2016 Vol. 33, No. 8
2016, 33(8): 1599-1607.
doi: 10.13801/j.cnki.fhclxb.20151013.005
Abstract:
In order to improve the flame retardant properties of ramie fabrics used as the reinforcing material in composites, amino-functionalized multiwall carbon nanotube (MWCNT)-ammonium polyphosphate (APP) and polyethylenimine (PEI)-APP intumescent flame retardant multilayer coatings were constructed on the surfaces of ramie fabric via layer-by-layer assembly method firstly. Then, the modified ramie fabrics were composed with benzoxazine resin to prepare ramie fabric/benzoxazine resin laminates, and the thermal degradation behaviour, flame retardant properties and mechanical properties of laminates were investigated. The results show that compared to the pristine ramie fabric/benzoxazine resin laminate, the peak values of heat release for the laminates containing MWCNT-APP and PEI-APP intumescent flame retardant multilayer coatings decrease from 106.6 W·g-1 to 53.4 W·g-1 and 53.0 W·g-1, the total heat release decrease from 12.3 kJ·g-1 to 7.6 kJ·g-1 and 9.0 kJ·g-1, the limiting oxygen indexes increase from 23.5 to 27.2 and 27.0, the UL94 level increase from no rating to V-0 and V-1 levels, the flexural strengths increase from 81 MPa to 122 MPa and 143 MPa, the flexural elongations at break increase from 1.2% to 1.4% and 1.7%, and the tensile properties also show improvements to a certain degree. The conclusions obtained show that using MWCNT-APP and PEI-APP intumescent flame retardant multilayer coatings can not only improve the flame retardant properties of laminates, but also improve the mechanical properties at the same time.
In order to improve the flame retardant properties of ramie fabrics used as the reinforcing material in composites, amino-functionalized multiwall carbon nanotube (MWCNT)-ammonium polyphosphate (APP) and polyethylenimine (PEI)-APP intumescent flame retardant multilayer coatings were constructed on the surfaces of ramie fabric via layer-by-layer assembly method firstly. Then, the modified ramie fabrics were composed with benzoxazine resin to prepare ramie fabric/benzoxazine resin laminates, and the thermal degradation behaviour, flame retardant properties and mechanical properties of laminates were investigated. The results show that compared to the pristine ramie fabric/benzoxazine resin laminate, the peak values of heat release for the laminates containing MWCNT-APP and PEI-APP intumescent flame retardant multilayer coatings decrease from 106.6 W·g-1 to 53.4 W·g-1 and 53.0 W·g-1, the total heat release decrease from 12.3 kJ·g-1 to 7.6 kJ·g-1 and 9.0 kJ·g-1, the limiting oxygen indexes increase from 23.5 to 27.2 and 27.0, the UL94 level increase from no rating to V-0 and V-1 levels, the flexural strengths increase from 81 MPa to 122 MPa and 143 MPa, the flexural elongations at break increase from 1.2% to 1.4% and 1.7%, and the tensile properties also show improvements to a certain degree. The conclusions obtained show that using MWCNT-APP and PEI-APP intumescent flame retardant multilayer coatings can not only improve the flame retardant properties of laminates, but also improve the mechanical properties at the same time.
2016, 33(8): 1608-1614.
doi: 10.13801/j.cnki.fhclxb.20151014.004
Abstract:
In order to obtain poly(lactic acid) (PLA) matrix biodegradable blends whose stiffness is balanced with toughness, PLA/poly(butylenes adipate-co-terephthalate) (PBAT)/poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fully biodegradable blends with different mass ratios were prepared by melting co-extrusion method. The morphology structures, thermal characteristics, rheological behavior and mechanical properties of PLA/PBAT/PHBV blends were investigated with SEM, TG, DSC, capillary rheometer and universal material testing machine. The results show that the initial decomposition temperature of PLA/PBAT/PHBV blends increases by 45 ℃ compared with pure PHBV, and the thermal stability of PLA/PBAT/PHBV blends is enhanced. Glass transition temperatures of each component in the blend system change little compared with the unitary system, which indicates that the PLA/PBAT/PHBV blend system is a complete incompatible system. At the same time, the cold crystallization of PLA is confined by the incorporation of PBAT and PHBV. The blend morphology of PLA/PBAT/PHBV blend system presents as a "sea-island" distribution, PBAT and PHBV distribute in PLA matrix evenly, and the interfaces between different phases are clear. When the content of PBAT increasing, the rheological of PLA/PBAT/PHBV blends melt is improved, and the effect of temperature on viscosity increases. The tensile strain of PLA/PBAT/PHBV blends with PLA/PBAT/PHBV mass ratio of 70/20/10 improves to 2.6 times of that of pure PLA, the toughness has been improved, and in the meanwhile, 60% tensile stress of pure PLA can be maintain. The conclusions obtained show that the comprehensive mechanical properties of PLA/PBAT/PHBV blends with PLA/PBAT/PHBV mass ratio of 70/20/10 is better than that of pure PLA.
In order to obtain poly(lactic acid) (PLA) matrix biodegradable blends whose stiffness is balanced with toughness, PLA/poly(butylenes adipate-co-terephthalate) (PBAT)/poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fully biodegradable blends with different mass ratios were prepared by melting co-extrusion method. The morphology structures, thermal characteristics, rheological behavior and mechanical properties of PLA/PBAT/PHBV blends were investigated with SEM, TG, DSC, capillary rheometer and universal material testing machine. The results show that the initial decomposition temperature of PLA/PBAT/PHBV blends increases by 45 ℃ compared with pure PHBV, and the thermal stability of PLA/PBAT/PHBV blends is enhanced. Glass transition temperatures of each component in the blend system change little compared with the unitary system, which indicates that the PLA/PBAT/PHBV blend system is a complete incompatible system. At the same time, the cold crystallization of PLA is confined by the incorporation of PBAT and PHBV. The blend morphology of PLA/PBAT/PHBV blend system presents as a "sea-island" distribution, PBAT and PHBV distribute in PLA matrix evenly, and the interfaces between different phases are clear. When the content of PBAT increasing, the rheological of PLA/PBAT/PHBV blends melt is improved, and the effect of temperature on viscosity increases. The tensile strain of PLA/PBAT/PHBV blends with PLA/PBAT/PHBV mass ratio of 70/20/10 improves to 2.6 times of that of pure PLA, the toughness has been improved, and in the meanwhile, 60% tensile stress of pure PLA can be maintain. The conclusions obtained show that the comprehensive mechanical properties of PLA/PBAT/PHBV blends with PLA/PBAT/PHBV mass ratio of 70/20/10 is better than that of pure PLA.
2016, 33(8): 1615-1620.
doi: 10.13801/j.cnki.fhclxb.20151020.004
Abstract:
In order to fully understand the curing properties of composites, on the basis of the numerical simulation and analysis for the curing induced deformation of carbon fiber reinforced resin matrix composites, self-designed fiber Bragg grating (FBG) sensors were embedded in the composite to real time on-line monitor the temperature and strain evolutions during the curing process of composite. The stacking sequence of prepreg was [011/9011]. The FBG temperature and strain sensors were embedded in the typical positions of the laminate along 0° and 45° directions, respectively. The composite laminate was cured and molded by hot molded pressing method, and two continuous cooling stages were conducted on the laminate after molding. The changes for central wavelength of FBG sensors during the curing process are recorded in real-time. The results show that the absolute value of the composite compression strain at the first cooling early stage is obviously less than the absolute value of the compression strain at the second cooling early stage under the same temperature conditions, which indicates that the composite still proceeds the "post curing" reaction which can be detected by FBG sensors at the first cooling stage. Besides, the deformation monitoring data of FBG sensors for laminates match well with the finite element simulation results. Therefore, using the method of embedded FBG sensors can monitor the curing process of composites real-time, which provides a reliable and effective method for analyzing the curing characteristics of the composites more comprehensively.
In order to fully understand the curing properties of composites, on the basis of the numerical simulation and analysis for the curing induced deformation of carbon fiber reinforced resin matrix composites, self-designed fiber Bragg grating (FBG) sensors were embedded in the composite to real time on-line monitor the temperature and strain evolutions during the curing process of composite. The stacking sequence of prepreg was [011/9011]. The FBG temperature and strain sensors were embedded in the typical positions of the laminate along 0° and 45° directions, respectively. The composite laminate was cured and molded by hot molded pressing method, and two continuous cooling stages were conducted on the laminate after molding. The changes for central wavelength of FBG sensors during the curing process are recorded in real-time. The results show that the absolute value of the composite compression strain at the first cooling early stage is obviously less than the absolute value of the compression strain at the second cooling early stage under the same temperature conditions, which indicates that the composite still proceeds the "post curing" reaction which can be detected by FBG sensors at the first cooling stage. Besides, the deformation monitoring data of FBG sensors for laminates match well with the finite element simulation results. Therefore, using the method of embedded FBG sensors can monitor the curing process of composites real-time, which provides a reliable and effective method for analyzing the curing characteristics of the composites more comprehensively.
2016, 33(8): 1621-1629.
doi: 10.13801/j.cnki.fhclxb.20151014.005
Abstract:
In order to compare and analyze the degradation effects of different supercritical fluids on carbon fiber/epoxy (CF/EP) composites, CF/EP composites were degraded by supercritical fluids in batch reactor firstly, the degradation capabilities of supercritical CO2 and supercritical alcohols at different reaction temperatures for CF/EP composites were analyzed, and the select method of supercritical fluid for the degradation of CF/EP composites was proposed. Then, the mechanical properties and microstructures of carbon fibers recycled using supercritical n-butanol and supercritical n-propanol were analyzed by testing measures such as single filament tensile tests, SEM and atomic force microscope etc. The results show that the degradation capability of supercritical CO2 for CF/EP composites is weaker, and the degradation capability has significant improvement when using n-propanol as the entrainer. Supercritical n-butanol has the strongest degradation capability for CF/EP composites, followed by supercritical n-propanol, and the degradation capability of supercritical methanol is the weakest. The smaller the dielectric constant of selected reaction medium is, the greater the dipole moment is, the closer the solubility parameters with the epoxy matrix is, the easier for the degradation of CF/EP composites under supercritical conditions. Carbon fibers with excellent performances could be obtained by degradation of CF/EP composites using supercritical fluids. Comparing with the original fibers, the retention rates for single filament tensile strength of supercritical n-butanol and supercritical n-propanol recycled carbon fibers are above 98%, and the Weibull modulus are close.
In order to compare and analyze the degradation effects of different supercritical fluids on carbon fiber/epoxy (CF/EP) composites, CF/EP composites were degraded by supercritical fluids in batch reactor firstly, the degradation capabilities of supercritical CO2 and supercritical alcohols at different reaction temperatures for CF/EP composites were analyzed, and the select method of supercritical fluid for the degradation of CF/EP composites was proposed. Then, the mechanical properties and microstructures of carbon fibers recycled using supercritical n-butanol and supercritical n-propanol were analyzed by testing measures such as single filament tensile tests, SEM and atomic force microscope etc. The results show that the degradation capability of supercritical CO2 for CF/EP composites is weaker, and the degradation capability has significant improvement when using n-propanol as the entrainer. Supercritical n-butanol has the strongest degradation capability for CF/EP composites, followed by supercritical n-propanol, and the degradation capability of supercritical methanol is the weakest. The smaller the dielectric constant of selected reaction medium is, the greater the dipole moment is, the closer the solubility parameters with the epoxy matrix is, the easier for the degradation of CF/EP composites under supercritical conditions. Carbon fibers with excellent performances could be obtained by degradation of CF/EP composites using supercritical fluids. Comparing with the original fibers, the retention rates for single filament tensile strength of supercritical n-butanol and supercritical n-propanol recycled carbon fibers are above 98%, and the Weibull modulus are close.
2016, 33(8): 1630-1637.
doi: 10.13801/j.cnki.fhclxb.20151022.001
Abstract:
Hollow glass microsphere(HGM)/epoxy syntactic foams were prepared with epoxy filled with HGM, The density of the syntactic foams was maintained 0.56-0.91 g/cm3. Viscosity, mechanical properties, dynamic mechanical properties and thermal insulation properties of the syntactic foams were investigated with respect to HGM content. The results show that surface coupling modification improves surface lipophilicity of HGM, thus increases the compatibility and interfacial property between HGM and resin matrix, which is beneficial to enhancing the property of syntactic foams. The viscosity of system increases with HGM content increasing and decreases with temperature increasing. The compressive, flexural and tensile strength decrease with increasing HGM content to some extent, the specific strength changes little, making a high degree of weight saving. With the incorporation of HGM, the glass transition temperature of HGM/epoxy syntactic foams shifts to low temperature and the storage modulus first decreases then increases, thermal conductivity decreases from 0.203 W/(m·K) of neat epoxy to 0.126 W/(m·K) of syntactic foams containing 40wt% of HGM, there is a significant improvement on damping and thermal insulation properties of HGM/epoxy syntactic foams.
Hollow glass microsphere(HGM)/epoxy syntactic foams were prepared with epoxy filled with HGM, The density of the syntactic foams was maintained 0.56-0.91 g/cm3. Viscosity, mechanical properties, dynamic mechanical properties and thermal insulation properties of the syntactic foams were investigated with respect to HGM content. The results show that surface coupling modification improves surface lipophilicity of HGM, thus increases the compatibility and interfacial property between HGM and resin matrix, which is beneficial to enhancing the property of syntactic foams. The viscosity of system increases with HGM content increasing and decreases with temperature increasing. The compressive, flexural and tensile strength decrease with increasing HGM content to some extent, the specific strength changes little, making a high degree of weight saving. With the incorporation of HGM, the glass transition temperature of HGM/epoxy syntactic foams shifts to low temperature and the storage modulus first decreases then increases, thermal conductivity decreases from 0.203 W/(m·K) of neat epoxy to 0.126 W/(m·K) of syntactic foams containing 40wt% of HGM, there is a significant improvement on damping and thermal insulation properties of HGM/epoxy syntactic foams.
2016, 33(8): 1638-1644.
doi: 10.13801/j.cnki.fhclxb.20151014.006
Abstract:
Maleic anhydride (MAH) was used to corrode aramid fibers (AFs) in order to improve the interfacial compatibility between AFs and polyamide 6 (PA6) and increase the mechanical properties of AFs/PA6 composites. PA6 was mixed with AFs treated with different time gradients uniformly and the standard samples of AFs/PA6 composites were injection molded. FE-SEM, XPS, XRD and DSC were used to study the surface morphologies and element contents of AFs and the impact fracture surface morphologies, crystal form, grain and crystallinities of AFs/PA6 composites. The results show that surface roughness and surface oxygen content of AFs reach the maximum after corrosion for 3 h. The introduction of corroded AFs is beneficial for PA6 to refine grains and form α crystal. The inner of AFs/PA6 composite samples tend to form α crystal easily and the crystallinity has been improved compared with PA6. AFs/PA6 composites have higher tensile strength and bending strength after the addition of surface treated AFs, and mechanical properties of AFs/PA6 composites achieve maximum value when AFs are corroded for 3 h.
Maleic anhydride (MAH) was used to corrode aramid fibers (AFs) in order to improve the interfacial compatibility between AFs and polyamide 6 (PA6) and increase the mechanical properties of AFs/PA6 composites. PA6 was mixed with AFs treated with different time gradients uniformly and the standard samples of AFs/PA6 composites were injection molded. FE-SEM, XPS, XRD and DSC were used to study the surface morphologies and element contents of AFs and the impact fracture surface morphologies, crystal form, grain and crystallinities of AFs/PA6 composites. The results show that surface roughness and surface oxygen content of AFs reach the maximum after corrosion for 3 h. The introduction of corroded AFs is beneficial for PA6 to refine grains and form α crystal. The inner of AFs/PA6 composite samples tend to form α crystal easily and the crystallinity has been improved compared with PA6. AFs/PA6 composites have higher tensile strength and bending strength after the addition of surface treated AFs, and mechanical properties of AFs/PA6 composites achieve maximum value when AFs are corroded for 3 h.
2016, 33(8): 1645-1653.
doi: 10.13801/j.cnki.fhclxb.20151027.001
Abstract:
In order to fabricate an inducible bone repair scaffold materials, Icariin (Ica) were modified by amino and then got Ica-NH2, Ica-NH2 was characterized by FTIR, XRD and TGA. Ica-NH2 covalent binding with carboxymethyl chitosan (CS) as the inducing factor addition method, poly hydroxybutyrate-co-hydroxyvalerate (PHBV) and CS were used as basic materials, then two-phase mixed rapid freezing/freeze-drying technology was used to build the Ica-NH2-CS/PHBV bone tissue engineering scaffolds. And then the scaffold materials were evaluated by SEM, invitro drug release, mechanical properties, cell compatibility and proliferation. The results show that: there were two moderate intensity, sharp N—H stretching vibration peaks at 3 371 and 3 328 cm-1 in the FTIR spectra of aminated Ica, one N—H waving vibration peaks appears at 1 689 cm-1, XRD pattern shows the diffractions are enhanced and move to the left as a whole, these results indicate that Ica is successfully amino-modified. The scaffold materials possess network-and bead-like mircostructures, which are uniformly distrubuted wtih microporous of 3-10 μm. Ica-NH2-CS/PHBV scaffold has good invitro drug release effect. Mechanical strength tests show its mechanical strength is between dense bone and cancellous bone, composite cells closely adhere on the scaffold after 7 d cultivation and proliferate well, and the proliferation rate of cells attached on Ica-NH2-CS/PHBV scaffold materials is significantly higher than that on the CS/PHBV. This research indicates that Ica-NH2-CS/PHBV scaffold materials could be used as good type of inducible bone repair materials.
In order to fabricate an inducible bone repair scaffold materials, Icariin (Ica) were modified by amino and then got Ica-NH2, Ica-NH2 was characterized by FTIR, XRD and TGA. Ica-NH2 covalent binding with carboxymethyl chitosan (CS) as the inducing factor addition method, poly hydroxybutyrate-co-hydroxyvalerate (PHBV) and CS were used as basic materials, then two-phase mixed rapid freezing/freeze-drying technology was used to build the Ica-NH2-CS/PHBV bone tissue engineering scaffolds. And then the scaffold materials were evaluated by SEM, invitro drug release, mechanical properties, cell compatibility and proliferation. The results show that: there were two moderate intensity, sharp N—H stretching vibration peaks at 3 371 and 3 328 cm-1 in the FTIR spectra of aminated Ica, one N—H waving vibration peaks appears at 1 689 cm-1, XRD pattern shows the diffractions are enhanced and move to the left as a whole, these results indicate that Ica is successfully amino-modified. The scaffold materials possess network-and bead-like mircostructures, which are uniformly distrubuted wtih microporous of 3-10 μm. Ica-NH2-CS/PHBV scaffold has good invitro drug release effect. Mechanical strength tests show its mechanical strength is between dense bone and cancellous bone, composite cells closely adhere on the scaffold after 7 d cultivation and proliferate well, and the proliferation rate of cells attached on Ica-NH2-CS/PHBV scaffold materials is significantly higher than that on the CS/PHBV. This research indicates that Ica-NH2-CS/PHBV scaffold materials could be used as good type of inducible bone repair materials.
2016, 33(8): 1654-1662.
doi: 10.13801/j.cnki.fhclxb.20160111.001
Abstract:
Graphene/polysulfone amide (PSA) composite films with different mass fractions of graphene were prepared by spin-coating technique. The chemical composition, macromolecular structure, thermal property, electrical properties, mechanical properties and ultraviolet resistance were characterized and analyzed by means of optical microscopy, Fourier transform infrared spectrometer, surface resistance testing, thermal gravimetric analysis and ultraviolet spectrum. The results show that small amount of graphene can be evenly dispersed in PSA substrate, and the introducing of graphene does not change the chemical structure of PSA. The crystallinity of the composite membranes can be improved because the graphene 2D nano material can act as a nucleation agent. The mechanical properties and thermal properties of composite membranes can be improved correspondingly. When the mass fraction of graphene is 0.1%, the surface specific resistance of graphene/PSA composite membranes decreases to 1.40×106 Ω quickly, while that of pure PSA membrane is 3.10×1012 Ω. As the mass fraction of graphene increases, the electrical properties of graphene/PSA composite membranes improves correspondingly. Graphene plays an important role in strengthening the absorption and scattering of ultraviolet light and improving ultraviolet resistance.
Graphene/polysulfone amide (PSA) composite films with different mass fractions of graphene were prepared by spin-coating technique. The chemical composition, macromolecular structure, thermal property, electrical properties, mechanical properties and ultraviolet resistance were characterized and analyzed by means of optical microscopy, Fourier transform infrared spectrometer, surface resistance testing, thermal gravimetric analysis and ultraviolet spectrum. The results show that small amount of graphene can be evenly dispersed in PSA substrate, and the introducing of graphene does not change the chemical structure of PSA. The crystallinity of the composite membranes can be improved because the graphene 2D nano material can act as a nucleation agent. The mechanical properties and thermal properties of composite membranes can be improved correspondingly. When the mass fraction of graphene is 0.1%, the surface specific resistance of graphene/PSA composite membranes decreases to 1.40×106 Ω quickly, while that of pure PSA membrane is 3.10×1012 Ω. As the mass fraction of graphene increases, the electrical properties of graphene/PSA composite membranes improves correspondingly. Graphene plays an important role in strengthening the absorption and scattering of ultraviolet light and improving ultraviolet resistance.
2016, 33(8): 1663-1670.
doi: 10.13801/j.cnki.fhclxb.20151124.002
Abstract:
With branched agent as the initiator of hyperbranched polyamide 6 (PA6), with organic modifier modified organic montmorillonite (O-MMT) which has the terminal carboxyl group, O-MMT/hyperbranched PA6 composites were prepared via in situ ring-opening graft polymerization. The grafting condition of hyperbranched PA6 and O-MMT, dispersing morphology of O-MMT in matrix were characterized by FTIR and TEM, and the effects of O-MMT on crystallization properties, melt flow properties and mechanical properties of hyperbranched PA6 were studied. Results show that O-MMT is exfoliated and intercalated dispersing in hyperbranched PA6 matrix, and chemically bonds with PA6 molecular chains to form crosslinked network structure, which makes the melt flow index of O-MMT/hyperbranched PA6 composites decrease sharply compared with hyperbranched PA6. In addition, O-MMT can make the α-crystal of hyperbranched PA6 disappear, and make crystallization degree of hyperbranched PA6 with only γ-crystal decrease. However, with the increase of O-MMT content, the strength of O-MMT/hyperbranched PA6 composites increase gradually, the tensile strength increase from 38.4 MPa to 60.8 MPa, the toughness of composites also has been greatly improved, the elongation at break increases from 2.1% to 70.1%, the un-notched impact strength increases from 20.3 kJ/m2 increase to 291.8 kJ/m2 sharply.
With branched agent as the initiator of hyperbranched polyamide 6 (PA6), with organic modifier modified organic montmorillonite (O-MMT) which has the terminal carboxyl group, O-MMT/hyperbranched PA6 composites were prepared via in situ ring-opening graft polymerization. The grafting condition of hyperbranched PA6 and O-MMT, dispersing morphology of O-MMT in matrix were characterized by FTIR and TEM, and the effects of O-MMT on crystallization properties, melt flow properties and mechanical properties of hyperbranched PA6 were studied. Results show that O-MMT is exfoliated and intercalated dispersing in hyperbranched PA6 matrix, and chemically bonds with PA6 molecular chains to form crosslinked network structure, which makes the melt flow index of O-MMT/hyperbranched PA6 composites decrease sharply compared with hyperbranched PA6. In addition, O-MMT can make the α-crystal of hyperbranched PA6 disappear, and make crystallization degree of hyperbranched PA6 with only γ-crystal decrease. However, with the increase of O-MMT content, the strength of O-MMT/hyperbranched PA6 composites increase gradually, the tensile strength increase from 38.4 MPa to 60.8 MPa, the toughness of composites also has been greatly improved, the elongation at break increases from 2.1% to 70.1%, the un-notched impact strength increases from 20.3 kJ/m2 increase to 291.8 kJ/m2 sharply.
2016, 33(8): 1671-1676.
doi: 10.13801/j.cnki.fhclxb.20151027.002
Abstract:
Impedance gradient materials have played an important role in the medical wearable devices. For realizing the matching character between different materials, the research about low-dielectric materials with impedance gradient is particularly important. By means of the electrospinning, low-dielectric barium titanate (BaTiO3)/polyvinylidene-fluoride (PVDF) composite fibrous mat with impedance gradient was designed and prepared. The results show that the BaTiO3 nano-particles can distribute in the fiber uniformly. By adjusting the mass fraction of nano-particles, the dielectric constant of BaTiO3/PVDF composite fibrous mat can arrange from 1 to 7, and it is also insensible to the different frequencies of electric field. BaTiO3/PVDF composite fibrous mat possesses good mechanical property and can meet the requirements of the wearable device materials.
Impedance gradient materials have played an important role in the medical wearable devices. For realizing the matching character between different materials, the research about low-dielectric materials with impedance gradient is particularly important. By means of the electrospinning, low-dielectric barium titanate (BaTiO3)/polyvinylidene-fluoride (PVDF) composite fibrous mat with impedance gradient was designed and prepared. The results show that the BaTiO3 nano-particles can distribute in the fiber uniformly. By adjusting the mass fraction of nano-particles, the dielectric constant of BaTiO3/PVDF composite fibrous mat can arrange from 1 to 7, and it is also insensible to the different frequencies of electric field. BaTiO3/PVDF composite fibrous mat possesses good mechanical property and can meet the requirements of the wearable device materials.
2016, 33(8): 1677-1686.
doi: 10.13801/j.cnki.fhclxb.20151020.005
Abstract:
In order to determine the effects of compressive preload on impact damage performance of composite laminates, low-velocity impact and quasi-static indentation tests were carried out on carbon fiber/bismaleimide resin CCF300/5428 laminates under different compressive preloads firstly. Then, delamination area and residual strength of the laminates were obtained by thermally deplying and compression after impact tests respectively. The results show that compressive preload will reduce the contact stiffness and bending stiffness of the laminates significantly, which causes the increases in dent depth and crack length of back matrix for the laminates under the same impact energy. For the quasi-static indentation process and impact processes under the same impact energy, both of delamination initiation load and peak load decrease with the increase of the compressive preload. Under the same impact energy, total delamination area in the laminates and absorbed impact energy ratio increase continually with the increase of compressive preload, leads to the continuous reduction in residual compressive strength. In conclusion, compressive preload will reduce the impact damage resistance of composite laminates and is unfavorable to the damage tolerance performance, which means that it is necessary to take the effects of compressive preload on impact damage performance into consideration during the test verification process of the structures under compressive load.
In order to determine the effects of compressive preload on impact damage performance of composite laminates, low-velocity impact and quasi-static indentation tests were carried out on carbon fiber/bismaleimide resin CCF300/5428 laminates under different compressive preloads firstly. Then, delamination area and residual strength of the laminates were obtained by thermally deplying and compression after impact tests respectively. The results show that compressive preload will reduce the contact stiffness and bending stiffness of the laminates significantly, which causes the increases in dent depth and crack length of back matrix for the laminates under the same impact energy. For the quasi-static indentation process and impact processes under the same impact energy, both of delamination initiation load and peak load decrease with the increase of the compressive preload. Under the same impact energy, total delamination area in the laminates and absorbed impact energy ratio increase continually with the increase of compressive preload, leads to the continuous reduction in residual compressive strength. In conclusion, compressive preload will reduce the impact damage resistance of composite laminates and is unfavorable to the damage tolerance performance, which means that it is necessary to take the effects of compressive preload on impact damage performance into consideration during the test verification process of the structures under compressive load.
2016, 33(8): 1687-1693.
doi: 10.13801/j.cnki.fhclxb.20151120.002
Abstract:
In order to investigate the delamination phenomenon of composite laminates after moisture absorption, finite element model for the delamination of composite laminates after moisture absorption caused by rapid heating was established, and ABAQUS finite element software was second developed, the delamination growth under the local high pressure loading effect induced by the vaporized water after moisture adsorption when rapid heating as well as the load applied process were simulated through UAMP subroutine. Then, the delamination phenomenon of saturated moisture absorbed T650-35/HFPE-II-52 carbon fiber polyimide composite laminates when rapidly heating to 310 ℃ was predicted by the model, and the numerical simulation and reference experimental results were contrasted. Finally, the influences for the moisture content of resin and the aggregate volume of resin in resin rich area on the delamination damage area were analyzed by the model. The results show that the finite element model established is valid. After rapid heating, the delamination damage area increases with the moisture content of resin increases. When the aggregate volume of resin in resin rich area is relatively small, the influence of it on delamination damage area of laminates after rapid heating is relatively small, while when the aggregate volume of resin in resin rich area increasing to a certain value, the delamination damage area increases significantly with the aggregate volume of resin in resin rich area increasing. The conclusions obtained show that the finite element model established by UAMP subroutine of ABAQUS can analyze the delamination phenomenon of moisture absorbed composite laminates due to rapid heating effectively.
In order to investigate the delamination phenomenon of composite laminates after moisture absorption, finite element model for the delamination of composite laminates after moisture absorption caused by rapid heating was established, and ABAQUS finite element software was second developed, the delamination growth under the local high pressure loading effect induced by the vaporized water after moisture adsorption when rapid heating as well as the load applied process were simulated through UAMP subroutine. Then, the delamination phenomenon of saturated moisture absorbed T650-35/HFPE-II-52 carbon fiber polyimide composite laminates when rapidly heating to 310 ℃ was predicted by the model, and the numerical simulation and reference experimental results were contrasted. Finally, the influences for the moisture content of resin and the aggregate volume of resin in resin rich area on the delamination damage area were analyzed by the model. The results show that the finite element model established is valid. After rapid heating, the delamination damage area increases with the moisture content of resin increases. When the aggregate volume of resin in resin rich area is relatively small, the influence of it on delamination damage area of laminates after rapid heating is relatively small, while when the aggregate volume of resin in resin rich area increasing to a certain value, the delamination damage area increases significantly with the aggregate volume of resin in resin rich area increasing. The conclusions obtained show that the finite element model established by UAMP subroutine of ABAQUS can analyze the delamination phenomenon of moisture absorbed composite laminates due to rapid heating effectively.
2016, 33(8): 1694-1701.
doi: 10.13801/j.cnki.fhclxb.20151029.001
Abstract:
In response to composite tube with arbitrary lamination and thickness, an approach of the equivalent bending stiffness was presented. The deformation theory with realistic deformation of composite tube beam was used in this analysis. Transverse shear deformation, non-uniform torsion effects, the primary and the secondary warping effects and 3D elastic effects in laminate material were considered. According to the actual stress state of the shell wall, the caculation model of the equivalent bending stiffness of the composite tube was established. By comparison with three-point bending experimental data and the equivalent bending stiffness calculated by classical laminated plate theory of four composite tubes, the calculation model was validated. The application of the calculation model was analyzed by comparing degradation of the present theory with the calculation method of bending stiffness of isotropic material.
In response to composite tube with arbitrary lamination and thickness, an approach of the equivalent bending stiffness was presented. The deformation theory with realistic deformation of composite tube beam was used in this analysis. Transverse shear deformation, non-uniform torsion effects, the primary and the secondary warping effects and 3D elastic effects in laminate material were considered. According to the actual stress state of the shell wall, the caculation model of the equivalent bending stiffness of the composite tube was established. By comparison with three-point bending experimental data and the equivalent bending stiffness calculated by classical laminated plate theory of four composite tubes, the calculation model was validated. The application of the calculation model was analyzed by comparing degradation of the present theory with the calculation method of bending stiffness of isotropic material.
2016, 33(8): 1702-1709.
doi: 10.13801/j.cnki.fhclxb.20151106.003
Abstract:
The finite element mechanical analysis model was established for the prediction of elastic properties of 2D woven fabric composite. Based on the geometrical features of 2D woven fabric composite, a parameterized unit cell model was established. The anisotropic material characteristics of the fiber bundles were considered, the principal direction of the material was converted to the direction of the fiber bundles buckling, and thus the finite element model for mechanical analysis was built. The insufficiency of the plane-keep-plane assumption for boundary surfaces of unit cell was analyzed and the universal periodic boundary conditions used for 2D woven fabric composite were proposed. Therefore, more accurate engineering elastic constants of 2D woven fabric composite were obtained. Results indicate that boundary surfaces of unit cell of fabric liner present concave and convex buckling deformation under uniaxial tensile and pure shear load, namely that periodic boundary is demonstrated. Based on the fabric parameterized geometric modeling method and finite element method presented, the engineering elastic constants can be obtained accurately, and the results of the numerical simulation are consistent with that of the experiment.
The finite element mechanical analysis model was established for the prediction of elastic properties of 2D woven fabric composite. Based on the geometrical features of 2D woven fabric composite, a parameterized unit cell model was established. The anisotropic material characteristics of the fiber bundles were considered, the principal direction of the material was converted to the direction of the fiber bundles buckling, and thus the finite element model for mechanical analysis was built. The insufficiency of the plane-keep-plane assumption for boundary surfaces of unit cell was analyzed and the universal periodic boundary conditions used for 2D woven fabric composite were proposed. Therefore, more accurate engineering elastic constants of 2D woven fabric composite were obtained. Results indicate that boundary surfaces of unit cell of fabric liner present concave and convex buckling deformation under uniaxial tensile and pure shear load, namely that periodic boundary is demonstrated. Based on the fabric parameterized geometric modeling method and finite element method presented, the engineering elastic constants can be obtained accurately, and the results of the numerical simulation are consistent with that of the experiment.
2016, 33(8): 1710-1717.
doi: 10.13801/j.cnki.fhclxb.20151210.001
Abstract:
For glass micro balloon/epoxy resin cement particle composite, the rigid frame-spring-damper model was put forward. Considering the damping properties of epoxy matrix, the loss factor was gotten under normal temperature and low frequency by the dynamic mechanical analysis, and used for this model. A rule of loss factor for glass micro balloon/epoxy resin cement composite changed along with the increase of radius of glass micro balloon could be obtained by numerical emulation analysis using finite element analysis method. The results show that the loss factor of particle composite caculated by the rigid frame-spring-damper model increases alone with the radius increase of glass micro balloon. In addition, the shear loss factor is higher than that of axial. For the integral material, the loss factor caculated by the rigid frame-spring-damper model is gradually increasing too. The loss factor caculated by the grid model arranged by plane quadrangle is higher than that of flat hexagonal. It means that the greater the porosity of particle composite, the higher the loss factor. The simulated analysis result is consistent with actual damper laws and it suggests that the model is reasonable.
For glass micro balloon/epoxy resin cement particle composite, the rigid frame-spring-damper model was put forward. Considering the damping properties of epoxy matrix, the loss factor was gotten under normal temperature and low frequency by the dynamic mechanical analysis, and used for this model. A rule of loss factor for glass micro balloon/epoxy resin cement composite changed along with the increase of radius of glass micro balloon could be obtained by numerical emulation analysis using finite element analysis method. The results show that the loss factor of particle composite caculated by the rigid frame-spring-damper model increases alone with the radius increase of glass micro balloon. In addition, the shear loss factor is higher than that of axial. For the integral material, the loss factor caculated by the rigid frame-spring-damper model is gradually increasing too. The loss factor caculated by the grid model arranged by plane quadrangle is higher than that of flat hexagonal. It means that the greater the porosity of particle composite, the higher the loss factor. The simulated analysis result is consistent with actual damper laws and it suggests that the model is reasonable.
2016, 33(8): 1718-1724.
doi: 10.13801/j.cnki.fhclxb.20151214.001
Abstract:
In winter road pavements are frequently covered by ice and snow because of the low temperature. Deicing salt is one way to deal with the icing coverage and clean the pavements. The SEM and bending beam rheometer (BBR) were used to study microstructure and rheological properties at low temperature of three kinds of asphalts (matrix asphalt, SBS(polystyrene-polybutadiene-polystyrene) modified asphalt and rubber powder modified asphalt) before and after the salt freezing cycle. The results show that the modified agent exists in asphalt with specific structure, and the two have good compatibility, which can adsorb asphalt better, so that the low temperature elasticity or viscosity of asphalt has been increased and then the low temperature performance of asphalt can been improved. After salt freezing cycle, the structure of asphalt has been damaged, which could affect the low temperature crack resistance of asphalt. The creep stiffness modulus of asphalt has been enlarged, and the creep strain rate of asphalt has been decreased after salt freezing cycle. As a result, the low temperature crack resistance and the stress relaxation ability have been reduced. However, the low temperature performance of modified asphalt is better than that of matrix asphalt. It is recommended that the north cold areas as far as possible choose modified asphalt as the pavement material.
In winter road pavements are frequently covered by ice and snow because of the low temperature. Deicing salt is one way to deal with the icing coverage and clean the pavements. The SEM and bending beam rheometer (BBR) were used to study microstructure and rheological properties at low temperature of three kinds of asphalts (matrix asphalt, SBS(polystyrene-polybutadiene-polystyrene) modified asphalt and rubber powder modified asphalt) before and after the salt freezing cycle. The results show that the modified agent exists in asphalt with specific structure, and the two have good compatibility, which can adsorb asphalt better, so that the low temperature elasticity or viscosity of asphalt has been increased and then the low temperature performance of asphalt can been improved. After salt freezing cycle, the structure of asphalt has been damaged, which could affect the low temperature crack resistance of asphalt. The creep stiffness modulus of asphalt has been enlarged, and the creep strain rate of asphalt has been decreased after salt freezing cycle. As a result, the low temperature crack resistance and the stress relaxation ability have been reduced. However, the low temperature performance of modified asphalt is better than that of matrix asphalt. It is recommended that the north cold areas as far as possible choose modified asphalt as the pavement material.
2016, 33(8): 1725-1732.
doi: 10.13801/j.cnki.fhclxb.20151214.002
Abstract:
A micromechanical model is developed to predict electro-magneto-thermo-elastic full-coupling behavior of smart materials based on the variational asymptotic homogenization method. Starting from the variational expression of energy functional derived from electro-magneto-thermo-elastic coupling constitutive equation of smart materials, the energy functional was asymptotically extended to a series of approximate functional by taking advantage of the small ratio of microscale to macroscale of unit cell. The fluctuation function of the field variables were obtained by minimizing the approximation functional, resulting in a micromechanical model which is as close as possible to the physical and engineering reality. This model was implemented by using finite element technology. The example results of BaTiO3-CoFe2O4 fiber/epoxy resin composites show that the constructed micromechanical model can accurately predict the electro-magneto-thermo-elastic behavior and recover the local distribution of multi-physical field.
A micromechanical model is developed to predict electro-magneto-thermo-elastic full-coupling behavior of smart materials based on the variational asymptotic homogenization method. Starting from the variational expression of energy functional derived from electro-magneto-thermo-elastic coupling constitutive equation of smart materials, the energy functional was asymptotically extended to a series of approximate functional by taking advantage of the small ratio of microscale to macroscale of unit cell. The fluctuation function of the field variables were obtained by minimizing the approximation functional, resulting in a micromechanical model which is as close as possible to the physical and engineering reality. This model was implemented by using finite element technology. The example results of BaTiO3-CoFe2O4 fiber/epoxy resin composites show that the constructed micromechanical model can accurately predict the electro-magneto-thermo-elastic behavior and recover the local distribution of multi-physical field.
2016, 33(8): 1733-1741.
doi: 10.13801/j.cnki.fhclxb.20151127.001
Abstract:
Anodic film on SiCP/Al alloy (2A12) composites was obtained by adipic-sulfuric acid process. The cracking behaviors and corrosion resistance of anodic film on SiCP/2A12 composites which was obtained at different anodized temperature (15-35 ℃) were analyzed after temperature shock.The micro morphology of anodic film on SiCP/2A12 composites was observed by using FE-SEM before and after temperature shock. Electrochemical impedance spectroscope (EIS) was used to study the corrosion resistance of anodic film on SiCP/2A12 composites before and after shock. The results show that the effect of temperature shock on anodic film on SiCP/2A12 composites obtained at different anodized temperatures was different.After treating by temperature shock, the crack density of anodic film on SiCP/2A12 composites gradually increases with the anodizing temperature increasing. The corrosion resistance of anodic film on SiCP/2A12 composites after temperature shock obtained at anodized temperature of 25 ℃ is best. The temperature shock resistance performance of anodic film on SiCP/2A12 composites is superior to that of 2A12 aluminium alloy oxidation film.
Anodic film on SiCP/Al alloy (2A12) composites was obtained by adipic-sulfuric acid process. The cracking behaviors and corrosion resistance of anodic film on SiCP/2A12 composites which was obtained at different anodized temperature (15-35 ℃) were analyzed after temperature shock.The micro morphology of anodic film on SiCP/2A12 composites was observed by using FE-SEM before and after temperature shock. Electrochemical impedance spectroscope (EIS) was used to study the corrosion resistance of anodic film on SiCP/2A12 composites before and after shock. The results show that the effect of temperature shock on anodic film on SiCP/2A12 composites obtained at different anodized temperatures was different.After treating by temperature shock, the crack density of anodic film on SiCP/2A12 composites gradually increases with the anodizing temperature increasing. The corrosion resistance of anodic film on SiCP/2A12 composites after temperature shock obtained at anodized temperature of 25 ℃ is best. The temperature shock resistance performance of anodic film on SiCP/2A12 composites is superior to that of 2A12 aluminium alloy oxidation film.
2016, 33(8): 1742-1748.
doi: 10.13801/j.cnki.fhclxb.20151022.004
Abstract:
The fly ash cenospheres (FAC) were added to semisolid AZ91D Mg alloy to prepare FAC/AZ91D Mg alloy composites by means of stir casting. The effect of particle size of FAC on the damping properties of this composites was investigated. The results show that the damping properties of FAC/AZ91D Mg alloy composites are better than those of matrix materials. When the content of FAC is the same, the damping properties of FAC/AZ91D Mg alloy composites rise with the increase of particle size of FAC. FAC plays a significant role in improving the damping properties of FAC/AZ91D Mg alloy composites at room temperature. The matrix nearby FAC can produce high density dislocations, which form the plastic zone. Under room temperature, the larger the particle size of FAC is, the greater the plastic zone is, which also leads to better damping properties. As the temperature increases, the damping properties of FAC/AZ91D Mg alloy composites go up rapidly. The dislocations, grain boundaries, and movement of the interfaces between FAC and matrix are the key points to enhance the damping properties.
The fly ash cenospheres (FAC) were added to semisolid AZ91D Mg alloy to prepare FAC/AZ91D Mg alloy composites by means of stir casting. The effect of particle size of FAC on the damping properties of this composites was investigated. The results show that the damping properties of FAC/AZ91D Mg alloy composites are better than those of matrix materials. When the content of FAC is the same, the damping properties of FAC/AZ91D Mg alloy composites rise with the increase of particle size of FAC. FAC plays a significant role in improving the damping properties of FAC/AZ91D Mg alloy composites at room temperature. The matrix nearby FAC can produce high density dislocations, which form the plastic zone. Under room temperature, the larger the particle size of FAC is, the greater the plastic zone is, which also leads to better damping properties. As the temperature increases, the damping properties of FAC/AZ91D Mg alloy composites go up rapidly. The dislocations, grain boundaries, and movement of the interfaces between FAC and matrix are the key points to enhance the damping properties.
2016, 33(8): 1749-1754.
doi: 10.13801/j.cnki.fhclxb.20151204.002
Abstract:
Based on Huang (Peking University) and Wang (Peking University)'s theory as well as the second thermodynamic law, the nonlinear compressive behaviors of closed-cell aluminum-alloy foams were studied at finite deformation. By means of introducing the internal variable and evolution equations of internal variable, the expressions of effective power-law potentials and stresses were presented whick taks meso-structural parameter and viscosity effect into consideration. With the presented theoretical models, some numerical examples were conducted to analyze the influences of micromechanics approaches, porosity and viscosity effect on the stress-strain curves of aluminum foams. The results show that the model predictions are basically agree with the experimental result. In addition, it is found that the model predictions considering the viscosity effect tend to the model predictions without considering the viscosity effect when the viscous coefficient becomes larger.
Based on Huang (Peking University) and Wang (Peking University)'s theory as well as the second thermodynamic law, the nonlinear compressive behaviors of closed-cell aluminum-alloy foams were studied at finite deformation. By means of introducing the internal variable and evolution equations of internal variable, the expressions of effective power-law potentials and stresses were presented whick taks meso-structural parameter and viscosity effect into consideration. With the presented theoretical models, some numerical examples were conducted to analyze the influences of micromechanics approaches, porosity and viscosity effect on the stress-strain curves of aluminum foams. The results show that the model predictions are basically agree with the experimental result. In addition, it is found that the model predictions considering the viscosity effect tend to the model predictions without considering the viscosity effect when the viscous coefficient becomes larger.
2016, 33(8): 1755-1761.
doi: 10.13801/j.cnki.fhclxb.20151217.004
Abstract:
LaFeO3, La0.8Sr0.2FeO3-δ and nonstoichiometric (La0.8Sr0.2)x FeO3-δ (x=0.97, 1.03) nanoparticles were fabricated via a simple solvothermal method. The morphologies and structures of the samples were characterized by XRD, TEM, UV-Vis, XPS and so on. Malachite green (MG) photodegradation was used as a model reaction to investigate the photocatalytic activity of these samples under the maximum absorption wavelength (616.9 nm). The results indicate that the doping of Sr2+ reduce the grain size and cause lattice defects and oxygen vacancies VO.. to be formed, which are in favor of hindering the recombination of electrons and holes, increasing the quantum efficiency. Doping Sr2+ and changing nonstoichiometry make the catalysts have strong absorption in visible region and large specific surface area. The specific surface area of (La0.8Sr0.2)1.03FeO3-δ is the largest (20.164 4 m2/g) and the visible degradation efficiency of (La0.8Sr0.2)1.03FeO3-δ is the highest(83.8%) among the catalysts. The photocatalytic activities of doped Sr2+ and nonstoichiometric LaFeO3 are higher than those of pure LaFeO3.
LaFeO3, La0.8Sr0.2FeO3-δ and nonstoichiometric (La0.8Sr0.2)x FeO3-δ (x=0.97, 1.03) nanoparticles were fabricated via a simple solvothermal method. The morphologies and structures of the samples were characterized by XRD, TEM, UV-Vis, XPS and so on. Malachite green (MG) photodegradation was used as a model reaction to investigate the photocatalytic activity of these samples under the maximum absorption wavelength (616.9 nm). The results indicate that the doping of Sr2+ reduce the grain size and cause lattice defects and oxygen vacancies VO.. to be formed, which are in favor of hindering the recombination of electrons and holes, increasing the quantum efficiency. Doping Sr2+ and changing nonstoichiometry make the catalysts have strong absorption in visible region and large specific surface area. The specific surface area of (La0.8Sr0.2)1.03FeO3-δ is the largest (20.164 4 m2/g) and the visible degradation efficiency of (La0.8Sr0.2)1.03FeO3-δ is the highest(83.8%) among the catalysts. The photocatalytic activities of doped Sr2+ and nonstoichiometric LaFeO3 are higher than those of pure LaFeO3.
2016, 33(8): 1762-1768.
doi: 10.13801/j.cnki.fhclxb.20151008.005
Abstract:
In order to improve the electrochemical performance of LiMn0.7Fe0.3PO4 (LMFP), the graphene oxide (GO)/LMFP composites were synthesized using solvothermal method by compound of GO and LMFP firstly. Then, structure and elements of the samples obtained were analyzed by XRD and inductively coupled plasma (ICP), the morphologies of samples were characterized by SEM, and the tests for electrochemical performances were conducted by program-controlled battery test system and electrochemical workstation. The results show that the GO/LMFP composites obtained are uniphase olivine structure, the particle size is about 200 nm and the distribution is relatively uniform. The initial discharge specific capacities of composite after the modification of GO were 157.9, 148.1, 142.0, 122.3, 87.3 mAh·g-1 at rates of 0.2C, 0.5C, 1.0C, 5.0C and 10.0C respectively, which increases 5.9%, 4.7%, 7.0%, 24.3% and 66.6% respectively compared with C/LMFP composite. The conclusions obtained show that the adding of GO improves the electronic conductivity and electrochemical activity of the material effectively, and synergistically effects on amorphous carbon, the effective utilization rate of active material increases, and the cycle stability of GO/LMFP composite improve.
In order to improve the electrochemical performance of LiMn0.7Fe0.3PO4 (LMFP), the graphene oxide (GO)/LMFP composites were synthesized using solvothermal method by compound of GO and LMFP firstly. Then, structure and elements of the samples obtained were analyzed by XRD and inductively coupled plasma (ICP), the morphologies of samples were characterized by SEM, and the tests for electrochemical performances were conducted by program-controlled battery test system and electrochemical workstation. The results show that the GO/LMFP composites obtained are uniphase olivine structure, the particle size is about 200 nm and the distribution is relatively uniform. The initial discharge specific capacities of composite after the modification of GO were 157.9, 148.1, 142.0, 122.3, 87.3 mAh·g-1 at rates of 0.2C, 0.5C, 1.0C, 5.0C and 10.0C respectively, which increases 5.9%, 4.7%, 7.0%, 24.3% and 66.6% respectively compared with C/LMFP composite. The conclusions obtained show that the adding of GO improves the electronic conductivity and electrochemical activity of the material effectively, and synergistically effects on amorphous carbon, the effective utilization rate of active material increases, and the cycle stability of GO/LMFP composite improve.
2016, 33(8): 1769-1776.
doi: 10.13801/j.cnki.fhclxb.20151123.001
Abstract:
By introducing Ti alloy interlayer between (Ti+B4C) reactant and Ti alloy substrate, the effect of thickness variations of Ti alloy interlayer on the microstructure and mechanical properties of the interface of TiB2 based ceramic/Ti-6Al-4V graded composites has been discussed, which were prepared by reaction bonding in high gravity field. The thermodynamic calculation shows that the adiabatic temperature of synthesis reaction is much higher than the melting point of Ti alloy, which ensures Ti alloy interlayer with different thickness completely melts. The XRD, FESEM and EDS analysis results show that the graded interface zone between ceramic and Ti alloy substrate forms, and the thickness of which increases with increasing thickness of Ti alloy interlayer. The volume fraction of TiB2 phase and TiC1-x gradually reduces, but the volume fraction of TiB first increases and then decreases from ceramic matrix to Ti alloy substrate, finally, on which there is the presence of the graded composite structures characterized by the size and distribution of TiB2, TiC1-x and TiB ceramic phases. And hardness distribution trend of the gradient connection area becomes smooth and shear strength improves gradually.
By introducing Ti alloy interlayer between (Ti+B4C) reactant and Ti alloy substrate, the effect of thickness variations of Ti alloy interlayer on the microstructure and mechanical properties of the interface of TiB2 based ceramic/Ti-6Al-4V graded composites has been discussed, which were prepared by reaction bonding in high gravity field. The thermodynamic calculation shows that the adiabatic temperature of synthesis reaction is much higher than the melting point of Ti alloy, which ensures Ti alloy interlayer with different thickness completely melts. The XRD, FESEM and EDS analysis results show that the graded interface zone between ceramic and Ti alloy substrate forms, and the thickness of which increases with increasing thickness of Ti alloy interlayer. The volume fraction of TiB2 phase and TiC1-x gradually reduces, but the volume fraction of TiB first increases and then decreases from ceramic matrix to Ti alloy substrate, finally, on which there is the presence of the graded composite structures characterized by the size and distribution of TiB2, TiC1-x and TiB ceramic phases. And hardness distribution trend of the gradient connection area becomes smooth and shear strength improves gradually.
2016, 33(8): 1777-1784.
doi: 10.13801/j.cnki.fhclxb.20151026.002
Abstract:
Usually, it requires extremely high temperature for preparation of SiC materials, so it is an important research direction for reducing the preparation temperature of SiC. SiC coating layer with a thickness of many microns on the ZrO2 spherical ceramic particles was synthesized using the fluidized bed chemical vapor deposition method. Through the study of microscopic morphology and microstructure change rule of SiC coating layer deposited at different temperatures, the deposition efficiency variation rule is obtained, and it is found that the low temperature product is silicon-rich, and the high-temperature product is carbon-rich. It is also found that the addition of argon can promote the deposition reaction toward to the carbon-rich direction by experimental study of different argon contents, so dense SiC coating layer can be prepared in the condition that the temperature is significantly reduced. Based on experimental results, the diagram map of SiC phase distribution with the variation of temperature and argon concentration in the fluidized bed chemical vapor deposition system is also given.
Usually, it requires extremely high temperature for preparation of SiC materials, so it is an important research direction for reducing the preparation temperature of SiC. SiC coating layer with a thickness of many microns on the ZrO2 spherical ceramic particles was synthesized using the fluidized bed chemical vapor deposition method. Through the study of microscopic morphology and microstructure change rule of SiC coating layer deposited at different temperatures, the deposition efficiency variation rule is obtained, and it is found that the low temperature product is silicon-rich, and the high-temperature product is carbon-rich. It is also found that the addition of argon can promote the deposition reaction toward to the carbon-rich direction by experimental study of different argon contents, so dense SiC coating layer can be prepared in the condition that the temperature is significantly reduced. Based on experimental results, the diagram map of SiC phase distribution with the variation of temperature and argon concentration in the fluidized bed chemical vapor deposition system is also given.
2016, 33(8): 1785-1793.
doi: 10.13801/j.cnki.fhclxb.20151201.001
Abstract:
Two kinds of thermal barrier coatings(TBCs) with different porosities at ceramic-coat and ceramic-coat/bond-coat interface by plasma spraying (PS) technology with NiCoCrAlY as bond-coat and 8wt% Y2O3 stabilized ZrO2 (8YSZ) as ceramic-coat. The difference of thermal cyclic lifetime of TBCs were studied, and the failure mechanism of TBCs with different porosities was analyzed. The distribution of stress in TBCs was calculated with finite element simulation, and the formation reason of the repeated parallel cracks in the porous TBCs and the failure mode of the two TBCs peeling were also analyzed. The cross-section microstructures and element distribution of TBCs were analyzed by using optical microscope(OM), SEM and EDX. The results show that the porous TBCs have a double longer lifetime than the dense TBCs. For the porous TBCs, as a consequence of the more pores and micro-cracks in ceramic-coats and interface to release the accumulated strain energy within the TBCs. At this time, the repeated parallel cracks in alumina layer further decrease the stress between ceramic-coats and bond-coats, which can prolong the lifetime of porous TBCs. Foundation for the structure design of the longer lifetime TBCs was laid.
Two kinds of thermal barrier coatings(TBCs) with different porosities at ceramic-coat and ceramic-coat/bond-coat interface by plasma spraying (PS) technology with NiCoCrAlY as bond-coat and 8wt% Y2O3 stabilized ZrO2 (8YSZ) as ceramic-coat. The difference of thermal cyclic lifetime of TBCs were studied, and the failure mechanism of TBCs with different porosities was analyzed. The distribution of stress in TBCs was calculated with finite element simulation, and the formation reason of the repeated parallel cracks in the porous TBCs and the failure mode of the two TBCs peeling were also analyzed. The cross-section microstructures and element distribution of TBCs were analyzed by using optical microscope(OM), SEM and EDX. The results show that the porous TBCs have a double longer lifetime than the dense TBCs. For the porous TBCs, as a consequence of the more pores and micro-cracks in ceramic-coats and interface to release the accumulated strain energy within the TBCs. At this time, the repeated parallel cracks in alumina layer further decrease the stress between ceramic-coats and bond-coats, which can prolong the lifetime of porous TBCs. Foundation for the structure design of the longer lifetime TBCs was laid.
2016, 33(8): 1794-1802.
doi: 10.13801/j.cnki.fhclxb.20160418.002
Abstract:
The MnO2/TiO2 composite electrodes were prepared with modifying MnO2 onto the anodized TiO2 nanotube arrays by the hydrothermal method. The supercapacitor was assembled with the two symmetric MnO2/TiO2 electrodes. The surface morphology, valence of the elements and electrochemical performance of the samples were characterized by FESEM, TEM, XPS and the electrochemical workstation. The results show that the MnO2 nanoparticles are uniformly loaded onto the outer and inner surface of the TiO2 nanotube array. The specific capacitance is 429.3 F/g at a charge-discharge current density of 1 A/g with 82.4% of the initial capacitance after 5 000 cycles. The MnO2/TiO2 symmetrical supercapacitor exhibits the charge-discharge specific capacitance of 39.9 F/g at the current density of 5 A/g with 91.5% of the initial capacitance after 5 000 cycles and the energy density of 18.98 Wh/kg at the power density of 400 W/kg. Not only the anodized TiO2 nanotube arrays could serve as the carrier of MnO2, but also the Ti substrate could be used for the current collector, which alleviates the weight of the supercapacitor and provides a method for preparing supercapacitors.
The MnO2/TiO2 composite electrodes were prepared with modifying MnO2 onto the anodized TiO2 nanotube arrays by the hydrothermal method. The supercapacitor was assembled with the two symmetric MnO2/TiO2 electrodes. The surface morphology, valence of the elements and electrochemical performance of the samples were characterized by FESEM, TEM, XPS and the electrochemical workstation. The results show that the MnO2 nanoparticles are uniformly loaded onto the outer and inner surface of the TiO2 nanotube array. The specific capacitance is 429.3 F/g at a charge-discharge current density of 1 A/g with 82.4% of the initial capacitance after 5 000 cycles. The MnO2/TiO2 symmetrical supercapacitor exhibits the charge-discharge specific capacitance of 39.9 F/g at the current density of 5 A/g with 91.5% of the initial capacitance after 5 000 cycles and the energy density of 18.98 Wh/kg at the power density of 400 W/kg. Not only the anodized TiO2 nanotube arrays could serve as the carrier of MnO2, but also the Ti substrate could be used for the current collector, which alleviates the weight of the supercapacitor and provides a method for preparing supercapacitors.
2016, 33(8): 1803-1811.
doi: 10.13801/j.cnki.fhclxb.20151027.003
Abstract:
In order to investigate the feasibility for the industry application of ramie stalk in treating heavy metal waste water, the microcosmic characterizations of ramie stalk particles were conducted by characterization methods such as laser particle size analyzer, SEM and FTIR etc. firstly, and the microstructure of ramie stalk was ascertained. Then based on those, water dispersible ramie stalk cake (WDRSC) were processed by mixing the ramie stalk particles with the environmental friendly natural wetting agent, adhesive and disintegrating agent according to a certain technological process. During the screen process of formula, the influences for the mass fractions of various additives on properties of WDRSC were tested, and the abilities of ramie stalk and WDRSC for adsorption of heavy metal Cu2+ and Cd2+ were compared. The results show that ramie stalk is a natural substance with porous structure, and a large number of adsorption sites and groups are related to the surface. When the mass ratio of ramie stalk, wetting agent, binder and disintegration agent in WDRSC formula is 75∶13∶2∶10, WDRSC can quickly be wetted (wetting time is less than 60 s) by water and automatic disintegration (disintegration time is less than 60 s) as soon as it touches water, the suspension rate within 60 s reaches about 80%, and the properties are all in accordance with the requirements of water dispersible granules. The related properties of WDRSC were affected by wetting agent, binder and disintegrating agent at different degrees. Comparing with ramie stalk, the removal rates of WDRSC for Cd2+ and Cu2+ improve 11% and 4% respectively. The conclusions obtained indicating that manufacturing ramie stalk into WDRSC has advantages such as convenient transportation and application, low costing, easy manufacturing process and convenient waste residue treatment after adsorption etc., which is a feasible method for the large-scale utilization for ramie stalk.
In order to investigate the feasibility for the industry application of ramie stalk in treating heavy metal waste water, the microcosmic characterizations of ramie stalk particles were conducted by characterization methods such as laser particle size analyzer, SEM and FTIR etc. firstly, and the microstructure of ramie stalk was ascertained. Then based on those, water dispersible ramie stalk cake (WDRSC) were processed by mixing the ramie stalk particles with the environmental friendly natural wetting agent, adhesive and disintegrating agent according to a certain technological process. During the screen process of formula, the influences for the mass fractions of various additives on properties of WDRSC were tested, and the abilities of ramie stalk and WDRSC for adsorption of heavy metal Cu2+ and Cd2+ were compared. The results show that ramie stalk is a natural substance with porous structure, and a large number of adsorption sites and groups are related to the surface. When the mass ratio of ramie stalk, wetting agent, binder and disintegration agent in WDRSC formula is 75∶13∶2∶10, WDRSC can quickly be wetted (wetting time is less than 60 s) by water and automatic disintegration (disintegration time is less than 60 s) as soon as it touches water, the suspension rate within 60 s reaches about 80%, and the properties are all in accordance with the requirements of water dispersible granules. The related properties of WDRSC were affected by wetting agent, binder and disintegrating agent at different degrees. Comparing with ramie stalk, the removal rates of WDRSC for Cd2+ and Cu2+ improve 11% and 4% respectively. The conclusions obtained indicating that manufacturing ramie stalk into WDRSC has advantages such as convenient transportation and application, low costing, easy manufacturing process and convenient waste residue treatment after adsorption etc., which is a feasible method for the large-scale utilization for ramie stalk.
2016, 33(8): 1812-1818.
doi: 10.13801/j.cnki.fhclxb.20151112.001
Abstract:
For investigating microstructure and deposition mechanism of the low temperature isotropic pyrocarbon(LTIC), LTIC was prepared by a steady-state fluidized bed chemical vapor deposition experiments at different deposition temperatures with propane as carbon source of different volume fractions. Microstructure of the LTIC obtained at different deposition conditions was characterized using SEM and TEM. The results show that the LTIC obtained at different deposition conditions is composed of globular-like granular and laminar carbon structure. Increasing the deposition temperature is propitious to decrease the nucleation barrier forming pyrocarbon in vapor, which causes the quantity of globular-like particles with a smaller diameter increasing and the texture of the carbon layer around carbon black particles inside globular-like particles decreasing gradually. With increasing the volume fraction of propane, pyrocarbon deposition process is mainly dominated by surficial growth mechanism, and transforms to the gaseous nucleation mechanism. The globular-like particle morphology in obtained LTIC is more obviously and laminar carbon structure gradually decreases and even disappear completely.
For investigating microstructure and deposition mechanism of the low temperature isotropic pyrocarbon(LTIC), LTIC was prepared by a steady-state fluidized bed chemical vapor deposition experiments at different deposition temperatures with propane as carbon source of different volume fractions. Microstructure of the LTIC obtained at different deposition conditions was characterized using SEM and TEM. The results show that the LTIC obtained at different deposition conditions is composed of globular-like granular and laminar carbon structure. Increasing the deposition temperature is propitious to decrease the nucleation barrier forming pyrocarbon in vapor, which causes the quantity of globular-like particles with a smaller diameter increasing and the texture of the carbon layer around carbon black particles inside globular-like particles decreasing gradually. With increasing the volume fraction of propane, pyrocarbon deposition process is mainly dominated by surficial growth mechanism, and transforms to the gaseous nucleation mechanism. The globular-like particle morphology in obtained LTIC is more obviously and laminar carbon structure gradually decreases and even disappear completely.
2016, 33(8): 1819-1829.
doi: 10.13801/j.cnki.fhclxb.20151106.001
Abstract:
According to the value of geometrical structure parameters and determined geometrical structure size of representative volume element (RVE) model of the fiber tow composites, finite element software MSC.Patran/Nastran as a platform to establish RVE finite element models of fiber tow composite and corresponding manufacturing defects were also implemented into the models. Grid element deletion method was utilized to implement all types of manufacturing defects. When crack-like manufacturing defects implemented into the RVE models, the crack width was obtained by moving the two opposite surfaces of the elements at the both sides of offset crack. The real morphologies of void-like manufacturing defects should be simulated as much as possible. According to material property parameter definitions of mechanics of composites and basic theories of micro-mechanics, the finite element computational micro-mechanics (FECM) methods to predict effective elastic properties and effective thermal expansion properties of composites were derived. Based on FECM methods, elastic constants and effective thermal expansion coefficients without manufacturing defects, containing a single manufacturing defect and containing all types of manufacturing defects were respectively predicted. The results show that the presence of all manufacturing defects will reduce elastic modulus and shear modulus, while Poisson's ratios and coefficients of thermal expansions may increase or decrease. Through comparison with the experimental test results, numerical prediction results are generally a little larger than experiment test results, but the overall effect is ideal. Wherein, the maximum relative error is 6.04%.
According to the value of geometrical structure parameters and determined geometrical structure size of representative volume element (RVE) model of the fiber tow composites, finite element software MSC.Patran/Nastran as a platform to establish RVE finite element models of fiber tow composite and corresponding manufacturing defects were also implemented into the models. Grid element deletion method was utilized to implement all types of manufacturing defects. When crack-like manufacturing defects implemented into the RVE models, the crack width was obtained by moving the two opposite surfaces of the elements at the both sides of offset crack. The real morphologies of void-like manufacturing defects should be simulated as much as possible. According to material property parameter definitions of mechanics of composites and basic theories of micro-mechanics, the finite element computational micro-mechanics (FECM) methods to predict effective elastic properties and effective thermal expansion properties of composites were derived. Based on FECM methods, elastic constants and effective thermal expansion coefficients without manufacturing defects, containing a single manufacturing defect and containing all types of manufacturing defects were respectively predicted. The results show that the presence of all manufacturing defects will reduce elastic modulus and shear modulus, while Poisson's ratios and coefficients of thermal expansions may increase or decrease. Through comparison with the experimental test results, numerical prediction results are generally a little larger than experiment test results, but the overall effect is ideal. Wherein, the maximum relative error is 6.04%.
2016, 33(8): 1830-1837.
doi: 10.13801/j.cnki.fhclxb.20160315.012
Abstract:
Cohesive zone model(CZM) was applied to numerical analysis of wavelet finite element method(WFEM) by using the excellent localization properties of interval B-spline wavelet, interface elements of wavelet cohesive zone were constructed by regarding interval B-spline wavelet scaling functions as the interpolation functions, stiffness matrix of interface elements of wavelet cohesive zone was derived, and strain energy release rate(SERR) of interface crack was calculated by using virtual crack closure technique(VCCT), and the quasi-static analysis of interface crack growth was achieved by taking β-Κ fracture criterion. The numerical analyzed results of SERR by WFEM and conventional finite element method(CFEM) were compared with theoretical results, and the results show that the SERR calculated by WFEM and CFEM are 96.60 J/m2 and 101.43 J/m2, respectively, and the relative errors of SERR between numerical and theoretical results of two method are 1.85% and 3.06%, respectively. It clearly indicates that WFEM can obtain higher accuracy and efficiency of calculating interface crack growth with less numbers of elements and nodes. On this basis, we studied the influence of initial interface crack length and bi-material elastic modulus ratio on interface crack growth. It is found that the equivalent stress at interface crack tip tends to increase with the increase of initial interface crack length. The difference of bi-material elastic modulus ratio is greater, interface crack is easier to expand, and the length of interface crack growth is also greater, therefore, interface crack growth can be slowed by adjusting bi-material elastic modulus ratio.
Cohesive zone model(CZM) was applied to numerical analysis of wavelet finite element method(WFEM) by using the excellent localization properties of interval B-spline wavelet, interface elements of wavelet cohesive zone were constructed by regarding interval B-spline wavelet scaling functions as the interpolation functions, stiffness matrix of interface elements of wavelet cohesive zone was derived, and strain energy release rate(SERR) of interface crack was calculated by using virtual crack closure technique(VCCT), and the quasi-static analysis of interface crack growth was achieved by taking β-Κ fracture criterion. The numerical analyzed results of SERR by WFEM and conventional finite element method(CFEM) were compared with theoretical results, and the results show that the SERR calculated by WFEM and CFEM are 96.60 J/m2 and 101.43 J/m2, respectively, and the relative errors of SERR between numerical and theoretical results of two method are 1.85% and 3.06%, respectively. It clearly indicates that WFEM can obtain higher accuracy and efficiency of calculating interface crack growth with less numbers of elements and nodes. On this basis, we studied the influence of initial interface crack length and bi-material elastic modulus ratio on interface crack growth. It is found that the equivalent stress at interface crack tip tends to increase with the increase of initial interface crack length. The difference of bi-material elastic modulus ratio is greater, interface crack is easier to expand, and the length of interface crack growth is also greater, therefore, interface crack growth can be slowed by adjusting bi-material elastic modulus ratio.
2016, 33(8): 1838-1847.
doi: 10.13801/j.cnki.fhclxb.20151204.003
Abstract:
In order to increase numerical calculation accuracy of hexagonal aluminum honeycomb sandwich plate, influences of length-thickness ratio on dynamic calculation accuracy of equivalent plate models were discussed. For the hexagonal aluminum honeycomb sandwich plate with cores which has uniform thickness of walls, equivalent plate models, including Reissner theory model, honeycomb plate theory model and the low-order shear laminated plate theory model were analyzed firstly. Then, natural frequencies of equivalent plate models were compared with those of the detailed model when their modal shapes were same. And influences of length-thickness ratio on the dynamics calculation accuracy of the equivalent plate models were analyzed. The results show that the calculation error on the natural frequencies of the homogenized core model is small; the low-order shear laminated plate theory model is a equivalent plate model with higher calculation accuracy; calculation accuracy of Reissner theory model is the lowest when length-thickness ratio is 7.37; the calculation accuracy of honeycomb plate theory model is lower on slab than on sheet; and the calculation accuracy of low-order shear laminated plate theory model is higher on slab than on sheet.
In order to increase numerical calculation accuracy of hexagonal aluminum honeycomb sandwich plate, influences of length-thickness ratio on dynamic calculation accuracy of equivalent plate models were discussed. For the hexagonal aluminum honeycomb sandwich plate with cores which has uniform thickness of walls, equivalent plate models, including Reissner theory model, honeycomb plate theory model and the low-order shear laminated plate theory model were analyzed firstly. Then, natural frequencies of equivalent plate models were compared with those of the detailed model when their modal shapes were same. And influences of length-thickness ratio on the dynamics calculation accuracy of the equivalent plate models were analyzed. The results show that the calculation error on the natural frequencies of the homogenized core model is small; the low-order shear laminated plate theory model is a equivalent plate model with higher calculation accuracy; calculation accuracy of Reissner theory model is the lowest when length-thickness ratio is 7.37; the calculation accuracy of honeycomb plate theory model is lower on slab than on sheet; and the calculation accuracy of low-order shear laminated plate theory model is higher on slab than on sheet.
2016, 33(8): 1848-1858.
doi: 10.13801/j.cnki.fhclxb.20151216.003
Abstract:
A numerical modeling approach of the elastic field under line contacts was proposed with taking the heterogeneous properties of the materials into consideration. The method was on the basis of the numerical equivalent inclusion method (NEIM), utilizing the rectangular heterogeneous material as the basic element. Integrated with the method of images, the elastic field of the materials under line contacts could be solved. Taking advantage of the methods of comparison validation, parametric analysis and examples of verification, the result yielded by the new method was compared with the result produced by the finite element method (FEM) and conventional equivalent inclusion method (EIM), and investigated the effects of heterogeneous material distribution parameters on the contact performance of material under line contacts. The results show that the new method is more advantageous than the FEM and the conventional EIM, and able to handle and simplify the coating problem and the line contact of randomly distributed heterogeneous material. Different locations of heterogeneous material may make the maximum von Mises stress of the matrix become bigger or smaller. The size of heterogeneous material and the difference between the heterogeneous material and the matrix may influence the stress concentration level of the matrix.
A numerical modeling approach of the elastic field under line contacts was proposed with taking the heterogeneous properties of the materials into consideration. The method was on the basis of the numerical equivalent inclusion method (NEIM), utilizing the rectangular heterogeneous material as the basic element. Integrated with the method of images, the elastic field of the materials under line contacts could be solved. Taking advantage of the methods of comparison validation, parametric analysis and examples of verification, the result yielded by the new method was compared with the result produced by the finite element method (FEM) and conventional equivalent inclusion method (EIM), and investigated the effects of heterogeneous material distribution parameters on the contact performance of material under line contacts. The results show that the new method is more advantageous than the FEM and the conventional EIM, and able to handle and simplify the coating problem and the line contact of randomly distributed heterogeneous material. Different locations of heterogeneous material may make the maximum von Mises stress of the matrix become bigger or smaller. The size of heterogeneous material and the difference between the heterogeneous material and the matrix may influence the stress concentration level of the matrix.
