1999 Vol. 16, No. 2
1999, 16(2): 1-5.
Abstract:
A costeffective approach is supposed to insitu monitor the cure of epoxy resin with common low refractive index fiberoptic sensor. A fiberoptic refractive index sensor was made by removing a short region of the cladding of a low refractive step index optical fiber. The sensor was used to insitu monitor the cure of epoxy resin by measuring the refractive index change of the resin during the cure process. The model of the sensor was developed on the basis of wave guide theory. A probe configuration was made by depositing a high reflective film on the endface of the fiber and mostly facilitate the tooling. Experiments have been performed to test the correctness of the model and the feasibility of the supposed approach.
A costeffective approach is supposed to insitu monitor the cure of epoxy resin with common low refractive index fiberoptic sensor. A fiberoptic refractive index sensor was made by removing a short region of the cladding of a low refractive step index optical fiber. The sensor was used to insitu monitor the cure of epoxy resin by measuring the refractive index change of the resin during the cure process. The model of the sensor was developed on the basis of wave guide theory. A probe configuration was made by depositing a high reflective film on the endface of the fiber and mostly facilitate the tooling. Experiments have been performed to test the correctness of the model and the feasibility of the supposed approach.
1999, 16(2): 6-10.
Abstract:
Conductive polymeric composites were prepared from Carbon Black(CB),Nitrile Butadiene Rubber(NBR) and a kind of organic crystal. The relationship between the resistivity of NBR/CB(N550) composite and temperature exhibits PTC (Positive Temperature Coefficient) phenomenon to some extent. Some influences of organic crystal on the resistivity of composites at room temperature and PTC effect of the composites were investigated in detail.
Conductive polymeric composites were prepared from Carbon Black(CB),Nitrile Butadiene Rubber(NBR) and a kind of organic crystal. The relationship between the resistivity of NBR/CB(N550) composite and temperature exhibits PTC (Positive Temperature Coefficient) phenomenon to some extent. Some influences of organic crystal on the resistivity of composites at room temperature and PTC effect of the composites were investigated in detail.
1999, 16(2): 11-14.
Abstract:
The properties of a new magnetic composite which consists of rapid quenching NdFeB magnetic powder and magnetic polymer (OPM) were studied and contrasted with the one of the bonded NdFeB permanent magnet by nonmagnetic polymer, such as epoxy resin. The results show that when the percentage of NdFeB magnetic powder of the magnetic composite increases, the residual flux density Br, the maximum energy product (BH)m and the coercive force Hbc increase, but the intrinsic coercive force Hjc decreases a little. However, when the rapid quenching NdFeB powder in the OPM bonded NdFeB magnet is as much as the one in epoxy resin bonded NeFeB magnet, the magnetic properties Br, (BH)m and Hbc of the former are higher than those of the latter, and the stability of temperature of the former is the same as the latter.
The properties of a new magnetic composite which consists of rapid quenching NdFeB magnetic powder and magnetic polymer (OPM) were studied and contrasted with the one of the bonded NdFeB permanent magnet by nonmagnetic polymer, such as epoxy resin. The results show that when the percentage of NdFeB magnetic powder of the magnetic composite increases, the residual flux density Br, the maximum energy product (BH)m and the coercive force Hbc increase, but the intrinsic coercive force Hjc decreases a little. However, when the rapid quenching NdFeB powder in the OPM bonded NdFeB magnet is as much as the one in epoxy resin bonded NeFeB magnet, the magnetic properties Br, (BH)m and Hbc of the former are higher than those of the latter, and the stability of temperature of the former is the same as the latter.
1999, 16(2): 15-20.
Abstract:
The energyabsorption properties of the 5 glassepoxy cylindrical shells subjected to axial compression were studied in this paper. Tests were performed to study the effect of the winding angle of the fibers on energyabsorption properties. The crushing process, failure modes and energyabsorption capability of various cylindrical composite shells under various loading conditions were analyzed.
The energyabsorption properties of the 5 glassepoxy cylindrical shells subjected to axial compression were studied in this paper. Tests were performed to study the effect of the winding angle of the fibers on energyabsorption properties. The crushing process, failure modes and energyabsorption capability of various cylindrical composite shells under various loading conditions were analyzed.
1999, 16(2): 21-28.
Abstract:
APC-2/AS4 prepreg tape winding with a heated mandrel and a flame was investigated. The temperaturetime processes of these two winding methods and the influence of winding parameters on qualities and internal stresses were also analyzed. The results show that the thickness of a part wound with a heated mandrel is limited by the highest temperature of mandrel and the thickness of that wound with a flame is unlimited. Tension and the matrix content of a tape are the most important parameters for a good quality part wound with a heated mandrel.
APC-2/AS4 prepreg tape winding with a heated mandrel and a flame was investigated. The temperaturetime processes of these two winding methods and the influence of winding parameters on qualities and internal stresses were also analyzed. The results show that the thickness of a part wound with a heated mandrel is limited by the highest temperature of mandrel and the thickness of that wound with a flame is unlimited. Tension and the matrix content of a tape are the most important parameters for a good quality part wound with a heated mandrel.
1999, 16(2): 29-33.
Abstract:
The wettability and soil adhesion performance of glass bead reinforced UHMWPE matrix composite were investigated. The results show that the increase of filler volume leads to the increase of the soiladhesion and wettability. When the filler volume is less than 9%, it will not affect the soil adhesionreducing performance obviously. The interaction of soilwaterspecimen surface was also analyzed. It is concluded that the reduction of soil adhesion of the glass bead/UHMWPE composite is caused mainly by its hydrophobic and chemical nonsmooth effects.
The wettability and soil adhesion performance of glass bead reinforced UHMWPE matrix composite were investigated. The results show that the increase of filler volume leads to the increase of the soiladhesion and wettability. When the filler volume is less than 9%, it will not affect the soil adhesionreducing performance obviously. The interaction of soilwaterspecimen surface was also analyzed. It is concluded that the reduction of soil adhesion of the glass bead/UHMWPE composite is caused mainly by its hydrophobic and chemical nonsmooth effects.
1999, 16(2): 34-38.
Abstract:
The curing reaction of modified BMI CDR9418 was studied with DSC. The curing reaction was carried out by constant heating and isothermal methods. And two curing exothermic peaks were found. Gelling temperature, curing temperature and treating temperature were calculated by extrapolating T.
The curing reaction of modified BMI CDR9418 was studied with DSC. The curing reaction was carried out by constant heating and isothermal methods. And two curing exothermic peaks were found. Gelling temperature, curing temperature and treating temperature were calculated by extrapolating T.
1999, 16(2): 39-45.
Abstract:
Some new results of the static and dynamic compressive tests about two reinforced foam plastics are given in this paper. Their deformation and failure characteristics were investigated by these experiments. By means of SEM analyses for two reinforced foam plastics specimens after loading, the deformation and failure mechanisms of them are determined. Furthermore, the reinforced mechanisms of them are also discussed from the viewpoint of microscopy.
Some new results of the static and dynamic compressive tests about two reinforced foam plastics are given in this paper. Their deformation and failure characteristics were investigated by these experiments. By means of SEM analyses for two reinforced foam plastics specimens after loading, the deformation and failure mechanisms of them are determined. Furthermore, the reinforced mechanisms of them are also discussed from the viewpoint of microscopy.
1999, 16(2): 46-51.
Abstract:
The piezoresistivity of high density polyethylene/graphite (HDPE/GP) semiconductive composites was studied through measuring the resistance change under uniaxial pressure. The results show that there exists a marking pressure dependence of the conductivity in HDPE/GP composites, in which the socalled negative pressure coefficient of resistive ( NPCR )and positive pressure coefficient of resistive ( PPCR ) are observed under minute and moderate pressures. Under constant pressures, timedependent resistivity is an outstanding characteristic for the composites, which is defined as resistance creep. The breakdown and rebuildup process of conductive network under pressure may be responsible for the pressureand timedependence of resistivity.
The piezoresistivity of high density polyethylene/graphite (HDPE/GP) semiconductive composites was studied through measuring the resistance change under uniaxial pressure. The results show that there exists a marking pressure dependence of the conductivity in HDPE/GP composites, in which the socalled negative pressure coefficient of resistive ( NPCR )and positive pressure coefficient of resistive ( PPCR ) are observed under minute and moderate pressures. Under constant pressures, timedependent resistivity is an outstanding characteristic for the composites, which is defined as resistance creep. The breakdown and rebuildup process of conductive network under pressure may be responsible for the pressureand timedependence of resistivity.
1999, 16(2): 52-56.
Abstract:
In this paper, using the analytical conclusion of Fick rule, the absorbing moisture process of abrasion adhesion coating material is measured. Furthermore, the dynamic absorbing moisture consistency and stress of applied coating are analyzed. The results show that the absorbing moisture property of coating is affected by the filling quantity and curing dose; the maximum absorbing moisture consistency is about 4%; relative to the initial strength, the dynamic absorbing moisture stress of coating is a small quantity.
In this paper, using the analytical conclusion of Fick rule, the absorbing moisture process of abrasion adhesion coating material is measured. Furthermore, the dynamic absorbing moisture consistency and stress of applied coating are analyzed. The results show that the absorbing moisture property of coating is affected by the filling quantity and curing dose; the maximum absorbing moisture consistency is about 4%; relative to the initial strength, the dynamic absorbing moisture stress of coating is a small quantity.
1999, 16(2): 57-61.
Abstract:
This paper presents a statistical evaluation of the tensile strength of the mullite shortfibrereinforced aluminium composite, which was produced by squeeze casting, by means of Weibull statistics. The result shows that the material has a high and reliable tensile strength. Volume fractions (Vf) of fibres in the material and on the fracture have been statistically analyzed. The spread of fibres shows a heterogeneity in microstructure. Two kinds of fibres, one making a small angle with the normal of the observed surface or with the tensile direction and another making a big angle with that, have hardly equal Vf. The latter has a larger Vf than the former, and the larger the Vf on the fracture, the less the tensile strength. The reason that the composite fails is the debonding of interface between the largeanglefibre and the matrix. The reason that the strength distributes in a certain range is the heterogeneity of the largeanglefibres.
This paper presents a statistical evaluation of the tensile strength of the mullite shortfibrereinforced aluminium composite, which was produced by squeeze casting, by means of Weibull statistics. The result shows that the material has a high and reliable tensile strength. Volume fractions (Vf) of fibres in the material and on the fracture have been statistically analyzed. The spread of fibres shows a heterogeneity in microstructure. Two kinds of fibres, one making a small angle with the normal of the observed surface or with the tensile direction and another making a big angle with that, have hardly equal Vf. The latter has a larger Vf than the former, and the larger the Vf on the fracture, the less the tensile strength. The reason that the composite fails is the debonding of interface between the largeanglefibre and the matrix. The reason that the strength distributes in a certain range is the heterogeneity of the largeanglefibres.
EFFECTS OF CATEGORY AND CONTENT OF REINFORCEMENTS ONMECHANICAL PROPERTIES OF METAL MATRIX COMPOSITES
1999, 16(2): 62-66.
Abstract:
Some aluminum matrix composites, reinforced by alumina and silicon carbide particles, were fabricated by P/M method, and the normal mechanical properties were measured. It is shown that the elastic modulus increases with volume fraction of ceramic particles, though the fracture strain decreases. SiCP/2024 system has the highest strength and best reinforcing efficiency, with the increase of particle volume fraction to 25%. SiCP/7075 system has lower strength than that of the controlled alloy. SiCP/pureAl system shows higher reinforcing efficiency in spite of the lower absolute strength. Al2O3P/2024 system exhibits a character of first rise and then drop in strength. It is considered that these differences may depend on the strength levels of reinforcements and the matrices and the deforming characteristics. The better matrices should have higher strength as well as higher workhardening rate.
Some aluminum matrix composites, reinforced by alumina and silicon carbide particles, were fabricated by P/M method, and the normal mechanical properties were measured. It is shown that the elastic modulus increases with volume fraction of ceramic particles, though the fracture strain decreases. SiCP/2024 system has the highest strength and best reinforcing efficiency, with the increase of particle volume fraction to 25%. SiCP/7075 system has lower strength than that of the controlled alloy. SiCP/pureAl system shows higher reinforcing efficiency in spite of the lower absolute strength. Al2O3P/2024 system exhibits a character of first rise and then drop in strength. It is considered that these differences may depend on the strength levels of reinforcements and the matrices and the deforming characteristics. The better matrices should have higher strength as well as higher workhardening rate.
1999, 16(2): 67-72.
Abstract:
In this work, the microstructures of hotextruded tubes and cuplike parts were observed by SEM and TEM. The Vickershardness and tensile properties were investigated. The results indicate that SiC whiskers tend to break and distribute directionally. The extrusion temperature is an important factor in final microstructure and properties of extruded parts. It is also shown that the unevenly distributed hardness is caused by the uneven flow of metals. An aging treatment of extruded parts will greatly increase the tensile strength.
In this work, the microstructures of hotextruded tubes and cuplike parts were observed by SEM and TEM. The Vickershardness and tensile properties were investigated. The results indicate that SiC whiskers tend to break and distribute directionally. The extrusion temperature is an important factor in final microstructure and properties of extruded parts. It is also shown that the unevenly distributed hardness is caused by the uneven flow of metals. An aging treatment of extruded parts will greatly increase the tensile strength.
1999, 16(2): 73-76.
Abstract:
Aluminosilicate(Al2O3·SiO2) short fibre reinforced AlSi alloy composite was fabricated by means of squeeze casting and the interface between aluminosilicate fibre and AlSi alloy matrix was studied by TEM. The experimental results show that the reaction products between aluminosilicate fibre and magnesium in AlSi alloy and binder in preform are MgAl2O4(spinel) and Si3(PO4)4.
Aluminosilicate(Al2O3·SiO2) short fibre reinforced AlSi alloy composite was fabricated by means of squeeze casting and the interface between aluminosilicate fibre and AlSi alloy matrix was studied by TEM. The experimental results show that the reaction products between aluminosilicate fibre and magnesium in AlSi alloy and binder in preform are MgAl2O4(spinel) and Si3(PO4)4.
1999, 16(2): 77-81.
Abstract:
Alsalt composite was fabricated with pressure penetrating casting. Fabricating process of preform and the influence of process parameters on preform were studied. When binder content is about 10% and baking temperature is 720 and baking time is 5.4 ks, a preform with higher compressive strength can be obtained. With the help of SEM, the structure of the preform was observed before and after baking. By removing salt from the composite, porous Al can be obtained. Thermal expansion property also was studied. Comparison with compact aluminum, porous aluminum has a lower average linear expansion coefficient.
Alsalt composite was fabricated with pressure penetrating casting. Fabricating process of preform and the influence of process parameters on preform were studied. When binder content is about 10% and baking temperature is 720 and baking time is 5.4 ks, a preform with higher compressive strength can be obtained. With the help of SEM, the structure of the preform was observed before and after baking. By removing salt from the composite, porous Al can be obtained. Thermal expansion property also was studied. Comparison with compact aluminum, porous aluminum has a lower average linear expansion coefficient.
1999, 16(2): 82-87.
Abstract:
Based on the energy equivalence principle, the elastic modulus of Al2O3f/Al composite was predicted by means of the Finite Element Method. In the predicting, the random orientation distribution of short fiber was considered. The results were compared with the experimental values and those of previous predicting methods. In the end, it can be concluded that the method developed in this paper is reasonable and precise.
Based on the energy equivalence principle, the elastic modulus of Al2O3f/Al composite was predicted by means of the Finite Element Method. In the predicting, the random orientation distribution of short fiber was considered. The results were compared with the experimental values and those of previous predicting methods. In the end, it can be concluded that the method developed in this paper is reasonable and precise.
1999, 16(2): 88-93.
Abstract:
Generalized selfconsistent finite element iterative averaging method was united with the Gurson model for the parametric investigation of the damage mechanisms and their relations with the macroscopic tensile properties of the SiC reinforced Al5456. The mesoscopic damage mechanisms studied here contained two types: interphase debonding between the reinforcement and matrix and the nucleation, growth, and coalescence of the voids in the matrix. As shown by the results, the interphase debonding increases the composite ductility, but results in the strengthening effects of the brittle reinforcements decreasing unfavorably.
Generalized selfconsistent finite element iterative averaging method was united with the Gurson model for the parametric investigation of the damage mechanisms and their relations with the macroscopic tensile properties of the SiC reinforced Al5456. The mesoscopic damage mechanisms studied here contained two types: interphase debonding between the reinforcement and matrix and the nucleation, growth, and coalescence of the voids in the matrix. As shown by the results, the interphase debonding increases the composite ductility, but results in the strengthening effects of the brittle reinforcements decreasing unfavorably.
1999, 16(2): 94-99.
Abstract:
When the compressive specimens of Al2014+15 vol% SiCp MMC were loaded approximately to 40 % in strain, the irregular oscillations in their stressstrain curves were observed for the first time. These oscillations are considered to be the macro manifestations of the fractal processes corresponding to the microcracks evolution in the specimens. The data of oscillations werefractal interpolated. An iterative function system (IFS) corresponding to a contractions affine transform can be obtained. A random iterative algorithm was used for this IFS and the constitutive relations with the fractal microcracks evolution were reconstructed satisfactorily. The power spectrums for the original oscillation curves and the reconstructed curves were analyzed. Their agreement is reasonably good. By using the GP algorithm, it is found that there is a correlation function of the attractor and the dimensionality of the attractor is 1.48. The minimum number of variables necessary to model the microcracks evolution is dete
When the compressive specimens of Al2014+15 vol% SiCp MMC were loaded approximately to 40 % in strain, the irregular oscillations in their stressstrain curves were observed for the first time. These oscillations are considered to be the macro manifestations of the fractal processes corresponding to the microcracks evolution in the specimens. The data of oscillations werefractal interpolated. An iterative function system (IFS) corresponding to a contractions affine transform can be obtained. A random iterative algorithm was used for this IFS and the constitutive relations with the fractal microcracks evolution were reconstructed satisfactorily. The power spectrums for the original oscillation curves and the reconstructed curves were analyzed. Their agreement is reasonably good. By using the GP algorithm, it is found that there is a correlation function of the attractor and the dimensionality of the attractor is 1.48. The minimum number of variables necessary to model the microcracks evolution is dete
1999, 16(2): 100-104.
Abstract:
The effect of a molybodnum net interlayer in Al2O3/Nb brazed joint on the thermal shock behaviour of the interface was studied for the first time. The existence of the net in Al2O3/Nb interface was able to increase the thermal shock resistance of the joint considerably. When it was brazed with Ni51Ti49 and Cu52Ni18Ti30 solders separately and quenched into water from 700,the thermal shock resistance of the joint with the net was raised by more than 180% and 130% respectively, compared to those of the joints without a net. The fracture topograph of the joints with the net was very different from those of the joints without a net. It was supposed that the existence of a net interlayer could markedly reduce the residual stress in the brazed interface.
The effect of a molybodnum net interlayer in Al2O3/Nb brazed joint on the thermal shock behaviour of the interface was studied for the first time. The existence of the net in Al2O3/Nb interface was able to increase the thermal shock resistance of the joint considerably. When it was brazed with Ni51Ti49 and Cu52Ni18Ti30 solders separately and quenched into water from 700,the thermal shock resistance of the joint with the net was raised by more than 180% and 130% respectively, compared to those of the joints without a net. The fracture topograph of the joints with the net was very different from those of the joints without a net. It was supposed that the existence of a net interlayer could markedly reduce the residual stress in the brazed interface.
1999, 16(2): 105-109.
Abstract:
The fabrication processing of unidirectional short carbon and Nicalon fiberreinforced LAS composites was investigated. The parameters influencing dispersion and orientation of short fiber were discussed. It is shown that homogeneity of dispersion of short fibers was much better by stirring in mixing solution of ethylene glycol and aqueous polyvinyl alcohol solution than by other methods. Unidirectional alignment of short fibers in prepreg could be obtained by doctorblade casting. The samples fabricated in the study have excellent strength and toughness.
The fabrication processing of unidirectional short carbon and Nicalon fiberreinforced LAS composites was investigated. The parameters influencing dispersion and orientation of short fiber were discussed. It is shown that homogeneity of dispersion of short fibers was much better by stirring in mixing solution of ethylene glycol and aqueous polyvinyl alcohol solution than by other methods. Unidirectional alignment of short fibers in prepreg could be obtained by doctorblade casting. The samples fabricated in the study have excellent strength and toughness.
1999, 16(2): 110-115.
Abstract:
SiC whisker reinforced multilayered Si3N4 composites with BN as separating layers were fabricated by compacting rolling, coating, laminating and hotpressing. Si3N4 was added into the separating layers to modify interfacical bonding between the matrix layers. With the increase of Si3N4 content in the separating layers, the bonding between the matrix layers changed from very weak to tight interface and the bulk mechanical properties varied accordingly. For weak interfaces, the composite exhibits very high apparent toughness up to 20 MPam1/2 with a moderate strength of about 600 MPa, while for tight interface, the composite fractures behave like monoliths and give a high strength of over 1000 MPa.
SiC whisker reinforced multilayered Si3N4 composites with BN as separating layers were fabricated by compacting rolling, coating, laminating and hotpressing. Si3N4 was added into the separating layers to modify interfacical bonding between the matrix layers. With the increase of Si3N4 content in the separating layers, the bonding between the matrix layers changed from very weak to tight interface and the bulk mechanical properties varied accordingly. For weak interfaces, the composite exhibits very high apparent toughness up to 20 MPam1/2 with a moderate strength of about 600 MPa, while for tight interface, the composite fractures behave like monoliths and give a high strength of over 1000 MPa.
1999, 16(2): 116-120.
Abstract:
Composite ultrafine NiTiN particles were prepared by active plasmametal reaction method in a mixture of N2-H2-Ar gas atmosphere. The formation mechanism of these particles is discussed. Thermodynamic calculation of chemical reactions in gas phases has been done to analyze the possibility of reactions.
Composite ultrafine NiTiN particles were prepared by active plasmametal reaction method in a mixture of N2-H2-Ar gas atmosphere. The formation mechanism of these particles is discussed. Thermodynamic calculation of chemical reactions in gas phases has been done to analyze the possibility of reactions.
1999, 16(2): 121-124.
Abstract:
In this paper, strontium lead titanate was prepared from strontium lead titanyl oxalate tetrohydrate by chemical coprecipitation. XRD, SEM, DTA, EPMA were used to analyze the powder. The effects of reactive temperature, pH value and heat treatment temperature were investigated after studying its formation and thermal decompositive mechanism.
In this paper, strontium lead titanate was prepared from strontium lead titanyl oxalate tetrohydrate by chemical coprecipitation. XRD, SEM, DTA, EPMA were used to analyze the powder. The effects of reactive temperature, pH value and heat treatment temperature were investigated after studying its formation and thermal decompositive mechanism.
1999, 16(2): 125-128.
Abstract:
Notch flexure strength of Al2O3 /TiC ceramics was tested at 20, 600and 800. Results show that the flexure strength keeps constant up to 600, and notch flexure strength can be calculated by equation(3). At 800, the flexure strength decreases, and the notch flexure strength doesn't obey equation (3) as the notch sensitivity decreases. The probability tests at high temperature show that the flexure strength and notch flexure strength follow Weibull distribution. The Weibull modules of various Kt are a constant at the same testing temperature. The dispersion of the values of flexure strength and notch flexure strength at 800 is lower than that at 20.
Notch flexure strength of Al2O3 /TiC ceramics was tested at 20, 600and 800. Results show that the flexure strength keeps constant up to 600, and notch flexure strength can be calculated by equation(3). At 800, the flexure strength decreases, and the notch flexure strength doesn't obey equation (3) as the notch sensitivity decreases. The probability tests at high temperature show that the flexure strength and notch flexure strength follow Weibull distribution. The Weibull modules of various Kt are a constant at the same testing temperature. The dispersion of the values of flexure strength and notch flexure strength at 800 is lower than that at 20.
1999, 16(2): 129-134.
Abstract:
A finite difference equation model was proposed for fabrication of unidirectional carboncarbon composites by Chemical Vapor Infiltration (CVI) process. The check experiment was designed to verify the accuracy of this model. The model results of density versus infiltration time showed good agreement with experiment data, which indicated that the model had good practicability. Moreover, much of the important information of CVI mechanism would be provided by the modeling results, such as the distribution of precursor concentration in preforms, uniformity of densification and evolving of porosity during infiltration.
A finite difference equation model was proposed for fabrication of unidirectional carboncarbon composites by Chemical Vapor Infiltration (CVI) process. The check experiment was designed to verify the accuracy of this model. The model results of density versus infiltration time showed good agreement with experiment data, which indicated that the model had good practicability. Moreover, much of the important information of CVI mechanism would be provided by the modeling results, such as the distribution of precursor concentration in preforms, uniformity of densification and evolving of porosity during infiltration.
1999, 16(2): 135-139.
Abstract:
The high order theory about the effective elastic modulus and shearing modulus for composite tubular element with arbitrary wall thickness was presented. The transverse shearing deformation effects and threedimensional elastic effects were included. The effective moduli were evaluated for three different layups( S, S and ]S) with the same wall thickness by high order theory and compared with the results evaluated by classic laminated theory. The effective modulus predicted by this theory can be used in the designing of composite tubular element structures.
The high order theory about the effective elastic modulus and shearing modulus for composite tubular element with arbitrary wall thickness was presented. The transverse shearing deformation effects and threedimensional elastic effects were included. The effective moduli were evaluated for three different layups( S, S and ]S) with the same wall thickness by high order theory and compared with the results evaluated by classic laminated theory. The effective modulus predicted by this theory can be used in the designing of composite tubular element structures.
1999, 16(2): 140-146.
Abstract:
Upper and lower bounds of effective bulk and shear moduli for a twophase elastic composite with imperfect interface are derived in the case of finite strains. In the case of very small strains, these derived bounds reduce known results for linear cases. Numerical results predict effects of the features of imperfect interface and the strains on these bounds of the effective moduli of such composites, and give reasonable results.
Upper and lower bounds of effective bulk and shear moduli for a twophase elastic composite with imperfect interface are derived in the case of finite strains. In the case of very small strains, these derived bounds reduce known results for linear cases. Numerical results predict effects of the features of imperfect interface and the strains on these bounds of the effective moduli of such composites, and give reasonable results.
1999, 16(2): 147-151.
Abstract:
Based on Tanaka and Liang's constitutive model of shape memory alloys, the linearized constitutive relation of SMA, embedded in matrix, was derived. Such a constitutive relation can easily be used in commercial finite element programs to treat the shape memory effect as the thermal effect of conventional materials. An intelligent structure, made up with TiNi belts embedded in the metal matrix to actively control the crack in the matrix, was analyzed using the method. Comparison of the calculated and test results shows that the method is practicable.
Based on Tanaka and Liang's constitutive model of shape memory alloys, the linearized constitutive relation of SMA, embedded in matrix, was derived. Such a constitutive relation can easily be used in commercial finite element programs to treat the shape memory effect as the thermal effect of conventional materials. An intelligent structure, made up with TiNi belts embedded in the metal matrix to actively control the crack in the matrix, was analyzed using the method. Comparison of the calculated and test results shows that the method is practicable.
