2018 Vol. 35, No. 1
2018, 35(1): 1-7.
doi: 10.13801/j.cnki.fhclxb.20170322.004
Abstract:
The γ-(2,3-epoxypropoxy) propytrimethoxysilane(KH560) graphene oxide (FGO) was prepared and characterized with FTIR and TGA. With the addition of FGO into radical-initiated and cationic-initiated photosensitive resins (CRCPR), the viscosity, gel rate and volume shrinkage of FGO/CRCPR were investigated. The mechanical properties of FGO/CRCPR composites were tested. The results show that compared with graphene oxide (GO), the viscosity doesn't markedly increase with the addition of FGO and the gel rate also doesn't reduce significantly, indicating that FGO has a good compatibility with the matrix. The results indicate that the volume shrinkage decreases by 37%, the tensile, the bending and the impact strength of the cured nano FGO/CRCPR composites, increase by 71.8%, 26.9% and 49.7% respectively, when the mass fraction is 0.06%, due to the excellent mechanical properties of FGO itself, the good compatibility of FGO with the matrix and the strong interface bonding between FGO and the matrix.
The γ-(2,3-epoxypropoxy) propytrimethoxysilane(KH560) graphene oxide (FGO) was prepared and characterized with FTIR and TGA. With the addition of FGO into radical-initiated and cationic-initiated photosensitive resins (CRCPR), the viscosity, gel rate and volume shrinkage of FGO/CRCPR were investigated. The mechanical properties of FGO/CRCPR composites were tested. The results show that compared with graphene oxide (GO), the viscosity doesn't markedly increase with the addition of FGO and the gel rate also doesn't reduce significantly, indicating that FGO has a good compatibility with the matrix. The results indicate that the volume shrinkage decreases by 37%, the tensile, the bending and the impact strength of the cured nano FGO/CRCPR composites, increase by 71.8%, 26.9% and 49.7% respectively, when the mass fraction is 0.06%, due to the excellent mechanical properties of FGO itself, the good compatibility of FGO with the matrix and the strong interface bonding between FGO and the matrix.
2018, 35(1): 8-15.
doi: 10.13801/j.cnki.fhclxb.20170412.001
Abstract:
A novel phase change polymer, poly(diethylene glycol hexadecyl ether acrylate) (PC16E2AC), was successfully synthesized by the free radical polymerization method. PC16E2AC with melting peak temperature at approximately 35℃, being close to the temperature of human skin, was selected as the core material to fabricate a series of core-sheath thermo-regulating fibers with various heat enthalpies via bicomponent wet-spinning technology with acrylonitrile-vinylidene chloride copolymer (P(AN-co-VDC)) being employed as sheath. The morphology, microstructure and thermal property of the composite thermo-regulated fibers were characterized systematically. The results show that the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers have uniform diameter, smooth surface and obvious core-sheath structure. Moreover, with increasing of the core-sheath extrusion ratio (S:C), the diameter of sheath increases gradually while the diameter of core shows the opposite trend. The breaking strength of PC16E2AC-P(AN-co-VDC) composite fibers improves steadily and the enthalpy also changes from 23 J/g to 57 J/g in the meantime. The fibers have good thermal stability under 220℃. 300 times thermal cycle test and 24 hours extraction experiment in toluene shed light on the good thermal reliability and excellent anti-osmosis property of the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers. It is noted that the melting peak temperature of the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers always remains at about 35℃, which indicates the potential for their application in smart textiles.
A novel phase change polymer, poly(diethylene glycol hexadecyl ether acrylate) (PC16E2AC), was successfully synthesized by the free radical polymerization method. PC16E2AC with melting peak temperature at approximately 35℃, being close to the temperature of human skin, was selected as the core material to fabricate a series of core-sheath thermo-regulating fibers with various heat enthalpies via bicomponent wet-spinning technology with acrylonitrile-vinylidene chloride copolymer (P(AN-co-VDC)) being employed as sheath. The morphology, microstructure and thermal property of the composite thermo-regulated fibers were characterized systematically. The results show that the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers have uniform diameter, smooth surface and obvious core-sheath structure. Moreover, with increasing of the core-sheath extrusion ratio (S:C), the diameter of sheath increases gradually while the diameter of core shows the opposite trend. The breaking strength of PC16E2AC-P(AN-co-VDC) composite fibers improves steadily and the enthalpy also changes from 23 J/g to 57 J/g in the meantime. The fibers have good thermal stability under 220℃. 300 times thermal cycle test and 24 hours extraction experiment in toluene shed light on the good thermal reliability and excellent anti-osmosis property of the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers. It is noted that the melting peak temperature of the PC16E2AC-P(AN-co-VDC) composite thermo-regulated fibers always remains at about 35℃, which indicates the potential for their application in smart textiles.
2018, 35(1): 16-23.
doi: 10.13801/j.cnki.fhclxb.20170315.003
Abstract:
In order to study the effect of sulfate corrosion on the degradation of interface properties of carbon fiber reinforced epoxy (CF/EP)-concrete. The sulfate environment was simulated by accelerated corrosion tests of cyclic dry-wet alternate. The degradation behavior of CF/EP-concrete interface under sulfite corrosion was studied. The results show that the effect of sulfate dry-wet alternation on the failure form of CF/EP-concrete interface is significant; the bond performance of interface increases slightly with the extending of corrosion time, and then decline accelerated. Based on the experiment and the existing interface theory, an interfacial bond-slip model is proposed, which is related to corrosion time. Through the comparison between the model predictions and the experimental data, the model can well reflect the degradation behavior of interfacial bonding performance under the dry-wet alternation of sulfate.
In order to study the effect of sulfate corrosion on the degradation of interface properties of carbon fiber reinforced epoxy (CF/EP)-concrete. The sulfate environment was simulated by accelerated corrosion tests of cyclic dry-wet alternate. The degradation behavior of CF/EP-concrete interface under sulfite corrosion was studied. The results show that the effect of sulfate dry-wet alternation on the failure form of CF/EP-concrete interface is significant; the bond performance of interface increases slightly with the extending of corrosion time, and then decline accelerated. Based on the experiment and the existing interface theory, an interfacial bond-slip model is proposed, which is related to corrosion time. Through the comparison between the model predictions and the experimental data, the model can well reflect the degradation behavior of interfacial bonding performance under the dry-wet alternation of sulfate.
2018, 35(1): 24-29.
doi: 10.13801/j.cnki.fhclxb.20170417.003
Abstract:
Traditional polyurethane foam was not good at absorbing the low-frequency noise, so magnetic polyurethane foam (MPF) loaded with carbonyl iron powder (CIP) was presented by one-step full water foaming method. Sound absorption test-platform of MPF was built. The influence of both the ratio of polyether polyols and isocyanate and CIP on sound absorption properties was investigated from both macroscopic and microscopic view. The micro topography of MPF was observed through SEM, the cell size was analyzed using statistical method, and the sound absorption performance of 64-1 600 Hz was tested by impedance tube and the transfer function method. The results show that the addition of CIP makes the average pore size of MPF decrease, the logarithmic distribution standard deviation increase, the open rate increase and the low-frequency sound absorption performance improve, especially less than 500 Hz; when the ratio of polyether polyol and isocyanate is 100:60, with 5wt% CIP, the low-frequency sound absorption performance of MPF is optimal and the average sound absorption coefficient of 64-500 Hz is 0.22.
Traditional polyurethane foam was not good at absorbing the low-frequency noise, so magnetic polyurethane foam (MPF) loaded with carbonyl iron powder (CIP) was presented by one-step full water foaming method. Sound absorption test-platform of MPF was built. The influence of both the ratio of polyether polyols and isocyanate and CIP on sound absorption properties was investigated from both macroscopic and microscopic view. The micro topography of MPF was observed through SEM, the cell size was analyzed using statistical method, and the sound absorption performance of 64-1 600 Hz was tested by impedance tube and the transfer function method. The results show that the addition of CIP makes the average pore size of MPF decrease, the logarithmic distribution standard deviation increase, the open rate increase and the low-frequency sound absorption performance improve, especially less than 500 Hz; when the ratio of polyether polyol and isocyanate is 100:60, with 5wt% CIP, the low-frequency sound absorption performance of MPF is optimal and the average sound absorption coefficient of 64-500 Hz is 0.22.
2018, 35(1): 30-34.
doi: 10.13801/j.cnki.fhclxb.20170331.001
Abstract:
Nano Mg(OH)2-Zn(OH)2 particles were prepared by reverse precipitation method, nano Mg(OH)2-ZnO/polyimide(PI) composite films with different mass contents of Mg(OH)2-ZnO were successfully prepared by in-situ polymerization and thermal imidization. The surface morphology, thermal stability, dielectric properties and breakdown strength of the films were characterized by SEM, TG, dielectric spectrum tester and breakdown strength tester. The results show that the Mg(OH)2-ZnO nanoparticles are homogeneously dispersed in the PI matrix, thermal stability decreases, dielectric constant, dielectric loss and electrical conductivity have been increased, the breakdown strength of nano Mg(OH)2-ZnO/PI composite films increases first and then decreases with the increasing of nanoparticles, and reaches a maximum value of 296 kV/mm at nanoparticle content of 2%.
Nano Mg(OH)2-Zn(OH)2 particles were prepared by reverse precipitation method, nano Mg(OH)2-ZnO/polyimide(PI) composite films with different mass contents of Mg(OH)2-ZnO were successfully prepared by in-situ polymerization and thermal imidization. The surface morphology, thermal stability, dielectric properties and breakdown strength of the films were characterized by SEM, TG, dielectric spectrum tester and breakdown strength tester. The results show that the Mg(OH)2-ZnO nanoparticles are homogeneously dispersed in the PI matrix, thermal stability decreases, dielectric constant, dielectric loss and electrical conductivity have been increased, the breakdown strength of nano Mg(OH)2-ZnO/PI composite films increases first and then decreases with the increasing of nanoparticles, and reaches a maximum value of 296 kV/mm at nanoparticle content of 2%.
2018, 35(1): 35-43.
doi: 10.13801/j.cnki.fhclxb.20170421.002
Abstract:
The linen was simply modified with the cationic surfactant trimethylstearylammonium bromide (STAB) in the aqueous solution. The linen was further hot compressed with unsaturated polyester(UPE) in the mold to prepare the linen/UPE composites. The mass fraction of linen was 28wt%. The moisture absorption ratio of linen is improved 30.3% compared with that of unmodified linen, and thus it becomes more hydrophobic. The moisture absorption behavior of the treated linen reinforced UPE (TL1/UPE) is determined to be improved 26% compared with that of the untreated linen reinforced UPE (UL/UPE). And the diffusion coefficient (D) value of the water molecules in TL1/UPE and UL/UPE is determined to be 0.63×10-2 mm2/h and 1.11×10-2 mm2/h, respectively. The water molecules diffuses faster in UL/UPE than in TL1/UPE. The impact strength of TL1/UPE is 2.4 times of that of the pure UPE, and thus the brittleness of UPE is dramatically improved. The TGA test shows the thermal stability of the linen/UPE composites can meet most of the utilizing demanding. It is proved that TL1/UPE is concluded to be with improved hygroscopicity, interfacial adhesion and mechanical properties, and it can be a kind of promising biocomposite with excellent comprehensive properties.
The linen was simply modified with the cationic surfactant trimethylstearylammonium bromide (STAB) in the aqueous solution. The linen was further hot compressed with unsaturated polyester(UPE) in the mold to prepare the linen/UPE composites. The mass fraction of linen was 28wt%. The moisture absorption ratio of linen is improved 30.3% compared with that of unmodified linen, and thus it becomes more hydrophobic. The moisture absorption behavior of the treated linen reinforced UPE (TL1/UPE) is determined to be improved 26% compared with that of the untreated linen reinforced UPE (UL/UPE). And the diffusion coefficient (D) value of the water molecules in TL1/UPE and UL/UPE is determined to be 0.63×10-2 mm2/h and 1.11×10-2 mm2/h, respectively. The water molecules diffuses faster in UL/UPE than in TL1/UPE. The impact strength of TL1/UPE is 2.4 times of that of the pure UPE, and thus the brittleness of UPE is dramatically improved. The TGA test shows the thermal stability of the linen/UPE composites can meet most of the utilizing demanding. It is proved that TL1/UPE is concluded to be with improved hygroscopicity, interfacial adhesion and mechanical properties, and it can be a kind of promising biocomposite with excellent comprehensive properties.
2018, 35(1): 44-49.
doi: 10.13801/j.cnki.fhclxb.20170314.006
Abstract:
Toluene-2,4-diisocyanate-poly propylene glycol (TDI-PPG) prepolymer was synthesized by two-step method with the protection of argon under normal pressure. A small amount of polytetrahydrofuran ether diol (PTMG) and trimethylolpropane (TMP) as chain cross-linker, were mixed with the TDI-PPG prepolymer to prepare a polyurethane resin casting. FTIR was used to analyze the molecular structure of theTDI-PPG prepolymer and the cured products. The mechanical properties of the polyurethane resin castings were tested by the universal testing machine. The results show that the addition of PTMG reduces the activity of the reaction while improves the toughness of PU cured product. When the mass fraction of -NCO in TDI-PPG prepolymer is 24.0wt%, the content of PTMG in chain extension crosslinker is 5wt%, and the isocyanate index (R) ranges from 1.01 to 1.05, the tensile strength is 87.4 MPa, the flexural strength is 104 MPa to 106 MPa, the modulus is 3.51 GPa to 3.60 GPa, the elongation at break is 4.45% to 4.83%
Toluene-2,4-diisocyanate-poly propylene glycol (TDI-PPG) prepolymer was synthesized by two-step method with the protection of argon under normal pressure. A small amount of polytetrahydrofuran ether diol (PTMG) and trimethylolpropane (TMP) as chain cross-linker, were mixed with the TDI-PPG prepolymer to prepare a polyurethane resin casting. FTIR was used to analyze the molecular structure of theTDI-PPG prepolymer and the cured products. The mechanical properties of the polyurethane resin castings were tested by the universal testing machine. The results show that the addition of PTMG reduces the activity of the reaction while improves the toughness of PU cured product. When the mass fraction of -NCO in TDI-PPG prepolymer is 24.0wt%, the content of PTMG in chain extension crosslinker is 5wt%, and the isocyanate index (R) ranges from 1.01 to 1.05, the tensile strength is 87.4 MPa, the flexural strength is 104 MPa to 106 MPa, the modulus is 3.51 GPa to 3.60 GPa, the elongation at break is 4.45% to 4.83%
2018, 35(1): 50-60.
doi: 10.13801/j.cnki.fhclxb.20170412.004
Abstract:
Composite material components may produce gaps during assembly due to their manufacturing errors. It is a basic method to use the liquid shim to fill the gaps. The tensile experiment was designed for composite single-lap bolted joint. An improved three-dimensional failure criterion and the corresponding degradation of the material were chosen in the finite element analysis(FEA) modeling. On this basis, the influences of the liquid shim on the mechanical properties of single-lap composite bolted joint were studied, such as strength and stiffness. The damage evolution process around the hole in composite and the state of stress and strain around the hole in shim were also studied. From the experiment and finite element results, it can be concluded that with the increase of liquid shim thickness, the tensile stiffness and peak load of the joints are reduced. It can also make the hole in composite have more serious damage under the same load and decrease the load when the initial damage appears. But the increase of the liquid shim thickness can decrease the peak stress and the plastic strain of the hole in the liquid shim and make their distribution more uniform, which can improve the stress condition around the shim's hole.
Composite material components may produce gaps during assembly due to their manufacturing errors. It is a basic method to use the liquid shim to fill the gaps. The tensile experiment was designed for composite single-lap bolted joint. An improved three-dimensional failure criterion and the corresponding degradation of the material were chosen in the finite element analysis(FEA) modeling. On this basis, the influences of the liquid shim on the mechanical properties of single-lap composite bolted joint were studied, such as strength and stiffness. The damage evolution process around the hole in composite and the state of stress and strain around the hole in shim were also studied. From the experiment and finite element results, it can be concluded that with the increase of liquid shim thickness, the tensile stiffness and peak load of the joints are reduced. It can also make the hole in composite have more serious damage under the same load and decrease the load when the initial damage appears. But the increase of the liquid shim thickness can decrease the peak stress and the plastic strain of the hole in the liquid shim and make their distribution more uniform, which can improve the stress condition around the shim's hole.
2018, 35(1): 61-69.
doi: 10.13801/j.cnki.fhclxb.20170508.001
Abstract:
The mechanical properties of the composite mechanical joint with hole delamination were studied by compressive test and numerical simulation. The loading capacity and failure mode of different test specimens were obtained by the compression test. In finite element simulation, the three-dimensional finite element model of composite mechanical joint was established based on ABAQUS software and the cohesive element was adopted to simulate the delamination. A good agreement was reached between the experiment and finite element method and the validity of the numerical method was verified. The failure mode, damage initiation and damage propagation of the composite structure were analyzed by the numerical model. A series of parametric studies were also performed to study the effects of the hole delamination position, the size of the delamination and the shape of the delamination on the compressive property of the composite mechanical joint. The results show that the load carrying capacity of the structure is the strongest when the delamination is located in the straight hole region and the bearing capacity of the composite structure with ellipse delamination is much bigger than the structure with square and circular shape delamination. In addition, no matter how the delamination shape changes, the delamination expands in the direction of compression as a semicircular shape.
The mechanical properties of the composite mechanical joint with hole delamination were studied by compressive test and numerical simulation. The loading capacity and failure mode of different test specimens were obtained by the compression test. In finite element simulation, the three-dimensional finite element model of composite mechanical joint was established based on ABAQUS software and the cohesive element was adopted to simulate the delamination. A good agreement was reached between the experiment and finite element method and the validity of the numerical method was verified. The failure mode, damage initiation and damage propagation of the composite structure were analyzed by the numerical model. A series of parametric studies were also performed to study the effects of the hole delamination position, the size of the delamination and the shape of the delamination on the compressive property of the composite mechanical joint. The results show that the load carrying capacity of the structure is the strongest when the delamination is located in the straight hole region and the bearing capacity of the composite structure with ellipse delamination is much bigger than the structure with square and circular shape delamination. In addition, no matter how the delamination shape changes, the delamination expands in the direction of compression as a semicircular shape.
2018, 35(1): 70-80.
doi: 10.13801/j.cnki.fhclxb.20170322.001
Abstract:
A concrete cable duct reinforced with glass fiber reinforced polymer (GFRP) bars was proposed. The newly developed cable duct is capable of reducing the energy dissipation and can be used to take place of traditional concrete cable duct which is reinforced with steel bars. The bending tests were conducted for several small and full size specimens of GFRP concrete cable duct and the bearing capacity of bending, deformation and failure characteristics were investigated. It is found that the mechanical characteristics of the GFRP concrete cable duct are similar with that of the concrete cable reinforced with steel bars. The loading-deflection curve is bi-linear with a cut-off point corresponding to the cracking of the concrete. The distribution of tension stresses on the side of the cable duct is not uniform and relatively high tension stresses are detected in some local regions. An appropriate calculation and design method was presented to capture the flexural capacity of the GFRP concrete cable duct. The theoretical predictions agree well with the experimental results.
A concrete cable duct reinforced with glass fiber reinforced polymer (GFRP) bars was proposed. The newly developed cable duct is capable of reducing the energy dissipation and can be used to take place of traditional concrete cable duct which is reinforced with steel bars. The bending tests were conducted for several small and full size specimens of GFRP concrete cable duct and the bearing capacity of bending, deformation and failure characteristics were investigated. It is found that the mechanical characteristics of the GFRP concrete cable duct are similar with that of the concrete cable reinforced with steel bars. The loading-deflection curve is bi-linear with a cut-off point corresponding to the cracking of the concrete. The distribution of tension stresses on the side of the cable duct is not uniform and relatively high tension stresses are detected in some local regions. An appropriate calculation and design method was presented to capture the flexural capacity of the GFRP concrete cable duct. The theoretical predictions agree well with the experimental results.
2018, 35(1): 81-88.
doi: 10.13801/j.cnki.fhclxb.20170413.002
Abstract:
During the toughening process in which the thermoset epoxy resin was toughened by the thermoplastic polyethersulfone(PES), the phase separation process could be controlled to optimize the phase morphology of the PES-epoxy resin blend systems, for the sake of improving the impact strength of thermoset epoxy resin. In the phase separation processes of PES-epoxy blend systems, in which both the stress relaxation phenomenon of PES and the curing reaction phenomenon of epoxy resin were considered, the viscoelastic model was used to describe the evolution process of micro-structure, then the mechanism and dynamic process of the phase separation processes were revealed, and the influences of composites material and processing parameters, such as PES content, PES molecular weight, dynamic asymmetry degree between PES and epoxy resin, curing conditions, on the phase morphology evolution of blend systems were analyzed. And then the basis for the optimization of phase morphology of the PES-epoxy systems was established.
During the toughening process in which the thermoset epoxy resin was toughened by the thermoplastic polyethersulfone(PES), the phase separation process could be controlled to optimize the phase morphology of the PES-epoxy resin blend systems, for the sake of improving the impact strength of thermoset epoxy resin. In the phase separation processes of PES-epoxy blend systems, in which both the stress relaxation phenomenon of PES and the curing reaction phenomenon of epoxy resin were considered, the viscoelastic model was used to describe the evolution process of micro-structure, then the mechanism and dynamic process of the phase separation processes were revealed, and the influences of composites material and processing parameters, such as PES content, PES molecular weight, dynamic asymmetry degree between PES and epoxy resin, curing conditions, on the phase morphology evolution of blend systems were analyzed. And then the basis for the optimization of phase morphology of the PES-epoxy systems was established.
2018, 35(1): 89-94.
doi: 10.13801/j.cnki.fhclxb.20170320.006
Abstract:
A non-unique corresponding relationship was verified between porosity P and ultrasonic attenuation coefficient α in carbon fibre reinforced polymer (CFRP). In order to explain the relationship from the point of ultrasonic scattering mechanisms, the CFRP models containing various size of voids (P=0.5%~3.5%) were established according to a kind of unidirectional CFRP laminate with thickness of 2 mm manufactured by autoclave moulding process. And the values of ultrasonic attenucation coefficient α were obtained by numerical calculation method. When the transverse dimension D of void is 56 μm and the normalized wavenumber kD=2π Dλ <1 (the wavelength λ ≈ 560 μm), α increases linearly and slowly with the increasing of P. And α shows logarithmic growth with the increasing of P when D=93 μm (kD ≈1). The simulation results show that, the ultrasonic attenuation may include two kinds of mechanism of Rayleigh scattering and Stochastic scattering depending on the normalized wavenumber when the ultrasound propagate in CFRP containing voids. The random and complex void morphology causes a non-unique corresponding relationship between porosity and ultrasonic attenuation coefficient.
A non-unique corresponding relationship was verified between porosity P and ultrasonic attenuation coefficient α in carbon fibre reinforced polymer (CFRP). In order to explain the relationship from the point of ultrasonic scattering mechanisms, the CFRP models containing various size of voids (P=0.5%~3.5%) were established according to a kind of unidirectional CFRP laminate with thickness of 2 mm manufactured by autoclave moulding process. And the values of ultrasonic attenucation coefficient α were obtained by numerical calculation method. When the transverse dimension D of void is 56 μm and the normalized wavenumber kD=2π Dλ <1 (the wavelength λ ≈ 560 μm), α increases linearly and slowly with the increasing of P. And α shows logarithmic growth with the increasing of P when D=93 μm (kD ≈1). The simulation results show that, the ultrasonic attenuation may include two kinds of mechanism of Rayleigh scattering and Stochastic scattering depending on the normalized wavenumber when the ultrasound propagate in CFRP containing voids. The random and complex void morphology causes a non-unique corresponding relationship between porosity and ultrasonic attenuation coefficient.
2018, 35(1): 95-102.
doi: 10.13801/j.cnki.fhclxb.20170328.001
Abstract:
The curing kinetics of 603 thermoplastic toughened epoxy resin was investigated by non-isothermal differential scanning calorimetry (DSC). The curing reaction of 603 epoxy resin system was consisted of two dominant reactions (reaction 1 and 2), as evidenced by the presence of a double peak on the DSC thermograms. The curing kinetics of the 603 resin system was investigated after separating the two overlapping exothermic peaks. The overall apparent activation energies of the curing processes were fitted respectively with Kissinger method and a two-parameter (m, n) Kamal model was employed to describe the curing kinetics. The reliability of established model was proved by comparing the calculation results with the experimental results of three different curing processes of the epoxy resin system. Based on the exothermic curves at different heating rates, the curing temperature of the reaction 1 whose heat accounted for 70% of the total heat of reaction is (177.3±2.2)℃ and the initial temperature and the curing temperature of the reaction 2 whose heat accounted for 30% of the total heat of reaction are (178.6±0.7)℃ and (216.9±1.7)℃ respectively by extrapolation method. The results have important significance for the analysis of curing kinetics of multi-component thermosetting resin system and optimization of composite processing.
The curing kinetics of 603 thermoplastic toughened epoxy resin was investigated by non-isothermal differential scanning calorimetry (DSC). The curing reaction of 603 epoxy resin system was consisted of two dominant reactions (reaction 1 and 2), as evidenced by the presence of a double peak on the DSC thermograms. The curing kinetics of the 603 resin system was investigated after separating the two overlapping exothermic peaks. The overall apparent activation energies of the curing processes were fitted respectively with Kissinger method and a two-parameter (m, n) Kamal model was employed to describe the curing kinetics. The reliability of established model was proved by comparing the calculation results with the experimental results of three different curing processes of the epoxy resin system. Based on the exothermic curves at different heating rates, the curing temperature of the reaction 1 whose heat accounted for 70% of the total heat of reaction is (177.3±2.2)℃ and the initial temperature and the curing temperature of the reaction 2 whose heat accounted for 30% of the total heat of reaction are (178.6±0.7)℃ and (216.9±1.7)℃ respectively by extrapolation method. The results have important significance for the analysis of curing kinetics of multi-component thermosetting resin system and optimization of composite processing.
2018, 35(1): 103-109.
doi: 10.13801/j.cnki.fhclxb.20170322.002
Abstract:
Thermal conductivities of 3D woven carbon fiber/epoxy resin composites with different structures were measured by using transient hot-wire method and flash method, respectively. From the finite elemental simulations of 3D orthogonal woven carbon fiber/epoxy resin composites, it can be seen that, the roles of the warp, weft and Z-yarn in heat transfer process change with the change of the measuring method. By using transient hot-wire method, the thermal conductivity of 2.5D woven carbon fiber/epoxy resin composite is higher than warp-reinforced 2.5D, but lower than 3D orthogonal. However, the thermal conductivities of warp-reinforced 2.5D and 3D orthogonal woven carbon fiber/epoxy resin composites are less than 2.5D by using flash method. That is because of that, the same yarn in 3D woven carbon fiber/epoxy resin composites plays distinct roles in heat transfer process by using different measurement methods. Thermal conductivities of 2.5D woven carbon fiber/epoxy resin composites obtained by using transient hot-wire method and flash method increase with the increasing of fiber volume fraction. In addition, the increase of thermal conductivity obtained by flash method is more obvious, which is caused by the crime of warp. Based on these investigation. it can be concluded that the thermal response mechanisms of 3D woven carbon fiber/epoxy resin composites under different heating modes are different.
Thermal conductivities of 3D woven carbon fiber/epoxy resin composites with different structures were measured by using transient hot-wire method and flash method, respectively. From the finite elemental simulations of 3D orthogonal woven carbon fiber/epoxy resin composites, it can be seen that, the roles of the warp, weft and Z-yarn in heat transfer process change with the change of the measuring method. By using transient hot-wire method, the thermal conductivity of 2.5D woven carbon fiber/epoxy resin composite is higher than warp-reinforced 2.5D, but lower than 3D orthogonal. However, the thermal conductivities of warp-reinforced 2.5D and 3D orthogonal woven carbon fiber/epoxy resin composites are less than 2.5D by using flash method. That is because of that, the same yarn in 3D woven carbon fiber/epoxy resin composites plays distinct roles in heat transfer process by using different measurement methods. Thermal conductivities of 2.5D woven carbon fiber/epoxy resin composites obtained by using transient hot-wire method and flash method increase with the increasing of fiber volume fraction. In addition, the increase of thermal conductivity obtained by flash method is more obvious, which is caused by the crime of warp. Based on these investigation. it can be concluded that the thermal response mechanisms of 3D woven carbon fiber/epoxy resin composites under different heating modes are different.
2018, 35(1): 110-116.
doi: 10.13801/j.cnki.fhclxb.20170417.001
Abstract:
In order to improve the strength of composite T-joint, effects of adhesive, filler and Z-pin on enhancing strength of composite T-joint were studied. Same size samples with two different adhesives, two different fillers and Z-pinned and Un-pinned composite T-joints were designed, Tensile tests were performed and then ultimate displacement and ultimate strength were obtained and compared. Damage evolution of T-joints was analyzed. It is shown that the ultimate displacement and strength of J299 adhesive composite T-joint are 57.8% and 64.7% higher than that of J116B joint, and the ultimate displacement and strength of ZXC195 enhanced core composite T-joint are 51.7% and 30.3% higher than that of unidirectional core joint, and Z-pin increases the ultimate displacement and strength of composite T-joint by 190.8% and 31.9%. These three structure parameters can only alter the ultimate strength and displacement of composite T-joint, but the structure stiffness keeps unchanged. Adhesive property has the largest effect on the ultimate strength, while Z-pin has the largest effect on the ultimate displacement.
In order to improve the strength of composite T-joint, effects of adhesive, filler and Z-pin on enhancing strength of composite T-joint were studied. Same size samples with two different adhesives, two different fillers and Z-pinned and Un-pinned composite T-joints were designed, Tensile tests were performed and then ultimate displacement and ultimate strength were obtained and compared. Damage evolution of T-joints was analyzed. It is shown that the ultimate displacement and strength of J299 adhesive composite T-joint are 57.8% and 64.7% higher than that of J116B joint, and the ultimate displacement and strength of ZXC195 enhanced core composite T-joint are 51.7% and 30.3% higher than that of unidirectional core joint, and Z-pin increases the ultimate displacement and strength of composite T-joint by 190.8% and 31.9%. These three structure parameters can only alter the ultimate strength and displacement of composite T-joint, but the structure stiffness keeps unchanged. Adhesive property has the largest effect on the ultimate strength, while Z-pin has the largest effect on the ultimate displacement.
2018, 35(1): 117-123.
doi: 10.13801/j.cnki.fhclxb.20170416.001
Abstract:
After acidification, sensitization and activation of multi-carbon nanotubes(CNTs), Ni-coated CNTs (Ni-CNTs)were produced by electroless plating through ultrasonic spray atomization. The obtained CNTs were characterized by TEM, EDS and Raman spectra. The results show that a continous and uniform Ni-plating layer is obtained. And the dispersion of CNTs in the product has been improved, which makes Ni-CNTs more conducive in the application area of composite materials. It is found that the different microstructure of the Ni plated absorbing properties of carbon nanotubes have obvious difference. For the Ni plated CNTs with relatively thin coatings, the maximum microwave absorbing peak of the Ni-CNTs is -17.12 dB at 9.36 GHz, the band width is 5.28 GHz (R<-5 dB) and 2 GHz (R<-10 dB), which is contributed to manufacturing broadband composite absorbing materials.
After acidification, sensitization and activation of multi-carbon nanotubes(CNTs), Ni-coated CNTs (Ni-CNTs)were produced by electroless plating through ultrasonic spray atomization. The obtained CNTs were characterized by TEM, EDS and Raman spectra. The results show that a continous and uniform Ni-plating layer is obtained. And the dispersion of CNTs in the product has been improved, which makes Ni-CNTs more conducive in the application area of composite materials. It is found that the different microstructure of the Ni plated absorbing properties of carbon nanotubes have obvious difference. For the Ni plated CNTs with relatively thin coatings, the maximum microwave absorbing peak of the Ni-CNTs is -17.12 dB at 9.36 GHz, the band width is 5.28 GHz (R<-5 dB) and 2 GHz (R<-10 dB), which is contributed to manufacturing broadband composite absorbing materials.
2018, 35(1): 124-131.
doi: 10.13801/j.cnki.fhclxb.20170315.002
Abstract:
Finite element method was used to explore particles volume fraction, particles strain hardening index, particles spacing and reticular structure influence on the strength and the ductility of the new amorphous alloy composite materials which was metallic glass composites (MGCs). The results show that with the increase of particles strain hardening index, strength and toughness of the composite material have greatly improved, increase of particles volume fraction, smaller particle spacing and mesh structure configuration will also make the toughness of the composite materials increased. All these will be contributed to designing good toughness of composites.
Finite element method was used to explore particles volume fraction, particles strain hardening index, particles spacing and reticular structure influence on the strength and the ductility of the new amorphous alloy composite materials which was metallic glass composites (MGCs). The results show that with the increase of particles strain hardening index, strength and toughness of the composite material have greatly improved, increase of particles volume fraction, smaller particle spacing and mesh structure configuration will also make the toughness of the composite materials increased. All these will be contributed to designing good toughness of composites.
2018, 35(1): 132-141.
doi: 10.13801/j.cnki.fhclxb.20170315.001
Abstract:
The damage and fracture behavior of in-situ TiB2 particle reinforced 2024-T4 aluminum matrix composites (TiB2/2024-T4) with particle volume fraction of 4.17% were investigated experimentally by means of in situ tension and SEM observation. The test results show that the aluminum alloy matrix within the TiB2 particle segregation bands breaks earlier than that in the particle sparse region. Based on such phenomenon and with the same particle volume fraction as well as the randomly distributed particles, three 2D unit cell finite element models of different segregation band widths were established. Tensile load and periodic boundary conditions were imposed. The radial return algorithm in plane stress state was deduced and applied to the elastoplastic iteration procedure. The initiation and propagation of micro matrix cracks in TiB2 segregation bands were simulated with Rice-Tracey local failure criterion. The numerical results show that the matrix near the particle poles suffers serious damage. Particle segregation leads to rapid accumulation of matrix damage and soon grows into micro matrix cracks. The fracture strain decreases with the increase of particle segregation degree. In addition, the nonlinear part of the stress-strain curve of the TiB2/2024-T4 unit cell model is obviously lower than the real curve, indicating that besides the mechanism of load transfer strengthening, other indirect particle reinforcement mechanisms may also enhance the strength of the material to a certain extent.
The damage and fracture behavior of in-situ TiB2 particle reinforced 2024-T4 aluminum matrix composites (TiB2/2024-T4) with particle volume fraction of 4.17% were investigated experimentally by means of in situ tension and SEM observation. The test results show that the aluminum alloy matrix within the TiB2 particle segregation bands breaks earlier than that in the particle sparse region. Based on such phenomenon and with the same particle volume fraction as well as the randomly distributed particles, three 2D unit cell finite element models of different segregation band widths were established. Tensile load and periodic boundary conditions were imposed. The radial return algorithm in plane stress state was deduced and applied to the elastoplastic iteration procedure. The initiation and propagation of micro matrix cracks in TiB2 segregation bands were simulated with Rice-Tracey local failure criterion. The numerical results show that the matrix near the particle poles suffers serious damage. Particle segregation leads to rapid accumulation of matrix damage and soon grows into micro matrix cracks. The fracture strain decreases with the increase of particle segregation degree. In addition, the nonlinear part of the stress-strain curve of the TiB2/2024-T4 unit cell model is obviously lower than the real curve, indicating that besides the mechanism of load transfer strengthening, other indirect particle reinforcement mechanisms may also enhance the strength of the material to a certain extent.
2018, 35(1): 142-149.
doi: 10.13801/j.cnki.fhclxb.20170328.002
Abstract:
A stable dispersion in mixed solvent of water and N, N-dimethyl formamide (DMF) of graphene (G) was synthesized by constant voltage one-step electrochemical approach using a high-purity graphite rod as the raw material and mixed acid as the electrolyte. The G/nanoTiO2 photocatalytic composites were prepared by the method of sol-gel and high temperature heating under nitrogen protection using butyl titanate ester and G as the precursors. The structural properties and microcosmic morphology of the graphite stripping product were characterized by using XRD, FTIR, ultraviolet-visible spectroscopy(UV-Vis), XPS, SEM and TEM. The photocatalytic properties in the anoxic water of different G/nano TiO2 composites dosages were studied by using 3,5-dinitrosalicylic acid(DNS)as the probe and ultraviolet light as the light source. The results show that distance between layer is enlarged, layers have high transmittance and less reactive groups are generated on six carbon ring and the conjugated π bond structure of G get good maintain by the method of constant voltage one-step electrochemical. The as-prepared G/nano TiO2 microcosmic morphology shows that well crystallized, closely combined with the TiO2 is found to be deposited on G. The degradation experiment shows that G/nano TiO2 composites have good performance for the photocatalytic degradation of DNS, and photocatalytic activity has a direct influence by different dosages. The nitryl become amino in benzene ring, the middle products of 5-aminosalicylic acid or phloroglucinol are produced from the photocatalytic reduction reaction of DNS under the anoxic condition, part of DNS is decomposited and CO2 and H2O are generated by photocatalytic oxidation.
A stable dispersion in mixed solvent of water and N, N-dimethyl formamide (DMF) of graphene (G) was synthesized by constant voltage one-step electrochemical approach using a high-purity graphite rod as the raw material and mixed acid as the electrolyte. The G/nanoTiO2 photocatalytic composites were prepared by the method of sol-gel and high temperature heating under nitrogen protection using butyl titanate ester and G as the precursors. The structural properties and microcosmic morphology of the graphite stripping product were characterized by using XRD, FTIR, ultraviolet-visible spectroscopy(UV-Vis), XPS, SEM and TEM. The photocatalytic properties in the anoxic water of different G/nano TiO2 composites dosages were studied by using 3,5-dinitrosalicylic acid(DNS)as the probe and ultraviolet light as the light source. The results show that distance between layer is enlarged, layers have high transmittance and less reactive groups are generated on six carbon ring and the conjugated π bond structure of G get good maintain by the method of constant voltage one-step electrochemical. The as-prepared G/nano TiO2 microcosmic morphology shows that well crystallized, closely combined with the TiO2 is found to be deposited on G. The degradation experiment shows that G/nano TiO2 composites have good performance for the photocatalytic degradation of DNS, and photocatalytic activity has a direct influence by different dosages. The nitryl become amino in benzene ring, the middle products of 5-aminosalicylic acid or phloroglucinol are produced from the photocatalytic reduction reaction of DNS under the anoxic condition, part of DNS is decomposited and CO2 and H2O are generated by photocatalytic oxidation.
2018, 35(1): 150-157.
doi: 10.13801/j.cnki.fhclxb.20170406.001
Abstract:
Carbon nanotubes (CNTs)/Al2O3 composite was fabricated by in-situ chemical vapor deposition growth of CNTs in Al2O3 ceramic green body during its sinetering. The results show that multi-walled CNTs have been sucessfully grown and distributed homogeneously in the Al2O3 ceramic matrix. The roots of CNTs embed in the Al2O3 grains reveal directly growth and firmly combination. The in-situ growth of CNTs in the Al2O3 ceramic matrixes requires strictly controlling of the preparation conditions. The CNTs grow at 850℃, while no CNTs are observed in the samples fabricated at higher or lower temperatures. The adding of the pore former, carbon source and catalyst all affect the in-situ growth of CNTs. The entire CNTs/Al2O3 composite with densified structure was obtained through subsequent sintering at higher temperature. The CNTs offers the CNTs/Al2O3 obviously electrical conductivity up to 3.7 S/m, 13 orders of magnitude higher than that of the bare Al2O3. This in-situ growth in preformed ceramic body as one-step strategy is attractive for the development of CNTs/ceramic composites combined with high mechanical and multi-functional properties.
Carbon nanotubes (CNTs)/Al2O3 composite was fabricated by in-situ chemical vapor deposition growth of CNTs in Al2O3 ceramic green body during its sinetering. The results show that multi-walled CNTs have been sucessfully grown and distributed homogeneously in the Al2O3 ceramic matrix. The roots of CNTs embed in the Al2O3 grains reveal directly growth and firmly combination. The in-situ growth of CNTs in the Al2O3 ceramic matrixes requires strictly controlling of the preparation conditions. The CNTs grow at 850℃, while no CNTs are observed in the samples fabricated at higher or lower temperatures. The adding of the pore former, carbon source and catalyst all affect the in-situ growth of CNTs. The entire CNTs/Al2O3 composite with densified structure was obtained through subsequent sintering at higher temperature. The CNTs offers the CNTs/Al2O3 obviously electrical conductivity up to 3.7 S/m, 13 orders of magnitude higher than that of the bare Al2O3. This in-situ growth in preformed ceramic body as one-step strategy is attractive for the development of CNTs/ceramic composites combined with high mechanical and multi-functional properties.
2018, 35(1): 158-167.
doi: 10.13801/j.cnki.fhclxb.20170821.007
Abstract:
Ni/TiB2-TiC composites were fabricated by spark plasma sintering using Ni, Ti and B4C powder mixture as precursor. Effects of Ni content on phase composition, microstructure, microhardness and wear resistance of composites were analyzed. The results show that the mainly phases of Ni/TiB2-TiC composites are γ-Ni, TiB2 and TiC. TiB2 phase presents rectangle strip and polygon shape, while TiC phase is irregular patch shape. With the increase of Ni content, the size of TiB2 and TiC ceramics decrease gradually. Additionally, TiB2 and TiC homogeneously disperse in the Ni binder phase, and the denser composites are obtained. Wear properties and mechanisms are influenced significantly by Ni content. When Ni content is low(20wt% and 30wt%), severe delaminate occurs with high and fluctuant coefficient of friction(COF). Micro-cutting wear appears with lower and smoother COF with the increase of Ni content(40wt%). However, when the Ni content continues to increase(50wt%), the adhesive wear results in poorer wear resisitance and higher COF due to the aggregation of Ni.
Ni/TiB2-TiC composites were fabricated by spark plasma sintering using Ni, Ti and B4C powder mixture as precursor. Effects of Ni content on phase composition, microstructure, microhardness and wear resistance of composites were analyzed. The results show that the mainly phases of Ni/TiB2-TiC composites are γ-Ni, TiB2 and TiC. TiB2 phase presents rectangle strip and polygon shape, while TiC phase is irregular patch shape. With the increase of Ni content, the size of TiB2 and TiC ceramics decrease gradually. Additionally, TiB2 and TiC homogeneously disperse in the Ni binder phase, and the denser composites are obtained. Wear properties and mechanisms are influenced significantly by Ni content. When Ni content is low(20wt% and 30wt%), severe delaminate occurs with high and fluctuant coefficient of friction(COF). Micro-cutting wear appears with lower and smoother COF with the increase of Ni content(40wt%). However, when the Ni content continues to increase(50wt%), the adhesive wear results in poorer wear resisitance and higher COF due to the aggregation of Ni.
2018, 35(1): 168-172.
doi: 10.13801/j.cnki.fhclxb.20170418.001
Abstract:
Al2O3 fiber was added into the SiO2 matrix powder, and the Al2O3/SiO2 ceramic core was prepared by hot-pressing method. The effects of Al2O3 fiber content on the properties of Al2O3/SiO2 ceramic core were analyzed. The results indicate that the mass fraction of Al2O3 fiber has a great influence on the linear shrinkage, bulk density and flexural strength of Al2O3 fiber/SiO2 ceramic core. When the content of Al2O3 fiber is more than 1wt%, the linear shrinkage of the Al2O3/SiO2 ceramic core decreases to 0.335%, the volume density of the core decreases, and it is stable at 1.790 g·cm-3; When the Al2O3 fiber mass fraction is 1wt%, the flexural strength of the core reaches the maximum value of 20.48 MPa. The mechanism of Al2O3 fiber on the sintering shrinkage of Al2O3/SiO2 ceramic core was analyzed.
Al2O3 fiber was added into the SiO2 matrix powder, and the Al2O3/SiO2 ceramic core was prepared by hot-pressing method. The effects of Al2O3 fiber content on the properties of Al2O3/SiO2 ceramic core were analyzed. The results indicate that the mass fraction of Al2O3 fiber has a great influence on the linear shrinkage, bulk density and flexural strength of Al2O3 fiber/SiO2 ceramic core. When the content of Al2O3 fiber is more than 1wt%, the linear shrinkage of the Al2O3/SiO2 ceramic core decreases to 0.335%, the volume density of the core decreases, and it is stable at 1.790 g·cm-3; When the Al2O3 fiber mass fraction is 1wt%, the flexural strength of the core reaches the maximum value of 20.48 MPa. The mechanism of Al2O3 fiber on the sintering shrinkage of Al2O3/SiO2 ceramic core was analyzed.
2018, 35(1): 173-179.
doi: 10.13801/j.cnki.fhclxb.20170401.003
Abstract:
The Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 complex catalysts were prepared using CoSn(OH)6 and ZnSn(OH)6 hollow nanocubes by an ultrasound process with ascorbic acid as the soft reductant, respectively, and demonstrate excellent performance towards the methanol oxidation reaction (MOR). The Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 catalysts exhibit higher mass activities (1095.6 mA/mg and 699.5 mA/mg, respectively) compared to Pt/C (594.6 mA/mg) catalyst towards methanol oxidation. XRD, SEM, TEM, XPS and electrochemical measurements were employed to explore the relationships of the crystal structure and the properties of catalysts. CO-stripping experiment results indicate that the hydroxide supports facilitates the removal of CO on Pt surface. The increased activity and resistance of CO poisoning for Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 catalysts can be attributed to the strong interaction between the support (Co, Zn)Sn(OH)6 and Pt in the catalysts and the large amount of hydroxyls on the support surface. The higher relative intensity of Pt in the (Co, Zn)Sn(OH)6 catalysts also contributes to the higher MOR activity. The (Co, Zn)Sn(OH)6 towards methanol catalytic electro-oxidation can disclose the influence of the support structure on the catalytic activity and will be helpful for the development and application of complex catalysts in direct methanol fuel cells (DMFCs).
The Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 complex catalysts were prepared using CoSn(OH)6 and ZnSn(OH)6 hollow nanocubes by an ultrasound process with ascorbic acid as the soft reductant, respectively, and demonstrate excellent performance towards the methanol oxidation reaction (MOR). The Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 catalysts exhibit higher mass activities (1095.6 mA/mg and 699.5 mA/mg, respectively) compared to Pt/C (594.6 mA/mg) catalyst towards methanol oxidation. XRD, SEM, TEM, XPS and electrochemical measurements were employed to explore the relationships of the crystal structure and the properties of catalysts. CO-stripping experiment results indicate that the hydroxide supports facilitates the removal of CO on Pt surface. The increased activity and resistance of CO poisoning for Pt/CoSn(OH)6 and Pt/ZnSn(OH)6 catalysts can be attributed to the strong interaction between the support (Co, Zn)Sn(OH)6 and Pt in the catalysts and the large amount of hydroxyls on the support surface. The higher relative intensity of Pt in the (Co, Zn)Sn(OH)6 catalysts also contributes to the higher MOR activity. The (Co, Zn)Sn(OH)6 towards methanol catalytic electro-oxidation can disclose the influence of the support structure on the catalytic activity and will be helpful for the development and application of complex catalysts in direct methanol fuel cells (DMFCs).
2018, 35(1): 180-184.
doi: 10.13801/j.cnki.fhclxb.20170509.003
Abstract:
The conducting film based on chemical vapor deposition (CVD)-graphene/poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) hybrid composites was prepared by using liquid-phase exfoliation method. The microstructure of the graphene/PEDOT-PSS hybrid composites was characterized by using atomic force microscope and SEM. The conduction mechanism of the as-fabricated graphene/PEDOT-PSS film was studied by using ultraviolet-visible absorption spectroscopy, X-ray photoelectronic spectroscopy and FTIR. The graphene/PEDOT-PSS film shows high electrical properties with a sheet resistance of approximate 8 Ω/□. The conjugation effect between graphene and thiophene in PEDOT main chain leads to a change of electron cloud density, which enhances the carrier delocalization of PEDOT main chain and results in the conductivity enhancement of the PEDOT. Furthermore, the conjugation effect leads to the increase of carrier density of graphene, which can enhance the conductivity of graphene/PEDOT-PSS composite.
The conducting film based on chemical vapor deposition (CVD)-graphene/poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) hybrid composites was prepared by using liquid-phase exfoliation method. The microstructure of the graphene/PEDOT-PSS hybrid composites was characterized by using atomic force microscope and SEM. The conduction mechanism of the as-fabricated graphene/PEDOT-PSS film was studied by using ultraviolet-visible absorption spectroscopy, X-ray photoelectronic spectroscopy and FTIR. The graphene/PEDOT-PSS film shows high electrical properties with a sheet resistance of approximate 8 Ω/□. The conjugation effect between graphene and thiophene in PEDOT main chain leads to a change of electron cloud density, which enhances the carrier delocalization of PEDOT main chain and results in the conductivity enhancement of the PEDOT. Furthermore, the conjugation effect leads to the increase of carrier density of graphene, which can enhance the conductivity of graphene/PEDOT-PSS composite.
2018, 35(1): 185-191.
doi: 10.13801/j.cnki.fhclxb.20170418.005
Abstract:
The silica/natural rubber (SiO2/NR) composites was prepared by wet mixing technology with liquid natural rubber (LNR) as compatibilizer. The tensile fracture surface morphology, Payne effect, glass transition temperature (Tg), bound rubber contents and crosslink density of SiO2/NR composites were characterized by SEM, rubber processing analyzer (RPA), differential scanning calorimetry(DSC), swelling method and nuclear magnetic resonance instrument. The effect of LNR on the rubber-filler interaction was also investigated. The results show that SiO2 particles are tightly encompassed by NR and fracture surfaces appear toughness fracture in the presence of LNR. The Payne effect of SiO2/NR composites is obviously decreased under certain amount of silica SiO2. Tg is observed from -59.57℃ to -56.61℃ and bound rubber content is observed from 40.24% to 44.02% when the mass ratio of SiO2 to NR is 60:100. The interfacial interaction of SiO2/NR composites quantitatively evaluated by Lorenz-Park equation is strengthened in the presence of LNR. Nuclear magnetic resonance test shows that the crosslink density has great enhancements and transverse relaxation time (T2) decrease for modified SiO2/NR composites, T2 decreases 4.20 ms, 5.84 ms and 7.86 ms when the mass ratio of SiO2 to NR are 30:100, 50:100 and 70:100, respectively, which can be ascribed to the stronger filler-rubber interfacial interaction that limites the extensibility of NR chains with incorporation of LNR. It is revealed that LNR has good compatibility, which contributes to strengthening interfacial interaction of SiO2/NR composites.
The silica/natural rubber (SiO2/NR) composites was prepared by wet mixing technology with liquid natural rubber (LNR) as compatibilizer. The tensile fracture surface morphology, Payne effect, glass transition temperature (Tg), bound rubber contents and crosslink density of SiO2/NR composites were characterized by SEM, rubber processing analyzer (RPA), differential scanning calorimetry(DSC), swelling method and nuclear magnetic resonance instrument. The effect of LNR on the rubber-filler interaction was also investigated. The results show that SiO2 particles are tightly encompassed by NR and fracture surfaces appear toughness fracture in the presence of LNR. The Payne effect of SiO2/NR composites is obviously decreased under certain amount of silica SiO2. Tg is observed from -59.57℃ to -56.61℃ and bound rubber content is observed from 40.24% to 44.02% when the mass ratio of SiO2 to NR is 60:100. The interfacial interaction of SiO2/NR composites quantitatively evaluated by Lorenz-Park equation is strengthened in the presence of LNR. Nuclear magnetic resonance test shows that the crosslink density has great enhancements and transverse relaxation time (T2) decrease for modified SiO2/NR composites, T2 decreases 4.20 ms, 5.84 ms and 7.86 ms when the mass ratio of SiO2 to NR are 30:100, 50:100 and 70:100, respectively, which can be ascribed to the stronger filler-rubber interfacial interaction that limites the extensibility of NR chains with incorporation of LNR. It is revealed that LNR has good compatibility, which contributes to strengthening interfacial interaction of SiO2/NR composites.
2018, 35(1): 192-199.
doi: 10.13801/j.cnki.fhclxb.20170417.002
Abstract:
Erosion-wear performance in gas-solid of cement mortar subjected to freeze-thaw cycles in composite salts solution was studied by using sediment-air injection method. Based on the SEM, the laser scanning confocal microscopy (LSCM) and XRD, surface morphologies of specimen after erosion and the chemical composition of specimen surface before and after freeze-thaw in salts solution were measured to explore the erosion damage mechanism. Results show that in the same erosion conditions, erosion rate increases as the impact angle increase, and the growth tendency in the high impact angle is relatively slower; The erosion rate firstly decreases and then increases with the increasing freeze-thaw cycles in composite salts solution, and the erosion rate reaches minimum at freeze-thaw of 10 times; Under the same condition, the erosion rate in 8% concentration is a little higher than that in 10% concentration. In the erosion damage process, normal components of kinetic energy play a decisive role, which is characterized by the emerging of erosion pits and micro-damage zones. The effect of freeze-thaw in composite salts solution on erosion-wear performance is mainly reflected in two aspects as follows. Physical aspects:the effect of supersaturated solution crystallization in the cooling process, ice expansion pressure and osmotic pressure on internal pores; Chemical aspects:ettringite and gypsum crystal generated through the chemical reaction between anion and cement-based materials filling in inside of cement mortar, improving its compactness. However, the increasing pressure can promote crack formation in the later stage, which has a negative effect on the erosion-wear resistance of cement mortar.
Erosion-wear performance in gas-solid of cement mortar subjected to freeze-thaw cycles in composite salts solution was studied by using sediment-air injection method. Based on the SEM, the laser scanning confocal microscopy (LSCM) and XRD, surface morphologies of specimen after erosion and the chemical composition of specimen surface before and after freeze-thaw in salts solution were measured to explore the erosion damage mechanism. Results show that in the same erosion conditions, erosion rate increases as the impact angle increase, and the growth tendency in the high impact angle is relatively slower; The erosion rate firstly decreases and then increases with the increasing freeze-thaw cycles in composite salts solution, and the erosion rate reaches minimum at freeze-thaw of 10 times; Under the same condition, the erosion rate in 8% concentration is a little higher than that in 10% concentration. In the erosion damage process, normal components of kinetic energy play a decisive role, which is characterized by the emerging of erosion pits and micro-damage zones. The effect of freeze-thaw in composite salts solution on erosion-wear performance is mainly reflected in two aspects as follows. Physical aspects:the effect of supersaturated solution crystallization in the cooling process, ice expansion pressure and osmotic pressure on internal pores; Chemical aspects:ettringite and gypsum crystal generated through the chemical reaction between anion and cement-based materials filling in inside of cement mortar, improving its compactness. However, the increasing pressure can promote crack formation in the later stage, which has a negative effect on the erosion-wear resistance of cement mortar.
2018, 35(1): 200-207.
doi: 10.13801/j.cnki.fhclxb.20170321.005
Abstract:
The core-shell structure composites were prepared by co-extrusion technology with the wood/high density polyethylene(W/HDPE) as shell layer and the poplar laminated veneer lumber (LVL) as core layer. Both of the LVL-W/HDPE and LVL were treated with boiled-frozen-dry environment at one cycle, and the low velocity impact property was investigated at three different impact energies of 50 J, 75 J and 100 J. The results indicate that the absorption energy and damage depth of LVL-W/HDPE was decrease by 2.9% and 15.9%, respectively, compared with LVL at the impact energy of 50 J. And the decreasing magnitude of the absorption energy and damage depth are about 3.9% and 9.2% at 75 J. While the results are almost the same at 100 J. The treated results also prove that the LVL-W/HDPE has better environmental resistance as well as impact property because of the presence of the protection shell layer.
The core-shell structure composites were prepared by co-extrusion technology with the wood/high density polyethylene(W/HDPE) as shell layer and the poplar laminated veneer lumber (LVL) as core layer. Both of the LVL-W/HDPE and LVL were treated with boiled-frozen-dry environment at one cycle, and the low velocity impact property was investigated at three different impact energies of 50 J, 75 J and 100 J. The results indicate that the absorption energy and damage depth of LVL-W/HDPE was decrease by 2.9% and 15.9%, respectively, compared with LVL at the impact energy of 50 J. And the decreasing magnitude of the absorption energy and damage depth are about 3.9% and 9.2% at 75 J. While the results are almost the same at 100 J. The treated results also prove that the LVL-W/HDPE has better environmental resistance as well as impact property because of the presence of the protection shell layer.
2018, 35(1): 208-217.
doi: 10.13801/j.cnki.fhclxb.20170411.001
Abstract:
Asymptotic homogenization (AH) method has rigorous mathematical foundation and can provide an accurate solution for the effective thermal conductivity (ETC) of periodic composite materials. A new implementation algorithm based AH method predicting the ETC of periodic composite materials was presented. Compared with the original implementation algorithm, the new implementation algorithm has two advantages:Its implementation as simple as representative volume element (RVE) method. The commercial finite element analysis (FEA) software as black box is used and the ETC of periodic composite materials through several simple steps can be obtained. The new implementation of AH can simultaneously use more than one element type to discretize a unit cell, which can save much computational cost in predicting the ETC of complex structure. This work is expected to greatly promote the widespread use of AH in predicting the ETC of periodic composite materials.
Asymptotic homogenization (AH) method has rigorous mathematical foundation and can provide an accurate solution for the effective thermal conductivity (ETC) of periodic composite materials. A new implementation algorithm based AH method predicting the ETC of periodic composite materials was presented. Compared with the original implementation algorithm, the new implementation algorithm has two advantages:Its implementation as simple as representative volume element (RVE) method. The commercial finite element analysis (FEA) software as black box is used and the ETC of periodic composite materials through several simple steps can be obtained. The new implementation of AH can simultaneously use more than one element type to discretize a unit cell, which can save much computational cost in predicting the ETC of complex structure. This work is expected to greatly promote the widespread use of AH in predicting the ETC of periodic composite materials.
2018, 35(1): 218-228.
doi: 10.13801/j.cnki.fhclxb.20170412.003
Abstract:
The geometrically exact nonlinear modeling of composite beam with arbitrary cross sectional shape, generally anisotropic material behavior and large deflection had been presented, based on the generalized Timoshenko beam theory of Hodges. The concept of decomposition of rotation tensor was used to calculate the strains in the beam. The variational asymptotical method was used to determine the arbitrary warping of the beam cross section. The generalized Timoshenko strain energy was derived from the equilibrium equations and the second-order asymptotically correct strain energy. The geometrically exact nonlinear equations of motion were established by the Hamilton's generalized principle. The established modeling was used for the static and dynamic analysis of composite beams and was verified by the comparisons with experimental data. The influences of the non-classical effects such as the cross sectional warping and the transverse shear deformation on the composite beams were investigated. The results indicate that the cross sectional warping has significant influences on the static deformation and the natural frequencies of the composite beams, and the influences of the transverse shear deformation on the static deformation and the natural frequencies of the composite beams are related to the length to depth ratio of the beam.
The geometrically exact nonlinear modeling of composite beam with arbitrary cross sectional shape, generally anisotropic material behavior and large deflection had been presented, based on the generalized Timoshenko beam theory of Hodges. The concept of decomposition of rotation tensor was used to calculate the strains in the beam. The variational asymptotical method was used to determine the arbitrary warping of the beam cross section. The generalized Timoshenko strain energy was derived from the equilibrium equations and the second-order asymptotically correct strain energy. The geometrically exact nonlinear equations of motion were established by the Hamilton's generalized principle. The established modeling was used for the static and dynamic analysis of composite beams and was verified by the comparisons with experimental data. The influences of the non-classical effects such as the cross sectional warping and the transverse shear deformation on the composite beams were investigated. The results indicate that the cross sectional warping has significant influences on the static deformation and the natural frequencies of the composite beams, and the influences of the transverse shear deformation on the static deformation and the natural frequencies of the composite beams are related to the length to depth ratio of the beam.
2018, 35(1): 229-237.
doi: 10.13801/j.cnki.fhclxb.20170412.007
Abstract:
In order to characterize the nonlinear and time-dependent piezoelectro-viscoelasto-plastic behavior of metal core piezoelectric fiber/polymer (MPF/PM) composites, an incremental micromechanics model of MPF/PM was developed based on the variational asymptotic theory. Firstly, the incremental constitutive equations of polymer and MPF were derived. The energy functional of variational principle for the MPF/PM piezoelectro-viscoelasto-plastic of (MPF/PM) composites was derived based on the Hamilton expansion principle. The incremental process associated with the instantaneous effective electromechanical coupling matrix, and solved by the finite element method. The presented model was used to investigate the effects of different volume fraction of aluminum, the change rate of electric field and loading condition on the effective global stress-strain relationship and uniaxial longitudinal tensile properties. The results show that the constructed model can accurately simulate the nonlinear, time-dependent behavior of MPF/PM composites under electromechanical coupling, which lays a theoretical foundation for the practical application of this new type of smart material.
In order to characterize the nonlinear and time-dependent piezoelectro-viscoelasto-plastic behavior of metal core piezoelectric fiber/polymer (MPF/PM) composites, an incremental micromechanics model of MPF/PM was developed based on the variational asymptotic theory. Firstly, the incremental constitutive equations of polymer and MPF were derived. The energy functional of variational principle for the MPF/PM piezoelectro-viscoelasto-plastic of (MPF/PM) composites was derived based on the Hamilton expansion principle. The incremental process associated with the instantaneous effective electromechanical coupling matrix, and solved by the finite element method. The presented model was used to investigate the effects of different volume fraction of aluminum, the change rate of electric field and loading condition on the effective global stress-strain relationship and uniaxial longitudinal tensile properties. The results show that the constructed model can accurately simulate the nonlinear, time-dependent behavior of MPF/PM composites under electromechanical coupling, which lays a theoretical foundation for the practical application of this new type of smart material.
2018, 35(1): 238-243.
doi: 10.13801/j.cnki.fhclxb.20170412.006
Abstract:
The microstructure of bone tissue is similar to that of fiber-reinforced composites. It mainly consists of the mineral and organic matters arranged alternately. Three kinds of collagen microfibril models were constructed based on the degree of mineralization. The effect of organic phase on mechanical properties of microfibril was investigated on considering of tropocollagen molecules and organic cross-links. The results were further studied by compared with the literature reported. The numerical results show that the stiffness value and trend of plastic deformation of the microfibril models are significantly improved with the increasing of the degree of mineralization. Shrinkage of tropocollagen molecules results in the increase of elastic modulus and the decrease of toughness. The mechanical properties of bone tissue improve and its brittleness increases with the increasing of the number of cross-links. The results are helpful to reveal the effects of the active constituents and microstructures of bone tissue on its mechanical properties, which can provide theoretical foundations to develop bone repair materials.
The microstructure of bone tissue is similar to that of fiber-reinforced composites. It mainly consists of the mineral and organic matters arranged alternately. Three kinds of collagen microfibril models were constructed based on the degree of mineralization. The effect of organic phase on mechanical properties of microfibril was investigated on considering of tropocollagen molecules and organic cross-links. The results were further studied by compared with the literature reported. The numerical results show that the stiffness value and trend of plastic deformation of the microfibril models are significantly improved with the increasing of the degree of mineralization. Shrinkage of tropocollagen molecules results in the increase of elastic modulus and the decrease of toughness. The mechanical properties of bone tissue improve and its brittleness increases with the increasing of the number of cross-links. The results are helpful to reveal the effects of the active constituents and microstructures of bone tissue on its mechanical properties, which can provide theoretical foundations to develop bone repair materials.
