2018 Vol. 35, No. 2
2018, 35(2): 245-252.
doi: 10.13801/j.cnki.fhclxb.20170512.001
Abstract:
The nano ZnO/poly(methyl methacrylate)(nano ZnO/PMMA) composites were prepared by a simple and environmental friendly method. The functions including UV resistance, transparency, photoluminescence and antibacterial properties of nano ZnO/PMMA were studied. The monomer, initiator, precursor and catalyst were dissolved in ethanol at 30℃. The system were heated to 80℃, the polymerization of poly(methyl methacrylate)(MMA) and the synthesis of ZnO were carried out simultaneously.The nano ZnO/PMMA composites were obtained after solvent evaporation.The nano ZnO/PMMA composites were characterized by XRD, FTIR, TEM and UV-Vis. The results show the successful preparation of nano ZnO/PMMA composites, nano ZnO/PMMA composites could absorb ultraviolet radiation of 200-400 nm and have high transparency in visible region. The characterization of photoluminescence shows that nano ZnO/PMMA is able to emit bright blue-green light under excitation of ultraviolet light. The antibacterial testing result showes that nano ZnO/PMMA composites have significant antibacterial effect on staphylococcus aureus, the antibacterial rate is more than 99%. nano ZnO/PMMA composites perform multifunctional properties and have potential applications in many areas, such as UV shielding coatings, UV resistant plexiglass, fluorescent materials, antibacterial plastic products, and so on.
The nano ZnO/poly(methyl methacrylate)(nano ZnO/PMMA) composites were prepared by a simple and environmental friendly method. The functions including UV resistance, transparency, photoluminescence and antibacterial properties of nano ZnO/PMMA were studied. The monomer, initiator, precursor and catalyst were dissolved in ethanol at 30℃. The system were heated to 80℃, the polymerization of poly(methyl methacrylate)(MMA) and the synthesis of ZnO were carried out simultaneously.The nano ZnO/PMMA composites were obtained after solvent evaporation.The nano ZnO/PMMA composites were characterized by XRD, FTIR, TEM and UV-Vis. The results show the successful preparation of nano ZnO/PMMA composites, nano ZnO/PMMA composites could absorb ultraviolet radiation of 200-400 nm and have high transparency in visible region. The characterization of photoluminescence shows that nano ZnO/PMMA is able to emit bright blue-green light under excitation of ultraviolet light. The antibacterial testing result showes that nano ZnO/PMMA composites have significant antibacterial effect on staphylococcus aureus, the antibacterial rate is more than 99%. nano ZnO/PMMA composites perform multifunctional properties and have potential applications in many areas, such as UV shielding coatings, UV resistant plexiglass, fluorescent materials, antibacterial plastic products, and so on.
2018, 35(2): 253-259.
doi: 10.13801/j.cnki.fhclxb.20170531.002
Abstract:
The electrolyte was made by dissolving Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI)which had excellent chemical stability and high conductivity in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) ionic liquid. And the electrolyte was added to the epoxy vinyl ester resin to improve its performance. The results show that after adding the lithium electrolyte, the characteristic peak of ionic liquid can be detected by FTIR spectroscopy. As the electrolyte content increases, the porosity of the lithium ionic liquid/epoxy vinyl ester resin system gradually increases, as well as the gully and lamellar structure. This change is beneficial to the conduction of lithium ions, which can improve the electrical properties. At the same time, it can improve the plasticity and toughness of the resin to achieve better mechanical properties. In this experiment, when the electrolyte content is 40wt%, the system can achieve multifunction to the largest extend.
The electrolyte was made by dissolving Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI)which had excellent chemical stability and high conductivity in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) ionic liquid. And the electrolyte was added to the epoxy vinyl ester resin to improve its performance. The results show that after adding the lithium electrolyte, the characteristic peak of ionic liquid can be detected by FTIR spectroscopy. As the electrolyte content increases, the porosity of the lithium ionic liquid/epoxy vinyl ester resin system gradually increases, as well as the gully and lamellar structure. This change is beneficial to the conduction of lithium ions, which can improve the electrical properties. At the same time, it can improve the plasticity and toughness of the resin to achieve better mechanical properties. In this experiment, when the electrolyte content is 40wt%, the system can achieve multifunction to the largest extend.
2018, 35(2): 260-266.
doi: 10.13801/j.cnki.fhclxb.20170615.001
Abstract:
The need of the bulletproof radome in Ku/Ka band is becoming more and more urgent as the weapon power increasing. The dielectric performances were discussed by waveguide method. After the simulation and experiment, the ultra-high molecular weight polyethylene (UHMWPE) was the best composite in Ku/Ka band. The wave transparent performances of bulletproof laminates were optimized by HFSS software. The loss of 7 mm bulletproof laminate is 0.2 dB at Ku band, while 0.6 dB at Ka band, which fits the simulation result. The bullet performance of 5.6 kg/m2 UHMWPE laminate is beyond 1 Class, whose V50 is 546 m/s.
The need of the bulletproof radome in Ku/Ka band is becoming more and more urgent as the weapon power increasing. The dielectric performances were discussed by waveguide method. After the simulation and experiment, the ultra-high molecular weight polyethylene (UHMWPE) was the best composite in Ku/Ka band. The wave transparent performances of bulletproof laminates were optimized by HFSS software. The loss of 7 mm bulletproof laminate is 0.2 dB at Ku band, while 0.6 dB at Ka band, which fits the simulation result. The bullet performance of 5.6 kg/m2 UHMWPE laminate is beyond 1 Class, whose V50 is 546 m/s.
2018, 35(2): 267-274.
doi: 10.13801/j.cnki.fhclxb.20170418.004
Abstract:
By using ultrasonic technology to prepare anhydrous CaSO4 whisker loaded amides β nucleating agent (βNB) for making polypropylene (PP) composites, the mechanical properties of PP composites were studied, and the influencing factors were explored by DSC and SEM. The results show that using ultrasonic technology to treat CaSO4W load βNB can greatly improve the impact toughness of the blending of ultrasonic CaSO4(UCaSO4W) loaded βBN and PP composites by 56.1%-124.1% compared with pure PP, while untreated CaSO4W loaded βNB and βNB alone with βNB/PP composites without this effect. DSC and SEM analysis show that the changes of PP beta crystal content in the βNB/PP, CaSO4W-βNB/PP and UCaSO4W-βNB/PP composites are related to the addition of βNB content, CaSO4W and βNB existed antagonism action on PP beta crystal effect; the main cause of the improvement of the impact performance is not the change of PP beta crystal content, but the processing of ultrasonic CaSO4W and βNB.
By using ultrasonic technology to prepare anhydrous CaSO4 whisker loaded amides β nucleating agent (βNB) for making polypropylene (PP) composites, the mechanical properties of PP composites were studied, and the influencing factors were explored by DSC and SEM. The results show that using ultrasonic technology to treat CaSO4W load βNB can greatly improve the impact toughness of the blending of ultrasonic CaSO4(UCaSO4W) loaded βBN and PP composites by 56.1%-124.1% compared with pure PP, while untreated CaSO4W loaded βNB and βNB alone with βNB/PP composites without this effect. DSC and SEM analysis show that the changes of PP beta crystal content in the βNB/PP, CaSO4W-βNB/PP and UCaSO4W-βNB/PP composites are related to the addition of βNB content, CaSO4W and βNB existed antagonism action on PP beta crystal effect; the main cause of the improvement of the impact performance is not the change of PP beta crystal content, but the processing of ultrasonic CaSO4W and βNB.
2018, 35(2): 275-281.
doi: 10.13801/j.cnki.fhclxb.20170509.002
Abstract:
Octadecyltrimethyl ammonium bromide (OTAB) was used as a cationic surfactant to modify micron BN platelets with an organic surface. The effects of BN surface modification on the thermal conductivity of BN/epoxy composites were studied. The adsorption of OTAB on BN surface is close to saturation at OTAB concentration of 0.6 g · L-1. BN surface modification improves the wettability of epoxy resin on BN surface and decreases the thermal conductivity of BN. SEM and viscosity characterization show that the interfacial and compatible properties of BN/epoxy composites are improved by the surface modification of BN. Due to the decrease in interfacial thermal resistance, the thermal conductivity of the modified BN/epoxy composites is higher than original BN/epoxy composites. When the filler loading is 30% (mass ratio of filler to matrix resin), the thermal conductivity of the modified BN/epoxy composite is 1.03 W(m · K)-1, 2.15 times of the thermal conductivity (0.48 W(m · K)-1) of original BN/epoxy composites.
Octadecyltrimethyl ammonium bromide (OTAB) was used as a cationic surfactant to modify micron BN platelets with an organic surface. The effects of BN surface modification on the thermal conductivity of BN/epoxy composites were studied. The adsorption of OTAB on BN surface is close to saturation at OTAB concentration of 0.6 g · L-1. BN surface modification improves the wettability of epoxy resin on BN surface and decreases the thermal conductivity of BN. SEM and viscosity characterization show that the interfacial and compatible properties of BN/epoxy composites are improved by the surface modification of BN. Due to the decrease in interfacial thermal resistance, the thermal conductivity of the modified BN/epoxy composites is higher than original BN/epoxy composites. When the filler loading is 30% (mass ratio of filler to matrix resin), the thermal conductivity of the modified BN/epoxy composite is 1.03 W(m · K)-1, 2.15 times of the thermal conductivity (0.48 W(m · K)-1) of original BN/epoxy composites.
2018, 35(2): 282-290.
doi: 10.13801/j.cnki.fhclxb.20170609.005
Abstract:
The impact has an obvious effect on inter laminar fracture of material surface. The influence of the impact on inter laminar fracture toughness is not clear at present. In particular, the influence on and the trend of the blade skin inter laminar fracture caused by the blade lead-lag have not been studied. In this paper, firstly, the dynamic response of impact load acting on blades in the case of lead-lag was studied. And the relationship of vibration-displacement-velocity was determined. Then the finite element numerical analysis of stress-strain-velocity in the case of lead-lag was carried out. According to the continuum mechanics principle, the governing equations of the pendulum impact load were established. The relationship between strain energy release rate (G) and stress intensity factor (K), which are related to the status that the blade lead-lag caused the crack, was clarified. Finally, the results of this paper were verified by measuring the fracture parameters in the impact test. The influence on and the trend of the blade skin inter laminar fracture caused by the blade lead-lag was discussed.
The impact has an obvious effect on inter laminar fracture of material surface. The influence of the impact on inter laminar fracture toughness is not clear at present. In particular, the influence on and the trend of the blade skin inter laminar fracture caused by the blade lead-lag have not been studied. In this paper, firstly, the dynamic response of impact load acting on blades in the case of lead-lag was studied. And the relationship of vibration-displacement-velocity was determined. Then the finite element numerical analysis of stress-strain-velocity in the case of lead-lag was carried out. According to the continuum mechanics principle, the governing equations of the pendulum impact load were established. The relationship between strain energy release rate (G) and stress intensity factor (K), which are related to the status that the blade lead-lag caused the crack, was clarified. Finally, the results of this paper were verified by measuring the fracture parameters in the impact test. The influence on and the trend of the blade skin inter laminar fracture caused by the blade lead-lag was discussed.
2018, 35(2): 291-297.
doi: 10.13801/j.cnki.fhclxb.20170426.001
Abstract:
The RTM process specimens of glass fiber continuous mat/E51 epoxy resin with different void content were prepared by applying different injection pressure (0.1-0.35 MPa). The void content of the specimen was measured by ultrasonic method, metallography and density measurement/resin burnout method. The relationship between void content and resin injection pressure was investigated. Effect of void content on ultrasonic parameters and mechanical property of RTM composites was discussed. The results show that, the change of resin injection pressure has a significant effect on the void content. The injection pressure increases from 0.1 MPa to 0.35 MPa, and the void content of glass fiber continuous mat/E51 epoxy resin composites decreases from 9.95% to 3.73%. Ultrasonic characteristic parameters are nearly linearly increased with the increasing of void content, and especially the change of ultrasonic nonlinear characteristic parameters are more obvious. The change of ultrasonic parameters can evaluate void content of composite materials.
The RTM process specimens of glass fiber continuous mat/E51 epoxy resin with different void content were prepared by applying different injection pressure (0.1-0.35 MPa). The void content of the specimen was measured by ultrasonic method, metallography and density measurement/resin burnout method. The relationship between void content and resin injection pressure was investigated. Effect of void content on ultrasonic parameters and mechanical property of RTM composites was discussed. The results show that, the change of resin injection pressure has a significant effect on the void content. The injection pressure increases from 0.1 MPa to 0.35 MPa, and the void content of glass fiber continuous mat/E51 epoxy resin composites decreases from 9.95% to 3.73%. Ultrasonic characteristic parameters are nearly linearly increased with the increasing of void content, and especially the change of ultrasonic nonlinear characteristic parameters are more obvious. The change of ultrasonic parameters can evaluate void content of composite materials.
2018, 35(2): 298-303.
doi: 10.13801/j.cnki.fhclxb.20170418.002
Abstract:
Wood flour/high density polyethylene (WF/HDPE) composite provides environmental benefit. To improve WF/HDPE properties, the short carbon fibers (SCF) were introduced to WF/HDPE and short carbon fiber reinforced wood flour/high density polyethylene composite (SCF-WF/HDPE) was prepared. The surfaces of SCF were treated by three methods, including gas-phase, liquid-phase and gas-liquid dual-phase oxidization, to enhance the interface bonding between short carbon fibers and plastic matrix. Then the short carbon fiber-wood flour/high density polyethylene (SCF-WF/HDPE) composites were prepared by extrusion process. The mechanical, dynamic mechanical and rheological properties were measured to evaluate the effectiveness of the treatment methods. SEM shows that the surface roughness of carbon fibers increases after the surface treatment, which enhances the interfacial bonding with HDPE matrix; The DMA reveals the storage modulus increases. The results demonstrate that the surface treatment significantly improves the mechanical properties, thermal dynamic property and creep performance of WF/HDPE composite. The best surface treatment method is gas-phase treatment. Comparing with the WF/HDPE composite without carbon fibers, the composite containing gas-phase treat carbon fibers increases in tensile strength by 34.5%, flexural strength by 23%, and impact strength by 54.7%.
Wood flour/high density polyethylene (WF/HDPE) composite provides environmental benefit. To improve WF/HDPE properties, the short carbon fibers (SCF) were introduced to WF/HDPE and short carbon fiber reinforced wood flour/high density polyethylene composite (SCF-WF/HDPE) was prepared. The surfaces of SCF were treated by three methods, including gas-phase, liquid-phase and gas-liquid dual-phase oxidization, to enhance the interface bonding between short carbon fibers and plastic matrix. Then the short carbon fiber-wood flour/high density polyethylene (SCF-WF/HDPE) composites were prepared by extrusion process. The mechanical, dynamic mechanical and rheological properties were measured to evaluate the effectiveness of the treatment methods. SEM shows that the surface roughness of carbon fibers increases after the surface treatment, which enhances the interfacial bonding with HDPE matrix; The DMA reveals the storage modulus increases. The results demonstrate that the surface treatment significantly improves the mechanical properties, thermal dynamic property and creep performance of WF/HDPE composite. The best surface treatment method is gas-phase treatment. Comparing with the WF/HDPE composite without carbon fibers, the composite containing gas-phase treat carbon fibers increases in tensile strength by 34.5%, flexural strength by 23%, and impact strength by 54.7%.
2018, 35(2): 304-310.
doi: 10.13801/j.cnki.fhclxb.20170601.001
Abstract:
Angle-ply of[±45°]8s unidirectional glass fiber reinforced epoxy composites were made by vacuum assisted molding process. The shear properties under constant strain rate were researched by special equipment. Test strain rate was from 3×10-4 s-1 to 128.4 s-1. A shear rate-dependent constitutive model of unidirectional glass fiber reinforced epoxy composite under intermediate strain rate was established based on Khan-Huang model. The optimal parameters were identified by least square method and genetic algorithm. The results show shear properties of unidirectional glass fiber reinforced epoxy composite depends on strain rate and shear strength increases with strain rate. The ultimate strength increases by 35.5% at 128.4 s-1. Constitutive model established in this paper can accurately reflect the shear properties of unidirectional glass fiber composite, and can be used to predict shear properties under intermediate strain rate.
Angle-ply of[±45°]8s unidirectional glass fiber reinforced epoxy composites were made by vacuum assisted molding process. The shear properties under constant strain rate were researched by special equipment. Test strain rate was from 3×10-4 s-1 to 128.4 s-1. A shear rate-dependent constitutive model of unidirectional glass fiber reinforced epoxy composite under intermediate strain rate was established based on Khan-Huang model. The optimal parameters were identified by least square method and genetic algorithm. The results show shear properties of unidirectional glass fiber reinforced epoxy composite depends on strain rate and shear strength increases with strain rate. The ultimate strength increases by 35.5% at 128.4 s-1. Constitutive model established in this paper can accurately reflect the shear properties of unidirectional glass fiber composite, and can be used to predict shear properties under intermediate strain rate.
2018, 35(2): 311-319.
doi: 10.13801/j.cnki.fhclxb.20170505.001
Abstract:
Due to no requirements for wave velocity and time of flight of ultrasonic guided waves, probability-based diagnostic imaging (PDI) algorithm is especially suitable for damage identification of composite structures. However, the defect distribution probability of PDI algorithm is relatively inaccurate, which reduce the damage localization accuracy. Thus in engineering applications, the effectiveness of PDI algorithm could be affected. In order to improve the damage localization accuracy, an improved PDI algorithm was proposed. Using the relationship between the damage index and the relative distance from damage to the direct path of actuator-sensor path, the defect distribution probability of PDI algorithm was modified in the proposed algorithm. The validity of the proposed algorithm was assessed by identifying damages at different locations on a stiffened composite panel. The results show that the proposed algorithm can identify a single damage of stiffened composite panel accurately, and it can identify two damages effectively as well.
Due to no requirements for wave velocity and time of flight of ultrasonic guided waves, probability-based diagnostic imaging (PDI) algorithm is especially suitable for damage identification of composite structures. However, the defect distribution probability of PDI algorithm is relatively inaccurate, which reduce the damage localization accuracy. Thus in engineering applications, the effectiveness of PDI algorithm could be affected. In order to improve the damage localization accuracy, an improved PDI algorithm was proposed. Using the relationship between the damage index and the relative distance from damage to the direct path of actuator-sensor path, the defect distribution probability of PDI algorithm was modified in the proposed algorithm. The validity of the proposed algorithm was assessed by identifying damages at different locations on a stiffened composite panel. The results show that the proposed algorithm can identify a single damage of stiffened composite panel accurately, and it can identify two damages effectively as well.
2018, 35(2): 320-331.
doi: 10.13801/j.cnki.fhclxb.20170413.001
Abstract:
Shear stability experiments on aeronautic composite stiffened panel were conducted to investigate the buckling load, buckling mode, post-buckling carrying capacity and failure characterization. The results show the centric lines of buckling waves have an angle of 45° with the direction of stiffeners under shear buckling load. The re-buckling behaviors will occur when the buckling ratio reaches 1.2. Failure load is 1.28 times of the buckling load. The stiffeners work as 'skin buckling separated' before re-buckling, and have little deformation. Theoretical analysis on the buckling and post-buckling behaviors was carried out. The buckling load by theoretical analysis is in a good agreement with experimental results with an error of 7.2%. Additionally, the slope of load-strain curve in post-buckling stage by theoretical analysis also leads an error less than 10% compared with experimental data. Finally, the variation law of the post-buckling angle and buckling ratio was determined.
Shear stability experiments on aeronautic composite stiffened panel were conducted to investigate the buckling load, buckling mode, post-buckling carrying capacity and failure characterization. The results show the centric lines of buckling waves have an angle of 45° with the direction of stiffeners under shear buckling load. The re-buckling behaviors will occur when the buckling ratio reaches 1.2. Failure load is 1.28 times of the buckling load. The stiffeners work as 'skin buckling separated' before re-buckling, and have little deformation. Theoretical analysis on the buckling and post-buckling behaviors was carried out. The buckling load by theoretical analysis is in a good agreement with experimental results with an error of 7.2%. Additionally, the slope of load-strain curve in post-buckling stage by theoretical analysis also leads an error less than 10% compared with experimental data. Finally, the variation law of the post-buckling angle and buckling ratio was determined.
2018, 35(2): 332-339.
doi: 10.13801/j.cnki.fhclxb.20170327.002
Abstract:
Based on single-side strap joint configuration theory, an analytical model of cracked flat plate repaired by single-sided patch considering the influence of additional bending moment was established. Through the analytical model, the maximum stress and minimum stress in base plate were calculated, which were compared with the FE results. The effect of patch length, patch width, patch thickness and adhesive elastic modulus on the J-internal values around the crack tips were analyzed, and the analytical equation for J-internal was obtained by fitting the magnitude relation between the stress in base plate and J-internal, the validity of which predicting the J-internal in cracked curved plate repaired by single-sided patch was also proved. The analysis shows that the model can be applied to flat or curved plates subjected to in-plane loadings or out-of-plane bending loadings.
Based on single-side strap joint configuration theory, an analytical model of cracked flat plate repaired by single-sided patch considering the influence of additional bending moment was established. Through the analytical model, the maximum stress and minimum stress in base plate were calculated, which were compared with the FE results. The effect of patch length, patch width, patch thickness and adhesive elastic modulus on the J-internal values around the crack tips were analyzed, and the analytical equation for J-internal was obtained by fitting the magnitude relation between the stress in base plate and J-internal, the validity of which predicting the J-internal in cracked curved plate repaired by single-sided patch was also proved. The analysis shows that the model can be applied to flat or curved plates subjected to in-plane loadings or out-of-plane bending loadings.
2018, 35(2): 340-346.
doi: 10.13801/j.cnki.fhclxb.20170426.002
Abstract:
Experimental study shows that the transverse tensile strength of fiber bundle/epoxy resin composites specimens has a good correlation with the transverse tensile strength of unidirectional laminate specimens. However, there is a discrepancy in values obtained using the two testing methods. In this paper, three types of fiber bundle/epoxy resin composites and unidirectional laminates were prepared using two kinds of carbon fibers and epoxy resins. Based on the measured transverse tensile strength of fiber bundle/epoxy resin composites and unidirectional laminates, as well as the tensile strength of epoxy matrices, a strength model was established to bridge the transverse tensile strength of fiber bundle/epoxy resin composite and unidirectional laminate. The parameters in the model were fitted according to the experimental results of two types of fiber bundle/epoxy resin composites and unidirectional laminates. Then the model was verified using the third type of fiber bundle/epoxy resin composite and unidirectional laminate. It is found that the predicted transverse tensile strength of the unidirectional laminate agrees well with the measured value, with relative deviation of 9%. Therefore, the proposed method can be employed to predict the transverse tensile strength of unidirectional laminates with simple tensile tests of fiber bundle/epoxy resin composites and epoxy matrices.
Experimental study shows that the transverse tensile strength of fiber bundle/epoxy resin composites specimens has a good correlation with the transverse tensile strength of unidirectional laminate specimens. However, there is a discrepancy in values obtained using the two testing methods. In this paper, three types of fiber bundle/epoxy resin composites and unidirectional laminates were prepared using two kinds of carbon fibers and epoxy resins. Based on the measured transverse tensile strength of fiber bundle/epoxy resin composites and unidirectional laminates, as well as the tensile strength of epoxy matrices, a strength model was established to bridge the transverse tensile strength of fiber bundle/epoxy resin composite and unidirectional laminate. The parameters in the model were fitted according to the experimental results of two types of fiber bundle/epoxy resin composites and unidirectional laminates. Then the model was verified using the third type of fiber bundle/epoxy resin composite and unidirectional laminate. It is found that the predicted transverse tensile strength of the unidirectional laminate agrees well with the measured value, with relative deviation of 9%. Therefore, the proposed method can be employed to predict the transverse tensile strength of unidirectional laminates with simple tensile tests of fiber bundle/epoxy resin composites and epoxy matrices.
2018, 35(2): 347-355.
doi: 10.13801/j.cnki.fhclxb.20170412.005
Abstract:
By using vacuum bag molding process, T-shaped stiffened carbon fiber reinforced resin composite panel was prepared with CYCOM 5320-1 prepreg. Then the curing deformation was measured by laser tracer. The simulation of curing process of the panel with and without mold considered was launched by finite element method. The results of the simulation show that the simulation and test have the same deformation tendency, and the deformation fits well along the width direction. It is more close to the true values when considering the mold factor. It is because that before resin reaches gel point, the mold is heated and squeezes die cavity, which causes permanent deformation of the component.
By using vacuum bag molding process, T-shaped stiffened carbon fiber reinforced resin composite panel was prepared with CYCOM 5320-1 prepreg. Then the curing deformation was measured by laser tracer. The simulation of curing process of the panel with and without mold considered was launched by finite element method. The results of the simulation show that the simulation and test have the same deformation tendency, and the deformation fits well along the width direction. It is more close to the true values when considering the mold factor. It is because that before resin reaches gel point, the mold is heated and squeezes die cavity, which causes permanent deformation of the component.
2018, 35(2): 356-363.
doi: 10.13801/j.cnki.fhclxb.20170420.003
Abstract:
The application of theory of micro-mechanics of failure (MMF) was extended to analyze the fatigue strength for the complex three-dimensional of the continuous fiber reinforced polymer (FRP) composite. The fatigue strength analysis method of the continuous FRP laminate structure was established based on the MMF theory. The strength and mechanical properties of unidirectional laminate of UTS50/E51 were measured by the static loading and fatigue-loading test. The constituent fatigue MMF critical parameters of the UTS50/E51 laminate were characterized and the S-lgN curves of the tensile and compressive fatigue MMF critical parameters of the fiber and matrix were obtained, which provided basis for using the MMF theory to analyze the fatigue strength of the continuous FRP laminates structure. The fatigue tensile strength of the laminates structure of polymer composites was studied based on MMF. The fatigue tension tests for the laminates structure of UTS50/E51 laminate were carried out. The strengths obtained from both theoretical analysis and tests were compared.
The application of theory of micro-mechanics of failure (MMF) was extended to analyze the fatigue strength for the complex three-dimensional of the continuous fiber reinforced polymer (FRP) composite. The fatigue strength analysis method of the continuous FRP laminate structure was established based on the MMF theory. The strength and mechanical properties of unidirectional laminate of UTS50/E51 were measured by the static loading and fatigue-loading test. The constituent fatigue MMF critical parameters of the UTS50/E51 laminate were characterized and the S-lgN curves of the tensile and compressive fatigue MMF critical parameters of the fiber and matrix were obtained, which provided basis for using the MMF theory to analyze the fatigue strength of the continuous FRP laminates structure. The fatigue tensile strength of the laminates structure of polymer composites was studied based on MMF. The fatigue tension tests for the laminates structure of UTS50/E51 laminate were carried out. The strengths obtained from both theoretical analysis and tests were compared.
2018, 35(2): 364-370.
doi: 10.13801/j.cnki.fhclxb.20170428.001
Abstract:
The 10B isotope of B in B4C which has high thermal neutron absorption cross-section is a great neutron absorber. B4C/6061Al composites with the B4C volume fractions of 10%-40% were fabricated by spark plasma sintering(SPS), the microstructure and phase composition of B4C/6061Al neutron absorber composites (B4C/6061Al) were analyzed and the tensile property of B4C/6061Al was measured. The results show that B4C particles distribute relatively homogeneously in 6061Al matrix, plasma generated by microscopic electrical discharge between the particles can improve the interfacial bonding of B4C particle/6061Al matrix, the phases of composites are mainly Al, B4C, AlB2 and Al3BC. With the increase of B4C volume fractions, the relative density of B4C/6061Al decreases and the tensile strength first increases and then decreases, the fracture mechanism is mainly the tear of 6061Al matrix and the B4C particle/6061Al matrix interface.
The 10B isotope of B in B4C which has high thermal neutron absorption cross-section is a great neutron absorber. B4C/6061Al composites with the B4C volume fractions of 10%-40% were fabricated by spark plasma sintering(SPS), the microstructure and phase composition of B4C/6061Al neutron absorber composites (B4C/6061Al) were analyzed and the tensile property of B4C/6061Al was measured. The results show that B4C particles distribute relatively homogeneously in 6061Al matrix, plasma generated by microscopic electrical discharge between the particles can improve the interfacial bonding of B4C particle/6061Al matrix, the phases of composites are mainly Al, B4C, AlB2 and Al3BC. With the increase of B4C volume fractions, the relative density of B4C/6061Al decreases and the tensile strength first increases and then decreases, the fracture mechanism is mainly the tear of 6061Al matrix and the B4C particle/6061Al matrix interface.
2018, 35(2): 371-376.
doi: 10.13801/j.cnki.fhclxb.20170511.002
Abstract:
The Mg alloy matrix composite reinforced by shape memory alloy TiNi wires was fabricated by Spark Plasma Sintering (SPS) process of AZ31 Mg alloy plate with TiNi SMA wires. The microstructure of TiNi reinforced Mg alloy composites was analyzed by microscopic analysis methods, including OM, SEM and EDS. The transformation of TiNi wires was analyzed by DSC and XRD. The mechanical properties of the composite materials at room temperature and high temperature were studied by quasi-static tensile test as well. The results show that a 2 μm mutual diffusion layer of Ti, Ni and Mg forms at the interface of the TiNi/Mg composite. The tensile properties of the composite at high temperature are better than RT. The yield strength, tensile strength and elastic modulus of the composite are higher than that at room temperature (157 MPa, 292 MPa, 22 GPa, respectively), i.e. increase by 12%, 33% and 29%, respectively, at 100℃, and higher than that at room temperature(143 MPa, 251 MPa, 20 GPa, respectively), i.e. increase by 2%, 14% and 18%, respectively, at 150℃.
The Mg alloy matrix composite reinforced by shape memory alloy TiNi wires was fabricated by Spark Plasma Sintering (SPS) process of AZ31 Mg alloy plate with TiNi SMA wires. The microstructure of TiNi reinforced Mg alloy composites was analyzed by microscopic analysis methods, including OM, SEM and EDS. The transformation of TiNi wires was analyzed by DSC and XRD. The mechanical properties of the composite materials at room temperature and high temperature were studied by quasi-static tensile test as well. The results show that a 2 μm mutual diffusion layer of Ti, Ni and Mg forms at the interface of the TiNi/Mg composite. The tensile properties of the composite at high temperature are better than RT. The yield strength, tensile strength and elastic modulus of the composite are higher than that at room temperature (157 MPa, 292 MPa, 22 GPa, respectively), i.e. increase by 12%, 33% and 29%, respectively, at 100℃, and higher than that at room temperature(143 MPa, 251 MPa, 20 GPa, respectively), i.e. increase by 2%, 14% and 18%, respectively, at 150℃.
2018, 35(2): 377-383.
doi: 10.13801/j.cnki.fhclxb.20170706.001
Abstract:
In this paper, the interface cracks between the zinc coating and the 304 stainless substrate were investigated and the interface fracture toughness of the Zinc coating-elastic substrate system was obtained by three point bending tests installed with an acoustic emission device and microscope. The interface propagation length obtained by a finite element method (FEM) is in agreement with the experimental result. A finite element simulation by ABAQUS was conducted and the result shows that the interface fracture toughness is related to many factors. The interface crack propagation length increases with the increase of film thickness and external load, and it decreases with the increase of interface fracture toughness and elastic modulus, while Poisson's ratio has little effect on the crack propagation length.
In this paper, the interface cracks between the zinc coating and the 304 stainless substrate were investigated and the interface fracture toughness of the Zinc coating-elastic substrate system was obtained by three point bending tests installed with an acoustic emission device and microscope. The interface propagation length obtained by a finite element method (FEM) is in agreement with the experimental result. A finite element simulation by ABAQUS was conducted and the result shows that the interface fracture toughness is related to many factors. The interface crack propagation length increases with the increase of film thickness and external load, and it decreases with the increase of interface fracture toughness and elastic modulus, while Poisson's ratio has little effect on the crack propagation length.
2018, 35(2): 384-390.
doi: 10.13801/j.cnki.fhclxb.20170519.001
Abstract:
The reduced graphene oxide@Ag2O co-modified TiO2-based composites (rGO@Ag2O/TiO2) were successfully synthesized, whose photocatalytic performance under visible light irradiation were also tested. The ternary rGO@Ag2O/TiO2 composites show much higher visible light photocatalytic activity than the pure TiO2 and rGO/TiO2、Ag2O/TiO2 binary composites, of which almost 100% Rhodamine B (RhB) molecules were decomposed by the rGO@Ag2O/TiO2 composites after 120 min visible light irradiation. Due to the introduction of the narrow gap semiconductor Ag2O and the admirable electron conductivity rGO, so the rGO@Ag2O/TiO2 ternary composites have strong visible light absorption ability and potent separation of electron-holes pairs, the ternary rGO@Ag2O/TiO2 composites show much higher visible light photocatalytic activity.
The reduced graphene oxide@Ag2O co-modified TiO2-based composites (rGO@Ag2O/TiO2) were successfully synthesized, whose photocatalytic performance under visible light irradiation were also tested. The ternary rGO@Ag2O/TiO2 composites show much higher visible light photocatalytic activity than the pure TiO2 and rGO/TiO2、Ag2O/TiO2 binary composites, of which almost 100% Rhodamine B (RhB) molecules were decomposed by the rGO@Ag2O/TiO2 composites after 120 min visible light irradiation. Due to the introduction of the narrow gap semiconductor Ag2O and the admirable electron conductivity rGO, so the rGO@Ag2O/TiO2 ternary composites have strong visible light absorption ability and potent separation of electron-holes pairs, the ternary rGO@Ag2O/TiO2 composites show much higher visible light photocatalytic activity.
2018, 35(2): 391-396.
doi: 10.13801/j.cnki.fhclxb.20170608.003
Abstract:
Fine weave pierced C/C throat was fabricated using electrically coupled chemical vapour impregnation(CVI) process together with resin infiltration and carbonization method. The pore size of fine weave pierced preform at different densification stages was characterized by μ-CT. Tensile properties of the samples at 2 800℃ and the ablation behaviors of the scaling down motor were also discussed. The results show that pores are located in between the fiber bundles in the material after the electrically coupled CVI, where the pores joint their boundaries to form the carbon body a net structure. Some micro pores, which sized 0-0.08 mm3 and scattered dispersed in the body, were left after several resin infiltration and carbonization cycles. The tensile strength is a little higher, but the fracture strain is increased by 118% at 2 800℃ than that at room temperature, which mean that the material possesses abnormal non-liner fracture behavior. The liner ablation rate is 0.077 mm/s for the material in a scaling solid motor. There are different ablation mechanisms for different throat parts:there are severe stagnations ablation at the convergent part which caused the honeycomb ablation dots, while the throat and divergent part have smooth ablation surfaces.
Fine weave pierced C/C throat was fabricated using electrically coupled chemical vapour impregnation(CVI) process together with resin infiltration and carbonization method. The pore size of fine weave pierced preform at different densification stages was characterized by μ-CT. Tensile properties of the samples at 2 800℃ and the ablation behaviors of the scaling down motor were also discussed. The results show that pores are located in between the fiber bundles in the material after the electrically coupled CVI, where the pores joint their boundaries to form the carbon body a net structure. Some micro pores, which sized 0-0.08 mm3 and scattered dispersed in the body, were left after several resin infiltration and carbonization cycles. The tensile strength is a little higher, but the fracture strain is increased by 118% at 2 800℃ than that at room temperature, which mean that the material possesses abnormal non-liner fracture behavior. The liner ablation rate is 0.077 mm/s for the material in a scaling solid motor. There are different ablation mechanisms for different throat parts:there are severe stagnations ablation at the convergent part which caused the honeycomb ablation dots, while the throat and divergent part have smooth ablation surfaces.
2018, 35(2): 397-402.
doi: 10.13801/j.cnki.fhclxb.20170428.002
Abstract:
The Si3N4 reaction-boned Fe3Si-Si3N4 composites were prepared in an atmosphere of highly pure nitrogen with Si powders and Fe3Si-Si3N4 particles as the raw materials. The phase composition turns out to be Si3N4, Fe2Si, FeSi and Si2N2O. The content of Si2N2O is about 6% and varies with the section of Si3N4 boned Fe3Si-Si3N4 block. By analyzing thermodynamics and microphotography of Si3N4, it is determined that Si2N2O comes from the oxidation of Si3N4. During the sintering, Fe3Si can transform to a low-melting-point ferrosilicon alloy with part of the Si powder dissolving into it. The molten ferrosilicon alloy, Fe2Si and FeSi, can fill or block the apparent pores and stop the diffusion of oxygen from central section to the marginal section. As a result, the oxygen reacts with Si3N4 of Fe3Si-Si3N4 generating more Si2N2O in central section of the block. The oxidation of Si3N4 costs the oxygen of the system and allows silicon to reacts with nitrogen directly generating columnar Si3N4, not fibrous Si3N4, which is completely different with silicon nitrodation mechanism in Si3N4 reaction-bonded Si. Meanwhile the existence of Fe α-Si3N4 transform to β-Si3N4 at 1 450℃.
The Si3N4 reaction-boned Fe3Si-Si3N4 composites were prepared in an atmosphere of highly pure nitrogen with Si powders and Fe3Si-Si3N4 particles as the raw materials. The phase composition turns out to be Si3N4, Fe2Si, FeSi and Si2N2O. The content of Si2N2O is about 6% and varies with the section of Si3N4 boned Fe3Si-Si3N4 block. By analyzing thermodynamics and microphotography of Si3N4, it is determined that Si2N2O comes from the oxidation of Si3N4. During the sintering, Fe3Si can transform to a low-melting-point ferrosilicon alloy with part of the Si powder dissolving into it. The molten ferrosilicon alloy, Fe2Si and FeSi, can fill or block the apparent pores and stop the diffusion of oxygen from central section to the marginal section. As a result, the oxygen reacts with Si3N4 of Fe3Si-Si3N4 generating more Si2N2O in central section of the block. The oxidation of Si3N4 costs the oxygen of the system and allows silicon to reacts with nitrogen directly generating columnar Si3N4, not fibrous Si3N4, which is completely different with silicon nitrodation mechanism in Si3N4 reaction-bonded Si. Meanwhile the existence of Fe α-Si3N4 transform to β-Si3N4 at 1 450℃.
2018, 35(2): 403-409.
doi: 10.13801/j.cnki.fhclxb.20170418.003
Abstract:
In order to adapt the demands for the lightweight of materials, MgAl2O4-CaAl4O7-CaAl12O19 (MA-CA2-CA6) composite was developed at 1 400-1 600℃ by addition of La2O3 micro powder, and the effect of La2O3 addition on sintering behavior, microstructure and mechanical properties of the composite was discussed. The results show that the added La2O3 dissolves to the CA6 phases of MA-CA2-CA6 composite, causing the lattice distortion of CA6 crystal, and the abnormal grain growth rate of CA6 to be decelerated, resulting in a more equiaxed morphology instead of anisotropic growth to platelet structure, thereby further contributes to the elimination of pores located between the initial plate-like CA6 grains. The disappearance of the platelet structures is favorable to Mg2+ diffusion and thus indirectly promotes the development of MA grains, so the sintering activity of MA-CA2-CA6 composite is comprehensively promoted. As a result, the dense microstructure is obtained, with the apparent porosity decreases from 19.2% to 6.1% and the bulk density increases from 2.78 g/cm3 to 3.18 g/cm3 after presintering at 1 200℃ and sintering at 1 600℃ for 2 h by addition of 4wt% La2O3. In addition, a texture microstructure of the crystal phase, which includes MA, CA2 and CA6, is observed in the typical back-scattered electron (BSE) images of microstructures with 4wt% La2O3 content La2O3/MA-CA2-CA6 composite samples sintered at 1 600℃ for 2 h, which is considered to be favorable to improve the mechanical properties of MA-CA2-CA6 composite, and the cold compressive strength increases from 317 MPa to 501 MPa after presintering at 1 200℃ and sintering at 1 600℃ for 2 h by addition of 4wt% La2O3.
In order to adapt the demands for the lightweight of materials, MgAl2O4-CaAl4O7-CaAl12O19 (MA-CA2-CA6) composite was developed at 1 400-1 600℃ by addition of La2O3 micro powder, and the effect of La2O3 addition on sintering behavior, microstructure and mechanical properties of the composite was discussed. The results show that the added La2O3 dissolves to the CA6 phases of MA-CA2-CA6 composite, causing the lattice distortion of CA6 crystal, and the abnormal grain growth rate of CA6 to be decelerated, resulting in a more equiaxed morphology instead of anisotropic growth to platelet structure, thereby further contributes to the elimination of pores located between the initial plate-like CA6 grains. The disappearance of the platelet structures is favorable to Mg2+ diffusion and thus indirectly promotes the development of MA grains, so the sintering activity of MA-CA2-CA6 composite is comprehensively promoted. As a result, the dense microstructure is obtained, with the apparent porosity decreases from 19.2% to 6.1% and the bulk density increases from 2.78 g/cm3 to 3.18 g/cm3 after presintering at 1 200℃ and sintering at 1 600℃ for 2 h by addition of 4wt% La2O3. In addition, a texture microstructure of the crystal phase, which includes MA, CA2 and CA6, is observed in the typical back-scattered electron (BSE) images of microstructures with 4wt% La2O3 content La2O3/MA-CA2-CA6 composite samples sintered at 1 600℃ for 2 h, which is considered to be favorable to improve the mechanical properties of MA-CA2-CA6 composite, and the cold compressive strength increases from 317 MPa to 501 MPa after presintering at 1 200℃ and sintering at 1 600℃ for 2 h by addition of 4wt% La2O3.
2018, 35(2): 410-417.
doi: 10.13801/j.cnki.fhclxb.20170531.005
Abstract:
The second heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory. The BNNTs/Si3N4 composites with weight fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process. The thermal shock resistance of the composite materials was tested by indentation method, verifying the second heat shock factor model in the steady state. The results indicate that the thermal shock performance of the material is enhanced by the BNNTs, with the increase of the second heat shock factor. Because the BNNTs which are distributed on the grain boundary make the crack pinned, bridged, and deflected, the crack propagation resistance is increased.
The second heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory. The BNNTs/Si3N4 composites with weight fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process. The thermal shock resistance of the composite materials was tested by indentation method, verifying the second heat shock factor model in the steady state. The results indicate that the thermal shock performance of the material is enhanced by the BNNTs, with the increase of the second heat shock factor. Because the BNNTs which are distributed on the grain boundary make the crack pinned, bridged, and deflected, the crack propagation resistance is increased.
2018, 35(2): 418-425.
doi: 10.13801/j.cnki.fhclxb.20170421.001
Abstract:
The nano Ag-polyvinyl butyral (PVB) composite nanofibers were prepared by electrospinning method, which aimed to fabricate antibacterial and efficient air filtration material. The morphology of nano Ag was characterized by TEM. The microstructure, chemical structure and crystal structure of the as-prepared nano Ag-PVB composite nanofibers were confirmed by SEM, FTIR and XRD. Moreover, the filtration efficiency, air permeability and antibacterial performance of the composite nanofibers were further studied. The results indicate that the suitable component for preparing composite nanofibers is 10wt% PVB and 0.25wt% nano Ag in ethanol solvent. Under the operating condition, the nano Ag-PVB composite nanofibers exhibit uniform structure with fiber diameter of 542.14 nm. The air filtration performance test reveals that the optimized electrospinning time is 10 min. Moreover, the nano Ag-PVB composite nanofibers display excellent PM2.5 filtration efficiency of 99.99%, low pressure drop of 16 Pa and appropriate air permeability of 155.0 mm/s. Further antibacterial test demonstrates that the nano Ag-PVB composite nanofibers exhibit good antibacterial performance for E.coli, and the antibacterial rate is 95.52%.
The nano Ag-polyvinyl butyral (PVB) composite nanofibers were prepared by electrospinning method, which aimed to fabricate antibacterial and efficient air filtration material. The morphology of nano Ag was characterized by TEM. The microstructure, chemical structure and crystal structure of the as-prepared nano Ag-PVB composite nanofibers were confirmed by SEM, FTIR and XRD. Moreover, the filtration efficiency, air permeability and antibacterial performance of the composite nanofibers were further studied. The results indicate that the suitable component for preparing composite nanofibers is 10wt% PVB and 0.25wt% nano Ag in ethanol solvent. Under the operating condition, the nano Ag-PVB composite nanofibers exhibit uniform structure with fiber diameter of 542.14 nm. The air filtration performance test reveals that the optimized electrospinning time is 10 min. Moreover, the nano Ag-PVB composite nanofibers display excellent PM2.5 filtration efficiency of 99.99%, low pressure drop of 16 Pa and appropriate air permeability of 155.0 mm/s. Further antibacterial test demonstrates that the nano Ag-PVB composite nanofibers exhibit good antibacterial performance for E.coli, and the antibacterial rate is 95.52%.
2018, 35(2): 426-432.
doi: 10.13801/j.cnki.fhclxb.20170413.003
Abstract:
The β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst was synthesized via chemical co-precipitation method, and the structure and performance of the composite were characterized by XRD, SEM, FTIR and superconducting quantum interference device (SQUID). The catalytic activity of β-MnO2/MnxZn1-xFe2O4 was studied by using Rhodamine B (RhB) as a simulated pollutant, and its stability was also studied. The results show that the spherical β-MnO2 and magnetic substrates MnxZn1-xFe2O4 are successfully combined together. The β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst has good catalytic and magnetic properties. When the mass ratio of MnxZn1-xFe2O4 and β-MnO2 is 20:100, in the presence of 2 mL of H2O2 (30%), the degradation rate of RhB at a concentration of 10 mg/L (100 mL) in β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst (93.9%) is higher than that in pure β-MnO2 (33.7%) within 1 h. Under the magnetic field, the recovery rate of the β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst is 89%, and the degradation rate of RhB is 76% after five cycles.
The β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst was synthesized via chemical co-precipitation method, and the structure and performance of the composite were characterized by XRD, SEM, FTIR and superconducting quantum interference device (SQUID). The catalytic activity of β-MnO2/MnxZn1-xFe2O4 was studied by using Rhodamine B (RhB) as a simulated pollutant, and its stability was also studied. The results show that the spherical β-MnO2 and magnetic substrates MnxZn1-xFe2O4 are successfully combined together. The β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst has good catalytic and magnetic properties. When the mass ratio of MnxZn1-xFe2O4 and β-MnO2 is 20:100, in the presence of 2 mL of H2O2 (30%), the degradation rate of RhB at a concentration of 10 mg/L (100 mL) in β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst (93.9%) is higher than that in pure β-MnO2 (33.7%) within 1 h. Under the magnetic field, the recovery rate of the β-MnO2/MnxZn1-xFe2O4 composite magnetic catalyst is 89%, and the degradation rate of RhB is 76% after five cycles.
2018, 35(2): 433-440.
doi: 10.13801/j.cnki.fhclxb.20170522.001
Abstract:
The tensile properties of the textile reinforced concrete fiber/concrete were investigated by the tensile test under different environments. The effects of the number of textile layers, the type of the textile, the concentration of the chloride salt and the number of cycles on the fiber/concrete were investigated under the chloride salt dry-wet cycle, freezing-thawing cycle and the conventional environment. The results show that the tensile properties of fiber/concrete can be improved by increasing the number of textile layers in the three kinds of environmental types, and the reinforcing effect of carbon fiber is more obvious than basalt fiber. The concentration of chloride and the number of dry-wet cycle or freezing-thawing cycle have no significant effect on fiber/concrete's tensile ultimate load. The tensile ultimate load of fiber/concrete can be increased by adding short-cut PVA (poly(vinyl alcohol)) fiber and AR(alkali-resistant)-glass fiber under the conventional environment and chlorine salt dry-wet cycle. Under the chloride salt freezing-thawing cycle, the tensile ultimate load of the fiber/concrete is not increased by the addition of PVA short-cut fiber, but increased by the addition of AR-glass short-cut fiber.
The tensile properties of the textile reinforced concrete fiber/concrete were investigated by the tensile test under different environments. The effects of the number of textile layers, the type of the textile, the concentration of the chloride salt and the number of cycles on the fiber/concrete were investigated under the chloride salt dry-wet cycle, freezing-thawing cycle and the conventional environment. The results show that the tensile properties of fiber/concrete can be improved by increasing the number of textile layers in the three kinds of environmental types, and the reinforcing effect of carbon fiber is more obvious than basalt fiber. The concentration of chloride and the number of dry-wet cycle or freezing-thawing cycle have no significant effect on fiber/concrete's tensile ultimate load. The tensile ultimate load of fiber/concrete can be increased by adding short-cut PVA (poly(vinyl alcohol)) fiber and AR(alkali-resistant)-glass fiber under the conventional environment and chlorine salt dry-wet cycle. Under the chloride salt freezing-thawing cycle, the tensile ultimate load of the fiber/concrete is not increased by the addition of PVA short-cut fiber, but increased by the addition of AR-glass short-cut fiber.
2018, 35(2): 441-450.
doi: 10.13801/j.cnki.fhclxb.20170424.001
Abstract:
In order to clarify the effect of low-temperature performance of warm-mixed asphalt mixture from warm-mixed agent and heating aging, the trabecular creep experiments, which are about original asphalt mixture, short-term aging and long-term aging asphalt mixture, were conducted by UTM-100 at temperature of 0℃, -10℃ and -20℃. The results show that the Burgess model parameter can be fitted by using the creep test data, then the temperature and strain energy density can be calculated, and the cracking temperature of the warm-mixed asphalt mixture can be predicted based on the creep test results, which can be used as a comprehensive index for the low-temperature performance of the asphalt mixture. The delayed mixing method can be taken as a method of characterizing the average aging degree of asphalt mixture in short-term aging process. The low-temperature performance of asphalt mixture at different temperatures and different aging degrees changes because of the fitting parameters. Warm-mixed agent can increase the short-term aging performance of asphalt mixture to a certain extent. It is found that the low-temperature performance of asphalt mixture can be reduced by adding RH warm-mixed agent, while Evotherm warm-mixed agent is beneficial to the low-temperature performance of asphalt mixture, so the Evotherm warm-mixed agent is recommended to be used in the cold area.
In order to clarify the effect of low-temperature performance of warm-mixed asphalt mixture from warm-mixed agent and heating aging, the trabecular creep experiments, which are about original asphalt mixture, short-term aging and long-term aging asphalt mixture, were conducted by UTM-100 at temperature of 0℃, -10℃ and -20℃. The results show that the Burgess model parameter can be fitted by using the creep test data, then the temperature and strain energy density can be calculated, and the cracking temperature of the warm-mixed asphalt mixture can be predicted based on the creep test results, which can be used as a comprehensive index for the low-temperature performance of the asphalt mixture. The delayed mixing method can be taken as a method of characterizing the average aging degree of asphalt mixture in short-term aging process. The low-temperature performance of asphalt mixture at different temperatures and different aging degrees changes because of the fitting parameters. Warm-mixed agent can increase the short-term aging performance of asphalt mixture to a certain extent. It is found that the low-temperature performance of asphalt mixture can be reduced by adding RH warm-mixed agent, while Evotherm warm-mixed agent is beneficial to the low-temperature performance of asphalt mixture, so the Evotherm warm-mixed agent is recommended to be used in the cold area.
2018, 35(2): 451-459.
doi: 10.13801/j.cnki.fhclxb.20170608.001
Abstract:
In order to study the effect of warm mix agents type and dosage on rheological property of different asphalts, temperature sweep experiment was tested for SBS modified asphalt and matrix asphalt mixed with RH and Evotherm warm mix agent by using Dynamic Shear Rheometerfor (DSR), and the complex shear modulus, phase angle and rutting factor of two kinds of asphalt were analyzed. The results show that Evotherm can improve the rutting resistance of two kinds of asphalt when the temperature is between 28℃ and 52℃, and the influence of Evotherm is weakened at temperature higher than 52℃. Evotherm can also improve the elastic recovery performance of two kinds of asphalt when the temperature is between 28℃ and 40℃, but it reduces the elastic recovery performance of SBS modified asphalt and has no effect on matrix asphalt at temperature higher than 40℃. The raise of Evotherm dosage can improve the rutting resistance of SBS modified asphalt and slightly reduce the rutting resistance of matrix asphalt when the temperature is between 28℃ and 52℃, and the influence is not obvious at temperature higher than 52℃. RH warm mix agent has a slightly adverse effect on anti-rutting performance when temperature is between 28℃ and 46℃, but the negative effect gradually weakens or even disappears with the rising of temperature, and RH warm mix agent can significantly increase the elastic recovery performance at high temperature of two types of asphalt. The increase of RH warm mix agent dosage will reduce anti-rutting performance but enhance the elastic recovery performance of two kinds of asphalt.
In order to study the effect of warm mix agents type and dosage on rheological property of different asphalts, temperature sweep experiment was tested for SBS modified asphalt and matrix asphalt mixed with RH and Evotherm warm mix agent by using Dynamic Shear Rheometerfor (DSR), and the complex shear modulus, phase angle and rutting factor of two kinds of asphalt were analyzed. The results show that Evotherm can improve the rutting resistance of two kinds of asphalt when the temperature is between 28℃ and 52℃, and the influence of Evotherm is weakened at temperature higher than 52℃. Evotherm can also improve the elastic recovery performance of two kinds of asphalt when the temperature is between 28℃ and 40℃, but it reduces the elastic recovery performance of SBS modified asphalt and has no effect on matrix asphalt at temperature higher than 40℃. The raise of Evotherm dosage can improve the rutting resistance of SBS modified asphalt and slightly reduce the rutting resistance of matrix asphalt when the temperature is between 28℃ and 52℃, and the influence is not obvious at temperature higher than 52℃. RH warm mix agent has a slightly adverse effect on anti-rutting performance when temperature is between 28℃ and 46℃, but the negative effect gradually weakens or even disappears with the rising of temperature, and RH warm mix agent can significantly increase the elastic recovery performance at high temperature of two types of asphalt. The increase of RH warm mix agent dosage will reduce anti-rutting performance but enhance the elastic recovery performance of two kinds of asphalt.
2018, 35(2): 460-467.
doi: 10.13801/j.cnki.fhclxb.20170426.003
Abstract:
In order to investigate the effect of embedded depth on the bond property between jute yarn and cement matrix, pull-out tests of jute yearns from the cement matrix were conducted by utilizing a Criterion 43 electromechanical universal test system. Correlations between mechanical parameters (pullout stiffness, peak pullout load, equivalent bond strength and work of pullout force) and embedded depths were obtained through the tests. Samples with four different embedded depths (20 mm, 40 mm, 60 mm and 80 mm) were tested at a constant displacement rate of 6 mm/min. The experimental results show that pullout stiffness decreases in spite of local undulation happened as embedded depth increases, while peak pullout load increases initially and then tends to be stable when the embedded depth is larger than 60 mm, and equivalent bond strength decreases with the increasing of embedded depth, and work of pullout force increases initially but then turns to decrease sharply at the embedded depth of 60 mm. Tested samples with different embedded depths were observed for the purpose of investigating the mechanisms of this variation further, through which the correlation between failure modes and embedded depths was obtained.
In order to investigate the effect of embedded depth on the bond property between jute yarn and cement matrix, pull-out tests of jute yearns from the cement matrix were conducted by utilizing a Criterion 43 electromechanical universal test system. Correlations between mechanical parameters (pullout stiffness, peak pullout load, equivalent bond strength and work of pullout force) and embedded depths were obtained through the tests. Samples with four different embedded depths (20 mm, 40 mm, 60 mm and 80 mm) were tested at a constant displacement rate of 6 mm/min. The experimental results show that pullout stiffness decreases in spite of local undulation happened as embedded depth increases, while peak pullout load increases initially and then tends to be stable when the embedded depth is larger than 60 mm, and equivalent bond strength decreases with the increasing of embedded depth, and work of pullout force increases initially but then turns to decrease sharply at the embedded depth of 60 mm. Tested samples with different embedded depths were observed for the purpose of investigating the mechanisms of this variation further, through which the correlation between failure modes and embedded depths was obtained.
2018, 35(2): 468-475.
doi: 10.13801/j.cnki.fhclxb.20170522.002
Abstract:
The structural properties of N-[3-(Trimethoxysilyl)propyl] ethylenediamine (DA)-Lauroyl Chloricle (LA) (DA-LA) dual composite self-assembled monolayers (SAMs), which was prepared on silicon (Si) substrates, were investigated by molecular dynamics simulation. The optimal coverage rate and arrangement of DA and LA molecules were obtained. The wetting process of water droplet on the surface of DA-LA dual composite SAMs was further discussed, and the wetting mechanism was analyzed by contact angle and radial distribution function. The investigation shows that the system energy is lowest when the coverage rate of DA on Si surface is 50% and the coverage rate of LA bond DA is 100%. In the lowest energy system, molecules of DA-LA dual composite SAMs on Si surface are arranged orderly, it reveals the formation mechanism of dense SAMs on Si surface by molecular method. The wetting mechanism simulation was analyzed in the optimal coverage rate system. The contact angles of water droplets on the DA-LA dual composite SAMs surface are similar to the experiment results, and the surface shows good hydrophobicity. Meanwhile, the contact angles of water droplet on the DA SAM are lower than the experiment results, because the DA coverage rate is low and the chain is short, and the hydrophilic hydroxyl molecules are exposed to the upper layer. By means of measuring and calculating, the surface free energy of hydroxylated Si is highest, followed by DA surface, and the surface of DA-LA is lowest. Further analysis shows that the hydrogen bond exists between the hydroxy Si surface, DA SAM surface and the water droplet, which strengthens the surface hydrophilicity; however, the weak van Edward force exists between the DA-LA dual composite SAMs surface and the water droplet, which enhances the surface hydrophobicity.
The structural properties of N-[3-(Trimethoxysilyl)propyl] ethylenediamine (DA)-Lauroyl Chloricle (LA) (DA-LA) dual composite self-assembled monolayers (SAMs), which was prepared on silicon (Si) substrates, were investigated by molecular dynamics simulation. The optimal coverage rate and arrangement of DA and LA molecules were obtained. The wetting process of water droplet on the surface of DA-LA dual composite SAMs was further discussed, and the wetting mechanism was analyzed by contact angle and radial distribution function. The investigation shows that the system energy is lowest when the coverage rate of DA on Si surface is 50% and the coverage rate of LA bond DA is 100%. In the lowest energy system, molecules of DA-LA dual composite SAMs on Si surface are arranged orderly, it reveals the formation mechanism of dense SAMs on Si surface by molecular method. The wetting mechanism simulation was analyzed in the optimal coverage rate system. The contact angles of water droplets on the DA-LA dual composite SAMs surface are similar to the experiment results, and the surface shows good hydrophobicity. Meanwhile, the contact angles of water droplet on the DA SAM are lower than the experiment results, because the DA coverage rate is low and the chain is short, and the hydrophilic hydroxyl molecules are exposed to the upper layer. By means of measuring and calculating, the surface free energy of hydroxylated Si is highest, followed by DA surface, and the surface of DA-LA is lowest. Further analysis shows that the hydrogen bond exists between the hydroxy Si surface, DA SAM surface and the water droplet, which strengthens the surface hydrophilicity; however, the weak van Edward force exists between the DA-LA dual composite SAMs surface and the water droplet, which enhances the surface hydrophobicity.
