2014 Vol. 31, No. 2
2014, 31(2): 255-262.
Abstract:
Using graphene oxide (GO) and tetrabutyl orthotitanate (Ti(OBu)4) as raw materials, the graphene/nano TiO2 composites were synthesized via a solvothermal reaction in ethanol solvent. The crystal structure, morphology and element form of graphene/nano TiO2 composites were characterized by XRD, FE-SEM, TEM, RAMAN and XPS. And the photocatalytic activity of graphene/nanoTiO2 composites was investigated by the photocatalytic degradation of methyl orange in aqueous solution. The results show that Ti(OBu)4 molecules are uniformly grafted on GO by chemisorption in ethanol solvent, both of the reduction of GO and deposition of anatase TiO2 nanoparticles on GO are achieved during the solvothermal process. With prolongation of solvothermal reaction, the content of active groups on GO quickly decreases, so GO is reduced more firmly. Meanwhile, the size of TiO2 crystal particles increases with the prolongation of solvothermal reaction. Compared to pure TiO2, the graphene/nano TiO2 composites exhibit higher photocatalytic activity, and the graphene ratios in composites have direct impact on the photocatalytic activity.
Using graphene oxide (GO) and tetrabutyl orthotitanate (Ti(OBu)4) as raw materials, the graphene/nano TiO2 composites were synthesized via a solvothermal reaction in ethanol solvent. The crystal structure, morphology and element form of graphene/nano TiO2 composites were characterized by XRD, FE-SEM, TEM, RAMAN and XPS. And the photocatalytic activity of graphene/nanoTiO2 composites was investigated by the photocatalytic degradation of methyl orange in aqueous solution. The results show that Ti(OBu)4 molecules are uniformly grafted on GO by chemisorption in ethanol solvent, both of the reduction of GO and deposition of anatase TiO2 nanoparticles on GO are achieved during the solvothermal process. With prolongation of solvothermal reaction, the content of active groups on GO quickly decreases, so GO is reduced more firmly. Meanwhile, the size of TiO2 crystal particles increases with the prolongation of solvothermal reaction. Compared to pure TiO2, the graphene/nano TiO2 composites exhibit higher photocatalytic activity, and the graphene ratios in composites have direct impact on the photocatalytic activity.
2014, 31(2): 263-272.
Abstract:
Graphene, a flat monolayer of carbon atom tightly packed into a two-dimensional honeycomb lattice, shows many unique physical and chemical properties and has good application prospect in various fields. Currently, the preparation and potential application of graphene and nano graphene composites have become the most important research frontiers. Herein, based on the structure and performance of graphene, the four preparation methods-mechanical exfoliation method, chemical vapor deposition method, chemical exfoliation method and chemical synthesis method are introduced. A comprehensive review is presented to introduce the preparation and potential application of nano graphene/polymer composites and nano inorganic/graphene composites. The unique advantages of nano graphene composites in biological medicine, electronic devices, microwave absorption, sensors and electrode materials are also reviewed. Future research and potential application of nano graphene composites are also prospected.
Graphene, a flat monolayer of carbon atom tightly packed into a two-dimensional honeycomb lattice, shows many unique physical and chemical properties and has good application prospect in various fields. Currently, the preparation and potential application of graphene and nano graphene composites have become the most important research frontiers. Herein, based on the structure and performance of graphene, the four preparation methods-mechanical exfoliation method, chemical vapor deposition method, chemical exfoliation method and chemical synthesis method are introduced. A comprehensive review is presented to introduce the preparation and potential application of nano graphene/polymer composites and nano inorganic/graphene composites. The unique advantages of nano graphene composites in biological medicine, electronic devices, microwave absorption, sensors and electrode materials are also reviewed. Future research and potential application of nano graphene composites are also prospected.
2014, 31(2): 273-285.
Abstract:
The latest research progress of interleaving of fibre-reinforced thermoset polymer matrix composite (PMC) is reviewed. Thermoset composites are brittle due to the high crosslink density of the matrix resin, which exhibit low impact damage resistance and damage tolerance. Interleaving of the flexible polymer improves interlaminar fracture toughness and damage resistance without sacrificing the excellent thermal properties and high modulus of the thermosets.There are three types of interleaving methods which seem to be the most frequently reported methods, namely particle, polymer fiber and polymer film interleaving. The concept, implementary methods, toughening mechanism and research results are discussed. Finally, the emphasis on interleaving composites by innovative ex-situ concept is putted. Ex-situ high-performance technology system for composites with intellectual property consisting of prepreg-based and liquid molding composites are introduced.
The latest research progress of interleaving of fibre-reinforced thermoset polymer matrix composite (PMC) is reviewed. Thermoset composites are brittle due to the high crosslink density of the matrix resin, which exhibit low impact damage resistance and damage tolerance. Interleaving of the flexible polymer improves interlaminar fracture toughness and damage resistance without sacrificing the excellent thermal properties and high modulus of the thermosets.There are three types of interleaving methods which seem to be the most frequently reported methods, namely particle, polymer fiber and polymer film interleaving. The concept, implementary methods, toughening mechanism and research results are discussed. Finally, the emphasis on interleaving composites by innovative ex-situ concept is putted. Ex-situ high-performance technology system for composites with intellectual property consisting of prepreg-based and liquid molding composites are introduced.
2014, 31(2): 286-294.
Abstract:
Molecular dynamics simulations of carbon nanotube/polyethylene composites have been implemented to calculate the structures, thermodynamical and mechanical properties, investigating their relationship with the filling rate and simulation temperature. The results show that carbon nanotube/polyethylene composites are in isotropic amorphous structures, with the polyethylene and carbon nanotubes combining together by intense van der Waals force. The periodicity of carbon atomic arrangement on carbon nanotube wall declines within the effects of polyethylene matrix, representing flexural and plicate deformations. Based on the energy consideration, the higher stability can be obtained with more carbon nanotube filling in composites. The carbon nanotube/polyethylene composites also exhibit higher isometric heat capacities, and negative thermal pressure coefficients with better temperature stability, which decrease explicitly with increased temperature and composite filling rate respectively, compared with polyethylene system. The mechanical properties of carbon nanotube/polyethylene composites present isotropic elastic constant tensors with substantially higher elastic modulus and Poisson ratio than those of polyethylene system, both of which decline with elevated temperature and reduced carbon filling simultaneously, indicating the extraordinary improvement in mechanical properties with the carbon nanotube filler.
Molecular dynamics simulations of carbon nanotube/polyethylene composites have been implemented to calculate the structures, thermodynamical and mechanical properties, investigating their relationship with the filling rate and simulation temperature. The results show that carbon nanotube/polyethylene composites are in isotropic amorphous structures, with the polyethylene and carbon nanotubes combining together by intense van der Waals force. The periodicity of carbon atomic arrangement on carbon nanotube wall declines within the effects of polyethylene matrix, representing flexural and plicate deformations. Based on the energy consideration, the higher stability can be obtained with more carbon nanotube filling in composites. The carbon nanotube/polyethylene composites also exhibit higher isometric heat capacities, and negative thermal pressure coefficients with better temperature stability, which decrease explicitly with increased temperature and composite filling rate respectively, compared with polyethylene system. The mechanical properties of carbon nanotube/polyethylene composites present isotropic elastic constant tensors with substantially higher elastic modulus and Poisson ratio than those of polyethylene system, both of which decline with elevated temperature and reduced carbon filling simultaneously, indicating the extraordinary improvement in mechanical properties with the carbon nanotube filler.
2014, 31(2): 295-303.
Abstract:
The Z-pinned woven composite unit cell models of lamina and laminate were developed based on the plain woven composite micro-structure with carbon fiber reinforced after Z-pin inserted. The influence of Z-pin diameter and distribution interval on the in-plane longitudinal tensile mechanical properties was predicted. The stress concentration around Z-pin in the Z-pinned woven composite unit cell model was recognized. The strength would be reduced after unit cell been failed due to the stress concentration. The process of Z-pin pulled out from laminated plates was simulated. The pull-out force versus displacement curves with different Z-pin diameters and thicknesses of separate sub layer were obtained. The double cantilever beam (DCB) with nonlinear spring element and virtual crack closure technique (VCCT) was developed. The mode I crack propagation of Z-pinned laminate was simulated. It was concluded that equivalent mode I energy release rate G IC of the laminate and its waviness amplitude were larger caused by larger Z-pin diameter. Moreover, the denser the Z-pin distribution was, the larger GICwas and the smaller its wavelength was.
The Z-pinned woven composite unit cell models of lamina and laminate were developed based on the plain woven composite micro-structure with carbon fiber reinforced after Z-pin inserted. The influence of Z-pin diameter and distribution interval on the in-plane longitudinal tensile mechanical properties was predicted. The stress concentration around Z-pin in the Z-pinned woven composite unit cell model was recognized. The strength would be reduced after unit cell been failed due to the stress concentration. The process of Z-pin pulled out from laminated plates was simulated. The pull-out force versus displacement curves with different Z-pin diameters and thicknesses of separate sub layer were obtained. The double cantilever beam (DCB) with nonlinear spring element and virtual crack closure technique (VCCT) was developed. The mode I crack propagation of Z-pinned laminate was simulated. It was concluded that equivalent mode I energy release rate G IC of the laminate and its waviness amplitude were larger caused by larger Z-pin diameter. Moreover, the denser the Z-pin distribution was, the larger GICwas and the smaller its wavelength was.
2014, 31(2): 304-316.
Abstract:
In order to choose the best parameters of tackifier in vacuum assisted resin infusion (VARI) processing, the distribution of tackifier on fabrics, effects of different addition levels of tackifier on epoxide resin and mechanical performance of composites reinforced by uniaxial warp-knitting fabrics were investigated. Effects of addition levels of tackifier on the glass transition temperature and phase configuration of epoxide resin were analyzed by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). Mechanical performances of composites with various amounts of tackifier were examined. It is shown that as the addition level of tackifier increases, the glass transition temperature of epoxide resin decreases, and its phase configuration transferred from sea island structure to double continuous-phase, then, at last to phase inversion structure. At room temperature, the thickness and irregularity of tackifier on surface of fabrics were increasing with increasing tackifier. After high-temperature processing, the tackifier have uniformly distributed onto the surface of fabrics. Addition levels of tackifier have significant effects on the mechanical properties of composites. The comprehensive mechanical properties of composites reinforced by uniaxial warp-knitting fabrics reach the best when the addition level of tackifier remains at 20 g/m2.
In order to choose the best parameters of tackifier in vacuum assisted resin infusion (VARI) processing, the distribution of tackifier on fabrics, effects of different addition levels of tackifier on epoxide resin and mechanical performance of composites reinforced by uniaxial warp-knitting fabrics were investigated. Effects of addition levels of tackifier on the glass transition temperature and phase configuration of epoxide resin were analyzed by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). Mechanical performances of composites with various amounts of tackifier were examined. It is shown that as the addition level of tackifier increases, the glass transition temperature of epoxide resin decreases, and its phase configuration transferred from sea island structure to double continuous-phase, then, at last to phase inversion structure. At room temperature, the thickness and irregularity of tackifier on surface of fabrics were increasing with increasing tackifier. After high-temperature processing, the tackifier have uniformly distributed onto the surface of fabrics. Addition levels of tackifier have significant effects on the mechanical properties of composites. The comprehensive mechanical properties of composites reinforced by uniaxial warp-knitting fabrics reach the best when the addition level of tackifier remains at 20 g/m2.
2014, 31(2): 317-322.
Abstract:
A new method of analyzing the dynamic wetting of fiberglass with infiltration liquid by linear regression analysis was proposed. The dynamic wettability of fiberglass surface was characterized, combining the use of precision electronic balance. The results show that the dynamic contact angle has an increasing trend with the increase of wetting velocity during the dynamic wetting process of fiberglass. Precisely, the contact angle of fiberglass and deionized water, ethylene glycol, 760E epoxy, CYD128 epoxy can increase from 66.04°, 42.21°, 51.31°, 73.90° to 69.05°, 46.95°, 74.58°, 170.06°, respectively, while the wettability of the fiberglass decreases. When the wetting rate increases, the greater the viscosity is, the faster the wettability declines during the dynamic wetting process of fiberglass. That is, the contact angle of fiberglass and CYD128 epoxy decreases by 96.16°, whereas the figures for 760E epoxy resin and ethylene glycol are 23.27° and 4.74°, respectively. Based on the new method, the force applied against the fiberglass increases with the rise of the moving velocity of three-phase contact line and the viscosity of infiltration liquid in the dynamic wetting system.
A new method of analyzing the dynamic wetting of fiberglass with infiltration liquid by linear regression analysis was proposed. The dynamic wettability of fiberglass surface was characterized, combining the use of precision electronic balance. The results show that the dynamic contact angle has an increasing trend with the increase of wetting velocity during the dynamic wetting process of fiberglass. Precisely, the contact angle of fiberglass and deionized water, ethylene glycol, 760E epoxy, CYD128 epoxy can increase from 66.04°, 42.21°, 51.31°, 73.90° to 69.05°, 46.95°, 74.58°, 170.06°, respectively, while the wettability of the fiberglass decreases. When the wetting rate increases, the greater the viscosity is, the faster the wettability declines during the dynamic wetting process of fiberglass. That is, the contact angle of fiberglass and CYD128 epoxy decreases by 96.16°, whereas the figures for 760E epoxy resin and ethylene glycol are 23.27° and 4.74°, respectively. Based on the new method, the force applied against the fiberglass increases with the rise of the moving velocity of three-phase contact line and the viscosity of infiltration liquid in the dynamic wetting system.
2014, 31(2): 323-330.
Abstract:
The thio-functionalized nano-Fe3O4-polymer magnetic composite material (SH-nFe3O4-polymer) was synthesized via suspension polymerization. The SH-nFe3O4-polymer was characterized by TGA, EA, AAS, XRD, FTIR, TEM and VSM. The application for its adsorption properties on the methylene blue (MB) from water was investigated. The results show that the SH-nFe3O4-polymer has an average size of 250-300 nm, with the saturation magnetization intensity of 5.88 emu/g. The adsorption capacities were investigated by adsorbing the MB from aqueous solutions, which demonstrate an excellent adsorption capacity with the maximum adsorption capacity at 476.2 mg/g, much higher than those of the tetraethylenepentamine-functionalized nano-Fe3O4-polymer magnetic composite (TEPA-nFe3O4-polymer, 30.6 mg/g) and the thiol-functionalized polymer free of magnetic core (SH-polymer, 74.6 mg/g). The isothermal adsorption curve mainly obeys the Langmuir mode. The adsorption thermodynamic studies suggest that the adsorption processes of the MB by the SH-nFe3O4-polymer are endothermic, entropy favored, and spontaneous in nature. The adsorption kinetic studies show that the adsorption processes reach the equilibrium within 10 min and the kinetic data are well fitted to the pseudo-second-order model. The activation energy for the MB removal is found to be 9.53 kJ/mol. The MB in aqueous solution can be effectively removed by the SH-n Fe3O4-polymer. The primary mechanism studies reveal that the adsorption processes may be related to the electrostatic attraction, π-π and hydrophobic interactions between the MB and the SH-nFe3O4-polymer. The existing of the magnetic core might be favorable to the mass transfer thus accelerating the adsorption process.
The thio-functionalized nano-Fe3O4-polymer magnetic composite material (SH-nFe3O4-polymer) was synthesized via suspension polymerization. The SH-nFe3O4-polymer was characterized by TGA, EA, AAS, XRD, FTIR, TEM and VSM. The application for its adsorption properties on the methylene blue (MB) from water was investigated. The results show that the SH-nFe3O4-polymer has an average size of 250-300 nm, with the saturation magnetization intensity of 5.88 emu/g. The adsorption capacities were investigated by adsorbing the MB from aqueous solutions, which demonstrate an excellent adsorption capacity with the maximum adsorption capacity at 476.2 mg/g, much higher than those of the tetraethylenepentamine-functionalized nano-Fe3O4-polymer magnetic composite (TEPA-nFe3O4-polymer, 30.6 mg/g) and the thiol-functionalized polymer free of magnetic core (SH-polymer, 74.6 mg/g). The isothermal adsorption curve mainly obeys the Langmuir mode. The adsorption thermodynamic studies suggest that the adsorption processes of the MB by the SH-nFe3O4-polymer are endothermic, entropy favored, and spontaneous in nature. The adsorption kinetic studies show that the adsorption processes reach the equilibrium within 10 min and the kinetic data are well fitted to the pseudo-second-order model. The activation energy for the MB removal is found to be 9.53 kJ/mol. The MB in aqueous solution can be effectively removed by the SH-n Fe3O4-polymer. The primary mechanism studies reveal that the adsorption processes may be related to the electrostatic attraction, π-π and hydrophobic interactions between the MB and the SH-nFe3O4-polymer. The existing of the magnetic core might be favorable to the mass transfer thus accelerating the adsorption process.
2014, 31(2): 331-337.
Abstract:
Based on an optical interference phase-contrast theory in the spectral domain, we propose a B-scan method to measure the out-of-plane displacement inside the glass fiber/polymer composite. In order to quantify its performance, composite members are specially designed, in which the polymer layer, air layer and glass layer represented the polymer base, crack and glass fiber in glass fiber/polymer composite. The measurement is executed by two snapping the interferograms before and after the load are applied, therefore, the processing is rapid. The system has the properties as: the field of view is 3.5 mm, the resolution of the contour is ±26.6 μm, the resolution of the out-of-plane displacement is ±0.1 μm, the range of the depth is 2.66 mm. This technology has a bright future in the mechanical properties measurement and non-destructive testing of the glass fiber reinforced resin matrix composite.
Based on an optical interference phase-contrast theory in the spectral domain, we propose a B-scan method to measure the out-of-plane displacement inside the glass fiber/polymer composite. In order to quantify its performance, composite members are specially designed, in which the polymer layer, air layer and glass layer represented the polymer base, crack and glass fiber in glass fiber/polymer composite. The measurement is executed by two snapping the interferograms before and after the load are applied, therefore, the processing is rapid. The system has the properties as: the field of view is 3.5 mm, the resolution of the contour is ±26.6 μm, the resolution of the out-of-plane displacement is ±0.1 μm, the range of the depth is 2.66 mm. This technology has a bright future in the mechanical properties measurement and non-destructive testing of the glass fiber reinforced resin matrix composite.
2014, 31(2): 338-344.
Abstract:
The betula alnoides wood powders are treated by xylanase solution. The betula alnoides/HDPE composites are prepared by hot-pressing forming technique. The effects of the solution reaction time, temperature and concentration on the tensile strength and the bending strength of the betula alnoides/HDPE composites are investigated. The optimum chemical reaction conditions of the betula alnoides wood powders in the xylanase solution are established. The transformation of chemical functional groups of the betula alnoides wood fibers are analyzed by FTIR and their morphologies of fracture surfaces are observed using SEM. The results show that the interfacial bonding in the betula alnoides/HDPE composites are enhanced after xylanase solution. After the wood fibers are treated in a xylanase solution of concentration 2.67 mg/L under the conditions of a temperature of 40℃ and a pH of 4.5 during 2 h, the relative content and crystallinity of cellulose and the relative content of lignin increase in the betula alnoides wood fibers, while the relative content of hemicellulose decrease. The comprehensive mechanical properties of the betula alnoides/HDPE composites are enhanced due to the increased interface area between plastic and treated wood fibers whose surface become softer and rougher.
The betula alnoides wood powders are treated by xylanase solution. The betula alnoides/HDPE composites are prepared by hot-pressing forming technique. The effects of the solution reaction time, temperature and concentration on the tensile strength and the bending strength of the betula alnoides/HDPE composites are investigated. The optimum chemical reaction conditions of the betula alnoides wood powders in the xylanase solution are established. The transformation of chemical functional groups of the betula alnoides wood fibers are analyzed by FTIR and their morphologies of fracture surfaces are observed using SEM. The results show that the interfacial bonding in the betula alnoides/HDPE composites are enhanced after xylanase solution. After the wood fibers are treated in a xylanase solution of concentration 2.67 mg/L under the conditions of a temperature of 40℃ and a pH of 4.5 during 2 h, the relative content and crystallinity of cellulose and the relative content of lignin increase in the betula alnoides wood fibers, while the relative content of hemicellulose decrease. The comprehensive mechanical properties of the betula alnoides/HDPE composites are enhanced due to the increased interface area between plastic and treated wood fibers whose surface become softer and rougher.
2014, 31(2): 345-352.
Abstract:
HT-350RTM, a novel high temperature polyimide resin for resin transfer molding (RTM) process, was synthesized through an optimized proportion of diamine monomer. 4-phenylethynylphthalic anhydride (4-PEPA) was employed as the end-capping agent of HT-350RTM resin, and 2, 3, 3', 4'-biphenyltetracarboxylic dianhydride (α-BPDA) used as its dianhydride monomer. U3160/HT-350RTM laminates were fabricated by RTM process reinforced by U3160 carbon fabric for evaluation of mechanical properties. The results show that the lowest melt viscosity of HT-350RTM is 390 mPa·s, and it stays below 1 Pa·s for over 2 h at 280℃, which qualifies the possibility for RTM process. After being cured, the glass transition temperature is 392℃ and the decomposition temperature(5% loss) is 537℃. The porosity of U3160/HT-350RTM laminates is only 0.34%. The U3160/HT-350RTM composites exhibit excellent mechanical properties at room temperature, and the retention rates of mechanical properties at 315℃ and 350℃ are both more than 60%, making the U3160/HT-350RTM composites ideal for the long-term use under 350℃.
HT-350RTM, a novel high temperature polyimide resin for resin transfer molding (RTM) process, was synthesized through an optimized proportion of diamine monomer. 4-phenylethynylphthalic anhydride (4-PEPA) was employed as the end-capping agent of HT-350RTM resin, and 2, 3, 3', 4'-biphenyltetracarboxylic dianhydride (α-BPDA) used as its dianhydride monomer. U3160/HT-350RTM laminates were fabricated by RTM process reinforced by U3160 carbon fabric for evaluation of mechanical properties. The results show that the lowest melt viscosity of HT-350RTM is 390 mPa·s, and it stays below 1 Pa·s for over 2 h at 280℃, which qualifies the possibility for RTM process. After being cured, the glass transition temperature is 392℃ and the decomposition temperature(5% loss) is 537℃. The porosity of U3160/HT-350RTM laminates is only 0.34%. The U3160/HT-350RTM composites exhibit excellent mechanical properties at room temperature, and the retention rates of mechanical properties at 315℃ and 350℃ are both more than 60%, making the U3160/HT-350RTM composites ideal for the long-term use under 350℃.
2014, 31(2): 353-361.
Abstract:
Mg-Al layered double hydroxides (LDHs) precursor was synthesized by coprecipitation method under mild conditions. The crystallization of LDHs was modulated with a small amount of ammonium polyphosphate (APP) to prepare APP-LDHs and the influence of APP at different mass fraction on the crystallization was investigated. When the addition of APP in LDHs suspension was 0.8wt%, the APP-LDHs was mixed with pentaerythritol (PER) and silane coupling agent KH-550 via ball milling and the modified LDHs (modified-LDHs) was completed ultimately. XRD, FTIR, SEM, TG were utilized to characterize the structure, morphology and thermal stability of the LDHs. The fire retardancy of LDHs/PP composites were evaluated by UL-94 test and limiting oxygen index (LOI), as well as the mechanical behavior was assessed, using flexural strength and notch impact strength. The results demonstrate that the crystal growth of LDHs is inhibited along the stacking direction in the presence of APP, but the grain size which represents layer growth remains unchanged. SEM images of the LDHs indicates sheet-like structure of the as-prepared LDHs, while the APP-LDHs modified by PER and KH-550 via ball milling shows that the modified-LDHs formed a regular powder with particle size of 100 nm to 250 nm. The modified-LDHs performs a better thermal stability at higher temperature. PP fills with 20 % mass fraction of LDHs burnt without droplet and the surface of LDHs/PP composites residue are covered with an expanded char network. Modified-LDHs/PP composite has superior flexural strength and notch impact strength compares with LDHs/PP and APP-LDHs/PP composites.
Mg-Al layered double hydroxides (LDHs) precursor was synthesized by coprecipitation method under mild conditions. The crystallization of LDHs was modulated with a small amount of ammonium polyphosphate (APP) to prepare APP-LDHs and the influence of APP at different mass fraction on the crystallization was investigated. When the addition of APP in LDHs suspension was 0.8wt%, the APP-LDHs was mixed with pentaerythritol (PER) and silane coupling agent KH-550 via ball milling and the modified LDHs (modified-LDHs) was completed ultimately. XRD, FTIR, SEM, TG were utilized to characterize the structure, morphology and thermal stability of the LDHs. The fire retardancy of LDHs/PP composites were evaluated by UL-94 test and limiting oxygen index (LOI), as well as the mechanical behavior was assessed, using flexural strength and notch impact strength. The results demonstrate that the crystal growth of LDHs is inhibited along the stacking direction in the presence of APP, but the grain size which represents layer growth remains unchanged. SEM images of the LDHs indicates sheet-like structure of the as-prepared LDHs, while the APP-LDHs modified by PER and KH-550 via ball milling shows that the modified-LDHs formed a regular powder with particle size of 100 nm to 250 nm. The modified-LDHs performs a better thermal stability at higher temperature. PP fills with 20 % mass fraction of LDHs burnt without droplet and the surface of LDHs/PP composites residue are covered with an expanded char network. Modified-LDHs/PP composite has superior flexural strength and notch impact strength compares with LDHs/PP and APP-LDHs/PP composites.
2014, 31(2): 362-367.
Abstract:
Bamboo fibers (BF)/polylactic acid (PLA) biodegradable composites are prepared by injection molding process. The natural degradation properties of BF/PLA composites were studied by the methods of X-ray differaction XRD, gel permeation chromatograph(GPC), 3D video microscope and scanning electron microscope(SEM). The results show that, BF is first degraded in natural degradation of composites, and PLA is degraded stratified, resulting in significant mass loss of composites; ester groups in PLA molecule chain react with water, which fractur molecular chain and declined crystallinity, the average molecular weight of PLA is gradually decreased and the molecular weight distribution narrows; the BF/PLA composites become dark with rough surface, partial nudity BF is visible, and tensile and impact strengths of composites reduce. After 12 month degradation, the mass loss rate of BF/PLA composites reachs 8.87%, the average molecular weight of the PLA in composites is reduced by 25.9%, the impact and tensile strengths of composites are reduced by 44.0% and 43.8% respectively. The natural degradation of BF/PLA biodegradable composites in the soil is relatively slow.
Bamboo fibers (BF)/polylactic acid (PLA) biodegradable composites are prepared by injection molding process. The natural degradation properties of BF/PLA composites were studied by the methods of X-ray differaction XRD, gel permeation chromatograph(GPC), 3D video microscope and scanning electron microscope(SEM). The results show that, BF is first degraded in natural degradation of composites, and PLA is degraded stratified, resulting in significant mass loss of composites; ester groups in PLA molecule chain react with water, which fractur molecular chain and declined crystallinity, the average molecular weight of PLA is gradually decreased and the molecular weight distribution narrows; the BF/PLA composites become dark with rough surface, partial nudity BF is visible, and tensile and impact strengths of composites reduce. After 12 month degradation, the mass loss rate of BF/PLA composites reachs 8.87%, the average molecular weight of the PLA in composites is reduced by 25.9%, the impact and tensile strengths of composites are reduced by 44.0% and 43.8% respectively. The natural degradation of BF/PLA biodegradable composites in the soil is relatively slow.
2014, 31(2): 368-374.
Abstract:
After reaction of the silicane coupling agent with the hydroxyl on the surface of graphite nanoplatelets(GNPs), polymethyl methacrylate (PMMA) was chemically grafted to the GNPs by using atom transfer radical polymerization(ATRP). The microstructure change of raw GNPs and grafted GNPs was investigated by SEM, TEM, FTIR and XRD. The grafted GNPs were added into the epoxy resin, and the mechanical properties and dimensional stability of GNPs-PMMA/epoxy composites were studied. The PMMA grafted GNPs show better reinforcing effect on the mechanical properties of epoxy resin in contrast with raw GNPs. The tensile strength and modulus of epoxy resin increase by 17.4% and 75% respectively after being added 0.5 wt% GNPs-PMMA. At the same time, the bending strength and modulus of epoxy resin exhibit enhancement of 6% and 12%, respectively. And the linear coefficient of thermal expansion (CTE) of epoxy resin declines by 25% below the glass transition temperature.
After reaction of the silicane coupling agent with the hydroxyl on the surface of graphite nanoplatelets(GNPs), polymethyl methacrylate (PMMA) was chemically grafted to the GNPs by using atom transfer radical polymerization(ATRP). The microstructure change of raw GNPs and grafted GNPs was investigated by SEM, TEM, FTIR and XRD. The grafted GNPs were added into the epoxy resin, and the mechanical properties and dimensional stability of GNPs-PMMA/epoxy composites were studied. The PMMA grafted GNPs show better reinforcing effect on the mechanical properties of epoxy resin in contrast with raw GNPs. The tensile strength and modulus of epoxy resin increase by 17.4% and 75% respectively after being added 0.5 wt% GNPs-PMMA. At the same time, the bending strength and modulus of epoxy resin exhibit enhancement of 6% and 12%, respectively. And the linear coefficient of thermal expansion (CTE) of epoxy resin declines by 25% below the glass transition temperature.
2014, 31(2): 375-382.
Abstract:
IsoTruss is a new ultra-lightweight composite structure, combining the advantage of lightweight material and structure. The structural features of IsoTruss were analyzed and the manufacturing process was summarized in this paper. Based on the structural features of IsoTruss, a flexible mandrel was designed and manufactured. 8-node single IsoTruss specimens were filament wound using the flexible mandrel and IsoTruss members were consolidated with aramid fiber. The compression test, bending test and torsion test were carried out to evaluate mechanical properties of IsoTruss specimens. The results of the compression test show that the average stiffness-to-mass ratio is 1 944.8 (kN/mm)/kg, and the average strength-to-mass ratio is 833.8 kN/kg, which achieve the performance of this type of composite structures and are higher than composite grid structures. Furthermore, the test results also indicate that the flexible mandrel, cooperated with consolidation using aramid fibre, can fabricate IsoTruss structures with high mechanical properties.
IsoTruss is a new ultra-lightweight composite structure, combining the advantage of lightweight material and structure. The structural features of IsoTruss were analyzed and the manufacturing process was summarized in this paper. Based on the structural features of IsoTruss, a flexible mandrel was designed and manufactured. 8-node single IsoTruss specimens were filament wound using the flexible mandrel and IsoTruss members were consolidated with aramid fiber. The compression test, bending test and torsion test were carried out to evaluate mechanical properties of IsoTruss specimens. The results of the compression test show that the average stiffness-to-mass ratio is 1 944.8 (kN/mm)/kg, and the average strength-to-mass ratio is 833.8 kN/kg, which achieve the performance of this type of composite structures and are higher than composite grid structures. Furthermore, the test results also indicate that the flexible mandrel, cooperated with consolidation using aramid fibre, can fabricate IsoTruss structures with high mechanical properties.
2014, 31(2): 383-387.
Abstract:
The graphite felt (GF) was pretreated with H2O2, and then Sn was electrodeposited on pretreated GF. At last, the SnO2 modified GF was obtained by oxidation of Sn at 120℃ for 24 h. The morphologies of GF before and after modified by SnO2 were characterized by SEM, and the electrochemical properties of GF modified by SnO2 were investigated by cyclic voltammogram. The results show that the SnO2 coating is uniformly formed on the surface of GF. The oxidation peak current increases from 0.053 8 A to 0.070 8 A, which means 31.5% improves before and after SnO2 modification of GF. The duration time of oxidation enhances after SnO2 modified, which indicates that SnO2 performs a catalytic action upon the reaction of vanadium ions. In addition, the potential of oxygen evolution increases from 1.382 V to 1.517 V. Therefore, the electrochemical window of GF electrode in VOSO4 solution is widened by modification of SnO2.
The graphite felt (GF) was pretreated with H2O2, and then Sn was electrodeposited on pretreated GF. At last, the SnO2 modified GF was obtained by oxidation of Sn at 120℃ for 24 h. The morphologies of GF before and after modified by SnO2 were characterized by SEM, and the electrochemical properties of GF modified by SnO2 were investigated by cyclic voltammogram. The results show that the SnO2 coating is uniformly formed on the surface of GF. The oxidation peak current increases from 0.053 8 A to 0.070 8 A, which means 31.5% improves before and after SnO2 modification of GF. The duration time of oxidation enhances after SnO2 modified, which indicates that SnO2 performs a catalytic action upon the reaction of vanadium ions. In addition, the potential of oxygen evolution increases from 1.382 V to 1.517 V. Therefore, the electrochemical window of GF electrode in VOSO4 solution is widened by modification of SnO2.
2014, 31(2): 388-395.
Abstract:
The four kinds of 5 μm SiCP/Mg alloy (AZ91) magnesium matrix composite with the volume fraction of 2%, 5%, 10% and 15%, respectively, were fabricated by stir casting. After the solution treatment, forging and hot extrusion, the effect of SiCP on the microstructure and mechanical properties of AZ91 matrix were investigated by compared with the monolithic AZ91 alloy. The results show that the grain size of SiCP/AZ91 depends on the volume fraction of SiCP. The average grain size of composite matrix decreases as the volume fraction increased from 0% to 10%, the grain size increases as SiCP volume fraction continuing increased to 15%. The addition of SiCP can improve the yield strength and modulus of AZ91 significantly, and they increase with the volume fraction of SiCP. The strengthening effects of SiCP on AZ91 matrix are mainly attributed to dislocation strengthening mechanism, grain refinement and load transfer effect, the grain refinement plays a main role on improving the yield strength.
The four kinds of 5 μm SiCP/Mg alloy (AZ91) magnesium matrix composite with the volume fraction of 2%, 5%, 10% and 15%, respectively, were fabricated by stir casting. After the solution treatment, forging and hot extrusion, the effect of SiCP on the microstructure and mechanical properties of AZ91 matrix were investigated by compared with the monolithic AZ91 alloy. The results show that the grain size of SiCP/AZ91 depends on the volume fraction of SiCP. The average grain size of composite matrix decreases as the volume fraction increased from 0% to 10%, the grain size increases as SiCP volume fraction continuing increased to 15%. The addition of SiCP can improve the yield strength and modulus of AZ91 significantly, and they increase with the volume fraction of SiCP. The strengthening effects of SiCP on AZ91 matrix are mainly attributed to dislocation strengthening mechanism, grain refinement and load transfer effect, the grain refinement plays a main role on improving the yield strength.
2014, 31(2): 396-401.
Abstract:
BaSrZnSi2O7-Ba0.5Sr0.5TiO3 composite ceramics were systematically characterized in terms of phase composition, microstructure and dielectric properties. It is found that dielectric permittivity peaks of the samples shifted to low temperatures initially and then kept invariable with increasing BaSrZnSi2O7content. Tunability showed a similar trend to Curie temperature. The variety in Q value is mainly related to whether the ‘doping’ effect or ‘composite’ effect is dominated. The sample with 60wt% of BaSrZnSi2O7 possess a high tunability of 16%(10 kHz), a low dielectric permittivity of 152 and a high Q value of 417 (2.720 GHz), making it a promising candidate for applications as electrically tunable microwave devices.
BaSrZnSi2O7-Ba0.5Sr0.5TiO3 composite ceramics were systematically characterized in terms of phase composition, microstructure and dielectric properties. It is found that dielectric permittivity peaks of the samples shifted to low temperatures initially and then kept invariable with increasing BaSrZnSi2O7content. Tunability showed a similar trend to Curie temperature. The variety in Q value is mainly related to whether the ‘doping’ effect or ‘composite’ effect is dominated. The sample with 60wt% of BaSrZnSi2O7 possess a high tunability of 16%(10 kHz), a low dielectric permittivity of 152 and a high Q value of 417 (2.720 GHz), making it a promising candidate for applications as electrically tunable microwave devices.
2014, 31(2): 402-407.
Abstract:
Core-shell structure Ag-SiO2-CeF3:Tb3+ composite luminescent nanoparticles are fabricated via a simple liquid method at room temperature, the structure and properties are characterized. The results show that orthogonal phase CeF3:Tb3+ nanocrystals are coated on the surface of Ag-SiO2. The obtained Ag-SiO2-CeF3:Tb3+composites have spherical morphology, the size is about 45-60 nm, and the surface is tough. Their photoluminescence properties show to be the same as those of the pure CeF3:Tb3+, and the strong emission peak is near 544 nm which is corresponding to 5D4→7F5 transition of Tb3+, Ag core quenches the luminescence of CeF3:Tb3+. This functional Ag-SiO2-CeF3:Tb3+composites would be potentially applied in biology detection and disease therapy fields.
Core-shell structure Ag-SiO2-CeF3:Tb3+ composite luminescent nanoparticles are fabricated via a simple liquid method at room temperature, the structure and properties are characterized. The results show that orthogonal phase CeF3:Tb3+ nanocrystals are coated on the surface of Ag-SiO2. The obtained Ag-SiO2-CeF3:Tb3+composites have spherical morphology, the size is about 45-60 nm, and the surface is tough. Their photoluminescence properties show to be the same as those of the pure CeF3:Tb3+, and the strong emission peak is near 544 nm which is corresponding to 5D4→7F5 transition of Tb3+, Ag core quenches the luminescence of CeF3:Tb3+. This functional Ag-SiO2-CeF3:Tb3+composites would be potentially applied in biology detection and disease therapy fields.
2014, 31(2): 408-415.
Abstract:
A type of novel iron oxide-based porous ceramsite (IPC) was prepared using goethite, sawdust and palygorskite as raw material. As-prepared IPC was proved to meet the national standard of water treatment. In various propriety tests for the ceramsite, the compressive strength was the principal factor to determine the most suitable product. An orthogonal experiment design in the optimization of mass ratio of raw materials and processing technology for IPC was introduced. XRD, SEM, polarizing microscope (PM) and specific surface area (BET-SSA) were used to characterize IPC. The results indicate that IPC has a porosity between 10-20 μm as well as 51-78 N of the compressive strength respectively. IPC owns large specific surface area (79 m2/g) and interconnects pores.The micro-organisms growth experimental results also show that in the same submerged culture conditions, the biological load in IPC is significantly higher than the commercially available ceramic and particle zeolite. The ceramisite is suitable to serve as the novel functional filler in biological aerated filter.
A type of novel iron oxide-based porous ceramsite (IPC) was prepared using goethite, sawdust and palygorskite as raw material. As-prepared IPC was proved to meet the national standard of water treatment. In various propriety tests for the ceramsite, the compressive strength was the principal factor to determine the most suitable product. An orthogonal experiment design in the optimization of mass ratio of raw materials and processing technology for IPC was introduced. XRD, SEM, polarizing microscope (PM) and specific surface area (BET-SSA) were used to characterize IPC. The results indicate that IPC has a porosity between 10-20 μm as well as 51-78 N of the compressive strength respectively. IPC owns large specific surface area (79 m2/g) and interconnects pores.The micro-organisms growth experimental results also show that in the same submerged culture conditions, the biological load in IPC is significantly higher than the commercially available ceramic and particle zeolite. The ceramisite is suitable to serve as the novel functional filler in biological aerated filter.
2014, 31(2): 416-422.
Abstract:
The rheological behaviors of the ZrO2/Al2O3 (ZTA) suspension were investigated using three kinds of Al2O3 with different particle morphology. ZrO2/Al2O3 green bodies and ceramics were prepared by using a low-toxicity monomer N,N-dimethyl acrylamide (DMAA) as gelling agent. The effect of dispersant dosage, milling time and solid loading on the rheological properties of suspension were discussed. Tabular Al2O3 powders have good effect on decreasing viscosity of slurries and clubbed Al2O3 powders are good for flexural strength of green bodies. The particles in ZrO2/Al2O3 green bodies are combined closely and their bending strength can reach 21.45, 19.87, 25.90 MPa, respectively. Granular Al2O3 powders are beneficial properties of sintered ceramics, and the mean bending strength and fracture toughness of sintered ceramics are 680 MPa and 7.49 MPa·m1/2, 453.1 MPa and 6.8 MPa·m1/2, 549.4 MPa and 6.34 MPa·m1/2.
The rheological behaviors of the ZrO2/Al2O3 (ZTA) suspension were investigated using three kinds of Al2O3 with different particle morphology. ZrO2/Al2O3 green bodies and ceramics were prepared by using a low-toxicity monomer N,N-dimethyl acrylamide (DMAA) as gelling agent. The effect of dispersant dosage, milling time and solid loading on the rheological properties of suspension were discussed. Tabular Al2O3 powders have good effect on decreasing viscosity of slurries and clubbed Al2O3 powders are good for flexural strength of green bodies. The particles in ZrO2/Al2O3 green bodies are combined closely and their bending strength can reach 21.45, 19.87, 25.90 MPa, respectively. Granular Al2O3 powders are beneficial properties of sintered ceramics, and the mean bending strength and fracture toughness of sintered ceramics are 680 MPa and 7.49 MPa·m1/2, 453.1 MPa and 6.8 MPa·m1/2, 549.4 MPa and 6.34 MPa·m1/2.
2014, 31(2): 423-428.
Abstract:
V-N co-doped TiO2/attapulgite photocatalytic composite materials were synthesized by slo-gel method, preparation method, V-N-TiO2 and attapulgite of mass ratio, calcination temperature and time of V-N-TiO2/attapulgite on photocatalytic properties were studied. On the condition of simulative sunlight, photocatalytic properties of V-N-TiO2/attapulgite were measured by using methylene blue as evaluation standards. Research shows that when mass ratio of TiO2 to attapulgite is 1：3, calcination temperature is 300℃ and calcination time is 2 h, the best performance properties of V-N-TiO2/attapulgite photocatalytic composite materials to methylene blue is obtained.
V-N co-doped TiO2/attapulgite photocatalytic composite materials were synthesized by slo-gel method, preparation method, V-N-TiO2 and attapulgite of mass ratio, calcination temperature and time of V-N-TiO2/attapulgite on photocatalytic properties were studied. On the condition of simulative sunlight, photocatalytic properties of V-N-TiO2/attapulgite were measured by using methylene blue as evaluation standards. Research shows that when mass ratio of TiO2 to attapulgite is 1：3, calcination temperature is 300℃ and calcination time is 2 h, the best performance properties of V-N-TiO2/attapulgite photocatalytic composite materials to methylene blue is obtained.
2014, 31(2): 429-435.
Abstract:
The multi-walled carbon nanotubes (MWCNTs) were acidified by mixed acid, then the MWCNTs coated with TiO2 (TiO2-MWCNTs) hybrid material were prepared by sol-gel method, and the results were verified by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The silane coupling agent KH560 was used to modify the TiO2-MWCNTs and MWCNTs, and the composite coating of TiO2-MWCNTs/epoxy resin, MWCNTs/epoxy resin and the pure epoxy coating was prepared respectively. The electrical properties machine flexibility of composite coatings were tested through EIS and material test system (MTS). Scanning electron microscope (SEM) was used to observe the coatings surface condition. The results show that TiO2-MWCNTs disperse good in the epoxy resin, TiO2-MWCNTs/epoxy composite coating in the corrosion medium has good resistance to permeation, and the flexibility of coating is increased greatly after coated by TiO2.
The multi-walled carbon nanotubes (MWCNTs) were acidified by mixed acid, then the MWCNTs coated with TiO2 (TiO2-MWCNTs) hybrid material were prepared by sol-gel method, and the results were verified by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The silane coupling agent KH560 was used to modify the TiO2-MWCNTs and MWCNTs, and the composite coating of TiO2-MWCNTs/epoxy resin, MWCNTs/epoxy resin and the pure epoxy coating was prepared respectively. The electrical properties machine flexibility of composite coatings were tested through EIS and material test system (MTS). Scanning electron microscope (SEM) was used to observe the coatings surface condition. The results show that TiO2-MWCNTs disperse good in the epoxy resin, TiO2-MWCNTs/epoxy composite coating in the corrosion medium has good resistance to permeation, and the flexibility of coating is increased greatly after coated by TiO2.
2014, 31(2): 436-440.
Abstract:
Al-Sm2O3/polyurethane (PU) composite coatings were prepared through a simple and convenient process by using Al-Sm2O3 as the pigments and PU as the adhesives. The microstructure, infrared emissivity, near-infrared reflective properties and mechanical properties of as-prepared coatings were systematically investigated. The results indicate that the existence of Sm2O3 in the coatings can obviously decrease the near-infrared light reflectivity at 1.06 μm, the existence of Al powders in the coatings can effectively reduce the infrared emissivity at the wavelength of 8 μm to 14 μm. By adjusting the mass ratio of Al-Sm2O3, the infrared emissivity at the wavelength of 8 μm to 14 μm can be tuned from 0.556 to 0.834, and the reflectivity at 1.06 μm can be tuned from 35.1% to 57.7%. The coatings can present good mechanical properties, the adhesion strength and impact strength of the coatings with different mass ratios of Al-Sm2O3can reach 1 grade and 50 kg·cm, respectively. Al-Sm2O3/PU composite coatings seem to be a novel low infrared emissivity material with low near-infrared light reflectivity and good mechanical properties.
Al-Sm2O3/polyurethane (PU) composite coatings were prepared through a simple and convenient process by using Al-Sm2O3 as the pigments and PU as the adhesives. The microstructure, infrared emissivity, near-infrared reflective properties and mechanical properties of as-prepared coatings were systematically investigated. The results indicate that the existence of Sm2O3 in the coatings can obviously decrease the near-infrared light reflectivity at 1.06 μm, the existence of Al powders in the coatings can effectively reduce the infrared emissivity at the wavelength of 8 μm to 14 μm. By adjusting the mass ratio of Al-Sm2O3, the infrared emissivity at the wavelength of 8 μm to 14 μm can be tuned from 0.556 to 0.834, and the reflectivity at 1.06 μm can be tuned from 35.1% to 57.7%. The coatings can present good mechanical properties, the adhesion strength and impact strength of the coatings with different mass ratios of Al-Sm2O3can reach 1 grade and 50 kg·cm, respectively. Al-Sm2O3/PU composite coatings seem to be a novel low infrared emissivity material with low near-infrared light reflectivity and good mechanical properties.
2014, 31(2): 441-447.
Abstract:
The nano-palygorskite/copper (nano-P/Cu)composites were prepared by liquid chemical reduction method and mechanical ball milling. The size and morphology of the nanoparticles were described by means of transmission electron microscopy(TEM) and particle size analyzer. The tribological properties of nano-P/Cu powders, in different mass fraction and component proportion, as 150 N base oil additive, were evaluated on a four ball friction and wear tester. The morphologies, element distributions and micromechanical properties of the worn surface were investigated by means of scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS). The results indicate that almost all particle size of nano-P/Cu is less than 100 nm and the lubricant oil with nano-P/Cu additives is good in dispersion effect and stable. For steel ball tribopair, the tribological properties are best while the component mass ratio and content of nano-P/Cu composites is P:Cu=3:1 and 1wt% respectively. The wear scar diameter of sample lubricated with nano-P/Cu additive decreases 20.7% compared with the none additive. It can be deduced that an auto-restoration film composed of Mg, Al, Si and Cu elements forms on the worn surface to compensate the wear loss and make the surface smoother.
The nano-palygorskite/copper (nano-P/Cu)composites were prepared by liquid chemical reduction method and mechanical ball milling. The size and morphology of the nanoparticles were described by means of transmission electron microscopy(TEM) and particle size analyzer. The tribological properties of nano-P/Cu powders, in different mass fraction and component proportion, as 150 N base oil additive, were evaluated on a four ball friction and wear tester. The morphologies, element distributions and micromechanical properties of the worn surface were investigated by means of scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS). The results indicate that almost all particle size of nano-P/Cu is less than 100 nm and the lubricant oil with nano-P/Cu additives is good in dispersion effect and stable. For steel ball tribopair, the tribological properties are best while the component mass ratio and content of nano-P/Cu composites is P:Cu=3:1 and 1wt% respectively. The wear scar diameter of sample lubricated with nano-P/Cu additive decreases 20.7% compared with the none additive. It can be deduced that an auto-restoration film composed of Mg, Al, Si and Cu elements forms on the worn surface to compensate the wear loss and make the surface smoother.
2014, 31(2): 448-455.
Abstract:
According to the smallest net section's picture of 2D-C/SiC composite laminates with circular hole, the macroscopic pores distribution and the gradient of loco-regional material density inside of specimen were obtained. The tensile stress-strain behavior of 2D-C/SiC composite laminates was fitted by nonlinear curve, and the material density's influence on initial tensile module and tensile strength also was investigated by associating theoretical model simulation with experimental verification. The tensile nonlinear stress-strain behavior of 2D-C/SiC composite with different density were described successfully. The mechanics analytical finite element model was built by taking the material density inhomogeneity in the specimen internal into account, and the material tensile nonlinear stress-strain behavior also varies with its density. The prediction in the net section tensile strength values of open-hole specimen go along well with the experimental results.
According to the smallest net section's picture of 2D-C/SiC composite laminates with circular hole, the macroscopic pores distribution and the gradient of loco-regional material density inside of specimen were obtained. The tensile stress-strain behavior of 2D-C/SiC composite laminates was fitted by nonlinear curve, and the material density's influence on initial tensile module and tensile strength also was investigated by associating theoretical model simulation with experimental verification. The tensile nonlinear stress-strain behavior of 2D-C/SiC composite with different density were described successfully. The mechanics analytical finite element model was built by taking the material density inhomogeneity in the specimen internal into account, and the material tensile nonlinear stress-strain behavior also varies with its density. The prediction in the net section tensile strength values of open-hole specimen go along well with the experimental results.
2014, 31(2): 456-464.
Abstract:
A novel type of glass fiber reinforced polymer (GFRP) sandwich structure with an improved chevron folded core was obtained through hot-press molding method. The mechanical response and failure mechanism of this structure under compression loading were investigated with FEM simulation and experiment, the process of damage evolution were described with inducing the fiber crushing model, and the obtained stress-strain curves with simulation and experiment are fitted well. Results show that the variation of relative density of structure not only affects the mechanical performance, but also leads the fracture mode changing.
A novel type of glass fiber reinforced polymer (GFRP) sandwich structure with an improved chevron folded core was obtained through hot-press molding method. The mechanical response and failure mechanism of this structure under compression loading were investigated with FEM simulation and experiment, the process of damage evolution were described with inducing the fiber crushing model, and the obtained stress-strain curves with simulation and experiment are fitted well. Results show that the variation of relative density of structure not only affects the mechanical performance, but also leads the fracture mode changing.
2014, 31(2): 465-475.
Abstract:
Composite laminate modeling based on lamination parameters was fulfilled and the parameter input problem of lamination parameters with Nastran was solved. Also, the feasible region of lamination parameters was derived and supplemented with rule of minimum amount of fibers. With the two aspects, an optimization method for composite aeroelastic tailoring based on lamination parameters and Nastran was proposed. First, laminate thickness and lamination parameters were as design variables, with constraints of lamination parameters constraints and structure behavior constraints including strength, stiffness, flutter speed and divergence speed constraints. Second, the inverse problem of optimal lamination parameters to real laminate configuration was solved as a discrete numerical optimization problem just with constraints of composite manufacturing constraints. Because the lamination parameters were functions of laminate thickness and stacking sequence, the optimization method with lamination parameters as design variables could obtain larger design freedom compared with the conventional method with layer thicknesses as design variables. Finally, a cantilever plate numerical example with aeroelastic constraints was used to demonstrate the efficiency of the proposed method. Results show that the optimal laminate configuration obtained by the proposed method satisfies the manufacturing constraints with lighter mass.
Composite laminate modeling based on lamination parameters was fulfilled and the parameter input problem of lamination parameters with Nastran was solved. Also, the feasible region of lamination parameters was derived and supplemented with rule of minimum amount of fibers. With the two aspects, an optimization method for composite aeroelastic tailoring based on lamination parameters and Nastran was proposed. First, laminate thickness and lamination parameters were as design variables, with constraints of lamination parameters constraints and structure behavior constraints including strength, stiffness, flutter speed and divergence speed constraints. Second, the inverse problem of optimal lamination parameters to real laminate configuration was solved as a discrete numerical optimization problem just with constraints of composite manufacturing constraints. Because the lamination parameters were functions of laminate thickness and stacking sequence, the optimization method with lamination parameters as design variables could obtain larger design freedom compared with the conventional method with layer thicknesses as design variables. Finally, a cantilever plate numerical example with aeroelastic constraints was used to demonstrate the efficiency of the proposed method. Results show that the optimal laminate configuration obtained by the proposed method satisfies the manufacturing constraints with lighter mass.
2014, 31(2): 476-484.
Abstract:
Due to the difficulties of the traditional reliability design in meeting modern design requirements, it was necessary to have a robustness optimization design to improve comprehensive reliability of the cabin. The reliability of composite monolayer was solved on the basis of two failure modes of matrix damage and fiber breakage by adopting the design point method. The idea of taking the structure as parallel systems that were constituted by series subsystems was put forward based on the hypothesis of the last layer failure. The main failure sequences can be figured out through combining the material stiffness ratio degradation criterion with monolayer reliability theory, and adopting the probability gradually failure analysis method, then the failure probability of structure can be worked out. Due to the complexity of design variable space of composite cabin, the idea of two-level optimization method was put forward. The first level was system-level layout optimization, which optimized some parameters, including profile shape of stiffener rib, the parameters of position, etc. The second level was subsystem-level size optimization, which optimized some parameters, including sectional dimensions of stiffener rib, each layer's thickness of composite, etc. Regarding the minimum mass of composite cabin as the objective function and the requirements of reliability as the constraint condition, the composite cabin with initial imperfection can be optimized by means of employing the genetic algorithm of self-adaption random search and coordinative optimization method of robustness. The method of optimization can provide references for optimization and design of composite structure.
Due to the difficulties of the traditional reliability design in meeting modern design requirements, it was necessary to have a robustness optimization design to improve comprehensive reliability of the cabin. The reliability of composite monolayer was solved on the basis of two failure modes of matrix damage and fiber breakage by adopting the design point method. The idea of taking the structure as parallel systems that were constituted by series subsystems was put forward based on the hypothesis of the last layer failure. The main failure sequences can be figured out through combining the material stiffness ratio degradation criterion with monolayer reliability theory, and adopting the probability gradually failure analysis method, then the failure probability of structure can be worked out. Due to the complexity of design variable space of composite cabin, the idea of two-level optimization method was put forward. The first level was system-level layout optimization, which optimized some parameters, including profile shape of stiffener rib, the parameters of position, etc. The second level was subsystem-level size optimization, which optimized some parameters, including sectional dimensions of stiffener rib, each layer's thickness of composite, etc. Regarding the minimum mass of composite cabin as the objective function and the requirements of reliability as the constraint condition, the composite cabin with initial imperfection can be optimized by means of employing the genetic algorithm of self-adaption random search and coordinative optimization method of robustness. The method of optimization can provide references for optimization and design of composite structure.
2014, 31(2): 485-494.
Abstract:
The low-velocity impact and compression after impact performances of composite laminates with a surface protection layer was experimentally investigated. Through drop-weight low-velocity impact tests, impact force histories, indentation depths and delamination areas inside the laminates were obtained. The damage tolerance performances for the groups of laminates can be evaluated through compression after impact tests. The test results show that the delamination initiation loads for the laminates with a surface protection layer are nearly the same with the bare laminates, while the impact energies required to generate an indentation with a depth of 1.0 mm are 24%-46% larger. Under the same impact energy, the C-scan delamination areas of the laminates with a surface protection layer are around 20%-50% smaller than the bare laminates. However, at the same indentation depth, the C-scan delamination areas do not change much when adding the surface protection layer to the laminates. The compression after impact (CAI) performances are in close relation to the delamination inside the laminates. Under the same impact energy, the CAI strength and failure strain are 15%-50% greater for the laminates with a surface protection layer which have smaller delamination areas compared with the bare laminates. At the same indentation depth, the CAI strength and failure strain do not appear to be much different for both the bare laminates and those with a surface protection layer.
The low-velocity impact and compression after impact performances of composite laminates with a surface protection layer was experimentally investigated. Through drop-weight low-velocity impact tests, impact force histories, indentation depths and delamination areas inside the laminates were obtained. The damage tolerance performances for the groups of laminates can be evaluated through compression after impact tests. The test results show that the delamination initiation loads for the laminates with a surface protection layer are nearly the same with the bare laminates, while the impact energies required to generate an indentation with a depth of 1.0 mm are 24%-46% larger. Under the same impact energy, the C-scan delamination areas of the laminates with a surface protection layer are around 20%-50% smaller than the bare laminates. However, at the same indentation depth, the C-scan delamination areas do not change much when adding the surface protection layer to the laminates. The compression after impact (CAI) performances are in close relation to the delamination inside the laminates. Under the same impact energy, the CAI strength and failure strain are 15%-50% greater for the laminates with a surface protection layer which have smaller delamination areas compared with the bare laminates. At the same indentation depth, the CAI strength and failure strain do not appear to be much different for both the bare laminates and those with a surface protection layer.
2014, 31(2): 495-504.
Abstract:
A hierarchical honeycomb material with soft adhesion layer being added to its walls was studied based on hexagonal honeycomb, Kagome honeycomb and triangular honeycomb. Using analytical calculation and numerical simulation method, the bulk modulus and shear modulus of hierarchical structure honeycomb with missing walls were given out. It presents that hierarchical structure honeycomb shows a low level of imperfection sensitivities compared with classic honeycomb. When the adhesion layer has the same specific modulus and twice the thickness of the core layer's but an order of magnitude lower modulus than the core layer's, the hexagonal honeycomb and Kagome honeycomb's imperfection sensitivities are significantly reduced.
A hierarchical honeycomb material with soft adhesion layer being added to its walls was studied based on hexagonal honeycomb, Kagome honeycomb and triangular honeycomb. Using analytical calculation and numerical simulation method, the bulk modulus and shear modulus of hierarchical structure honeycomb with missing walls were given out. It presents that hierarchical structure honeycomb shows a low level of imperfection sensitivities compared with classic honeycomb. When the adhesion layer has the same specific modulus and twice the thickness of the core layer's but an order of magnitude lower modulus than the core layer's, the hexagonal honeycomb and Kagome honeycomb's imperfection sensitivities are significantly reduced.
2014, 31(2): 505-511.
Abstract:
The steady and transient state heat transfer across the FRP honeycomb panel was investigated by the simulation of finite element method on the basis of ANSYS. In consistent with the real experimental condition,the coupling heat plane model of fluid and solid of the FRP honeycomb panel was built. The steady thermal performance was investigated for different honeycomb heights,the research indicates that simulation results of the steady thermal performance are identical with the calculation results of the Swann & Pittman empirical formula. Furthermore,the simulation results of transient facial thermal response are also quite identical with the experimental results. The results indicate that the finite element soft of ANSYS could correctly simulation the heat transfer of the FRP honeycomb panel. In addition,the radiation heat transfer between the inner faces is one of the important mechanism of heat transfer,and coupling heat transfer of the radiation and conductivity should be considered in the condition of high temperature. The thermal conductivity of the FRP honeycomb panel gradually increases along with the increasing honeycomb core height. In the condition of fixed honeycomb core height,the thermal conductivity of the FRP honeycomb panel gradually decreases along with the increasing honeycomb core layers,and the temperature of the FRP honeycomb panel is trend to fixed value along with the increasing honeycomb core layers.
The steady and transient state heat transfer across the FRP honeycomb panel was investigated by the simulation of finite element method on the basis of ANSYS. In consistent with the real experimental condition,the coupling heat plane model of fluid and solid of the FRP honeycomb panel was built. The steady thermal performance was investigated for different honeycomb heights,the research indicates that simulation results of the steady thermal performance are identical with the calculation results of the Swann & Pittman empirical formula. Furthermore,the simulation results of transient facial thermal response are also quite identical with the experimental results. The results indicate that the finite element soft of ANSYS could correctly simulation the heat transfer of the FRP honeycomb panel. In addition,the radiation heat transfer between the inner faces is one of the important mechanism of heat transfer,and coupling heat transfer of the radiation and conductivity should be considered in the condition of high temperature. The thermal conductivity of the FRP honeycomb panel gradually increases along with the increasing honeycomb core height. In the condition of fixed honeycomb core height,the thermal conductivity of the FRP honeycomb panel gradually decreases along with the increasing honeycomb core layers,and the temperature of the FRP honeycomb panel is trend to fixed value along with the increasing honeycomb core layers.
2014, 31(2): 512-517.
Abstract:
During the preparation of biologic foam materials using starch and ethylene-vinyl acetate copolymer(EVA) as raw material to prepare the starch/EVA biologic materials, the influences of screw speed, die temperature and moisture content on extrusion foaming have been studied, and the double-layer BP network model based on artificial neural network technique has been built. The orthogonal experiment result has been used as samples to train and forecast the expansibility of biologic foam materials. The results show that this BP network model is effective to forecast expansibility of the starch/EVA biologic materials accurately, and the expansibility gradually increases with the increase of screw speed. When the screw speed is 320 r/min, expansibility reaches its maximum. The expansibility also increases with the rising of die temperature and reaches its maximum at 140℃. Moisture content also has significant influence on the expansibility of the starch/EVA foam materials.
During the preparation of biologic foam materials using starch and ethylene-vinyl acetate copolymer(EVA) as raw material to prepare the starch/EVA biologic materials, the influences of screw speed, die temperature and moisture content on extrusion foaming have been studied, and the double-layer BP network model based on artificial neural network technique has been built. The orthogonal experiment result has been used as samples to train and forecast the expansibility of biologic foam materials. The results show that this BP network model is effective to forecast expansibility of the starch/EVA biologic materials accurately, and the expansibility gradually increases with the increase of screw speed. When the screw speed is 320 r/min, expansibility reaches its maximum. The expansibility also increases with the rising of die temperature and reaches its maximum at 140℃. Moisture content also has significant influence on the expansibility of the starch/EVA foam materials.
2014, 31(2): 518-524.
Abstract:
The self-emulsifying hydroxyethyl methylacrylate modified waterborne polyurethane (AWPU) emulsion was prepared and mixed with epoxy (EP) emulsion. Infrared, differential scanning calorimetry and thermogravimetry were used to characterize the chemical reaction and thermal properties occurred in the process of sizing of AWPU, EP, AWPU-EP emulsions. The results show that when temperature is below 300℃, the thermal mass loss of AWPU-EP composite emulsion is between those of AWPU and EP emulsion; when temperature is above 350℃, a good thermal property is obtained. The maximum mass loss rate temperature is increased from 312.8℃ of EP emulsion and 321.6℃ of AWPU emulsion to 410.2℃. When gluing carbon fiber with AWPU mass fraction of 20% and 80% in AWPU-EP composite emulsion, carbon fiber will show superior cluster of carbon fiber and its antiwear is better than that with EP emulsion.
The self-emulsifying hydroxyethyl methylacrylate modified waterborne polyurethane (AWPU) emulsion was prepared and mixed with epoxy (EP) emulsion. Infrared, differential scanning calorimetry and thermogravimetry were used to characterize the chemical reaction and thermal properties occurred in the process of sizing of AWPU, EP, AWPU-EP emulsions. The results show that when temperature is below 300℃, the thermal mass loss of AWPU-EP composite emulsion is between those of AWPU and EP emulsion; when temperature is above 350℃, a good thermal property is obtained. The maximum mass loss rate temperature is increased from 312.8℃ of EP emulsion and 321.6℃ of AWPU emulsion to 410.2℃. When gluing carbon fiber with AWPU mass fraction of 20% and 80% in AWPU-EP composite emulsion, carbon fiber will show superior cluster of carbon fiber and its antiwear is better than that with EP emulsion.
2014, 31(2): 525-531.
Abstract:
The macroporous conducting C/SiO2 composite electrode was prepared in-situ polymerization and vacuum pyrolysis in a novel SiO2 macroporous template, followed by loading the elemental sulfur and the polymer film on the channel surface to obtain the Polymer-S-C/SiO2 composite macroporous electrode with multilayer structure. The structures of Polymer-S-C/SiO2 electrodes were characterized by SEM, and the specific surface area and average thickness of loads were also measured. The electrochemical performances were studied by electrochemical charge-discharge experiments and impedance spectroscopy. The results show that the alternating current impedance of electrode increases rapidly and the reverse cycle performance of lithium ion batteries are improved obviously when the thickness of the polymer film increases, which shows that the existence of the polymer film can effectively inhibit the loss of polysulfide intermediate. The thickness of the polymer film can be adjusted by changing the dosage of the monomer. When the average thickness of the polymer film is 8.0 nm, the lithium ion battery exhibits the first discharge specific capacity of 792 mA·h/g, and it remains 635 mA·h/g after 50 cycles, which shows the best effects.
The macroporous conducting C/SiO2 composite electrode was prepared in-situ polymerization and vacuum pyrolysis in a novel SiO2 macroporous template, followed by loading the elemental sulfur and the polymer film on the channel surface to obtain the Polymer-S-C/SiO2 composite macroporous electrode with multilayer structure. The structures of Polymer-S-C/SiO2 electrodes were characterized by SEM, and the specific surface area and average thickness of loads were also measured. The electrochemical performances were studied by electrochemical charge-discharge experiments and impedance spectroscopy. The results show that the alternating current impedance of electrode increases rapidly and the reverse cycle performance of lithium ion batteries are improved obviously when the thickness of the polymer film increases, which shows that the existence of the polymer film can effectively inhibit the loss of polysulfide intermediate. The thickness of the polymer film can be adjusted by changing the dosage of the monomer. When the average thickness of the polymer film is 8.0 nm, the lithium ion battery exhibits the first discharge specific capacity of 792 mA·h/g, and it remains 635 mA·h/g after 50 cycles, which shows the best effects.
