2011 Vol. 28, No. 6
2011, 28(6): 1-7.
doi: CNKI:11-1801/TB.20110720.1334.003
Abstract:
The compressibility of fabric preforms in vacuum infusion molding process (VIMP) was studied by loading vacuum pressure. The effects of cyclic loading, fabric form, fiber type, number of layers, way of layup and hybrid mode on the compressibility were investigated. The results show that the fiber volume fraction increases with the times of cyclic loading, while the growth value decreases. The growth value of fiber volume fraction slightly increases with the number of layers under the same vacuum pressure that it almost can be neglected in vacuum infusion molding process(VIMP). The way of layup, fabric form, fiber type and hybrid mode have remarkable effects on the compressibility of fabric preforms. The undirectional layup results in a higher fiber volume fraction than the orthogonal layup under the same compaction pressure, and the higher fiber volume faction can be achieved in the core hybrid composite compared with that in the interply hybrid composite.
The compressibility of fabric preforms in vacuum infusion molding process (VIMP) was studied by loading vacuum pressure. The effects of cyclic loading, fabric form, fiber type, number of layers, way of layup and hybrid mode on the compressibility were investigated. The results show that the fiber volume fraction increases with the times of cyclic loading, while the growth value decreases. The growth value of fiber volume fraction slightly increases with the number of layers under the same vacuum pressure that it almost can be neglected in vacuum infusion molding process(VIMP). The way of layup, fabric form, fiber type and hybrid mode have remarkable effects on the compressibility of fabric preforms. The undirectional layup results in a higher fiber volume fraction than the orthogonal layup under the same compaction pressure, and the higher fiber volume faction can be achieved in the core hybrid composite compared with that in the interply hybrid composite.
2011, 28(6): 8-13.
doi: CNKI:11-1801/TB.20110720.1334.004
Abstract:
The epoxy molding compounds (EMCs) were prepared by filling high thermal conductive Si3N4 and flame retardant Al(OH)3 into the epoxy. The effects of two fillers on the thermal conductivity and flame retardant of the EMCs were investigated under sole and hybrid fillers filled. The experimental results show that two kinds filler of Si3N4 and Al(OH)3 have similar activity on the flame retardant and thermal conductivity of the EMCs, i.e. with the increasing of filler in the epoxy, the flame retardant and thermal conductivity of the EMCs were improved to a certain extent depend on the type of fillers. Hybrid fillers have a positive effect on the thermal conductivity and flame retardant of EMCs. However, with the volume ratio of Si3N4 to Al(OH)3 changing, the contribution of fillers to the thermal conductivity and flame retardant of EMC appeare cross-coupling each other. When the volume fraction of the hybrid fillers is 60% and the volume ratio of Si3N4 to Al(OH)3 is 3∶2, EMCs with thermal conductivity of 2.15 W/(m·K), LOI of 53.5% and UL-94 vertical burning test ranking of V-0 was obtained.
The epoxy molding compounds (EMCs) were prepared by filling high thermal conductive Si3N4 and flame retardant Al(OH)3 into the epoxy. The effects of two fillers on the thermal conductivity and flame retardant of the EMCs were investigated under sole and hybrid fillers filled. The experimental results show that two kinds filler of Si3N4 and Al(OH)3 have similar activity on the flame retardant and thermal conductivity of the EMCs, i.e. with the increasing of filler in the epoxy, the flame retardant and thermal conductivity of the EMCs were improved to a certain extent depend on the type of fillers. Hybrid fillers have a positive effect on the thermal conductivity and flame retardant of EMCs. However, with the volume ratio of Si3N4 to Al(OH)3 changing, the contribution of fillers to the thermal conductivity and flame retardant of EMC appeare cross-coupling each other. When the volume fraction of the hybrid fillers is 60% and the volume ratio of Si3N4 to Al(OH)3 is 3∶2, EMCs with thermal conductivity of 2.15 W/(m·K), LOI of 53.5% and UL-94 vertical burning test ranking of V-0 was obtained.
2011, 28(6): 14-22.
doi: CNKI:11-1801/TB.20110720.1335.006
Abstract:
Masterbatch M1 of nano-organ-montmorillonite (OMMT)/polyamide-6(PA6) and masterbatch M2 of OMMT/polypropylene(PP) were prepared by melt-extruding method, and nano-OMMT/PA6-PP composites with different OMMT content were prepared with two masterbatches by melt-compound blending with PA6-PP, the composites with the same mass ratio were also prepared by direct blending method. The distribution of OMMT and morphology of the PP disperse phase in composites were characterized by TEM and SEM, and the mechanical properties of nano-OMMT/PA6-PP composites prepared by three processes were also compared. It was found that the OMMT selectively located in PA6 matrix by three processes, and the OMMT shows the best distribution in the composites prepared by the process of M1 masterbatch. The particle size and polydispersity of the PP disperse phase first reduce and then change little with increasing the OMMT content. When the mass ratio of OMMT to PA6-PP is 5∶100, the particle size is minimized and the distribution shows the best. The composites prepared by the processes of masterbatches display smaller disperse phase size and better distribution than that prepared by direct blending. OMMT improvs the flexural modulus, in which the compsites prepared by the process of M1 masterbatch display the highest tensile strength and flexural modulus, and the ones prepared by the process of M2 masterbatch show the best impact toughness.
Masterbatch M1 of nano-organ-montmorillonite (OMMT)/polyamide-6(PA6) and masterbatch M2 of OMMT/polypropylene(PP) were prepared by melt-extruding method, and nano-OMMT/PA6-PP composites with different OMMT content were prepared with two masterbatches by melt-compound blending with PA6-PP, the composites with the same mass ratio were also prepared by direct blending method. The distribution of OMMT and morphology of the PP disperse phase in composites were characterized by TEM and SEM, and the mechanical properties of nano-OMMT/PA6-PP composites prepared by three processes were also compared. It was found that the OMMT selectively located in PA6 matrix by three processes, and the OMMT shows the best distribution in the composites prepared by the process of M1 masterbatch. The particle size and polydispersity of the PP disperse phase first reduce and then change little with increasing the OMMT content. When the mass ratio of OMMT to PA6-PP is 5∶100, the particle size is minimized and the distribution shows the best. The composites prepared by the processes of masterbatches display smaller disperse phase size and better distribution than that prepared by direct blending. OMMT improvs the flexural modulus, in which the compsites prepared by the process of M1 masterbatch display the highest tensile strength and flexural modulus, and the ones prepared by the process of M2 masterbatch show the best impact toughness.
2011, 28(6): 23-27.
doi: CNKI:11-1801/TB.20110720.1340.013
Abstract:
Low viscosity and high-temperature resistant isomeric polyimide resins were synthesized by modified polymerization of monomer reactants (MPMR) method. The effect of molecular mass on the rheology of oligmers and thermal-oxidation stability of cured resins was studied. The molecular structure of polyimide resins, the processing and mechanical properties of their composites were characterized. The results show that the shelf life of resin solution is more than two months. The lowest viscosity of PI-2 resin after imidization is 154 Pa·s. The temperature for 5% mass loss of cured resins is higher than 560 ℃. The flexural strength and flexural modulus of quartz fabric/PI-2 composite at room temperature and 500 ℃ are 917 MPa, 197 MPa and 29 GPa, 22 GPa, respectively. The tensile strength and tensile modulus at room temperature and 500 ℃ are 760 MPa, 341 MPa and 32 GPa, 31 GPa, respectively. The compressive strength at room temperature and 500 ℃ is 570 MPa, 95 MPa respectively. The interlaminar shear strength at room temperature and 500 ℃ is 62 MPa and 10 MPa, respectively.
Low viscosity and high-temperature resistant isomeric polyimide resins were synthesized by modified polymerization of monomer reactants (MPMR) method. The effect of molecular mass on the rheology of oligmers and thermal-oxidation stability of cured resins was studied. The molecular structure of polyimide resins, the processing and mechanical properties of their composites were characterized. The results show that the shelf life of resin solution is more than two months. The lowest viscosity of PI-2 resin after imidization is 154 Pa·s. The temperature for 5% mass loss of cured resins is higher than 560 ℃. The flexural strength and flexural modulus of quartz fabric/PI-2 composite at room temperature and 500 ℃ are 917 MPa, 197 MPa and 29 GPa, 22 GPa, respectively. The tensile strength and tensile modulus at room temperature and 500 ℃ are 760 MPa, 341 MPa and 32 GPa, 31 GPa, respectively. The compressive strength at room temperature and 500 ℃ is 570 MPa, 95 MPa respectively. The interlaminar shear strength at room temperature and 500 ℃ is 62 MPa and 10 MPa, respectively.
2011, 28(6): 28-32.
doi: CNKI:11-1801/TB.20110720.1341.016
Abstract:
Phosphate glass (P-glass)/polypropylene (PP) composites were prepared. The effects of P-glass with different glass transition temperature (Tg) on the crystalline and mechanical properties of PP matrix were studied. The experimental results show that the crystallization temperature of the PP matrix was markedly increased by adding P-glass, in which P-glass with low-Tg plays a crucial role in the heterogeneous nucleation process of PP. The addition of low-Tg P-glass leads to the formation of β crystals and obvious improvement in toughness. The elongation at break of the composites increases from 427% to 545%, and the impact strength increases from 18.6 kJ/m2 to 36.8 kJ/m2.
Phosphate glass (P-glass)/polypropylene (PP) composites were prepared. The effects of P-glass with different glass transition temperature (Tg) on the crystalline and mechanical properties of PP matrix were studied. The experimental results show that the crystallization temperature of the PP matrix was markedly increased by adding P-glass, in which P-glass with low-Tg plays a crucial role in the heterogeneous nucleation process of PP. The addition of low-Tg P-glass leads to the formation of β crystals and obvious improvement in toughness. The elongation at break of the composites increases from 427% to 545%, and the impact strength increases from 18.6 kJ/m2 to 36.8 kJ/m2.
2011, 28(6): 33-38.
doi: CNKI:11-1801/TB.20110720.1421.027
Abstract:
Filled with micro-Al2O3(0.5~3 μm), micro-Si3N4(0.3~3 μm) and nano-Al2O3 , different thermal conductive silicone rubber composites were prepared by the blending method. Micro-Si3N4 and nano-Al2O3 according to different volume ratio were compounded with silicone rubber and the total volume fraction was fixed at 30%. It is found that with the same volume fraction, the thermal conductivity of all the micro-Si3N4 and nano-Al2O3 co-filled composites have remarkable improvement compared with that of the composite filled with micro-Si3N4. Especially, when the volume ratio of micro-Si3N4 to nano-Al2O3 is 26∶4, the thermal conductivity (1.64 W/(m·K)) is three times as high as that of the composite filled with micro-Si3N4 (0.52 W/(m·K)). At the same time, the micro-Si3N4 and nano-Al2O3 co- filled silicone rubber composites remain the good voltage breakdown strength and excellent insulating properties.
Filled with micro-Al2O3(0.5~3 μm), micro-Si3N4(0.3~3 μm) and nano-Al2O3 , different thermal conductive silicone rubber composites were prepared by the blending method. Micro-Si3N4 and nano-Al2O3 according to different volume ratio were compounded with silicone rubber and the total volume fraction was fixed at 30%. It is found that with the same volume fraction, the thermal conductivity of all the micro-Si3N4 and nano-Al2O3 co-filled composites have remarkable improvement compared with that of the composite filled with micro-Si3N4. Especially, when the volume ratio of micro-Si3N4 to nano-Al2O3 is 26∶4, the thermal conductivity (1.64 W/(m·K)) is three times as high as that of the composite filled with micro-Si3N4 (0.52 W/(m·K)). At the same time, the micro-Si3N4 and nano-Al2O3 co- filled silicone rubber composites remain the good voltage breakdown strength and excellent insulating properties.
2011, 28(6): 39-44.
doi: CNKI:11-1801/TB.20110720.1426.039
Abstract:
Nanocrystalline cellulose (NCC) was prepared from hydrolysis of microcrystalline cellulose (MCC) using sulfuric acid. NCC can be used as filler partialy to replace SiO2 and utilized in the preparation of (NCC-SiO2)/NR(natural rubber) composites. The results show that the composites can not only maintain basic mechanical properties, but also decrease heat build-up from 19.9 ℃to 10.6 ℃ and permanent set from 11.4% to 5.9%. When the mass ratio was added with NCC∶SiO2=10∶20, the grade one and six flex cracking times of (NCC-SiO2)/NR composite material increase from 2.5×104 and 6.0×104 (filled by SiO2) to 7.0×104 and 1.2×105, respectively. Aging performance is also superior to SiO2/NR composite materials. After hot air aging, the tensile strength, tear strength and hardness of the composite materials after aging increase by 40%, 21% and 25%, respectively, and the permanent deformation droppes by 25%, while tensile strength and elongation at break remain basically unchanged. Dynamic mechanical performance test shows that when the mass ratio of NCC to SiO2 is from 0∶30 to 20∶10, the rolling resistance of rubber tanδ at 0 ℃ keep almost constant, but the skid resistance of rubber tanδ at 60 ℃ droppes from 0.060 to 0.049. The results of SEM photographs prove that better dispersion and stronger interfacial interaction were achieved in NR matrix filled by NCC-SiO2 than by SiO2.
Nanocrystalline cellulose (NCC) was prepared from hydrolysis of microcrystalline cellulose (MCC) using sulfuric acid. NCC can be used as filler partialy to replace SiO2 and utilized in the preparation of (NCC-SiO2)/NR(natural rubber) composites. The results show that the composites can not only maintain basic mechanical properties, but also decrease heat build-up from 19.9 ℃to 10.6 ℃ and permanent set from 11.4% to 5.9%. When the mass ratio was added with NCC∶SiO2=10∶20, the grade one and six flex cracking times of (NCC-SiO2)/NR composite material increase from 2.5×104 and 6.0×104 (filled by SiO2) to 7.0×104 and 1.2×105, respectively. Aging performance is also superior to SiO2/NR composite materials. After hot air aging, the tensile strength, tear strength and hardness of the composite materials after aging increase by 40%, 21% and 25%, respectively, and the permanent deformation droppes by 25%, while tensile strength and elongation at break remain basically unchanged. Dynamic mechanical performance test shows that when the mass ratio of NCC to SiO2 is from 0∶30 to 20∶10, the rolling resistance of rubber tanδ at 0 ℃ keep almost constant, but the skid resistance of rubber tanδ at 60 ℃ droppes from 0.060 to 0.049. The results of SEM photographs prove that better dispersion and stronger interfacial interaction were achieved in NR matrix filled by NCC-SiO2 than by SiO2.
2011, 28(6): 45-49.
doi: CNKI:11-1801/TB.20110720.1422.028
Abstract:
NBR (nitrile-butadiene rubber) hollow fibers have been prepared by the method of dry-wet phase inversion, in which PVC(polyvinylchloride) was blended to avoid the problems of NBR because of being too viscous and too long time of phase inversion. The NBR hollow fibers may be a new lightweight and consumption reducing damping material. The mechanical property of NBR hollow fibers aroused by changing NBR/PVC mass ratio and polymer mass fraction have been studied. The results show that the damping property of the hollow fiber structure is better than that of the plate membrane structure under the same conditions. The stretching and damping property of NBR hollow fiber can be optimized by changing NBR/PVC mass ratio and polymer mass fraction. The damping peak temperature of NBR hollow fiber decreases by increasing the NBR/PVC mass ratio. When polymer mass fraction is 25% and mass ratio of NBR/PVC is 80∶20, the damping factor of NBR hollow fiber is the largest, which is 0.78.
NBR (nitrile-butadiene rubber) hollow fibers have been prepared by the method of dry-wet phase inversion, in which PVC(polyvinylchloride) was blended to avoid the problems of NBR because of being too viscous and too long time of phase inversion. The NBR hollow fibers may be a new lightweight and consumption reducing damping material. The mechanical property of NBR hollow fibers aroused by changing NBR/PVC mass ratio and polymer mass fraction have been studied. The results show that the damping property of the hollow fiber structure is better than that of the plate membrane structure under the same conditions. The stretching and damping property of NBR hollow fiber can be optimized by changing NBR/PVC mass ratio and polymer mass fraction. The damping peak temperature of NBR hollow fiber decreases by increasing the NBR/PVC mass ratio. When polymer mass fraction is 25% and mass ratio of NBR/PVC is 80∶20, the damping factor of NBR hollow fiber is the largest, which is 0.78.
2011, 28(6): 50-58.
doi: CNKI:11-1801/TB.20110720.1422.030
Abstract:
Organoclay modified polystyrene composites were prepared by melt-compounding polystyrene (PS) resin and organic montmorillonite (OMMT). The structures of the OMMT/PS composites were studied by XRD and high resolution TEM (HRTEM). The pyrolysis behavior and fire performance of the composites were investigated by means of TGA, high temperature degradation, horizontal burning, oxygen index and cone calorimetry experiments. The results indicate that the OMMT/PS composite is an intercalated composite. Compared with pure PS, adding a small amount of organoclay can evidently improve the flame retardancy of the OMMT/PS composite. The OMMT/PS composite with OMMT/PS mass ratio of 2/100 exhibits much higher thermal stability, of which the degradation temperature with 10% and 50% mass losses can increase by 7.8 ℃ and 15.2 ℃, respectively. The residue percentage at 500 ℃ and oxygen index rise by 2.6% and 1.4%, respectively, while the peak heat release rate decreases by 21.0%. The shielding of OMMT layers to the intercalated polymer chains and the formation of a continuous and compact char residue layer, which covers on the burnt polymer composite surface, can prevent the polymer from further degradation and decrease its degradation rate. The increase of melt viscosity of the OMMT/PS composite decreases the transfer rate of the combustible small-molecular compounds to the flame zone and thus suppresses the supply of fuel to the fire. The flame retardancy of the composites is enhanced due to both factors.
Organoclay modified polystyrene composites were prepared by melt-compounding polystyrene (PS) resin and organic montmorillonite (OMMT). The structures of the OMMT/PS composites were studied by XRD and high resolution TEM (HRTEM). The pyrolysis behavior and fire performance of the composites were investigated by means of TGA, high temperature degradation, horizontal burning, oxygen index and cone calorimetry experiments. The results indicate that the OMMT/PS composite is an intercalated composite. Compared with pure PS, adding a small amount of organoclay can evidently improve the flame retardancy of the OMMT/PS composite. The OMMT/PS composite with OMMT/PS mass ratio of 2/100 exhibits much higher thermal stability, of which the degradation temperature with 10% and 50% mass losses can increase by 7.8 ℃ and 15.2 ℃, respectively. The residue percentage at 500 ℃ and oxygen index rise by 2.6% and 1.4%, respectively, while the peak heat release rate decreases by 21.0%. The shielding of OMMT layers to the intercalated polymer chains and the formation of a continuous and compact char residue layer, which covers on the burnt polymer composite surface, can prevent the polymer from further degradation and decrease its degradation rate. The increase of melt viscosity of the OMMT/PS composite decreases the transfer rate of the combustible small-molecular compounds to the flame zone and thus suppresses the supply of fuel to the fire. The flame retardancy of the composites is enhanced due to both factors.
2011, 28(6): 59-64.
doi: CNKI:11-1801/TB.20110720.1424.036
Abstract:
A modified bismaleimide resin film with a good film-formability was fabricated by adding thermoplastic polyether sulphone (PES). The DSC, gel time, dynamic viscosity and viscosity at certain temperature were measured. The film has a low viscosity at 130 ℃ (139.3 mPa·s), and the retention time for viscosity less than 1000 mPa·s and 3000 mPa·s at 130 ℃ are 98 min and 117 min, respectively, which makes the resin easily impregnate the fiber perform thoroughly in resin film infusion (RFI) process. A numerical simulation of RFI for composite unit with crossed stiffener was analyzed by control volume/finite element method. The change of infusion height with time, the pressure distribution and the limit infusion height at 130 ℃ and -0.1 MPa were predicted. The arbon fiber/madiied bismaleimide composite with crossed stiffener was successfully prepared, in which no obvious defects were observed by A and C scan.
A modified bismaleimide resin film with a good film-formability was fabricated by adding thermoplastic polyether sulphone (PES). The DSC, gel time, dynamic viscosity and viscosity at certain temperature were measured. The film has a low viscosity at 130 ℃ (139.3 mPa·s), and the retention time for viscosity less than 1000 mPa·s and 3000 mPa·s at 130 ℃ are 98 min and 117 min, respectively, which makes the resin easily impregnate the fiber perform thoroughly in resin film infusion (RFI) process. A numerical simulation of RFI for composite unit with crossed stiffener was analyzed by control volume/finite element method. The change of infusion height with time, the pressure distribution and the limit infusion height at 130 ℃ and -0.1 MPa were predicted. The arbon fiber/madiied bismaleimide composite with crossed stiffener was successfully prepared, in which no obvious defects were observed by A and C scan.
2011, 28(6): 65-70.
doi: CNKI:11-1801/TB.20110720.1338.009
Abstract:
The terephthalic type unsaturated polyesters resin(UPR), prepared with dimethyl terephthalate(DMT), maleic anhydride(MA) and propylene glycol(PG), was reinforced with the surface-modified MgO powder to prepare MgO/UPR composite through mechanical blending. The dispersion of surface-modified MgO powder in the UPR matrix, the effect of the mass fraction of MgO on the dynamic thermal mechanical properties, heat resistance and hardness of MgO/UPR composites were investigated. XRD, FTIR and SEM results illustrate that the surface of MgO is coated with a layer of organic functional groups and disperses well in UPR after being modified by sodium stearate. The results of dynamic mechanical analysis (DMA) show when the mass fraction of MgO is 9%, the MgO/UPR composite has the best dynamic mechanical properties, heat resistance, and slow decrease of storage modulus with increasing temperature. The glass transition temperature(Tg) reaches 191 ℃ which is 66 ℃ higher than that of the pure UPR. The hardness analyses indicate MgO/UPR composite has the maximum barcol hardness HBa 44 when the mass fraction of MgO is 4%, which is 18.9% higher than that of pure UPR.
The terephthalic type unsaturated polyesters resin(UPR), prepared with dimethyl terephthalate(DMT), maleic anhydride(MA) and propylene glycol(PG), was reinforced with the surface-modified MgO powder to prepare MgO/UPR composite through mechanical blending. The dispersion of surface-modified MgO powder in the UPR matrix, the effect of the mass fraction of MgO on the dynamic thermal mechanical properties, heat resistance and hardness of MgO/UPR composites were investigated. XRD, FTIR and SEM results illustrate that the surface of MgO is coated with a layer of organic functional groups and disperses well in UPR after being modified by sodium stearate. The results of dynamic mechanical analysis (DMA) show when the mass fraction of MgO is 9%, the MgO/UPR composite has the best dynamic mechanical properties, heat resistance, and slow decrease of storage modulus with increasing temperature. The glass transition temperature(Tg) reaches 191 ℃ which is 66 ℃ higher than that of the pure UPR. The hardness analyses indicate MgO/UPR composite has the maximum barcol hardness HBa 44 when the mass fraction of MgO is 4%, which is 18.9% higher than that of pure UPR.
2011, 28(6): 71-79.
doi: CNKI:11-1801/TB.20110720.1338.010
Abstract:
The PA66-based composites containing surface modified nano-SiO2 with different treatments were prepared in a twin-screw extruder by melt compounding. The interaction of different surface modified nano-SiO2 and PA66 in composites systems was studied by FTIR and XPS, and the thermal properties of composites were investigated. The results show that different surface modification treatments bring different interface interactions between nano-SiO2 and PA66, which can influence the melting and crystallization behavior of the PA66 matrix. The presence of modified nano-SiO2 can result in a lower crystallization temperature and smaller grain size of composites compared with pure PA66 and cause changes in crystallinity of nano-SiO2/PA66 composites. The TGA and DMA results indicate that surface modification structures of nano-SiO2 can produce effect on the thermal stability and glass transition temperature of nano-SiO2/PA66 composites.
The PA66-based composites containing surface modified nano-SiO2 with different treatments were prepared in a twin-screw extruder by melt compounding. The interaction of different surface modified nano-SiO2 and PA66 in composites systems was studied by FTIR and XPS, and the thermal properties of composites were investigated. The results show that different surface modification treatments bring different interface interactions between nano-SiO2 and PA66, which can influence the melting and crystallization behavior of the PA66 matrix. The presence of modified nano-SiO2 can result in a lower crystallization temperature and smaller grain size of composites compared with pure PA66 and cause changes in crystallinity of nano-SiO2/PA66 composites. The TGA and DMA results indicate that surface modification structures of nano-SiO2 can produce effect on the thermal stability and glass transition temperature of nano-SiO2/PA66 composites.
2011, 28(6): 80-85.
doi: CNKI:11-1801/TB.20110720.1337.008
Abstract:
The epoxy was modified by polyethylene glycol (PEG) to synthesize self-emulsifying epoxy emulsion, which was characterized by FTIR to confirm its structure. The stability of the epoxy emulsion stemmed in different experimental circumstances was investigated to analyze the effects of the reactants, process and other factors on the final products, and to reveal the optimal process parameters. The thermal properties of the sizing agents were characterized by TG and DSC, the wetting property of the sizing agents were characterized through contact angle test, and the IFSS (interfacial shear strength) of a single fiber was characterized by a single fiber fragmentation test. The results show that the emulsion prepared by reaction of the epoxy and PEG-1000 at 80~120 ℃ has the best stability. The sizing agents has good thermal stability and wetting property. The fuzz amount of carbon fiber decreases and the IFSS (interfacial shear strength) increases by 33.48% after sizing with the epoxy emulsion.
The epoxy was modified by polyethylene glycol (PEG) to synthesize self-emulsifying epoxy emulsion, which was characterized by FTIR to confirm its structure. The stability of the epoxy emulsion stemmed in different experimental circumstances was investigated to analyze the effects of the reactants, process and other factors on the final products, and to reveal the optimal process parameters. The thermal properties of the sizing agents were characterized by TG and DSC, the wetting property of the sizing agents were characterized through contact angle test, and the IFSS (interfacial shear strength) of a single fiber was characterized by a single fiber fragmentation test. The results show that the emulsion prepared by reaction of the epoxy and PEG-1000 at 80~120 ℃ has the best stability. The sizing agents has good thermal stability and wetting property. The fuzz amount of carbon fiber decreases and the IFSS (interfacial shear strength) increases by 33.48% after sizing with the epoxy emulsion.
2011, 28(6): 86-91.
doi: CNKI:11-1801/TB.20110720.1419.024
Abstract:
Hydroxyapatite/polyamide-66 (HA/PA66) composite porous scaffolds were prepared using injection-molding technique and analyzed by means of SEM, XRD, DSC and mechanical testing. The results demonstrate that the mechanical properties, porosity and pore size of HA/PA66 composite scaffolds can be effectively controlled by changing the molding parameters (foaming agent and shot size). HA particles increase the stiffness of HA/PA66 composite scaffolds accompanied by the reduction of pore size and porosity. The addition of ethylene-vinyl acetate copolymer (EVA) in HA/PA66 (30/70, mass ratio) scaffolds conduces to the pore growth, the formation of uniform porous structure, the improvement of the scaffolds'mechanical properties and melt processability of the composites. The injection-molding method can rapidly and conveniently fabricate the composite scaffolds. The obtained scaffolds with a pore size ranging from 200 μm to 600 μm and a porosity more than 64% can simultaneously meet the requirements of porous structure and mechanical performance. The compressive properties of the scaffolds are similar to or higher than those of trabecular bone and close to those of the cancellous bone.
Hydroxyapatite/polyamide-66 (HA/PA66) composite porous scaffolds were prepared using injection-molding technique and analyzed by means of SEM, XRD, DSC and mechanical testing. The results demonstrate that the mechanical properties, porosity and pore size of HA/PA66 composite scaffolds can be effectively controlled by changing the molding parameters (foaming agent and shot size). HA particles increase the stiffness of HA/PA66 composite scaffolds accompanied by the reduction of pore size and porosity. The addition of ethylene-vinyl acetate copolymer (EVA) in HA/PA66 (30/70, mass ratio) scaffolds conduces to the pore growth, the formation of uniform porous structure, the improvement of the scaffolds'mechanical properties and melt processability of the composites. The injection-molding method can rapidly and conveniently fabricate the composite scaffolds. The obtained scaffolds with a pore size ranging from 200 μm to 600 μm and a porosity more than 64% can simultaneously meet the requirements of porous structure and mechanical performance. The compressive properties of the scaffolds are similar to or higher than those of trabecular bone and close to those of the cancellous bone.
2011, 28(6): 92-97.
doi: CNKI:11-1801/TB.20110720.1425.037
Abstract:
Comparing with the unidirectional(UD) cloth T700/bismaleimide(BMI)6421 composite, mechanical properties of warp-knitted fabric T700/BMI6421 composite were studied. Bending properties and interlaminar shear properties of warp-knitted fabric T700/BMI6421 composite were tested. The variety in fabric structure caused by warp-knitted thread were demonstrated with metallographic microscope and SEM images. It is shown fiber distortions caused by warp-knitted thread decrease the bending performance. The bending modulus is 26% lower than the unidirectional cloth reinforced composite in the 45°direction. The interlaminar shear performance is improved by stitching structure which make the fiber layer tighter. The interlaminar shear strength(ILSS) is about 13% higher than the unidirectional cloth reinforced composite in the 0°direction. It is confirmed that traditional unidirectional cloth could be replaced by warp-knitted fabric in liquid composite molding process.
Comparing with the unidirectional(UD) cloth T700/bismaleimide(BMI)6421 composite, mechanical properties of warp-knitted fabric T700/BMI6421 composite were studied. Bending properties and interlaminar shear properties of warp-knitted fabric T700/BMI6421 composite were tested. The variety in fabric structure caused by warp-knitted thread were demonstrated with metallographic microscope and SEM images. It is shown fiber distortions caused by warp-knitted thread decrease the bending performance. The bending modulus is 26% lower than the unidirectional cloth reinforced composite in the 45°direction. The interlaminar shear performance is improved by stitching structure which make the fiber layer tighter. The interlaminar shear strength(ILSS) is about 13% higher than the unidirectional cloth reinforced composite in the 0°direction. It is confirmed that traditional unidirectional cloth could be replaced by warp-knitted fabric in liquid composite molding process.
2011, 28(6): 98-103.
doi: CNKI:11-1801/TB.20110720.1423.031
Abstract:
Bioactive glass(BG)/poly(ε-caprolactone)(PCL) porous composites modified by collagen for bone repairing were prepared by combining particulates-leaching and solvent-evaporation methods. The morphology of the porous materials and pore-wall, mineralization activity, ionic concentration and variation of pH values were characterized by SEM, FTIR, XRD, plasma atomic emission spectroscope and pH meter. The effects of colllagen on the porosity and water absorption rate were characterized by traditional specific-gravity and weighing methods. The results indicate that collagen can be succesfully adhered onto the pore wall and the mineralization activity and degradability of BG/PCL are effectively improved. Porosity and water absorption rate are as high as 96.400%±0.018% and 13.65±1.65, respectively.
Bioactive glass(BG)/poly(ε-caprolactone)(PCL) porous composites modified by collagen for bone repairing were prepared by combining particulates-leaching and solvent-evaporation methods. The morphology of the porous materials and pore-wall, mineralization activity, ionic concentration and variation of pH values were characterized by SEM, FTIR, XRD, plasma atomic emission spectroscope and pH meter. The effects of colllagen on the porosity and water absorption rate were characterized by traditional specific-gravity and weighing methods. The results indicate that collagen can be succesfully adhered onto the pore wall and the mineralization activity and degradability of BG/PCL are effectively improved. Porosity and water absorption rate are as high as 96.400%±0.018% and 13.65±1.65, respectively.
2011, 28(6): 104-108.
doi: CNKI:11-1801/TB.20110720.1340.014
Abstract:
The magnetic ZnFe2O4 nanoparticles were prepared by sol-gel method, and the carboxymethyl chitosan(CMC) was obtained by modification of chitosan with water as the solvent. The ZnFe2O4 coated magnetic ZnFe2O4 -CMC composite microspheres were prepared with the crosslinker, in which the aspirin has been loaded. The materials were characterized by XRD, IR, SEM, TEM, VSM, UV, et al. The results show that the magnetic composite microspheres are well-shaped with the average diameter being about 1~5 μm, the saturation magnetization being 10.99 emu/g, the dose of releasing drug being 76.82% in 24 h, the loading rate being 0.801 g/g and the enveloping rate being 78.3%. The performance of material is excellent, which may be used as a novel drug carrier.
The magnetic ZnFe2O4 nanoparticles were prepared by sol-gel method, and the carboxymethyl chitosan(CMC) was obtained by modification of chitosan with water as the solvent. The ZnFe2O4 coated magnetic ZnFe2O4 -CMC composite microspheres were prepared with the crosslinker, in which the aspirin has been loaded. The materials were characterized by XRD, IR, SEM, TEM, VSM, UV, et al. The results show that the magnetic composite microspheres are well-shaped with the average diameter being about 1~5 μm, the saturation magnetization being 10.99 emu/g, the dose of releasing drug being 76.82% in 24 h, the loading rate being 0.801 g/g and the enveloping rate being 78.3%. The performance of material is excellent, which may be used as a novel drug carrier.
2011, 28(6): 109-117.
doi: CNKI:11-1801/TB.20110720.1424.035
Abstract:
The optimum processing conditions were determined by orthogonal design to prepare ultra-high molecular weight polyethylene loaded with sodium alendronate (ALN/UHMWPE). The range analysis and analysis of variance(ANOVA) of tensile strength and broken elongation were carried out by statistiacl package for the social science (SPSS). The tensile test, XRD , DSC, SEM and EDS were used to characterize ALN/UHMWPE prepared under the optimum processing conditions. The orthogonal design combined with statistical analyses reveals that the optimal processing conditions for the uniform dispersion of ALN in UHMWPE are as follows: surfactant (F68), ultra sonic dispersion, 1% mass fraction of ALN and at 37 ℃. ANOVA shows a significant difference. The tensile tests indicate that both tensile strength and broken elongation of (ALN-F68)/UHMWPE increase compared with ALN/UHMWPE. The crystallinity of (ALN-F68)/UHMWPE is slightly higher than that of ALN/UHMWPE, both of which are lower than UHMWPE. No phase or melting behavior changes resulting from ALN addition are observed. The addition of F68 leads to a more uniform distribution of ALN in (ALN-F68)/UHMWPE.
The optimum processing conditions were determined by orthogonal design to prepare ultra-high molecular weight polyethylene loaded with sodium alendronate (ALN/UHMWPE). The range analysis and analysis of variance(ANOVA) of tensile strength and broken elongation were carried out by statistiacl package for the social science (SPSS). The tensile test, XRD , DSC, SEM and EDS were used to characterize ALN/UHMWPE prepared under the optimum processing conditions. The orthogonal design combined with statistical analyses reveals that the optimal processing conditions for the uniform dispersion of ALN in UHMWPE are as follows: surfactant (F68), ultra sonic dispersion, 1% mass fraction of ALN and at 37 ℃. ANOVA shows a significant difference. The tensile tests indicate that both tensile strength and broken elongation of (ALN-F68)/UHMWPE increase compared with ALN/UHMWPE. The crystallinity of (ALN-F68)/UHMWPE is slightly higher than that of ALN/UHMWPE, both of which are lower than UHMWPE. No phase or melting behavior changes resulting from ALN addition are observed. The addition of F68 leads to a more uniform distribution of ALN in (ALN-F68)/UHMWPE.
2011, 28(6): 118-124.
doi: CNKI:11-1801/TB.20110720.1341.018
Abstract:
Mechanisms of near-net-shape reducing-yarn braiding were discussed. Microstructures in yarn-reducing regions were characterized by image observation and topological analysis. Flexural properties in the tapered regions of the reducing-yarn composites or cut composites and those of the uniform composites were compared. Finally, failure mechanisms of the reducing-yarn composites and cut composites were analyzed. The results indicate that continuity of the braiding process after yarn reduction must be ensured. The reducing-yarn preforms have a trapezoid profile near the reducing-yarn cross-section. Flexural properties of the reducing-yarn composites are higher than those of cut counterparts but lower than the uniform composites. The reducing-yarn composites show compound failure modes, which are dominated by yarn breakage and also include matrix cracking and fiber pulling-out.
Mechanisms of near-net-shape reducing-yarn braiding were discussed. Microstructures in yarn-reducing regions were characterized by image observation and topological analysis. Flexural properties in the tapered regions of the reducing-yarn composites or cut composites and those of the uniform composites were compared. Finally, failure mechanisms of the reducing-yarn composites and cut composites were analyzed. The results indicate that continuity of the braiding process after yarn reduction must be ensured. The reducing-yarn preforms have a trapezoid profile near the reducing-yarn cross-section. Flexural properties of the reducing-yarn composites are higher than those of cut counterparts but lower than the uniform composites. The reducing-yarn composites show compound failure modes, which are dominated by yarn breakage and also include matrix cracking and fiber pulling-out.
2011, 28(6): 125-130.
doi: CNKI:11-1801/TB.20110720.1425.038
Abstract:
In order to explore the improving effect of SiO2 on the properties of fast-growing plantation poplar wood, two kinds of SiO2/poplar wood composites were prepared by sol-gel and impregnating silicasol method, respectively. The performances of microscopic morphology, structure composition and thermal degradation about the composites were characterized and evaluated by SEM, XRD, FTIR and thermal analysis. The results show that SiO2 has a wide distribution in the vessels, wood fibers and gaps between wood cells in the wood substrate, and its contact with wood cell walls in the composites fabricated by means of sol-gel is tighter which presents more effective filling and combination. The diffraction intensity and crystallinity in wood cellulose of SiO2/poplar wood composites exhibit a decreasing trend resulting from the introduction of SiO2, and the variation of (100) crystal surfaces in the composite fabricated by sol-gel is more obvious. The pyrolysis temperatures of SiO2/poplar wood composites decrease from 420 ℃ to 380 ℃ with a narrowing of pyrolysis reaction, accelerating the occurs of wood carbonization to protect wood substrate from burnout adequately in some extent.
In order to explore the improving effect of SiO2 on the properties of fast-growing plantation poplar wood, two kinds of SiO2/poplar wood composites were prepared by sol-gel and impregnating silicasol method, respectively. The performances of microscopic morphology, structure composition and thermal degradation about the composites were characterized and evaluated by SEM, XRD, FTIR and thermal analysis. The results show that SiO2 has a wide distribution in the vessels, wood fibers and gaps between wood cells in the wood substrate, and its contact with wood cell walls in the composites fabricated by means of sol-gel is tighter which presents more effective filling and combination. The diffraction intensity and crystallinity in wood cellulose of SiO2/poplar wood composites exhibit a decreasing trend resulting from the introduction of SiO2, and the variation of (100) crystal surfaces in the composite fabricated by sol-gel is more obvious. The pyrolysis temperatures of SiO2/poplar wood composites decrease from 420 ℃ to 380 ℃ with a narrowing of pyrolysis reaction, accelerating the occurs of wood carbonization to protect wood substrate from burnout adequately in some extent.
2011, 28(6): 132-136.
doi: CNKI:11-1801/TB.20110720.1418.022
Abstract:
In order to understand the dynamic viscoelasticity property of phenol liquefaction products from Chinese fir, this research studied storage modulus E' and loss factor tgδ property at 1Hz, 10Hz, 50Hz and -120~100 ℃ using dynamic mechanical analysis and discussed the effect of liquefaction factors on dynamic viscoelasticity. The results show that a glass transfer temperature (Tg ) occurs in the liquefaction products. An α' relaxation peak exists at the range of 0~50 ℃ and an α″ relaxation peak exists at the range of 50~100 ℃. The activation energy of α″ is much higher than that of α'. Moreover, the activation energy of α' increases with the increasing of liquefaction time, while the activation energy of α″ decreases with the increasing of the mass ratio of phenol to Chinese fir.
In order to understand the dynamic viscoelasticity property of phenol liquefaction products from Chinese fir, this research studied storage modulus E' and loss factor tgδ property at 1Hz, 10Hz, 50Hz and -120~100 ℃ using dynamic mechanical analysis and discussed the effect of liquefaction factors on dynamic viscoelasticity. The results show that a glass transfer temperature (Tg ) occurs in the liquefaction products. An α' relaxation peak exists at the range of 0~50 ℃ and an α″ relaxation peak exists at the range of 50~100 ℃. The activation energy of α″ is much higher than that of α'. Moreover, the activation energy of α' increases with the increasing of liquefaction time, while the activation energy of α″ decreases with the increasing of the mass ratio of phenol to Chinese fir.
2011, 28(6): 137-141.
doi: CNKI:11-1801/TB.20110720.1341.015
Abstract:
Different diameters and depths of blind holes were drilled in the samples of 3D needled C/SiC composites to simulate air void defects in this paper. Thermal imaging testing was used to detect the blind hole defects, and then the dimension and location information of the defects were obtained. Two methods, i.e. peak temperature-contrast method and logarithmic peak second-derivative method, were used to measure the defect depths, and the errors of these measured results were discussed. The results indicate that both of the two methods can be used to successfully measure the depth of the blind holes, but the measured error for the two methods is different. The error of peak temperature-contrast method is less than the other method when the ratio of diameter to depth ranges from 1 to 4.4. Though the error of logarithmic peak second-derivative method is a bit larger than the other, this method can be used for wider ratios of diameter to depth, and the error of this method decreases as the ratio of diameter to depth increases.
Different diameters and depths of blind holes were drilled in the samples of 3D needled C/SiC composites to simulate air void defects in this paper. Thermal imaging testing was used to detect the blind hole defects, and then the dimension and location information of the defects were obtained. Two methods, i.e. peak temperature-contrast method and logarithmic peak second-derivative method, were used to measure the defect depths, and the errors of these measured results were discussed. The results indicate that both of the two methods can be used to successfully measure the depth of the blind holes, but the measured error for the two methods is different. The error of peak temperature-contrast method is less than the other method when the ratio of diameter to depth ranges from 1 to 4.4. Though the error of logarithmic peak second-derivative method is a bit larger than the other, this method can be used for wider ratios of diameter to depth, and the error of this method decreases as the ratio of diameter to depth increases.
2011, 28(6): 142-147.
doi: CNKI:11-1801/TB.20110720.1420.026
Abstract:
Multi-walled carbon nanotubes(MWCNTs) reinforced Al matrix composites were prepared by friction stir processing(FSP). The microstructure and hardness of the composites were investigated. The results show that the MWCNTS/Al is composed of fine equiaxed grains but the grains are uneven. The interface between MWCNTs and the matrix is well binded. A large numbers of dislocations were distributed in the interface. MWCNTs mainly distributed within the aluminum grains. The grain refinement is realized by recrystallization through a subcrystal nucleating mode. The nucleis form nucleus in the primary grains and the formed subcrystal. Therefore, the grains are refined gradually. With increasing MWCNTs content, the hardness of MWCNTs/Al composite increases. When the volume fraction of MWCNTs is 6%, the microhardness is HV 63.4 which is 1.9 times as hard as Al made after 5 times of FSP.
Multi-walled carbon nanotubes(MWCNTs) reinforced Al matrix composites were prepared by friction stir processing(FSP). The microstructure and hardness of the composites were investigated. The results show that the MWCNTS/Al is composed of fine equiaxed grains but the grains are uneven. The interface between MWCNTs and the matrix is well binded. A large numbers of dislocations were distributed in the interface. MWCNTs mainly distributed within the aluminum grains. The grain refinement is realized by recrystallization through a subcrystal nucleating mode. The nucleis form nucleus in the primary grains and the formed subcrystal. Therefore, the grains are refined gradually. With increasing MWCNTs content, the hardness of MWCNTs/Al composite increases. When the volume fraction of MWCNTs is 6%, the microhardness is HV 63.4 which is 1.9 times as hard as Al made after 5 times of FSP.
2011, 28(6): 148-152.
doi: CNKI:11-1801/TB.20110720.1419.025
Abstract:
Alkaline solution treatment was used to purify B4C powder and enhance the wetting ability between the B4C powder and the Mg-Li matrix. The results show that both of the specific surface and B2O3 decrease. Tensile strength and density of the pre-mixed alloy prepared by the B4C powder after alkaline treatment increase. Fewer agglomerates and uniform formation are proved in the metallographic structure of the B4C/Mg-Li composite (Mg-15Li-2Al-6B4C). The tensile strength of B4C/Mg-Li composite increases 21.53% compared with that prepared by B4C without alkaline solution treatment. Results indicate that the alkaline solution treatment of B4C powder can improve the strengthening effect of the boride in-situ reacted in the B4C/Mg-Li composite.
Alkaline solution treatment was used to purify B4C powder and enhance the wetting ability between the B4C powder and the Mg-Li matrix. The results show that both of the specific surface and B2O3 decrease. Tensile strength and density of the pre-mixed alloy prepared by the B4C powder after alkaline treatment increase. Fewer agglomerates and uniform formation are proved in the metallographic structure of the B4C/Mg-Li composite (Mg-15Li-2Al-6B4C). The tensile strength of B4C/Mg-Li composite increases 21.53% compared with that prepared by B4C without alkaline solution treatment. Results indicate that the alkaline solution treatment of B4C powder can improve the strengthening effect of the boride in-situ reacted in the B4C/Mg-Li composite.
2011, 28(6): 153-158.
doi: CNKI:11-1801/TB.20110720.1339.011
Abstract:
The effects of diluting agent Al2O3 on the combustion velocity and the products microstructure of NiO/Al aluminothermic system were studied. Combined with the adiabatic temperature calculation, the apparent activation energy of NiO/Al system were measured by Arrhenius diagram of ln(v/Tad)-1/Tad based on the combustion equation proposed by Merzhanov et al. The results show that in a certain range of Al2O3 mass fraction(0~5％, 25%~35％), the combustion velocity of NiO/Al aluminothermic system is considerable invariable. The further results show that the process of combustion is contributed to the mass-transferring of Al reactant of burning compact. When the temperature above the boiling point of Al(2740 K), the apparent activation energy of NiO/Al aluminothermic system is (64±14) kJ/mol. On the contrary, that is (189±15) kJ/mol.
The effects of diluting agent Al2O3 on the combustion velocity and the products microstructure of NiO/Al aluminothermic system were studied. Combined with the adiabatic temperature calculation, the apparent activation energy of NiO/Al system were measured by Arrhenius diagram of ln(v/Tad)-1/Tad based on the combustion equation proposed by Merzhanov et al. The results show that in a certain range of Al2O3 mass fraction(0~5％, 25%~35％), the combustion velocity of NiO/Al aluminothermic system is considerable invariable. The further results show that the process of combustion is contributed to the mass-transferring of Al reactant of burning compact. When the temperature above the boiling point of Al(2740 K), the apparent activation energy of NiO/Al aluminothermic system is (64±14) kJ/mol. On the contrary, that is (189±15) kJ/mol.
2011, 28(6): 159-165.
doi: CNKI:11-1801/TB.20110720.1423.032
Abstract:
The composite photoanodes with different mass ratios of ZnO nano-flowers to TiO2 nano-particles were prepared on transparent conductive fluorine-doped SnO2 (FTO) substrates by doctor-blade technique. These anodes were sealed together with Pt-counter electrode to assemble into dye-sensitized solar cell(DSSC). The effect of mass ratio of ZnO nano-flowers to TiO2 nano-particles on the performance and electron transport properties of DSSC were studied by means of the photocurrent-voltage curve and electrochemical impedance spectroscopy. The results show that open-circuit voltage and fill factor of DSSC increase with increasing the mass ratio of TiO2 nanopartices in composite photoanodes. The energy conversion efficiency reaches 3.20% when the mass ratio of ZnO to TiO2 is 83∶17. The impedance spectrum of DSSC assembled from ZnO-TiO2 composite anodes is similar to Gerisher impedance, and the impedance of diffusion is coupled with impedance of recombination.
The composite photoanodes with different mass ratios of ZnO nano-flowers to TiO2 nano-particles were prepared on transparent conductive fluorine-doped SnO2 (FTO) substrates by doctor-blade technique. These anodes were sealed together with Pt-counter electrode to assemble into dye-sensitized solar cell(DSSC). The effect of mass ratio of ZnO nano-flowers to TiO2 nano-particles on the performance and electron transport properties of DSSC were studied by means of the photocurrent-voltage curve and electrochemical impedance spectroscopy. The results show that open-circuit voltage and fill factor of DSSC increase with increasing the mass ratio of TiO2 nanopartices in composite photoanodes. The energy conversion efficiency reaches 3.20% when the mass ratio of ZnO to TiO2 is 83∶17. The impedance spectrum of DSSC assembled from ZnO-TiO2 composite anodes is similar to Gerisher impedance, and the impedance of diffusion is coupled with impedance of recombination.
2011, 28(6): 166-171.
doi: CNKI:11-1801/TB.20110720.1417.019
Abstract:
Al/AlN composites with different Al content were prepared by infiltrating AlN preforms with molten AlSi7Mg alloy. Phase composition of the composites was characterized by XRD. Microstructure of the composites was observed by optical microscope and SEM. Mechanical and thermal properties of the composites with different Al content were also tested. The results show that Al/AlN composites with relative density of more than 98.5% can be obtained by infiltrating the AlN preforms with different porosity at 900℃ in N2 atmosphere. There is nearly no shape and dimension change of AlN preforms during the infiltration process. The mechanical and thermal properties of the composites vary with Al content. As Al volume fraction varies from 38% to 62%, the Vickers hardness of the composites decreases from HV 715 to HV 203, the bending strength decreases from 492 MPa to 388 MPa, the room temperature thermal conductivity of the composites increases from 73 W/(m·K) to 120 W/(m·K), and the mean linear thermal expansion coefficient (TEC) between room temperature and 200 ℃ varies from 8.60×10-6 K-1 to 1.11×10-5 K-1. The results also show that the relation between the TEC and Al volume fraction of the composites agrees with the Kerner model.
Al/AlN composites with different Al content were prepared by infiltrating AlN preforms with molten AlSi7Mg alloy. Phase composition of the composites was characterized by XRD. Microstructure of the composites was observed by optical microscope and SEM. Mechanical and thermal properties of the composites with different Al content were also tested. The results show that Al/AlN composites with relative density of more than 98.5% can be obtained by infiltrating the AlN preforms with different porosity at 900℃ in N2 atmosphere. There is nearly no shape and dimension change of AlN preforms during the infiltration process. The mechanical and thermal properties of the composites vary with Al content. As Al volume fraction varies from 38% to 62%, the Vickers hardness of the composites decreases from HV 715 to HV 203, the bending strength decreases from 492 MPa to 388 MPa, the room temperature thermal conductivity of the composites increases from 73 W/(m·K) to 120 W/(m·K), and the mean linear thermal expansion coefficient (TEC) between room temperature and 200 ℃ varies from 8.60×10-6 K-1 to 1.11×10-5 K-1. The results also show that the relation between the TEC and Al volume fraction of the composites agrees with the Kerner model.
2011, 28(6): 172-179.
doi: CNKI:11-1801/TB.20110720.1332.001
Abstract:
Nb-16Si-xFe in-situ composites (x = 2, 4, 6, atom fraction(%), referred to 2Fe, 4Fe and 6Fe alloy, respectively, hereafter) were prepared by vacuum non-consumable arc-melting method and the effect of Fe additions on the microstructures and room-temperature mechanical properties of the Nb-16Si alloy was studied. The results reveal that the as-cast and heat-treated (vacuum annealing 100 h at 1350 ℃) 2Fe and 4Fe alloys are composed of Nb solid solution (NbSS), silicides of Nb3Si and Nb4FeSi, while the 6Fe alloy is composed of the NbSS phase and the Nb4FeSi silicide. As the Fe content increasing, the volume fraction of the Nb3Si phase decreases, while that of the Nb4FeSi phase increases. Small silicde particles precipitate in the heat-treated NbSS phase. For the Nb4FeSi, a new stiffening phase in the Nb-16Si alloy, its microhardness and fracture toughness are HV 1110 and 1.22 MPa·m1/2, respectively. With the increasing of the atom fration of Fe from 2% to 6%, the room-temperature fracture toughness of the heat-treated alloys shows a decreasing tendency, while the hardness and compressive strength increase.
Nb-16Si-xFe in-situ composites (x = 2, 4, 6, atom fraction(%), referred to 2Fe, 4Fe and 6Fe alloy, respectively, hereafter) were prepared by vacuum non-consumable arc-melting method and the effect of Fe additions on the microstructures and room-temperature mechanical properties of the Nb-16Si alloy was studied. The results reveal that the as-cast and heat-treated (vacuum annealing 100 h at 1350 ℃) 2Fe and 4Fe alloys are composed of Nb solid solution (NbSS), silicides of Nb3Si and Nb4FeSi, while the 6Fe alloy is composed of the NbSS phase and the Nb4FeSi silicide. As the Fe content increasing, the volume fraction of the Nb3Si phase decreases, while that of the Nb4FeSi phase increases. Small silicde particles precipitate in the heat-treated NbSS phase. For the Nb4FeSi, a new stiffening phase in the Nb-16Si alloy, its microhardness and fracture toughness are HV 1110 and 1.22 MPa·m1/2, respectively. With the increasing of the atom fration of Fe from 2% to 6%, the room-temperature fracture toughness of the heat-treated alloys shows a decreasing tendency, while the hardness and compressive strength increase.
2011, 28(6): 180-183.
doi: CNKI:11-1801/TB.20110720.1337.007
Abstract:
Tungsten/Al-Cu powder compacts with different tungsten powder contents were synthesized by laser combustion. The influences of tungsten powder content on the microstructure, densification and hardness of tungsten/Al-Cu composite were studied by SEM, OM, XRD and Vickers hardness tester. The results show that doped tungsten powders can refine alloys structure, increase the uniformity of alloys and promote densification. When the mass ratio of doped tungsten powder to Al-Cu powder is 3%, the synthesized density and hardness of sample reach the highest values, i.e. 3.43 g/cm3 and HV 244.4.
Tungsten/Al-Cu powder compacts with different tungsten powder contents were synthesized by laser combustion. The influences of tungsten powder content on the microstructure, densification and hardness of tungsten/Al-Cu composite were studied by SEM, OM, XRD and Vickers hardness tester. The results show that doped tungsten powders can refine alloys structure, increase the uniformity of alloys and promote densification. When the mass ratio of doped tungsten powder to Al-Cu powder is 3%, the synthesized density and hardness of sample reach the highest values, i.e. 3.43 g/cm3 and HV 244.4.
2011, 28(6): 184-188.
doi: CNKI:11-1801/TB.20110720.1333.002
Abstract:
Diamond/Cu composites were fabricated by powder metallurgy in a hot-pressing furnace. The impacts of the titanium film, sintering temperature and volume fraction of diamond particles on the thermal conductivity of diamond/Cu composites were investigated. The results show that the titanium film can improve the interfacial soakage, decrease porosity and increase the thermal conductivity of diamond/Cu composites. When the sintering temperature was below 980 ℃, it can not make diamond/Cu composites get enough sintering driving force, resulting in low relative density and thermal conductivity. When the sintering temperature was above 980 ℃, it can cause the interfaces to break away because of the large difference of thermal expansion between diamond particles and copper, and can make the relative density and thermal conductivity of diamond/Cu composites decrease. The increasing of the diamond particle volume fraction can cause the copper to insufficiently fill the porosity between diamond particles, and decrease the relative density of diamond/Cu composites, which results in the increasing first and then decreasing of the thermal conductivity of diamond/Cu composites.
Diamond/Cu composites were fabricated by powder metallurgy in a hot-pressing furnace. The impacts of the titanium film, sintering temperature and volume fraction of diamond particles on the thermal conductivity of diamond/Cu composites were investigated. The results show that the titanium film can improve the interfacial soakage, decrease porosity and increase the thermal conductivity of diamond/Cu composites. When the sintering temperature was below 980 ℃, it can not make diamond/Cu composites get enough sintering driving force, resulting in low relative density and thermal conductivity. When the sintering temperature was above 980 ℃, it can cause the interfaces to break away because of the large difference of thermal expansion between diamond particles and copper, and can make the relative density and thermal conductivity of diamond/Cu composites decrease. The increasing of the diamond particle volume fraction can cause the copper to insufficiently fill the porosity between diamond particles, and decrease the relative density of diamond/Cu composites, which results in the increasing first and then decreasing of the thermal conductivity of diamond/Cu composites.
2011, 28(6): 189-193.
doi: CNKI:11-1801/TB.20110720.1418.023
Abstract:
The composition protective coatings on the surface of carbon steel crucible were prepared by aluminizing and high temperature chemical reaction. The relations between the thickness of reaction product layer and reaction temperature and time were investigated. The microstructures and phase composition of the coating layer were investigated by means of optics microscope and XRD. The experimental results show that the thicknesses of reaction product layers increase with the reaction temperature and time increasing. The composition coatings are composed of transition layer and reaction product layer. The constitution of transition layer are Fe3Al and small amount of Fe2Al5, Fe14Al86 and Al2O3. The reaction product layer are consisted of TiB2, MgO and small amount of Mg2TiO4, Mg2B2O5, Fe3Al, FeAl and Ti2B5.
The composition protective coatings on the surface of carbon steel crucible were prepared by aluminizing and high temperature chemical reaction. The relations between the thickness of reaction product layer and reaction temperature and time were investigated. The microstructures and phase composition of the coating layer were investigated by means of optics microscope and XRD. The experimental results show that the thicknesses of reaction product layers increase with the reaction temperature and time increasing. The composition coatings are composed of transition layer and reaction product layer. The constitution of transition layer are Fe3Al and small amount of Fe2Al5, Fe14Al86 and Al2O3. The reaction product layer are consisted of TiB2, MgO and small amount of Mg2TiO4, Mg2B2O5, Fe3Al, FeAl and Ti2B5.
2011, 28(6): 194-199.
doi: CNKI:11-1801/TB.20110720.1424.034
Abstract:
BG/BG-FHA composite coatings on the surface of Ti6Al4V alloy, which consist of a biological glass (BG) for the middle layer, BG and F doped hydroxyapatite (FHA) composite powder for the surface layer were prepared by electrophoretic deposition method. The phase composition, microstructure and adhesion of BG/BG-FHA composite coatings were analyzed by XRD, SEM, EDS and electronic universal material testing machine. The ameliorated heat-treatment process was obtained, and the in vitro biological activity was investigated by the soaking experiment in the simulated body fluid (SBF). The results show that a new phase Ti3(PO4)4 is generated in the interface between BG and Ti6Al4V base alloy after the BG/BG-FHA composite coatings were heat-treated appropriately, and the binding mode of the interface is chemically metallurgical bonding, which is higher than 20 MPa. Optimized heat treatment processing parameters are as follows: heat treatment temperature 750 ℃, holding time 12 min and furnace cooling. The bone-like calcium deficiency apatite, which grows like petal with several hundred nanometers in length, forms on the surface of BG/BG-FHA coating after soaking, showing excellent biological activity.
BG/BG-FHA composite coatings on the surface of Ti6Al4V alloy, which consist of a biological glass (BG) for the middle layer, BG and F doped hydroxyapatite (FHA) composite powder for the surface layer were prepared by electrophoretic deposition method. The phase composition, microstructure and adhesion of BG/BG-FHA composite coatings were analyzed by XRD, SEM, EDS and electronic universal material testing machine. The ameliorated heat-treatment process was obtained, and the in vitro biological activity was investigated by the soaking experiment in the simulated body fluid (SBF). The results show that a new phase Ti3(PO4)4 is generated in the interface between BG and Ti6Al4V base alloy after the BG/BG-FHA composite coatings were heat-treated appropriately, and the binding mode of the interface is chemically metallurgical bonding, which is higher than 20 MPa. Optimized heat treatment processing parameters are as follows: heat treatment temperature 750 ℃, holding time 12 min and furnace cooling. The bone-like calcium deficiency apatite, which grows like petal with several hundred nanometers in length, forms on the surface of BG/BG-FHA coating after soaking, showing excellent biological activity.
2011, 28(6): 200-207.
doi: CNKI:11-1801/TB.20110720.1418.020
Abstract:
Based on the meso-structure of plain weave composites, a micromechanical model was presented to simulate the progressive damage behavior of the plain weave composites that subjected to uniaxial tension. By considering the void defects scattered randomly throughout the matrix that induced during the manufacturing process, the Weibull distribution was implemented to simulate the defects by using Python language in the commercial finite element method (FEM) software ABAQUS standard. The failure criteria proposed by Linde was utilized to set up the progressive damage model, and the stress-strain relation of plain weave composites with defects was simulated. The voids in matrix were chosen for analysis the effect on tensile stress-strain curves of plain weave composite. The micromechanical model allows some detailed interpretation of plain weave composite with defects under warp directional tension, such as the evolution of damage fiber bundle. The numerical results show that the proposed model accurately captures the data from experiments, which demonstrates the validity of the present analytical model. Furthermore, the numerical model provides an alternate way to design and predict the mechanical properties of plain weave composites.
Based on the meso-structure of plain weave composites, a micromechanical model was presented to simulate the progressive damage behavior of the plain weave composites that subjected to uniaxial tension. By considering the void defects scattered randomly throughout the matrix that induced during the manufacturing process, the Weibull distribution was implemented to simulate the defects by using Python language in the commercial finite element method (FEM) software ABAQUS standard. The failure criteria proposed by Linde was utilized to set up the progressive damage model, and the stress-strain relation of plain weave composites with defects was simulated. The voids in matrix were chosen for analysis the effect on tensile stress-strain curves of plain weave composite. The micromechanical model allows some detailed interpretation of plain weave composite with defects under warp directional tension, such as the evolution of damage fiber bundle. The numerical results show that the proposed model accurately captures the data from experiments, which demonstrates the validity of the present analytical model. Furthermore, the numerical model provides an alternate way to design and predict the mechanical properties of plain weave composites.
2011, 28(6): 208-214.
doi: CNKI:11-1801/TB.20110720.1335.005
Abstract:
The governing partial differential equations (PDEs) were deduced from the asymptotically correct geometrically nonlinear theory to research the buckling and mode jumping behavior of clamped supported composite laminates with antisymmetric angle-ply under bi-axial compressive load. The two coupled fourth-order partial differential equations (PDEs), namely, the compatibility equation and the dynamic governing equation were transformed into a system of nonlinear ordinary differential equations (ODEs). Then a relatively simpler solution method was developed. The generalized Galerkin method was used to solve boundary value problems corresponding to antisymmetric angle-ply composite plates. The post-buckling patterns with different complexity before and after mode jumping were analyzed. An numerical example of 4-layers clamped composite laminates shows that the numerical results in the primary post-buckling region from the present method agree well with the finite element analysis (FEA). The FEA may lose its convergence when solution comes close the secondary point, while the analytic method can explore deeply into the post-buckling realm and accuratty capture the mode jumping phenomenon. Only the pure symmetric modes may be used to qualitatively predict the primary post-buckling branch, the secondary bifurcation load and the remote jumped branch of the composite laminates with antisymmetric angle-ply.
The governing partial differential equations (PDEs) were deduced from the asymptotically correct geometrically nonlinear theory to research the buckling and mode jumping behavior of clamped supported composite laminates with antisymmetric angle-ply under bi-axial compressive load. The two coupled fourth-order partial differential equations (PDEs), namely, the compatibility equation and the dynamic governing equation were transformed into a system of nonlinear ordinary differential equations (ODEs). Then a relatively simpler solution method was developed. The generalized Galerkin method was used to solve boundary value problems corresponding to antisymmetric angle-ply composite plates. The post-buckling patterns with different complexity before and after mode jumping were analyzed. An numerical example of 4-layers clamped composite laminates shows that the numerical results in the primary post-buckling region from the present method agree well with the finite element analysis (FEA). The FEA may lose its convergence when solution comes close the secondary point, while the analytic method can explore deeply into the post-buckling realm and accuratty capture the mode jumping phenomenon. Only the pure symmetric modes may be used to qualitatively predict the primary post-buckling branch, the secondary bifurcation load and the remote jumped branch of the composite laminates with antisymmetric angle-ply.
2011, 28(6): 215-222.
doi: CNKI:11-1801/TB.20110720.1424.033
Abstract:
Based on the assumption of hexagonal cross-section of yarns, a parameterized representative volume element (RVE) of 2D 1×1 biaxial braided composites was established with the consideration of the interaction and the cross-sectional deformation of the yarns. Coupled with the periodical boundary condition, the structural RVE was adopted to predict the elastic properties of the braided composites by the finite element method. The influences of braid angle and fiber volume fraction on the effective elastic constants were studied, and the overall stress distribution nephogram of the RVE under typical loads were obtained and analyzed. The results indicate tha the spatial configuration and the mutual squeezing of the yarns are validly reflected in the RVE, and the structural RVE with different structural parameters can be quickly regenerated, and the prediction results coincide with the experimental data well. The finite element model provides reasonable stress filed, which establishes a good foundation for structure optimization and failure analysis of the 2D braided composites.
Based on the assumption of hexagonal cross-section of yarns, a parameterized representative volume element (RVE) of 2D 1×1 biaxial braided composites was established with the consideration of the interaction and the cross-sectional deformation of the yarns. Coupled with the periodical boundary condition, the structural RVE was adopted to predict the elastic properties of the braided composites by the finite element method. The influences of braid angle and fiber volume fraction on the effective elastic constants were studied, and the overall stress distribution nephogram of the RVE under typical loads were obtained and analyzed. The results indicate tha the spatial configuration and the mutual squeezing of the yarns are validly reflected in the RVE, and the structural RVE with different structural parameters can be quickly regenerated, and the prediction results coincide with the experimental data well. The finite element model provides reasonable stress filed, which establishes a good foundation for structure optimization and failure analysis of the 2D braided composites.
2011, 28(6): 223-229.
doi: CNKI:11-1801/TB.20110720.1418.021
Abstract:
Considering the effect of adhesive layers between adjacent yarns, a new FEM model of representative unit cell was established, which more really simulates the inner meso-structures of the 3D 4-directional braided composites. The boundary conditions and constrain conditions of the unit cell model were discussed and the effective elastic properties parameters were obtained by FEM calculation. The calculation results by the model agree well with the experimental results. The relations of the effective elastic properties varied with different braiding angles and fiber volume fractions are concluded by analyzing the results. The distribution of the stress in the composites was determined, which provide data for the strength calculations of the composites.
Considering the effect of adhesive layers between adjacent yarns, a new FEM model of representative unit cell was established, which more really simulates the inner meso-structures of the 3D 4-directional braided composites. The boundary conditions and constrain conditions of the unit cell model were discussed and the effective elastic properties parameters were obtained by FEM calculation. The calculation results by the model agree well with the experimental results. The relations of the effective elastic properties varied with different braiding angles and fiber volume fractions are concluded by analyzing the results. The distribution of the stress in the composites was determined, which provide data for the strength calculations of the composites.
2011, 28(6): 230-236.
doi: CNKI:11-1801/TB.20110720.1341.017
Abstract:
In order to solve the convergence difficulties caused by contaction in the analysis of composite bolted joints, the user-defined cohesive element with special constitutive behavior was developed to model contaction. This element could only transfer the pressure, but not the tension. The user-defined cohesive element was placed between the two interfaces in order to transfer the contact pressure, so that it becomes a way to guarantee the relation of coordination between the deformation of the two interfaces. Meanwhile, a three-dimensional progressive damage model was developed to model composite laminates with a single bolted joint. The stiffness reduction associated with damage due to compressive loads was improved based on the method of the document. The contact technology based on the user-defined cohesive element and the improved method of the stiffness reduction were used to predict strength of the model. At last, experimental results concerning the bearing strength were obtained and compared with the predictions, from which a good agreement was observed.
In order to solve the convergence difficulties caused by contaction in the analysis of composite bolted joints, the user-defined cohesive element with special constitutive behavior was developed to model contaction. This element could only transfer the pressure, but not the tension. The user-defined cohesive element was placed between the two interfaces in order to transfer the contact pressure, so that it becomes a way to guarantee the relation of coordination between the deformation of the two interfaces. Meanwhile, a three-dimensional progressive damage model was developed to model composite laminates with a single bolted joint. The stiffness reduction associated with damage due to compressive loads was improved based on the method of the document. The contact technology based on the user-defined cohesive element and the improved method of the stiffness reduction were used to predict strength of the model. At last, experimental results concerning the bearing strength were obtained and compared with the predictions, from which a good agreement was observed.
2011, 28(6): 237-244.
doi: CNKI:11-1801/TB.20110720.1422.029
Abstract:
The nonlinear dynamic responses and the dynamic stress of a circular plate in thermal environment were studied. The effect of geometric nonlinearity and temperature-dependent material properties were both taken into account. The material properties of the functionally graded plate were assumed to vary continuously through the thickness according to a power law distribution of the volume fraction of the constituents. Using the principle of virtual work, the nonlinear partial differential equations of functionally graded plate subjected to transverse harmonic excitation and thermal loads were derived. For the circular plate with clamped immovable edge, the Duffing nonlinear forced vibration equation was deduced by using Galerkin method. Through the numerical example given in the paper, the bifurcation diagram for material's volume fraction index, phasepotrait, Poincare map and the dynamic stress variation were plotted. Besides, the influences of materials volume fraction index and thermal loads on the nonlinear dynamic response of functionally graded plate were discussed. The results show that periodic, multiplier periodic and chaotic motions exist for the functionally graded plate with the change of the volume fraction index. The dynamic stress at the center of the circular plate varies sharply when the system appears bifurcation or chaos and becomes unpredictable when the system appears chaotic motions.
The nonlinear dynamic responses and the dynamic stress of a circular plate in thermal environment were studied. The effect of geometric nonlinearity and temperature-dependent material properties were both taken into account. The material properties of the functionally graded plate were assumed to vary continuously through the thickness according to a power law distribution of the volume fraction of the constituents. Using the principle of virtual work, the nonlinear partial differential equations of functionally graded plate subjected to transverse harmonic excitation and thermal loads were derived. For the circular plate with clamped immovable edge, the Duffing nonlinear forced vibration equation was deduced by using Galerkin method. Through the numerical example given in the paper, the bifurcation diagram for material's volume fraction index, phasepotrait, Poincare map and the dynamic stress variation were plotted. Besides, the influences of materials volume fraction index and thermal loads on the nonlinear dynamic response of functionally graded plate were discussed. The results show that periodic, multiplier periodic and chaotic motions exist for the functionally graded plate with the change of the volume fraction index. The dynamic stress at the center of the circular plate varies sharply when the system appears bifurcation or chaos and becomes unpredictable when the system appears chaotic motions.
2011, 28(6): 245-251.
doi: CNKI:11-1801/TB.20110720.1340.012
Abstract:
The tensile, compressive and shear property of 4D in-plain C/C composites in each direction were studied by macroscopic mechanical experiment. ARAMIS incontact strain test system was successfully used to solve the incompatible problems produced in using strain gauge to test the properties. The results show that the properties of the 4D in-plain C/C composites exhibit anisotropy, double modules and the nonlinear characteristics. Under tensile load, the specimens show crack delamination growth along the radical direction, and show carbon rod pulled out along the axial direction. Under compress load, the specimens show shear failure caused by the increment of ductility. It embodies brittle in tensile and pseudoplastic in compress. The specimens show delamination failure in xz plane under shear load, and fiber bundle pulled out in xy plane.
The tensile, compressive and shear property of 4D in-plain C/C composites in each direction were studied by macroscopic mechanical experiment. ARAMIS incontact strain test system was successfully used to solve the incompatible problems produced in using strain gauge to test the properties. The results show that the properties of the 4D in-plain C/C composites exhibit anisotropy, double modules and the nonlinear characteristics. Under tensile load, the specimens show crack delamination growth along the radical direction, and show carbon rod pulled out along the axial direction. Under compress load, the specimens show shear failure caused by the increment of ductility. It embodies brittle in tensile and pseudoplastic in compress. The specimens show delamination failure in xz plane under shear load, and fiber bundle pulled out in xy plane.
