2005 Vol. 22, No. 2
2005, 22(2): 1-5.
Abstract:
A novel type elasticity-damping composite was manufactured using Cu-Al-Ni-Mn-Ti alloy and QBe2 alloy by explosion cladding. The damping value of the composite is about 10 times higher than that of the QBe2 alloy ,and has an obvious amplitude effect . The elect rical resistivity of the composite board is lower than that of the QBe2alloy but higher than that of the Cu-Al-Ni-Mn-Ti SMA. The boundary of the composite board has a little effect onthe resistivity of the composite board. The shape of the boundary of the composite by explosion cladding is wavelike. At 780 ℃, the boundary of the composite widens with the prolong of the holding time.
A novel type elasticity-damping composite was manufactured using Cu-Al-Ni-Mn-Ti alloy and QBe2 alloy by explosion cladding. The damping value of the composite is about 10 times higher than that of the QBe2 alloy ,and has an obvious amplitude effect . The elect rical resistivity of the composite board is lower than that of the QBe2alloy but higher than that of the Cu-Al-Ni-Mn-Ti SMA. The boundary of the composite board has a little effect onthe resistivity of the composite board. The shape of the boundary of the composite by explosion cladding is wavelike. At 780 ℃, the boundary of the composite widens with the prolong of the holding time.
2005, 22(2): 6-10.
Abstract:
Nb/ Nb5Si3 is a new high temperature st ructural composite and has great application potentials in manyfields. In order to decrease the fabricating cost of Nb/ Nb5Si3 composite and to efficiently cont rol it s microst ructure ,spark plasma sintering (SPS) technology was used to in2si tu synthesize Nb/ Nb5Si3 composites from a mixture of Nband Si powders , and the effect of Si content on the microst ructures of the fabricated composites was mainly investi2gated. The result s show that fully dense Nb/ Nb5Si3 composites can be fabricated by SPS technology , and the micrO2st ructures of the composites consist of the in2si tu synthesized Nb5Si3 and the dispersed Nb particles. Moreover , withthe increasing of Si content from 6 % to 20 %(atom f raction) , the volume f raction of the synthesized Nb5Si3 in thecomposites increases , whereas the content and size of Nb particles decrease obviously. As a result , the density andhardness of the composites are both improved.
Nb/ Nb5Si3 is a new high temperature st ructural composite and has great application potentials in manyfields. In order to decrease the fabricating cost of Nb/ Nb5Si3 composite and to efficiently cont rol it s microst ructure ,spark plasma sintering (SPS) technology was used to in2si tu synthesize Nb/ Nb5Si3 composites from a mixture of Nband Si powders , and the effect of Si content on the microst ructures of the fabricated composites was mainly investi2gated. The result s show that fully dense Nb/ Nb5Si3 composites can be fabricated by SPS technology , and the micrO2st ructures of the composites consist of the in2si tu synthesized Nb5Si3 and the dispersed Nb particles. Moreover , withthe increasing of Si content from 6 % to 20 %(atom f raction) , the volume f raction of the synthesized Nb5Si3 in thecomposites increases , whereas the content and size of Nb particles decrease obviously. As a result , the density andhardness of the composites are both improved.
2005, 22(2): 11-15.
Abstract:
In-situ sol-gel method was employed to prepare SiO2 / PI hybrid films with different silica content s. Themechanical properties at room temperature and cryogenic temperature (77 K) as a function of silica content werestudied. The result s show that the tensile st rength increases with the increasing of silica particles up to 3 % andthen decreases with the increasing of silica content at room and cryogenic temperatures. The cryogenic st rength isobviously higher than that at room temperature. The elongation at break reaches the maximum at 3 % silica contentat room temperature but has no obvious tendency at cryogenic temperature (77 K) . The molecular st ructure andmorphology of the fracture surfaces of hybrid films were analysed by using IR and SEM.
In-situ sol-gel method was employed to prepare SiO2 / PI hybrid films with different silica content s. Themechanical properties at room temperature and cryogenic temperature (77 K) as a function of silica content werestudied. The result s show that the tensile st rength increases with the increasing of silica particles up to 3 % andthen decreases with the increasing of silica content at room and cryogenic temperatures. The cryogenic st rength isobviously higher than that at room temperature. The elongation at break reaches the maximum at 3 % silica contentat room temperature but has no obvious tendency at cryogenic temperature (77 K) . The molecular st ructure andmorphology of the fracture surfaces of hybrid films were analysed by using IR and SEM.
2005, 22(2): 16-20.
Abstract:
The gel nanocomposite polymer elect rolyte (NCPE) was prepared by UV radiation curing based on poly(ethylene glycol) diacrylate ( PEGDA) monomer containing nanosize SiO2 in the presence of liquid elect rolyte. ThePEGDA monomer containing nanosize SiO2 was synthesized using aqueous colloidal silica as one of starting materialsthrough a solvent exchange process and the partial surface groups of SiO2 were modified into acrylic group during theprocedure by employing methacryloxypropyl t rimethoxysilane (MAPTMS) , which made the nanosize SiO2 havingthe UV-curable acrylate groups. Compared with the gel polymer elect rolyte based on PEGDA without nanosize filler , the ionic conductivity is higher and the improvement s in the elect rochemical stability and interfacial stability arenoticeable for the gel NCPE.
The gel nanocomposite polymer elect rolyte (NCPE) was prepared by UV radiation curing based on poly(ethylene glycol) diacrylate ( PEGDA) monomer containing nanosize SiO2 in the presence of liquid elect rolyte. ThePEGDA monomer containing nanosize SiO2 was synthesized using aqueous colloidal silica as one of starting materialsthrough a solvent exchange process and the partial surface groups of SiO2 were modified into acrylic group during theprocedure by employing methacryloxypropyl t rimethoxysilane (MAPTMS) , which made the nanosize SiO2 havingthe UV-curable acrylate groups. Compared with the gel polymer elect rolyte based on PEGDA without nanosize filler , the ionic conductivity is higher and the improvement s in the elect rochemical stability and interfacial stability arenoticeable for the gel NCPE.
2005, 22(2): 21-26.
Abstract:
The silicon dioxide (SiO2 ) / polystyrene ( PS) composite microspheres were prepared by dispersion polymerization in ethanol/ water medium. The process of dispersion polymerization was investigated , and the kinetics ofdispersion polymersion with nano-SiO2 in the reaction system was studied. The samples were characterized by microscopy techniques (SEM ,TEM) . It is shown that nano-SiO2 particles are encapsulated by PS af ter dispersion polymerization in ethanol/ water medium using polyvinylpyrrolidone ( PVP K-30) as stabilizer. The average size of thecomposite microsphere is 1.25μm and the dispersion coefficientεis 0.035. The effect s of stabilizer concent ration onthe size of the microspheres were studied.
The silicon dioxide (SiO2 ) / polystyrene ( PS) composite microspheres were prepared by dispersion polymerization in ethanol/ water medium. The process of dispersion polymerization was investigated , and the kinetics ofdispersion polymersion with nano-SiO2 in the reaction system was studied. The samples were characterized by microscopy techniques (SEM ,TEM) . It is shown that nano-SiO2 particles are encapsulated by PS af ter dispersion polymerization in ethanol/ water medium using polyvinylpyrrolidone ( PVP K-30) as stabilizer. The average size of thecomposite microsphere is 1.25μm and the dispersion coefficientεis 0.035. The effect s of stabilizer concent ration onthe size of the microspheres were studied.
2005, 22(2): 27-33.
Abstract:
MCM-41/ epoxy resin and modified MCM-41/ epoxy resin nanocomposites were prepared by solutionblending. The influences of coupling agent modification and the content of the particulates on the disperse propertiesand mechanical properties were investigated. The small angle X-ray diff raction ( XRD) of MCM-41/ epoxy resinshows that the nanO2porous MCM-41 channels are not dest royed in the composite. Because modified MCM-41 canst rengthen the links between particle and mat rix , and modified MCM-41 particle can disperse evenly in the mat rix ,the tensile properties of the composite are the highest when the amount of the modified MCM-41 particle is 2.5 %(mass f raction) . Compared with the mat rix , the tensile st rength and the Young’s modulus of the composites are improved by 99.2 % and 110 % respectively.
MCM-41/ epoxy resin and modified MCM-41/ epoxy resin nanocomposites were prepared by solutionblending. The influences of coupling agent modification and the content of the particulates on the disperse propertiesand mechanical properties were investigated. The small angle X-ray diff raction ( XRD) of MCM-41/ epoxy resinshows that the nanO2porous MCM-41 channels are not dest royed in the composite. Because modified MCM-41 canst rengthen the links between particle and mat rix , and modified MCM-41 particle can disperse evenly in the mat rix ,the tensile properties of the composite are the highest when the amount of the modified MCM-41 particle is 2.5 %(mass f raction) . Compared with the mat rix , the tensile st rength and the Young’s modulus of the composites are improved by 99.2 % and 110 % respectively.
2005, 22(2): 34-37.
Abstract:
Carbon fiber-reinforced polylactide (C/ PLA) composite used for bone fracture fixation was prepared ,and the change of mechanical performance was investigated during in vi t ro degradation. The result indicates that themechanical performance of C/ PLA composite descends to some extent , however , the C/ PLA composite whose carbon fiber was t reated by the surface soakage with thick nit ric acid attains a slow degradation rate , which denotes thatthe st ronger interfacial bonding st rength can rest rain in vi t ro degradation of C/ PLA composite.
Carbon fiber-reinforced polylactide (C/ PLA) composite used for bone fracture fixation was prepared ,and the change of mechanical performance was investigated during in vi t ro degradation. The result indicates that themechanical performance of C/ PLA composite descends to some extent , however , the C/ PLA composite whose carbon fiber was t reated by the surface soakage with thick nit ric acid attains a slow degradation rate , which denotes thatthe st ronger interfacial bonding st rength can rest rain in vi t ro degradation of C/ PLA composite.
2005, 22(2): 38-45.
Abstract:
SBR/ C18MMT and SBR/ Na-MMT composites were prepared through a melt intercalation process.The result s of XRD and TEM observation show that the dispersion of montmorillonite layers in SBR mat rix is determined by the hydrophobic property of the layers. Organic t reated montmorillonite could be exfoliated into layerswith about 20nm in thickness and uniformly dispersed in the SBR mat rix. The effect s of montmorillonite on the vulcanization reaction of SBR were determined by DSC method. The vulcanization curves show that the existence of C18-MMT accelerates the vulcanization reaction and the activation energy is not changed. For the SBR reinforced by Na-MMT , the vulcanization was impeded and the sensitivity of reaction to temperature was decreased , which resulted inthe decrease of apparent activity energy. Due to the nanoscale dispersion of layers of C18-MMT and the enhancedcrosslinking density of rubber mat rix , the mechanical properties of SBR dramatically increase. The tensile st rengthand 300 % modulus of SBR/ C18-MMT nanocomposite were correspondent to the SBR reinforced by equal content ofcarbon black N330 while the elongation at the break of the nanocomposite was much higher , which is related to theslipping and oriented arranging of the C18-MMT layers in the composite under tension.
SBR/ C18MMT and SBR/ Na-MMT composites were prepared through a melt intercalation process.The result s of XRD and TEM observation show that the dispersion of montmorillonite layers in SBR mat rix is determined by the hydrophobic property of the layers. Organic t reated montmorillonite could be exfoliated into layerswith about 20nm in thickness and uniformly dispersed in the SBR mat rix. The effect s of montmorillonite on the vulcanization reaction of SBR were determined by DSC method. The vulcanization curves show that the existence of C18-MMT accelerates the vulcanization reaction and the activation energy is not changed. For the SBR reinforced by Na-MMT , the vulcanization was impeded and the sensitivity of reaction to temperature was decreased , which resulted inthe decrease of apparent activity energy. Due to the nanoscale dispersion of layers of C18-MMT and the enhancedcrosslinking density of rubber mat rix , the mechanical properties of SBR dramatically increase. The tensile st rengthand 300 % modulus of SBR/ C18-MMT nanocomposite were correspondent to the SBR reinforced by equal content ofcarbon black N330 while the elongation at the break of the nanocomposite was much higher , which is related to theslipping and oriented arranging of the C18-MMT layers in the composite under tension.
2005, 22(2): 46-51.
Abstract:
ZnO whisker , which possesses stereoscopic st ructure , was int roduced into M40J / bisphenol-A dicyanate(BADCy) composite to improve it s ILSS1 The reaction mechanisms of BADCy blend with epoxy resin E51 and ZnOwhisker were studied by FTIR spect roscopy1 It was found that ZnO whisker serves as a catalyst of polycyclot rimerize reaction of BADCy , and post-cure temperature of BADCy/ E51 blend system was descended from 200 ℃ to180 ℃. The result s indicated that when 10 % ZnO whisker t reated by KH560 is int roduced , the ILSS and flexuralmodulus of M40J / BADCy composite could improve from 77.6 MPa and 178.9 GPa to 91.2 MPa and 207.4 GPa respectively , while with the unt reated ZnO whisker they are improved only slightly. The SEM analysis of f racture surfaces of broken specimens indicates that the ILSS and flexural modulus of M40J / BADCy composite were improvedby means of the“nail”of ZnO whisker in the laminar of M40J / BADCy composite.
ZnO whisker , which possesses stereoscopic st ructure , was int roduced into M40J / bisphenol-A dicyanate(BADCy) composite to improve it s ILSS1 The reaction mechanisms of BADCy blend with epoxy resin E51 and ZnOwhisker were studied by FTIR spect roscopy1 It was found that ZnO whisker serves as a catalyst of polycyclot rimerize reaction of BADCy , and post-cure temperature of BADCy/ E51 blend system was descended from 200 ℃ to180 ℃. The result s indicated that when 10 % ZnO whisker t reated by KH560 is int roduced , the ILSS and flexuralmodulus of M40J / BADCy composite could improve from 77.6 MPa and 178.9 GPa to 91.2 MPa and 207.4 GPa respectively , while with the unt reated ZnO whisker they are improved only slightly. The SEM analysis of f racture surfaces of broken specimens indicates that the ILSS and flexural modulus of M40J / BADCy composite were improvedby means of the“nail”of ZnO whisker in the laminar of M40J / BADCy composite.
2005, 22(2): 52-56.
Abstract:
A kind of blended powder of PA12 and organic rectorite (OREC) was molded by selective laser sintering (SLS) . The st ructure of sintered PA12/ rectorite composite was characterized by XRD , DSC and SEM , and it sthermal stability and mechanical properties were studied. The result s show that the organic rectorite is intercalatedby PA12 during the sintering process , and the thermal stability and the mechanical properties of the PA12/ rectoritenanocomposite are better than those of sintered pure PA12. With 10 % mass f raction of OREC , the tensile st rength ,flexural st rength and impact st rength are improved by 10.7 % , 15.9 % and 38.7 % , respectively , and the thermaldecomposition temperature increases by 27 ℃.
A kind of blended powder of PA12 and organic rectorite (OREC) was molded by selective laser sintering (SLS) . The st ructure of sintered PA12/ rectorite composite was characterized by XRD , DSC and SEM , and it sthermal stability and mechanical properties were studied. The result s show that the organic rectorite is intercalatedby PA12 during the sintering process , and the thermal stability and the mechanical properties of the PA12/ rectoritenanocomposite are better than those of sintered pure PA12. With 10 % mass f raction of OREC , the tensile st rength ,flexural st rength and impact st rength are improved by 10.7 % , 15.9 % and 38.7 % , respectively , and the thermaldecomposition temperature increases by 27 ℃.
2005, 22(2): 57-62.
Abstract:
The microst ructure and mechanical properties were studied for polyamide 66 ( PA66) / ult ra high molecular weight polyethylene ( U HMWPE) blends compatibilized by maleic anhydride high density polyethylene( HDPE-g-MAH) . The result s indicate that the notched izod impact st rength increases obviously with the increase ofcontent of U HMWPE at the expense of tensile/ flexural st rength and modulus. In order to improve the st rength andstiffness of U HMWPE toughening polyamide 66 , short glass fiber (SGF) and inorganic particles were employed toreinforce PA66/ U HMWPE/ HDPE-g-MA H (80/ 20/ 20) . It is found that the tensile/ flexural st rength and tensile/flexural modulus are improved substantially , meanwhile the high notched izod impact strength is maintained , about72.9 % higher than that of PA66.
The microst ructure and mechanical properties were studied for polyamide 66 ( PA66) / ult ra high molecular weight polyethylene ( U HMWPE) blends compatibilized by maleic anhydride high density polyethylene( HDPE-g-MAH) . The result s indicate that the notched izod impact st rength increases obviously with the increase ofcontent of U HMWPE at the expense of tensile/ flexural st rength and modulus. In order to improve the st rength andstiffness of U HMWPE toughening polyamide 66 , short glass fiber (SGF) and inorganic particles were employed toreinforce PA66/ U HMWPE/ HDPE-g-MA H (80/ 20/ 20) . It is found that the tensile/ flexural st rength and tensile/flexural modulus are improved substantially , meanwhile the high notched izod impact strength is maintained , about72.9 % higher than that of PA66.
2005, 22(2): 63-66.
Abstract:
The condition of fibers in carbon fiber sheet with epoxy resin mat rix used in civil inf rast ructure is different from that in indust rialized carbon fiber reinforced polymer/ plastic (CFRP) , i1 e. some fibers located inner ofthe fiber bundle are indeed without epoxy resin mat rix. The self-diagnostic function of carbon fiber sheet without epoxy resin mat rix was studied under a tensile loading condition. The experimental results indicate that the resistanceof carbon fiber sheet without epoxy resin mat rix linearly changes with the applied st rain , so the carbon fiber sheetcan act as a sensor to measure strain. A parallel variant2st ructure circuit , in which each carbon fiber bundle playsone path and a resistor , is employed to model the elect ric behavior of carbon fiber sheet and the resistance changescaused by the elongation and breakage of carbon fibers one by one. It is found that the periphery carbon fibers firstlybreak and cause an abrupt increase of resistance of carbon fiber sheet through changing the st ructure of the circuit ,and then the broken carbon fibers do not cont ribute to the resistance of carbon fibers anymore. The carbon fiberslocated inner of carbon fiber bundles also break later and still contact with the unbroken fibers at one point or severalpoint s , thus , these kinds of broken fibers carry on paths of the parallel circuit and still cont ribute to the resistance ofthe carbon fiber sheet . The ratio of un-contact broken fibers to all broken fibers was identified by fitting the testdata. The calculated results by using the variant2st ructure parallel circuit agree well with the test results.
The condition of fibers in carbon fiber sheet with epoxy resin mat rix used in civil inf rast ructure is different from that in indust rialized carbon fiber reinforced polymer/ plastic (CFRP) , i1 e. some fibers located inner ofthe fiber bundle are indeed without epoxy resin mat rix. The self-diagnostic function of carbon fiber sheet without epoxy resin mat rix was studied under a tensile loading condition. The experimental results indicate that the resistanceof carbon fiber sheet without epoxy resin mat rix linearly changes with the applied st rain , so the carbon fiber sheetcan act as a sensor to measure strain. A parallel variant2st ructure circuit , in which each carbon fiber bundle playsone path and a resistor , is employed to model the elect ric behavior of carbon fiber sheet and the resistance changescaused by the elongation and breakage of carbon fibers one by one. It is found that the periphery carbon fibers firstlybreak and cause an abrupt increase of resistance of carbon fiber sheet through changing the st ructure of the circuit ,and then the broken carbon fibers do not cont ribute to the resistance of carbon fibers anymore. The carbon fiberslocated inner of carbon fiber bundles also break later and still contact with the unbroken fibers at one point or severalpoint s , thus , these kinds of broken fibers carry on paths of the parallel circuit and still cont ribute to the resistance ofthe carbon fiber sheet . The ratio of un-contact broken fibers to all broken fibers was identified by fitting the testdata. The calculated results by using the variant2st ructure parallel circuit agree well with the test results.
2005, 22(2): 67-70.
Abstract:
An optical fiber sensor system , established by our laboratory , was used to measure the pressure changein the normal direction of prepreg layers to monitor the cure process. The optical fiber sensor is embedded in theprepreg and the change of output voltage can reflect the change of compacting pressure between fibers and the compacting degree of composite laminates. The experimental result s show that the system can not only reflect the pressure change in the normal direction of prepreg layers during cure molding process , but also provide some useful datafor layer consolidation and resin flowing. The data are very important to determine the pressurized point and optimize cure processing and cont rol the performances of composite parts.
An optical fiber sensor system , established by our laboratory , was used to measure the pressure changein the normal direction of prepreg layers to monitor the cure process. The optical fiber sensor is embedded in theprepreg and the change of output voltage can reflect the change of compacting pressure between fibers and the compacting degree of composite laminates. The experimental result s show that the system can not only reflect the pressure change in the normal direction of prepreg layers during cure molding process , but also provide some useful datafor layer consolidation and resin flowing. The data are very important to determine the pressurized point and optimize cure processing and cont rol the performances of composite parts.
2005, 22(2): 71-77.
Abstract:
A micro-heterogeneous , non-equilibrium and multi-sub-processes coupled model was presented based onlot s of experimental result s. Numerical analysis was used to study the behaviors of the Ti-C-Fe system in SHS. Thecalculated result s show that the relative density of compact has a dual-effect on SHS combustion behaviors , an optimal value exit s in some system , and a larger particle size of reactant s will lead to a relative slow chemical reactionand low combustion temperature. The result s show good agreement with experiment s.
A micro-heterogeneous , non-equilibrium and multi-sub-processes coupled model was presented based onlot s of experimental result s. Numerical analysis was used to study the behaviors of the Ti-C-Fe system in SHS. Thecalculated result s show that the relative density of compact has a dual-effect on SHS combustion behaviors , an optimal value exit s in some system , and a larger particle size of reactant s will lead to a relative slow chemical reactionand low combustion temperature. The result s show good agreement with experiment s.
2005, 22(2): 78-82.
Abstract:
A modified test rig of QM1000-Ⅱtype wet f riction performance tester was assembled by refitting thejigger equipment , adding the data acquisition program and the data processing program of the f riction torque. A paper-based f riction material reinforced by cellulose fiber was prepared by using the paper-making method. The relationship between load and f riction torque characteristics and the effect of load on the static coefficient and dynamiccoefficient of f riction of paper-based f riction material were investigated. The result s show that the torque magnitudeof both static and dynamic f riction increases with the increasing of load , the static coefficient of f riction increases linearly and the dynamic coefficient of f riction declines as increasing of loads. The duration time of the torque curve ofstatic f riction is independent of loading. Experiment data of static torque are more accurate and more reliable by automatic method than by manual method. The experiment result s will have guide significance for design of operationparameters of a wet clutch and optimizing the composition formula of f riction materials.
A modified test rig of QM1000-Ⅱtype wet f riction performance tester was assembled by refitting thejigger equipment , adding the data acquisition program and the data processing program of the f riction torque. A paper-based f riction material reinforced by cellulose fiber was prepared by using the paper-making method. The relationship between load and f riction torque characteristics and the effect of load on the static coefficient and dynamiccoefficient of f riction of paper-based f riction material were investigated. The result s show that the torque magnitudeof both static and dynamic f riction increases with the increasing of load , the static coefficient of f riction increases linearly and the dynamic coefficient of f riction declines as increasing of loads. The duration time of the torque curve ofstatic f riction is independent of loading. Experiment data of static torque are more accurate and more reliable by automatic method than by manual method. The experiment result s will have guide significance for design of operationparameters of a wet clutch and optimizing the composition formula of f riction materials.
2005, 22(2): 83-86.
Abstract:
The preparation of biomimetic bone-like HAp/ Col composite by imitating in vit ro biomineralization andself-assembly process was investigated. Characterizations of the specimen indicate an even dispersion and preferredorientation of HAp nanocrystals on collagen mat rix , which confirmed a promising similarity of both composition andconfiguration to nature bone.
The preparation of biomimetic bone-like HAp/ Col composite by imitating in vit ro biomineralization andself-assembly process was investigated. Characterizations of the specimen indicate an even dispersion and preferredorientation of HAp nanocrystals on collagen mat rix , which confirmed a promising similarity of both composition andconfiguration to nature bone.
2005, 22(2): 87-90.
Abstract:
0-3 cement based piezoelect ric composites were fabricated by compressing technique using PMN andsulphoaluminate cement as raw materials. The piezoelect ric and dielect ric properties of the composites were investigated. The result s indicate that the dielect ric constant s of the composites are almost constant over the temperatureranges between - 30 ℃and 150 ℃, which exhibit s good dielect ric-temperature stability. But dielect ric dissipation increases as temperature increases. With increasing PMN content , the piezoelect ric and dielect ric properties of thecomposites increase. The bet ter performances of the composites are exhibited when PZT content exceeds 70 %.
0-3 cement based piezoelect ric composites were fabricated by compressing technique using PMN andsulphoaluminate cement as raw materials. The piezoelect ric and dielect ric properties of the composites were investigated. The result s indicate that the dielect ric constant s of the composites are almost constant over the temperatureranges between - 30 ℃and 150 ℃, which exhibit s good dielect ric-temperature stability. But dielect ric dissipation increases as temperature increases. With increasing PMN content , the piezoelect ric and dielect ric properties of thecomposites increase. The bet ter performances of the composites are exhibited when PZT content exceeds 70 %.
2005, 22(2): 91-97.
Abstract:
For metal phase Al in Al2O3 / Al composite is harmful to it s high temperature property , Al2O3 / SiC/ Ni/Al-Si multi-phase ceramic mat rix composites were synthesized by oxidizing and infilt rating Al-5Zn-10Si alloy meltinto SiC/ Ni porous preforms made by slip casting at high temperature. The phase composition , microst ructure andinterface characteristic of composites were investigated using optical microscope , XRD , SEM , EDS , etc. The result s show that the main phases of the composites are Al2O3 and SiC , while Al (Si) compound oxide , NiAl2O4 , Niand Al2Si alloy phase exist at the phase interface of Al2O3 or SiC. The compositions in different phase interfaces arecontinuous variety , which brings into being a multi-phase composites with vague-interface.
For metal phase Al in Al2O3 / Al composite is harmful to it s high temperature property , Al2O3 / SiC/ Ni/Al-Si multi-phase ceramic mat rix composites were synthesized by oxidizing and infilt rating Al-5Zn-10Si alloy meltinto SiC/ Ni porous preforms made by slip casting at high temperature. The phase composition , microst ructure andinterface characteristic of composites were investigated using optical microscope , XRD , SEM , EDS , etc. The result s show that the main phases of the composites are Al2O3 and SiC , while Al (Si) compound oxide , NiAl2O4 , Niand Al2Si alloy phase exist at the phase interface of Al2O3 or SiC. The compositions in different phase interfaces arecontinuous variety , which brings into being a multi-phase composites with vague-interface.
2005, 22(2): 98-102.
Abstract:
TiB2-Cu composite is higH2elect ric composite with high-intensity , but the preparation of dense TiB2-Cucomposite is quite difficult because of the bad wettability of TiB2-Cu. The influence of different materials systems onthe characteristics (temperature , speed of combustion , production , etc. ) of the production by SHS (Self-propagating High-temperature Synthesis) was investigated. Based on these , the SHS/ QP technique was developed and usedfor the preparation of dense TiB2-Cu composite. The additives of Mo and Fe improve the wettability , make theproduct s more uniform and decrease the pore ratio and the particle size.
TiB2-Cu composite is higH2elect ric composite with high-intensity , but the preparation of dense TiB2-Cucomposite is quite difficult because of the bad wettability of TiB2-Cu. The influence of different materials systems onthe characteristics (temperature , speed of combustion , production , etc. ) of the production by SHS (Self-propagating High-temperature Synthesis) was investigated. Based on these , the SHS/ QP technique was developed and usedfor the preparation of dense TiB2-Cu composite. The additives of Mo and Fe improve the wettability , make theproduct s more uniform and decrease the pore ratio and the particle size.
2005, 22(2): 103-108.
Abstract:
In order to develop light-weight biomimetic composites , the microst ructure of A1 dichotoma was investigated in detail. A three dimensional honeycomb-columniation model was proposed and several design concept s forfurther development of three dimensional composite st ructure were discussed. At the same time , the advantages andapplication possibility were described. The result s show that there is an integrity network-columniation st ructure inthe whole fore wings of A1 dichotoma. This network st ructure is made of air sacs , and although it present s theirregularity and diversification , it is almost similar to the honeycomb-shaped polygon st ructure.
In order to develop light-weight biomimetic composites , the microst ructure of A1 dichotoma was investigated in detail. A three dimensional honeycomb-columniation model was proposed and several design concept s forfurther development of three dimensional composite st ructure were discussed. At the same time , the advantages andapplication possibility were described. The result s show that there is an integrity network-columniation st ructure inthe whole fore wings of A1 dichotoma. This network st ructure is made of air sacs , and although it present s theirregularity and diversification , it is almost similar to the honeycomb-shaped polygon st ructure.
2005, 22(2): 109-115.
Abstract:
To understand the quasistatic and dynamic compressive mechanical properties of a kind of carbon fibertwo-dimensional orthogonal plain woven reinforced polymer mat rix composite , numbers of quasistatic and dynamiccompression experiment s in it s three principal directions (the vertical direction of the carbon cloth , and also the warpand fill directions in the carbon cloth) were conducted , by means of Inst ron apparatus and SHPB technology respectively. The compressive st ress2st rain curves and compressive st rength were achieved in each direction in a largest rain rate range (from st rain rate 10 -3 / s to about 103 / s) . The experimental result s show that the dynamic performance of this composite in each three principal directions has it s own characteristics : in the vertical direction ofthe carbon cloth , the mechanical property and the st rain rate effect are mat rix-dominated ; in the warp or fill direction in the carbon cloth , the carbon fiber and it s initial waviness master the mechanical property. Two formulas wereproposed to model the relationship of the compressive st rength and elastic modulus with the st rain rate.
To understand the quasistatic and dynamic compressive mechanical properties of a kind of carbon fibertwo-dimensional orthogonal plain woven reinforced polymer mat rix composite , numbers of quasistatic and dynamiccompression experiment s in it s three principal directions (the vertical direction of the carbon cloth , and also the warpand fill directions in the carbon cloth) were conducted , by means of Inst ron apparatus and SHPB technology respectively. The compressive st ress2st rain curves and compressive st rength were achieved in each direction in a largest rain rate range (from st rain rate 10 -3 / s to about 103 / s) . The experimental result s show that the dynamic performance of this composite in each three principal directions has it s own characteristics : in the vertical direction ofthe carbon cloth , the mechanical property and the st rain rate effect are mat rix-dominated ; in the warp or fill direction in the carbon cloth , the carbon fiber and it s initial waviness master the mechanical property. Two formulas wereproposed to model the relationship of the compressive st rength and elastic modulus with the st rain rate.
2005, 22(2): 116-120.
Abstract:
Three types of carbon-fibre epoxy composites , HT7/ 5228 , HT3/ N Y9200G and HT3/ 5224 , were interlayer toughened with thermoplastic particles. In order to improve compression st rength af ter impacting (CAI) andevaluate damage resistance , a quasi-static indentation (QSI) test was conducted. The experimental result s indicatethat the interlayer zones formed by particles and epoxy can significantly suppress delamination and crack propagation. Average delamination onset energy eⅡc is significantly improved. The relation between indent depth and contactforce shows that the interleaved specimen achieves a smaller damage area at the expense of greater indent depth inthe local region. The toughening mechanism is chiefly as follows : geomet rical effect of interlayers , crack path kinking and deflection , and crack tip shielding. A large amount of f racture energy is absorbed by ductile deformationand ultimate failure of the particles.
Three types of carbon-fibre epoxy composites , HT7/ 5228 , HT3/ N Y9200G and HT3/ 5224 , were interlayer toughened with thermoplastic particles. In order to improve compression st rength af ter impacting (CAI) andevaluate damage resistance , a quasi-static indentation (QSI) test was conducted. The experimental result s indicatethat the interlayer zones formed by particles and epoxy can significantly suppress delamination and crack propagation. Average delamination onset energy eⅡc is significantly improved. The relation between indent depth and contactforce shows that the interleaved specimen achieves a smaller damage area at the expense of greater indent depth inthe local region. The toughening mechanism is chiefly as follows : geomet rical effect of interlayers , crack path kinking and deflection , and crack tip shielding. A large amount of f racture energy is absorbed by ductile deformationand ultimate failure of the particles.
2005, 22(2): 121-124.
Abstract:
The explicit expression for effective elect roelastic moduli of piezoelect ric ceramic/ polymer biphase piezocomposite was obtained by employing Eshelby’s model and Mori-Tanaka average field theory. The expression canreflect physical insight for piezocomposites. As a practical example , the coupled elect roelastic behaviors were analyzed for a piezoelect ric elliptic cylindrical fiber reinforced polymer composite. The result s show that the averageelect roelastic moduli depend on the coupled elect roelastic effect s which have relations to the connectivity , volumef raction and the shape of piezoelect ric inclusions. The origin of the coupling effect s is related to the existence of mismatch elect roelastic moduli of constituent s.
The explicit expression for effective elect roelastic moduli of piezoelect ric ceramic/ polymer biphase piezocomposite was obtained by employing Eshelby’s model and Mori-Tanaka average field theory. The expression canreflect physical insight for piezocomposites. As a practical example , the coupled elect roelastic behaviors were analyzed for a piezoelect ric elliptic cylindrical fiber reinforced polymer composite. The result s show that the averageelect roelastic moduli depend on the coupled elect roelastic effect s which have relations to the connectivity , volumef raction and the shape of piezoelect ric inclusions. The origin of the coupling effect s is related to the existence of mismatch elect roelastic moduli of constituent s.
2005, 22(2): 125-129.
Abstract:
Based on the piezoelect ric equation , the relationships between D33 of composite materials and the respective properties of different components were calculated by employing the Dilute serial material model . The analyzed data were compared with the experimental D33 results. The result s showed that improving the dielect ric couplecan enhance the piezoelect ric properties effectively and the particle sizes also influence the materials’properties.
Based on the piezoelect ric equation , the relationships between D33 of composite materials and the respective properties of different components were calculated by employing the Dilute serial material model . The analyzed data were compared with the experimental D33 results. The result s showed that improving the dielect ric couplecan enhance the piezoelect ric properties effectively and the particle sizes also influence the materials’properties.
2005, 22(2): 130-136.
Abstract:
The micro-analysis of a typical and periodical cell selected from the panel was used to calculate the macro-parameters of the sandwich panels. The temperature and st ress fields were analyzed by a three-dimensional finiteelement method and the thermo-mechanical parameters of sandwich panels were given considering heat t ransfer byradiation inner the honeycomb core. The influence of the honeycomb core on heat conductivities , thermal expansioncoefficient s , elasticity properties and bending stiffness of sandwich panels was also investigated. The result s showthat the heat conductivity along the thickness was different from that obtained by t raditional methods , all mechanicalproperties except D12 could use conventional result s to approximate and the effect of the honeycomb core on thermalexpansion could not be neglected.
The micro-analysis of a typical and periodical cell selected from the panel was used to calculate the macro-parameters of the sandwich panels. The temperature and st ress fields were analyzed by a three-dimensional finiteelement method and the thermo-mechanical parameters of sandwich panels were given considering heat t ransfer byradiation inner the honeycomb core. The influence of the honeycomb core on heat conductivities , thermal expansioncoefficient s , elasticity properties and bending stiffness of sandwich panels was also investigated. The result s showthat the heat conductivity along the thickness was different from that obtained by t raditional methods , all mechanicalproperties except D12 could use conventional result s to approximate and the effect of the honeycomb core on thermalexpansion could not be neglected.
2005, 22(2): 137-142.
Abstract:
To investigate the subsiding of honeycomb sandwich panel or beam , a theoretic model of a circular cellhoneycomb subjected to axial loading is developed. The formulas of the critical press st ress on the skin are derived ,a perfect design theory of honeycomb sandwich panel or beam is established , and a novel method of iterative optimization design is presented. Finally , the result with a numeric simulation method verifies that the theoretic model inthis paper is accurate and efficient . The study will provide an important theoretical basis for advanced improvementof the honeycomb sandwich plate or beam.
To investigate the subsiding of honeycomb sandwich panel or beam , a theoretic model of a circular cellhoneycomb subjected to axial loading is developed. The formulas of the critical press st ress on the skin are derived ,a perfect design theory of honeycomb sandwich panel or beam is established , and a novel method of iterative optimization design is presented. Finally , the result with a numeric simulation method verifies that the theoretic model inthis paper is accurate and efficient . The study will provide an important theoretical basis for advanced improvementof the honeycomb sandwich plate or beam.
2005, 22(2): 143-147.
Abstract:
According to the geomet ric form of a shell element , geomet ric formulations of the shell element are deduced. This paper supposes that temperature has quadratic variation through layers of the shell element , and givesthe expression of temperature functions in given boundary conditions. In this paper , the orthot ropic feature of material property is considered ; heat conductivity can be t ransformed from material coordinates into element coordinatesand then the formulations of thermal analysis are deduced. Finite element formulations are established using 3D-degenerated shell element and then thermal shell formulations are gotten. Thus this method can change 3D problemsinto 2D problems. Then a program is designed to test this theory. It not only has the same precision with isoparamet ric element , but also improves the efficiency of analysis. It also can save memory of computer and running time.The numerical result s are compared with ANSYS result s and are satisfactory.
According to the geomet ric form of a shell element , geomet ric formulations of the shell element are deduced. This paper supposes that temperature has quadratic variation through layers of the shell element , and givesthe expression of temperature functions in given boundary conditions. In this paper , the orthot ropic feature of material property is considered ; heat conductivity can be t ransformed from material coordinates into element coordinatesand then the formulations of thermal analysis are deduced. Finite element formulations are established using 3D-degenerated shell element and then thermal shell formulations are gotten. Thus this method can change 3D problemsinto 2D problems. Then a program is designed to test this theory. It not only has the same precision with isoparamet ric element , but also improves the efficiency of analysis. It also can save memory of computer and running time.The numerical result s are compared with ANSYS result s and are satisfactory.
2005, 22(2): 148-159.
Abstract:
It is well known that design and analysis for the ultimate load carrying capacity of a st ructure made of isot ropic materials can be accomplished only based on a st ress failure criterion (e. g. the first or the fourth st rengththeory int roduced in a mechanics of materials text book) . This is , however , not t rue for composites in general. It ispointed out in the paper that the ultimate failure of laminated composite beams subjected to bending cannot be figured out only based on a st ress failure criterion. Thus , the design and analysis for the ultimate load carrying capacityof composite st ructures require not only a st ress failure criterion but also a critical deformation related condition. Toshow this , some experimental evidences are summarized in the paper. Another purpose of this paper is to presentsome latest result s achieved by the authors in the relevant research areas especially in determination of the ultimatebending st rength of laminated composites. A number of challenging topics are also addressed in the paper.
It is well known that design and analysis for the ultimate load carrying capacity of a st ructure made of isot ropic materials can be accomplished only based on a st ress failure criterion (e. g. the first or the fourth st rengththeory int roduced in a mechanics of materials text book) . This is , however , not t rue for composites in general. It ispointed out in the paper that the ultimate failure of laminated composite beams subjected to bending cannot be figured out only based on a st ress failure criterion. Thus , the design and analysis for the ultimate load carrying capacityof composite st ructures require not only a st ress failure criterion but also a critical deformation related condition. Toshow this , some experimental evidences are summarized in the paper. Another purpose of this paper is to presentsome latest result s achieved by the authors in the relevant research areas especially in determination of the ultimatebending st rength of laminated composites. A number of challenging topics are also addressed in the paper.
2005, 22(2): 160-165.
Abstract:
A finite element model of 3-3 piezocomposites was established according to the homogenization method ,which combined the techniques relying upon representative volume element ( RVE) and periodic boundary conditions. Numerical result s of the model are in agreement with the previous experimental work. In cont rast to the analytical model , the finite element model gives more accurate result s. The effect of material parameters , such as polymer volume f raction , Poisson ratio , Young’s modulus and mat rix geomet ry , on the hydrostatic properties was analyzed based on the model.
A finite element model of 3-3 piezocomposites was established according to the homogenization method ,which combined the techniques relying upon representative volume element ( RVE) and periodic boundary conditions. Numerical result s of the model are in agreement with the previous experimental work. In cont rast to the analytical model , the finite element model gives more accurate result s. The effect of material parameters , such as polymer volume f raction , Poisson ratio , Young’s modulus and mat rix geomet ry , on the hydrostatic properties was analyzed based on the model.
2005, 22(2): 166-171.
Abstract:
Based on the characters of optimal design for the composite grid-stiffened st ructures (A GS) , such asmulti-loading cases , multi-const raints , mixed discrete-continuous design variables , etc , a st rategy of optimalanalysis was proposed. Some improvement s about genetic and simplex algorithms were made , and an optimal problem with the buckling and st rain const raint s was t ransformed into a non-const rained optimal problem by the exteriorpenalty function scheme. Based on the foregoing measures , a new hybrid genetic algorithm by conjunction of geneticapproach with simplex algorithm was developed successfully. Comparison of the benchmark result s given by t raditional genetic algorithms showed effectiveness of the present algorithm. Some numerical examples were discussedabout the effect s of st rength const raint s and grid configurations upon the optimal result s. It is concluded that globalbuckling const raint is the key factor for identifying safety of AGS , and the algorithm provided is convenient and efficient .
Based on the characters of optimal design for the composite grid-stiffened st ructures (A GS) , such asmulti-loading cases , multi-const raints , mixed discrete-continuous design variables , etc , a st rategy of optimalanalysis was proposed. Some improvement s about genetic and simplex algorithms were made , and an optimal problem with the buckling and st rain const raint s was t ransformed into a non-const rained optimal problem by the exteriorpenalty function scheme. Based on the foregoing measures , a new hybrid genetic algorithm by conjunction of geneticapproach with simplex algorithm was developed successfully. Comparison of the benchmark result s given by t raditional genetic algorithms showed effectiveness of the present algorithm. Some numerical examples were discussedabout the effect s of st rength const raint s and grid configurations upon the optimal result s. It is concluded that globalbuckling const raint is the key factor for identifying safety of AGS , and the algorithm provided is convenient and efficient .
