2011 Vol. 28, No. 3
2011, 28(3): 1-5.
Abstract:
The ramie fabric was treated with two different types of flame retardants, namely phosphate type and nitrogen-phosphorous type, and composed with phenolic resin to prepare ramie/phenolic resin laminate. The flame retardancy of the laminate treated by nitrogen-phosphorous type flame retardant is better than that treated by phosphate type flame retardant. The limiting oxygen index (LOI) of the laminate with nitrogen-phosphorous type treatment increases from 25.2% to 39.1%, and reaches the V0 level in UL94 vertical burning test, while LOI of the laminate with the phosphate type treatment only increases to 27.8%. Cone calorimeter tests show that the laminates with the nitrogen-phosphorous type treatment have increased char residue, extended ignition time and decreased peak heat release rate and average smoke density. It is also found that the mechanical properties of the laminates are not changed because of the little damage on the fiber structure of ramie fabric with the flame retardant treatment.
The ramie fabric was treated with two different types of flame retardants, namely phosphate type and nitrogen-phosphorous type, and composed with phenolic resin to prepare ramie/phenolic resin laminate. The flame retardancy of the laminate treated by nitrogen-phosphorous type flame retardant is better than that treated by phosphate type flame retardant. The limiting oxygen index (LOI) of the laminate with nitrogen-phosphorous type treatment increases from 25.2% to 39.1%, and reaches the V0 level in UL94 vertical burning test, while LOI of the laminate with the phosphate type treatment only increases to 27.8%. Cone calorimeter tests show that the laminates with the nitrogen-phosphorous type treatment have increased char residue, extended ignition time and decreased peak heat release rate and average smoke density. It is also found that the mechanical properties of the laminates are not changed because of the little damage on the fiber structure of ramie fabric with the flame retardant treatment.
2011, 28(3): 6-12.
Abstract:
The high-strength buoyancy material was synthesized with adhesive matrix of epoxy resin and filler of hollow glass microsphere (HGM) activated by silane coupling agent. The characteristics of HGM treated with silane were analyzed by XRD and FRIR. The effect of type and content of HGM on performance of buoyancy material was investigated through density test and uniaxial static compression test. The fracture characteristics and water absorption of buoyancy material were studied by SEM and water absorption test. The results show that the structure of HGM is amorphous. Silane is grafted on the surface of HGM after activation. HGM is perfectly combined with epoxy resin and there is no gap between their interface. The high specific compression strength of HGM is beneficial to the performance of buoyancy material. The density, compression strength and specific compression strength of buoyancy material are 0.645~0.850 g/cm3, 60~93 MPa and 92~112 MPa·cm3·g-1, respectively. On the fracture surface of buoyancy material with less HGM, HGM is destroyed and there is tailing in the matrix, while the damage degree of HGM increases with the increase of HGM content and finally HGM is destroyed thoroughly. The water absorption of buoyancy material is low.
The high-strength buoyancy material was synthesized with adhesive matrix of epoxy resin and filler of hollow glass microsphere (HGM) activated by silane coupling agent. The characteristics of HGM treated with silane were analyzed by XRD and FRIR. The effect of type and content of HGM on performance of buoyancy material was investigated through density test and uniaxial static compression test. The fracture characteristics and water absorption of buoyancy material were studied by SEM and water absorption test. The results show that the structure of HGM is amorphous. Silane is grafted on the surface of HGM after activation. HGM is perfectly combined with epoxy resin and there is no gap between their interface. The high specific compression strength of HGM is beneficial to the performance of buoyancy material. The density, compression strength and specific compression strength of buoyancy material are 0.645~0.850 g/cm3, 60~93 MPa and 92~112 MPa·cm3·g-1, respectively. On the fracture surface of buoyancy material with less HGM, HGM is destroyed and there is tailing in the matrix, while the damage degree of HGM increases with the increase of HGM content and finally HGM is destroyed thoroughly. The water absorption of buoyancy material is low.
2011, 28(3): 13-19.
Abstract:
The carbon nanotube (CNT)-glass fiber/epoxy resin laminates were prepared by traditional vacuum assisted resin infusion molding (VARIM) and double vacuum assisted resin infusion molding (DVARIM), respectively. The defects of the laminates processed with the two methods were examined, and the mechanical properties including flexural property and interlaminar shear strength (ILSS) were measured. The distribution and the enhancement mechanism of CNT in the laminates with DVARIM were studied by the measurement of the resin properties and the observation of the fiber/resin interfacial bonding. It shows that, compared with traditional VARIM, the defects in the fiber bundles decrease because the spaces within fibers increase and the resin infiltration improves in DVARIM. The mechanical properties of the laminates are enhanced by adding 0.05% mass fraction of acidulated CNT, especially for the laminates processed by DVARIM. In addition, the infusion process influences the distribution of CNT in the laminates, and further changes the effects of CNT on the interface bonding of fiber/resin, which is dependent on the compactness of the fabric.
The carbon nanotube (CNT)-glass fiber/epoxy resin laminates were prepared by traditional vacuum assisted resin infusion molding (VARIM) and double vacuum assisted resin infusion molding (DVARIM), respectively. The defects of the laminates processed with the two methods were examined, and the mechanical properties including flexural property and interlaminar shear strength (ILSS) were measured. The distribution and the enhancement mechanism of CNT in the laminates with DVARIM were studied by the measurement of the resin properties and the observation of the fiber/resin interfacial bonding. It shows that, compared with traditional VARIM, the defects in the fiber bundles decrease because the spaces within fibers increase and the resin infiltration improves in DVARIM. The mechanical properties of the laminates are enhanced by adding 0.05% mass fraction of acidulated CNT, especially for the laminates processed by DVARIM. In addition, the infusion process influences the distribution of CNT in the laminates, and further changes the effects of CNT on the interface bonding of fiber/resin, which is dependent on the compactness of the fabric.
2011, 28(3): 20-26.
Abstract:
A multi-walled carbon nanotubes (MWCNTs)/epoxy resin adhesive was prepared with the EP resin and surface hydroxylating MWCNTs by a mass ratio of 100∶0.1 using ultrasonic dispersion method. The effects of two kinds of silane couple agents KH550 and KH560 on the modified degree of the MWCNTs were investigated. The effects of the MWCNTs on curing behavior and rheological property of the adhesives were studied by means of FTIR, DSC, DMA and rheometer. Based on the observation of fracture cross-section, the influences of MWCNTs on the shear strength by tension loading and impact strength were analyzed. The experimental results show that the silane couple agents have the condensation reaction with－OH on the surface of MWCNTs, and can improve the compatibility between MWCNTs and epoxy resin. Thus, the silane couple agents influence the curing reaction and viscosity-shear rate curves of the adhesives. The MWCNTs modified by KH550 can obviously improve the bond property between the adhesives and metal, and the Al-Al shear strengths by tension loading are raised by 46.4% compared with the one without MWCNTs. The impact fracture cross-sections of the adhesives with MWCNTs are much rougher and have larger areas of crack. In addition, the impact strength of the adhesive with MWCNTs+KH550 is raised by 44.1% compared with the one without MWCNTs, indicating that the interphase property between MWCNTs and epoxy resin is very important for the toughening effect of the MWCNTs.
A multi-walled carbon nanotubes (MWCNTs)/epoxy resin adhesive was prepared with the EP resin and surface hydroxylating MWCNTs by a mass ratio of 100∶0.1 using ultrasonic dispersion method. The effects of two kinds of silane couple agents KH550 and KH560 on the modified degree of the MWCNTs were investigated. The effects of the MWCNTs on curing behavior and rheological property of the adhesives were studied by means of FTIR, DSC, DMA and rheometer. Based on the observation of fracture cross-section, the influences of MWCNTs on the shear strength by tension loading and impact strength were analyzed. The experimental results show that the silane couple agents have the condensation reaction with－OH on the surface of MWCNTs, and can improve the compatibility between MWCNTs and epoxy resin. Thus, the silane couple agents influence the curing reaction and viscosity-shear rate curves of the adhesives. The MWCNTs modified by KH550 can obviously improve the bond property between the adhesives and metal, and the Al-Al shear strengths by tension loading are raised by 46.4% compared with the one without MWCNTs. The impact fracture cross-sections of the adhesives with MWCNTs are much rougher and have larger areas of crack. In addition, the impact strength of the adhesive with MWCNTs+KH550 is raised by 44.1% compared with the one without MWCNTs, indicating that the interphase property between MWCNTs and epoxy resin is very important for the toughening effect of the MWCNTs.
2011, 28(3): 27-34.
Abstract:
N-isopropylacrylamide(NIPAM) and acrylic acid (AA)copolymer microspheres with various compositions were prepared by a reverse suspension emulsion technique. The microspheres were employed as microreactors for the synthesis of fluorescence composite microspheres by two different methods. In this way, several uniform of P(NIPAM-co-AA)-Alq3 fluorescence composite microspheres were prepared. The surface functionalized P(NIPAM-co-AA)-Alq3-SiO2 fluorescence composite microspheres was prepared by decorating the surface with the tetraethoxy-silicone(TEOS). The fluorescence composite microspheres were characterized by SEM, IR, FM and XRD. The results indicate uniform particle size fluorescent composite microspheres are obtained with high efficiency fluorescent light and high specific surface area. It might be expected that this functional material can be applied for high-throughput screening assays and recognition of biomacromolecules in biological medical fields.
N-isopropylacrylamide(NIPAM) and acrylic acid (AA)copolymer microspheres with various compositions were prepared by a reverse suspension emulsion technique. The microspheres were employed as microreactors for the synthesis of fluorescence composite microspheres by two different methods. In this way, several uniform of P(NIPAM-co-AA)-Alq3 fluorescence composite microspheres were prepared. The surface functionalized P(NIPAM-co-AA)-Alq3-SiO2 fluorescence composite microspheres was prepared by decorating the surface with the tetraethoxy-silicone(TEOS). The fluorescence composite microspheres were characterized by SEM, IR, FM and XRD. The results indicate uniform particle size fluorescent composite microspheres are obtained with high efficiency fluorescent light and high specific surface area. It might be expected that this functional material can be applied for high-throughput screening assays and recognition of biomacromolecules in biological medical fields.
2011, 28(3): 27-34.
Abstract:
N-isopropylacrylamide(NIPAM) and acrylic acid (AA)copolymer microspheres with various compositions were prepared by a reverse suspension emulsion technique. The microspheres were employed as microreactors for the synthesis of fluorescence composite microspheres by two different methods. In this way, several uniform of P(NIPAM-co-AA)-Alq3 fluorescence composite microspheres were prepared. The surface functionalized P(NIPAM-co-AA)-Alq3-SiO2 fluorescence composite microspheres was prepared by decorating the surface with the tetraethoxy-silicone(TEOS). The fluorescence composite microspheres were characterized by SEM, IR, FM and XRD. The results indicate uniform particle size fluorescent composite microspheres are obtained with high efficiency fluorescent light and high specific surface area. It might be expected that this functional material can be applied for high-throughput screening assays and recognition of biomacromolecules in biological medical fields.
N-isopropylacrylamide(NIPAM) and acrylic acid (AA)copolymer microspheres with various compositions were prepared by a reverse suspension emulsion technique. The microspheres were employed as microreactors for the synthesis of fluorescence composite microspheres by two different methods. In this way, several uniform of P(NIPAM-co-AA)-Alq3 fluorescence composite microspheres were prepared. The surface functionalized P(NIPAM-co-AA)-Alq3-SiO2 fluorescence composite microspheres was prepared by decorating the surface with the tetraethoxy-silicone(TEOS). The fluorescence composite microspheres were characterized by SEM, IR, FM and XRD. The results indicate uniform particle size fluorescent composite microspheres are obtained with high efficiency fluorescent light and high specific surface area. It might be expected that this functional material can be applied for high-throughput screening assays and recognition of biomacromolecules in biological medical fields.
2011, 28(3): 42-49.
Abstract:
Trifunctional polysiloxane flame retardants were synthesized through hydrolysis condensation reaction. The influence of the Karstedt catalyst (KC) on the polysiloxane/PC composite and the flame retarding mechanism were studied using limiting oxygen index (LOI) test, cone calorimeter, TGA, PY-GC/MS and SEM. The results show that the KC promotes the crosslinking of the trifunctional polysiloxane containing vinyl groups and increases the thermal stability of the polysiloxane/PC composite. Furthermore, KC restrains the release of the combustion heat of the polysiloxane/PC composite, which delays the emission of smoke, CO and CO2 and reduces the peak of the emission of smoke. Thus the flame retardancy of the polysiloxane/PC composite is enhanced and the danger for combustion is reduced. However, the effect of KC on the LOI of the polysiloxane/PC composite is quite complicated. The LOI of the polysiloxane/PC composite with KC depends not only on the amount of the char, but also on the structure of the char layer. KC could promote the formation of more compact and uniform char layer of the polysiloxane/PC composite during the combustion, thus the LOI of the composite is increased.
Trifunctional polysiloxane flame retardants were synthesized through hydrolysis condensation reaction. The influence of the Karstedt catalyst (KC) on the polysiloxane/PC composite and the flame retarding mechanism were studied using limiting oxygen index (LOI) test, cone calorimeter, TGA, PY-GC/MS and SEM. The results show that the KC promotes the crosslinking of the trifunctional polysiloxane containing vinyl groups and increases the thermal stability of the polysiloxane/PC composite. Furthermore, KC restrains the release of the combustion heat of the polysiloxane/PC composite, which delays the emission of smoke, CO and CO2 and reduces the peak of the emission of smoke. Thus the flame retardancy of the polysiloxane/PC composite is enhanced and the danger for combustion is reduced. However, the effect of KC on the LOI of the polysiloxane/PC composite is quite complicated. The LOI of the polysiloxane/PC composite with KC depends not only on the amount of the char, but also on the structure of the char layer. KC could promote the formation of more compact and uniform char layer of the polysiloxane/PC composite during the combustion, thus the LOI of the composite is increased.
2011, 28(3): 50-55.
Abstract:
A thermal expansion process with silicone rubber was adopted to prepare carbon fiber/bismaleimide resin composite laminates. By means of a designed processing mold and a resin pressure online measuring system, the thermal expansion pressure and the resin pressure in the prepreg stack during the process were measured and analyzed. The effects of the process gap and temperature distribution were investigated, and the consolidation degrees of cured laminates under different process conditions were studied using the micrographs of laminates. The results show that the resin pressure in prepreg stack during thermal expansion process can be measured using the resin pressure online measuring system. The process gap and the temperature distribution inside the silicon rubber strongly influence the resin pressure and the thermal expansion pressure. When the process gap is reasonable, the trend and the variation degree of the thermal expansion pressure and the resin pressure before gelation are almost consistent in zero-bleeding process. The cured laminates are compact with uniform thickness. By adding the temperature platform to reduce the temperature distribution inside the silicone rubber, the increasing speed of thermal expansion pressure can be decreased.
A thermal expansion process with silicone rubber was adopted to prepare carbon fiber/bismaleimide resin composite laminates. By means of a designed processing mold and a resin pressure online measuring system, the thermal expansion pressure and the resin pressure in the prepreg stack during the process were measured and analyzed. The effects of the process gap and temperature distribution were investigated, and the consolidation degrees of cured laminates under different process conditions were studied using the micrographs of laminates. The results show that the resin pressure in prepreg stack during thermal expansion process can be measured using the resin pressure online measuring system. The process gap and the temperature distribution inside the silicon rubber strongly influence the resin pressure and the thermal expansion pressure. When the process gap is reasonable, the trend and the variation degree of the thermal expansion pressure and the resin pressure before gelation are almost consistent in zero-bleeding process. The cured laminates are compact with uniform thickness. By adding the temperature platform to reduce the temperature distribution inside the silicone rubber, the increasing speed of thermal expansion pressure can be decreased.
2011, 28(3): 56-62.
Abstract:
The 3D needled C/SiC brake materials were prepared by chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI) method. The thermal physical properties of the 3D needled C/SiC brake materials were systematically investigated. The results indicate that the thermal expansion coefficients (CTE) of the C/SiC brake materials increase with the temperature increasing, but it shows regular fluctuation. At the same temperature, the CTE perpendicular to friction surface is far bigger than that parallel to friction surface. From room temperature to 1300 ℃, the average CTE parallel and perpendicular to friction surface are 1.75×10-6 K-1 and 4.41×10-6 K-1, respectively. The specific heat capacity of the C/SiC brake materials increases with the temperature increasing, but the rate of the specific heat capacity rise decreases gradually. From 100 ℃ to 1400 ℃, the specific heat capacity increases from 1.14 J/(g·K) to 1.92 J/(g·K). The thermal diffusivity of the C/SiC brake materials decreases to constant with the temperature increasing. The thermal diffusivity parallel to friction surface is obviously larger than that perpendicular to friction surface.
The 3D needled C/SiC brake materials were prepared by chemical vapor infiltration (CVI) combined with reactive melt infiltration (RMI) method. The thermal physical properties of the 3D needled C/SiC brake materials were systematically investigated. The results indicate that the thermal expansion coefficients (CTE) of the C/SiC brake materials increase with the temperature increasing, but it shows regular fluctuation. At the same temperature, the CTE perpendicular to friction surface is far bigger than that parallel to friction surface. From room temperature to 1300 ℃, the average CTE parallel and perpendicular to friction surface are 1.75×10-6 K-1 and 4.41×10-6 K-1, respectively. The specific heat capacity of the C/SiC brake materials increases with the temperature increasing, but the rate of the specific heat capacity rise decreases gradually. From 100 ℃ to 1400 ℃, the specific heat capacity increases from 1.14 J/(g·K) to 1.92 J/(g·K). The thermal diffusivity of the C/SiC brake materials decreases to constant with the temperature increasing. The thermal diffusivity parallel to friction surface is obviously larger than that perpendicular to friction surface.
2011, 28(3): 63-68.
Abstract:
Using fabric of silica fiber and silica sol as the raw materials, the silica fiber reinforced silica based composite materials (SiO2f/SiO2) were fabricated by the sol-gel method, and the silica fiber reinforced silica and boron nitride based composite materials (SiO2f/SiO2-BN) were prepared via the urea route. The mechanical properties and dielectric properties of the composites were investigated. The results show that the density of the composites increases with the increase of the cycles, while the densification becomes slow gradually. After three cycles, the density of the SiO2f/SiO2-BN composites reaches 1.81 g/cm3. The flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, which increase by 12.1% and 76.3% compared with SiO2f/SiO2 composites, respectively. The interfacial combination between fiber and matrix is good and lots of fiber pull-out can be observed on the fracture surface, which suggests a good toughness. The composite has excellent dielectric properties with the dielectric constant and loss tangent being 3.32 and 0.004, respectively.
Using fabric of silica fiber and silica sol as the raw materials, the silica fiber reinforced silica based composite materials (SiO2f/SiO2) were fabricated by the sol-gel method, and the silica fiber reinforced silica and boron nitride based composite materials (SiO2f/SiO2-BN) were prepared via the urea route. The mechanical properties and dielectric properties of the composites were investigated. The results show that the density of the composites increases with the increase of the cycles, while the densification becomes slow gradually. After three cycles, the density of the SiO2f/SiO2-BN composites reaches 1.81 g/cm3. The flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, which increase by 12.1% and 76.3% compared with SiO2f/SiO2 composites, respectively. The interfacial combination between fiber and matrix is good and lots of fiber pull-out can be observed on the fracture surface, which suggests a good toughness. The composite has excellent dielectric properties with the dielectric constant and loss tangent being 3.32 and 0.004, respectively.
2011, 28(3): 69-73.
Abstract:
SiC/Ti3SiC2 composites were prepared by reactive hot pressing method. The effects of hot pressing temperature, the content and particle size of SiC on the phase constituent, mechanical properties and the behavior of stress-strain of the composites were investigated. The results show that the hot pressing temperature influences the phase constituent of SiC/Ti3SiC2 composites. The flexural strength and fracture toughness of composites increase with the increase of hot pressing temperature. With the increasing the SiC content, the flexural strength and fracture toughness of composites increase. When the mass fraction of SiC is 30%, the flexural strength and fracture toughness of SiC/Ti3SiC2 composite are 371 MPa and 6.9 MPa·m1/2 , respectively. However, when the mass fraction of SiC content reaches 50%, the flexural strength and fracture toughness of composites decrease due to high porosity in the composites. The flexural strength and fracture toughness of composites increase with the particle size of SiC. SiC/Ti3SiC2 composites are non-brittle at room temperature.
SiC/Ti3SiC2 composites were prepared by reactive hot pressing method. The effects of hot pressing temperature, the content and particle size of SiC on the phase constituent, mechanical properties and the behavior of stress-strain of the composites were investigated. The results show that the hot pressing temperature influences the phase constituent of SiC/Ti3SiC2 composites. The flexural strength and fracture toughness of composites increase with the increase of hot pressing temperature. With the increasing the SiC content, the flexural strength and fracture toughness of composites increase. When the mass fraction of SiC is 30%, the flexural strength and fracture toughness of SiC/Ti3SiC2 composite are 371 MPa and 6.9 MPa·m1/2 , respectively. However, when the mass fraction of SiC content reaches 50%, the flexural strength and fracture toughness of composites decrease due to high porosity in the composites. The flexural strength and fracture toughness of composites increase with the particle size of SiC. SiC/Ti3SiC2 composites are non-brittle at room temperature.
2011, 28(3): 74-79.
Abstract:
Two kinds of BaO-Al2O3-SiO2 (BAS) glass-ceramics with different soften points and thermal expansion coefficients were employed to prepare three kinds of gradient coatings for carbon fiber reinforced silicon carbide(Cf/SiC) composite. These coatings were fabricated with slurry deposition combined dipping method and multi-co-firing technology. These BAS glass-ceramics based coatings were integrated and defect-free. The coatings and the composites bind tightly, which can improve the anti-oxidation performance of the coated Cf/SiC composite. All coating systems can protect Cf/SiC composite from oxidation. The graded coatings protect Cf/SiC composite markedly, and the mass loss rate and mass loss of coated composites are reduced greatly within 1200~1350 ℃. Compared with uncoated composite, the mass loss of the coated composite is reduced by 1/2~2/3, and the reminant bending strength is enhanced 7~15 times after 600 thermal shock cycles in the experimental range.
Two kinds of BaO-Al2O3-SiO2 (BAS) glass-ceramics with different soften points and thermal expansion coefficients were employed to prepare three kinds of gradient coatings for carbon fiber reinforced silicon carbide(Cf/SiC) composite. These coatings were fabricated with slurry deposition combined dipping method and multi-co-firing technology. These BAS glass-ceramics based coatings were integrated and defect-free. The coatings and the composites bind tightly, which can improve the anti-oxidation performance of the coated Cf/SiC composite. All coating systems can protect Cf/SiC composite from oxidation. The graded coatings protect Cf/SiC composite markedly, and the mass loss rate and mass loss of coated composites are reduced greatly within 1200~1350 ℃. Compared with uncoated composite, the mass loss of the coated composite is reduced by 1/2~2/3, and the reminant bending strength is enhanced 7~15 times after 600 thermal shock cycles in the experimental range.
2011, 28(3): 80-84.
Abstract:
7% mass fraction of SiO2and 2%, 4% and 6% mass fraction of Na2B4O7 were added as additives into the system of A1-Fe2O3 to examine their effects on the microstructures and properties of ceramic compound pipes made by centrifugal SHS (self-propagating high temperature synthesis) process. It was found that ceramic layer is mainly composed of α-Al2O3, FeAl2O4, Al2SiO5 and B2O3 by XRD analysis. The surfaces on ceramic layer by SEM are much denser than that without additives, and Fe is also found in ceramic layer combined with the EDS analysis. The results show that inner ceramic layer and transition iron layer combine well without any gap observed by metallurgical microscope. It is also found that the shearing strength of the ceramic layer and crushing strength of the composite pipe under 7%SiO2+4%Na2B4O7(mass fraction) are 22 MPa and 430 MPa, respectively, which are 240% and 22.8% greater than those without additives.
7% mass fraction of SiO2and 2%, 4% and 6% mass fraction of Na2B4O7 were added as additives into the system of A1-Fe2O3 to examine their effects on the microstructures and properties of ceramic compound pipes made by centrifugal SHS (self-propagating high temperature synthesis) process. It was found that ceramic layer is mainly composed of α-Al2O3, FeAl2O4, Al2SiO5 and B2O3 by XRD analysis. The surfaces on ceramic layer by SEM are much denser than that without additives, and Fe is also found in ceramic layer combined with the EDS analysis. The results show that inner ceramic layer and transition iron layer combine well without any gap observed by metallurgical microscope. It is also found that the shearing strength of the ceramic layer and crushing strength of the composite pipe under 7%SiO2+4%Na2B4O7(mass fraction) are 22 MPa and 430 MPa, respectively, which are 240% and 22.8% greater than those without additives.
2011, 28(3): 85-89.
Abstract:
An advanced ultrahigh temperature Nb-Si based composite with a high content of Cr was prepared by directional solidification. The microstructure and phases were investigated under the condition of different melting temperatures or different solidification rates. The results reveal that the microstructure is composed of Nbss, α-Nb5Si3, NbCr2 phases and a small amount of (Nbss+ Nb5Si3) eutectic. The composites phase composition has not been changed by directional solidification. The Nbss phase appears like grain and the Nb5Si3 phase is randomly distributed in the block or short lath at 1550 ℃. With the increase of the melting temperature, the Nbss phase changes from large grains to dendrites, while the Nb5Si3 phase undergoes an evolution from block to batten morphologies. The composite microstructure is fined obviously and the directional effects enhance as the increase of the solidification rates. The excellent directionally solidified microstructure is obtained when the solidifying rate is 18 mm/min, and the Nb5Si3 phase is column shape with good orientation.
An advanced ultrahigh temperature Nb-Si based composite with a high content of Cr was prepared by directional solidification. The microstructure and phases were investigated under the condition of different melting temperatures or different solidification rates. The results reveal that the microstructure is composed of Nbss, α-Nb5Si3, NbCr2 phases and a small amount of (Nbss+ Nb5Si3) eutectic. The composites phase composition has not been changed by directional solidification. The Nbss phase appears like grain and the Nb5Si3 phase is randomly distributed in the block or short lath at 1550 ℃. With the increase of the melting temperature, the Nbss phase changes from large grains to dendrites, while the Nb5Si3 phase undergoes an evolution from block to batten morphologies. The composite microstructure is fined obviously and the directional effects enhance as the increase of the solidification rates. The excellent directionally solidified microstructure is obtained when the solidifying rate is 18 mm/min, and the Nb5Si3 phase is column shape with good orientation.
2011, 28(3): 90-95.
Abstract:
Composite electrode materials with 60% mass fraction of RuO2 loading on activated carbon (AC) were prepared by a modified colloidal method, then it was annealed at different temperatures for 6h.The cyclic voltammetry, constant charge-discharge and alternating impedance of the composite electrode materials were measured by electrochemical working station. The morphology and structure of the composites annealed at different temperatures were characterized by SEM, EDS and XRD. The results illustrate that the specific capacitance is the best at 240 ℃ and its value is 445 F/g with good charge-discharge performance. The impedance value gradually decreases with the increase of annealing temperature under 240 ℃ and increases slightly beyond 240 ℃. Morphology of composite annealed at 240 ℃ is fine and homogeneous hydrated RuO2 particle distributed in the carbon matrix. The RuO2 of complexes remains amorphous, and changes to the crystal phase when the temperature is beyond 270 ℃. Electrochemical properties of the composite electrode prepared by the modified colloidal method is good when it is annealed at 240 ℃.
Composite electrode materials with 60% mass fraction of RuO2 loading on activated carbon (AC) were prepared by a modified colloidal method, then it was annealed at different temperatures for 6h.The cyclic voltammetry, constant charge-discharge and alternating impedance of the composite electrode materials were measured by electrochemical working station. The morphology and structure of the composites annealed at different temperatures were characterized by SEM, EDS and XRD. The results illustrate that the specific capacitance is the best at 240 ℃ and its value is 445 F/g with good charge-discharge performance. The impedance value gradually decreases with the increase of annealing temperature under 240 ℃ and increases slightly beyond 240 ℃. Morphology of composite annealed at 240 ℃ is fine and homogeneous hydrated RuO2 particle distributed in the carbon matrix. The RuO2 of complexes remains amorphous, and changes to the crystal phase when the temperature is beyond 270 ℃. Electrochemical properties of the composite electrode prepared by the modified colloidal method is good when it is annealed at 240 ℃.
2011, 28(3): 96-102.
Abstract:
Titanate nanowhiskers were synthesized by a hydrothermal method with nano-sized titanate dioxide rutile as the titanate source, and then the modified titanate nanowhiskers were obtained by loading tributyl phosphate (TBP) on the surface of the titanate nanowhiskers. The morphology and structure of the titanate nanowhiskers and the modified titanate nanowhiskers were characterized by SEM, TEM and FTIR. The two nanomaterials were applied for the adsorption of uranium ion, and the adsorption kinetics and the adsorption isotherm model of the modified titanate nanowhiskers were studied. SEM photographs show that the particle size of the titanate nanowhiskers ranges from 80 nm to 100 nm. Uranium adsorption studies demonstrate that modified titanate nanowhiskers exhibite higher adsorption capacity in 3 mol/L NO-3 medium than titanate nanowhiskers. Adsorption kinetics of uranium on modified titanate nanowhiskers is in accordance with quasi-second order kinetic model, and adsorption isotherm model consistents with Langmuir and Freundlich isotherm model. The modified titanate nanowhiskers were applied to recover low concentration uranium from tap water, and satisfactory results were achieved.
Titanate nanowhiskers were synthesized by a hydrothermal method with nano-sized titanate dioxide rutile as the titanate source, and then the modified titanate nanowhiskers were obtained by loading tributyl phosphate (TBP) on the surface of the titanate nanowhiskers. The morphology and structure of the titanate nanowhiskers and the modified titanate nanowhiskers were characterized by SEM, TEM and FTIR. The two nanomaterials were applied for the adsorption of uranium ion, and the adsorption kinetics and the adsorption isotherm model of the modified titanate nanowhiskers were studied. SEM photographs show that the particle size of the titanate nanowhiskers ranges from 80 nm to 100 nm. Uranium adsorption studies demonstrate that modified titanate nanowhiskers exhibite higher adsorption capacity in 3 mol/L NO-3 medium than titanate nanowhiskers. Adsorption kinetics of uranium on modified titanate nanowhiskers is in accordance with quasi-second order kinetic model, and adsorption isotherm model consistents with Langmuir and Freundlich isotherm model. The modified titanate nanowhiskers were applied to recover low concentration uranium from tap water, and satisfactory results were achieved.
2011, 28(3): 103-108.
Abstract:
The polyurethane-aluminum foam was fabricated by filling the open-cell aluminum foam with polyurethane. Making use of the Hopkinson pressure bar, the dynamic compression experiments have been carried out to reinforced composites of three-dimensional continuous network composed of aluminum foam and polyurethane under different relative density, strain rate and polyurethane content. The experiment results indicate that the yield strength and the compression strain of polyurethane-aluminum foam are significantly improved, compared with the aluminum foam under the identical strain rate and relative density, and its stress-strain curve displays some obvious fluctuations. With the increase of the strain, the stress also increases and when the strain reaches a certain value, the stress corresponding to the polyurethane-aluminum foam is higher and its energy absorption is more than that of the aluminum foam. Furthermore, when the strain rate increases, polyurethane-aluminum foam presents an obvious effect of strain rate.
The polyurethane-aluminum foam was fabricated by filling the open-cell aluminum foam with polyurethane. Making use of the Hopkinson pressure bar, the dynamic compression experiments have been carried out to reinforced composites of three-dimensional continuous network composed of aluminum foam and polyurethane under different relative density, strain rate and polyurethane content. The experiment results indicate that the yield strength and the compression strain of polyurethane-aluminum foam are significantly improved, compared with the aluminum foam under the identical strain rate and relative density, and its stress-strain curve displays some obvious fluctuations. With the increase of the strain, the stress also increases and when the strain reaches a certain value, the stress corresponding to the polyurethane-aluminum foam is higher and its energy absorption is more than that of the aluminum foam. Furthermore, when the strain rate increases, polyurethane-aluminum foam presents an obvious effect of strain rate.
2011, 28(3): 109-114.
Abstract:
A chemical modification was adopted to treat the surface of Kevlar fibers. The influences of the Kevlar fiber on the strength and shock resistance of cement-based composites before and after chemical modification were studied. The results indicate that chemical modification can obviously strengthen the enhancement effect of Kevlar fibers on the flexural strength and shock resistance of the cement mortar. When the fiber volume ratio is 1.0%, the flexural strength of the cement mortar reinforced by Kevlar fiber before and after chemical modification is increased by 15.18% and 23.85%, respectively, and the toughness of shock resistance is increased by 276.74% and 294.54%, respectively, compared with the reference with no fiber. The micro-morphology of Kevlar fibers and the fracture morphology of the samples were observed by SEM, and the changes of the elements on the surface of Kevlar fibers before and after modification were studied with XPS. The mechanism of Kevlar fibers in improving mortar’s mechanical performance was discussed.
A chemical modification was adopted to treat the surface of Kevlar fibers. The influences of the Kevlar fiber on the strength and shock resistance of cement-based composites before and after chemical modification were studied. The results indicate that chemical modification can obviously strengthen the enhancement effect of Kevlar fibers on the flexural strength and shock resistance of the cement mortar. When the fiber volume ratio is 1.0%, the flexural strength of the cement mortar reinforced by Kevlar fiber before and after chemical modification is increased by 15.18% and 23.85%, respectively, and the toughness of shock resistance is increased by 276.74% and 294.54%, respectively, compared with the reference with no fiber. The micro-morphology of Kevlar fibers and the fracture morphology of the samples were observed by SEM, and the changes of the elements on the surface of Kevlar fibers before and after modification were studied with XPS. The mechanism of Kevlar fibers in improving mortar’s mechanical performance was discussed.
2011, 28(3): 115-120.
Abstract:
The preparation technology of ion-exchange polymer metal composites (IPMC) was explored, and the Pt-IPMC samples were successfully prepared by a chemical deposition method. SEM was used for analyzing the topography and chemical composition of the surface electrodes. The displacement of Pt-IPMC sample was measured under four types of actuating signal (amplitude of 2~4 V, frequency of 0.06~0.14 Hz). The results show that the Pt atoms deposit well both inside and outside of the exchange membrane so that the depths of interior and exterior electrodes decrease to some extent. It is also found that the deformability and response speed of the Pt-IPMC samples are improved with the amplitude of driving signal rising. Furthmore, the displacement of Pt-IPMC samples all reaches a peak for four types of signals, and the Pt-IPMC sample shows the best response speed and deformability under the square wave when the actuating frequency is 0.1 Hz.
The preparation technology of ion-exchange polymer metal composites (IPMC) was explored, and the Pt-IPMC samples were successfully prepared by a chemical deposition method. SEM was used for analyzing the topography and chemical composition of the surface electrodes. The displacement of Pt-IPMC sample was measured under four types of actuating signal (amplitude of 2~4 V, frequency of 0.06~0.14 Hz). The results show that the Pt atoms deposit well both inside and outside of the exchange membrane so that the depths of interior and exterior electrodes decrease to some extent. It is also found that the deformability and response speed of the Pt-IPMC samples are improved with the amplitude of driving signal rising. Furthmore, the displacement of Pt-IPMC samples all reaches a peak for four types of signals, and the Pt-IPMC sample shows the best response speed and deformability under the square wave when the actuating frequency is 0.1 Hz.
2011, 28(3): 121-126.
Abstract:
The microstructures and mechanical properties of the gastropod shell of Hemifusus tuba during different growing periods were studied. The results show that the thickness and mechanical performance of the aragonite fiber increase with the accretion of Hemifusus tuba shell. Thus the mollusk shell alters the microstructure through the soft tissue in the growth process and the structure of mineral and mechanical performance of mollusk shell varies. The mechanical properties of mollusk shells are affected synthetically by the microstructure, organic matrix and some other factors, which are different from the higher strength and little dimension of the traditional engineering material.
The microstructures and mechanical properties of the gastropod shell of Hemifusus tuba during different growing periods were studied. The results show that the thickness and mechanical performance of the aragonite fiber increase with the accretion of Hemifusus tuba shell. Thus the mollusk shell alters the microstructure through the soft tissue in the growth process and the structure of mineral and mechanical performance of mollusk shell varies. The mechanical properties of mollusk shells are affected synthetically by the microstructure, organic matrix and some other factors, which are different from the higher strength and little dimension of the traditional engineering material.
2011, 28(3): 127-134.
Abstract:
Ag/chitosan (CS) composite colloids were synthesized by the liquid-phase chemical reduction and then Ag/CS-g-methylmethacrylate (MMA) composite was prepared by graft polymerization.The results show that Ag nanoparticles hinder the graft polymerization of CS with MMA, which results in the decrease of the graft percentage and graft efficiency in comparison with those without Ag nanoparticles.The structural characterizations verify that Ag nanoparticles disperse uniformly in the composites.The evaluations of antimicrobial activities show that the antibacterial performances of Ag/CS and Ag/CS-g-MMA composites are higher than that of Ag or CS alone.Among them, the inhibition rate of Ag/CS-g-MMA to four kinds of bacteria of E.coli, B.subtilis, S.aureus and P.aeruginosa are 96.3%、 97.6%、 93.2%、 95.8%, respectively.The antibacterial mechanisms of Ag nanoparticles and CS were studied.The antibacterial activities of Ag/CS based antimicrobial are displayed by the cooperation of Ag nanoparticles with CS.
Ag/chitosan (CS) composite colloids were synthesized by the liquid-phase chemical reduction and then Ag/CS-g-methylmethacrylate (MMA) composite was prepared by graft polymerization.The results show that Ag nanoparticles hinder the graft polymerization of CS with MMA, which results in the decrease of the graft percentage and graft efficiency in comparison with those without Ag nanoparticles.The structural characterizations verify that Ag nanoparticles disperse uniformly in the composites.The evaluations of antimicrobial activities show that the antibacterial performances of Ag/CS and Ag/CS-g-MMA composites are higher than that of Ag or CS alone.Among them, the inhibition rate of Ag/CS-g-MMA to four kinds of bacteria of E.coli, B.subtilis, S.aureus and P.aeruginosa are 96.3%、 97.6%、 93.2%、 95.8%, respectively.The antibacterial mechanisms of Ag nanoparticles and CS were studied.The antibacterial activities of Ag/CS based antimicrobial are displayed by the cooperation of Ag nanoparticles with CS.
2011, 28(3): 135-140.
Abstract:
In order to improve the bioactivity of C/C material and the bonding strength between C/C matrix and the bioactive materials of hydroxyapatite (HAp), the HAp-polyarcyl amide(PAM) composites coatings were prepared by a novel hydrothermal electrophoresis polymerization deposition process on the surface of C/C composite in isopropyl alcohol, using sonochemical resulted HAp nanoparticles and AM as raw materials. The phase composition, functional group, fracture surface morphologies and bonding strength of the as-prepared coatings were characterized by XRD, TEM, SEM, FTIR and mechanical tests. The influence of the deposition voltage on the microstructures and properties was investigated. The results show that with the increase of the deposition voltage,the crystallization, density and homogeneity of the HAp coatings firstly increase then decrease, and the crystallization of the PAM phase decreases with deposition voltage. The bonding strength of the composite coatings with C/C matrix also firstly increases and then decreases with the increase of the deposition voltage. When the deposition voltage is 150 V, the density and homogeneity of the coatings reach the optimized value and the thickness and bonding strength of the coating with matrix reach 25 μm and 19.10 MPa, respectively.
In order to improve the bioactivity of C/C material and the bonding strength between C/C matrix and the bioactive materials of hydroxyapatite (HAp), the HAp-polyarcyl amide(PAM) composites coatings were prepared by a novel hydrothermal electrophoresis polymerization deposition process on the surface of C/C composite in isopropyl alcohol, using sonochemical resulted HAp nanoparticles and AM as raw materials. The phase composition, functional group, fracture surface morphologies and bonding strength of the as-prepared coatings were characterized by XRD, TEM, SEM, FTIR and mechanical tests. The influence of the deposition voltage on the microstructures and properties was investigated. The results show that with the increase of the deposition voltage,the crystallization, density and homogeneity of the HAp coatings firstly increase then decrease, and the crystallization of the PAM phase decreases with deposition voltage. The bonding strength of the composite coatings with C/C matrix also firstly increases and then decreases with the increase of the deposition voltage. When the deposition voltage is 150 V, the density and homogeneity of the coatings reach the optimized value and the thickness and bonding strength of the coating with matrix reach 25 μm and 19.10 MPa, respectively.
2011, 28(3): 141-147.
Abstract:
Based on the software ANSYS, a user-program was developed for simulating the variation of temperature-cure degree coupling field in a composite curing process. Both of a 2D and 3D finite element models were used to analyze the coupling field in an advanced orthogonal grid-stiffened composite structure during the soft-mold aided co-curing process. The calculation results show that the 2D finite element model proposed in the paper could effectively simulate the co-curing process for an advanced grid-stiffened composite structure with a larger time step regardless the node of crossing ribs, and the 3D precise finite element model could be employed to obtain the distribution of temperature and cure degree fields accurately considering the node of crossing ribs. It is found that the temperature near the node of crossing ribs in the advanced grid-stiffened composite structure is obviously higher than other areas during the co-curing process.
Based on the software ANSYS, a user-program was developed for simulating the variation of temperature-cure degree coupling field in a composite curing process. Both of a 2D and 3D finite element models were used to analyze the coupling field in an advanced orthogonal grid-stiffened composite structure during the soft-mold aided co-curing process. The calculation results show that the 2D finite element model proposed in the paper could effectively simulate the co-curing process for an advanced grid-stiffened composite structure with a larger time step regardless the node of crossing ribs, and the 3D precise finite element model could be employed to obtain the distribution of temperature and cure degree fields accurately considering the node of crossing ribs. It is found that the temperature near the node of crossing ribs in the advanced grid-stiffened composite structure is obviously higher than other areas during the co-curing process.
2011, 28(3): 148-153.
Abstract:
A calculation model of stitching yarn was proposed, and the elastic properties parameter of stitching yarn were obtained based on the numerical simulation and the experiment results. The finite element simulating calculation was carried out on the stitching reinforcement for composite laminates containing a circular hole. The strain distribution near the hole edge were investigated analytically. The hole edge coefficients of strain concentration were calculated for different stitching parameters, such as stitching needle distance, row spacing, edge distance, diameter and modulus. A stitching design parameters on the edge of hole are obtained.
A calculation model of stitching yarn was proposed, and the elastic properties parameter of stitching yarn were obtained based on the numerical simulation and the experiment results. The finite element simulating calculation was carried out on the stitching reinforcement for composite laminates containing a circular hole. The strain distribution near the hole edge were investigated analytically. The hole edge coefficients of strain concentration were calculated for different stitching parameters, such as stitching needle distance, row spacing, edge distance, diameter and modulus. A stitching design parameters on the edge of hole are obtained.
2011, 28(3): 154-158.
Abstract:
For the structure reliability of the cylindrical composite shell rotating with a high speed, the strain equations were derived, then the axial, peripheral and shear stresses as well as the correspondenting main axial stresses were derived for every layer and their variations with the angle and the thickness of the small angle winding layer were obtained. The optimal designs of the structural parameter for the cylindrical composite shell were made under the condition that the object function was equal strengthen reliability which was 0.99 for every layer.
For the structure reliability of the cylindrical composite shell rotating with a high speed, the strain equations were derived, then the axial, peripheral and shear stresses as well as the correspondenting main axial stresses were derived for every layer and their variations with the angle and the thickness of the small angle winding layer were obtained. The optimal designs of the structural parameter for the cylindrical composite shell were made under the condition that the object function was equal strengthen reliability which was 0.99 for every layer.
2011, 28(3): 159-166.
Abstract:
Based on the chemical conversion properties of the constituents of phenolic-based C/C composites during liquid-phase impregnation process and Arrhenius equation, the manufacturing process mechanical model for C/C composites was established. The variations of volume fraction of different component phases in two important stages of solidification-carbonization and graphitization were analyzed. The volume fraction of pores obtained by simulations is in a good agreement with the experimental results obtained by image processing of Micro-CT system for the actual fine-woven punctured C/C composites. Combined with homogenization method, the effective elastic modulus of matrix during manufacturing process was predicted. The results show that the effective elastic modulus of matrix increases with the increasing of the densification times. The elastic modulus of matrix in each densification process increases first and then decreases. After solidification process, the elastic modulus of matrix approaches a stable value.
Based on the chemical conversion properties of the constituents of phenolic-based C/C composites during liquid-phase impregnation process and Arrhenius equation, the manufacturing process mechanical model for C/C composites was established. The variations of volume fraction of different component phases in two important stages of solidification-carbonization and graphitization were analyzed. The volume fraction of pores obtained by simulations is in a good agreement with the experimental results obtained by image processing of Micro-CT system for the actual fine-woven punctured C/C composites. Combined with homogenization method, the effective elastic modulus of matrix during manufacturing process was predicted. The results show that the effective elastic modulus of matrix increases with the increasing of the densification times. The elastic modulus of matrix in each densification process increases first and then decreases. After solidification process, the elastic modulus of matrix approaches a stable value.
2011, 28(3): 167-173.
Abstract:
A new method was presented to predict the effective elastic constants of unidirectional continuous fiber reinforced composites containing voids of various characteristics based on the similarity between the deformation of the fibers around the voids and the flow field around the 3D Rankine oval. A finite element model of the representative volume cell was proposed, in which the volume fraction change of the fibers around the voids was described by the velocity variation in the flow field, and the direction of the fibers around the voids was described by the streamline shape. The periodic boundary conditions were used to calculate the laminar elastic properties, combining with the probability distribution model of the void shape and the stiffness volume average method. The numerical results agree reasonably with the available experimental data, which validates the computational method in the prediction of the voids influence on the elastic properties of the unidirectional continuous fiber reinforced composites.
A new method was presented to predict the effective elastic constants of unidirectional continuous fiber reinforced composites containing voids of various characteristics based on the similarity between the deformation of the fibers around the voids and the flow field around the 3D Rankine oval. A finite element model of the representative volume cell was proposed, in which the volume fraction change of the fibers around the voids was described by the velocity variation in the flow field, and the direction of the fibers around the voids was described by the streamline shape. The periodic boundary conditions were used to calculate the laminar elastic properties, combining with the probability distribution model of the void shape and the stiffness volume average method. The numerical results agree reasonably with the available experimental data, which validates the computational method in the prediction of the voids influence on the elastic properties of the unidirectional continuous fiber reinforced composites.
2011, 28(3): 174-179.
Abstract:
The dynamic behavior of the airdropped flexible container under impact loading was predicted based on the properties prediction of composite material. A unit cell finite element model of the textile composite was constructed, and mechanical properties of the composite were obtained by applying periodic boundary conditions on the unit cell model. Based on the prediction, the impact numerical test of the flexible liquid storage container, which contains 80% water in volume, was carried out. The interaction between the container and the fluid was modeled and studied using the multi-material ALE method. Numerical results were compared with experimental data for the validation of the model and the approaches, which shows that the periodic boundary conditions can provide more accurate results. In addition, the impact model and the fluid-structure interaction (FSI) technology are also validated.
The dynamic behavior of the airdropped flexible container under impact loading was predicted based on the properties prediction of composite material. A unit cell finite element model of the textile composite was constructed, and mechanical properties of the composite were obtained by applying periodic boundary conditions on the unit cell model. Based on the prediction, the impact numerical test of the flexible liquid storage container, which contains 80% water in volume, was carried out. The interaction between the container and the fluid was modeled and studied using the multi-material ALE method. Numerical results were compared with experimental data for the validation of the model and the approaches, which shows that the periodic boundary conditions can provide more accurate results. In addition, the impact model and the fluid-structure interaction (FSI) technology are also validated.
2011, 28(3): 180-184.
Abstract:
The tensile and compressive performance of carbon fiber(CCF300)/bismaleimide (GW-300) laminates were experimentally studied at 200 ℃ and 300 ℃. It is found that the tensile strength and modulus of the laminates controlled by the resin decrease more than those controlled by the fibers. The compressive strength of the thick laminates increases more than that of the thin laminates with temperature rising. The retention rate of tensile performance is high, while it is low for the compressive performance at high temperature. The retention rate of tensile strength of the laminates controlled by the resin and fibers are more than 70% and 90%, respectively, at 300 ℃, while both of the retention rate of compressive strength of thick and thin laminates are a little more than 30%.
The tensile and compressive performance of carbon fiber(CCF300)/bismaleimide (GW-300) laminates were experimentally studied at 200 ℃ and 300 ℃. It is found that the tensile strength and modulus of the laminates controlled by the resin decrease more than those controlled by the fibers. The compressive strength of the thick laminates increases more than that of the thin laminates with temperature rising. The retention rate of tensile performance is high, while it is low for the compressive performance at high temperature. The retention rate of tensile strength of the laminates controlled by the resin and fibers are more than 70% and 90%, respectively, at 300 ℃, while both of the retention rate of compressive strength of thick and thin laminates are a little more than 30%.
2011, 28(3): 185-191.
Abstract:
The paper seeks to address the techniques of structural optimization design, manufacturing and experimental measurement of mechanical properties for integral composite wing with the specific dimension and configuration. By using finite element analysis (FEA) code, the numerical simulation on static strength of hollow composite wing was conducted to obtain the relationship between load-carrying efficiency and geometric dimension. From the FEA results, the optimized dimension of wing and ply thickness for stacking fibre were determined. An integral composite wing was processed by using the processing technique incorporating balloon-forming method and paraffin core mould. The three-point bending test was performed to verify the mechanical properties of wing, and the failure mechanism was discussed from experimental observation. It is found that the main failure mode is local buckling occurring on upper surface of composite wing, and the wing with local buckling is still capable of carrying a load.
The paper seeks to address the techniques of structural optimization design, manufacturing and experimental measurement of mechanical properties for integral composite wing with the specific dimension and configuration. By using finite element analysis (FEA) code, the numerical simulation on static strength of hollow composite wing was conducted to obtain the relationship between load-carrying efficiency and geometric dimension. From the FEA results, the optimized dimension of wing and ply thickness for stacking fibre were determined. An integral composite wing was processed by using the processing technique incorporating balloon-forming method and paraffin core mould. The three-point bending test was performed to verify the mechanical properties of wing, and the failure mechanism was discussed from experimental observation. It is found that the main failure mode is local buckling occurring on upper surface of composite wing, and the wing with local buckling is still capable of carrying a load.
2011, 28(3): 192-196.
Abstract:
The buckling and post-buckling behaviors of a functionally graded material(FGM) column under distributed load were analysed. Based on the large deformation theory and consideration of the axial extension of the column, the quilibrium equations with geometric nonlinearity of an elastic FGM column subjected to distributed load were established. In the analysis, it was assumed that the material properties of the column vary continuously as a power function of the thickness coordinate. By using shooting method and analytical continuation, the nonlinear boundary-value problem was solved numerically and buckling and post-buckling response of FGM column with free- fixed edges were obtained. The post-buckling characteristics curves of FGM column under the different graded index were plotted, which were compared with the those of pure metal and ceramic material columns. The effects of material gradient property on the buckling deformation and critical load of beam were discussed in details.The results show that the post-buckling behavior of the FGM column are different from that of homogenous column, and the gradient index of the material have significant effect on the bucking load and post-buckling behavior of the FGM columns.
The buckling and post-buckling behaviors of a functionally graded material(FGM) column under distributed load were analysed. Based on the large deformation theory and consideration of the axial extension of the column, the quilibrium equations with geometric nonlinearity of an elastic FGM column subjected to distributed load were established. In the analysis, it was assumed that the material properties of the column vary continuously as a power function of the thickness coordinate. By using shooting method and analytical continuation, the nonlinear boundary-value problem was solved numerically and buckling and post-buckling response of FGM column with free- fixed edges were obtained. The post-buckling characteristics curves of FGM column under the different graded index were plotted, which were compared with the those of pure metal and ceramic material columns. The effects of material gradient property on the buckling deformation and critical load of beam were discussed in details.The results show that the post-buckling behavior of the FGM column are different from that of homogenous column, and the gradient index of the material have significant effect on the bucking load and post-buckling behavior of the FGM columns.
2011, 28(3): 197-202.
Abstract:
A 3D FEM was presented for the progressive damage analysis on the adhesively bonding patch repair of composite laminates. The constitutive model of laminates and adhesive were established with the orthotropic damage tensor and isotropic damage variable in the frame of continuum damage mechanism, respectively. The failure initiation, progression and their interactons of both laminates and adhesive were take into considerations during the whole analysis. The proposed model was validated by the existing experiments of the bonding patch repair of laminates under compression. The effects of repair parameters on the repair strength were also evaluated with the proposed model. The results show that the patch failure is the critical factor of the repaired laminates strength when the patch is thin, while the adhesive is the critical factor of the repaired laminates strength when the patch is thick enough. Under this condition, the laminates strength will not increase with the increase of the patch thickness. Therefore, the patch and adhesive should be designed carefully and optimized before an adhesively bonding patch repair on a damaged laminates.
A 3D FEM was presented for the progressive damage analysis on the adhesively bonding patch repair of composite laminates. The constitutive model of laminates and adhesive were established with the orthotropic damage tensor and isotropic damage variable in the frame of continuum damage mechanism, respectively. The failure initiation, progression and their interactons of both laminates and adhesive were take into considerations during the whole analysis. The proposed model was validated by the existing experiments of the bonding patch repair of laminates under compression. The effects of repair parameters on the repair strength were also evaluated with the proposed model. The results show that the patch failure is the critical factor of the repaired laminates strength when the patch is thin, while the adhesive is the critical factor of the repaired laminates strength when the patch is thick enough. Under this condition, the laminates strength will not increase with the increase of the patch thickness. Therefore, the patch and adhesive should be designed carefully and optimized before an adhesively bonding patch repair on a damaged laminates.
2011, 28(3): 203-209.
Abstract:
Based on the techniques of water-soluble mandrel and digital design, the integrated composite wing box was designed and manufactured by the resin transfer molding (RTM) process. The optimized injection pattern and process parameters were determined by the PAM-RTM code and the RTM mould was designed and fabricated from the results of resin flow simulation. According to the fiber overlay design and forming process, the integral composite wing box was manufactured to verify the validity and feasibility of the RTM technique for the integrated wing box.
Based on the techniques of water-soluble mandrel and digital design, the integrated composite wing box was designed and manufactured by the resin transfer molding (RTM) process. The optimized injection pattern and process parameters were determined by the PAM-RTM code and the RTM mould was designed and fabricated from the results of resin flow simulation. According to the fiber overlay design and forming process, the integral composite wing box was manufactured to verify the validity and feasibility of the RTM technique for the integrated wing box.
2011, 28(3): 210-216.
Abstract:
The honeycomb core of cells was modeled as a layer of orthotropic material whose physical and the mechanical properties were determined by the corrected Gibson’s formula.Based on the classical plate theory, a preliminary study was conducted for the natural frequency of the honeycomb sandwich plate with completed clamped supported. The effects of panel thickness and core thickness on the natural frequency of honeycomb were investigated. Furthermore, the finite element simulations with equivalent parameters performed. The results show that the method can exactly calculate the natural frequency of honeycomb.
The honeycomb core of cells was modeled as a layer of orthotropic material whose physical and the mechanical properties were determined by the corrected Gibson’s formula.Based on the classical plate theory, a preliminary study was conducted for the natural frequency of the honeycomb sandwich plate with completed clamped supported. The effects of panel thickness and core thickness on the natural frequency of honeycomb were investigated. Furthermore, the finite element simulations with equivalent parameters performed. The results show that the method can exactly calculate the natural frequency of honeycomb.
2011, 28(3): 217-222.
Abstract:
The thermal property of AlN filled silicone encapsulant was investigated through experimental method and numerical simulation. A 3D finite element model of AlN filled silicone encapsulant was built by random sequential adsorption (RSA) method. This model can generate representative volume element of random particle location and different particle diameters. The single particle size and multiple particle sizes models can be established. The AlN particles in 3 μm filled silicone encapsulant composite was prepared and the thermal conductivity was tested at different filling volume. The model was verified to be accurate by comparing the predicted and the practical thermal conductivity. The simulation results show that thermal conductivity of the silicone encapsulant increases with the filler mass fraction, and the thermal conductivity increases rapidly after the filler mass fraction being higher than 50%. When the AlN particles with normal distribution pack effectively, the filling volume is increased. The thermal conductivity is different when the composite is filled with different mass ratio of two different particles.
The thermal property of AlN filled silicone encapsulant was investigated through experimental method and numerical simulation. A 3D finite element model of AlN filled silicone encapsulant was built by random sequential adsorption (RSA) method. This model can generate representative volume element of random particle location and different particle diameters. The single particle size and multiple particle sizes models can be established. The AlN particles in 3 μm filled silicone encapsulant composite was prepared and the thermal conductivity was tested at different filling volume. The model was verified to be accurate by comparing the predicted and the practical thermal conductivity. The simulation results show that thermal conductivity of the silicone encapsulant increases with the filler mass fraction, and the thermal conductivity increases rapidly after the filler mass fraction being higher than 50%. When the AlN particles with normal distribution pack effectively, the filling volume is increased. The thermal conductivity is different when the composite is filled with different mass ratio of two different particles.
2011, 28(3): 223-228.
Abstract:
Honeycomb reinforced plastic foam samples were prepared through honeycomb cutting and injection molding process, and the compression tests of samples were done. Through tests the pressure-displacement date were obtained, then the calculation was conducted to obtain the stress-strain curve of honeycomb reinforced plastic foam samples. The experimental results show that stress of all honeycomb reinforced plastic foam samples is larger than the sum of honeycomb and plastic foam. It is also found that the complex effect of composite material is more apparent with the decrease of the length of the cell and the increase of the thickness of samples. On the basis of quasi-static properties, the simulation model of composite material was built. By applying pressure pulse to the model, the same complex effect was found on the condition of dynamic impact. It is proved that this composite material is suitable not only for lower strain ratio, but also for higher strain ratio.
Honeycomb reinforced plastic foam samples were prepared through honeycomb cutting and injection molding process, and the compression tests of samples were done. Through tests the pressure-displacement date were obtained, then the calculation was conducted to obtain the stress-strain curve of honeycomb reinforced plastic foam samples. The experimental results show that stress of all honeycomb reinforced plastic foam samples is larger than the sum of honeycomb and plastic foam. It is also found that the complex effect of composite material is more apparent with the decrease of the length of the cell and the increase of the thickness of samples. On the basis of quasi-static properties, the simulation model of composite material was built. By applying pressure pulse to the model, the same complex effect was found on the condition of dynamic impact. It is proved that this composite material is suitable not only for lower strain ratio, but also for higher strain ratio.
2011, 28(3): 229-235.
Abstract:
Based on the micromechanical damage characteristics of composite solid propellants, a cohesive interface element was placed between particles and binder. The bilinear model was used to describe interfacial damage evolution, and its key parameters were determined, including the intial linear modulus, maxmial cohesive strength, and maximal displacement. Combined with packing models of composite solid propellant, the micromechanical interfacial debonding was analyzed by finite element method. The results show that cohesive interface element can effectively predict the progress of debonding of particles from binder. The nonlinear mechanical properties of propellant under tensile is closely related with interfacial debonding. The numerical results are in agreement with the experimental observations.
Based on the micromechanical damage characteristics of composite solid propellants, a cohesive interface element was placed between particles and binder. The bilinear model was used to describe interfacial damage evolution, and its key parameters were determined, including the intial linear modulus, maxmial cohesive strength, and maximal displacement. Combined with packing models of composite solid propellant, the micromechanical interfacial debonding was analyzed by finite element method. The results show that cohesive interface element can effectively predict the progress of debonding of particles from binder. The nonlinear mechanical properties of propellant under tensile is closely related with interfacial debonding. The numerical results are in agreement with the experimental observations.
2011, 28(3): 236-244.
Abstract:
Material parameters were supposed to have a gradient change in the thickness direction. The functionally graded electro-magneto-elastic plate was divided into layer elements along the thickness direction. The governing equations of an element were obtained, and then the governing equations of the elements were assembled into the total equations. The dispersion curves of waves in the functionally graded electro-magneto-elastic plate can be obtained by the solution of the governing equations. The effects of the parameters of the electric and magnetic materials on the dispersion of wave were analyzed. The displacement and electrostatic potential and magneto-static potential distributions of the wave modes were investigated. The six characteristic surfaces of the wave were analyzed. The numeric results show that the elastic displacement, static electro potential and static magneto potential distribution converge on the thickness direction of the smaller parameters. The functionally graded electro-magneto-elastic material is orthotropic.
Material parameters were supposed to have a gradient change in the thickness direction. The functionally graded electro-magneto-elastic plate was divided into layer elements along the thickness direction. The governing equations of an element were obtained, and then the governing equations of the elements were assembled into the total equations. The dispersion curves of waves in the functionally graded electro-magneto-elastic plate can be obtained by the solution of the governing equations. The effects of the parameters of the electric and magnetic materials on the dispersion of wave were analyzed. The displacement and electrostatic potential and magneto-static potential distributions of the wave modes were investigated. The six characteristic surfaces of the wave were analyzed. The numeric results show that the elastic displacement, static electro potential and static magneto potential distribution converge on the thickness direction of the smaller parameters. The functionally graded electro-magneto-elastic material is orthotropic.
