrid nanoparticles were used as the core, the surfactant KH560 as the corona and polyether amine M2070 as the canopy. The solvent-free (GNS-MWCNTs)@M2070 and solvent-free (GNS-ZHS)@M2070 nanofluids were prepared, respectively. Then both of them with mass fraction is 2.0 wt% were added into the epoxy resin(EP) to prepare (GNS-MWCNTs)@M2070/EP and (GNS-ZHS)@M2070/EP composites. The flame retardant property of the composites was characterized by the cone calorimeter test. The results show that the value of FIGRA index of pure EP, (GNS-MWCNTs)@M2070/EP and (GNS-ZHS)@M2070/EP are 3.682, 3.118 and 4.391 kW(m2·s)-1, respectively. Compared with (GNS-MWCNTs)@M2070/EP, (GNS-ZHS)@M2070/EP has a lower smoke productiom rate(SPR), total smoke production(TSR) and carbon monoxide production(COP), which confirms that the ZHS deposited on the graphene sheet layers solvent-free nanofluid can better improve the flame retardant property of the epoxy resin.
2017, 34(1): 40-46.
doi: 10.13801/j.cnki.fhclxb.20160322.005
Abstract:
The silane grafting and crosslinking high density polyethylene (HDPE) filled with MgO was prepared by the method of two-step reaction-extrusion, in order to study the effects of the silane grafting and crosslinking on the crystallinity, the mechanical properties, the heat resistance, and the thermal conductivity of the MgO/HDPE composites. And the graft-crosslinking and the crystallization were characterized by FTIR and DSC, respectively. The results show that the tensile strength, the notched impact strength and the heat deflection temperature (HDT) of the MgO/HDPE composites increase from 20.41 MPa, 1.875 kJ/m2 and 74.6℃ without graft-crosslinking to 27.24 MPa, 7.875 kJ/m2 and 83.5℃ respectively after crosslinking, and the thermal conductivity of the crosslinking composites (0.447 W/(m·K)) is almost the same with the non-crosslinking ones.
The silane grafting and crosslinking high density polyethylene (HDPE) filled with MgO was prepared by the method of two-step reaction-extrusion, in order to study the effects of the silane grafting and crosslinking on the crystallinity, the mechanical properties, the heat resistance, and the thermal conductivity of the MgO/HDPE composites. And the graft-crosslinking and the crystallization were characterized by FTIR and DSC, respectively. The results show that the tensile strength, the notched impact strength and the heat deflection temperature (HDT) of the MgO/HDPE composites increase from 20.41 MPa, 1.875 kJ/m2 and 74.6℃ without graft-crosslinking to 27.24 MPa, 7.875 kJ/m2 and 83.5℃ respectively after crosslinking, and the thermal conductivity of the crosslinking composites (0.447 W/(m·K)) is almost the same with the non-crosslinking ones.
2017, 34(1): 47-52.
doi: 10.13801/j.cnki.fhclxb.20160322.006
Abstract:
Crochet process was specially applied to combine activated carbon fibers (ACF) with glass fibers (GF) to improve the designability and complexity of frequency selective surface (FSS), ACF crochet structure circuit screen carbon fibers/epoxy(ACF/EP) composites were prepared. The effect of different knitted structure and ACF mass fraction to microwave absorbing performance of composites was discussed. The results show that the maximum reflection loss (RL) of both 4-needle-date-shaped FSS CF/EP composites with 100% CF and 16-needle-date-shaped FSS composites with 50% CF are higher than -50 dB, in addition, the effective absorption bandwidth (RL<-10 dB) could reach to 10 GHz. With complex crochet design, the porous structure of CF/EP composites increase, effective absorption bandwidth(RL<-10 dB) broaden, and 4-needle-date-shaped structure with more irregular aperture has excellent microwave absorbing property. Ideal CF/EP microwave absorbing composites will be obtained by combining the suitable mass fraction of chopped CF and knitted structure.
Crochet process was specially applied to combine activated carbon fibers (ACF) with glass fibers (GF) to improve the designability and complexity of frequency selective surface (FSS), ACF crochet structure circuit screen carbon fibers/epoxy(ACF/EP) composites were prepared. The effect of different knitted structure and ACF mass fraction to microwave absorbing performance of composites was discussed. The results show that the maximum reflection loss (RL) of both 4-needle-date-shaped FSS CF/EP composites with 100% CF and 16-needle-date-shaped FSS composites with 50% CF are higher than -50 dB, in addition, the effective absorption bandwidth (RL<-10 dB) could reach to 10 GHz. With complex crochet design, the porous structure of CF/EP composites increase, effective absorption bandwidth(RL<-10 dB) broaden, and 4-needle-date-shaped structure with more irregular aperture has excellent microwave absorbing property. Ideal CF/EP microwave absorbing composites will be obtained by combining the suitable mass fraction of chopped CF and knitted structure.
2017, 34(1): 53-59.
doi: 10.13801/j.cnki.fhclxb.20160411.003
Abstract:
The poor heat resistance of silicone rubber seriously restricts its application in the field of high temperature resistance. To solve this problem, low melting oxide Sb2O3 and Bi2O3 were used as fluxing agent to study the effects on the ceramizable properties of diatomite/silicone rubber composites. The thermal stability of Sb2O3 and Bi2O3 on diatomite/silicone rubber composites was analyzed by TG, the bending strength after pyrolysis was tested by universal mechanical testing apparatus, field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS) were used to analyze the microstructure and composition of the pyrolysis products, and ceramic mechanism was studied by XRD. The results show that metal oxide of Sb2O3 and Bi2O3 can accelerate the decomposition of silicone rubber, but they can obviously improve the bending strength of the specimen after pyrolysis. Bi2O3 and Sb2O3 are contribute to the formation of a continuous bridge structure in the process of composites pyrolysis by FESEM. Through EDS analysis, eutectic phenomenon may be occurring between SiO2 and Sb2O3, Bi2O3 and SiO2 in the process of composites pyrolysis and help to form a ceramic structure. XRD show that the amorphous phase structure is formed after the addition of fluxing agent to diatomite/silicone rubber composite, which can improve the strength of the ceramics.
The poor heat resistance of silicone rubber seriously restricts its application in the field of high temperature resistance. To solve this problem, low melting oxide Sb2O3 and Bi2O3 were used as fluxing agent to study the effects on the ceramizable properties of diatomite/silicone rubber composites. The thermal stability of Sb2O3 and Bi2O3 on diatomite/silicone rubber composites was analyzed by TG, the bending strength after pyrolysis was tested by universal mechanical testing apparatus, field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS) were used to analyze the microstructure and composition of the pyrolysis products, and ceramic mechanism was studied by XRD. The results show that metal oxide of Sb2O3 and Bi2O3 can accelerate the decomposition of silicone rubber, but they can obviously improve the bending strength of the specimen after pyrolysis. Bi2O3 and Sb2O3 are contribute to the formation of a continuous bridge structure in the process of composites pyrolysis by FESEM. Through EDS analysis, eutectic phenomenon may be occurring between SiO2 and Sb2O3, Bi2O3 and SiO2 in the process of composites pyrolysis and help to form a ceramic structure. XRD show that the amorphous phase structure is formed after the addition of fluxing agent to diatomite/silicone rubber composite, which can improve the strength of the ceramics.
2017, 34(1): 60-66.
doi: 10.13801/j.cnki.fhclxb.20160411.004
Abstract:
MgO-Al2O3-SiO2/boron phenolic (MAS/BPF) ceramifiable composites, based on ceramifiable fillers of nano MgO, Al2O3 and SiO2(MAS) modified matrix boron phenolic resin(BPF), were prepared with fusing agent of B2O3, Bi2O3 or glass frits by hot compression molding. The effects of fusing agent on the thermal stability, microstructure and phase-transition of MAS/BPF ceramifiable composites were studied. The results show that the dimensional shrinkage rate varies from 9% to 14.5% after pyrolysed at 600-1 000℃ for 2 h, indicating a great dimensional stability. And TG analysis reveals that the fusing ageing reduces the char yields of MAS/BPF ceramifiable composites at 1 200℃, but leading to a higher thermal stability at 900-1 200℃. XRD and SEM manifest ceramic reaction occurs at lower temperature with the addition of fusing agent. Compared with B2O3 and Bi2O3, glass frits contribute to forming a large amount of liquid phase structure, which promotes the reaction between the porous carbon from the decomposed resin matrix and ceramifiable fillers, improving the density and dimensional stability at high temperatures of MAS/BPF ceramifiable composites.
MgO-Al2O3-SiO2/boron phenolic (MAS/BPF) ceramifiable composites, based on ceramifiable fillers of nano MgO, Al2O3 and SiO2(MAS) modified matrix boron phenolic resin(BPF), were prepared with fusing agent of B2O3, Bi2O3 or glass frits by hot compression molding. The effects of fusing agent on the thermal stability, microstructure and phase-transition of MAS/BPF ceramifiable composites were studied. The results show that the dimensional shrinkage rate varies from 9% to 14.5% after pyrolysed at 600-1 000℃ for 2 h, indicating a great dimensional stability. And TG analysis reveals that the fusing ageing reduces the char yields of MAS/BPF ceramifiable composites at 1 200℃, but leading to a higher thermal stability at 900-1 200℃. XRD and SEM manifest ceramic reaction occurs at lower temperature with the addition of fusing agent. Compared with B2O3 and Bi2O3, glass frits contribute to forming a large amount of liquid phase structure, which promotes the reaction between the porous carbon from the decomposed resin matrix and ceramifiable fillers, improving the density and dimensional stability at high temperatures of MAS/BPF ceramifiable composites.
2017, 34(1): 67-74.
doi: 10.13801/j.cnki.fhclxb.20160401.002
Abstract:
Using the process technology of precipitated silica, under the same condition, different mass fractions of hydroxy carboxylic ester were added into precursors as modifier in order to wet modification, the mechanical properties, dynamic properties and dynamic heat generation properties of silica/nature rubber (NR) composites were investigated. The results show that the silica prepared is amorphous silica, the dispersion of silica modified by the mass fraction of 6% of hydroxy carboxylic ester is good, particles are distributed evenly, which shapes like a ball, and some hydrophilic groups of silica are eliminated effectively by using hydroxy carboxylic esters, therefore, the dispersity of silica in NR is improved. When the amounts of silica increase, the mechanical property, loss factor and dynamic heat generation of the composites are enhanced, meanwhile, the Payne effects are also increased. By the time the content of silica reaches its critical value (the mass ratio of silica to NR is 40:100), the mechanical properties of silica/NR composites would have better performance, the properties of modified silica/NR composites is better than unmodified silica/NR composites, as results of the hardness and tensile strength and elongation at break are increased, the wear volume and dynamic heat generation are decreased. Dynamic mechanical performance test shows that when the mass ratio of modified silica to NR is 40:100, the rolling resistance of modified silica/NR composites loss factor at 0℃ keep almost constant, but the skid resistance of composites loss factor at 60℃ drops from 0.123 to 0.104. The results of SEM prove that better dispersion and stronger interfacial interaction are achieved in NR matrix filled by modified silica than unmodified silica.
Using the process technology of precipitated silica, under the same condition, different mass fractions of hydroxy carboxylic ester were added into precursors as modifier in order to wet modification, the mechanical properties, dynamic properties and dynamic heat generation properties of silica/nature rubber (NR) composites were investigated. The results show that the silica prepared is amorphous silica, the dispersion of silica modified by the mass fraction of 6% of hydroxy carboxylic ester is good, particles are distributed evenly, which shapes like a ball, and some hydrophilic groups of silica are eliminated effectively by using hydroxy carboxylic esters, therefore, the dispersity of silica in NR is improved. When the amounts of silica increase, the mechanical property, loss factor and dynamic heat generation of the composites are enhanced, meanwhile, the Payne effects are also increased. By the time the content of silica reaches its critical value (the mass ratio of silica to NR is 40:100), the mechanical properties of silica/NR composites would have better performance, the properties of modified silica/NR composites is better than unmodified silica/NR composites, as results of the hardness and tensile strength and elongation at break are increased, the wear volume and dynamic heat generation are decreased. Dynamic mechanical performance test shows that when the mass ratio of modified silica to NR is 40:100, the rolling resistance of modified silica/NR composites loss factor at 0℃ keep almost constant, but the skid resistance of composites loss factor at 60℃ drops from 0.123 to 0.104. The results of SEM prove that better dispersion and stronger interfacial interaction are achieved in NR matrix filled by modified silica than unmodified silica.
2017, 34(1): 75-82.
doi: 10.13801/j.cnki.fhclxb.20160328.005
Abstract:
Failure modes of composite sandwich column with pyramidal truss core containing a hole were studied through experiments aimed to study the failure mode and influencing factors of composite lattice sandwich structure with a hole under compression loads. Finite element analysis progressive damage failure mode of composite lattice sandwich structure with a hole was established based on 3D Hashin criterion and Chang-Chang stiffness degradation criterion, and the calculated results were compared with experimental ones. Based on the finite element method, the impact of the opening shape, ratio and position on its ultimate loading capacity was discussed. The result shows that when the face-sheet of lattice sandwich structure containing a hole is thinker, the main failure mode is face crushing. By contrast the results of finite element calculation and experimental ones, the maximum error of the ultimate loading capacity is about 12%, and failure position is consistent with the experimental results. When the center of the hole is in the symmetry plane parallel to the direction of the load, the compressive strength of the lattice sandwich structure has nothing to do with the opening position, mainly influenced by the opening shape and ratio. When the center of hole is in the symmetry plane perpendicular to the direction of the load, if the margin is larger than one cell size, the compression strength of the lattice sandwich structure substantially does't change, otherwise the compression strength decreases.
Failure modes of composite sandwich column with pyramidal truss core containing a hole were studied through experiments aimed to study the failure mode and influencing factors of composite lattice sandwich structure with a hole under compression loads. Finite element analysis progressive damage failure mode of composite lattice sandwich structure with a hole was established based on 3D Hashin criterion and Chang-Chang stiffness degradation criterion, and the calculated results were compared with experimental ones. Based on the finite element method, the impact of the opening shape, ratio and position on its ultimate loading capacity was discussed. The result shows that when the face-sheet of lattice sandwich structure containing a hole is thinker, the main failure mode is face crushing. By contrast the results of finite element calculation and experimental ones, the maximum error of the ultimate loading capacity is about 12%, and failure position is consistent with the experimental results. When the center of the hole is in the symmetry plane parallel to the direction of the load, the compressive strength of the lattice sandwich structure has nothing to do with the opening position, mainly influenced by the opening shape and ratio. When the center of hole is in the symmetry plane perpendicular to the direction of the load, if the margin is larger than one cell size, the compression strength of the lattice sandwich structure substantially does't change, otherwise the compression strength decreases.
2017, 34(1): 83-90.
doi: 10.13801/j.cnki.fhclxb.20160328.004
Abstract:
For the sake of predicting residual strength of composite laminate with lightning strike thermal-mechanical coupling damage, stiffness matrix progressive damage degradation model was constructed to characterize composite lightning strike thermal-mechanical coupling damage based on continuum damage mechanics (CDM) method and phenomenological analysis method. An three dimensional model of composite laminate structure with lightning strike thermal-mechanical coupling damage was established based on progressive damage model and ABAQUS finite element simulation software. Combined with UMAT subroutine, residual strength prediction was accomplished under tensile load. The results show that excellent agreement between test data and numerical results is observed. The model constructed in this paper is capable to predict the tensile residual strength of composite laminate with lightning strike thermal-mechanical coupling damage.
For the sake of predicting residual strength of composite laminate with lightning strike thermal-mechanical coupling damage, stiffness matrix progressive damage degradation model was constructed to characterize composite lightning strike thermal-mechanical coupling damage based on continuum damage mechanics (CDM) method and phenomenological analysis method. An three dimensional model of composite laminate structure with lightning strike thermal-mechanical coupling damage was established based on progressive damage model and ABAQUS finite element simulation software. Combined with UMAT subroutine, residual strength prediction was accomplished under tensile load. The results show that excellent agreement between test data and numerical results is observed. The model constructed in this paper is capable to predict the tensile residual strength of composite laminate with lightning strike thermal-mechanical coupling damage.
2017, 34(1): 91-95.
doi: 10.13801/j.cnki.fhclxb.20160330.001
Abstract:
50D hollow polyester filaments were used to be embedded the composite materials simulating the porosity of the composites, which was used as standard test blocks. Carbon fiber reinforced epoxy resin composites were prepared with three kinds of thicknesses(1.5, 3.0 and 5.0 mm) and five kinds of void contents (0-5.76%). Ultrasonic C-scan was adopted to measure the ultrasonic attenuation of the composites with different void contents. Testing results were compared with the results using Boeing Co.'s standard test block. The effect of arrangement density and position of polyester filament on ultrasonic attenuation of the composites were studied. The results show that there is a good consistency between the standard test block made in this paper and Boeing Co. standard test block, and using hollow polyester filament is feasible to simulate the porosity of composites. The void content and ultrasonic attenuation increase with the arrangement density. The ultrasonic attenuation keeps stable when the position of polyester filament in thickness direction changes.
50D hollow polyester filaments were used to be embedded the composite materials simulating the porosity of the composites, which was used as standard test blocks. Carbon fiber reinforced epoxy resin composites were prepared with three kinds of thicknesses(1.5, 3.0 and 5.0 mm) and five kinds of void contents (0-5.76%). Ultrasonic C-scan was adopted to measure the ultrasonic attenuation of the composites with different void contents. Testing results were compared with the results using Boeing Co.'s standard test block. The effect of arrangement density and position of polyester filament on ultrasonic attenuation of the composites were studied. The results show that there is a good consistency between the standard test block made in this paper and Boeing Co. standard test block, and using hollow polyester filament is feasible to simulate the porosity of composites. The void content and ultrasonic attenuation increase with the arrangement density. The ultrasonic attenuation keeps stable when the position of polyester filament in thickness direction changes.
2017, 34(1): 96-103.
doi: 10.13801/j.cnki.fhclxb.20160405.001
Abstract:
The problem of stability for wing surface structure made of composite stiffened panels was studied, and stability safety margin of stiffened panels under compression and shear loads was analyzed. A method of calculating buckling and post-buckling loading capacity of composite stiffened panels was presented and used to check the structural stability under complex loading conditions. The object for check is an optimized wing made of composites which satisfies the requirement of strength, stiffness and manufacture process. The internal force distribution of the wing under various load cases was obtained by MSC.NASTRAN, and the stability loading capacity of each skin block was acquired by the method proposed in this paper. Then the buckling and post-buckling safety margin calculation principles for composite laminated plates under complex loading were given to verify whether the stiffened panels of the optimized wing meet the stability design requirements. This method can be integrated into a structure optimization platform as a constraint.
The problem of stability for wing surface structure made of composite stiffened panels was studied, and stability safety margin of stiffened panels under compression and shear loads was analyzed. A method of calculating buckling and post-buckling loading capacity of composite stiffened panels was presented and used to check the structural stability under complex loading conditions. The object for check is an optimized wing made of composites which satisfies the requirement of strength, stiffness and manufacture process. The internal force distribution of the wing under various load cases was obtained by MSC.NASTRAN, and the stability loading capacity of each skin block was acquired by the method proposed in this paper. Then the buckling and post-buckling safety margin calculation principles for composite laminated plates under complex loading were given to verify whether the stiffened panels of the optimized wing meet the stability design requirements. This method can be integrated into a structure optimization platform as a constraint.
2017, 34(1): 104-111.
doi: 10.13801/j.cnki.fhclxb.20160407.001
Abstract:
In order to analyze the damage characteristics of mechanical fastened composite laminates subjected to lightning strike, mathematical analysis model of the ablation damage of composite laminate structure with fastener was constructed based on the principle of energy balance. According to the model, an effective three dimensional thermal-electrical coupling analysis finite element model of composite laminate structure with fastener subjected to lightning current has been established based on ABAQUS, and lightning strike ablation damage under different potential boundary conditions was analyzed. Analysis results indicate that:lightning current could pass through the thickness direction of the laminate due to the existence of the metal fastener, then distribute to all layers, and finally conducted in in-plane of layer, conductive ability of different layup orientations was dependent on the potential gradient direction and electrical conductivity along the potential gradient direction; different potential boundary conditions was corresponding to different potential distribution in layers, resulting in conductive ability of different layup orientations was changed, and then caused different lightning strike ablation damage distribution. According to the investigation in this paper, the lightning strike ablation damage characteristic of composite laminate with fastener can be qualitatively recognized.
In order to analyze the damage characteristics of mechanical fastened composite laminates subjected to lightning strike, mathematical analysis model of the ablation damage of composite laminate structure with fastener was constructed based on the principle of energy balance. According to the model, an effective three dimensional thermal-electrical coupling analysis finite element model of composite laminate structure with fastener subjected to lightning current has been established based on ABAQUS, and lightning strike ablation damage under different potential boundary conditions was analyzed. Analysis results indicate that:lightning current could pass through the thickness direction of the laminate due to the existence of the metal fastener, then distribute to all layers, and finally conducted in in-plane of layer, conductive ability of different layup orientations was dependent on the potential gradient direction and electrical conductivity along the potential gradient direction; different potential boundary conditions was corresponding to different potential distribution in layers, resulting in conductive ability of different layup orientations was changed, and then caused different lightning strike ablation damage distribution. According to the investigation in this paper, the lightning strike ablation damage characteristic of composite laminate with fastener can be qualitatively recognized.
2017, 34(1): 112-120.
doi: 10.13801/j.cnki.fhclxb.20160411.002
Abstract:
A micro-model of thermal resistance change with fiber breakage was developed to describe the correlation between the thermal resistance change and the fiber damage in unidirectional fibers reinforced composites, and a qualitative analysis of the thermal resistance change was carried out based on the present model. Heat transfers in longitudinal and thickness directions of the composite were both analyzed. Analytical solutions were derived for the thermal resistance change in both longitudinal and thickness directions of the composite by the standard Weibull model in combination with the failure length of fibers as the minimum length of the fiber segments. The process of fiber break under applied tensile stress was simulated with Monte-Carlo random method, during which the thermal resistance change in the composite was calculated simultaneously. The results of the present study show that the thermal resistance changes in both the longitudinal and thickness directions increase linearly with the number of fiber breakage in the composite. For larger fiber volume fraction, the thermal resistance changes more greatly. The thermal resistance change in longitudinal direction of the composite increases greatly by the fiber/matrix thermal conductivity ratio β, but the increase amplitude reduces gradually while the fiber/matrix thermal conductivity ratio greater than 10 (i.e. β>10). However, the thermal resistance change in thickness direction increases dramatically from the beginning and then decreases with the increase of the fiber/matrix thermal conductivity ratio β, and the maximum value of the thermal resistance change occurs for the fiber thermal conductivity close to that of the matrix (i.e. around β=1).
A micro-model of thermal resistance change with fiber breakage was developed to describe the correlation between the thermal resistance change and the fiber damage in unidirectional fibers reinforced composites, and a qualitative analysis of the thermal resistance change was carried out based on the present model. Heat transfers in longitudinal and thickness directions of the composite were both analyzed. Analytical solutions were derived for the thermal resistance change in both longitudinal and thickness directions of the composite by the standard Weibull model in combination with the failure length of fibers as the minimum length of the fiber segments. The process of fiber break under applied tensile stress was simulated with Monte-Carlo random method, during which the thermal resistance change in the composite was calculated simultaneously. The results of the present study show that the thermal resistance changes in both the longitudinal and thickness directions increase linearly with the number of fiber breakage in the composite. For larger fiber volume fraction, the thermal resistance changes more greatly. The thermal resistance change in longitudinal direction of the composite increases greatly by the fiber/matrix thermal conductivity ratio β, but the increase amplitude reduces gradually while the fiber/matrix thermal conductivity ratio greater than 10 (i.e. β>10). However, the thermal resistance change in thickness direction increases dramatically from the beginning and then decreases with the increase of the fiber/matrix thermal conductivity ratio β, and the maximum value of the thermal resistance change occurs for the fiber thermal conductivity close to that of the matrix (i.e. around β=1).
2017, 34(1): 121-128.
doi: 10.13801/j.cnki.fhclxb.20160317.003
Abstract:
The plant polyphenol was modified by amine methylation, and then coated onto Fe3O4 surface to obtain the functional Fe3O4@amine-methylated plant polyphenol (Fe3O4@A-PP) for harvesting the oleagious microalgae-Chlorella vulgaris. FTIR, magnetic hysteresis loop, and zeta potential of Fe3O4@A-PP were detected to investigate its physicochemical properties. The effects of dosing mode of Fe3O4@A-PP and the ratio of Fe3O4 to A-PP on harvesting efficiency were also studied. FTIR indicates that Fe3O4@A-PP has the functional groups of C-H, N-H, and -OH from A-PP. The coating of A-PP onto the Fe3O4 surface don't interfere the magnetic property of Fe3O4. Compared with A-PP, the zeta potential of Fe3O4@A-PP is improved by 5-10 mV. The ratio of Fe3O4 (g/L) to A-PP (mg/L) in Fe3O4@A-PP influences the harvesting efficiency obviously and the highest efficiency of 84.2% is achieved at 20/200. Fe3O4@A-PP can shorten the harvesting time from 30 min of A-PP to less than 0.5 min. The microscope images show that the microalgae cells are wrapped by Fe3O4@A-PP and form the cluster matrix or adhere around the Fe3O4, unlike the flaky and loose flocs or aggregates after A-PP flocculation. The mechanism of charge neutralization in the Fe3O4@A-PP magnetic flocculation plays an important role in microalgal harvesting.
The plant polyphenol was modified by amine methylation, and then coated onto Fe3O4 surface to obtain the functional Fe3O4@amine-methylated plant polyphenol (Fe3O4@A-PP) for harvesting the oleagious microalgae-Chlorella vulgaris. FTIR, magnetic hysteresis loop, and zeta potential of Fe3O4@A-PP were detected to investigate its physicochemical properties. The effects of dosing mode of Fe3O4@A-PP and the ratio of Fe3O4 to A-PP on harvesting efficiency were also studied. FTIR indicates that Fe3O4@A-PP has the functional groups of C-H, N-H, and -OH from A-PP. The coating of A-PP onto the Fe3O4 surface don't interfere the magnetic property of Fe3O4. Compared with A-PP, the zeta potential of Fe3O4@A-PP is improved by 5-10 mV. The ratio of Fe3O4 (g/L) to A-PP (mg/L) in Fe3O4@A-PP influences the harvesting efficiency obviously and the highest efficiency of 84.2% is achieved at 20/200. Fe3O4@A-PP can shorten the harvesting time from 30 min of A-PP to less than 0.5 min. The microscope images show that the microalgae cells are wrapped by Fe3O4@A-PP and form the cluster matrix or adhere around the Fe3O4, unlike the flaky and loose flocs or aggregates after A-PP flocculation. The mechanism of charge neutralization in the Fe3O4@A-PP magnetic flocculation plays an important role in microalgal harvesting.
2017, 34(1): 129-134.
doi: 10.13801/j.cnki.fhclxb.20160329.001
Abstract:
The chemical etching technique was applied to prepare surface texture of SiC/Al composites. The microtopography characteristics and wetting behaviors of the etched surfaces as well as their dependencies on etching time were analyzed by SEM and a contact angle meter. The temperature shock resistance of the SiC/Al superhydrophobic surfaces were evaluated by thermal shock tests. The results indicate that SiC/Al composite can be easily etched chemically to form distinct hierarchical structures integrating particle-shaped microstructures and nano-sized pit structures mainly due to the existence of SiC microparticles served as the bodies of microstructure, the etched surfaces modified by fluorosilane coating show excellent superhydrophobicity with a water contact angle of up to 166.8° and a small slide angle of as low as 3°, the SiC/Al superhydrophobic surfaces possess a favorable temperature shock resistance.
The chemical etching technique was applied to prepare surface texture of SiC/Al composites. The microtopography characteristics and wetting behaviors of the etched surfaces as well as their dependencies on etching time were analyzed by SEM and a contact angle meter. The temperature shock resistance of the SiC/Al superhydrophobic surfaces were evaluated by thermal shock tests. The results indicate that SiC/Al composite can be easily etched chemically to form distinct hierarchical structures integrating particle-shaped microstructures and nano-sized pit structures mainly due to the existence of SiC microparticles served as the bodies of microstructure, the etched surfaces modified by fluorosilane coating show excellent superhydrophobicity with a water contact angle of up to 166.8° and a small slide angle of as low as 3°, the SiC/Al superhydrophobic surfaces possess a favorable temperature shock resistance.
2017, 34(1): 135-141.
doi: 10.13801/j.cnki.fhclxb.20160407.002
Abstract:
TiC/Ti6Al4V composites were fabricated by microwave sintering. The isothermal oxidation behaviors of the TiC/Ti6Al4V composites were investigated in air under the temperature of 550, 650 and 750℃. Moreover, the surface and cross-sectional morphologies and phase composition of the oxidation film were investigated. The results show that the TiC/Ti6Al4V composites are composed of TiC, α-Ti+β-Ti phases. With increase of the oxidation temperature, the oxidation rule curves change from parabola into line. The oxidation products of the composites mainly consist of TiO2 as the oxidation temperature lower than 650℃. While the oxidation temperature is high up to 750℃, the oxidation coatings are composed of three layers, containing thin outer TiO2, intermediate Al2O3 and TiO2 and inner TiO2. With the TiC content increases, the oxygen activation energy increases, the particle size of oxide decreases and the oxidation resistance of TiC/Ti6Al4V composites improves.
TiC/Ti6Al4V composites were fabricated by microwave sintering. The isothermal oxidation behaviors of the TiC/Ti6Al4V composites were investigated in air under the temperature of 550, 650 and 750℃. Moreover, the surface and cross-sectional morphologies and phase composition of the oxidation film were investigated. The results show that the TiC/Ti6Al4V composites are composed of TiC, α-Ti+β-Ti phases. With increase of the oxidation temperature, the oxidation rule curves change from parabola into line. The oxidation products of the composites mainly consist of TiO2 as the oxidation temperature lower than 650℃. While the oxidation temperature is high up to 750℃, the oxidation coatings are composed of three layers, containing thin outer TiO2, intermediate Al2O3 and TiO2 and inner TiO2. With the TiC content increases, the oxygen activation energy increases, the particle size of oxide decreases and the oxidation resistance of TiC/Ti6Al4V composites improves.
2017, 34(1): 142-151.
doi: 10.13801/j.cnki.fhclxb.20160329.002
Abstract:
Aiming at the problem of poor high-temperature wear resistance of safety clamp wedge used in ultra-high speed elevator, the experiments of laser cladding to prepare VC-Fe3C/Fe-Ni composite coating were made. FeV powder, graphite powder and Ni powder were used as cladding material. The evolution rule of microstructure at different mass ratios and process parameters was analyzed. The properties of composite coating such as hardness, high temperature wear resistance and impact toughness were tested. The research results show that the composite coating is made up of VC, Fe-Ni solid solution and Fe3C by in-situ reaction. The content of VC increases with the adding of graphite content. At low scanning speed, the morphology of VC is presented as ball-like and cellular-like. Most VC particles are equably distributed in Fe-Ni solid solution. At high scanning speed, the morphology of VC is presented as chrysanthemum-like, dendrite-like and bulk-like. Most VC particles are distributed along grain boundary. At the mass ratio of 8:3:8 for FeV powder, graphite powder and Ni powder, the overlapping zone has no crack. The average hardness of composite coating is 5.9 GPa. The high-temperature wear loss of VC-Fe3C/Fe-Ni coating is 25% that of Ni60 laser cladding coating and 9.7% that of 45 steel. The impact toughness value of VC-Fe3C/Fe-Ni coating increases 37.6% than that of Ni60 laser cladding coating. Using this technology to the surface strengthening of elevator parts such as safety clamp wedge, the wear resistance and service life can be greatly improved.
Aiming at the problem of poor high-temperature wear resistance of safety clamp wedge used in ultra-high speed elevator, the experiments of laser cladding to prepare VC-Fe3C/Fe-Ni composite coating were made. FeV powder, graphite powder and Ni powder were used as cladding material. The evolution rule of microstructure at different mass ratios and process parameters was analyzed. The properties of composite coating such as hardness, high temperature wear resistance and impact toughness were tested. The research results show that the composite coating is made up of VC, Fe-Ni solid solution and Fe3C by in-situ reaction. The content of VC increases with the adding of graphite content. At low scanning speed, the morphology of VC is presented as ball-like and cellular-like. Most VC particles are equably distributed in Fe-Ni solid solution. At high scanning speed, the morphology of VC is presented as chrysanthemum-like, dendrite-like and bulk-like. Most VC particles are distributed along grain boundary. At the mass ratio of 8:3:8 for FeV powder, graphite powder and Ni powder, the overlapping zone has no crack. The average hardness of composite coating is 5.9 GPa. The high-temperature wear loss of VC-Fe3C/Fe-Ni coating is 25% that of Ni60 laser cladding coating and 9.7% that of 45 steel. The impact toughness value of VC-Fe3C/Fe-Ni coating increases 37.6% than that of Ni60 laser cladding coating. Using this technology to the surface strengthening of elevator parts such as safety clamp wedge, the wear resistance and service life can be greatly improved.
2017, 34(1): 152-159.
doi: 10.13801/j.cnki.fhclxb.20160422.001
Abstract:
In order to improve the anti-ablation property of carbon/carbon(C/C) composites, ZrC-Cu-C/C composites were fabricated by reactive melt infiltration using C/C composites with the porosity of 38% as preforms and Zr-Cu mixed powders as reactive infiltrators. The effect of infiltrator composition on the ablation resistance of ZrC-Cu-C/C composites was investigated by the test of oxyacetylene flame ablation, and the phase composition and microstructure of the ZrC-Cu-C/C composites before and after ablation were analyzed by XRD, SEM and EDS. The results show that the composites are composed of C, ZrC, Cu and residual Zr before ablation, while there exist C matrix, ZrO2, CuO and Cu2O as well as remnant ZrC and Cu in the surface after ablation for 20 s. Both the linear recession rate and mass loss rate of the composites decrease first and then increase with increasing the content of Zr in infiltrators. The ZrC-Cu-C/C composite fabricated with 60% Zr-Cu(mass fraction) exhibits the best anti-ablation property, whose linear recession rate and mass loss rate are 0.001 8 mm·s-1 and 0.001 3 g·s-1, respectively. The ablation mechanisms of the ZrC-Cu-C/C composite are the combination of thermo-physics ablation (based on sublimation of C, melt of ZrO2 and vaporization and sublimation of Cu), thermo-chemical ablation (oxidation of ZrC and C) and mechanical denudation (erosion of the flame).
In order to improve the anti-ablation property of carbon/carbon(C/C) composites, ZrC-Cu-C/C composites were fabricated by reactive melt infiltration using C/C composites with the porosity of 38% as preforms and Zr-Cu mixed powders as reactive infiltrators. The effect of infiltrator composition on the ablation resistance of ZrC-Cu-C/C composites was investigated by the test of oxyacetylene flame ablation, and the phase composition and microstructure of the ZrC-Cu-C/C composites before and after ablation were analyzed by XRD, SEM and EDS. The results show that the composites are composed of C, ZrC, Cu and residual Zr before ablation, while there exist C matrix, ZrO2, CuO and Cu2O as well as remnant ZrC and Cu in the surface after ablation for 20 s. Both the linear recession rate and mass loss rate of the composites decrease first and then increase with increasing the content of Zr in infiltrators. The ZrC-Cu-C/C composite fabricated with 60% Zr-Cu(mass fraction) exhibits the best anti-ablation property, whose linear recession rate and mass loss rate are 0.001 8 mm·s-1 and 0.001 3 g·s-1, respectively. The ablation mechanisms of the ZrC-Cu-C/C composite are the combination of thermo-physics ablation (based on sublimation of C, melt of ZrO2 and vaporization and sublimation of Cu), thermo-chemical ablation (oxidation of ZrC and C) and mechanical denudation (erosion of the flame).
2017, 34(1): 160-167.
doi: 10.13801/j.cnki.fhclxb.20160331.002
Abstract:
By using ANSYS/LS-DYNA software, the finite element(FE) model of cross-wedge rolling of laminated shafts was established. Some thickness-radius ratio rolling experiments were carried out under the orthogonal experimental designed with four factors and three levels. Through finite element simulation, the effect of process parameters including forming angle, spreading angle, area reduction and rolling temperature on thickness-radius ratio were analyzed. The results show that the rolling experimental results accord with the simulation results, which shows that finite element model can be used to predict thickness-radius ratio. With the increase of spreading angle, the thickness-radius ratio sharply decreases first and then slowly decreases. With the increase of temperature, the thickness-radius ratio strengthens first and then slowly strengthens. With the increase of area reduction, the thickness-radius ratio slowly strengthens first and then changes little. With the increase of forming angle, the thickness-radius ratio change is not obvious. The influencing sequence on the thickness-radius ratio is spreading angle, rolling temperature, area reduction and forming angle in turn. The research results contribute to control and design clad material thickness and matrix material radius size of laminated shaft.
By using ANSYS/LS-DYNA software, the finite element(FE) model of cross-wedge rolling of laminated shafts was established. Some thickness-radius ratio rolling experiments were carried out under the orthogonal experimental designed with four factors and three levels. Through finite element simulation, the effect of process parameters including forming angle, spreading angle, area reduction and rolling temperature on thickness-radius ratio were analyzed. The results show that the rolling experimental results accord with the simulation results, which shows that finite element model can be used to predict thickness-radius ratio. With the increase of spreading angle, the thickness-radius ratio sharply decreases first and then slowly decreases. With the increase of temperature, the thickness-radius ratio strengthens first and then slowly strengthens. With the increase of area reduction, the thickness-radius ratio slowly strengthens first and then changes little. With the increase of forming angle, the thickness-radius ratio change is not obvious. The influencing sequence on the thickness-radius ratio is spreading angle, rolling temperature, area reduction and forming angle in turn. The research results contribute to control and design clad material thickness and matrix material radius size of laminated shaft.
2017, 34(1): 168-174.
doi: 10.13801/j.cnki.fhclxb.20160331.001
Abstract:
To make sense of the crack growth rate distribution in graded material, a standard three-point bending fatigue test was performed on two groups of cracked graded titanium alloys TC11-TC4 and TA15-TA2. Test results show that the same components in different parts of graded structure shear an identical propagation property and the Paris formulas of the four kinds of 3D printing titanium alloy have been determined. The variation distribution of elastic modulus influences the stress intensity factor and inhibits the propagation of crack in the lower modulus side. During influence thickness of transition layer, propagation rate is between that of the two components and varies continuously, proving that gradient is able to eliminate the interface effect in the connection of dissimilar materials. A mixing law based on volume rate has been proposed to describe the distribution of crack propagation rate. In the test under constant periodic load, there was a remarkable difference in the propagation life of specimens only propagated along different directions. It means damage tolerance in graded structures can be improved with a reasonable arrangement of the gradient. The variation distribution of modulus and fatigue property both influence the propagation lives.
To make sense of the crack growth rate distribution in graded material, a standard three-point bending fatigue test was performed on two groups of cracked graded titanium alloys TC11-TC4 and TA15-TA2. Test results show that the same components in different parts of graded structure shear an identical propagation property and the Paris formulas of the four kinds of 3D printing titanium alloy have been determined. The variation distribution of elastic modulus influences the stress intensity factor and inhibits the propagation of crack in the lower modulus side. During influence thickness of transition layer, propagation rate is between that of the two components and varies continuously, proving that gradient is able to eliminate the interface effect in the connection of dissimilar materials. A mixing law based on volume rate has been proposed to describe the distribution of crack propagation rate. In the test under constant periodic load, there was a remarkable difference in the propagation life of specimens only propagated along different directions. It means damage tolerance in graded structures can be improved with a reasonable arrangement of the gradient. The variation distribution of modulus and fatigue property both influence the propagation lives.
2017, 34(1): 175-182.
doi: 10.13801/j.cnki.fhclxb.20160411.006
Abstract:
In order to improve the precision of inhomogeneous material interface crack tip fracture parameters which based on the inhomogeneous material interface fracture mechanics, Cell-Based smoothed finite element method(Cell-SFEM) and inhomogeneous material interaction integral, the Cell-Based smoothed finite element method was put forward to work out the inhomogeneous materials interface crack tip fracture parameters, and the interaction integral of inhomogeneous material based on Cell-Based smoothed finite element method was deduced. The normalized stress intensity factor in inhomogeneous material interface crack tip was solved. Compared with the reference solution, the relationship between the sizes of interaction integral region, the number of smoothing element and normalized stress intensity factor was discussed. The results of numerical example show that this method has high computational accuracy. It is not sensitive to integral area size as its features, and it can provide the basis for design and manufacture anti-failure of inhomogeneous material.
In order to improve the precision of inhomogeneous material interface crack tip fracture parameters which based on the inhomogeneous material interface fracture mechanics, Cell-Based smoothed finite element method(Cell-SFEM) and inhomogeneous material interaction integral, the Cell-Based smoothed finite element method was put forward to work out the inhomogeneous materials interface crack tip fracture parameters, and the interaction integral of inhomogeneous material based on Cell-Based smoothed finite element method was deduced. The normalized stress intensity factor in inhomogeneous material interface crack tip was solved. Compared with the reference solution, the relationship between the sizes of interaction integral region, the number of smoothing element and normalized stress intensity factor was discussed. The results of numerical example show that this method has high computational accuracy. It is not sensitive to integral area size as its features, and it can provide the basis for design and manufacture anti-failure of inhomogeneous material.
2017, 34(1): 183-190.
doi: 10.13801/j.cnki.fhclxb.20160308.001
Abstract:
Fe(Ⅱ)-Al layered double hydroxides (Fe-Al LDHs) were prepared by the ultrasound-assisted co-precipitation method and used for the adsorption of uranium (Ⅵ) from aqueous solution. The effects of initial pH, adsorbent dosage, temperature, adsorption time and initial U(Ⅵ) ions concentration on adsorption of U(Ⅵ) were investigated. The prepared composites were characterized by SEM, FTIR, XRD and X-ray photoelectron spectroscopy (XPS). The experiment results indicate that the maximum adsorption occur at pH of 6 and the adsorption reach equilibrium within 120 min. Meanwhile the removal rate is up to 99.98% for initial U(Ⅵ) concentration of 10 mg/L and adsorbent dosage of 1.0 g/L at 25℃, and the maximum adsorption capacity for U(Ⅵ) ions is 117.13 mg/g. The experimental data fit well with the Langmuir isotherm model and pseudo-second-order kinetic model(R2≈1), Adsorption of U(Ⅵ) on Fe(Ⅱ)-Al LDH is primarily due to spontaneous endothermic reaction. The results of SEM、FTIR and XPS show that the structure of Fe(Ⅱ)-Al LDH has no change, chemisorption plays a major role and redox take subsidiary function.
Fe(Ⅱ)-Al layered double hydroxides (Fe-Al LDHs) were prepared by the ultrasound-assisted co-precipitation method and used for the adsorption of uranium (Ⅵ) from aqueous solution. The effects of initial pH, adsorbent dosage, temperature, adsorption time and initial U(Ⅵ) ions concentration on adsorption of U(Ⅵ) were investigated. The prepared composites were characterized by SEM, FTIR, XRD and X-ray photoelectron spectroscopy (XPS). The experiment results indicate that the maximum adsorption occur at pH of 6 and the adsorption reach equilibrium within 120 min. Meanwhile the removal rate is up to 99.98% for initial U(Ⅵ) concentration of 10 mg/L and adsorbent dosage of 1.0 g/L at 25℃, and the maximum adsorption capacity for U(Ⅵ) ions is 117.13 mg/g. The experimental data fit well with the Langmuir isotherm model and pseudo-second-order kinetic model(R2≈1), Adsorption of U(Ⅵ) on Fe(Ⅱ)-Al LDH is primarily due to spontaneous endothermic reaction. The results of SEM、FTIR and XPS show that the structure of Fe(Ⅱ)-Al LDH has no change, chemisorption plays a major role and redox take subsidiary function.
2017, 34(1): 191-197.
doi: 10.13801/j.cnki.fhclxb.20160315.002
Abstract:
The N-dodecanol-polymethyl-metharylate(DA@PMMA) microcapsules were prepared by suspension polymerization method with n-dodecanol (DA) as core material and polymethyl-metharylate (PMMA) as outer shell. Microcapsules were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA), et al. The results show that the best conditions for preparation of DA@PMMA microcapsules are:Sodium salt of styrene-maleic anhydride polymer (SMA) content is 7.5% to DA, 2, 2-azobisisobutyronitrile (AIBN) content is 7.5% to methyl methacrylate (MMA), the core/shell mass ratio is 2:1, stirring speed is 1 000 r/min. DA@PMMA microcapsules are sphericalthe average particle size of DA@PMMA microcapsules is 26 μm. The mass fraction of DA in DA@PMMA microcapsules is nearly 66% and the latent heats of melting and freezing are found to be 137.6 J/g and 132.8 J/g. TGA and FIIR analyses also indicate that DA@PMMA microcapsules have good stability.
The N-dodecanol-polymethyl-metharylate(DA@PMMA) microcapsules were prepared by suspension polymerization method with n-dodecanol (DA) as core material and polymethyl-metharylate (PMMA) as outer shell. Microcapsules were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA), et al. The results show that the best conditions for preparation of DA@PMMA microcapsules are:Sodium salt of styrene-maleic anhydride polymer (SMA) content is 7.5% to DA, 2, 2-azobisisobutyronitrile (AIBN) content is 7.5% to methyl methacrylate (MMA), the core/shell mass ratio is 2:1, stirring speed is 1 000 r/min. DA@PMMA microcapsules are sphericalthe average particle size of DA@PMMA microcapsules is 26 μm. The mass fraction of DA in DA@PMMA microcapsules is nearly 66% and the latent heats of melting and freezing are found to be 137.6 J/g and 132.8 J/g. TGA and FIIR analyses also indicate that DA@PMMA microcapsules have good stability.
2017, 34(1): 198-202.
doi: 10.13801/j.cnki.fhclxb.20160322.002
Abstract:
Firstly, a theoretical method was employed to analyze the effect of the curvature of struts on the stiffness and strength properties of the open cell foam, based on the assumption that all the struts were curved. Then theoretical formulas were obtained for the prediction of the Young's modulus and yield strength of these foam containing curved struts. The validity of the theoretical prediction was verified by comparing with the simulation results of the finite element method. Finally, the finite element model was employed to investigate the effects of the content of curved struts, the curvature, and the anisotropy ratio on the compressive properties of the aluminum foam. The results indicate that the curvature of struts has a greater influence on the elastic modulus than the plastic collapse strength. The compressive properties of the aluminum foam show strong dependence on the curvature of struts, the content of curved struts, and the anisotropy ratio of cell structure.
Firstly, a theoretical method was employed to analyze the effect of the curvature of struts on the stiffness and strength properties of the open cell foam, based on the assumption that all the struts were curved. Then theoretical formulas were obtained for the prediction of the Young's modulus and yield strength of these foam containing curved struts. The validity of the theoretical prediction was verified by comparing with the simulation results of the finite element method. Finally, the finite element model was employed to investigate the effects of the content of curved struts, the curvature, and the anisotropy ratio on the compressive properties of the aluminum foam. The results indicate that the curvature of struts has a greater influence on the elastic modulus than the plastic collapse strength. The compressive properties of the aluminum foam show strong dependence on the curvature of struts, the content of curved struts, and the anisotropy ratio of cell structure.
2017, 34(1): 203-209.
doi: 10.13801/j.cnki.fhclxb.20160322.003
Abstract:
Hexadecanol-palmitic acid-lauric acid/SiO2 composite materials can be prepared by sol-gel method. The effect of absolute alcohol amount, deionized water amount and hexadecanol-palmitic acid-lauric acid amount on heat & moisture comprehensive property of hexadecanol-palmitic acid-lauric acid/SiO2 composites, and the preparation technology parameters for hexadecanol-palmitic acid-lauric acid/SiO2 composite materials was optimized. The results show that primary and secondary sequence of factors is the effect of absolute alcohol amount is obviously more significant than that of hexadecanol-palmitic acid-lauric acid amount, and the effect of hexadecanol-palmitic acid-lauric acid amount more significant than that of deionized water amount. Within the ranges of parameters in this study, absolute alcohol amount (mole ratio to tetraethyl orthosilicate) is 9.11, deionized water amount is 5.21 and hexadecanol-palmitic acid-lauric acid amount is 0.52. Hexadecanol-palmitic acid-lauric acid/SiO2 composite materials have the best heat-moisture comprehensive performance in the range of human comfort, i.e. average equilibrium moisture content is 0.102 0 g/g in relative humidity 50%, phase change temperature is 26.81-28.52℃, phase change enthalpy is 95.69 J/g, and belong to micron organic phase change core materials/inorganic substrate composite materials.
Hexadecanol-palmitic acid-lauric acid/SiO2 composite materials can be prepared by sol-gel method. The effect of absolute alcohol amount, deionized water amount and hexadecanol-palmitic acid-lauric acid amount on heat & moisture comprehensive property of hexadecanol-palmitic acid-lauric acid/SiO2 composites, and the preparation technology parameters for hexadecanol-palmitic acid-lauric acid/SiO2 composite materials was optimized. The results show that primary and secondary sequence of factors is the effect of absolute alcohol amount is obviously more significant than that of hexadecanol-palmitic acid-lauric acid amount, and the effect of hexadecanol-palmitic acid-lauric acid amount more significant than that of deionized water amount. Within the ranges of parameters in this study, absolute alcohol amount (mole ratio to tetraethyl orthosilicate) is 9.11, deionized water amount is 5.21 and hexadecanol-palmitic acid-lauric acid amount is 0.52. Hexadecanol-palmitic acid-lauric acid/SiO2 composite materials have the best heat-moisture comprehensive performance in the range of human comfort, i.e. average equilibrium moisture content is 0.102 0 g/g in relative humidity 50%, phase change temperature is 26.81-28.52℃, phase change enthalpy is 95.69 J/g, and belong to micron organic phase change core materials/inorganic substrate composite materials.
2017, 34(1): 210-216.
doi: 10.13801/j.cnki.fhclxb.20160328.006
Abstract:
The microcrystalline cellulose(MCC) and poly(butylene succinate) (PBS) composites were prepared by melt blending method. The influence of different temperature and MCC content on the steady-state rheological behavior and dynamic rheological behavior of the composites was studied by advanced capillary rheometer and rotationnal rheometer. The results show that:the rheological behavior of the corresponding relationship between the viscosity and the shear rate of the composites fits the power law model. Arrhenius equation can be employed to describe the dependence of the viscosity on temperature. The storage modulus (G') of the composites keeps invariant in linear viscoelastic region. When strain(γ) is over critical value (γc), the composites enter into the nonlinear viscoelastic region and the "Payne effect" occur. The γc decrease rapidly with the increase of strain. The storage modulus (G'), loss modulus (G") and complex viscosity(|η*|) of the composites all increase with the increasing contents of MCC in the range of angular frequency(ω) scanning. The value of G" is always higher than G' and the value of loss factor(tan(δ)) is always greater than one under the condition of the invariable content of MCC. Second plateau is observed for G' at low ω. The study of processing rheological properties of MCC/PBS composites might be valuable for the processing of MCC/PBS composites.
The microcrystalline cellulose(MCC) and poly(butylene succinate) (PBS) composites were prepared by melt blending method. The influence of different temperature and MCC content on the steady-state rheological behavior and dynamic rheological behavior of the composites was studied by advanced capillary rheometer and rotationnal rheometer. The results show that:the rheological behavior of the corresponding relationship between the viscosity and the shear rate of the composites fits the power law model. Arrhenius equation can be employed to describe the dependence of the viscosity on temperature. The storage modulus (G') of the composites keeps invariant in linear viscoelastic region. When strain(γ) is over critical value (γc), the composites enter into the nonlinear viscoelastic region and the "Payne effect" occur. The γc decrease rapidly with the increase of strain. The storage modulus (G'), loss modulus (G") and complex viscosity(|η*|) of the composites all increase with the increasing contents of MCC in the range of angular frequency(ω) scanning. The value of G" is always higher than G' and the value of loss factor(tan(δ)) is always greater than one under the condition of the invariable content of MCC. Second plateau is observed for G' at low ω. The study of processing rheological properties of MCC/PBS composites might be valuable for the processing of MCC/PBS composites.
2017, 34(1): 217-223.
doi: 10.13801/j.cnki.fhclxb.20160322.004
Abstract:
A micromechanical representative volume element (RVE) model was developed for analyzing effective mechanical behaviors of continuous bidirectional-fiber-reinforced matrix composites (CBFRCs) by combining the homogenization method and finite element method. In the proposed RVE model, the imperfect interfaces between the fiber and the matrix were taken into account by introducing some cohesive contact surfaces. The results show that an imperfect interface with a different interfacial stiffness may induce different damage onsets in the matrix of CBFRCs. Compared with the interfacial fracture energy, both the interfacial stiffness and strength play a more important role in determining the out-of-plane tensile strength of the CBFRCs, while have slight effect on the in-plane tensile strength. The tensile strength of the CBFRCs will be reduced because of the existence of interface. With an increase in the fiber volume fraction, the in-plane tensile strength increases sharply while the out-of-plane tensile strength decreases slightly. The numerical results indicate that the proposed model is simple and efficient for performing realistic optimum design on complex three dimensional fiber-reinforced composites.
A micromechanical representative volume element (RVE) model was developed for analyzing effective mechanical behaviors of continuous bidirectional-fiber-reinforced matrix composites (CBFRCs) by combining the homogenization method and finite element method. In the proposed RVE model, the imperfect interfaces between the fiber and the matrix were taken into account by introducing some cohesive contact surfaces. The results show that an imperfect interface with a different interfacial stiffness may induce different damage onsets in the matrix of CBFRCs. Compared with the interfacial fracture energy, both the interfacial stiffness and strength play a more important role in determining the out-of-plane tensile strength of the CBFRCs, while have slight effect on the in-plane tensile strength. The tensile strength of the CBFRCs will be reduced because of the existence of interface. With an increase in the fiber volume fraction, the in-plane tensile strength increases sharply while the out-of-plane tensile strength decreases slightly. The numerical results indicate that the proposed model is simple and efficient for performing realistic optimum design on complex three dimensional fiber-reinforced composites.
2017, 34(1): 224-230.
doi: 10.13801/j.cnki.fhclxb.20160328.011
Abstract:
The experiment results of uniaxial tension of airship envelope material Uretek5876 were analyzed in seven in-plane directions including 0°, 15°, 30°, 45°, 60°, 75°, 90°, which provided the law of residual strain and elasticity modulus with cycle inder. The modulus obtained from the theory of single layer board does not adapt to multi-layer pressure membrane material. VIC-2D digital speckle technique was used in tensile process to obtain the displacement field and strain field. Based on displacement field, the Poisson's ratio of Uretek 5876 was obtained. Strain field was not only used to analysis tensile failure mechanism, but also can forecast the position and type of fracture. The uniaxial tensile strength was tested by two kinds of specification of the sample, and the sample 3 was found to be more proper to response the actual strength of Uretek 5876. The work in this paper provides reference value for the design and analysis of the airship structure.
The experiment results of uniaxial tension of airship envelope material Uretek5876 were analyzed in seven in-plane directions including 0°, 15°, 30°, 45°, 60°, 75°, 90°, which provided the law of residual strain and elasticity modulus with cycle inder. The modulus obtained from the theory of single layer board does not adapt to multi-layer pressure membrane material. VIC-2D digital speckle technique was used in tensile process to obtain the displacement field and strain field. Based on displacement field, the Poisson's ratio of Uretek 5876 was obtained. Strain field was not only used to analysis tensile failure mechanism, but also can forecast the position and type of fracture. The uniaxial tensile strength was tested by two kinds of specification of the sample, and the sample 3 was found to be more proper to response the actual strength of Uretek 5876. The work in this paper provides reference value for the design and analysis of the airship structure.
