2021 Vol. 38, No. 4
2021, 38(4): 1210-1222.
doi: 10.13801/j.cnki.fhclxb.20200713.005
Abstract:
In order to obtain high-performance and low-cost C/C composites, a series of preforms stitched with commercial grade large tow spreading carbon fiber cloth or aerospace grade small tow carbon fiber cloth were prepared. The carbon cloth stitched C/C composites were prepared by chemical vapor deposition (CVD), and the densification characteristics, microstructure features and mechanical properties of stitched C/C composites were characterized and discussed. The investigation results show that the types of carbon cloth and stitching density have obvious effects on the densification and mechanical properties of stitched C/C composites. When the type of preform selects key characteristics as spreading fiber cloth T700-12 K-100 g and stitching density 5 mm×5 mm, the values of tensile strength, compression strength, flexural strength and interlaminar shear strength for stitched C/C composites (1.781 g/cm3) reach 342.9 MPa、285.5 MPa、328.4 MPa and 15.2 MPa respectively, which are the international advanced level. The cost of high-performance C/C composites is greatly reduced by using spreading carbon cloth.
In order to obtain high-performance and low-cost C/C composites, a series of preforms stitched with commercial grade large tow spreading carbon fiber cloth or aerospace grade small tow carbon fiber cloth were prepared. The carbon cloth stitched C/C composites were prepared by chemical vapor deposition (CVD), and the densification characteristics, microstructure features and mechanical properties of stitched C/C composites were characterized and discussed. The investigation results show that the types of carbon cloth and stitching density have obvious effects on the densification and mechanical properties of stitched C/C composites. When the type of preform selects key characteristics as spreading fiber cloth T700-12 K-100 g and stitching density 5 mm×5 mm, the values of tensile strength, compression strength, flexural strength and interlaminar shear strength for stitched C/C composites (1.781 g/cm3) reach 342.9 MPa、285.5 MPa、328.4 MPa and 15.2 MPa respectively, which are the international advanced level. The cost of high-performance C/C composites is greatly reduced by using spreading carbon cloth.
Preparation and properties of strong polyaniline-polyacrylic acid/polyacrylamide conductive hydrogel
2021, 38(4): 1223-1230.
doi: 10.13801/j.cnki.fhclxb.20200806.004
Abstract:
The conductive polymer-based conductive hydrogels which introduced conductive polymers into the hydrogel network have been extensively studied because of the combination of three-dimensional network structure, good biocompatibility, excellent mechanical properties and electrical properties, especially the conductive hydrogels with polyaniline (PANI) as conductive polymer. However, PANI is insoluble in water, so it is difficult to prepare PANI-based conductive hydrogels. In order to prepare high-strength PANI based conductive hydrogels, this paper attempted to graft PANI onto the hydrophilic polymer polyacrylic acid (PAA) to obtain a PANI-PAA conductive composite that could be uniformly dispersed in water, and then it was polymerized with polyacrylamide (PAM) to obtain a strong PANI-PAA/PAM conductive hydrogel. Through mechanical and electrochemical tests, it is found that the conductive hydrogel has good mechanical and electrochemical properties. When SDS was used as dispersant, the conductivity could reach 4.63 S·m−1, meanwhile, it could withstand compression stress of 1.33 MPa (corresponding dissipation energy of compression is 85.50 kJ·m−3), the elongation at break is 964%, and the corresponding breaking strength is 0.25 MPa. Under the condition of NaOH as dispersant, the conductivity could reach 4.19 S·m−1, and it could bear the compression stress of 1.13 MPa (corresponding dissipation energy of compression is 73.45 kJ·m−3), the tensile elongation at break reaches 896%, and the corresponding fracture strength is 0.14 MPa. This study provides ideas for the preparation of high-strength polyaniline-based conductive hydrogels.
The conductive polymer-based conductive hydrogels which introduced conductive polymers into the hydrogel network have been extensively studied because of the combination of three-dimensional network structure, good biocompatibility, excellent mechanical properties and electrical properties, especially the conductive hydrogels with polyaniline (PANI) as conductive polymer. However, PANI is insoluble in water, so it is difficult to prepare PANI-based conductive hydrogels. In order to prepare high-strength PANI based conductive hydrogels, this paper attempted to graft PANI onto the hydrophilic polymer polyacrylic acid (PAA) to obtain a PANI-PAA conductive composite that could be uniformly dispersed in water, and then it was polymerized with polyacrylamide (PAM) to obtain a strong PANI-PAA/PAM conductive hydrogel. Through mechanical and electrochemical tests, it is found that the conductive hydrogel has good mechanical and electrochemical properties. When SDS was used as dispersant, the conductivity could reach 4.63 S·m−1, meanwhile, it could withstand compression stress of 1.33 MPa (corresponding dissipation energy of compression is 85.50 kJ·m−3), the elongation at break is 964%, and the corresponding breaking strength is 0.25 MPa. Under the condition of NaOH as dispersant, the conductivity could reach 4.19 S·m−1, and it could bear the compression stress of 1.13 MPa (corresponding dissipation energy of compression is 73.45 kJ·m−3), the tensile elongation at break reaches 896%, and the corresponding fracture strength is 0.14 MPa. This study provides ideas for the preparation of high-strength polyaniline-based conductive hydrogels.
2021, 38(4): 1231-1241.
doi: 10.13801/j.cnki.fhclxb.20200806.002
Abstract:
Polyester-polyamide 6 (PET-PA6) bicomponent hollow segmented-pie PET-PA6 microfiber was prepared by spunbond technology, and composited with Lyocell fibers web, and PET-PA6/Lyocell composite nonwoven materials with double-layer composite structure were prepared by high-pressure spunlace. The effects of fiber composite ratio and areal density on the performance of composite nonwoven materials were studied. The results show that the PET-PA6/Lyocell composite nonwoven material has an obvious three-dimensional structure and double-layer composite structure. After spunlacing, the fiber equivalent diameter of PET-PA6 fiber is between 3.60 and 6.50 μm, the diameter of Lyocell fiber is between 9.30 and 11.50 μm, and some fibrillation microfibrils appear. At the same areal density, PET-PA6/Lyocell nonwoven material is compared with PET-PA6 nonwoven material, the hydrophilic property has been significantly improved. When the content ratio of PET-PA6 and Lyocell fiber is 1∶1 (gram weight is 160 g/m2), the air permeability is 249.47 L/(cm2·s), increased by 117.83%; the water vapor permeabi-lity is 4 035 g/(m2·24 h), increased by 36.01%; the softness is 4.39 mm, increased by 67.56%; at the same time, the mechanical properties have been increased, and the aspect ratio of tensile strength is reduced from 1.5 to 1.2, and the phase difference is significantly reduced; but the thermal stability is slightly reduced. As the areal density increasing, the air permeability and water vapor permeability of the composite nonwoven material are gradually decreased, the softness is decreased, and the mechanical properties are increased. The combination of Lyocell fibers have significantly improved the overall performance of nonwoven materials. The three-dimensional and double-layer composite structure of nonwoven fabrics are similar to the microstructure of natural leather, and are expected to be applied in the field of microfiber synthetic leather base.
Polyester-polyamide 6 (PET-PA6) bicomponent hollow segmented-pie PET-PA6 microfiber was prepared by spunbond technology, and composited with Lyocell fibers web, and PET-PA6/Lyocell composite nonwoven materials with double-layer composite structure were prepared by high-pressure spunlace. The effects of fiber composite ratio and areal density on the performance of composite nonwoven materials were studied. The results show that the PET-PA6/Lyocell composite nonwoven material has an obvious three-dimensional structure and double-layer composite structure. After spunlacing, the fiber equivalent diameter of PET-PA6 fiber is between 3.60 and 6.50 μm, the diameter of Lyocell fiber is between 9.30 and 11.50 μm, and some fibrillation microfibrils appear. At the same areal density, PET-PA6/Lyocell nonwoven material is compared with PET-PA6 nonwoven material, the hydrophilic property has been significantly improved. When the content ratio of PET-PA6 and Lyocell fiber is 1∶1 (gram weight is 160 g/m2), the air permeability is 249.47 L/(cm2·s), increased by 117.83%; the water vapor permeabi-lity is 4 035 g/(m2·24 h), increased by 36.01%; the softness is 4.39 mm, increased by 67.56%; at the same time, the mechanical properties have been increased, and the aspect ratio of tensile strength is reduced from 1.5 to 1.2, and the phase difference is significantly reduced; but the thermal stability is slightly reduced. As the areal density increasing, the air permeability and water vapor permeability of the composite nonwoven material are gradually decreased, the softness is decreased, and the mechanical properties are increased. The combination of Lyocell fibers have significantly improved the overall performance of nonwoven materials. The three-dimensional and double-layer composite structure of nonwoven fabrics are similar to the microstructure of natural leather, and are expected to be applied in the field of microfiber synthetic leather base.
2021, 38(4): 1242-1251.
doi: 10.13801/j.cnki.fhclxb.20200807.001
Abstract:
Montmorillonite-cellulosenanofibers (MTM-CNFs) substrate materials were prepared by freeze drying. Then polyaniline (PANi) was synthesized from aniline monomers by in-situ polymerization and the ordered nanowire arrays were constructed without templates. Through the research on microstructure, synthesis mechanism, electrical conductivity and electrochemical properties of PANi/(MTM-CNFs) composite electrodes, we studied the principle of compounds prepared by one-dimensional (1D) linear material, two-dimensional (2D) nanosheets and conductive polymer. Furthermore, we also studied the preparation method of the energy-storing materials with ordered arrays. The results show that the incorporation of MTM nanosheets facilitate the in-situ growing of PANi nanorod on the substrates, Forming the ordered nanowire arrays and improving the capacitance of the composite electrodes efficiently. When the mass ratio of MTM and CNFs in the substrates is 1∶9, the PANi/(MTM-CNFs) compo-sites have the highest capacitance with the value of 596 F/g, which is 11.5 times compared to PANi/CNFs composites. With the increasement and stack of nanosheets, the capacitance of composites decreases owing to the reduced active substance. However, the value of capacitance of ternary electrodes is also significantly higher than that of binary electrodes.Furthermore, the corporation of MTM nanosheet is beneficial for the stability of columbic efficiency of the composites. During the charge and discharge cycles for 1 000 times, the value of columbic efficiency is always around 100%.
Montmorillonite-cellulosenanofibers (MTM-CNFs) substrate materials were prepared by freeze drying. Then polyaniline (PANi) was synthesized from aniline monomers by in-situ polymerization and the ordered nanowire arrays were constructed without templates. Through the research on microstructure, synthesis mechanism, electrical conductivity and electrochemical properties of PANi/(MTM-CNFs) composite electrodes, we studied the principle of compounds prepared by one-dimensional (1D) linear material, two-dimensional (2D) nanosheets and conductive polymer. Furthermore, we also studied the preparation method of the energy-storing materials with ordered arrays. The results show that the incorporation of MTM nanosheets facilitate the in-situ growing of PANi nanorod on the substrates, Forming the ordered nanowire arrays and improving the capacitance of the composite electrodes efficiently. When the mass ratio of MTM and CNFs in the substrates is 1∶9, the PANi/(MTM-CNFs) compo-sites have the highest capacitance with the value of 596 F/g, which is 11.5 times compared to PANi/CNFs composites. With the increasement and stack of nanosheets, the capacitance of composites decreases owing to the reduced active substance. However, the value of capacitance of ternary electrodes is also significantly higher than that of binary electrodes.Furthermore, the corporation of MTM nanosheet is beneficial for the stability of columbic efficiency of the composites. During the charge and discharge cycles for 1 000 times, the value of columbic efficiency is always around 100%.
2021, 38(4): 1252-1261.
doi: 10.13801/j.cnki.fhclxb.20200824.002
Abstract:
In order to endow poplar plywood with certain flame retardant properties, ammonium polyphosphate-chitosan/boron nitride (APP-CS/BN) were choosed as the flame retardant coatings, and were deposited on the plywood through layer by layer self-assembly method. The results of FTIR and SEM show that APP-CS/BN coatings are assembled on the surface of plywood to form a membrane structure, and the assembled membranes are evenly distributed on the surface of the material. Cone calorimeter (CONE) combustion tests show that APP-CS/BN self-assembled coatings effectively prolong the ignition time (TTI), reduce the heat release rate (HRR) and total heat release (THR) of the plywood, while increase the char residue which formed after combustion of the material. Compared to untreated plywoods, the ignition time of self-assembled plywoods with 15, 20, 25 APP-CS/BN layers increase by 100%, 105% and 125%, respectively; Pk-HRR is decreased by 10.15%, 22.34% and 31.82%; THR is decreased by 2.89%, 13.68% and 15.32%. The char formation rates of untreated plywood, self-assembled plywoods with 15, 20, 25 APP-CS/BN layers are 18.55%, 24.07%, 26.04% and 27.65%, respectively. In summary, the poplar plywood exhibits good flame retardant properties via layer-by-layer self-assembly flame retardant treatment. However, when the number of self-assembly layers is from 20 to 25, the increment amplitude of flame retardancy of plywood becomes slower. In this study, the suitable self-assembly coatings are 20-25 layers.
In order to endow poplar plywood with certain flame retardant properties, ammonium polyphosphate-chitosan/boron nitride (APP-CS/BN) were choosed as the flame retardant coatings, and were deposited on the plywood through layer by layer self-assembly method. The results of FTIR and SEM show that APP-CS/BN coatings are assembled on the surface of plywood to form a membrane structure, and the assembled membranes are evenly distributed on the surface of the material. Cone calorimeter (CONE) combustion tests show that APP-CS/BN self-assembled coatings effectively prolong the ignition time (TTI), reduce the heat release rate (HRR) and total heat release (THR) of the plywood, while increase the char residue which formed after combustion of the material. Compared to untreated plywoods, the ignition time of self-assembled plywoods with 15, 20, 25 APP-CS/BN layers increase by 100%, 105% and 125%, respectively; Pk-HRR is decreased by 10.15%, 22.34% and 31.82%; THR is decreased by 2.89%, 13.68% and 15.32%. The char formation rates of untreated plywood, self-assembled plywoods with 15, 20, 25 APP-CS/BN layers are 18.55%, 24.07%, 26.04% and 27.65%, respectively. In summary, the poplar plywood exhibits good flame retardant properties via layer-by-layer self-assembly flame retardant treatment. However, when the number of self-assembly layers is from 20 to 25, the increment amplitude of flame retardancy of plywood becomes slower. In this study, the suitable self-assembly coatings are 20-25 layers.
2021, 38(4): 1262-1271.
doi: 10.13801/j.cnki.fhclxb.20200723.003
Abstract:
The chitosan/magnetic graphene oxide (CS/MGO) composites were synthesized by the modified Hummers and hydrothermal methods and applied as an adsorbent for the removal of methyl orange (MO). CS/MGO composite was characterized by SEM, XRD, BET, FTIR and a vibrating sample magnetometer (VSM). Results show that Fe3O4 nanoparticles mainly exist on the surface of graphene oxide and chitosan (CS) composite with less aggregation and a good magnetic response. In addition, the thermal stability is good, and the specific surface area of CS/MGO is 36.873 m2·g−1. CS/MGO composite could be easily separated by magnetic separation and demonstrates good stability and reusability. The effects of pH, initial concentration of MO, CS/MGO composite amount and regeneration on the removal of MO were systematically investigated. The results reveal that the initial MO concentration of 20 mg·L−1, CS/MGO composite amount of 0.12 g·L−1, and pH=3 lead to the adsorption equilibrium after 210 min. CS/MGO composite maintains 83.7% of its maximum MO adsorption capacity after five consecutive cycles. The adsorption process conforms to the pseudo-second-order kinetic model, and the adsorption isotherms conform to the Langmuir model. The maximum adsorption amounts at 298.15, 303.15 and 308.15 K are 129.96, 138.94 and 145.03 mg·g−1, respectively. The adsorption thermodynamics indicate that the adsorption process is endothermic; entropy increases the spontaneous adsorption process.
The chitosan/magnetic graphene oxide (CS/MGO) composites were synthesized by the modified Hummers and hydrothermal methods and applied as an adsorbent for the removal of methyl orange (MO). CS/MGO composite was characterized by SEM, XRD, BET, FTIR and a vibrating sample magnetometer (VSM). Results show that Fe3O4 nanoparticles mainly exist on the surface of graphene oxide and chitosan (CS) composite with less aggregation and a good magnetic response. In addition, the thermal stability is good, and the specific surface area of CS/MGO is 36.873 m2·g−1. CS/MGO composite could be easily separated by magnetic separation and demonstrates good stability and reusability. The effects of pH, initial concentration of MO, CS/MGO composite amount and regeneration on the removal of MO were systematically investigated. The results reveal that the initial MO concentration of 20 mg·L−1, CS/MGO composite amount of 0.12 g·L−1, and pH=3 lead to the adsorption equilibrium after 210 min. CS/MGO composite maintains 83.7% of its maximum MO adsorption capacity after five consecutive cycles. The adsorption process conforms to the pseudo-second-order kinetic model, and the adsorption isotherms conform to the Langmuir model. The maximum adsorption amounts at 298.15, 303.15 and 308.15 K are 129.96, 138.94 and 145.03 mg·g−1, respectively. The adsorption thermodynamics indicate that the adsorption process is endothermic; entropy increases the spontaneous adsorption process.
2021, 38(4): 1272-1282.
doi: 10.13801/j.cnki.fhclxb.20200730.001
Abstract:
The polyaniline nanowire/self-supported graphene (PANI/SGr) composite was synthesized by one-step electrochemical exfoliation and electrodeposition method using graphite paper. The directional migration of electrolyte ions and the electropolymerization of aniline monomers through the electrical field simultaneously occurred in the mixed solution including Na2SO4, HCl and aniline (An) monomers. The stability of the PANI/SGr composite is enhanced by the combination of the new-born SGr with high activity and PANI. The uniform distribution of the nanowire-like PANI is achieved on the surface of the SGr. The PANI nanowires lead to the formation of the three-dimensional network architecture, where the existence of pores facilitates the diffusion of electrolyte ions into the internal structure of the PANI/SGr composite. The electrochemical tests of the PANI/SGr composite were conducted as a supercapacitor electrode material. The specific capacitance of 453 F·g−1 at a scan rate of 2 mV·s−1 is achieved. The rate capability of the PANI/SGr composite at the current densities of 0.5-10 A·g−1 is up to 73.1%. The cycling stability of the PANI/SGr composite is as high as 87.3% after 10000 discharge-charge cycles at the current density of 1 A·g−1. All of these results indicate that the PANI/SGr composite possesses good capacitive performance and excellent cycling stability. The PANI/SGr composite is promising for supercapacitor electrode materials.
The polyaniline nanowire/self-supported graphene (PANI/SGr) composite was synthesized by one-step electrochemical exfoliation and electrodeposition method using graphite paper. The directional migration of electrolyte ions and the electropolymerization of aniline monomers through the electrical field simultaneously occurred in the mixed solution including Na2SO4, HCl and aniline (An) monomers. The stability of the PANI/SGr composite is enhanced by the combination of the new-born SGr with high activity and PANI. The uniform distribution of the nanowire-like PANI is achieved on the surface of the SGr. The PANI nanowires lead to the formation of the three-dimensional network architecture, where the existence of pores facilitates the diffusion of electrolyte ions into the internal structure of the PANI/SGr composite. The electrochemical tests of the PANI/SGr composite were conducted as a supercapacitor electrode material. The specific capacitance of 453 F·g−1 at a scan rate of 2 mV·s−1 is achieved. The rate capability of the PANI/SGr composite at the current densities of 0.5-10 A·g−1 is up to 73.1%. The cycling stability of the PANI/SGr composite is as high as 87.3% after 10000 discharge-charge cycles at the current density of 1 A·g−1. All of these results indicate that the PANI/SGr composite possesses good capacitive performance and excellent cycling stability. The PANI/SGr composite is promising for supercapacitor electrode materials.
2021, 38(4): 1283-1291.
doi: 10.13801/j.cnki.fhclxb.20200730.002
Abstract:
In order to study the effect of polyacrylamide (PAM) on the early strength and failure form of lime stabilized soil, through the California bearing ratio (CBR) test, triaxial unconsolidated undrained shear test and super depth of field three-dimensional microscope, the early strength of PAM-lime stabilized soil with different PAM contents was analyzed. The solidification mechanism of PAM on the lime stabilized soil was explored. The research indicates that PAM can effectively improve the early strength of the lime stabilized soil. With the increase of PAM content, the early strength of the lime stabilized soil shows a trend of increasing first and then decreasing. PAM can improve the brittle failure characteristics of lime stable soil, and weak strain hardening occurs. But when the PAM content exceeds 0.36wt%, the lime stable soil exhibits brittle failure characteristics under low confining pressure of 50 kPa. When the content of lime is 8wt% and the content of PAM is 0.36wt%, the improvement effect of the soil is better. Under the condition of this dosage, the combined action of PAM and lime can better promote the agglomeration of soil particles, strengthen the soil structure and increase the surface roughness of the soil. The internal friction angle and cohesion can be improved and the shear strength will also be enhanced.
In order to study the effect of polyacrylamide (PAM) on the early strength and failure form of lime stabilized soil, through the California bearing ratio (CBR) test, triaxial unconsolidated undrained shear test and super depth of field three-dimensional microscope, the early strength of PAM-lime stabilized soil with different PAM contents was analyzed. The solidification mechanism of PAM on the lime stabilized soil was explored. The research indicates that PAM can effectively improve the early strength of the lime stabilized soil. With the increase of PAM content, the early strength of the lime stabilized soil shows a trend of increasing first and then decreasing. PAM can improve the brittle failure characteristics of lime stable soil, and weak strain hardening occurs. But when the PAM content exceeds 0.36wt%, the lime stable soil exhibits brittle failure characteristics under low confining pressure of 50 kPa. When the content of lime is 8wt% and the content of PAM is 0.36wt%, the improvement effect of the soil is better. Under the condition of this dosage, the combined action of PAM and lime can better promote the agglomeration of soil particles, strengthen the soil structure and increase the surface roughness of the soil. The internal friction angle and cohesion can be improved and the shear strength will also be enhanced.
2021, 38(4): 1292-1301.
doi: 10.13801/j.cnki.fhclxb.20200805.001
Abstract:
In order to study the bending performance of engineered cementitious composites (ECC) reinforced by high-strength stainless steel wire strand meshes, the four-point bending tests were carried out on 8 high-strength stainless steel wire strands mesh reinforced ECC thin plate specimens designed in two groups, which considered two factors including the reinforcement ratio of longitudinal high-strength stainless steel wire strands and ECC compressive and tensile strength. The results show that with an increase in the reinforcement ratio of longitudinal high-strength stainless steel wire strands, the cracking load is basically unchanged, but the peak load increases significantly, and the peak displacement decreases, that is the ductility is reduced. In addition, the reasonable reinforcement ratio of longitudinal high-strength stainless steel wire strands should be less than 0.48%. The cracking load and peak load of the high-strength stainless steel wire strand mesh reinforced ECC bending specimen increases as the ECC strength increasing. After ECC cracking, the steel wire strands and the ECC in the tensile zone are tensioned together. When the applied load reaches 80% of the peak load, the maximum crack width at the bottom is only 0.08 mm. At peak load, the maximum crack width doesn’t exceed 0.55 mm, and the compressive strain of the ECC in the compression zone reaches 0.01. When the ECC is crushed, the maximum deflection in the mid-span reaches 1/15 of the span. These phenomena show that the high-strength stainless steel wire strand mesh reinforced ECC studied in the paper has good crack resistance and ductility.
In order to study the bending performance of engineered cementitious composites (ECC) reinforced by high-strength stainless steel wire strand meshes, the four-point bending tests were carried out on 8 high-strength stainless steel wire strands mesh reinforced ECC thin plate specimens designed in two groups, which considered two factors including the reinforcement ratio of longitudinal high-strength stainless steel wire strands and ECC compressive and tensile strength. The results show that with an increase in the reinforcement ratio of longitudinal high-strength stainless steel wire strands, the cracking load is basically unchanged, but the peak load increases significantly, and the peak displacement decreases, that is the ductility is reduced. In addition, the reasonable reinforcement ratio of longitudinal high-strength stainless steel wire strands should be less than 0.48%. The cracking load and peak load of the high-strength stainless steel wire strand mesh reinforced ECC bending specimen increases as the ECC strength increasing. After ECC cracking, the steel wire strands and the ECC in the tensile zone are tensioned together. When the applied load reaches 80% of the peak load, the maximum crack width at the bottom is only 0.08 mm. At peak load, the maximum crack width doesn’t exceed 0.55 mm, and the compressive strain of the ECC in the compression zone reaches 0.01. When the ECC is crushed, the maximum deflection in the mid-span reaches 1/15 of the span. These phenomena show that the high-strength stainless steel wire strand mesh reinforced ECC studied in the paper has good crack resistance and ductility.
2021, 38(4): 1302-1312.
doi: 10.13801/j.cnki.fhclxb.20200826.005
Abstract:
Bamboo is a kind of natural composite material, which is composed of bamboo fiber as reinforcement and porous lignin as matrix. In this paper, based on the microstructure of bamboo, the porous polyethersulfone (PES) matrix with gradient pore size distribution was deposited on the surface of glass fiber (GF) by immersion precipitation phase transformation method of high-performance thermoplastic polymer. The bamboo like porous polyethersulfone matrix monofilament glass fiber composite(GF/PES) was prepared, and its microstructure, tensile mechanical properties and “temperature modulus” response were studied. Based on the good energy absorption of the gradient porous PES matrix and its repair effect on the micro defects on the surface of GF, the tensile strength and elongation at break of GF/PES can be increased by 39.11% and 58.1%, respectively. In addition, the porous polymer matrix also can be used as carrier of various functional materials. For example, filling water in pores of porous PES can make a significant modulus change of GF/PES. Therefore, “temperature-modulus” intelligent response composite are obtained.
Bamboo is a kind of natural composite material, which is composed of bamboo fiber as reinforcement and porous lignin as matrix. In this paper, based on the microstructure of bamboo, the porous polyethersulfone (PES) matrix with gradient pore size distribution was deposited on the surface of glass fiber (GF) by immersion precipitation phase transformation method of high-performance thermoplastic polymer. The bamboo like porous polyethersulfone matrix monofilament glass fiber composite(GF/PES) was prepared, and its microstructure, tensile mechanical properties and “temperature modulus” response were studied. Based on the good energy absorption of the gradient porous PES matrix and its repair effect on the micro defects on the surface of GF, the tensile strength and elongation at break of GF/PES can be increased by 39.11% and 58.1%, respectively. In addition, the porous polymer matrix also can be used as carrier of various functional materials. For example, filling water in pores of porous PES can make a significant modulus change of GF/PES. Therefore, “temperature-modulus” intelligent response composite are obtained.
2021, 38(4): 979-996.
doi: 10.13801/j.cnki.fhclxb.20210118.003
Abstract:
Applying additive manufacturing (AM), also termed as three-dimensional printing (3D printing), is an emerging technology for creating objects by sequential layering. Recently, the exponential research on improving mechanical performance of 3D printed productions by introducing continuous fibre-reinforcement has contributed to develop high-performance polymeric composites. In the present review, by introducing brief history of AM technique for polymerics, the positive influence on improving performance of printed productions resulted from technology- and material-revolution were described. Following that, the review focused on the mechanism of the fused deposition modelling (FDM) method for fabricating continuous fibre reinforced composites, as well as the advantages and problems of the mechanical performance for productions. Additionally, the probable contributing factors were reviewed herein from the aspects of materials, process parameters and meso/microstructures of the printed composites. The review might be helpful to the readers who are concerning with the issues of the FDM technique.
Applying additive manufacturing (AM), also termed as three-dimensional printing (3D printing), is an emerging technology for creating objects by sequential layering. Recently, the exponential research on improving mechanical performance of 3D printed productions by introducing continuous fibre-reinforcement has contributed to develop high-performance polymeric composites. In the present review, by introducing brief history of AM technique for polymerics, the positive influence on improving performance of printed productions resulted from technology- and material-revolution were described. Following that, the review focused on the mechanism of the fused deposition modelling (FDM) method for fabricating continuous fibre reinforced composites, as well as the advantages and problems of the mechanical performance for productions. Additionally, the probable contributing factors were reviewed herein from the aspects of materials, process parameters and meso/microstructures of the printed composites. The review might be helpful to the readers who are concerning with the issues of the FDM technique.
2021, 38(4): 997-1019.
doi: 10.13801/j.cnki.fhclxb.20201210.004
Abstract:
Polymer piezoelectric materials polyvinylidene fluoride (PVDF) and its copolymers P(VDF-TRFE) and P(VDF-HFP) are typical organic polymer materials with piezoelectric properties. Currently, these materials attract great attention in academic and application area for their good mechanical properties, corrosion resistance, biocompatibility and easy processing. However, compared with the traditional inorganic piezoelectric ceramic materials, the piezoelectric constant of polymer piezoelectric materials is still relatively low, so improving the piezoelectric properties of such polymer piezoelectric materials has become one of the research hotspots at home and abroad. In this paper, the methods of improving the piezoelectric properties by combining PVDF and its copolymers with different functional materials at national and international levels in recent years are summarized, and the advantages and disadvantages of different types of fillers doped with different polymer piezoelectric materials and their development trends are prospected.
Polymer piezoelectric materials polyvinylidene fluoride (PVDF) and its copolymers P(VDF-TRFE) and P(VDF-HFP) are typical organic polymer materials with piezoelectric properties. Currently, these materials attract great attention in academic and application area for their good mechanical properties, corrosion resistance, biocompatibility and easy processing. However, compared with the traditional inorganic piezoelectric ceramic materials, the piezoelectric constant of polymer piezoelectric materials is still relatively low, so improving the piezoelectric properties of such polymer piezoelectric materials has become one of the research hotspots at home and abroad. In this paper, the methods of improving the piezoelectric properties by combining PVDF and its copolymers with different functional materials at national and international levels in recent years are summarized, and the advantages and disadvantages of different types of fillers doped with different polymer piezoelectric materials and their development trends are prospected.
2021, 38(4): 1020-1028.
doi: 10.13801/j.cnki.fhclxb.20201218.003
Abstract:
MXene is a novel kind of two-dimensional material with similar structure with graphene, which is composed of transition metal carbide, nitride or carbonitrides. Usually, it has excellent physical and chemical properties, such as large specific surface area, good electrical conductivity, excellent catalysis, excellent self-lubricating property, and abundant surface functional groups, thus showing broad application prospects in varied fields. In this paper, in view of easy stacking of MXene nanosheets and the poor compatibility with polymer matrix, the research progress of MXene surface functional modification was reviewed, including organic, inorganic and organic-inorga-nic hybrid modification methods. It also summarized the applications research progress of MXene in the fields of energy storage, catalysis and tribology, as well as prospected the future research direction.
MXene is a novel kind of two-dimensional material with similar structure with graphene, which is composed of transition metal carbide, nitride or carbonitrides. Usually, it has excellent physical and chemical properties, such as large specific surface area, good electrical conductivity, excellent catalysis, excellent self-lubricating property, and abundant surface functional groups, thus showing broad application prospects in varied fields. In this paper, in view of easy stacking of MXene nanosheets and the poor compatibility with polymer matrix, the research progress of MXene surface functional modification was reviewed, including organic, inorganic and organic-inorga-nic hybrid modification methods. It also summarized the applications research progress of MXene in the fields of energy storage, catalysis and tribology, as well as prospected the future research direction.
2021, 38(4): 1029-1042.
doi: 10.13801/j.cnki.fhclxb.20201021.002
Abstract:
Most textile composites are anisotropic materials, and their mechanical properties strongly depend on the fiber orientations in the preforms after forming process. In order to guarantee that the fiber orientation of the preforms meeting the requirements of product design, at present, many nondestructive testing technologies have been employed for textile composite preform forming process and quality detection. In this paper, combines with the development trends of textile composite preform preparing technology and nondestructive testing technology requirements on preform forming process, a variety of nondestructive testing technologies which are widely used in scientific research and industrial production are reviewed, including contact measurement technology, optical testing technology, thermography testing technology, eddy current testing technology and radiographic testing technology. The technical characteristics, application and existing problems of each method are summarized. Finally the development trend and the challenges of nondestructive testing technologies for textile composite preform forming process are discussed.
Most textile composites are anisotropic materials, and their mechanical properties strongly depend on the fiber orientations in the preforms after forming process. In order to guarantee that the fiber orientation of the preforms meeting the requirements of product design, at present, many nondestructive testing technologies have been employed for textile composite preform forming process and quality detection. In this paper, combines with the development trends of textile composite preform preparing technology and nondestructive testing technology requirements on preform forming process, a variety of nondestructive testing technologies which are widely used in scientific research and industrial production are reviewed, including contact measurement technology, optical testing technology, thermography testing technology, eddy current testing technology and radiographic testing technology. The technical characteristics, application and existing problems of each method are summarized. Finally the development trend and the challenges of nondestructive testing technologies for textile composite preform forming process are discussed.
2021, 38(4): 1043-1053.
doi: 10.13801/j.cnki.fhclxb.20201202.002
Abstract:
Graphene oxide (GO), as an oxygen-containing derivative of graphene, has attracted wide attention for its excellent physical and chemical properties. In this paper, the antibacterial mechanism of graphene oxide was analyzed; the research progress of antibacterial composite materials of graphene oxide and metal particles, metal oxides and organics were summarized; and the antibacterial finishing methods and their advantages and disadvantages of textiles based on graphene oxide and its composite materials were discussed again. Finally, the research trends of graphene oxide and its composite materials in textile antibacterial finishing were further analyzed.
Graphene oxide (GO), as an oxygen-containing derivative of graphene, has attracted wide attention for its excellent physical and chemical properties. In this paper, the antibacterial mechanism of graphene oxide was analyzed; the research progress of antibacterial composite materials of graphene oxide and metal particles, metal oxides and organics were summarized; and the antibacterial finishing methods and their advantages and disadvantages of textiles based on graphene oxide and its composite materials were discussed again. Finally, the research trends of graphene oxide and its composite materials in textile antibacterial finishing were further analyzed.
2021, 38(4): 1054-1065.
doi: 10.13801/j.cnki.fhclxb.20201224.001
Abstract:
The high-quality development of the integrated circuit industry puts forward higher requirements for the insulation properties and thermal conductivity of supporting materials in its industrial chain. The basic research of carbon-based materials with excellent properties, such as high thermal conductivity, low density and active surface interface in polymer matrix composites, is essential for the performance improvement and application development of high-performance insulating and thermally conductive materials. This article systematically reviews the research progress of carbon-based fillers in polymer matrix insulating and thermally conductive composites. Firstly, the thermal conduction mechanism, insulation mechanism, and insulation and thermal conduction compatibility mechanism of polymer matrix composites were introduced. Secondly, the surface treatment, spatial structure and distribution control methods of carbon-based fillers were reviewed, and the control mechanism of insulation properties and thermal conductivity wass studied. Finally, the unresolved scientific problems, technical difficulties and future development directions in the research work of polymer matrix insulating and thermally conductive composites were summarized and prospected.
The high-quality development of the integrated circuit industry puts forward higher requirements for the insulation properties and thermal conductivity of supporting materials in its industrial chain. The basic research of carbon-based materials with excellent properties, such as high thermal conductivity, low density and active surface interface in polymer matrix composites, is essential for the performance improvement and application development of high-performance insulating and thermally conductive materials. This article systematically reviews the research progress of carbon-based fillers in polymer matrix insulating and thermally conductive composites. Firstly, the thermal conduction mechanism, insulation mechanism, and insulation and thermal conduction compatibility mechanism of polymer matrix composites were introduced. Secondly, the surface treatment, spatial structure and distribution control methods of carbon-based fillers were reviewed, and the control mechanism of insulation properties and thermal conductivity wass studied. Finally, the unresolved scientific problems, technical difficulties and future development directions in the research work of polymer matrix insulating and thermally conductive composites were summarized and prospected.
2021, 38(4): 1066-1075.
doi: 10.13801/j.cnki.fhclxb.20201229.002
Abstract:
Due to the inhomogeneity of graphene composites (GC) made of randomly stacked graphene, the piezoresistive sensing performance of GC is closely related to the size of meso element. According to the microstructure characteristics of GC, a calculation method for piezoresistive sensing performance of GC was developed. The electron percolation probability, initial sheet resistance and relative resistance-strain relationship of GC were calculated in turn. The results show that the electron percolation probability of GC increases with the increase of graphene area fraction. The percolation threshold of GC with large aspect ratio graphene is lower, and the minimum area fraction of graphene to keep the electron transport network connected is 0.5. The minimum side length of GC representative element can be determined by its initial sheet resistance. GC with large area fraction has smaller representative element, and the minimum ratios of the side length of representative element with area fraction of 1.2, 1.4, 1.6, 1.8 and 2.0 to graphene side length are 35, 30, 25, 20 and 15, respectively. Finally, the calculation results of GC representative elements confirm that the linear sensing stage and total sensing range of GC can be enlarged by increasing the area fraction or aspect ratio of graphene.
Due to the inhomogeneity of graphene composites (GC) made of randomly stacked graphene, the piezoresistive sensing performance of GC is closely related to the size of meso element. According to the microstructure characteristics of GC, a calculation method for piezoresistive sensing performance of GC was developed. The electron percolation probability, initial sheet resistance and relative resistance-strain relationship of GC were calculated in turn. The results show that the electron percolation probability of GC increases with the increase of graphene area fraction. The percolation threshold of GC with large aspect ratio graphene is lower, and the minimum area fraction of graphene to keep the electron transport network connected is 0.5. The minimum side length of GC representative element can be determined by its initial sheet resistance. GC with large area fraction has smaller representative element, and the minimum ratios of the side length of representative element with area fraction of 1.2, 1.4, 1.6, 1.8 and 2.0 to graphene side length are 35, 30, 25, 20 and 15, respectively. Finally, the calculation results of GC representative elements confirm that the linear sensing stage and total sensing range of GC can be enlarged by increasing the area fraction or aspect ratio of graphene.
2021, 38(4): 1076-1086.
doi: 10.13801/j.cnki.fhclxb.20210302.006
Abstract:
Composite laminates are widely used in aerospace and other fields. Delamination is the main damage form in composite laminates, which has a significant impact on the strength and stiffness of composite structures. It’s one of the hot issues which is limited in major engineering applications. It often takes a lot of time and cost to study composite structure by experimental methods. Mature finite element numerical simulation technology can realize the layered behavior simulation of composite structures at a low cost and become an important means for delamination damage research. In this paper, from the perspective of numerical simulation, the research results on the interface damage of fiber reinforced composite materials at home and abroad are summarized, and the current main methods are virtual crack closure technology (VCCT), cohesive force model (CZM) and extended finite element method (XFEM). Finally, the text makes a prospect for the future work.
Composite laminates are widely used in aerospace and other fields. Delamination is the main damage form in composite laminates, which has a significant impact on the strength and stiffness of composite structures. It’s one of the hot issues which is limited in major engineering applications. It often takes a lot of time and cost to study composite structure by experimental methods. Mature finite element numerical simulation technology can realize the layered behavior simulation of composite structures at a low cost and become an important means for delamination damage research. In this paper, from the perspective of numerical simulation, the research results on the interface damage of fiber reinforced composite materials at home and abroad are summarized, and the current main methods are virtual crack closure technology (VCCT), cohesive force model (CZM) and extended finite element method (XFEM). Finally, the text makes a prospect for the future work.
2021, 38(4): 1087-1097.
doi: 10.13801/j.cnki.fhclxb.20200721.001
Abstract:
With poly(vinylidene fluoride) (PVDF) as matrix, 15wt% of CTAB modified silicon carbide nanowhisker (SiCw) and nano BaTiO3 (BT) particles modified by KH550 as fillers, the BT-SiCw/PVDF ternary composite film was prepared. The composition and the micro-morphology of the samples were investigated by FTIR, XRD and SEM, respectively. It was illustrated that modified BT could be well dispersed in PVDF matrix by SEM analysis. The results show that KH550 particles can be successfully modified BT and BT does not change the crystal structure, SiCw and BT can be well dispersed in the PVDF matrix. The dielectric constant of the BT-SiCw/PVDF composite film is as high as 33 while the dielectric loss is only 0.154 correspondingly at the frequency of 500 Hz with loading of 10wt% BT at room temperature and reach optimal. The dielectric constant and dielectric loss of the composite film increase with increasing the temperature and reach the maximum value (freqyency f=500 Hz, dielectric constant εrmax=110, dielectric loss
With poly(vinylidene fluoride) (PVDF) as matrix, 15wt% of CTAB modified silicon carbide nanowhisker (SiCw) and nano BaTiO3 (BT) particles modified by KH550 as fillers, the BT-SiCw/PVDF ternary composite film was prepared. The composition and the micro-morphology of the samples were investigated by FTIR, XRD and SEM, respectively. It was illustrated that modified BT could be well dispersed in PVDF matrix by SEM analysis. The results show that KH550 particles can be successfully modified BT and BT does not change the crystal structure, SiCw and BT can be well dispersed in the PVDF matrix. The dielectric constant of the BT-SiCw/PVDF composite film is as high as 33 while the dielectric loss is only 0.154 correspondingly at the frequency of 500 Hz with loading of 10wt% BT at room temperature and reach optimal. The dielectric constant and dielectric loss of the composite film increase with increasing the temperature and reach the maximum value (freqyency f=500 Hz, dielectric constant εrmax=110, dielectric loss
2021, 38(4): 1098-1106.
doi: 10.13801/j.cnki.fhclxb.20200831.004
Abstract:
Using N-methylol acrylamide (N-MA) and polyethylene glycol (PEG) eutectic as raw materials, poly-N-methylol acrylamide (PN-MA)/PEG semi-interpenetrating network was prepared by emulsion polymerization (SIPN) composite phase change material (CPCM). The structure and performance of (PN-MA)/PEG CPCM were characterized using FTIR, XRD, differential scanning calorimeter (DSC), SEM, EDS and other methods. The results show that the crystallization enthalpy and melting enthalpy of the obtained CPCM reach 78.38 J/g and 82.31 J/g, and the crystallization temperature and melting temperature are 36.88°C and 32.05°C respectively; the interaction between PN-MA and PEG in CPCM is physical link, no other chemical reaction occurs; the obtained CPCM is spherical and the size is relatively uniform. The small spheres with a diameter of about 200 nm are aggregated to form large spheres with a diameter of 10 μm to 15 μm. The sphere presents a dense three-dimensional net cage structure; PEG is well supported under the constraints of the cross-linked PN-MA network, and still has good crystallization performance.
Using N-methylol acrylamide (N-MA) and polyethylene glycol (PEG) eutectic as raw materials, poly-N-methylol acrylamide (PN-MA)/PEG semi-interpenetrating network was prepared by emulsion polymerization (SIPN) composite phase change material (CPCM). The structure and performance of (PN-MA)/PEG CPCM were characterized using FTIR, XRD, differential scanning calorimeter (DSC), SEM, EDS and other methods. The results show that the crystallization enthalpy and melting enthalpy of the obtained CPCM reach 78.38 J/g and 82.31 J/g, and the crystallization temperature and melting temperature are 36.88°C and 32.05°C respectively; the interaction between PN-MA and PEG in CPCM is physical link, no other chemical reaction occurs; the obtained CPCM is spherical and the size is relatively uniform. The small spheres with a diameter of about 200 nm are aggregated to form large spheres with a diameter of 10 μm to 15 μm. The sphere presents a dense three-dimensional net cage structure; PEG is well supported under the constraints of the cross-linked PN-MA network, and still has good crystallization performance.
2021, 38(4): 1107-1114.
doi: 10.13801/j.cnki.fhclxb.20200623.002
Abstract:
The structural design, manufacture and mechanical evaluation of an auxetic advanced grid structure (AGS) composite were investigated. The mechanical behavior of the auxetic AGS composite under the compressive loading was simulated via finite element method (FEM). The auxetic AGS composite was fabricated via autoclave processing, and the processing quality and mechanical properties were evaluated. The simulation results show that the auxetic AGS composite after deformation is in a corrugation shape, which is different from the saddle deformation shape of the orthogonal AGS composite. Compared with the orthogonal AGS composite, the transverse expansion is lower and the stress is more uniformly distributed. An 30° included angle between grid and axis is the most optimal structure for the auxetic AGS composite. Excellent manufacturing quality and superior mechanical properties are found for the MT300/603 carbon fiber/epoxy auxetic AGS composite. The mechanical experiment results show the optimal MT300/603 auxetic AGS composites have a compression modulus of 65.92 GPa and a compression failure load of 64.65 kN. The failure occurs between the grid and skin at the crossing of the grids, showing a higher compression strength than the orthogonal AGS composite. The optimal MT300/603 auxetic AGS composite exhibits a characteristic negative Poisson’s ratio. The AGS composite structure with superior overall mechanical performance can potentially be used on aerospace structures.
The structural design, manufacture and mechanical evaluation of an auxetic advanced grid structure (AGS) composite were investigated. The mechanical behavior of the auxetic AGS composite under the compressive loading was simulated via finite element method (FEM). The auxetic AGS composite was fabricated via autoclave processing, and the processing quality and mechanical properties were evaluated. The simulation results show that the auxetic AGS composite after deformation is in a corrugation shape, which is different from the saddle deformation shape of the orthogonal AGS composite. Compared with the orthogonal AGS composite, the transverse expansion is lower and the stress is more uniformly distributed. An 30° included angle between grid and axis is the most optimal structure for the auxetic AGS composite. Excellent manufacturing quality and superior mechanical properties are found for the MT300/603 carbon fiber/epoxy auxetic AGS composite. The mechanical experiment results show the optimal MT300/603 auxetic AGS composites have a compression modulus of 65.92 GPa and a compression failure load of 64.65 kN. The failure occurs between the grid and skin at the crossing of the grids, showing a higher compression strength than the orthogonal AGS composite. The optimal MT300/603 auxetic AGS composite exhibits a characteristic negative Poisson’s ratio. The AGS composite structure with superior overall mechanical performance can potentially be used on aerospace structures.
2021, 38(4): 1115-1127.
doi: 10.13801/j.cnki.fhclxb.20200806.001
Abstract:
Carbon fiber reinforced epoxy composite-aluminium alloy (CFRP-Al) stub column has the characteristics of lightweight, high strength and good ductility, showing a promising application prospect in long-span space structures. However, the research on its mechanical properties is basically in a blank state at home and abroad. For this reason, the theoretical analysis, experimental and numerical researches on CFRP-Al stub column were carried out in this paper. The equivalent elastic constants of CFRP-Al stub column were derived. The axial compression tests of six stub columns were completed and the axial bearing capacity and the failure mode of the short columns were obtained. The load-displacement curves calculated by the theory of elasticity show a good agreement with the test curves. Two numerical models, the layer-by-layer refinement model and the overall equivalent simplified model, were established using ABAQUS. The results of the two numerical models were compared with the experimental results. The comparison shows that both numerical models can well simulate the axial compression performance of CFRP-Al stub columns.
Carbon fiber reinforced epoxy composite-aluminium alloy (CFRP-Al) stub column has the characteristics of lightweight, high strength and good ductility, showing a promising application prospect in long-span space structures. However, the research on its mechanical properties is basically in a blank state at home and abroad. For this reason, the theoretical analysis, experimental and numerical researches on CFRP-Al stub column were carried out in this paper. The equivalent elastic constants of CFRP-Al stub column were derived. The axial compression tests of six stub columns were completed and the axial bearing capacity and the failure mode of the short columns were obtained. The load-displacement curves calculated by the theory of elasticity show a good agreement with the test curves. Two numerical models, the layer-by-layer refinement model and the overall equivalent simplified model, were established using ABAQUS. The results of the two numerical models were compared with the experimental results. The comparison shows that both numerical models can well simulate the axial compression performance of CFRP-Al stub columns.
2021, 38(4): 1128-1138.
doi: 10.13801/j.cnki.fhclxb.20200805.003
Abstract:
In order to elucidate the adsorption mechanism of the amino methylene phosphonic acid chelating resin (D418) with high efficiency for removal of Cu(II) from wastewater, the influence of pH, ionic strength, contact time and temperature were detailly investigated by adsorption experiment. Meanwhile, adsorption kinetics, adsorption isotherms and site energy distribution theory were used to explain the removal mechanism of Cu(II) on the D418 resin. The results demonstrate that the optimal removal rate of Cu(II) on the D418 resin reaches to 97.20% at the initial pH=9.00, and the change of zeta potential on the influence of removal rate is well compatible with Boltzmann model. Furthermore, the removal efficiency of Cu(II) increases with the ionic strength at the range of 0-0.10 mol/L. According to the comparisons of the linear correlation coefficient values, the data of the adsorption kinetics fits well to the intra-particle diffusion while isotherm model data fits well to the Sips model. Based on the Sips model, the isotherm parameters and the energy distributions of adsorption sites were also conducted, and the result shows that the process of the Cu(II) adsorption on the D418 resin is spontaneous and endothermic. Cu(II) is preferentially adsorbed to the high- energy sites and to the low-energy sites. Based on the XPS and FTIR analysis, the adsorption mechanism of the Cu(II) ions is mainly attributed to the electrostatic interaction, the chemical precipitation and the inner-sphere complexation.
In order to elucidate the adsorption mechanism of the amino methylene phosphonic acid chelating resin (D418) with high efficiency for removal of Cu(II) from wastewater, the influence of pH, ionic strength, contact time and temperature were detailly investigated by adsorption experiment. Meanwhile, adsorption kinetics, adsorption isotherms and site energy distribution theory were used to explain the removal mechanism of Cu(II) on the D418 resin. The results demonstrate that the optimal removal rate of Cu(II) on the D418 resin reaches to 97.20% at the initial pH=9.00, and the change of zeta potential on the influence of removal rate is well compatible with Boltzmann model. Furthermore, the removal efficiency of Cu(II) increases with the ionic strength at the range of 0-0.10 mol/L. According to the comparisons of the linear correlation coefficient values, the data of the adsorption kinetics fits well to the intra-particle diffusion while isotherm model data fits well to the Sips model. Based on the Sips model, the isotherm parameters and the energy distributions of adsorption sites were also conducted, and the result shows that the process of the Cu(II) adsorption on the D418 resin is spontaneous and endothermic. Cu(II) is preferentially adsorbed to the high- energy sites and to the low-energy sites. Based on the XPS and FTIR analysis, the adsorption mechanism of the Cu(II) ions is mainly attributed to the electrostatic interaction, the chemical precipitation and the inner-sphere complexation.
2021, 38(4): 1139-1146.
doi: 10.13801/j.cnki.fhclxb.20200624.001
Abstract:
In order to reduce the amount of HCl used in the hydrated ferrous oxide (HFO) composite adsorbents preparation process, which frequently caused serious equipment corrosion, safe and environmental problems, several adsorbents were prepared with various HCl concentrations. The effectiveness of P adsorption by the adsorbents were investigated at various perspectives, including adsorption kinetics, adsorption isotherms, effect of pH, co-existing ions and desorption methods. Experimental results demonstrate that phosphate adsorption capacity of HFO composite adsorbents doesn’t decrease significantly with the decreasing HCl concentration (from 2 mol·L−1 to 0.5 mol·L−1). The maximum P adsorption capacity of HFO composite adsorbent prepared at 0.5 mol·L−1 HCl is 29.67 mg·g−1, which is higher than the corresponding value of D201 resin (16.39 mg·g−1). The adsorption kinetic curves of the adsorbents are fitted well with the pseudo first order adsorption kinetic equation. The optimal pH for P removal is 6-8. When the concentration of coexisting ions, such as Cl−, NO3−, SO42−, CO32−, in P solution is 1.0 g·L−1 respectively, the phosphate adsorption of HFO composite adsorbents decreases by 31.1%-53.0%. The adsorbed P on HFO composite adsorbents could be well desorbed with 5wt% NaOH solution.
In order to reduce the amount of HCl used in the hydrated ferrous oxide (HFO) composite adsorbents preparation process, which frequently caused serious equipment corrosion, safe and environmental problems, several adsorbents were prepared with various HCl concentrations. The effectiveness of P adsorption by the adsorbents were investigated at various perspectives, including adsorption kinetics, adsorption isotherms, effect of pH, co-existing ions and desorption methods. Experimental results demonstrate that phosphate adsorption capacity of HFO composite adsorbents doesn’t decrease significantly with the decreasing HCl concentration (from 2 mol·L−1 to 0.5 mol·L−1). The maximum P adsorption capacity of HFO composite adsorbent prepared at 0.5 mol·L−1 HCl is 29.67 mg·g−1, which is higher than the corresponding value of D201 resin (16.39 mg·g−1). The adsorption kinetic curves of the adsorbents are fitted well with the pseudo first order adsorption kinetic equation. The optimal pH for P removal is 6-8. When the concentration of coexisting ions, such as Cl−, NO3−, SO42−, CO32−, in P solution is 1.0 g·L−1 respectively, the phosphate adsorption of HFO composite adsorbents decreases by 31.1%-53.0%. The adsorbed P on HFO composite adsorbents could be well desorbed with 5wt% NaOH solution.
2021, 38(4): 1147-1154.
doi: 10.13801/j.cnki.fhclxb.20200812.001
Abstract:
The effects of the nano BN and ZnO on the thermal decomposition, combustion and mechanical properties of wood flour-polyvinyl chloride (WF-PVC) composites were investigated. The flame retarded WF-PVC composites with nano-BN and ZnO were prepared by hot pressing. Thermogravimetric analysis (TG) test results show that the addition of BN and ZnO reduces the initial thermal degradation temperature of the composites, while significantly increases the pyrolysis residues of the composites. When the mass ratio of BN to ZnO is 1∶2, the residues content of the composites increases by 21.7%. The cone calorimeter combustion test results show that the addition of nano-BN and ZnO significantly improves the flame retardant properties of the composites. Compared with the pure WF-PVC, the addition of BN and ZnO effectively decreases the heat release and smoke release during combustion of the composites, the total heat release and total smoke emission are decreased by 18.2% and 48.9%, respectively. The mechanical properties of the composites were tested by the universal mechanical testing machine. The results show that the addition of the flame retardants has some negative effects on the mechanical properties of the composites. However, the flame retardants were compounded in a certain proportion, which could effectively reduce the damage to the mechanical properties of the composites. The flexural strength of the composites is reduced by 29.5% when the ZnO is added alone, while the flexural strength of the composites is decreased by 9.9% when the mass ratio of BN to ZnO is 2∶1.
The effects of the nano BN and ZnO on the thermal decomposition, combustion and mechanical properties of wood flour-polyvinyl chloride (WF-PVC) composites were investigated. The flame retarded WF-PVC composites with nano-BN and ZnO were prepared by hot pressing. Thermogravimetric analysis (TG) test results show that the addition of BN and ZnO reduces the initial thermal degradation temperature of the composites, while significantly increases the pyrolysis residues of the composites. When the mass ratio of BN to ZnO is 1∶2, the residues content of the composites increases by 21.7%. The cone calorimeter combustion test results show that the addition of nano-BN and ZnO significantly improves the flame retardant properties of the composites. Compared with the pure WF-PVC, the addition of BN and ZnO effectively decreases the heat release and smoke release during combustion of the composites, the total heat release and total smoke emission are decreased by 18.2% and 48.9%, respectively. The mechanical properties of the composites were tested by the universal mechanical testing machine. The results show that the addition of the flame retardants has some negative effects on the mechanical properties of the composites. However, the flame retardants were compounded in a certain proportion, which could effectively reduce the damage to the mechanical properties of the composites. The flexural strength of the composites is reduced by 29.5% when the ZnO is added alone, while the flexural strength of the composites is decreased by 9.9% when the mass ratio of BN to ZnO is 2∶1.
2021, 38(4): 1155-1166.
doi: 10.13801/j.cnki.fhclxb.20200722.004
Abstract:
In order to solve the time-consuming problem of data acquisition of the whole wavefield, a compressed sensing algorithm was introduced to represent the wavefield sparsely. Due to the complex propagation characteristics of guided waves in composite materials, the application of compressed sensing in composite plates becomes difficult. Hence, by considering the anisotropic wavenumber characteristics of the guided waves propagating in the composite plate, a wavenumber library under different angles in the calculated frequency band was constructed for wavefield reconstruction. In the stage of damage analysis, a composite material damage scattering wavefield separation technology without reference signal technology was proposed to accurately remove the incident wavefield and improve the accuracy of damage location. Simulation and experimental results show that the proposed approach allows a reduction of the measurement locations required for accurate signal recovery to less than 90% of the original sampling grid and the single damage location error is less than 2/3 of the minimum wavelength. In addition, the double-damage experimental results show that the proposed method can effectively locate the double-damage, and related results can provide a theoretical and methodological basis for the practical application of composite damage detection.
In order to solve the time-consuming problem of data acquisition of the whole wavefield, a compressed sensing algorithm was introduced to represent the wavefield sparsely. Due to the complex propagation characteristics of guided waves in composite materials, the application of compressed sensing in composite plates becomes difficult. Hence, by considering the anisotropic wavenumber characteristics of the guided waves propagating in the composite plate, a wavenumber library under different angles in the calculated frequency band was constructed for wavefield reconstruction. In the stage of damage analysis, a composite material damage scattering wavefield separation technology without reference signal technology was proposed to accurately remove the incident wavefield and improve the accuracy of damage location. Simulation and experimental results show that the proposed approach allows a reduction of the measurement locations required for accurate signal recovery to less than 90% of the original sampling grid and the single damage location error is less than 2/3 of the minimum wavelength. In addition, the double-damage experimental results show that the proposed method can effectively locate the double-damage, and related results can provide a theoretical and methodological basis for the practical application of composite damage detection.
2021, 38(4): 1167-1176.
doi: 10.13801/j.cnki.fhclxb.20200720.002
Abstract:
To predict the process-induced residual stress/strain of 3D woven composite and propose the optimal cure cycle, a multiscale model of the process analysis has been developed. Based on the representative volume elements (RVE) at the fiber and yarn scale, the modulus development of yarns and 3D woven composite was obtained. A thermal-chemical-mechanical coupling analysis was conducted on the yarn scale with the consideration of chemical shrinkage effect of resin, and the evolution of the microscopic stress-strain was calculated. The fiber Bragg grating (FBG) sensors were embedded in the 3D woven preform through the 3D weaving technique, and the evolutions of temperature and strain were monitored. The accuracy of the finite element model was validated by the experimental result. Three sequential sampling methods based on space, error and result were adopted to establish the surrogate model of the process analysis of 3D woven composite. Based on the surrogate model, the optimization of process parameters of 3D woven composite forming process was carried out. The results show that the residual strain is reduced by 15.4% and the cure cycle is shortened by 10.6%.
To predict the process-induced residual stress/strain of 3D woven composite and propose the optimal cure cycle, a multiscale model of the process analysis has been developed. Based on the representative volume elements (RVE) at the fiber and yarn scale, the modulus development of yarns and 3D woven composite was obtained. A thermal-chemical-mechanical coupling analysis was conducted on the yarn scale with the consideration of chemical shrinkage effect of resin, and the evolution of the microscopic stress-strain was calculated. The fiber Bragg grating (FBG) sensors were embedded in the 3D woven preform through the 3D weaving technique, and the evolutions of temperature and strain were monitored. The accuracy of the finite element model was validated by the experimental result. Three sequential sampling methods based on space, error and result were adopted to establish the surrogate model of the process analysis of 3D woven composite. Based on the surrogate model, the optimization of process parameters of 3D woven composite forming process was carried out. The results show that the residual strain is reduced by 15.4% and the cure cycle is shortened by 10.6%.
2021, 38(4): 1177-1191.
doi: 10.13801/j.cnki.fhclxb.20201111.001
Abstract:
The damage of composite materials poses a threat to the reliability and safety of the structure, and has attracted widespread attention from domestic and foreign experts and scholars in recent years. This study embeded the shape memory alloy (SMA) in the composite material specimen, and discussed the relationship between the SMA resistance change and the composite material strain, established theoretical models of composite damage monitoring under different monitoring conditions. Based on this model, the damage monitoring behavior of SMA materials in different initial states was discussed. The research results show that the damage of the composite material has a linear relationship with the resistance change of the SMA. The temperature load has little influence on the damage monitoring when the SMA does not undergo a phase change, and has a greater influence on the damage monitoring when the SMA undergoes a phase change. The research can provide theoretical guidance for the further engineering application of SMA-based composite damage monitoring theory.
The damage of composite materials poses a threat to the reliability and safety of the structure, and has attracted widespread attention from domestic and foreign experts and scholars in recent years. This study embeded the shape memory alloy (SMA) in the composite material specimen, and discussed the relationship between the SMA resistance change and the composite material strain, established theoretical models of composite damage monitoring under different monitoring conditions. Based on this model, the damage monitoring behavior of SMA materials in different initial states was discussed. The research results show that the damage of the composite material has a linear relationship with the resistance change of the SMA. The temperature load has little influence on the damage monitoring when the SMA does not undergo a phase change, and has a greater influence on the damage monitoring when the SMA undergoes a phase change. The research can provide theoretical guidance for the further engineering application of SMA-based composite damage monitoring theory.
2021, 38(4): 1192-1199.
doi: 10.13801/j.cnki.fhclxb.20201110.001
Abstract:
The graphite flakes reinforced Al matrix composites (50vol%Gf/6061Al) were fabricated by powder metallurgy technique. The Gf had a well bonding with Al matrix without cracks and pores. The composites were exposed to a thermal cycling test in the temperature range of −50-120℃. The microstructure and properties of 50vol%Gf/6061Al were examined when the composites were tested by 10, 50, 100 and 200 thermal cycles. The density of the composites is almost unchanged under different thermal cycles. With the number of the thermal cycle increasing, the Gf in the composites are cracked due to the stress from the difference of the thermal expansion coefficient between Gf and Al matrix. The strength and thermal conductivity of the composite are decreased with the number of the thermal cycle increasing. After 100 thermal cycles, the bending strength decreases by 27.4% and thermal conductivity decreases by 11.5% compared to that of the sample without thermal cycles. The broken Gf and the cracked interface between Gf and Al matrix could release the thermal stress, therefore, the cracking of the Gf would be retarded. The microstructure and properties of the composites are not serious changed. After 200 thermal cycles, the bending strength decreases by 32% and TC decreases by 13.1% compared to that of the sample without thermal cycles.
The graphite flakes reinforced Al matrix composites (50vol%Gf/6061Al) were fabricated by powder metallurgy technique. The Gf had a well bonding with Al matrix without cracks and pores. The composites were exposed to a thermal cycling test in the temperature range of −50-120℃. The microstructure and properties of 50vol%Gf/6061Al were examined when the composites were tested by 10, 50, 100 and 200 thermal cycles. The density of the composites is almost unchanged under different thermal cycles. With the number of the thermal cycle increasing, the Gf in the composites are cracked due to the stress from the difference of the thermal expansion coefficient between Gf and Al matrix. The strength and thermal conductivity of the composite are decreased with the number of the thermal cycle increasing. After 100 thermal cycles, the bending strength decreases by 27.4% and thermal conductivity decreases by 11.5% compared to that of the sample without thermal cycles. The broken Gf and the cracked interface between Gf and Al matrix could release the thermal stress, therefore, the cracking of the Gf would be retarded. The microstructure and properties of the composites are not serious changed. After 200 thermal cycles, the bending strength decreases by 32% and TC decreases by 13.1% compared to that of the sample without thermal cycles.
2021, 38(4): 1200-1209.
doi: 10.13801/j.cnki.fhclxb.20201011.002
Abstract:
Using trichloromethylsilane (MTS) and H2 as precursors, the deposition kinetics of silicon carbide (SiC) was studied by chemical vapor deposition (CVD) process at 900-1 050℃, H2/MTS mole ratio of 4-20 and residence time of 0.4-1 s. The results show that the variation of SiC deposition rate with process parameters in different reactors is obviously different. The average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 increases with the increase of temperature, while the average deposition rate of SiC in the reactor with length diameter ratio of 7∶2 first increases and then decreases with the increase of temperature. Moreover, the deposition of SiC along the reactor with length diameter ratio of 7∶6 has the characteristics of multiple steady states. The variation of SiC deposition rate at different H2/MTS mole ratios is basically consistent in the two reactors. Although multiple preferential deposition positions along the SiC path appear in the reactor with length diameter ratio of 7∶6, the inhibition effect of H2 on SiC deposition is greater than that caused by reactor size effect. The results show that the average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 decreases with the increase of residence time, but the deposition rate along the path does not decrease monotonically due to the effect of reactor size; both the average deposition rate and the deposition rate along the path of the reactor with length diameter ratio of 7∶2 decrease with the increase of residence time and then tend to be stable. The flow field and temperature field of two kinds of length diameter ratio reactors were simulated by COMSOL software. It is found that the reactor with length diameter ratio of 7∶6 produces obvious radial velocity difference, and the axial and radial temperature difference are large, while the flow field and temperature field of deposition reactor with length diameter ratio of 7∶2 are more uniform. The actual process parameters and theory caused by the size effect of the reactor were analyzed. The deviation of process parameters is the reason for the difference of SiC deposition kinetics in different length diameter ratio reactors.
Using trichloromethylsilane (MTS) and H2 as precursors, the deposition kinetics of silicon carbide (SiC) was studied by chemical vapor deposition (CVD) process at 900-1 050℃, H2/MTS mole ratio of 4-20 and residence time of 0.4-1 s. The results show that the variation of SiC deposition rate with process parameters in different reactors is obviously different. The average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 increases with the increase of temperature, while the average deposition rate of SiC in the reactor with length diameter ratio of 7∶2 first increases and then decreases with the increase of temperature. Moreover, the deposition of SiC along the reactor with length diameter ratio of 7∶6 has the characteristics of multiple steady states. The variation of SiC deposition rate at different H2/MTS mole ratios is basically consistent in the two reactors. Although multiple preferential deposition positions along the SiC path appear in the reactor with length diameter ratio of 7∶6, the inhibition effect of H2 on SiC deposition is greater than that caused by reactor size effect. The results show that the average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 decreases with the increase of residence time, but the deposition rate along the path does not decrease monotonically due to the effect of reactor size; both the average deposition rate and the deposition rate along the path of the reactor with length diameter ratio of 7∶2 decrease with the increase of residence time and then tend to be stable. The flow field and temperature field of two kinds of length diameter ratio reactors were simulated by COMSOL software. It is found that the reactor with length diameter ratio of 7∶6 produces obvious radial velocity difference, and the axial and radial temperature difference are large, while the flow field and temperature field of deposition reactor with length diameter ratio of 7∶2 are more uniform. The actual process parameters and theory caused by the size effect of the reactor were analyzed. The deviation of process parameters is the reason for the difference of SiC deposition kinetics in different length diameter ratio reactors.
