2017 Vol. 34, No. 5
2017, 34(5): 939-944.
doi: 10.13801/j.cnki.fhclxb.20160711.004
Abstract:
In order to study micro-structure and properties of composite, polyether sulfone/bismaleimide-epoxy composite was prepared by in-situ polymerization. The results of FTIR and SEM show that PES do not react chemical reaction with BMI-EP, PES is existence of two-phase structure in composite and has very strong interaction with BMI-EP matrix. PES presente as disperse phase in matrix, the interface of PES and matrix is fuzzy. The failure crack is not smooth and the direction is changed, it is typical ductile fracture when PES is added into the polymer matrix. The energy spectrum analysis show that PES is mutual penetration phenomenon with matrix and PES is uniformly dispersed in the matrix. The results of mechanical properties indicated that the toughening effect of PES resin are extremely obvious, when the content of PES is 4 wt%, the bending strength and the impact strength of PES/BMI-EP are 144.9 MPa and 19.7 kJ/m2, 41.2% and 90% higher than that of BMI-EP matrix, respectively. The thermogravimetric results prove that appropriate amount of PES can improve the heat resistance of PES/BMI-EP composite, and the excessive amount of PES resin is not conducive to the decomposition temperature of the material.
In order to study micro-structure and properties of composite, polyether sulfone/bismaleimide-epoxy composite was prepared by in-situ polymerization. The results of FTIR and SEM show that PES do not react chemical reaction with BMI-EP, PES is existence of two-phase structure in composite and has very strong interaction with BMI-EP matrix. PES presente as disperse phase in matrix, the interface of PES and matrix is fuzzy. The failure crack is not smooth and the direction is changed, it is typical ductile fracture when PES is added into the polymer matrix. The energy spectrum analysis show that PES is mutual penetration phenomenon with matrix and PES is uniformly dispersed in the matrix. The results of mechanical properties indicated that the toughening effect of PES resin are extremely obvious, when the content of PES is 4 wt%, the bending strength and the impact strength of PES/BMI-EP are 144.9 MPa and 19.7 kJ/m2, 41.2% and 90% higher than that of BMI-EP matrix, respectively. The thermogravimetric results prove that appropriate amount of PES can improve the heat resistance of PES/BMI-EP composite, and the excessive amount of PES resin is not conducive to the decomposition temperature of the material.
2017, 34(5): 945-951.
doi: 10.13801/j.cnki.fhclxb.20160706.003
Abstract:
In this study, in order to obtain nylon 66-based composites with low electrical resistivity, carbon fiber-Ni/nylon 66 composites were prepared by a plastic extruder with carbon fiber (CF) and nickel powder (Ni) as the paddings, nylon 66 as the raw resin. The relationships of the surficial modification and the fractions of CF and Ni between the electrical resistivity and mechanical properties of CF-Ni/nylon 66 composites were studied. The results show that the modification by KH550 and increasing of CF and Ni are of advantage to decrease the electric resistivity of CF-Ni/nylon 66 composites. And the electrical percolation thresholds of CF and Ni both are 20 wt%. The electric resistivity of CF-Ni/nylon 66 composite is 455 Ω·cm at the percolation thresholds, and its melting point is 202.2℃. The flexural strength and tensile strength of CF-Ni/nylon 66 composites increase firstly and decrease lately with the increasing of CF and Ni. When the fraction of Ni is 20 wt%, the flexural strength of CF-Ni/nylon 66 composite reaches to the maximum 98 MPa as the fraction of CF is 20 wt%, and the tensile strength reaches to the maximum 70 MPa as the fraction is 10 wt%. When the fraction of CF is 20 wt%, the flexural strength of CF-Ni/nylon 66 composite reaches to the maximum 120 MPa as the fraction of Ni is 30 wt%, and the tensile strength reaches to the maximum 67 MPa as the fraction is 20 wt%.
In this study, in order to obtain nylon 66-based composites with low electrical resistivity, carbon fiber-Ni/nylon 66 composites were prepared by a plastic extruder with carbon fiber (CF) and nickel powder (Ni) as the paddings, nylon 66 as the raw resin. The relationships of the surficial modification and the fractions of CF and Ni between the electrical resistivity and mechanical properties of CF-Ni/nylon 66 composites were studied. The results show that the modification by KH550 and increasing of CF and Ni are of advantage to decrease the electric resistivity of CF-Ni/nylon 66 composites. And the electrical percolation thresholds of CF and Ni both are 20 wt%. The electric resistivity of CF-Ni/nylon 66 composite is 455 Ω·cm at the percolation thresholds, and its melting point is 202.2℃. The flexural strength and tensile strength of CF-Ni/nylon 66 composites increase firstly and decrease lately with the increasing of CF and Ni. When the fraction of Ni is 20 wt%, the flexural strength of CF-Ni/nylon 66 composite reaches to the maximum 98 MPa as the fraction of CF is 20 wt%, and the tensile strength reaches to the maximum 70 MPa as the fraction is 10 wt%. When the fraction of CF is 20 wt%, the flexural strength of CF-Ni/nylon 66 composite reaches to the maximum 120 MPa as the fraction of Ni is 30 wt%, and the tensile strength reaches to the maximum 67 MPa as the fraction is 20 wt%.
2017, 34(5): 952-956.
doi: 10.13801/j.cnki.fhclxb.20160907.002
Abstract:
The graphite nanoplatelets(GnPs)-carboxylated acrylo nitrile butadiene rubber(XNBR) composites were prepared via emulsion blending by the electron beam irradiation. The effects of the irradiation dose on the emulsion stability, crosslinking degree, thermal stability, electrical performance and the morphology of GnPs-XNBR were characterized. The results show that crosslinking degree, the thermal stability and the volume resistance rate of GnPs-XNBR increase after irradiation, while the stability of the emulsion decrease obviously. The interface interaction between the rubber particles and graphite nanoplatelets and the distribution of graphite nanoplatelets in the rubber matrix are enhanced through the core-shell structure formation attributed to the irradiation, which resulte in the increment of thermal stability and dielectric constant, and also the decrement of the conductivity and dielectric loss of the GnPs-XNBR.
The graphite nanoplatelets(GnPs)-carboxylated acrylo nitrile butadiene rubber(XNBR) composites were prepared via emulsion blending by the electron beam irradiation. The effects of the irradiation dose on the emulsion stability, crosslinking degree, thermal stability, electrical performance and the morphology of GnPs-XNBR were characterized. The results show that crosslinking degree, the thermal stability and the volume resistance rate of GnPs-XNBR increase after irradiation, while the stability of the emulsion decrease obviously. The interface interaction between the rubber particles and graphite nanoplatelets and the distribution of graphite nanoplatelets in the rubber matrix are enhanced through the core-shell structure formation attributed to the irradiation, which resulte in the increment of thermal stability and dielectric constant, and also the decrement of the conductivity and dielectric loss of the GnPs-XNBR.
2017, 34(5): 957-962.
doi: 10.13801/j.cnki.fhclxb.20160825.002
Abstract:
Three kinds of SiO2 sols containing amorphous nano-silica (nano A-SiO2), spherical nano-silica (nano S-SiO2), and layered hexagonal nano-silica (nano LH-SiO2) particles were controllably synthesized by tailoring the hydrolysis of sodium silicate. By in-situ reaction between SiO2 sols and hydrophilic polyurethane (HPU) prepolymer, synthesizing from diisocyanate and polyether polyol, a series of nano-silica modified hydrophilic polyurethane composites (nano SiO2/HPU) were obtained. The structure and properties of HPU and nano SiO2/HPU were characterized by ATR-FTIR, TEM, SEM and mechanical properties. The results show that PEG plays a regulating role in the formation of nano-silica particles in SiO2 sol, and the morphology of nano-silica particles affects the mechanical properties of nano SiO2/HPU grouting composites differently. Specifically, nano S-SiO2/HPU exhibits higher compression strength, and nano LH-SiO2/HPU possesses better toughness.
Three kinds of SiO2 sols containing amorphous nano-silica (nano A-SiO2), spherical nano-silica (nano S-SiO2), and layered hexagonal nano-silica (nano LH-SiO2) particles were controllably synthesized by tailoring the hydrolysis of sodium silicate. By in-situ reaction between SiO2 sols and hydrophilic polyurethane (HPU) prepolymer, synthesizing from diisocyanate and polyether polyol, a series of nano-silica modified hydrophilic polyurethane composites (nano SiO2/HPU) were obtained. The structure and properties of HPU and nano SiO2/HPU were characterized by ATR-FTIR, TEM, SEM and mechanical properties. The results show that PEG plays a regulating role in the formation of nano-silica particles in SiO2 sol, and the morphology of nano-silica particles affects the mechanical properties of nano SiO2/HPU grouting composites differently. Specifically, nano S-SiO2/HPU exhibits higher compression strength, and nano LH-SiO2/HPU possesses better toughness.
2017, 34(5): 963-969.
doi: 10.13801/j.cnki.fhclxb.20160801.001
Abstract:
Mesoporous molecular sieve(MCM-41) and Cr2O3 were used on intumescent flame retardant (IFR) to flame retardant natural rubber(NR). In order to study the flame retardant synergistic effects of MCM-41 and Cr2O3, two synergists of different components and IFR were used to flame retardant natural rubber(NR). The oxygen index test, thermogravimetric analysis, cone calorimetric analysis, tensile test and the analysis of the residual carbon scanning were investigated for the flame retardant system. The results show that when only expansion flame retardant system is added to the natural rubber, the mechanical properties of the flame retardant system are dropped dramatically and the thermal performance almost have no improvement. While tensile strength and elongation at break of the composites are improved with the increase of Cr2O3 and MCM-41. The IFR-MCM-41-Cr2O3 composite flame retardant effect achieves the best when IFR content is 36% (mass ratio to the natural rubber), MCM-41 content is 1%, Cr2O3 content is 3%. And the peak value of heat release rate and total heat release of burning decrease significantly. The IFR-MCM-41-Cr2O3/NR composites could form compact charred layer after burning. The limiting oxygen index (LOI) can reach 26.5% and the vertical combustion (UL-94) is V-0 level.
Mesoporous molecular sieve(MCM-41) and Cr2O3 were used on intumescent flame retardant (IFR) to flame retardant natural rubber(NR). In order to study the flame retardant synergistic effects of MCM-41 and Cr2O3, two synergists of different components and IFR were used to flame retardant natural rubber(NR). The oxygen index test, thermogravimetric analysis, cone calorimetric analysis, tensile test and the analysis of the residual carbon scanning were investigated for the flame retardant system. The results show that when only expansion flame retardant system is added to the natural rubber, the mechanical properties of the flame retardant system are dropped dramatically and the thermal performance almost have no improvement. While tensile strength and elongation at break of the composites are improved with the increase of Cr2O3 and MCM-41. The IFR-MCM-41-Cr2O3 composite flame retardant effect achieves the best when IFR content is 36% (mass ratio to the natural rubber), MCM-41 content is 1%, Cr2O3 content is 3%. And the peak value of heat release rate and total heat release of burning decrease significantly. The IFR-MCM-41-Cr2O3/NR composites could form compact charred layer after burning. The limiting oxygen index (LOI) can reach 26.5% and the vertical combustion (UL-94) is V-0 level.
2017, 34(5): 970-977.
doi: 10.13801/j.cnki.fhclxb.20161010.001
Abstract:
A typical body structure B-pillar was selected as the research object. Experiment and simulation analysis were used to investigate its optimization design method for resin transfer molding method (RTM) process. The injection mode was optimized by control the resin flow front, which could reduce the porosity and ensure the quality of the part. Firstly, the self-manufactured variable thickness permeability test mold was used to obtain the selected fabric permeability, then the robustness of the adopted simulation method and the obtained permeability data were verified by comparing the vacuum-assisted RTM experiments with the virtual simulations. Finally, combing the filing cycle and the porosity controlling theory, the optimal design of the injection port distribution and injection modes of RTM forming process were investigated. The results show that, for the selected automotive structure, the parts with the injection of optimized injection rate acquire the lowest porosity, but their filling cycles are too long, then the injection of a constant flow rate and two injection ports can better take into account the requirement of both the filling cycle and part porosity.
A typical body structure B-pillar was selected as the research object. Experiment and simulation analysis were used to investigate its optimization design method for resin transfer molding method (RTM) process. The injection mode was optimized by control the resin flow front, which could reduce the porosity and ensure the quality of the part. Firstly, the self-manufactured variable thickness permeability test mold was used to obtain the selected fabric permeability, then the robustness of the adopted simulation method and the obtained permeability data were verified by comparing the vacuum-assisted RTM experiments with the virtual simulations. Finally, combing the filing cycle and the porosity controlling theory, the optimal design of the injection port distribution and injection modes of RTM forming process were investigated. The results show that, for the selected automotive structure, the parts with the injection of optimized injection rate acquire the lowest porosity, but their filling cycles are too long, then the injection of a constant flow rate and two injection ports can better take into account the requirement of both the filling cycle and part porosity.
2017, 34(5): 978-986.
doi: 10.13801/j.cnki.fhclxb.20160823.002
Abstract:
Based on the analysis of the degree of cure and temperature dependent viscoelastic constitutive model of composite, the dimensionless parameters defined as Dem were proposed to characterize the viscoelasticity of composite in this paper. The parameters Dem can comprehensively reflect the effects of the degree of cure and temperature on the viscoelasticity of a composite during cure. When all of the values of Dem are higher than 102, the composite matrix is in a flow state. When all of the values of Dem are less than 10-2, the composite is in an elastic state. Only when one or more Dem lie between 102 and 10-2, the composite is in viscoelastic state. The behavior of the AS4 fiber/3501-6 polymer matrix composite was used as example, the development of the viscoelasticity of the composite was analyzed according to the evolution of the parameters Dem during the typical curing cycle. The result shows that the gelation time determined by the parameters Dem is consistent with that obtained by experimental tests. According to the effect of viscoelasticity of composite on the accumulation of residual stress, the analysis procedure on the residual stress was divided into the flow stage and the viscoelasticity stage, and the cure state dependent viscoelastic constitutive models were put forward. The proposed models were verified by comparing their predictions with those of the original constitutive model. The results show that the residual stresses predicted by the proposed models are consistent with those predicted by the original model, but the computing time and storage space required by the proposed models are greatly reduced.
Based on the analysis of the degree of cure and temperature dependent viscoelastic constitutive model of composite, the dimensionless parameters defined as Dem were proposed to characterize the viscoelasticity of composite in this paper. The parameters Dem can comprehensively reflect the effects of the degree of cure and temperature on the viscoelasticity of a composite during cure. When all of the values of Dem are higher than 102, the composite matrix is in a flow state. When all of the values of Dem are less than 10-2, the composite is in an elastic state. Only when one or more Dem lie between 102 and 10-2, the composite is in viscoelastic state. The behavior of the AS4 fiber/3501-6 polymer matrix composite was used as example, the development of the viscoelasticity of the composite was analyzed according to the evolution of the parameters Dem during the typical curing cycle. The result shows that the gelation time determined by the parameters Dem is consistent with that obtained by experimental tests. According to the effect of viscoelasticity of composite on the accumulation of residual stress, the analysis procedure on the residual stress was divided into the flow stage and the viscoelasticity stage, and the cure state dependent viscoelastic constitutive models were put forward. The proposed models were verified by comparing their predictions with those of the original constitutive model. The results show that the residual stresses predicted by the proposed models are consistent with those predicted by the original model, but the computing time and storage space required by the proposed models are greatly reduced.
2017, 34(5): 987-995.
doi: 10.13801/j.cnki.fhclxb.20160713.002
Abstract:
A 3D finite element model was developed in this work by considering damage modes like matrix cracking, fiber breakage, intra-ply splitting and inter-ply delamination. The notch size effect and notch shape effect of tensile quasi-isotropic composite laminates ([45/0/-45/90]2S) with central holes and central cracks were studied by the finite element model. The simulation results indicate that the damage strength of the laminates decreases with the increasing of notch size. However, the laminates with central cracks always show higher damage strengths than those with corresponding central holes for the laminates studied in this paper. A further investigation of the finite element simulation results shows that subcritical damage forms earlier in cracked laminates with larger subcritical damage zones. The subcritical damage will significantly alleviate the stress concentration at the notch tip, and therefore make the cracked laminates exhibit higher damage strengths.
A 3D finite element model was developed in this work by considering damage modes like matrix cracking, fiber breakage, intra-ply splitting and inter-ply delamination. The notch size effect and notch shape effect of tensile quasi-isotropic composite laminates ([45/0/-45/90]2S) with central holes and central cracks were studied by the finite element model. The simulation results indicate that the damage strength of the laminates decreases with the increasing of notch size. However, the laminates with central cracks always show higher damage strengths than those with corresponding central holes for the laminates studied in this paper. A further investigation of the finite element simulation results shows that subcritical damage forms earlier in cracked laminates with larger subcritical damage zones. The subcritical damage will significantly alleviate the stress concentration at the notch tip, and therefore make the cracked laminates exhibit higher damage strengths.
2017, 34(5): 996-1002.
doi: 10.13801/j.cnki.fhclxb.20160906.003
Abstract:
In the manufacturing process of composite structures for commercial aircraft, peel ply surface treatment for co-bonding and secondary bonding of composites is becoming more common and gradually substitutes the traditional method such as grinding. And it is found that potential matching exists between different peel plies and composite resin systems in practical application. As a result, varied bonding properties were observed on composite surface with different peel plies after treatments. In order to study the effects of peel ply on the bonding performance, T300/Cycom 970 epoxy resin composite laminates were fabricated using the autoclave process. First, four peel plies and an adhesive film for commercial aircraft were chosen for surface treatment and bonding, respectively. Second, the structure properties of T300/Cycom 970 epoxy laminate specimens after bonding were tested by stripping tests and single lap shear tests according to the ASTM standards. Finally, contact angle test, scanning electron microscopy (SEM) and X-Ray Photo Spectroscopy (XPS) were applied to characterize the surface wettability, morphology and element analysis for composite laminates and peel plies. The results show that the bond quality of the T300/Cycom 970 epoxy composite sample which are treated with polyester wet peel ply is the best, and the residual of peel plies fabric and coating has negative effect on the T300/Cycom 970 epoxy composite bonding performance. Although peel ply surface treatment can improve the surface wettability and the surface energy, the improvement of wettability cannot guarantee the bond quality. T300/Cycom 970 epoxy composite surface topography and roughness are affected directly by peel ply weave pattern, which produce an effect on the bond quality of the composites.
In the manufacturing process of composite structures for commercial aircraft, peel ply surface treatment for co-bonding and secondary bonding of composites is becoming more common and gradually substitutes the traditional method such as grinding. And it is found that potential matching exists between different peel plies and composite resin systems in practical application. As a result, varied bonding properties were observed on composite surface with different peel plies after treatments. In order to study the effects of peel ply on the bonding performance, T300/Cycom 970 epoxy resin composite laminates were fabricated using the autoclave process. First, four peel plies and an adhesive film for commercial aircraft were chosen for surface treatment and bonding, respectively. Second, the structure properties of T300/Cycom 970 epoxy laminate specimens after bonding were tested by stripping tests and single lap shear tests according to the ASTM standards. Finally, contact angle test, scanning electron microscopy (SEM) and X-Ray Photo Spectroscopy (XPS) were applied to characterize the surface wettability, morphology and element analysis for composite laminates and peel plies. The results show that the bond quality of the T300/Cycom 970 epoxy composite sample which are treated with polyester wet peel ply is the best, and the residual of peel plies fabric and coating has negative effect on the T300/Cycom 970 epoxy composite bonding performance. Although peel ply surface treatment can improve the surface wettability and the surface energy, the improvement of wettability cannot guarantee the bond quality. T300/Cycom 970 epoxy composite surface topography and roughness are affected directly by peel ply weave pattern, which produce an effect on the bond quality of the composites.
2017, 34(5): 1003-1008.
doi: 10.13801/j.cnki.fhclxb.20160711.005
Abstract:
Many efforts had been made aiming at the issue of lower mechanical performance of domestic aramid paper composites, which made of meta-aramid fibers and fibrids. In the present work, the aramid paper composites were prepared with para-aramid (1414) chopped fibers and meta-aramid (1313) fibrids, abbreviated as 1414/1313 paper. The hot-pressing characteristics and strength properties of the aramid sheets under various temperatures were investigated. The variations of internal structure in aramid paper composites were characterized by using SEM and FTIR. The effects of hot-pressing temperature on interactions and inter-binding features between the fibers and fibrids were studied. The results show that a favorable bond feature between the chopped fibers and fibrids is formed when the papers were hot pressed at 280℃, 15 MPa for 6 min. A maximum tensile index of 212.2 N·m·g-1 with paper porosity of 23.21% occurs, which may about twice that of the commercial T410 Nomex paper. In addition, the FTIR spectrum results verify that no new chemical bonds are formed with the increase of hot pressing temperature, but the significant strength increase of intermolecular hydrogen bond association, which is the main cause of paper mechanical properties improvement.
Many efforts had been made aiming at the issue of lower mechanical performance of domestic aramid paper composites, which made of meta-aramid fibers and fibrids. In the present work, the aramid paper composites were prepared with para-aramid (1414) chopped fibers and meta-aramid (1313) fibrids, abbreviated as 1414/1313 paper. The hot-pressing characteristics and strength properties of the aramid sheets under various temperatures were investigated. The variations of internal structure in aramid paper composites were characterized by using SEM and FTIR. The effects of hot-pressing temperature on interactions and inter-binding features between the fibers and fibrids were studied. The results show that a favorable bond feature between the chopped fibers and fibrids is formed when the papers were hot pressed at 280℃, 15 MPa for 6 min. A maximum tensile index of 212.2 N·m·g-1 with paper porosity of 23.21% occurs, which may about twice that of the commercial T410 Nomex paper. In addition, the FTIR spectrum results verify that no new chemical bonds are formed with the increase of hot pressing temperature, but the significant strength increase of intermolecular hydrogen bond association, which is the main cause of paper mechanical properties improvement.
2017, 34(5): 1009-1015.
doi: 10.13801/j.cnki.fhclxb.20160715.003
Abstract:
To improve the bioactivity of β -type Ti-Nb-Zr alloy, 20 wt% CPP (calcium pyrophosphate) was added as bio-ceramic, and then the 20CPP/Ti-35Nb-7Zr composites were fabricated by spark plasma sintering (SPS) technology. The study was focus on microstructure and mechanical properties of the composites sintered at different temperatures (1 000-1 200℃). The influence mechanism of microstructure evolution on the mechanical properties was revealed. Results show that the composites are consisted of β -Ti phase matrix, a little residual α -Ti phase and metal-ceramic phases (CaO, Ti2O, CaTiO3, CaZrO3 and TixPy). With increasing sintering temperature, the β -Ti phase and metal-ceramic phase increase gradually. The changes of metal-ceramic phases from particle-like precipitate to a continuous network structure are caused by the fierce reaction between metal and ceramic, which separates the matrix. Compressive elastic moduli and compressive strength of 20CPP/Ti-35Nb-7Zr composites present substantial increases (64.0 to 71.4 GPa) with increase of sintering temperature due to the morphological changes of metal-ceramic phases. Therefore, it will be beneficial to improving mechanical properties by controlling the morphological structure of metal-ceramic phases in 20CPP/Ti-Nb-Zr composite.
To improve the bioactivity of β -type Ti-Nb-Zr alloy, 20 wt% CPP (calcium pyrophosphate) was added as bio-ceramic, and then the 20CPP/Ti-35Nb-7Zr composites were fabricated by spark plasma sintering (SPS) technology. The study was focus on microstructure and mechanical properties of the composites sintered at different temperatures (1 000-1 200℃). The influence mechanism of microstructure evolution on the mechanical properties was revealed. Results show that the composites are consisted of β -Ti phase matrix, a little residual α -Ti phase and metal-ceramic phases (CaO, Ti2O, CaTiO3, CaZrO3 and TixPy). With increasing sintering temperature, the β -Ti phase and metal-ceramic phase increase gradually. The changes of metal-ceramic phases from particle-like precipitate to a continuous network structure are caused by the fierce reaction between metal and ceramic, which separates the matrix. Compressive elastic moduli and compressive strength of 20CPP/Ti-35Nb-7Zr composites present substantial increases (64.0 to 71.4 GPa) with increase of sintering temperature due to the morphological changes of metal-ceramic phases. Therefore, it will be beneficial to improving mechanical properties by controlling the morphological structure of metal-ceramic phases in 20CPP/Ti-Nb-Zr composite.
Influence of high pressure torsion on microstructure and mechanical properties of SiCP/Al composites
2017, 34(5): 1016-1022.
doi: 10.13801/j.cnki.fhclxb.20160707.001
Abstract:
In order to research the influence of severe plastic deformation on microstructure and mechanical properties of metal matrix composites, powder mixture of pure Al and oxidized SiC were consolidated into 10 wt% (mass fraction) SiCP/Al composites at 200℃ by high-pressure torsion(HPT). The Al microstructure and SiC-Al interface of different torsion numbers were studied by TEM. The energy dispersive spectrometer(EDS) was used to analysis the elements diffusion. The mechanical properties of different torsion numbers were studied by universal testing machine. The results show that there are a large number of lattice defect in Al matrix after deformation of different torsion numbers, such as dislocation and non-equilibrium grain boundary. There are two different SiC-Al interface which is the SiC-Al interface with SiO2 layer and new interface that formes between Al matrix and broken SiC particles. SiC-Al bonding is good and elements mutually diffuse at the interface. The tensile strength of 10 wt% SiCP/Al is increased significantly and the elongation is greatly improved with the increase of torsion numbers. The analysis shows that a large number of lattice defects and fine grains are produced in the samples after deformation of different torsion numbers. The lattice defects and fine grains enhance the elements diffusion and make the interface bonding better. Lattice defects and better interface are the main reasons that the mechanical properties of 10 wt% SiCP/Al are greatly improved.
In order to research the influence of severe plastic deformation on microstructure and mechanical properties of metal matrix composites, powder mixture of pure Al and oxidized SiC were consolidated into 10 wt% (mass fraction) SiCP/Al composites at 200℃ by high-pressure torsion(HPT). The Al microstructure and SiC-Al interface of different torsion numbers were studied by TEM. The energy dispersive spectrometer(EDS) was used to analysis the elements diffusion. The mechanical properties of different torsion numbers were studied by universal testing machine. The results show that there are a large number of lattice defect in Al matrix after deformation of different torsion numbers, such as dislocation and non-equilibrium grain boundary. There are two different SiC-Al interface which is the SiC-Al interface with SiO2 layer and new interface that formes between Al matrix and broken SiC particles. SiC-Al bonding is good and elements mutually diffuse at the interface. The tensile strength of 10 wt% SiCP/Al is increased significantly and the elongation is greatly improved with the increase of torsion numbers. The analysis shows that a large number of lattice defects and fine grains are produced in the samples after deformation of different torsion numbers. The lattice defects and fine grains enhance the elements diffusion and make the interface bonding better. Lattice defects and better interface are the main reasons that the mechanical properties of 10 wt% SiCP/Al are greatly improved.
2017, 34(5): 1023-1033.
doi: 10.13801/j.cnki.fhclxb.20160926.002
Abstract:
In this paper, the problem of thermal buckling of thin spherical shells of functionally graded materials composed of metal and ceramics was studied. The stability equation of axisymmetric spherical shell was derived by the tensor method. The thermal constitutive equation was applied to the stability equation of the spherical shell, and the thermal buckling equations of the spherical shell were obtained. The effects of external pressure and temperature were considered. The thermal buckling of simply supported spherical shell was studied by using Galerkin method.The change tendency of the critical pressure and the critical pressure of the thickness of the thin shell and the change of the physical parameters were analyzed.With the change of the thickness, physical property parameter, temperature difference between inside and outside surface, the change tendency of the critical temperature and the change of the critical pressure were presented.
In this paper, the problem of thermal buckling of thin spherical shells of functionally graded materials composed of metal and ceramics was studied. The stability equation of axisymmetric spherical shell was derived by the tensor method. The thermal constitutive equation was applied to the stability equation of the spherical shell, and the thermal buckling equations of the spherical shell were obtained. The effects of external pressure and temperature were considered. The thermal buckling of simply supported spherical shell was studied by using Galerkin method.The change tendency of the critical pressure and the critical pressure of the thickness of the thin shell and the change of the physical parameters were analyzed.With the change of the thickness, physical property parameter, temperature difference between inside and outside surface, the change tendency of the critical temperature and the change of the critical pressure were presented.
2017, 34(5): 1034-1039.
doi: 10.13801/j.cnki.fhclxb.20160918.001
Abstract:
The MoSi2/Al2O3 ceramic composites were prepared by the reaction sintering process, in which the metal Mo, Si and Al powder as the raw material in order to effectively enhance the room temperature toughness and strength of MoSi/Al2O3 composite, and to reveal the resistivity with the purpose of sintering temperature variation. The samples' phase composition and microstructure, sintered at different temperatures, were investigated by SEM and XRD, and the mechanical properties and resistivity were investigated. The experimental results indicate that the MoSi2/Al2O3 ceramic composite shows good performance in the argon protect atmosphere at 1 200℃. The apparent porosity is 20.7%, the volume density is 4.8 g/cm3, the fracture toughness value is 9.72 MPa·m1/2, and the resistivity is 6.0×10-2 Ω·cm. MoSi2/Al2O3 composite structure is mainly formed by Al2O3 cladding and MoSi2 continuous cladding phase composition. The organizational structure is symmetrical. When the sintering temperature is 1 200℃, MoSi2 conductive phase connects each other to shape interconnected network distribution, and the cladding layer of Al2O3 coated MoSi2 conductive phase become thinner, MoSi2 phase can easy to break the Al2O3 cladding phase to communicate with each other, which is contribute to reduce the resistivity.
The MoSi2/Al2O3 ceramic composites were prepared by the reaction sintering process, in which the metal Mo, Si and Al powder as the raw material in order to effectively enhance the room temperature toughness and strength of MoSi/Al2O3 composite, and to reveal the resistivity with the purpose of sintering temperature variation. The samples' phase composition and microstructure, sintered at different temperatures, were investigated by SEM and XRD, and the mechanical properties and resistivity were investigated. The experimental results indicate that the MoSi2/Al2O3 ceramic composite shows good performance in the argon protect atmosphere at 1 200℃. The apparent porosity is 20.7%, the volume density is 4.8 g/cm3, the fracture toughness value is 9.72 MPa·m1/2, and the resistivity is 6.0×10-2 Ω·cm. MoSi2/Al2O3 composite structure is mainly formed by Al2O3 cladding and MoSi2 continuous cladding phase composition. The organizational structure is symmetrical. When the sintering temperature is 1 200℃, MoSi2 conductive phase connects each other to shape interconnected network distribution, and the cladding layer of Al2O3 coated MoSi2 conductive phase become thinner, MoSi2 phase can easy to break the Al2O3 cladding phase to communicate with each other, which is contribute to reduce the resistivity.
2017, 34(5): 1040-1047.
doi: 10.13801/j.cnki.fhclxb.20160829.001
Abstract:
ZrC-SiC-C/C composites were fabricated by precursor infiltration and pyrolysis method (PIP) using the C/C with a low density as performs. The microstructure and ablation performance of the composites were investigated, and the anti-oxidant ablation behavior was discussed, particularly. The results show that ZrC-SiC dual ceramic phases are dispersed in the matrix, and a good interface between different phases is obtained; ZrC-SiC-C/C composites have an excellent anti-oxidant ablation performance. After ablation at 2 200℃ for 120 s by plasma flame, the linear and mass ablation rates of composites are 1.67×10-4 mm·s-1 and 6.04×10-4 g·s-1, respectively. When the ablation temperature is 2 200℃, ZrO2-SiO2 binary eutectic systemas a oxide film is formed on the surface, which can effectively prevent the infiltration of oxidation atmosphere, and reduce the denudation of flame on the material. When the ablation temperature rises to 2 500℃, aoxide membrane structure with the ZrO2 as the outer layer and ZrO2-SiO2 binary eutectic system as the inner layer is generated on the surface. ZrO2 layer can inhibit heat transmitting into interior, which contributes to form a dense oxide layer at the bottom.
ZrC-SiC-C/C composites were fabricated by precursor infiltration and pyrolysis method (PIP) using the C/C with a low density as performs. The microstructure and ablation performance of the composites were investigated, and the anti-oxidant ablation behavior was discussed, particularly. The results show that ZrC-SiC dual ceramic phases are dispersed in the matrix, and a good interface between different phases is obtained; ZrC-SiC-C/C composites have an excellent anti-oxidant ablation performance. After ablation at 2 200℃ for 120 s by plasma flame, the linear and mass ablation rates of composites are 1.67×10-4 mm·s-1 and 6.04×10-4 g·s-1, respectively. When the ablation temperature is 2 200℃, ZrO2-SiO2 binary eutectic systemas a oxide film is formed on the surface, which can effectively prevent the infiltration of oxidation atmosphere, and reduce the denudation of flame on the material. When the ablation temperature rises to 2 500℃, aoxide membrane structure with the ZrO2 as the outer layer and ZrO2-SiO2 binary eutectic system as the inner layer is generated on the surface. ZrO2 layer can inhibit heat transmitting into interior, which contributes to form a dense oxide layer at the bottom.
2017, 34(5): 1048-1053.
doi: 10.13801/j.cnki.fhclxb.20170222.003
Abstract:
Effect of co-doping V5+-Sr2+ on the properties of TiO2 varistors ceramic was studied. V5+-Sr2+ co-doped TiO2 samples were prepared by adopting the solid phase sintering method. XRD and SEM were carried out to measured the microstructure and chemical composition of V5+-Sr2+ co-doping TiO2. Based on different sintering temperatures and V5+-Sr2+ co-doping content, electrical properties of V5+-Sr2+ were tested out by using the parameters instrument. The results show that secondary phase is observed in V5+-Sr2+ doped TiO2 samples when the V2O5 doped amount is 0.35 mol%. With SrCO3 doping content and sintering temperature increasing, varistor voltage and nonlinear coefficient of V5+-Sr2+ co-doped TiO2 samples present different trends to change. 0.5 mol% Sr2+ doped samples sintered at 1 300℃ possess the optimal properties with a voltage of 16.3 V/mm and a nonlinear coefficient of 5.6.
Effect of co-doping V5+-Sr2+ on the properties of TiO2 varistors ceramic was studied. V5+-Sr2+ co-doped TiO2 samples were prepared by adopting the solid phase sintering method. XRD and SEM were carried out to measured the microstructure and chemical composition of V5+-Sr2+ co-doping TiO2. Based on different sintering temperatures and V5+-Sr2+ co-doping content, electrical properties of V5+-Sr2+ were tested out by using the parameters instrument. The results show that secondary phase is observed in V5+-Sr2+ doped TiO2 samples when the V2O5 doped amount is 0.35 mol%. With SrCO3 doping content and sintering temperature increasing, varistor voltage and nonlinear coefficient of V5+-Sr2+ co-doped TiO2 samples present different trends to change. 0.5 mol% Sr2+ doped samples sintered at 1 300℃ possess the optimal properties with a voltage of 16.3 V/mm and a nonlinear coefficient of 5.6.
2017, 34(5): 1054-1061.
doi: 10.13801/j.cnki.fhclxb.20160711.008
Abstract:
Edgewise compression experiments were conducted at different temperatures for the stitched aerogel-core sandwich composite, and the edgewise compression mechanical properties were investigated at RT, 300℃, 600℃ and 800℃, respectively. Micro-focus industrial computed tomography (Micro-CT) technology was adopted to scan the internal structure of the composite. And combined with FEM analysis method, edgewise compression failure mechanisms were discussed. The results reveal that in the case of edgewise compression, the composite has ultimate load. The local buckling of the panel, shear failure of the core and crush of the stitches are the main damage mechanisms of the specimens. With the increasing temperature, the edgewise compression modulus and the ultimate stress increase, and the fracture mode of the panel trends to be brittle. The compression modulus of 300℃, 600℃ and 800℃ is about 1.05 times, 1.57 times and 1.65 times that of room temperature, respectively, and the ultimate strength is 1.14 times, 1.46 times and 1.67 times that of room temperature, respectively. The comparison of finite element analysis results and the experimental results at room temperature shows that the failure mode of the stitched aerogel-core sandwich composite is reasonable.
Edgewise compression experiments were conducted at different temperatures for the stitched aerogel-core sandwich composite, and the edgewise compression mechanical properties were investigated at RT, 300℃, 600℃ and 800℃, respectively. Micro-focus industrial computed tomography (Micro-CT) technology was adopted to scan the internal structure of the composite. And combined with FEM analysis method, edgewise compression failure mechanisms were discussed. The results reveal that in the case of edgewise compression, the composite has ultimate load. The local buckling of the panel, shear failure of the core and crush of the stitches are the main damage mechanisms of the specimens. With the increasing temperature, the edgewise compression modulus and the ultimate stress increase, and the fracture mode of the panel trends to be brittle. The compression modulus of 300℃, 600℃ and 800℃ is about 1.05 times, 1.57 times and 1.65 times that of room temperature, respectively, and the ultimate strength is 1.14 times, 1.46 times and 1.67 times that of room temperature, respectively. The comparison of finite element analysis results and the experimental results at room temperature shows that the failure mode of the stitched aerogel-core sandwich composite is reasonable.
2017, 34(5): 1062-1068.
doi: 10.13801/j.cnki.fhclxb.20160825.003
Abstract:
V-N co-doped TiO2/glass beads photocatalytic composites were synthesized by sol-gel method. The effects of several preparation condition, such as V-N co-doped TiO2(V-N-TiO2) concentration, V-N-TiO2/glass beads dipping times, glass beads size and calcination temperature were studied. The V-N-TiO2/glass beads photocatalytic composites were characterized by TEM, EDS, XRD, XPS and their photocatalytic properties for phenol degradation were investigated. The result shows that the V-N-TiO2/glass beads composite with 2%V-N-TiO2 and 2~3 mm glass beads, dipping for 4 times, calcinating at 400℃ for 4.5 h, exhibits the best photocatalytic performance. Moreover, the degradation amount of phenol per the V-N-TiO2/glass beads composite is slightly higher than V-N-TiO2. The prepared V-N-TiO2/glass beads composite reveals good photocatalytic performance and stability of recycle.
V-N co-doped TiO2/glass beads photocatalytic composites were synthesized by sol-gel method. The effects of several preparation condition, such as V-N co-doped TiO2(V-N-TiO2) concentration, V-N-TiO2/glass beads dipping times, glass beads size and calcination temperature were studied. The V-N-TiO2/glass beads photocatalytic composites were characterized by TEM, EDS, XRD, XPS and their photocatalytic properties for phenol degradation were investigated. The result shows that the V-N-TiO2/glass beads composite with 2%V-N-TiO2 and 2~3 mm glass beads, dipping for 4 times, calcinating at 400℃ for 4.5 h, exhibits the best photocatalytic performance. Moreover, the degradation amount of phenol per the V-N-TiO2/glass beads composite is slightly higher than V-N-TiO2. The prepared V-N-TiO2/glass beads composite reveals good photocatalytic performance and stability of recycle.
2017, 34(5): 1069-1074.
doi: 10.13801/j.cnki.fhclxb.20160711.003
Abstract:
In order to explore the effect of surface modification on pore structure and thermal-electric energy conversion of activated carbon, activated carbons were first modified by surface treatment using HNO3 and KOH under different conditions. The pore structure and graphitic-type structure of the activated carbons were characterized by N2 adsorption and XRD. The specific surface area and pore volume of the activated carbon are significantly increased by the surface treatments, while the average pore size and presence of graphite crystal structure are slightly affected. For the dry modification method, the specific surface area and pore volume are increased from 1 077.880 m2/g and 0.763 cm3/g to 1 635.268 m2/g and 1.128 cm3/g, respectively. Furthermore, after modification, the micropore volume is increased and the impurities of the activated carbon are removed. The performance of thermal-electric energy conversion of the activated carbon is tested by using the activated carbon as solid electrode materials and KCl solution as electrolyte, which shows the treated activated carbon has better performance.
In order to explore the effect of surface modification on pore structure and thermal-electric energy conversion of activated carbon, activated carbons were first modified by surface treatment using HNO3 and KOH under different conditions. The pore structure and graphitic-type structure of the activated carbons were characterized by N2 adsorption and XRD. The specific surface area and pore volume of the activated carbon are significantly increased by the surface treatments, while the average pore size and presence of graphite crystal structure are slightly affected. For the dry modification method, the specific surface area and pore volume are increased from 1 077.880 m2/g and 0.763 cm3/g to 1 635.268 m2/g and 1.128 cm3/g, respectively. Furthermore, after modification, the micropore volume is increased and the impurities of the activated carbon are removed. The performance of thermal-electric energy conversion of the activated carbon is tested by using the activated carbon as solid electrode materials and KCl solution as electrolyte, which shows the treated activated carbon has better performance.
2017, 34(5): 1075-1081.
doi: 10.13801/j.cnki.fhclxb.20160715.004
Abstract:
Bi2Te3 powders were successfully synthesized by hydrothermal reaction, which were composited with carbon black (CB), and then the thermoelectric (TE) performance of Bi2Te3/CB composites was investigated. At the same time, TGA, SEM and XRD analysis methods were used to characterize the structure of Bi2Te3/CB composites and the relationship between microscopic structures and TE properties was researched intensively. It shows that the thermal conductivities of Bi2Te3/CB composites reduce sharply (from 0.5957 W/(m·K) to 0.0888 W/(m·K) at room temperature) because of doped with CB under the special structure design. However, the values of electrical and thermal conductivities of Bi2Te3/CB composites improve with the increase of Bi2Te3 weight fraction, and Seebeck coefficients increase first and then decrease. After sintering under 558℃ for 10 min, the figure of merit (ZT) of Bi2Te3/CB composites with 88.9% Bi2Te3 is the best (ZT=0.21) at room temperature. Although the ZT value is much lower than the stand of TE material application, this topic investigation may provide new insights and optimization approach into the design and development of Bi2Te3 TE material for application, especially in terms of lower thermal conductivity of materials.
Bi2Te3 powders were successfully synthesized by hydrothermal reaction, which were composited with carbon black (CB), and then the thermoelectric (TE) performance of Bi2Te3/CB composites was investigated. At the same time, TGA, SEM and XRD analysis methods were used to characterize the structure of Bi2Te3/CB composites and the relationship between microscopic structures and TE properties was researched intensively. It shows that the thermal conductivities of Bi2Te3/CB composites reduce sharply (from 0.5957 W/(m·K) to 0.0888 W/(m·K) at room temperature) because of doped with CB under the special structure design. However, the values of electrical and thermal conductivities of Bi2Te3/CB composites improve with the increase of Bi2Te3 weight fraction, and Seebeck coefficients increase first and then decrease. After sintering under 558℃ for 10 min, the figure of merit (ZT) of Bi2Te3/CB composites with 88.9% Bi2Te3 is the best (ZT=0.21) at room temperature. Although the ZT value is much lower than the stand of TE material application, this topic investigation may provide new insights and optimization approach into the design and development of Bi2Te3 TE material for application, especially in terms of lower thermal conductivity of materials.
In-situ reaction fabrication of ZnS/reduced graphene oxide composite and its photocatalytic property
2017, 34(5): 1082-1087.
doi: 10.13801/j.cnki.fhclxb.20160711.006
Abstract:
ZnS decotrated onto reduced graphene oxide(RGO) composite (ZnS/RGO) had been synthesized through one-step in-situ solvothermal reaction using ZnAc2 and graphene oxide as reaction precursor and dimethyl sulfoxide (DMSO) as a source of sulfur and reaction solvent. SEM、XRD、Raman and fluorescence spectroscopy had been used to characterize microtopography and chemical structure of ZnS and ZnS/RGO. The results show that the ZnS/RGO composite synthesized through in-situ reaction consists of uniformly decorated spherical ZnS particles and 6-7 layer-structured RGO sheets. Under the simulated ultraviolet irradiation, the photocatalytic results for methyl orange pollutants show that the degradation ratio of ZnS/RGO hybrid is remarkly higher than that of pure ZnS. During the recycling degradation process photocatalytic efficiency of ZnS/RGO remain stable, which demonstrates in-situ reaction enhance the interaction between ZnS and RGO. Fluorescence spectroscopy result shows enchanced photocatalytic degradation efficiency of ZnS/RGO hybrid is mainly attributed to in-situ incorporation of ZnS with RGO sheets, which can efficiently transfer the excited photoelectrons from ZnS to conjugated graphene structures, and further enlarges recombination efficiency of photogenergated electron-hole.
ZnS decotrated onto reduced graphene oxide(RGO) composite (ZnS/RGO) had been synthesized through one-step in-situ solvothermal reaction using ZnAc2 and graphene oxide as reaction precursor and dimethyl sulfoxide (DMSO) as a source of sulfur and reaction solvent. SEM、XRD、Raman and fluorescence spectroscopy had been used to characterize microtopography and chemical structure of ZnS and ZnS/RGO. The results show that the ZnS/RGO composite synthesized through in-situ reaction consists of uniformly decorated spherical ZnS particles and 6-7 layer-structured RGO sheets. Under the simulated ultraviolet irradiation, the photocatalytic results for methyl orange pollutants show that the degradation ratio of ZnS/RGO hybrid is remarkly higher than that of pure ZnS. During the recycling degradation process photocatalytic efficiency of ZnS/RGO remain stable, which demonstrates in-situ reaction enhance the interaction between ZnS and RGO. Fluorescence spectroscopy result shows enchanced photocatalytic degradation efficiency of ZnS/RGO hybrid is mainly attributed to in-situ incorporation of ZnS with RGO sheets, which can efficiently transfer the excited photoelectrons from ZnS to conjugated graphene structures, and further enlarges recombination efficiency of photogenergated electron-hole.
2017, 34(5): 1088-1094.
doi: 10.13801/j.cnki.fhclxb.20160826.001
Abstract:
T-typed bismaleimide (T-BMI) was used to blend with 4, 4'-bismaleimidodiphenylmethyene (BDM) for preparing a matrix resin with high toughness. The results show that T-BMI has great effect on improving the mechanical performances of the matrix resin. With the same mole between T-BMI and BDM, the impact strength and fracture toughness (GIC value) of T-BMI-BDM reach up to 17.2 kJ/m2 and 316 J/m2, which are increased by 66.3% and 39.8% than before modifying, respectively. Furthermore, the tensile strength and flexural strength are up to 101.0 MPa and 165.0 MPa, they are improved by 12.2% and 2.5% than before modifying, respectively. The analysis of DMA and TG show that the heat-resistance and thermal stabilities of the copolymerization system are not significantly influenced by introduced T-BMI. The glass transition temperature and 5% mass loss temperature are 267.2℃ and 403.7℃, respectively. Cure condition of the matrix resin determined by DSC curves are 160℃×2 h+180℃×2 h +200×2 h+230℃×4 h. Rheological property determined by viscosity-temperature and viscosity-time curves indicates that it can be suitable for RTM process, and resin injection temperature should be selected in the range of 125℃ to 140℃.
T-typed bismaleimide (T-BMI) was used to blend with 4, 4'-bismaleimidodiphenylmethyene (BDM) for preparing a matrix resin with high toughness. The results show that T-BMI has great effect on improving the mechanical performances of the matrix resin. With the same mole between T-BMI and BDM, the impact strength and fracture toughness (GIC value) of T-BMI-BDM reach up to 17.2 kJ/m2 and 316 J/m2, which are increased by 66.3% and 39.8% than before modifying, respectively. Furthermore, the tensile strength and flexural strength are up to 101.0 MPa and 165.0 MPa, they are improved by 12.2% and 2.5% than before modifying, respectively. The analysis of DMA and TG show that the heat-resistance and thermal stabilities of the copolymerization system are not significantly influenced by introduced T-BMI. The glass transition temperature and 5% mass loss temperature are 267.2℃ and 403.7℃, respectively. Cure condition of the matrix resin determined by DSC curves are 160℃×2 h+180℃×2 h +200×2 h+230℃×4 h. Rheological property determined by viscosity-temperature and viscosity-time curves indicates that it can be suitable for RTM process, and resin injection temperature should be selected in the range of 125℃ to 140℃.
2017, 34(5): 1095-1102.
doi: 10.13801/j.cnki.fhclxb.20160715.002
Abstract:
Lime and slag could be used to prepare lime-slag/soil composites. The effect of lime content, slag content and moisture content on heat & moisture comprehensive property of lime-slag/soil composites was studied by response surface methodology and the preparation technology for lime-slag/soil composites was optimized. The results show that heat & moisture comprehensive property is influenced by lime content, slag content and moisture content. Optimal program is obtained by regression analysis that lime content (mass ratio between lime and compo-site) is 10.19%, slag content (mass ratio between slag and composite) is 4.02%, and moisture content (mass ratio between water and composite) is 9.00%. Average equilibrium moisture content of optimal lime-slag/soil composites is 12.725%, thermal conductivity is 0.798 W/(m·K), optimal lime-slag/soil composites have favorable heat & moisture comprehensive property. Under the effect of alkaline excitation and micro aggregate, optimal lime-slag/soil composites have the whole and compact construction through structural analysis, and reasonable mechanical performance and heat & moisture comprehensive property.
Lime and slag could be used to prepare lime-slag/soil composites. The effect of lime content, slag content and moisture content on heat & moisture comprehensive property of lime-slag/soil composites was studied by response surface methodology and the preparation technology for lime-slag/soil composites was optimized. The results show that heat & moisture comprehensive property is influenced by lime content, slag content and moisture content. Optimal program is obtained by regression analysis that lime content (mass ratio between lime and compo-site) is 10.19%, slag content (mass ratio between slag and composite) is 4.02%, and moisture content (mass ratio between water and composite) is 9.00%. Average equilibrium moisture content of optimal lime-slag/soil composites is 12.725%, thermal conductivity is 0.798 W/(m·K), optimal lime-slag/soil composites have favorable heat & moisture comprehensive property. Under the effect of alkaline excitation and micro aggregate, optimal lime-slag/soil composites have the whole and compact construction through structural analysis, and reasonable mechanical performance and heat & moisture comprehensive property.
2017, 34(5): 1103-1110.
doi: 10.13801/j.cnki.fhclxb.20160825.004
Abstract:
For preparing biomass materials with agricultural waste, using rice straw, wheat straw, peanut straw, rice husk, wheat husk and peanut shell as fillers, bone glue as base material, six kinds of different fillers biomass composites were prepared by compression molding process. The components of the plant fibers were analyzed, and the mechanical property, hygroscopic capability, surface functional groups and thermostability of the composites were tested. The section microstructures of the composites were observed using stereomicroscope. It is found that cellulose content of wheat straw is the highest, which is followed by rice straw. The properties of composites prepared with the straw are better than with the shell from the same biomass. The rice straw/bone glue composite has the best binding interface compatibility and mechanical properties with tensile strength of 4.14 MPa and impact strength of 4.89 kJ/m2, which are 118% and 22.6% higher than that of rice husk/bone glue composite, 4.42%, 37.3%, 56.9% and 20.8% higher than that of wheat straw/bone glue and peanut straw/bone glue composites, respectively. The rice straw/bone glue composite has good anti-hygroscopic capability with equilibrium moisture absorption rate of 12.35%, 27.11%, 16.72%, 19.36%, 0.04% and 15.97% lower than the composites prepared with wheat straw, peanut straw, rice husk, wheat husk and peanut shell, respectively. With more wax layer on the surface of wheat straw, its composite with bone glue has poor properties. The rice husk/bone glue composite is the best in the thermostability among six kinds of biomass composites.
For preparing biomass materials with agricultural waste, using rice straw, wheat straw, peanut straw, rice husk, wheat husk and peanut shell as fillers, bone glue as base material, six kinds of different fillers biomass composites were prepared by compression molding process. The components of the plant fibers were analyzed, and the mechanical property, hygroscopic capability, surface functional groups and thermostability of the composites were tested. The section microstructures of the composites were observed using stereomicroscope. It is found that cellulose content of wheat straw is the highest, which is followed by rice straw. The properties of composites prepared with the straw are better than with the shell from the same biomass. The rice straw/bone glue composite has the best binding interface compatibility and mechanical properties with tensile strength of 4.14 MPa and impact strength of 4.89 kJ/m2, which are 118% and 22.6% higher than that of rice husk/bone glue composite, 4.42%, 37.3%, 56.9% and 20.8% higher than that of wheat straw/bone glue and peanut straw/bone glue composites, respectively. The rice straw/bone glue composite has good anti-hygroscopic capability with equilibrium moisture absorption rate of 12.35%, 27.11%, 16.72%, 19.36%, 0.04% and 15.97% lower than the composites prepared with wheat straw, peanut straw, rice husk, wheat husk and peanut shell, respectively. With more wax layer on the surface of wheat straw, its composite with bone glue has poor properties. The rice husk/bone glue composite is the best in the thermostability among six kinds of biomass composites.
2017, 34(5): 1111-1121.
doi: 10.13801/j.cnki.fhclxb.20160901.002
Abstract:
The 2-D picture and 3-D topography for asphalt and mineral aggregate were firstly scanned with the tapping mode of atomic force microscope (AFM). Then the surface energies of asphalt and mineral aggregates were measured with the force-curve mode of AFM and calculated to represent their physical bonding performance. The results indicate that the asphalt binders made with various crude oils have different chemical compositions and surface roughness. The asphalt binder with bee-structure has a larger roughness compared with asphalt binder without bee-structure. Ageing can reduce the surface roughness and surface energy of asphalt, then weaken the adhesive bonding between asphalt and mineral aggregate. Finally the relationships among the surface roughness and surface energies of asphalt and mineral aggregate, and the adhesive tensile strength of asphalt/mineral aggregate system were analyzed, based on the adhesive tensile test results at the macro-scale. It is found that the roughness of asphalt and mineral aggregate play a key role in determining their adhesion, when the asphalt has bee-structures. However, for the asphalt which has no bee-structures, the adhesion between asphalt and mineral aggregate is more dependent on the surface energies of materials, which actually represents the physical bond performances of materials.
The 2-D picture and 3-D topography for asphalt and mineral aggregate were firstly scanned with the tapping mode of atomic force microscope (AFM). Then the surface energies of asphalt and mineral aggregates were measured with the force-curve mode of AFM and calculated to represent their physical bonding performance. The results indicate that the asphalt binders made with various crude oils have different chemical compositions and surface roughness. The asphalt binder with bee-structure has a larger roughness compared with asphalt binder without bee-structure. Ageing can reduce the surface roughness and surface energy of asphalt, then weaken the adhesive bonding between asphalt and mineral aggregate. Finally the relationships among the surface roughness and surface energies of asphalt and mineral aggregate, and the adhesive tensile strength of asphalt/mineral aggregate system were analyzed, based on the adhesive tensile test results at the macro-scale. It is found that the roughness of asphalt and mineral aggregate play a key role in determining their adhesion, when the asphalt has bee-structures. However, for the asphalt which has no bee-structures, the adhesion between asphalt and mineral aggregate is more dependent on the surface energies of materials, which actually represents the physical bond performances of materials.
2017, 34(5): 1122-1129.
doi: 10.13801/j.cnki.fhclxb.20160711.007
Abstract:
The nanoindentation technique was used to measure the micro-mechanical properties of individual phase in hardened cement pastes through discrete nanoindentation, and the properties over large areas through grid nanoindentation. Comparisons were made between pastes with water to cement (w/cm) mass ratio of 0.3, 0.4 and 0.5 and the slag content of 0, 50% and 70% for water to cement=0.3 paste, to illustrate their differences on the phase distribution and the micro-mechanical properties. Significant portion of composite phase was found in slag-blended paste. A three-phase model was used to determine the volume fraction of the unhydrated phase included in the composite. A nanoindentation-based methodology was proposed to calculate the degree of hydration of Portland cement and slag-blended cement pastes. The calculated degree of hydration are more consistent with the results obtained from thermal gravimetric method for Portland cement pastes than that of the slag-blended pastes.
The nanoindentation technique was used to measure the micro-mechanical properties of individual phase in hardened cement pastes through discrete nanoindentation, and the properties over large areas through grid nanoindentation. Comparisons were made between pastes with water to cement (w/cm) mass ratio of 0.3, 0.4 and 0.5 and the slag content of 0, 50% and 70% for water to cement=0.3 paste, to illustrate their differences on the phase distribution and the micro-mechanical properties. Significant portion of composite phase was found in slag-blended paste. A three-phase model was used to determine the volume fraction of the unhydrated phase included in the composite. A nanoindentation-based methodology was proposed to calculate the degree of hydration of Portland cement and slag-blended cement pastes. The calculated degree of hydration are more consistent with the results obtained from thermal gravimetric method for Portland cement pastes than that of the slag-blended pastes.
2017, 34(5): 1130-1136.
doi: 10.13801/j.cnki.fhclxb.20160802.002
Abstract:
The dynamic shear rheometer (DSR) and bending beam rheometer (BBR) were utilized to test three asphalt(asphalt, styrene-butadiene-styene blockcopolymer(SBS)modified asphalt, rubber powder modified asphalt) before and after freeze-thaw cycles. The variation orderliness of high and low temperature performance of three asphalt under different freezing temperature and the concentration of snow melting salt and the cycle times of freeze-thaw were compared. Then the environment factors by grey correlation entropy were analyzed. The result shows that the most important factor on the complex modulus of asphalt (G*) is the concentration of snow melting salt, followed by 10℃ ductility.The factor which has the greatest impact on phase angle of asphalt (δ) is softening point, followed by 25℃ penetration. And the biggest influencing factor on the creep stiffness modulus of asphalt(S) is the concentration of snow melting salt, followed by 10℃ ductility. The factor which have the greatest impact on creep rate of asphalt (m) is test temperature, followed by freezing temperature.
The dynamic shear rheometer (DSR) and bending beam rheometer (BBR) were utilized to test three asphalt(asphalt, styrene-butadiene-styene blockcopolymer(SBS)modified asphalt, rubber powder modified asphalt) before and after freeze-thaw cycles. The variation orderliness of high and low temperature performance of three asphalt under different freezing temperature and the concentration of snow melting salt and the cycle times of freeze-thaw were compared. Then the environment factors by grey correlation entropy were analyzed. The result shows that the most important factor on the complex modulus of asphalt (G*) is the concentration of snow melting salt, followed by 10℃ ductility.The factor which has the greatest impact on phase angle of asphalt (δ) is softening point, followed by 25℃ penetration. And the biggest influencing factor on the creep stiffness modulus of asphalt(S) is the concentration of snow melting salt, followed by 10℃ ductility. The factor which have the greatest impact on creep rate of asphalt (m) is test temperature, followed by freezing temperature.
2017, 34(5): 1137-1145.
doi: 10.13801/j.cnki.fhclxb.20160901.001
Abstract:
In order to investigate the changes performance of pavement materials under the snow melting salt, the dynamic shear rheometer (DSR) was used to study repeat creep property of SBS (styrene-butadiene-styrene blockcopolymer) modified asphalt and rubber powder modified asphalt in Inner Mongolia region, and the atomic force microscope (AFM) was used to observe microstructure, the micro structure and the rheological properties of the two kinds of asphalt were compared and analysed after salt freezing cycles. AFM tests indicate that there are some "bee" structures in SBS modified asphalt, and the quality and size of "bee" structures change after freeze-thaw cycles; But there is not "bee" structures in rubber modified asphalt. At the same time, there is little change in microstructure before and after freeze-thaw cycles. DSR test results show that the ratio of transient strain to unloading instantaneous strain (εP/εL) of SBS modified asphalt and rubber powder modified asphalt increases at the beginning of the loading and then reach a steady state after a certain number of loading cycles. The εP/εL of SBS modified asphalt reduces and the εP/εL of rubber powder modified asphalt does not change after freeze-thaw cycles. Burgers model was used to fitting the parameter Gv. The Gv of SBS modified asphalt reduces, while it is increased for the rubber powder modified asphalt after freeze-thaw cycles. And the Gv of asphalt after water freezing has little difference from that after salt freezing. Rubber powder modified asphalt has better high temperature performance.
In order to investigate the changes performance of pavement materials under the snow melting salt, the dynamic shear rheometer (DSR) was used to study repeat creep property of SBS (styrene-butadiene-styrene blockcopolymer) modified asphalt and rubber powder modified asphalt in Inner Mongolia region, and the atomic force microscope (AFM) was used to observe microstructure, the micro structure and the rheological properties of the two kinds of asphalt were compared and analysed after salt freezing cycles. AFM tests indicate that there are some "bee" structures in SBS modified asphalt, and the quality and size of "bee" structures change after freeze-thaw cycles; But there is not "bee" structures in rubber modified asphalt. At the same time, there is little change in microstructure before and after freeze-thaw cycles. DSR test results show that the ratio of transient strain to unloading instantaneous strain (εP/εL) of SBS modified asphalt and rubber powder modified asphalt increases at the beginning of the loading and then reach a steady state after a certain number of loading cycles. The εP/εL of SBS modified asphalt reduces and the εP/εL of rubber powder modified asphalt does not change after freeze-thaw cycles. Burgers model was used to fitting the parameter Gv. The Gv of SBS modified asphalt reduces, while it is increased for the rubber powder modified asphalt after freeze-thaw cycles. And the Gv of asphalt after water freezing has little difference from that after salt freezing. Rubber powder modified asphalt has better high temperature performance.
2017, 34(5): 1146-1151.
doi: 10.13801/j.cnki.fhclxb.20160921.002
Abstract:
0-3 cement-based piezoelectric composites were fabricated by compressing technique, with sulphoaluminate cement as the matrix, Pb(Zr0.52Ti0.48)O3(PZT)/ceramic as the functional phase. The effects of forming pressure on the cement-based composites of different size PZT particles were investigated. The results indicate that the change in forming pressure affect the piezoelectric and dielectric properties of PZT/cement composites of different size PZT in different ways. In the forming pressure range from 30 MPa to 90 MPa, the piezoelectric strain factors (d33) and the relative dielectric constants (εr) of PZT/cement composites rapidly increase as forming pressure adds due to the reduction of porosity with pressure. However, the change in piezoelectric voltage factors (g33) with pressure is related to the size of PZT. The electromechanical coupling coefficients (Kt and Kp) of PZT/cement composites of different sized PZT particles also have distinct changes with forming pressure. For PZT/cement composites of 6 μm or 126 μm size PZT particles, the Kt and Kp reduce with the increasing of forming pressure, while that of composites of 430 μm size PZT particles goes up as forming pressure rises. In addition, both dielectric and piezoelectric performance degrade significantly when forming pressure is up to 150 MPa.
0-3 cement-based piezoelectric composites were fabricated by compressing technique, with sulphoaluminate cement as the matrix, Pb(Zr0.52Ti0.48)O3(PZT)/ceramic as the functional phase. The effects of forming pressure on the cement-based composites of different size PZT particles were investigated. The results indicate that the change in forming pressure affect the piezoelectric and dielectric properties of PZT/cement composites of different size PZT in different ways. In the forming pressure range from 30 MPa to 90 MPa, the piezoelectric strain factors (d33) and the relative dielectric constants (εr) of PZT/cement composites rapidly increase as forming pressure adds due to the reduction of porosity with pressure. However, the change in piezoelectric voltage factors (g33) with pressure is related to the size of PZT. The electromechanical coupling coefficients (Kt and Kp) of PZT/cement composites of different sized PZT particles also have distinct changes with forming pressure. For PZT/cement composites of 6 μm or 126 μm size PZT particles, the Kt and Kp reduce with the increasing of forming pressure, while that of composites of 430 μm size PZT particles goes up as forming pressure rises. In addition, both dielectric and piezoelectric performance degrade significantly when forming pressure is up to 150 MPa.
2017, 34(5): 1152-1158.
doi: 10.13801/j.cnki.fhclxb.20160729.001
Abstract:
The calculative double nonlinear layered combinative(DNLC) element of high performance concrete(HPC) beams strengthened with prestressed hybrid fiber(HFRP) sheet were established for different kinds of mixture ratios. The prestress effect of HFRP sheet was effectively simulated by isoperimetric layer element with initial stress. After considering the material nonlinearity of the HPC beams and the geometry nonlinearity of the structures, the analytical model based on DNLC element was validated, and then the mechanical behaviors including the cracking loads, the stress development of the steel and the stress redistribution of HFRP sheet of the strengthened beams were studied. By comparing with the experimental results, the results of this method are in good agreement with the experimental results, which proves that the prestress of HFRP is efficiently modeled by isoperimetric layer element and the DNLC element is reliable. The characteristic loads of prestressed CFRP sheet are higher than those of prestressed GFRP sheet. However, the degree of increase of the cracking loads of prestressed CFRP sheet is smaller compared with hybrid fiber sheet and the residual strength of CFRP sheet is more than other hybrid fiber sheets. Before cracking loads, the stress redistribution of the hybrid fiber sheet changes a little and then after yielding loads, it increases fast until the structure fails.
The calculative double nonlinear layered combinative(DNLC) element of high performance concrete(HPC) beams strengthened with prestressed hybrid fiber(HFRP) sheet were established for different kinds of mixture ratios. The prestress effect of HFRP sheet was effectively simulated by isoperimetric layer element with initial stress. After considering the material nonlinearity of the HPC beams and the geometry nonlinearity of the structures, the analytical model based on DNLC element was validated, and then the mechanical behaviors including the cracking loads, the stress development of the steel and the stress redistribution of HFRP sheet of the strengthened beams were studied. By comparing with the experimental results, the results of this method are in good agreement with the experimental results, which proves that the prestress of HFRP is efficiently modeled by isoperimetric layer element and the DNLC element is reliable. The characteristic loads of prestressed CFRP sheet are higher than those of prestressed GFRP sheet. However, the degree of increase of the cracking loads of prestressed CFRP sheet is smaller compared with hybrid fiber sheet and the residual strength of CFRP sheet is more than other hybrid fiber sheets. Before cracking loads, the stress redistribution of the hybrid fiber sheet changes a little and then after yielding loads, it increases fast until the structure fails.
2017, 34(5): 1159-1166.
doi: 10.13801/j.cnki.fhclxb.20170302.003
Abstract:
For enhancing the interface bonding and the bringing effect of the basalt fibers (BF) to the cement matrix, the BF was treated with different concentrations of HCl solution (0-2.0 mol/L) and NaOH solution (0-2.0 mol/L), respectively. The mechanical properties of BF reinforced cement composites were studied. The results indicate that with the increase of the concentration of HCl solution, the flexural strength and bending strength increase firstly and then decrease, midspan deflection increases slowly and the change of compressive strength of BF/cement composite is not obvious. The strength and toughness of BF/cement composite are the highest as the concentration of HCl solution is 1 mol/L. The strength of BF/cement composite decreases significantly when BF is treated with NaOH solution, and the toughness of the composite is not improved obviously. Mass ratio variation trend of BF corroded HCl solution is similar to that of BF corroded with NaOH solution while strength ratio of BF corroded HCl solution is more than that of BF corroded with the same concentrate of NaOH solution.
For enhancing the interface bonding and the bringing effect of the basalt fibers (BF) to the cement matrix, the BF was treated with different concentrations of HCl solution (0-2.0 mol/L) and NaOH solution (0-2.0 mol/L), respectively. The mechanical properties of BF reinforced cement composites were studied. The results indicate that with the increase of the concentration of HCl solution, the flexural strength and bending strength increase firstly and then decrease, midspan deflection increases slowly and the change of compressive strength of BF/cement composite is not obvious. The strength and toughness of BF/cement composite are the highest as the concentration of HCl solution is 1 mol/L. The strength of BF/cement composite decreases significantly when BF is treated with NaOH solution, and the toughness of the composite is not improved obviously. Mass ratio variation trend of BF corroded HCl solution is similar to that of BF corroded with NaOH solution while strength ratio of BF corroded HCl solution is more than that of BF corroded with the same concentrate of NaOH solution.
