2017 Vol. 34, No. 9
2017, 34(9): 1879-1886.
doi: 10.13801/j.cnki.fhclxb.20161208.004
Abstract:
A new method has been applied to prepare the wood powder/polypropylene (PP) composites. The key procedure is to inject fluids (ethanol and propanol) during extrusion process and to make the fluid in the subcritical state at a certain temperature. Furthermore, the structures of wood powder/polypropylene composites were analyzed and observed by FTIR, SEM. Due to the hydrophilic nature, there are a large number of hydroxyls in wood powder, which can esterify with maleic anhydride grafted polypropylene (PP-g-MAH). The results show that the subcritical fluid as a swelling agent and reaction medium promotes the interfacial reaction between wood powder and PP-g-MAH, which leads to the improvement of the interface bond strength. When ethanol is at subcritical state (190℃, (2.4±0.1)MPa, 120 r/min), ethanol as a reaction media is helpful to swelling and liquefaction of wood powder. Subcritical ethanol can further promote the esterification between wood powder and PP-g-MAH as well as the dispersibility of wood powder in PP matrix. In addition, wood powder can be permeated by PP-g-MAH under the high temperature and pressure, the interfacial reaction is strengthened. The tensile strength, flexural strength, flexural modulus and non-notched impact strength of the wood powder/polypropylene composites at the reaction condition in subcritical ethanol reach 23.5 MPa, 52.5 MPa, 4.8 GPa, and 5.9 kJ · m-2, respectively, comparing with wood powder/PP composites without fluids during extrusion procession.
A new method has been applied to prepare the wood powder/polypropylene (PP) composites. The key procedure is to inject fluids (ethanol and propanol) during extrusion process and to make the fluid in the subcritical state at a certain temperature. Furthermore, the structures of wood powder/polypropylene composites were analyzed and observed by FTIR, SEM. Due to the hydrophilic nature, there are a large number of hydroxyls in wood powder, which can esterify with maleic anhydride grafted polypropylene (PP-g-MAH). The results show that the subcritical fluid as a swelling agent and reaction medium promotes the interfacial reaction between wood powder and PP-g-MAH, which leads to the improvement of the interface bond strength. When ethanol is at subcritical state (190℃, (2.4±0.1)MPa, 120 r/min), ethanol as a reaction media is helpful to swelling and liquefaction of wood powder. Subcritical ethanol can further promote the esterification between wood powder and PP-g-MAH as well as the dispersibility of wood powder in PP matrix. In addition, wood powder can be permeated by PP-g-MAH under the high temperature and pressure, the interfacial reaction is strengthened. The tensile strength, flexural strength, flexural modulus and non-notched impact strength of the wood powder/polypropylene composites at the reaction condition in subcritical ethanol reach 23.5 MPa, 52.5 MPa, 4.8 GPa, and 5.9 kJ · m-2, respectively, comparing with wood powder/PP composites without fluids during extrusion procession.
2017, 34(9): 1887-1894.
doi: 10.13801/j.cnki.fhclxb.20161129.003
Abstract:
The graphene oxide(GO) was prepared by the modified Hummers' method and nano graphene oxide/poly(butylene succinate) (GO/PBS) composites were synthesized via in situ compound technology, and its properties were studied. The experimental results showe that a suitable content GO can accelerate the crystallization process of GO/PBS composite. A certain amount of GO can improve the mechanical property and increase the speed of enzyme degradation. Otherwise, the crystal size of composites modified by inorganic nanoparticles is reduced, GO serves as an effective nucleating agent for the crystallization of GO/PBS.
The graphene oxide(GO) was prepared by the modified Hummers' method and nano graphene oxide/poly(butylene succinate) (GO/PBS) composites were synthesized via in situ compound technology, and its properties were studied. The experimental results showe that a suitable content GO can accelerate the crystallization process of GO/PBS composite. A certain amount of GO can improve the mechanical property and increase the speed of enzyme degradation. Otherwise, the crystal size of composites modified by inorganic nanoparticles is reduced, GO serves as an effective nucleating agent for the crystallization of GO/PBS.
2017, 34(9): 1895-1901.
doi: 10.13801/j.cnki.fhclxb.20161124.007
Abstract:
The radiation crosslinking modification of 30wt% glass fibers (GF) reinforced nylon 6 (PA6) composites was conducted using electron beam at different radiation doses. The triallyl isocyanurate (TAIC) was used as the sensitizer. The effects of radiation doses and sensitizer loadings on the structure, mechanical properties, water absorption and thermal stability of GF/PA6 composites were investigated. The experiment results show that the tensile strength, flexural strength, and impact strength of GF/PA6 composites are enhanced by 15.7%, 43.2%, 18.7% and 17.3%, respectively, at a TAIC content of 1wt% and a radiation dose of 50 kGy. Moreover, both the crosslinking structure of the GF/PA6 composites composites and the carbonized structure after the pyrolysis are observed by SEM. The crosslinking density of GF/PA6 is found to increase with increasing the radiation dose. During the pyrolysis process, the formed dense carbonized structure is effective in slowing down, even eliminating the formation rate of molten drops of GF/PA6 composites.
The radiation crosslinking modification of 30wt% glass fibers (GF) reinforced nylon 6 (PA6) composites was conducted using electron beam at different radiation doses. The triallyl isocyanurate (TAIC) was used as the sensitizer. The effects of radiation doses and sensitizer loadings on the structure, mechanical properties, water absorption and thermal stability of GF/PA6 composites were investigated. The experiment results show that the tensile strength, flexural strength, and impact strength of GF/PA6 composites are enhanced by 15.7%, 43.2%, 18.7% and 17.3%, respectively, at a TAIC content of 1wt% and a radiation dose of 50 kGy. Moreover, both the crosslinking structure of the GF/PA6 composites composites and the carbonized structure after the pyrolysis are observed by SEM. The crosslinking density of GF/PA6 is found to increase with increasing the radiation dose. During the pyrolysis process, the formed dense carbonized structure is effective in slowing down, even eliminating the formation rate of molten drops of GF/PA6 composites.
2017, 34(9): 1902-1910.
doi: 10.13801/j.cnki.fhclxb.20161205.001
Abstract:
The composites of kenaf (KF) reinforced polypropylene(PP) and palm(PF) reinforced polypropylene(PP) were modified by PVA crosslinking. PF/PP and KF/PP composites were prepared by compression molding process.The effects of different crosslinking methods on the structure and properties of composites were studied.SEM and DMA were used to describe the interfacial bonding and mechanical properties of the composites.The results reveal that the PVA and coupling agent have the best effect on the natural fiber reinforce PP composite.When the KF/PP is modified by 5%PVA and 3% coupling agent, the flexural strength increases by 25.2%, the flexural modulus increases by 35.49%, and the shear strength increases by 28%, which reach 50.90 MPa, 5.76 GPa, 5.4 MPa, respectively.When the PF/PP is modified by 5%PVA and 2% coupling agent, the flexural strength increases by 31.46%, the flexural modulus increases by 27.07%, and the shear strength increases by 21.75%, which reach 44.33 MPa, 2.32 GPa, 5.18 MPa, respectively.The water content of the modified KF/PP and PF/PP composites are reduced by 46.89% and 10.63%, respectively, the water absorption of the modified KF/PP and PF/PP composites are reduced by 8.57% and 6.12%, respectively. After the modification of KF/PP, the storage modulus increases by 20.93%.The Tg value of the modified PF/PP composite increase from 90.1℃ to 113.8℃, which increases by 26.30%. SEM reveal that the crosslinking modification of PVA and coupling agent effectively improve the adhesion between fiber and polypropylene, and the interface bonding between the fiber and polypropylene is also improved.
The composites of kenaf (KF) reinforced polypropylene(PP) and palm(PF) reinforced polypropylene(PP) were modified by PVA crosslinking. PF/PP and KF/PP composites were prepared by compression molding process.The effects of different crosslinking methods on the structure and properties of composites were studied.SEM and DMA were used to describe the interfacial bonding and mechanical properties of the composites.The results reveal that the PVA and coupling agent have the best effect on the natural fiber reinforce PP composite.When the KF/PP is modified by 5%PVA and 3% coupling agent, the flexural strength increases by 25.2%, the flexural modulus increases by 35.49%, and the shear strength increases by 28%, which reach 50.90 MPa, 5.76 GPa, 5.4 MPa, respectively.When the PF/PP is modified by 5%PVA and 2% coupling agent, the flexural strength increases by 31.46%, the flexural modulus increases by 27.07%, and the shear strength increases by 21.75%, which reach 44.33 MPa, 2.32 GPa, 5.18 MPa, respectively.The water content of the modified KF/PP and PF/PP composites are reduced by 46.89% and 10.63%, respectively, the water absorption of the modified KF/PP and PF/PP composites are reduced by 8.57% and 6.12%, respectively. After the modification of KF/PP, the storage modulus increases by 20.93%.The Tg value of the modified PF/PP composite increase from 90.1℃ to 113.8℃, which increases by 26.30%. SEM reveal that the crosslinking modification of PVA and coupling agent effectively improve the adhesion between fiber and polypropylene, and the interface bonding between the fiber and polypropylene is also improved.
2017, 34(9): 1911-1918.
doi: 10.13801/j.cnki.fhclxb.20161216.002
Abstract:
The ultrasonic vibration was added to extrusion process, and the influences of ultrasonic vibration on the morphology, crystallization, electrical and thermal properties of nano graphene nanoplatelet (GNP)/polypropylene(PP) composites with high GNP contents were investigated. The results show that the ultrasonic vibration provides powerful shock wave and micro jet which can reduce the thickness of GNP effectively, reduce the agglomeration of GNP and enhance the uniform dispersion of GNP in PP matrix. The morphology is benefit for the building of electrical and thermal network, therefore the electrical conductivity and thermal conductivity of GNP/PP composites are increased. Compared to non-ultrasonic vibration, after the addition of 100 W ultrasonic vibration, with the increase of the GNP content, the amplitude of electrical and thermal conductivity improvement increase continuously, when the GNP content is 15wt%, the increase of electrical conductivity is 85%, and thermal conductivity is 9.7%. When the GNP content is 12wt%, with increasing the ultrasonic power, the electrical and thermal conductivity increase first and then decrease. When the ultrasonic power is 200 W, the increasement of electrical and thermal conductivity is 214% and 17.2%, respectively. While the results of 300 W ultrasonic treatment show that the higher power of the ultrasonic vibration makes the flake sizes of GNP decreased, which lets it more difficult to build a complete electrical and thermal network, so that the performance is slightly decreased.
The ultrasonic vibration was added to extrusion process, and the influences of ultrasonic vibration on the morphology, crystallization, electrical and thermal properties of nano graphene nanoplatelet (GNP)/polypropylene(PP) composites with high GNP contents were investigated. The results show that the ultrasonic vibration provides powerful shock wave and micro jet which can reduce the thickness of GNP effectively, reduce the agglomeration of GNP and enhance the uniform dispersion of GNP in PP matrix. The morphology is benefit for the building of electrical and thermal network, therefore the electrical conductivity and thermal conductivity of GNP/PP composites are increased. Compared to non-ultrasonic vibration, after the addition of 100 W ultrasonic vibration, with the increase of the GNP content, the amplitude of electrical and thermal conductivity improvement increase continuously, when the GNP content is 15wt%, the increase of electrical conductivity is 85%, and thermal conductivity is 9.7%. When the GNP content is 12wt%, with increasing the ultrasonic power, the electrical and thermal conductivity increase first and then decrease. When the ultrasonic power is 200 W, the increasement of electrical and thermal conductivity is 214% and 17.2%, respectively. While the results of 300 W ultrasonic treatment show that the higher power of the ultrasonic vibration makes the flake sizes of GNP decreased, which lets it more difficult to build a complete electrical and thermal network, so that the performance is slightly decreased.
2017, 34(9): 1919-1925.
doi: 10.13801/j.cnki.fhclxb.20161130.003
Abstract:
The heat resistant layer of aluminium phosphate (AlPO4) was prepared on the surface of polyethersulphone (PES) matrix using the high temperature calcination molding process. The microstructure, chemical component and thermal stability of AlPO4-PES layered composites were characterized by techniques of SEM, confocal laser scanning microscopy-three dimensional morphology analysis (CLSM-3D), FTIR and TGA. The influence of AlPO4 content on the thermal conductivity and dielectric property of AlPO4-PES layered composites was investigated. The results show that the incorporation of AlPO4 leads to significant changes on the microscopic structure of PES matrix. And heat resistant layer of AlPO4 and PES matrix are combined together via physical way. The thermal stability of AlPO4-PES layered composites is obviously enhanced with increasing the AlPO4 content, while the thermal conductivity of composites is decreased continuously. As the AlPO4 content increases, both the dielectric constant and dielectric dissipation of AlPO4-PES layered composites are reduced, and they exhibit excellent frequency stability in the test range of 0.1-5 MHz.
The heat resistant layer of aluminium phosphate (AlPO4) was prepared on the surface of polyethersulphone (PES) matrix using the high temperature calcination molding process. The microstructure, chemical component and thermal stability of AlPO4-PES layered composites were characterized by techniques of SEM, confocal laser scanning microscopy-three dimensional morphology analysis (CLSM-3D), FTIR and TGA. The influence of AlPO4 content on the thermal conductivity and dielectric property of AlPO4-PES layered composites was investigated. The results show that the incorporation of AlPO4 leads to significant changes on the microscopic structure of PES matrix. And heat resistant layer of AlPO4 and PES matrix are combined together via physical way. The thermal stability of AlPO4-PES layered composites is obviously enhanced with increasing the AlPO4 content, while the thermal conductivity of composites is decreased continuously. As the AlPO4 content increases, both the dielectric constant and dielectric dissipation of AlPO4-PES layered composites are reduced, and they exhibit excellent frequency stability in the test range of 0.1-5 MHz.
2017, 34(9): 1926-1933.
doi: 10.13801/j.cnki.fhclxb.20161202.004
Abstract:
In order to solve the problem of absent nondestructive test methods, the frequency domain spectroscopy (FDS) based on dielectric response theory had been used to test Vacuum Pressure Impregnating (VPI) less resin epoxy mica insulation of large generator stator bars. The effect of electrical aging of insulation dielectric properties was studied through comparing and analyzing the dielectric loss and dielectric constant curves in different ageing time and temperature. Result shows that the dielectric properties of epoxy-mica insulation decrease because of electrical aging, especially the epoxy resin. Molecular chain failure leads to the decrease of the bonding ability after the electrical ageing. More medium interfaces appear inside insulation material and the polar molecule activity improves at the same time. Interface polarization and turning-direction polarization are intensified. Dielectric loss and dielectric constant increase with electrical aging time.
In order to solve the problem of absent nondestructive test methods, the frequency domain spectroscopy (FDS) based on dielectric response theory had been used to test Vacuum Pressure Impregnating (VPI) less resin epoxy mica insulation of large generator stator bars. The effect of electrical aging of insulation dielectric properties was studied through comparing and analyzing the dielectric loss and dielectric constant curves in different ageing time and temperature. Result shows that the dielectric properties of epoxy-mica insulation decrease because of electrical aging, especially the epoxy resin. Molecular chain failure leads to the decrease of the bonding ability after the electrical ageing. More medium interfaces appear inside insulation material and the polar molecule activity improves at the same time. Interface polarization and turning-direction polarization are intensified. Dielectric loss and dielectric constant increase with electrical aging time.
2017, 34(9): 1934-1943.
doi: 10.13801/j.cnki.fhclxb.20161202.003
Abstract:
Based on asymptotic expansion homogenization theory, which satisfies the assumptions of periodicity and separation of two length scales, the effective elastic properties were identified fast for particle reinforced composites and its macro-micro stress field information were also conveniently obtained by the second-development of ABAQUS. In order to approximate the actual composite structure, the randomly distributed spherical particles considering different sizes and contents were adopted in micro-scale model. The effective elastic parameters were extracted from the micro-scale model with finite element analysis and the error analysis was carried out for validating the simulation method. Besides, the nonlinear coupled multi-scale analysis method, based on the couple mechanism of two scales, was realized by using the user defined subroutines in ABAQUS, which is cooperated with a computationally efficient method. Finally, the influence of the plasticity evolution in micro-scale model in terms of particle reinforced materials on the macro mechanical properties was studied. Since the present method and codes are also applicable for the other composite materials, this work can provide useful reference for the study of other composite materials.
Based on asymptotic expansion homogenization theory, which satisfies the assumptions of periodicity and separation of two length scales, the effective elastic properties were identified fast for particle reinforced composites and its macro-micro stress field information were also conveniently obtained by the second-development of ABAQUS. In order to approximate the actual composite structure, the randomly distributed spherical particles considering different sizes and contents were adopted in micro-scale model. The effective elastic parameters were extracted from the micro-scale model with finite element analysis and the error analysis was carried out for validating the simulation method. Besides, the nonlinear coupled multi-scale analysis method, based on the couple mechanism of two scales, was realized by using the user defined subroutines in ABAQUS, which is cooperated with a computationally efficient method. Finally, the influence of the plasticity evolution in micro-scale model in terms of particle reinforced materials on the macro mechanical properties was studied. Since the present method and codes are also applicable for the other composite materials, this work can provide useful reference for the study of other composite materials.
2017, 34(9): 1944-1952.
doi: 10.13801/j.cnki.fhclxb.20161216.003
Abstract:
The influence of cryogenic mediums (liquid nitrogen and liquid oxygen, LN2 and LO2) on the mechanical properties of carbon fiber reinforced epoxy resin (CFs/EP) was studied. T700 carbon fibers (CFs) and CFs/EP were immersed in liquid nitrogen (LN2) and liquid oxygen (LO2) for 120 h. The surface elements and morphology of T700 CFs were investigated by XPS and SEM, respectively. The mechanical properties of T700 CFs and CFs/EP were also researched after immersion in LN2 and LO2. The results show that there are obvious damages on the surface of T700 CFs after immersion in LN2, but no damages are found on the surface of T700 CFs after immersion in LO2. The different influence of LN2 and LO2 on the surface elements of T700 CFs and single fiber tensile strength could be negligible. After immersion in LN2 and LO2, the tensile strength of CFs/EP decrease 15.26% and 14.38%, respectively, and the flexural strength of CFs/EP increase 56.18% and 57.81%, respectively. Consequently, the influence of LN2 and LO2 on the mechanical properties of CFs/EP are nearly no difference.
The influence of cryogenic mediums (liquid nitrogen and liquid oxygen, LN2 and LO2) on the mechanical properties of carbon fiber reinforced epoxy resin (CFs/EP) was studied. T700 carbon fibers (CFs) and CFs/EP were immersed in liquid nitrogen (LN2) and liquid oxygen (LO2) for 120 h. The surface elements and morphology of T700 CFs were investigated by XPS and SEM, respectively. The mechanical properties of T700 CFs and CFs/EP were also researched after immersion in LN2 and LO2. The results show that there are obvious damages on the surface of T700 CFs after immersion in LN2, but no damages are found on the surface of T700 CFs after immersion in LO2. The different influence of LN2 and LO2 on the surface elements of T700 CFs and single fiber tensile strength could be negligible. After immersion in LN2 and LO2, the tensile strength of CFs/EP decrease 15.26% and 14.38%, respectively, and the flexural strength of CFs/EP increase 56.18% and 57.81%, respectively. Consequently, the influence of LN2 and LO2 on the mechanical properties of CFs/EP are nearly no difference.
2017, 34(9): 1953-1959.
doi: 10.13801/j.cnki.fhclxb.20170104.001
Abstract:
The short-Kevlar-fiber toughening method for carbon-fiber/aluminum-honeycomb sandwich panels was introduced. Three-point bending tests and in-plane compression tests were conducted. The load-displacement curves and failure modes were compared for toughened specimens and non-toughened specimens, which indicated that interface debonding followed by local failures occurred on the non-toughened specimens, whereas the toughened specimens behaved global failure with structural integrity. The results demonstrate that the bending property, compressive property and energy absorption of the carbon fiber/aluminum honeycomb sandwich panels are respectively increased by more than 14%, 55% and 61% by the short Kevlar fiber toughening. The observations of the damaged interface by SEM reveal that the toughened interface is kept bonded, while the face-core separation of the toughened specimen is caused by the fracture of honeycomb core. The FEM modeling was conducted to numerically analyze the three-point bending and in-plane compression performance of carbon fiber/aluminum honeycomb sandwich structures with and without short Kevlar fiber toughening. The FEM results provide general guidance for the designing of such sandwich structures.
The short-Kevlar-fiber toughening method for carbon-fiber/aluminum-honeycomb sandwich panels was introduced. Three-point bending tests and in-plane compression tests were conducted. The load-displacement curves and failure modes were compared for toughened specimens and non-toughened specimens, which indicated that interface debonding followed by local failures occurred on the non-toughened specimens, whereas the toughened specimens behaved global failure with structural integrity. The results demonstrate that the bending property, compressive property and energy absorption of the carbon fiber/aluminum honeycomb sandwich panels are respectively increased by more than 14%, 55% and 61% by the short Kevlar fiber toughening. The observations of the damaged interface by SEM reveal that the toughened interface is kept bonded, while the face-core separation of the toughened specimen is caused by the fracture of honeycomb core. The FEM modeling was conducted to numerically analyze the three-point bending and in-plane compression performance of carbon fiber/aluminum honeycomb sandwich structures with and without short Kevlar fiber toughening. The FEM results provide general guidance for the designing of such sandwich structures.
2017, 34(9): 1960-1972.
doi: 10.13801/j.cnki.fhclxb.20161208.002
Abstract:
The armor plates manufactured by pressing curing process which using UHMWPE fiber, S-glass fiber, Aramid 1414 fiber or Heterocyclic aramid fiber as reinforcement and thermoplastic resin (PO or WPU) as matrix were experimentally investigated in this paper. The effects on the ballistic performance were also investigated utilizing a series of ballistic limit velocity tests. The fractured morphologies of the armor plates were observed by stereomicroscopy. Finally, the damage mechanisms of fiber reinforced polymer composites were analyzed. It is shown from the results that there is a positive correlation between the ballistic performance of UHMWPE reinforced PO resin matrix composite armor plate and the stress and modulus of UHMWPE fiber. However, the influences of fiber modulus on the ballistic performance are gradually decreased with the increase of the fiber modulus. For WPU resin matrix, the ballistic performances of the four kinds of fiber from high to low are UHMWPE fiber, Heterocyclic aramid fiber, Aramid 1414 fiber and S-glass fiber. The fiber fractured morphologies of fiber reinforced polymer armor plates are fiber shear and plugging on front surface, fiber tensile deformation and cut in middle and fiber tensile fracture on rear surface. The main middle fiber tensile deformation is the main fracture mode.
The armor plates manufactured by pressing curing process which using UHMWPE fiber, S-glass fiber, Aramid 1414 fiber or Heterocyclic aramid fiber as reinforcement and thermoplastic resin (PO or WPU) as matrix were experimentally investigated in this paper. The effects on the ballistic performance were also investigated utilizing a series of ballistic limit velocity tests. The fractured morphologies of the armor plates were observed by stereomicroscopy. Finally, the damage mechanisms of fiber reinforced polymer composites were analyzed. It is shown from the results that there is a positive correlation between the ballistic performance of UHMWPE reinforced PO resin matrix composite armor plate and the stress and modulus of UHMWPE fiber. However, the influences of fiber modulus on the ballistic performance are gradually decreased with the increase of the fiber modulus. For WPU resin matrix, the ballistic performances of the four kinds of fiber from high to low are UHMWPE fiber, Heterocyclic aramid fiber, Aramid 1414 fiber and S-glass fiber. The fiber fractured morphologies of fiber reinforced polymer armor plates are fiber shear and plugging on front surface, fiber tensile deformation and cut in middle and fiber tensile fracture on rear surface. The main middle fiber tensile deformation is the main fracture mode.
2017, 34(9): 1973-1981.
doi: 10.13801/j.cnki.fhclxb.20170112.002
Abstract:
An improved unit cell model for 3D four-directional braided composites was proposed, considering the cross-section shape variation of interior fiber bundles along their center line in manufacturing process of jamming action, and this model was further used to predict equivalence elastic constant. Firstly, based on analyzing the braiding process, interior fiber bundle distribution of unit cell was established; then, the geometric position coordinates for fiber bundle jamming regions of improved unit cell model were derived with alternately changed circular and elliptical fiber bundle cross-section, assuming the original circular cross-section is squeezed into oval shape ellipse in pinch regions, thus curling the fiber bundle paths. Mathematical relationship between braiding parameters and unit cell geometric dimensions was also deduced, with a relative calculation error for braiding pitch length less than 4% compared with test data, which is better than those models ignoring fiber bundles' deformation. Finally, equivalence elastic constants were predicted, further used to investigate the effects of braiding angle and fiber volume fracture to elastic constants.
An improved unit cell model for 3D four-directional braided composites was proposed, considering the cross-section shape variation of interior fiber bundles along their center line in manufacturing process of jamming action, and this model was further used to predict equivalence elastic constant. Firstly, based on analyzing the braiding process, interior fiber bundle distribution of unit cell was established; then, the geometric position coordinates for fiber bundle jamming regions of improved unit cell model were derived with alternately changed circular and elliptical fiber bundle cross-section, assuming the original circular cross-section is squeezed into oval shape ellipse in pinch regions, thus curling the fiber bundle paths. Mathematical relationship between braiding parameters and unit cell geometric dimensions was also deduced, with a relative calculation error for braiding pitch length less than 4% compared with test data, which is better than those models ignoring fiber bundles' deformation. Finally, equivalence elastic constants were predicted, further used to investigate the effects of braiding angle and fiber volume fracture to elastic constants.
2017, 34(9): 1982-1988.
doi: 10.13801/j.cnki.fhclxb.20161208.005
Abstract:
The mesoporous NiCo2O4 microsphere was synthesized via a facile hydrothermal method followed by thermal annealing treatment. The surface morphology, valence of the elements and electrochemical performance of the samples were characterized by FESEM, TEM, XPS and the electrochemical workstation. The results show that the as-prepared NiCo2O4 microsphere presents 3D structure constructed with rich porous nanoneedles, and deliveres a high specific surface area. The NiCo2O4 microsphere electrode reveals amazing pseudocapacitive properties with high specific capacitance (1 554 F · g-1 at 1 A · g-1) and a favorable rate capability (87.5% from 1 to 20 A · g-1) due to the 3D structure. Moreover, the specific capacitance remains 90.4% of its initial value after 2 000 cycles at 5 A · g-1. The good electrochemical performances indicate that NiCo2O4 microsphere could be a promising material for supercapacitor electrode.
The mesoporous NiCo2O4 microsphere was synthesized via a facile hydrothermal method followed by thermal annealing treatment. The surface morphology, valence of the elements and electrochemical performance of the samples were characterized by FESEM, TEM, XPS and the electrochemical workstation. The results show that the as-prepared NiCo2O4 microsphere presents 3D structure constructed with rich porous nanoneedles, and deliveres a high specific surface area. The NiCo2O4 microsphere electrode reveals amazing pseudocapacitive properties with high specific capacitance (1 554 F · g-1 at 1 A · g-1) and a favorable rate capability (87.5% from 1 to 20 A · g-1) due to the 3D structure. Moreover, the specific capacitance remains 90.4% of its initial value after 2 000 cycles at 5 A · g-1. The good electrochemical performances indicate that NiCo2O4 microsphere could be a promising material for supercapacitor electrode.
2017, 34(9): 1989-1996.
doi: 10.13801/j.cnki.fhclxb.20161226.001
Abstract:
The gradient composite Mo-Ni alloy powder with the different contents of 30-70wt%Mo and a small amount of ZrO2 were designed, the Mo-Ni-ZrO2 high temperature wear-resistant composite alloy coating were prepared on 3Cr2W8V steel by laser direct deposition technology. The microstructure, crack and pore elimination, phase composition and hardness of gradient coatings were studied by optical microscope, micro hardness tester, SEM, energy dispersive spectrometer and XRD. The results show that the MoO3 is formed in the Mo-Ni composite alloy gradient coating because molybdenum is easily oxided under the laser action, MoO3 tends to volatile when it's heated and can't escape timely in laser molten pool, so as to cracks and pores are produced in the gradient layer with 50wt%Mo, and its average microhardness is 287. The cracks and pores are reduced obviously because of ZrO2 addition in Mo-Ni-ZrO2 gradient layer with 50wt%Mo, the phase of the Mo-Ni-ZrO2 gradient layer is composed of MoNi and reinforced such as Mo1.24Ni0.76, Ni3Zr and a small amount of MoO3, its average microhardness is 477. ZrO2 has a favorable effect on elimination of the cracks and pores and improvement of the hardness in Mo-Ni high temperature gradient composite alloy coating.
The gradient composite Mo-Ni alloy powder with the different contents of 30-70wt%Mo and a small amount of ZrO2 were designed, the Mo-Ni-ZrO2 high temperature wear-resistant composite alloy coating were prepared on 3Cr2W8V steel by laser direct deposition technology. The microstructure, crack and pore elimination, phase composition and hardness of gradient coatings were studied by optical microscope, micro hardness tester, SEM, energy dispersive spectrometer and XRD. The results show that the MoO3 is formed in the Mo-Ni composite alloy gradient coating because molybdenum is easily oxided under the laser action, MoO3 tends to volatile when it's heated and can't escape timely in laser molten pool, so as to cracks and pores are produced in the gradient layer with 50wt%Mo, and its average microhardness is 287. The cracks and pores are reduced obviously because of ZrO2 addition in Mo-Ni-ZrO2 gradient layer with 50wt%Mo, the phase of the Mo-Ni-ZrO2 gradient layer is composed of MoNi and reinforced such as Mo1.24Ni0.76, Ni3Zr and a small amount of MoO3, its average microhardness is 477. ZrO2 has a favorable effect on elimination of the cracks and pores and improvement of the hardness in Mo-Ni high temperature gradient composite alloy coating.
2017, 34(9): 1997-2004.
doi: 10.13801/j.cnki.fhclxb.20161129.001
Abstract:
Mg2Si/AZ91D composites were synthesized by stirring casting method using addition different content of fly ash cenospheres to AZ91D Mg alloy substrate as raw materials. The microstructure, composition and damping capacities of the Mg2Si/AZ91D composite materials were investigated by means of optical microscope, XRD and dynamic mechanical thermal analysis. The results show that there is Mg2Si phase in the composites after adding milling cenosphere particles, compared with the Mg alloy. With the increase of mass fraction of cenosphere, Mg2Si phase shows irregular shape, and the damping capacities of the composites increase.After the solution treatment, the distribution of Mg2Si particles in Mg2Si/AZ91D composite becomes more uniform, and the damping capacities are higher than those of as-cast composite. The damping capacity of Mg2Si/AZ91D composites prepared by stirring 6 min is higher than those by stirring 3 min at both room temperature and elevated temperature. Damping capacities of Mg2Si/AZ91D composites can be explained by the G-L theory at room temperature.
Mg2Si/AZ91D composites were synthesized by stirring casting method using addition different content of fly ash cenospheres to AZ91D Mg alloy substrate as raw materials. The microstructure, composition and damping capacities of the Mg2Si/AZ91D composite materials were investigated by means of optical microscope, XRD and dynamic mechanical thermal analysis. The results show that there is Mg2Si phase in the composites after adding milling cenosphere particles, compared with the Mg alloy. With the increase of mass fraction of cenosphere, Mg2Si phase shows irregular shape, and the damping capacities of the composites increase.After the solution treatment, the distribution of Mg2Si particles in Mg2Si/AZ91D composite becomes more uniform, and the damping capacities are higher than those of as-cast composite. The damping capacity of Mg2Si/AZ91D composites prepared by stirring 6 min is higher than those by stirring 3 min at both room temperature and elevated temperature. Damping capacities of Mg2Si/AZ91D composites can be explained by the G-L theory at room temperature.
2017, 34(9): 2005-2011.
doi: 10.13801/j.cnki.fhclxb.20161202.005
Abstract:
The present study on the representative volume element (RVE) of honeycomb structures shows that, by compared with the homogeneous boundary conditions (HBCs), a more accurate result is obtained by using the periodic boundary conditions (PBCs). Based on the RVE with the PBCs, tensile tests of the self-similar hierarchical honeycombs (SSHHs) along the two in-plane directions were simulated. The effects of the porosity and the hierarchical length ratio were especially examined. The numerical results show that a large in-plane anisotropy in the SSHHs is observed. The SSHHs fails at the horizontal-links when it is subjected to a tension along the armchair direction. But when it is subjected to a tension along the zigzag direction, in case of the SSHHs with the edge of node-hexagon greater than the wall thickness and a long length of the hypotenuse-links, it will break down twice respectively at the node-hexagon and the hypotenuse-links, otherwise it breaks down once at the hypotenuse-links. It also can be seen that the tensile strength decreases with the increase of either the porosity or the hierarchical length ratio.
The present study on the representative volume element (RVE) of honeycomb structures shows that, by compared with the homogeneous boundary conditions (HBCs), a more accurate result is obtained by using the periodic boundary conditions (PBCs). Based on the RVE with the PBCs, tensile tests of the self-similar hierarchical honeycombs (SSHHs) along the two in-plane directions were simulated. The effects of the porosity and the hierarchical length ratio were especially examined. The numerical results show that a large in-plane anisotropy in the SSHHs is observed. The SSHHs fails at the horizontal-links when it is subjected to a tension along the armchair direction. But when it is subjected to a tension along the zigzag direction, in case of the SSHHs with the edge of node-hexagon greater than the wall thickness and a long length of the hypotenuse-links, it will break down twice respectively at the node-hexagon and the hypotenuse-links, otherwise it breaks down once at the hypotenuse-links. It also can be seen that the tensile strength decreases with the increase of either the porosity or the hierarchical length ratio.
2017, 34(9): 2012-2019.
doi: 10.13801/j.cnki.fhclxb.20170313.001
Abstract:
β-Sialon ceramic was prepared by high temperature nitriding reaction of raw material including Al metal powder, Si powder and α-Al2O3 fine powder. Adding different mass fractions of Y2O3 and TiO2 as sintering additive, the effect of Y3+ and Ti4+ on the composition, lattice parameters, sintering properties and microstructure of crystalline phases was studied and compared. The crystalline phases and microstructure were determined by XRD and SEM, respectively. The lattice parameters of the crystalline phases were estimated by X'Pert Plus software. The phase composition was evaluated by semi-quantification method. The results show that the addition of Y2O3 and TiO2 makes the formation temperature of β-Sialon lower obviously. Adding of Y2O3 and TiO2 has a beneficial effect on the solid solubility of Al2O3 dissolving into Si3N4, the content and the lattice parameters of β-Sialon phase increase and the sintering properties are improved. Comprehensive analysis shows that Y2O3 and TiO2 promote the sintering properties of β-Sialon ceramic, the formation of pressureless sintered β-Sialon ceramic is possible using low cost TiO2 powder instead of the conventional rare earth as sintering additives.
β-Sialon ceramic was prepared by high temperature nitriding reaction of raw material including Al metal powder, Si powder and α-Al2O3 fine powder. Adding different mass fractions of Y2O3 and TiO2 as sintering additive, the effect of Y3+ and Ti4+ on the composition, lattice parameters, sintering properties and microstructure of crystalline phases was studied and compared. The crystalline phases and microstructure were determined by XRD and SEM, respectively. The lattice parameters of the crystalline phases were estimated by X'Pert Plus software. The phase composition was evaluated by semi-quantification method. The results show that the addition of Y2O3 and TiO2 makes the formation temperature of β-Sialon lower obviously. Adding of Y2O3 and TiO2 has a beneficial effect on the solid solubility of Al2O3 dissolving into Si3N4, the content and the lattice parameters of β-Sialon phase increase and the sintering properties are improved. Comprehensive analysis shows that Y2O3 and TiO2 promote the sintering properties of β-Sialon ceramic, the formation of pressureless sintered β-Sialon ceramic is possible using low cost TiO2 powder instead of the conventional rare earth as sintering additives.
2017, 34(9): 2020-2029.
doi: 10.13801/j.cnki.fhclxb.20170103.001
Abstract:
It is important and fundamental to measure the deformations of thermal protection materials and structures under thermal and mechanical loads in the research on their mechanical properties at elevated temperature. A non-contact measuring system based on the digital image correlation method was established to realize the deformation measurement up to 800℃. Thermal deformation measurements in both out-of-plane and in-plane material orientations were conducted for the ceramic fiber reinforced SiO2 aerogel composites with the reference temperature 25℃ when the composites were heated to different temperatures in the range of 300-800℃. The results show that the deformation measuring method based on this testing system can be used to measure the high temperature deformations of these thermal protection materials. The high temperature thermal deformations of ceramic fiber reinforced SiO2 aerogel composites are obviously anisotropic. The contraction occurs in the out-of-plane direction while the expansion occurs in the in-plane direction. The main reasons resulting in the thermal deformation anisotropy could be the aggregations of particles in the SiO2 aerogel matrix and the layered distributed feature of reinforcing fibers in the in-plane direction.
It is important and fundamental to measure the deformations of thermal protection materials and structures under thermal and mechanical loads in the research on their mechanical properties at elevated temperature. A non-contact measuring system based on the digital image correlation method was established to realize the deformation measurement up to 800℃. Thermal deformation measurements in both out-of-plane and in-plane material orientations were conducted for the ceramic fiber reinforced SiO2 aerogel composites with the reference temperature 25℃ when the composites were heated to different temperatures in the range of 300-800℃. The results show that the deformation measuring method based on this testing system can be used to measure the high temperature deformations of these thermal protection materials. The high temperature thermal deformations of ceramic fiber reinforced SiO2 aerogel composites are obviously anisotropic. The contraction occurs in the out-of-plane direction while the expansion occurs in the in-plane direction. The main reasons resulting in the thermal deformation anisotropy could be the aggregations of particles in the SiO2 aerogel matrix and the layered distributed feature of reinforcing fibers in the in-plane direction.
2017, 34(9): 2030-2037.
doi: 10.13801/j.cnki.fhclxb.20170220.001
Abstract:
Various mass ratio thermoplastic polyurethane-polylactic acid (TPU-PLA) blends were prepared by melting blends. The morphology, thermal characteristics, and high-temperature processing performance of TPU-PLA blends were studied with SEM, DSC, TG, Vicat Softening Temperature (VST) and Melt Flow Rate (MFR), respectively. The results show that the morphologies of TPU and PLA in blends present as a "sea-island" distribution. Glass transition temperature Tg of the PLA in the blends changes from 69.60℃(Original PLA) to 57.58℃(PLA70), 53.29℃(PLA50) and 55.64℃(PLA30), and TPU distributes in PLA evenly as dispersing phases. There are clear interfaces between the dispersing phases and continuous phases. It indicates that TPU-PLA blends are an incompatible system. The crystallinity of original PLA is lower than that in TPU-PLA blends, due to overlapping of crystallization and melting. The initial decomposition temperature of TPU-PLA blends are around 180-200℃ and the fastest decomposition temperature of TPU-PLA are about 310-350℃. The thermal properties of TPU-PLA blends are favorable. When the mass ratio of TPU is 10%-30%, the material critical deformation temperature of blends is enhanced relatively to original PLA and TPU. The melt index of blends is increased firstly and then decreased as the mass ratio of TPU increased. As the mass ratio of TPU is 40%, the melting index of blends is highest which is 1406 g · (10 min)-1.
Various mass ratio thermoplastic polyurethane-polylactic acid (TPU-PLA) blends were prepared by melting blends. The morphology, thermal characteristics, and high-temperature processing performance of TPU-PLA blends were studied with SEM, DSC, TG, Vicat Softening Temperature (VST) and Melt Flow Rate (MFR), respectively. The results show that the morphologies of TPU and PLA in blends present as a "sea-island" distribution. Glass transition temperature Tg of the PLA in the blends changes from 69.60℃(Original PLA) to 57.58℃(PLA70), 53.29℃(PLA50) and 55.64℃(PLA30), and TPU distributes in PLA evenly as dispersing phases. There are clear interfaces between the dispersing phases and continuous phases. It indicates that TPU-PLA blends are an incompatible system. The crystallinity of original PLA is lower than that in TPU-PLA blends, due to overlapping of crystallization and melting. The initial decomposition temperature of TPU-PLA blends are around 180-200℃ and the fastest decomposition temperature of TPU-PLA are about 310-350℃. The thermal properties of TPU-PLA blends are favorable. When the mass ratio of TPU is 10%-30%, the material critical deformation temperature of blends is enhanced relatively to original PLA and TPU. The melt index of blends is increased firstly and then decreased as the mass ratio of TPU increased. As the mass ratio of TPU is 40%, the melting index of blends is highest which is 1406 g · (10 min)-1.
2017, 34(9): 2038-2046.
doi: 10.13801/j.cnki.fhclxb.20161208.001
Abstract:
Vibratory time was determined by compaction degree index using simple vibratory compaction equipment. The strength of different compaction methods were measured while the void volume of all the specimens kept approximate consistent. Then, the difference of 4 kinds of compaction methods was compared and the results were analyzed. The air void distribution, fractal dimension, the most probable diameter and average diameter was conducted by using CT scanning. Test results show that the "kneading effect" of SGC has a significant influence on ITS of cold recycled mixture using foamed asphalt (CRMF) and vibratory compaction takes the second place. However, ITS of the specimens manufactured by static compaction and Marshall compaction methods have little difference; And the UCS of four kinds of compaction methods get little difference; The distribution of fine particles is affected by using SGC and vibratory compaction methods. Thus, the air void distribution is affected by the change of fine particles distribution. The number of air voids is larger and the equivalent diameter of air voids is smaller compared with static and Marshall compaction methods. Difference of compaction mechanism between compaction methods leads to the difference of characteristics (fractal dimension, the most probable diameter and average diameter) of air void. The different characteristics of air voids, in essence, make mechanics strength of CRMF different.
Vibratory time was determined by compaction degree index using simple vibratory compaction equipment. The strength of different compaction methods were measured while the void volume of all the specimens kept approximate consistent. Then, the difference of 4 kinds of compaction methods was compared and the results were analyzed. The air void distribution, fractal dimension, the most probable diameter and average diameter was conducted by using CT scanning. Test results show that the "kneading effect" of SGC has a significant influence on ITS of cold recycled mixture using foamed asphalt (CRMF) and vibratory compaction takes the second place. However, ITS of the specimens manufactured by static compaction and Marshall compaction methods have little difference; And the UCS of four kinds of compaction methods get little difference; The distribution of fine particles is affected by using SGC and vibratory compaction methods. Thus, the air void distribution is affected by the change of fine particles distribution. The number of air voids is larger and the equivalent diameter of air voids is smaller compared with static and Marshall compaction methods. Difference of compaction mechanism between compaction methods leads to the difference of characteristics (fractal dimension, the most probable diameter and average diameter) of air void. The different characteristics of air voids, in essence, make mechanics strength of CRMF different.
2017, 34(9): 2047-2052.
doi: 10.13801/j.cnki.fhclxb.20161212.001
Abstract:
Diatomite was used as modifier to prepare diatomite-modified asphalt at different contents. The modification process and mechanism of diatomite modified asphalt were characterized by IR, SEM, OM, and a model diagram of the modification process was inferred based on the analytical results of IR, SEM and four components of asphalt. Furthermore, related performance of the diatomite-modified asphalt was examined with TG, penetration, softening point, ductility test, respectively. The results show that diatomite modified asphalt exhibits no obvious chemical change, it is showed that diatomite absorbed asphalt physically, solvent components of relatively strong liquidity and smaller molecular weight in asphalt are easily absorbed into or around diatomite for its porosity and large specific surface, they can be congealed and hardened to form a stable and homogeneous lump with diatomite when temperature decrease. This is the main reason for improvement of high temperature performance of diatomite modified asphalt. The content of diatomite is not positively related to the performance of modified asphalt. The temperature sensitivity and low temperature performance of the modified asphalt will be worse with increase content of the diatomite, the global performance of diatomite-modified asphalt is relatively good when the content is 13%.
Diatomite was used as modifier to prepare diatomite-modified asphalt at different contents. The modification process and mechanism of diatomite modified asphalt were characterized by IR, SEM, OM, and a model diagram of the modification process was inferred based on the analytical results of IR, SEM and four components of asphalt. Furthermore, related performance of the diatomite-modified asphalt was examined with TG, penetration, softening point, ductility test, respectively. The results show that diatomite modified asphalt exhibits no obvious chemical change, it is showed that diatomite absorbed asphalt physically, solvent components of relatively strong liquidity and smaller molecular weight in asphalt are easily absorbed into or around diatomite for its porosity and large specific surface, they can be congealed and hardened to form a stable and homogeneous lump with diatomite when temperature decrease. This is the main reason for improvement of high temperature performance of diatomite modified asphalt. The content of diatomite is not positively related to the performance of modified asphalt. The temperature sensitivity and low temperature performance of the modified asphalt will be worse with increase content of the diatomite, the global performance of diatomite-modified asphalt is relatively good when the content is 13%.
2017, 34(9): 2053-2060.
doi: 10.13801/j.cnki.fhclxb.20161209.001
Abstract:
The high temperature and low temperature performances of rubber modified asphalts with different viscosity reducers(1%, 2% and 3%) were studied by means of dynamic shear rheological test(DSR) and the bending creep test (BBR).The results indicate that the viscosity-reducer LP improves the high temperature performance of the rubber modified asphalt, in which the phase angle decreases and the complex modulus increases, and its high temperature performance increases gradually with the increase of viscosity reducers.Mixed with LP viscosity-reducer improves the low temperature performance of rubber powder modified asphalt, but the low temperature property decreases by the increase of viscosity-reducer dosages, which have the negative effects on improvements. The improvement effect on low temperature of viscosity agent LP to the rubber asphalts reduces with the temperature reduction, and the improvement of the low temperature performance with different dosages is similar.
The high temperature and low temperature performances of rubber modified asphalts with different viscosity reducers(1%, 2% and 3%) were studied by means of dynamic shear rheological test(DSR) and the bending creep test (BBR).The results indicate that the viscosity-reducer LP improves the high temperature performance of the rubber modified asphalt, in which the phase angle decreases and the complex modulus increases, and its high temperature performance increases gradually with the increase of viscosity reducers.Mixed with LP viscosity-reducer improves the low temperature performance of rubber powder modified asphalt, but the low temperature property decreases by the increase of viscosity-reducer dosages, which have the negative effects on improvements. The improvement effect on low temperature of viscosity agent LP to the rubber asphalts reduces with the temperature reduction, and the improvement of the low temperature performance with different dosages is similar.
2017, 34(9): 2061-2069.
doi: 10.13801/j.cnki.fhclxb.20161220.002
Abstract:
Based on the surface free energy theory, firstly, the contact angel between asphalt, aggregate and known reagent was measured, then the adhesion and peeling work and water stability index ER of asphalt-aggregate composites were calculated according to relative formulas, followed by the analyse of the change of adhesion abilities of asphalt and aggregate before and after aging. The results show that the adhesion and peeling process of asphalt-aggregate composite release heat energy to external and are spontaneous. For the composite of same asphalt and different aggregate, the rank of adhesion and resist water damage ability from strong to weak is asphalt-limestone > asphalt-basalt > asphalt-granite, and for the composite of different asphalt and same aggregate, the rank is composite modified asphalt(CM)-aggregate > rubber crumb modified asphalt(CRM)-aggregate > styrene-butadiene-styrene modified asphalt(SBSM)-aggregate. After aging, the adhesion and resist water damage ability of asphalt-aggregate composite present a decline trend and the pressure aging vessel(PAV) is more clear than rolling thin-film oven test(RTFOT), but aging process does not change the compatibility of asphalt-aggregate composite; By analyzing the SEM image of three modified asphalt after aging, it can be discovered that the interface adhesion properties between asphalt and aggregate has been changed, which results in adhesion ability decreases of asphalt and aggregate.
Based on the surface free energy theory, firstly, the contact angel between asphalt, aggregate and known reagent was measured, then the adhesion and peeling work and water stability index ER of asphalt-aggregate composites were calculated according to relative formulas, followed by the analyse of the change of adhesion abilities of asphalt and aggregate before and after aging. The results show that the adhesion and peeling process of asphalt-aggregate composite release heat energy to external and are spontaneous. For the composite of same asphalt and different aggregate, the rank of adhesion and resist water damage ability from strong to weak is asphalt-limestone > asphalt-basalt > asphalt-granite, and for the composite of different asphalt and same aggregate, the rank is composite modified asphalt(CM)-aggregate > rubber crumb modified asphalt(CRM)-aggregate > styrene-butadiene-styrene modified asphalt(SBSM)-aggregate. After aging, the adhesion and resist water damage ability of asphalt-aggregate composite present a decline trend and the pressure aging vessel(PAV) is more clear than rolling thin-film oven test(RTFOT), but aging process does not change the compatibility of asphalt-aggregate composite; By analyzing the SEM image of three modified asphalt after aging, it can be discovered that the interface adhesion properties between asphalt and aggregate has been changed, which results in adhesion ability decreases of asphalt and aggregate.
2017, 34(9): 2070-2078.
doi: 10.13801/j.cnki.fhclxb.20170117.002
Abstract:
Based on the surface free energy theory, the contact angel between asphalt, aggregate and known reagent was measurd using the contact angel measurement instrument, the adhesion and spalling work of different asphalt-aggregate systems according to relative formulas were calculated, then the adhesion work and spalling work of different asphalt-aggregate systems were compared to study the influence of different factors to asphalt-aggregate systems adhesion performance. In order to understand the influence degree of different factors to asphalt-aggregate systems adhesion performance, the grey relational analysis was conducted. The study results show that the adhesion work and spalling work are different between different asphalt-aggregate systems, in other words, the water stability is different. For the raw materials, adhesion performance is better with the increase of viscosity of asphalt and the pH of aggregate. As for the external environment influence factors, adhesion performance is worse with the increase of salt concentration and freezing-thaw cycle times, and the serious of aging level. The grey relational analysis results show that the rank from strong to weak of the influence degree in 5 influence factors is types of aggregate > types of asphalt > salt concentration > freezing-thaw cycle times > aging level. So, in road engineering, the mixture ratio design should seriously control, the asphalt with bigger viscosity and the aggregate with bigger pH should be selected, and the dosage of deicing salt should be controlled seriously.
Based on the surface free energy theory, the contact angel between asphalt, aggregate and known reagent was measurd using the contact angel measurement instrument, the adhesion and spalling work of different asphalt-aggregate systems according to relative formulas were calculated, then the adhesion work and spalling work of different asphalt-aggregate systems were compared to study the influence of different factors to asphalt-aggregate systems adhesion performance. In order to understand the influence degree of different factors to asphalt-aggregate systems adhesion performance, the grey relational analysis was conducted. The study results show that the adhesion work and spalling work are different between different asphalt-aggregate systems, in other words, the water stability is different. For the raw materials, adhesion performance is better with the increase of viscosity of asphalt and the pH of aggregate. As for the external environment influence factors, adhesion performance is worse with the increase of salt concentration and freezing-thaw cycle times, and the serious of aging level. The grey relational analysis results show that the rank from strong to weak of the influence degree in 5 influence factors is types of aggregate > types of asphalt > salt concentration > freezing-thaw cycle times > aging level. So, in road engineering, the mixture ratio design should seriously control, the asphalt with bigger viscosity and the aggregate with bigger pH should be selected, and the dosage of deicing salt should be controlled seriously.
2017, 34(9): 2079-2084.
doi: 10.13801/j.cnki.fhclxb.20161228.001
Abstract:
To get macro and micro-properties of polyphosphoric acid (PPA) modified asphalt, pure asphalt, 4 wt% styrene-butadiene-styrene blockcopolymer (SBS) modified asphalt and 2 wt% PPA modified asphalt were test by AFM and DSR based on morphology and rheology. The topography images and phase images of three types of asphalt were obtained from AFM, in which the size of "bee-like" structrue of PPA modified asphalt is a bit larger than that of pure asphalt asphalt and SBS modified asphalt, moreover, the whole image brightness of PPA modified asphalt is higher than that of pure asphalt and SBS modified asphalt. The PPA modified asphalt shows a stiffer and more uniform surface according to surface bearing index (Sbi) and the density of summits(Sds) analysis. The complex shear modulus(G*), phase angle(δ) and rutting factor(G*/sin δ) of three types of asphalt gotten from DSR indicate that PPA modified asphalt is better to resist the transformation from high temperature than the other two types of asphalt.
To get macro and micro-properties of polyphosphoric acid (PPA) modified asphalt, pure asphalt, 4 wt% styrene-butadiene-styrene blockcopolymer (SBS) modified asphalt and 2 wt% PPA modified asphalt were test by AFM and DSR based on morphology and rheology. The topography images and phase images of three types of asphalt were obtained from AFM, in which the size of "bee-like" structrue of PPA modified asphalt is a bit larger than that of pure asphalt asphalt and SBS modified asphalt, moreover, the whole image brightness of PPA modified asphalt is higher than that of pure asphalt and SBS modified asphalt. The PPA modified asphalt shows a stiffer and more uniform surface according to surface bearing index (Sbi) and the density of summits(Sds) analysis. The complex shear modulus(G*), phase angle(δ) and rutting factor(G*/sin δ) of three types of asphalt gotten from DSR indicate that PPA modified asphalt is better to resist the transformation from high temperature than the other two types of asphalt.
2017, 34(9): 2085-2092.
doi: 10.13801/j.cnki.fhclxb.20161207.003
Abstract:
To investigate the piezoresistivity mechanism and the influence factors of magneto-rheological elastomer(MRE), the conduction models and resistance expressions of isotropic and anisotropic MREs were established respectively based on their structural characteristics and the field emission theory. Further, the effects of Ni filler concentration in silicone rubber and applied voltage on the resistance were analyzed. Experiments were carried out to study the piezoresistive properties of the two MREs. MRE samples with isotropic (prepared without magnetic field) and anisotropic (pre-orientated with a magnetic field) distributions of Ni powders were prepared, respectively. The two conduction models were verified through comparison of the mapping relationships between the experimental pressure and the logarithmic resistance data. In comparison with the high impedance and low resistance range of the isotropic MRE, the anisotropic MRE changes from 106 Ω under 0 kPa to 10 Ω under 6 kPa, which presents a better feasibility in tactile sensing applications.
To investigate the piezoresistivity mechanism and the influence factors of magneto-rheological elastomer(MRE), the conduction models and resistance expressions of isotropic and anisotropic MREs were established respectively based on their structural characteristics and the field emission theory. Further, the effects of Ni filler concentration in silicone rubber and applied voltage on the resistance were analyzed. Experiments were carried out to study the piezoresistive properties of the two MREs. MRE samples with isotropic (prepared without magnetic field) and anisotropic (pre-orientated with a magnetic field) distributions of Ni powders were prepared, respectively. The two conduction models were verified through comparison of the mapping relationships between the experimental pressure and the logarithmic resistance data. In comparison with the high impedance and low resistance range of the isotropic MRE, the anisotropic MRE changes from 106 Ω under 0 kPa to 10 Ω under 6 kPa, which presents a better feasibility in tactile sensing applications.
2017, 34(9): 2093-2098.
doi: 10.13801/j.cnki.fhclxb.20161207.004
Abstract:
With Cu(NO3)2 · 3H2O and Ce(NO3)3 · 6H2O as the modifier, Cu-Ce/TiO2 was made by sol-gel method. Cu-Ce doped loading, Cu-Ce molar ratio and sintering temperature were analyzed by orthogonal design and multivariate nonlinear regression, in order to get significant of Cu-Ce/TiO2 moisture performance and photocatalytic performance. The preparation parameters of optimal Cu-Ce/TiO2 were obtained, performance and characterization of optimal Cu-Ce/TiO2 were studied and analyzed by SEM, LPSA, XRD and UV-Vis. The results showed that various factors on importance order of Cu-Ce/TiO2 moisture performance and photocatalytic performance:Cu-Ce doped loading > Cu-Ce molar ratio > sintering temperature > blank. Preparation parameters of optimal Cu-Ce/TiO2:Cu-Ce doped loading is 3.26%, Cu-Ce molar ratio is 0.87:1, sintering temperature is 505℃. Cu-Ce/TiO2 moisture performance and photocatalytic performance are 0.0869 g · g-1 and 50.7%, respectively. Cu-Ce/TiO2 morphology is better, particle size distribution is 1 183.68-3 916.05 nm, and absorption sideband occurs red shift.
With Cu(NO3)2 · 3H2O and Ce(NO3)3 · 6H2O as the modifier, Cu-Ce/TiO2 was made by sol-gel method. Cu-Ce doped loading, Cu-Ce molar ratio and sintering temperature were analyzed by orthogonal design and multivariate nonlinear regression, in order to get significant of Cu-Ce/TiO2 moisture performance and photocatalytic performance. The preparation parameters of optimal Cu-Ce/TiO2 were obtained, performance and characterization of optimal Cu-Ce/TiO2 were studied and analyzed by SEM, LPSA, XRD and UV-Vis. The results showed that various factors on importance order of Cu-Ce/TiO2 moisture performance and photocatalytic performance:Cu-Ce doped loading > Cu-Ce molar ratio > sintering temperature > blank. Preparation parameters of optimal Cu-Ce/TiO2:Cu-Ce doped loading is 3.26%, Cu-Ce molar ratio is 0.87:1, sintering temperature is 505℃. Cu-Ce/TiO2 moisture performance and photocatalytic performance are 0.0869 g · g-1 and 50.7%, respectively. Cu-Ce/TiO2 morphology is better, particle size distribution is 1 183.68-3 916.05 nm, and absorption sideband occurs red shift.
2017, 34(9): 2099-2105.
doi: 10.13801/j.cnki.fhclxb.20161207.002
Abstract:
In order to study the effects of expansive agent dosage and lateral confinement by steel tube on creep strain of concrete, 12 groups with or without lateral confinement of steel tube were conducted. The test results show that creep strain of concrete in lateral confinement by steel tube is 0.175-0.181 times of without lateral confinement at loading age to 480 days, and lateral confinement greatly reduces the creep strain of concrete. Three creep strains of concrete were tested under mass fraction of 4%, 8% and 12% expansive agent dosage. The test results show that the expansive agent dosage is the same rule of creep strain effects on concrete in both lateral confinement and without lateral confinement of the concrete structure. When admixture is 4%, the creep strain of the structure is the biggest, and when admixture is 8%, creep strain of the structure take the second place. When admixture is 12%, the creep strain of the structure is minimal. Stress ratio of concrete structure by steel tube lateral confinement is less than that without lateral confinement under the same load stress. Lateral restraint of concrete is increased by steel tube confinement, and the longitudinal deformation of concrete is confined. The smaller the stress ratio, the smaller structure creep deformation. At the same time, the mechanism of the expansion agent was analyzed by scanning electron microscopy secondary electron imaging. The final analysis conclusion is that expansive agent in cement hydration produces three sulfur type calcium sulphoaluminate(AFt) crystals which is thick stick and cross each other. The AFt crystals fill in pores that it was occupied by a solution, which makes cement denser.
In order to study the effects of expansive agent dosage and lateral confinement by steel tube on creep strain of concrete, 12 groups with or without lateral confinement of steel tube were conducted. The test results show that creep strain of concrete in lateral confinement by steel tube is 0.175-0.181 times of without lateral confinement at loading age to 480 days, and lateral confinement greatly reduces the creep strain of concrete. Three creep strains of concrete were tested under mass fraction of 4%, 8% and 12% expansive agent dosage. The test results show that the expansive agent dosage is the same rule of creep strain effects on concrete in both lateral confinement and without lateral confinement of the concrete structure. When admixture is 4%, the creep strain of the structure is the biggest, and when admixture is 8%, creep strain of the structure take the second place. When admixture is 12%, the creep strain of the structure is minimal. Stress ratio of concrete structure by steel tube lateral confinement is less than that without lateral confinement under the same load stress. Lateral restraint of concrete is increased by steel tube confinement, and the longitudinal deformation of concrete is confined. The smaller the stress ratio, the smaller structure creep deformation. At the same time, the mechanism of the expansion agent was analyzed by scanning electron microscopy secondary electron imaging. The final analysis conclusion is that expansive agent in cement hydration produces three sulfur type calcium sulphoaluminate(AFt) crystals which is thick stick and cross each other. The AFt crystals fill in pores that it was occupied by a solution, which makes cement denser.
2017, 34(9): 2106-2113.
doi: 10.13801/j.cnki.fhclxb.20161216.004
Abstract:
Heavy press frame made by prestressed carbon fiber winding was studied Carbon fiber(T700SC-12000) and titanium alloy(TC11) frame were selected as prestressed parts, New materials were applied to main parts of 25 MN die forging press and carbon fiber winding frame structure was designed. Press frame model was established according to the input parameters. Meantime, A variable tension winding was designed for the 25 MN die forging press and the results using the finite element were analyzed. The analysis results show that prestressed carbon fiber winding technology greatly improves the pre-tightening force of the protection of the beam and column of heavy press, and increases the reliability of the parts, reduces the manufacturing risk of large parts. The strength of heavy press frame made by prestressed carbon fiber winding meet the requirements, the Von Mises of the prestressed frame is 863.9 MPa and less than the yield strength of TC11. The mass loss effect is obvious, mass of press frame is decreased from 8 022 kg to 1 950.76 kg, decreased by 75.7%.
Heavy press frame made by prestressed carbon fiber winding was studied Carbon fiber(T700SC-12000) and titanium alloy(TC11) frame were selected as prestressed parts, New materials were applied to main parts of 25 MN die forging press and carbon fiber winding frame structure was designed. Press frame model was established according to the input parameters. Meantime, A variable tension winding was designed for the 25 MN die forging press and the results using the finite element were analyzed. The analysis results show that prestressed carbon fiber winding technology greatly improves the pre-tightening force of the protection of the beam and column of heavy press, and increases the reliability of the parts, reduces the manufacturing risk of large parts. The strength of heavy press frame made by prestressed carbon fiber winding meet the requirements, the Von Mises of the prestressed frame is 863.9 MPa and less than the yield strength of TC11. The mass loss effect is obvious, mass of press frame is decreased from 8 022 kg to 1 950.76 kg, decreased by 75.7%.
2017, 34(9): 2114-2120.
doi: 10.13801/j.cnki.fhclxb.20161220.005
Abstract:
Taking simply supported steel-concrete-steel sandwich beam an example, this paper focused on constructing a simplified calculation model of steel-concrete-steel sandwich beam under concentrated load, equations illustrating interface slips between steel and concrete and deformations were obtained based on proposed analysis model. The deduced equations can not only describe the deformation distribution of slipping interface, but also reflect the deformation of composite beam influenced by interface slips. The computed results using the formulas of this paper are in good agreements with the experiments results in literature. Example study shows that, as applying loads and shear connectors span increase, both of interface slips and bending deformations rise significantly.
Taking simply supported steel-concrete-steel sandwich beam an example, this paper focused on constructing a simplified calculation model of steel-concrete-steel sandwich beam under concentrated load, equations illustrating interface slips between steel and concrete and deformations were obtained based on proposed analysis model. The deduced equations can not only describe the deformation distribution of slipping interface, but also reflect the deformation of composite beam influenced by interface slips. The computed results using the formulas of this paper are in good agreements with the experiments results in literature. Example study shows that, as applying loads and shear connectors span increase, both of interface slips and bending deformations rise significantly.
