2006 Vol. 23, No. 4
2006, 23(4): 1-8.
Abstract:
The st ress-sensing cement composite material , which is mainly composed of special conducting materialor nano-particle and t raditional cement or mortar , is a new kind of material with piezoresistive effect . Using the special performance of this material that between it s specific resistance and compressive st ress there is a correspondingrelationship , a new kind of sensor can be made. As having character of low cost , high durability and good compatibility with concrete , sensors made of the st ress-sensing cement composite material have great potential to be used aslong time health monitors of concrete st ructures. In this paper , the progress in st resssensing cement compositematerials , such as t reating and selecting of the raw material , mixing technology , testing method of specific resistance , and testing system of the st ress-sensing cement sensor , was summarized. And the problems , i. e. stabilityand discreteness of specific resistance and specific resistanceps changing rules under multiaxial st resses and so on ,should be further resolved so as to promote their applications to practical engineering.
The st ress-sensing cement composite material , which is mainly composed of special conducting materialor nano-particle and t raditional cement or mortar , is a new kind of material with piezoresistive effect . Using the special performance of this material that between it s specific resistance and compressive st ress there is a correspondingrelationship , a new kind of sensor can be made. As having character of low cost , high durability and good compatibility with concrete , sensors made of the st ress-sensing cement composite material have great potential to be used aslong time health monitors of concrete st ructures. In this paper , the progress in st resssensing cement compositematerials , such as t reating and selecting of the raw material , mixing technology , testing method of specific resistance , and testing system of the st ress-sensing cement sensor , was summarized. And the problems , i. e. stabilityand discreteness of specific resistance and specific resistanceps changing rules under multiaxial st resses and so on ,should be further resolved so as to promote their applications to practical engineering.
2006, 23(4): 9-14.
Abstract:
The present paper deals with a primary study on the impregnation property in the plane of the unidirectional fabric with pure epoxy resin. The effect of the parameters on the dynamics of capillary impregnation wasresearched , such as temperatures , and fiber-resin surface impregnation angles. And a data t reatment method wasproposed to avoid the influence of meniscus at the bottom of the fabric. The result s show that velocity of impregnation can be improved by increasing the temperatures and the impregnation angles.
The present paper deals with a primary study on the impregnation property in the plane of the unidirectional fabric with pure epoxy resin. The effect of the parameters on the dynamics of capillary impregnation wasresearched , such as temperatures , and fiber-resin surface impregnation angles. And a data t reatment method wasproposed to avoid the influence of meniscus at the bottom of the fabric. The result s show that velocity of impregnation can be improved by increasing the temperatures and the impregnation angles.
2006, 23(4): 15-18.
Abstract:
The 0-3 piezoelect ric composites were fabricated with the polyurethane ( PU) doped with polyaniline( PANI) by in si tu polymerization as mat rix and lead zirconate titanate ( PZT) as function phase. The polarizationand elect rical properties of the composites were studied. The result s show that the polarization and piezoelect ricproperties of 0-3 composites can effectively increase with an appropriate volume f raction of PANI. The piezoelect ricconstant ( d33 ) and elect romechanical coupling coefficient ( kp ) rapidly increase with increasing the PANI content . Atthe PANI volume f raction of 4 % the d33 and kp of the composite are 34 pC/ N and 0.25 , respectively , and show themaximum values. The dielect ric constant and dielect ric loss of the composites rise with increasing the content ofPANI.
The 0-3 piezoelect ric composites were fabricated with the polyurethane ( PU) doped with polyaniline( PANI) by in si tu polymerization as mat rix and lead zirconate titanate ( PZT) as function phase. The polarizationand elect rical properties of the composites were studied. The result s show that the polarization and piezoelect ricproperties of 0-3 composites can effectively increase with an appropriate volume f raction of PANI. The piezoelect ricconstant ( d33 ) and elect romechanical coupling coefficient ( kp ) rapidly increase with increasing the PANI content . Atthe PANI volume f raction of 4 % the d33 and kp of the composite are 34 pC/ N and 0.25 , respectively , and show themaximum values. The dielect ric constant and dielect ric loss of the composites rise with increasing the content ofPANI.
2006, 23(4): 19-23.
Abstract:
This paper mainly studies the sound absorption properties of a new type of multilayered polymer composite materials with nonplanar interfaces at different temperatures and pressures. The new type of multilayered composites with the nonplanar interfaces and a t raditional multilayered composite with a planar interface were preparedand their sound absorption coefficient s were measured in the sound tube. The result s show that the sound absorptioncoefficient s of the new type of absorbers are higher than those of the t raditional absorber within the interested f requency range. The sound absorption coefficient peak values of the new type of absorbers shif t to the low f requencieswith temperatures increasing , but they are not sensitive to the pressures. It is suggested that appropriately designing the interface shape of multilayer polymer composite materials can enhance their sound absorption properties
This paper mainly studies the sound absorption properties of a new type of multilayered polymer composite materials with nonplanar interfaces at different temperatures and pressures. The new type of multilayered composites with the nonplanar interfaces and a t raditional multilayered composite with a planar interface were preparedand their sound absorption coefficient s were measured in the sound tube. The result s show that the sound absorptioncoefficient s of the new type of absorbers are higher than those of the t raditional absorber within the interested f requency range. The sound absorption coefficient peak values of the new type of absorbers shif t to the low f requencieswith temperatures increasing , but they are not sensitive to the pressures. It is suggested that appropriately designing the interface shape of multilayer polymer composite materials can enhance their sound absorption properties
2006, 23(4): 24-28.
Abstract:
The effect s of proton implantation on the t ribological behavior of MoS2 / PES-C composites werestudied. The st ructural changes of the composites caused by the proton implantation were studied by using inf raredspect ra and X-ray photoelect ron spect roscopy (XPS) . The result s show that part of PES-C degrades af ter protonimplantation , and a carbon- rich st ructure forms on the surface of the composites , whereas there are no obviouschemical changes for MoS2 during the implantation process. The f riction and wear test s reveal that the wear-resistance of the composites could be improved by proton implantation. Especially when the dose reaches 1. 25 ×1016 ions/ cm2 ,its friction coefficient and wear rate decrease simultaneously. The wear mechanism changes f rom adhesive wear andplastic deformation for the un-implanted composites to fatigue wear for the implanted ones.
The effect s of proton implantation on the t ribological behavior of MoS2 / PES-C composites werestudied. The st ructural changes of the composites caused by the proton implantation were studied by using inf raredspect ra and X-ray photoelect ron spect roscopy (XPS) . The result s show that part of PES-C degrades af ter protonimplantation , and a carbon- rich st ructure forms on the surface of the composites , whereas there are no obviouschemical changes for MoS2 during the implantation process. The f riction and wear test s reveal that the wear-resistance of the composites could be improved by proton implantation. Especially when the dose reaches 1. 25 ×1016 ions/ cm2 ,its friction coefficient and wear rate decrease simultaneously. The wear mechanism changes f rom adhesive wear andplastic deformation for the un-implanted composites to fatigue wear for the implanted ones.
2006, 23(4): 29-35.
Abstract:
High-performance carbon fiber has been widely used in commercial and military fields because of its highstrength , light weight and high stiffness. However , the application of higher performance carbon fiber ( e. g. T800)would cause worse mechanical performances because of the ext reme inertness of it s surface caused by the alignmentof graphitic crystallites. In order to produce the high-performance resin mat rix , which can bond T800 carbon fiber(CF) well , the sizing of T800 CF was analyzed. The effect of resin mat rix’ s st ructure and property on T800 CFcomposite was studied based on the analysis. Meanwhile , the mechanical property and thermal mechanical propertyof the resin and it s carbon fiber composite were analyzed. The result s show that T800 sizing possesses high contentof ester , which can possess excellent interfacial properties with glyceride epoxy. With the help of the optimized resinsystem , the T800 CF composite possesses excellent interfacial properties and heat-resistance properties. The interlaminar shear st rength ( ILSS) of the composite is 138 MPa , the tensile st rength of NOL rings is 2530 MPa , and theglass t ransition temperature ( Tg ) is 213 ℃.
High-performance carbon fiber has been widely used in commercial and military fields because of its highstrength , light weight and high stiffness. However , the application of higher performance carbon fiber ( e. g. T800)would cause worse mechanical performances because of the ext reme inertness of it s surface caused by the alignmentof graphitic crystallites. In order to produce the high-performance resin mat rix , which can bond T800 carbon fiber(CF) well , the sizing of T800 CF was analyzed. The effect of resin mat rix’ s st ructure and property on T800 CFcomposite was studied based on the analysis. Meanwhile , the mechanical property and thermal mechanical propertyof the resin and it s carbon fiber composite were analyzed. The result s show that T800 sizing possesses high contentof ester , which can possess excellent interfacial properties with glyceride epoxy. With the help of the optimized resinsystem , the T800 CF composite possesses excellent interfacial properties and heat-resistance properties. The interlaminar shear st rength ( ILSS) of the composite is 138 MPa , the tensile st rength of NOL rings is 2530 MPa , and theglass t ransition temperature ( Tg ) is 213 ℃.
2006, 23(4): 36-40.
Abstract:
The mechanics , f riction and wear properties of graphite/ MoS2 filled Ekonol/ PTFE composites werestudied. The result shows that the addition of graphite/ MoS2 not only increases the mechanical properties ofEkonol/ PTFE composites , but also causes the f riction coefficient to increase , the wear volume to decrease , and theabrasive resistance to remarkably increase. When Ekonol and graphite/ MoS2 mass f ractions are 5 % and 8 % , thetensile st rength and bend st rength of composites increase 31 % and 41 % , and the hardness increases 713 % too. Thewear mechanism of Ekonol/ graphite/ MoS2 / PTFE composites is adhesive wear , as indicated by SEM analysis of theworn surface.
The mechanics , f riction and wear properties of graphite/ MoS2 filled Ekonol/ PTFE composites werestudied. The result shows that the addition of graphite/ MoS2 not only increases the mechanical properties ofEkonol/ PTFE composites , but also causes the f riction coefficient to increase , the wear volume to decrease , and theabrasive resistance to remarkably increase. When Ekonol and graphite/ MoS2 mass f ractions are 5 % and 8 % , thetensile st rength and bend st rength of composites increase 31 % and 41 % , and the hardness increases 713 % too. Thewear mechanism of Ekonol/ graphite/ MoS2 / PTFE composites is adhesive wear , as indicated by SEM analysis of theworn surface.
2006, 23(4): 41-46.
Abstract:
The green bodies of carbon nanotubes/ hydroxyapatite (CNTs/ HA) composite were prepared by gel casting process. The effect s of p H , dispersant , content of solid in slurry and the dispersing process on the slurryand the properties of the green bodies were researched. The mechanical properties were tested , and the microst ructure was analysed using SEM. It is found that the p H value of the slurry should be cont rolled in the range 10 to 12.The fluidness of HA slurry is the best as the concent ration of NH4- PMAA is 0. 6 %. The viscosity of CNTs/ HAslurry reaches the lowest value as the concent ration of sodium dodecanesulphonate which is called SDS for shortchanges f rom SDS/ CNTs = 1 % to SDS/ CNTs = 2 %. The content of solid in CNTs/ HA slurry reaches 55 % and thebending st rength of the green bodies of CNTs/ HA composite reaches 57. 403 MPa by a ball mill process.
The green bodies of carbon nanotubes/ hydroxyapatite (CNTs/ HA) composite were prepared by gel casting process. The effect s of p H , dispersant , content of solid in slurry and the dispersing process on the slurryand the properties of the green bodies were researched. The mechanical properties were tested , and the microst ructure was analysed using SEM. It is found that the p H value of the slurry should be cont rolled in the range 10 to 12.The fluidness of HA slurry is the best as the concent ration of NH4- PMAA is 0. 6 %. The viscosity of CNTs/ HAslurry reaches the lowest value as the concent ration of sodium dodecanesulphonate which is called SDS for shortchanges f rom SDS/ CNTs = 1 % to SDS/ CNTs = 2 %. The content of solid in CNTs/ HA slurry reaches 55 % and thebending st rength of the green bodies of CNTs/ HA composite reaches 57. 403 MPa by a ball mill process.
2006, 23(4): 47-51.
Abstract:
Mimicking the st ructure of nacre , the poly(t ripropylene glycol diacrylate , TPGDA) / SiO2 nanocompositethin film was prepared using an evaporation-induced self -assembly procedure on the quartz glass subst rate. Thest ructure of the nanocomposite thin film was characterized by means of FT- IR spect roscope , X- ray diff raction(XRD) and t ransmission elect ron microscope ( TEM) . The f rictional force behavior of the nanocomposite thin filmwas tested. The formation mechanism of the poly ( TPGDA) / SiO2 nanocomposite thin film was investigated. The results indicate that the thin film is composed of organic and inorganic layers in alternately orderly arrangement . Thedistance between the organic layer and inorganic layer is 2. 69 nm before polymerization and 2. 35 nm af ter polymerization. Moreover , the polymerized film has preferable antiwear property.
Mimicking the st ructure of nacre , the poly(t ripropylene glycol diacrylate , TPGDA) / SiO2 nanocompositethin film was prepared using an evaporation-induced self -assembly procedure on the quartz glass subst rate. Thest ructure of the nanocomposite thin film was characterized by means of FT- IR spect roscope , X- ray diff raction(XRD) and t ransmission elect ron microscope ( TEM) . The f rictional force behavior of the nanocomposite thin filmwas tested. The formation mechanism of the poly ( TPGDA) / SiO2 nanocomposite thin film was investigated. The results indicate that the thin film is composed of organic and inorganic layers in alternately orderly arrangement . Thedistance between the organic layer and inorganic layer is 2. 69 nm before polymerization and 2. 35 nm af ter polymerization. Moreover , the polymerized film has preferable antiwear property.
2006, 23(4): 52-59.
Abstract:
In order to completely know the microst ructure and physical characteristics of silicon dioxide/ wood composites , X-ray diff raction (XRD) and energy dispersive X-ray analyzer ( EDAX) are used for studying the microst ructure of silicon dioxide/ wood composites made by sol-gel. St ress relaxation , dielect ric properties , thermogravimet ry and surface microhardness mensurating methods are used for analyzing their physical properties. Theresult s show that silicon dioxide exist s in the cell wall of wood for silicon dioxide/ wood composites made by thewood of moisture content under the fibre saturation point . Crystallinity decreases , while the mole f raction of silicondioxide increases with the enhancement of mass gain. The position of XRD spect ra peak is the same as the unt reatment . The magnitude of st ress relaxation of silicon dioxide/ wood composites is less than the unt reatment . There isa cross-linking between wood molecule and silicon dioxide. The dielect ric constant decreases , while the dielect ricloss factor increases firstly , then decreases with increasing f requency. The f requency of the dielect ric loss factorreaching the maximum value is in the vicinity of log f = 6. 5 Hz at room temperature. The start temperature of fastthermogravimet ry of the silicon dioxide/ wood composites rises in the thermogravimet ry course , their remainder massincreases in the end , and their surface microhardness increases.
In order to completely know the microst ructure and physical characteristics of silicon dioxide/ wood composites , X-ray diff raction (XRD) and energy dispersive X-ray analyzer ( EDAX) are used for studying the microst ructure of silicon dioxide/ wood composites made by sol-gel. St ress relaxation , dielect ric properties , thermogravimet ry and surface microhardness mensurating methods are used for analyzing their physical properties. Theresult s show that silicon dioxide exist s in the cell wall of wood for silicon dioxide/ wood composites made by thewood of moisture content under the fibre saturation point . Crystallinity decreases , while the mole f raction of silicondioxide increases with the enhancement of mass gain. The position of XRD spect ra peak is the same as the unt reatment . The magnitude of st ress relaxation of silicon dioxide/ wood composites is less than the unt reatment . There isa cross-linking between wood molecule and silicon dioxide. The dielect ric constant decreases , while the dielect ricloss factor increases firstly , then decreases with increasing f requency. The f requency of the dielect ric loss factorreaching the maximum value is in the vicinity of log f = 6. 5 Hz at room temperature. The start temperature of fastthermogravimet ry of the silicon dioxide/ wood composites rises in the thermogravimet ry course , their remainder massincreases in the end , and their surface microhardness increases.
2006, 23(4): 60-64.
Abstract:
The wettability of a reaction bonded SiC/ Co-Cr system was studied by the sessile drop technique in highvacuum. The effect of Cr content and technological parameters including wetting temperature and dwelling time onthe wettability of the system was investigated. Compared with the reaction bonded (RB) SiC/ pure Co system , thewettability of the system is remarkably improved by adding active element Cr. The relatively small contact angles ofthe RB SiC/ Co-Cr system are obtained with the Cr content of 5 % , 7 % and 42 % , respectively. Wetting temperatureand dwelling time st rongly affect the contact angle. The experimental result s show that the wetting processes ofboth RB SiC/ pure Co system and RB SiC/ Co-Cr system belong to reactive wetting. Microst ructure study and XRDphase analysis indicate that interfacial reactions take place in the RB SiC/ pure Co system , leading to the formation ofCoSi , and resulting in the decreasing of the contact angle ; but for the RB SiC/ Co-Cr system , interfacial reactionscause the formation of Cr23C6 , leading to the decreasing of the interfacial energy of the system , and consequently thewettability of the system is improved.
The wettability of a reaction bonded SiC/ Co-Cr system was studied by the sessile drop technique in highvacuum. The effect of Cr content and technological parameters including wetting temperature and dwelling time onthe wettability of the system was investigated. Compared with the reaction bonded (RB) SiC/ pure Co system , thewettability of the system is remarkably improved by adding active element Cr. The relatively small contact angles ofthe RB SiC/ Co-Cr system are obtained with the Cr content of 5 % , 7 % and 42 % , respectively. Wetting temperatureand dwelling time st rongly affect the contact angle. The experimental result s show that the wetting processes ofboth RB SiC/ pure Co system and RB SiC/ Co-Cr system belong to reactive wetting. Microst ructure study and XRDphase analysis indicate that interfacial reactions take place in the RB SiC/ pure Co system , leading to the formation ofCoSi , and resulting in the decreasing of the contact angle ; but for the RB SiC/ Co-Cr system , interfacial reactionscause the formation of Cr23C6 , leading to the decreasing of the interfacial energy of the system , and consequently thewettability of the system is improved.
2006, 23(4): 65-71.
Abstract:
The composite elect roforming technology was employed to fabricate nano-sized alumina particles (nano-Al2O3 ) reinforced copper composite in copper sulfate sulfuric acid plating solution. The surface , f racture and wearsurface morphologies were observed by scanning elect ron microscopy (SEM) , and the microst ructure was observedby t ransmission elect ron microscopy ( TEM) . Microhardness , tensile property , wear resistance and elect rical resistivity ( Er ) were examined. The result s show that Al2O3 particles and their agglomerations with nano size disperse inthe copper mat rix and have good bonding with copper mat rix. The microhardness of composite can be 42 % higherthan that of elect roformed pure copper. The tensile st rength and the extensibility reach 385 MPa and 26 % , respectively , as the nano-Al2O3 mass f raction is 1. 26 %. Wear resistance of composite is enhanced obviously. Comparedwith elect roformed pure copper , the increase amplitude in elect rical resistivity of the composite is below 6 %.
The composite elect roforming technology was employed to fabricate nano-sized alumina particles (nano-Al2O3 ) reinforced copper composite in copper sulfate sulfuric acid plating solution. The surface , f racture and wearsurface morphologies were observed by scanning elect ron microscopy (SEM) , and the microst ructure was observedby t ransmission elect ron microscopy ( TEM) . Microhardness , tensile property , wear resistance and elect rical resistivity ( Er ) were examined. The result s show that Al2O3 particles and their agglomerations with nano size disperse inthe copper mat rix and have good bonding with copper mat rix. The microhardness of composite can be 42 % higherthan that of elect roformed pure copper. The tensile st rength and the extensibility reach 385 MPa and 26 % , respectively , as the nano-Al2O3 mass f raction is 1. 26 %. Wear resistance of composite is enhanced obviously. Comparedwith elect roformed pure copper , the increase amplitude in elect rical resistivity of the composite is below 6 %.
2006, 23(4): 72-77.
Abstract:
W/ Cu functionally graded material was prepared by infilt ration. The W skeleton with graded porositywas fabricated using water cooking pore-agent , and then molten copper was infilt rated into the W skeleton. The dist ributions of the element s in the longitudinal section was tested. The result s show that the dist ributions of concent ration of copper and tungsten were gradient in the longitudinal section. The circumstance of service was simulatedby water quenching and the thermal st ress was analyzed. The result s show that the maximum thermal st ress is always in the tungsten-rich region.
W/ Cu functionally graded material was prepared by infilt ration. The W skeleton with graded porositywas fabricated using water cooking pore-agent , and then molten copper was infilt rated into the W skeleton. The dist ributions of the element s in the longitudinal section was tested. The result s show that the dist ributions of concent ration of copper and tungsten were gradient in the longitudinal section. The circumstance of service was simulatedby water quenching and the thermal st ress was analyzed. The result s show that the maximum thermal st ress is always in the tungsten-rich region.
2006, 23(4): 78-82.
Abstract:
The Al mat rix composite material reinforced by SiC particle of different sizes was prepared by elect romagnetic cent rifugal casting ( EMCC) . The different size particle dist ribution affected by different exciting voltageswas studied. The hardness and abrasion resistance of different size particle reinforced composite were also studied.The result s show that it is much easier for the smaller particles to scatter evenly with the same exciting voltage byelect romagnetic stirring ( EMS) . The same size particles dist ribute more evenly with 100 V exciting voltage thanwith 50 V exciting voltage. The hardness and abrasion resistance of the composite are improved greatly by the moreeven dist ribution of smaller particles.
The Al mat rix composite material reinforced by SiC particle of different sizes was prepared by elect romagnetic cent rifugal casting ( EMCC) . The different size particle dist ribution affected by different exciting voltageswas studied. The hardness and abrasion resistance of different size particle reinforced composite were also studied.The result s show that it is much easier for the smaller particles to scatter evenly with the same exciting voltage byelect romagnetic stirring ( EMS) . The same size particles dist ribute more evenly with 100 V exciting voltage thanwith 50 V exciting voltage. The hardness and abrasion resistance of the composite are improved greatly by the moreeven dist ribution of smaller particles.
2006, 23(4): 83-87.
Abstract:
The high temperature thermal chemical ablative result s for carbon composite materials were calculated byminimization of the energy function. The experiment s of the high temperature thermal chemical ablation with archeater and plasma torch were carried out . The spect rum diagnoses of gaseous ablative result s for carbon compositematerials were made . The gaseous ablative result s of spect rum diagnoses are consistent with those of calculation byminimization of the energy function. It confirmed the validity of the thermal chemical ablative calculation by minimization of the energy function for carbon composite materials further. The method calculated the thermal chemicalgaseous ablative results not only for carbon composite materials , but also for complex hybrid carbon composite materials.
The high temperature thermal chemical ablative result s for carbon composite materials were calculated byminimization of the energy function. The experiment s of the high temperature thermal chemical ablation with archeater and plasma torch were carried out . The spect rum diagnoses of gaseous ablative result s for carbon compositematerials were made . The gaseous ablative result s of spect rum diagnoses are consistent with those of calculation byminimization of the energy function. It confirmed the validity of the thermal chemical ablative calculation by minimization of the energy function for carbon composite materials further. The method calculated the thermal chemicalgaseous ablative results not only for carbon composite materials , but also for complex hybrid carbon composite materials.
2006, 23(4): 88-94.
Abstract:
Ag nanoparticles were synthesized in a nanoreactor formed by an adsorption layer on the silica surface.The effect s of concent ration of water on the process of adsorption and reaction were analyzed. When the mass fraction of NaOH keeps constant , the equilibrium content of NaOH adsorbed on SiO2 increases with the increase of concent ration of water , which changes f rom 0 to 1. 00 %. Two jump regions of equilibrium content are found f rom 0 to0. 05 % and f rom 0. 25 % to 0. 50 %. Analysis by XRD and TEM indicates that the agglomeration of Ag or Ag2Oparticles becomes more moderate , it s dispersion on the surface SiO2 becomes more uniform , and it s grain size becomes smaller with the increase of concent ration of water. The minimum grain size and uniform dispersion can beachieved when the concent ration of water is 0. 50 %. Based on the reduction mechanism of Ag + and essential principle of the adsorption process on the surface of SiO2 , it can be concluded that the water-rich adsorption layer on thesurface of SiO2 is formed gradually with the increase of water concent ration and the region of Ag generation changesfrom the surface of SiO2 to the water-rich adsorption layer , where the concent ration of NaOH is so high that most ofAg are generated in it .
Ag nanoparticles were synthesized in a nanoreactor formed by an adsorption layer on the silica surface.The effect s of concent ration of water on the process of adsorption and reaction were analyzed. When the mass fraction of NaOH keeps constant , the equilibrium content of NaOH adsorbed on SiO2 increases with the increase of concent ration of water , which changes f rom 0 to 1. 00 %. Two jump regions of equilibrium content are found f rom 0 to0. 05 % and f rom 0. 25 % to 0. 50 %. Analysis by XRD and TEM indicates that the agglomeration of Ag or Ag2Oparticles becomes more moderate , it s dispersion on the surface SiO2 becomes more uniform , and it s grain size becomes smaller with the increase of concent ration of water. The minimum grain size and uniform dispersion can beachieved when the concent ration of water is 0. 50 %. Based on the reduction mechanism of Ag + and essential principle of the adsorption process on the surface of SiO2 , it can be concluded that the water-rich adsorption layer on thesurface of SiO2 is formed gradually with the increase of water concent ration and the region of Ag generation changesfrom the surface of SiO2 to the water-rich adsorption layer , where the concent ration of NaOH is so high that most ofAg are generated in it .
2006, 23(4): 95-99.
Abstract:
Portland cement and carbon fiber were used to fabricate carbon fiber reinforced cement-based composites(CFRC) by compressing. The microcosmic properties were analyzed by SEM and Poremaster Analyzer , and thesmart properties were also studied. The result s show that the porosities of the specimens formed under larger pressures are obviously lower than those of the specimens formed under smaller pressures. With the temperatureincreasing , the resistivities of the composites formed under different pressures show the t rend of increase anddecrease. The critical temperature zones of the specimens formed under the smaller and the larger pressures arebetween 75～100 ℃and 100～120 ℃, respectively. Under the low cyclic load , the f ractional change in resistivity ofCFRC changes reversibly with the cyclic load. The amplitude of the f ractional change in resistance of the compositesformed under the larger pressure is obviously larger than that of the composites formed under the smaller pressure ,which is more suitable for the real-time , dynamic and health monitoring and damage assessment of st ructures.
Portland cement and carbon fiber were used to fabricate carbon fiber reinforced cement-based composites(CFRC) by compressing. The microcosmic properties were analyzed by SEM and Poremaster Analyzer , and thesmart properties were also studied. The result s show that the porosities of the specimens formed under larger pressures are obviously lower than those of the specimens formed under smaller pressures. With the temperatureincreasing , the resistivities of the composites formed under different pressures show the t rend of increase anddecrease. The critical temperature zones of the specimens formed under the smaller and the larger pressures arebetween 75～100 ℃and 100～120 ℃, respectively. Under the low cyclic load , the f ractional change in resistivity ofCFRC changes reversibly with the cyclic load. The amplitude of the f ractional change in resistance of the compositesformed under the larger pressure is obviously larger than that of the composites formed under the smaller pressure ,which is more suitable for the real-time , dynamic and health monitoring and damage assessment of st ructures.
2006, 23(4): 100-105.
Abstract:
Based on the reactive fame spray technique , TiC- TiB2 multiphase coatings were prepared on the steelsubst rate with Ti-B4C-C reactant s. By elect ronic microcosmic observation , X-ray diff raction and energy spect rumanalysis , the st ructure and it s forming causes of TiC- TiB2 multiphase coatings were discussed. The result s showthat the coatings have the multiphase heterogeneous metastable st ructure , which have no conspicuous layer-shapedst ructure that the t raditional flame spray coatings have. The coatings are composed of the major phases TiC0.7N0.3 ,TiC0.2N0.8 , TiB2 , a little of TiO2 , Ti2O , Ti3O5 and some pores. There are three kinds of st ructures with differentcharacteristics in the coatings the cluster-shaped st ructure in micron-nanometer size , the 1～3μm st ructure takingon equiaxed particles dist ribution , and the deep black pores. Before meeting the subst rate the spray particles combust , react , and form molten ceramic beads (in solid and hollow two kinds) or abnormal ceramic granules (having thesame figure as the spray particles) . Af ter colliding with the subst rate , they distort , cool , quickly crystallize andform the three kinds of st ructures.
Based on the reactive fame spray technique , TiC- TiB2 multiphase coatings were prepared on the steelsubst rate with Ti-B4C-C reactant s. By elect ronic microcosmic observation , X-ray diff raction and energy spect rumanalysis , the st ructure and it s forming causes of TiC- TiB2 multiphase coatings were discussed. The result s showthat the coatings have the multiphase heterogeneous metastable st ructure , which have no conspicuous layer-shapedst ructure that the t raditional flame spray coatings have. The coatings are composed of the major phases TiC0.7N0.3 ,TiC0.2N0.8 , TiB2 , a little of TiO2 , Ti2O , Ti3O5 and some pores. There are three kinds of st ructures with differentcharacteristics in the coatings the cluster-shaped st ructure in micron-nanometer size , the 1～3μm st ructure takingon equiaxed particles dist ribution , and the deep black pores. Before meeting the subst rate the spray particles combust , react , and form molten ceramic beads (in solid and hollow two kinds) or abnormal ceramic granules (having thesame figure as the spray particles) . Af ter colliding with the subst rate , they distort , cool , quickly crystallize andform the three kinds of st ructures.
2006, 23(4): 106-111.
Abstract:
A reversibly thermochromic functional cement based composite at normal temperature was prepared byadding reversibly thermochromic microencapsules in white Portland cement . The research result s show that thecolors of the composites can be changed reversibly f rom blue , green , red at lower temperature to white at highertemperature , and the switching temperature is about 42～58 ℃. Mean square analyses show that when the blue thermochromic microencapsule , B30 , is added in white Portland cement , the fineness and st rength of the composite canbe affected greatly. The water demand for the standard consistency of cement slurry increases by about 13 % , andthe flexural st rength and compressive st rength decrease by 20 %～40 % , but the setting time and the soundness ofcement are not affected. The composite has the light-absorbing and light-reflecting t ransforming function for buildings , indicating that the prepared composite can meet the demand for creation of a thermally comfortable environment of buildings.
A reversibly thermochromic functional cement based composite at normal temperature was prepared byadding reversibly thermochromic microencapsules in white Portland cement . The research result s show that thecolors of the composites can be changed reversibly f rom blue , green , red at lower temperature to white at highertemperature , and the switching temperature is about 42～58 ℃. Mean square analyses show that when the blue thermochromic microencapsule , B30 , is added in white Portland cement , the fineness and st rength of the composite canbe affected greatly. The water demand for the standard consistency of cement slurry increases by about 13 % , andthe flexural st rength and compressive st rength decrease by 20 %～40 % , but the setting time and the soundness ofcement are not affected. The composite has the light-absorbing and light-reflecting t ransforming function for buildings , indicating that the prepared composite can meet the demand for creation of a thermally comfortable environment of buildings.
2006, 23(4): 112-118.
Abstract:
A unit cell model is established on the pattern of the rule of the yarn movement and the relationshipbetween the braiding parameters is deduced. Based on this model , the elastic properties of three-dimensional six-directional (3D & 6D) braided composites were derived with the method of stiffness averaging and the influence of thebraiding angle adn the fiber volume f raction was analyzed. The result s show that the 3D & 6D braided composite hasgood mechanical properties and it s in2plane mechanical performance is improved by joining the in2plane t ransverseyarns.
A unit cell model is established on the pattern of the rule of the yarn movement and the relationshipbetween the braiding parameters is deduced. Based on this model , the elastic properties of three-dimensional six-directional (3D & 6D) braided composites were derived with the method of stiffness averaging and the influence of thebraiding angle adn the fiber volume f raction was analyzed. The result s show that the 3D & 6D braided composite hasgood mechanical properties and it s in2plane mechanical performance is improved by joining the in2plane t ransverseyarns.
2006, 23(4): 119-123.
Abstract:
A model is established based on the basic mechanics characters of composite materials and the basic mechanics theory of the multi - spar st ructures , combining the request from engineering practices. The equations ofloading capability are deduced , especially in post-buckling of the multi-spar st ructures , and the analyzing sof twareis designed. The validity and effectiveness of the sof tware are demonst rated by comparing the application with experiment . The sof tware with high accuracy and short-time-consumption can solve the analytical problem of composite multi-spar load capability faced in the aircraf t design.
A model is established based on the basic mechanics characters of composite materials and the basic mechanics theory of the multi - spar st ructures , combining the request from engineering practices. The equations ofloading capability are deduced , especially in post-buckling of the multi-spar st ructures , and the analyzing sof twareis designed. The validity and effectiveness of the sof tware are demonst rated by comparing the application with experiment . The sof tware with high accuracy and short-time-consumption can solve the analytical problem of composite multi-spar load capability faced in the aircraf t design.
2006, 23(4): 124-128.
Abstract:
For reliability design and safety evaluation on fiber wound reinforced plastics ( FWRP) pressure vessels ,the t raditional safety factor design was substituted by a reliability st ructure design based on the reliability theory andthe statistical principle. Eight glass fiber wound reinforced plastics ( GFWRP) pressure vessels were manufacturedand the experiment s were conducted to obtain the probabilistic dist ribution of design variables , such as the fiberst rength , winding angle , geomet ric size , burst st rength and so on. The result s ( thickness of the winding fiber)derived f rom the reliability design agree well with the experimental result s and much lower than that f rom thet raditional safety factor design. Through comparison between the reliability design result s with different statistics offiber st rength , the significant influence of the variance level of fiber st rength on reliability design of FWRP pressurevessel was demonst rated. The t raditional safety factor design was verified to be not reasonable since it considers onlythe mean value of fiber st rength without the effect of fiber st rength statistics on the st ructural resistance of thevessel . The reliability design of FWRP pressure vessel in this study present s the effective unity of safety andeconomy.
For reliability design and safety evaluation on fiber wound reinforced plastics ( FWRP) pressure vessels ,the t raditional safety factor design was substituted by a reliability st ructure design based on the reliability theory andthe statistical principle. Eight glass fiber wound reinforced plastics ( GFWRP) pressure vessels were manufacturedand the experiment s were conducted to obtain the probabilistic dist ribution of design variables , such as the fiberst rength , winding angle , geomet ric size , burst st rength and so on. The result s ( thickness of the winding fiber)derived f rom the reliability design agree well with the experimental result s and much lower than that f rom thet raditional safety factor design. Through comparison between the reliability design result s with different statistics offiber st rength , the significant influence of the variance level of fiber st rength on reliability design of FWRP pressurevessel was demonst rated. The t raditional safety factor design was verified to be not reasonable since it considers onlythe mean value of fiber st rength without the effect of fiber st rength statistics on the st ructural resistance of thevessel . The reliability design of FWRP pressure vessel in this study present s the effective unity of safety andeconomy.
2006, 23(4): 129-135.
Abstract:
Based on the similarity between the orientation of the fiber in the stitched laminates and the st ream inthe flow around a cylinder , a flow field model is built for the elastic constant s of the stitched laminar , which is asteady 2D non-compressible non-viscous ideal flow without swirl in a finite space. The boundaries of the flow fieldand the unit cell of the stitched laminates are identical , and the surface of the body in the flow field is the same as thesection shape of the stitch thread. The velocity variation in the flow field describes the fiber volume f raction variationin the unit cell of the stitched laminar , and the st reamline shape describes the fiber orientation. Using the flow fieldmodel , the elastic properties of the stitched laminar are calculated by the micromechanics and the homogenizationmethod , and the result s are in good agreement with those of the test . Finally , the effect s of the stitch parameters onthe laminar elastic constant s are discussed.
Based on the similarity between the orientation of the fiber in the stitched laminates and the st ream inthe flow around a cylinder , a flow field model is built for the elastic constant s of the stitched laminar , which is asteady 2D non-compressible non-viscous ideal flow without swirl in a finite space. The boundaries of the flow fieldand the unit cell of the stitched laminates are identical , and the surface of the body in the flow field is the same as thesection shape of the stitch thread. The velocity variation in the flow field describes the fiber volume f raction variationin the unit cell of the stitched laminar , and the st reamline shape describes the fiber orientation. Using the flow fieldmodel , the elastic properties of the stitched laminar are calculated by the micromechanics and the homogenizationmethod , and the result s are in good agreement with those of the test . Finally , the effect s of the stitch parameters onthe laminar elastic constant s are discussed.
2006, 23(4): 136-142.
Abstract:
Based on the idea of calculating elastic properties of the stitched laminar , a flow field model is set up tocalculate the elastic properties of each laminar for the elastic properties of stitched laminates. Using the flow fieldmodels , the elastic properties of the 0°and 45°stitched laminar are calculated by the micromechanics and the homogenization method. The elastic constant s of 6 set s of stitched laminates are calculated using the modified homogenization method , and the result s are in good agreement with those of the test .
Based on the idea of calculating elastic properties of the stitched laminar , a flow field model is set up tocalculate the elastic properties of each laminar for the elastic properties of stitched laminates. Using the flow fieldmodels , the elastic properties of the 0°and 45°stitched laminar are calculated by the micromechanics and the homogenization method. The elastic constant s of 6 set s of stitched laminates are calculated using the modified homogenization method , and the result s are in good agreement with those of the test .
2006, 23(4): 143-148.
Abstract:
The aeroelasticity of helicopter composite rotor blades with elastic coupling is analyzed. The st ructuralmodel in this analysis includes the effect s of t ransverse shear deformation , out-of-plane warping and aeroelastic coupling. A 21-DOF beam finite element , including t ransverse shear DOF and warping DOF , is developed for analysis.The governing differential equations of motion for a hingeless rotor are derived using the Hamiltonps principle.Three different composite blade configurations are conducted for comparison. The result s show that changes in bladef requencies are very small , however , the mode shapes are significantly changed considering elastic coupling. Theblade stability in hover is st rongly affected by the ply-induced composite couplings. Positive flap -torsion couplinghas a stabilizing effect on the lag mode damping. Negative flap-torsion coupling has a destabilizing effect on the lagstability.
The aeroelasticity of helicopter composite rotor blades with elastic coupling is analyzed. The st ructuralmodel in this analysis includes the effect s of t ransverse shear deformation , out-of-plane warping and aeroelastic coupling. A 21-DOF beam finite element , including t ransverse shear DOF and warping DOF , is developed for analysis.The governing differential equations of motion for a hingeless rotor are derived using the Hamiltonps principle.Three different composite blade configurations are conducted for comparison. The result s show that changes in bladef requencies are very small , however , the mode shapes are significantly changed considering elastic coupling. Theblade stability in hover is st rongly affected by the ply-induced composite couplings. Positive flap -torsion couplinghas a stabilizing effect on the lag mode damping. Negative flap-torsion coupling has a destabilizing effect on the lagstability.
2006, 23(4): 149-154.
Abstract:
This article discusses the pull-out mechanical model of NiTi shape memory alloy (SMA) fiber. In constant temperature state , considering the interfacial f riction between the fiber and mat rix , the tensile problem of SMAfiber under varying axial force is discussed , and the formulation of memory alloy fiberps pull-out length is obtainedby two theories respectively , namely the index model of Tanaka and the cosine model of C. Liang. The numericalresults are given. The good agreement between the results of index model and cosine model warrants this new theoretical method.
This article discusses the pull-out mechanical model of NiTi shape memory alloy (SMA) fiber. In constant temperature state , considering the interfacial f riction between the fiber and mat rix , the tensile problem of SMAfiber under varying axial force is discussed , and the formulation of memory alloy fiberps pull-out length is obtainedby two theories respectively , namely the index model of Tanaka and the cosine model of C. Liang. The numericalresults are given. The good agreement between the results of index model and cosine model warrants this new theoretical method.
2006, 23(4): 155-163.
Abstract:
This paper employs some related theorems as well as the result s f rom the field of geomet rical probabilityto explore the quantitative relationship between statistical mean values of the apparent interfacial t ransition zone( ITZ) thickness and the actual ITZ thickness. In the 2 dimensional case as well as in the 3 dimensional case , thegeneral solutions are derived for an arbit rary shape grain with closed convex curve (2D) or convex surface (3D) .The result s show that : (1) For the 2D grains with the closed convex curve of an arbit rary shape , the ratio of thestatistical mean apparent ITZ thickness to the actual ITZ thickness is less thanπ/ 2. The exact value depends on theshape of the grains. If the actual ITZ thickness is far less than the size of the grain , this ratio is approximately equaltoπ/ 2. (2) For the 3D grains with the closed convex surface of an arbit rary shape , the ratio of the statistical meanapparent ITZ thickness to the actual ITZ thickness is less than 2. The exact value also depends on the shape of thegrains. If the actual ITZ thickness is far less than the size of the grain , the ratio of the statistical mean value of theapparent ITZ thickness to the actual ITZ thickness is approximately equal to 2.
This paper employs some related theorems as well as the result s f rom the field of geomet rical probabilityto explore the quantitative relationship between statistical mean values of the apparent interfacial t ransition zone( ITZ) thickness and the actual ITZ thickness. In the 2 dimensional case as well as in the 3 dimensional case , thegeneral solutions are derived for an arbit rary shape grain with closed convex curve (2D) or convex surface (3D) .The result s show that : (1) For the 2D grains with the closed convex curve of an arbit rary shape , the ratio of thestatistical mean apparent ITZ thickness to the actual ITZ thickness is less thanπ/ 2. The exact value depends on theshape of the grains. If the actual ITZ thickness is far less than the size of the grain , this ratio is approximately equaltoπ/ 2. (2) For the 3D grains with the closed convex surface of an arbit rary shape , the ratio of the statistical meanapparent ITZ thickness to the actual ITZ thickness is less than 2. The exact value also depends on the shape of thegrains. If the actual ITZ thickness is far less than the size of the grain , the ratio of the statistical mean value of theapparent ITZ thickness to the actual ITZ thickness is approximately equal to 2.
2006, 23(4): 164-168.
Abstract:
The cured shapes of cross-ply unsymmet ric composite laminates were investigated using Ritz method.An analytical model to predict the cured shape of unsymmet ric thin composite laminates was established based on thegeomet ric nonlinearity. The shape and deformation of the unsymmet ric composite laminates were obtained. It showsthat the predicted deformations are well agreed with the experiment s for the regions a lit tle far away from the edgesof the square plates and for the rectangular plates.
The cured shapes of cross-ply unsymmet ric composite laminates were investigated using Ritz method.An analytical model to predict the cured shape of unsymmet ric thin composite laminates was established based on thegeomet ric nonlinearity. The shape and deformation of the unsymmet ric composite laminates were obtained. It showsthat the predicted deformations are well agreed with the experiment s for the regions a lit tle far away from the edgesof the square plates and for the rectangular plates.
2006, 23(4): 169-174.
Abstract:
The effect of stitching reinforcement on st rain concent ration was investigated for the composite laminatescontaining a circular hole. The effect s of stitching parameters , such as stitching needle distance , row spacing , edgedistance , single stitching or double stitching , etc , were compared and analysed. The tensile st rength and stiffnesswere measured for composite laminates containing a circular hole. The st rain concent ration and st rain dist ributionregularity were investigated analytically and experimentally. The hole edge coefficient s of st rain concent ration weremeasured for different stitching parameters , external load , the edge location of the hole , etc. The experimental results show a distinct efficiency of stitching reinforcement for composite laminates containing a circular hole and givethe stitching design parameters on the hole edge. The experiment s show that near the hole region in the loading direction , the st rain concent ration is not influenced under different loads ; with the material bearing compressive deformation , near the hole region in the vertical line of loading direction , the st rain concent ration factors Kε vary withload and can reach a very high value. Compared with isot ropic plates , the Kεof orthot ropic laminates is variable atdifferent edge locations of the hole.
The effect of stitching reinforcement on st rain concent ration was investigated for the composite laminatescontaining a circular hole. The effect s of stitching parameters , such as stitching needle distance , row spacing , edgedistance , single stitching or double stitching , etc , were compared and analysed. The tensile st rength and stiffnesswere measured for composite laminates containing a circular hole. The st rain concent ration and st rain dist ributionregularity were investigated analytically and experimentally. The hole edge coefficient s of st rain concent ration weremeasured for different stitching parameters , external load , the edge location of the hole , etc. The experimental results show a distinct efficiency of stitching reinforcement for composite laminates containing a circular hole and givethe stitching design parameters on the hole edge. The experiment s show that near the hole region in the loading direction , the st rain concent ration is not influenced under different loads ; with the material bearing compressive deformation , near the hole region in the vertical line of loading direction , the st rain concent ration factors Kε vary withload and can reach a very high value. Compared with isot ropic plates , the Kεof orthot ropic laminates is variable atdifferent edge locations of the hole.
2006, 23(4): 175-179.
Abstract:
A finite element model is developed to analyze the stability of composite shells of revolution with thet ransverse shear effect . Transverse shear st rain is int roduced into the st rain vector to take t ransverse shear deformation into account . To avoid shear lock , the one point Gauss integral method is used to compute the stiffness. Thegeomet ry stiffness is deduced by St ricklin method. The stability problem is generalized to an eigenvalue problem atlast . The examples show that the critical load of isot ropic or composite shells of revolution will decrease when considering the t ransverse shear deformation. The influence of t ransverse shear is small on isot ropic thin shells , but alittle big on composite shells. The influence of t ransverse shear on isot ropic thin shells is smaller than on compositeshells.
A finite element model is developed to analyze the stability of composite shells of revolution with thet ransverse shear effect . Transverse shear st rain is int roduced into the st rain vector to take t ransverse shear deformation into account . To avoid shear lock , the one point Gauss integral method is used to compute the stiffness. Thegeomet ry stiffness is deduced by St ricklin method. The stability problem is generalized to an eigenvalue problem atlast . The examples show that the critical load of isot ropic or composite shells of revolution will decrease when considering the t ransverse shear deformation. The influence of t ransverse shear is small on isot ropic thin shells , but alittle big on composite shells. The influence of t ransverse shear on isot ropic thin shells is smaller than on compositeshells.
2006, 23(4): 180-184.
Abstract:
The bonded NdFeB magnet was prepared with NdFeB magnetic powders and polyimide. The effect s ofparticle size of magnetic powders , coupling agent content , adhesive content , molding pressure and adhesive propertyon the magnetic and mechanical properties of bonded magnet s were studied. The results indicate that the bondedNdFeB magnets with good properties can be obtained by a proper ratio of big particles to small particles , appropriateamount of coupling agent and adhesive , proper pressure and polyimide. The ratio of the coarse particles to the fineones was 33 to 67. The content s of coupling agent and adhesive were 0. 9 % and 3. 2 % , respectively. The properpressure was 600 MPa.
The bonded NdFeB magnet was prepared with NdFeB magnetic powders and polyimide. The effect s ofparticle size of magnetic powders , coupling agent content , adhesive content , molding pressure and adhesive propertyon the magnetic and mechanical properties of bonded magnet s were studied. The results indicate that the bondedNdFeB magnets with good properties can be obtained by a proper ratio of big particles to small particles , appropriateamount of coupling agent and adhesive , proper pressure and polyimide. The ratio of the coarse particles to the fineones was 33 to 67. The content s of coupling agent and adhesive were 0. 9 % and 3. 2 % , respectively. The properpressure was 600 MPa.
