1995 Vol. 12, No. 2
1995, 12(2): 1-4.
Abstract:
In the process of particulate reinforced metal matrix composites the injection of the solid particulate into the molten metal is computed in this paper.By considering the resistance for the injection of a particulate as comprising drag,surface force and buoyancy,a criterion has been derived.For the implant of a particulate there is a minimum impinging velocity of a particulate onto the melt.Larger diameters of particulates,improvement in the wetting condition,and an increase of kinetic energy of particulates will favor the initiation of particulate transfer to melt.
In the process of particulate reinforced metal matrix composites the injection of the solid particulate into the molten metal is computed in this paper.By considering the resistance for the injection of a particulate as comprising drag,surface force and buoyancy,a criterion has been derived.For the implant of a particulate there is a minimum impinging velocity of a particulate onto the melt.Larger diameters of particulates,improvement in the wetting condition,and an increase of kinetic energy of particulates will favor the initiation of particulate transfer to melt.
1995, 12(2): 5-9.
Abstract:
The processing parameter of SiC(Nicalon)/Al composites can influence interfacial bonding status between fiber and matrix.This paper established an in situ interfacial strength testing instrument (ISISTI).Based on this ISISTI,the single-fiber push-out test and the analysis of the interfacial bonding strength for Nicalon/Al composites have been carried out.The results indicate that the data of interfacial bonding strength in Nicalon/Al composites evidently correspond to the processing condition.Therefore,this paper offers a method available for evaluating the interfacial chemical reaction and directing composites processing.
The processing parameter of SiC(Nicalon)/Al composites can influence interfacial bonding status between fiber and matrix.This paper established an in situ interfacial strength testing instrument (ISISTI).Based on this ISISTI,the single-fiber push-out test and the analysis of the interfacial bonding strength for Nicalon/Al composites have been carried out.The results indicate that the data of interfacial bonding strength in Nicalon/Al composites evidently correspond to the processing condition.Therefore,this paper offers a method available for evaluating the interfacial chemical reaction and directing composites processing.
1995, 12(2): 10-14.
Abstract:
The directional solidification of aluminium matrix composites,reinforced by carbon fiber with non-wettable SiC coatings,was presented in this paper.The functions of directional solidification velocity to the solidification processing and morphology were studied,and the columnar dendrite with different arm spacing and cellular crystal were obtained in the matrix between the fiber bunches.It has been found that the tensile strength of non-wettable system composites decreased after directional solidification,and the mechanism was also probed.
The directional solidification of aluminium matrix composites,reinforced by carbon fiber with non-wettable SiC coatings,was presented in this paper.The functions of directional solidification velocity to the solidification processing and morphology were studied,and the columnar dendrite with different arm spacing and cellular crystal were obtained in the matrix between the fiber bunches.It has been found that the tensile strength of non-wettable system composites decreased after directional solidification,and the mechanism was also probed.
1995, 12(2): 15-20.
Abstract:
Infiltration pressure models fabricating MMCs by the squeeze infiltration method were established according to the basic principle of hydromechanics and Laplace equation.The infiltration process of ZA22/Al2O3 composites was analysed and ZA22/Al2O3 composites with excellent properties were prepared under the guidance of the models.
Infiltration pressure models fabricating MMCs by the squeeze infiltration method were established according to the basic principle of hydromechanics and Laplace equation.The infiltration process of ZA22/Al2O3 composites was analysed and ZA22/Al2O3 composites with excellent properties were prepared under the guidance of the models.
1995, 12(2): 21-25.
Abstract:
This paper studies the sintering characteristics and venting quality of A3S2/Fe composite and effectiveness of short fiber reinforcement,and analyzes the formation mechanism of its macrostructure and microstructure in sintering.Experimental results show that A3S2/Fe composite has the good sintering properties at sintering temperatures of 900-1000℃,a hard layer forms in the surface of the composite when the sample is sintered,and short fibers obviously reinforce this composite.The compressive strength of the composite can reach 17-23MPa,and the venting quality is within the range of 4.30-9.69cm3/(cm2·s·atm),which can meet the needs in application.
This paper studies the sintering characteristics and venting quality of A3S2/Fe composite and effectiveness of short fiber reinforcement,and analyzes the formation mechanism of its macrostructure and microstructure in sintering.Experimental results show that A3S2/Fe composite has the good sintering properties at sintering temperatures of 900-1000℃,a hard layer forms in the surface of the composite when the sample is sintered,and short fibers obviously reinforce this composite.The compressive strength of the composite can reach 17-23MPa,and the venting quality is within the range of 4.30-9.69cm3/(cm2·s·atm),which can meet the needs in application.
1995, 12(2): 26-31.
Abstract:
The processes of the deformation,the crack initiation and growth in SiCw/Al composite have been observed by means of the in-situ transmission electron microscopy straining techniques.The results indicate that a great deal of dislocations would arise around grain boundaries and whiskers in the early deformation stages.Cracks are initiated mainly in whisker-riched regions and by the crack of the whiskers injured during the preparation for the composite.The whiskers and grain boundaries in the composite play an important role in impeding the crack growth.When the whisker in front of a crack tip is perpendicular to the crack,the crack tip would blunt near the whisker side and then advance along its nearinterface-region.Under the condition of the whisker in front of a crack tip parallel to the crack,the crack tip would blunt near the whisker end and then propagate along the nearinterface-region.
The processes of the deformation,the crack initiation and growth in SiCw/Al composite have been observed by means of the in-situ transmission electron microscopy straining techniques.The results indicate that a great deal of dislocations would arise around grain boundaries and whiskers in the early deformation stages.Cracks are initiated mainly in whisker-riched regions and by the crack of the whiskers injured during the preparation for the composite.The whiskers and grain boundaries in the composite play an important role in impeding the crack growth.When the whisker in front of a crack tip is perpendicular to the crack,the crack tip would blunt near the whisker side and then advance along its nearinterface-region.Under the condition of the whisker in front of a crack tip parallel to the crack,the crack tip would blunt near the whisker end and then propagate along the nearinterface-region.
1995, 12(2): 32-36.
Abstract:
The properties of friction,wear and limit PV of JS material under the lubrication of 20# mechanical lubricant oil,lO# gasoline engine lubricant oil,1OW30CD diesel engine lubricant oil,glycerol and triethanolamine were studied using the MPV+1500 friction tester.The results show that the properties of friction,wear and limit PV of JS material are greatly improved with the lubrication of the lubricant mediums above.The friction coefficient is decreased by 2 to 3 orders of magnitude,the wear is decreased by 1 to 2 orders of magnitude,and the limit PV value is increased at least by 1 order of magnitude.The limit PV value of JS material is above 120 MPa·m/s with the lubrication of the 5 kinds of lubricant mediums,it is about 100 times as much as that of pure PTFE bearing(dry friction),and several times of that of babbit metal bearing with the lubrication of 20# mechanical lubricant oil.JS material can be applied in practice as a kind of sliding bearing which has a high PV value under the lubrication of the lubricant mediums above.
The properties of friction,wear and limit PV of JS material under the lubrication of 20# mechanical lubricant oil,lO# gasoline engine lubricant oil,1OW30CD diesel engine lubricant oil,glycerol and triethanolamine were studied using the MPV+1500 friction tester.The results show that the properties of friction,wear and limit PV of JS material are greatly improved with the lubrication of the lubricant mediums above.The friction coefficient is decreased by 2 to 3 orders of magnitude,the wear is decreased by 1 to 2 orders of magnitude,and the limit PV value is increased at least by 1 order of magnitude.The limit PV value of JS material is above 120 MPa·m/s with the lubrication of the 5 kinds of lubricant mediums,it is about 100 times as much as that of pure PTFE bearing(dry friction),and several times of that of babbit metal bearing with the lubrication of 20# mechanical lubricant oil.JS material can be applied in practice as a kind of sliding bearing which has a high PV value under the lubrication of the lubricant mediums above.
1995, 12(2): 37-41.
Abstract:
The friction surfaces of the friction pair consisting of the semimetallic friction material and cast iron were examinated by scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDX).The experimental results show that copper can transfer onto the friction surface of the cast iron counterpart by smearing,adhering and ploughing.Because of the smear and back transfer,the distribution of copper is more dispersive in the friction surface of the friction material after friction.However,there exists a lot of iron on the copper fibers in the friction surface of the friction material with iron and iron oxide wear debris adhering and mounting.These actions of the copper fibers make the friction pair have a stable friction coefficient and an excellent wear resistance.Moreover,the orientation of copper fibers has a great influence upon the friction and wear characteristics of the friction material.The coefficient of friction,wear loss and temperature at the friction interface where the fibers are perpendicular to the friction interface are lower than those at the interface where the fibers are parallel to the friction interface but perpendicular to the sliding direction.
The friction surfaces of the friction pair consisting of the semimetallic friction material and cast iron were examinated by scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDX).The experimental results show that copper can transfer onto the friction surface of the cast iron counterpart by smearing,adhering and ploughing.Because of the smear and back transfer,the distribution of copper is more dispersive in the friction surface of the friction material after friction.However,there exists a lot of iron on the copper fibers in the friction surface of the friction material with iron and iron oxide wear debris adhering and mounting.These actions of the copper fibers make the friction pair have a stable friction coefficient and an excellent wear resistance.Moreover,the orientation of copper fibers has a great influence upon the friction and wear characteristics of the friction material.The coefficient of friction,wear loss and temperature at the friction interface where the fibers are perpendicular to the friction interface are lower than those at the interface where the fibers are parallel to the friction interface but perpendicular to the sliding direction.
1995, 12(2): 42-46.
Abstract:
The influence of fiber pre-stressing during curing of VIRALL laminates on its tensile properties has been experimentally investigated on the basis of studying the tensile behavior of Vinylon strands.It is revealed that pre-stressing of fibers could effectively increase the elastic limit,yielding strength and fracture strength of VIRALL laminates.
The influence of fiber pre-stressing during curing of VIRALL laminates on its tensile properties has been experimentally investigated on the basis of studying the tensile behavior of Vinylon strands.It is revealed that pre-stressing of fibers could effectively increase the elastic limit,yielding strength and fracture strength of VIRALL laminates.
1995, 12(2): 47-51.
Abstract:
The effect of anod treatment on the interface adhesion between carbon fibers with DMF cement has been investigated in this work.The experimental results show that the anod treatment is an effective method to increase the interface adhesion of carbon fibers/MDF cement.The strength σf and impact energy absorption αk of untreated carbon fiber reinforced MDF cement composite are lower than those of the matrix.The σf and αk of the composite,in which the carbon fibers are treated by anod treatment,are much greater than those of the matrix,and as a result the anod treatment can considerably increase the carbon fiber/MDF cement interface adhesion.When the content of pitch-based carbon fiber is 2.0wt% and is treated at optimum conditions,the σf and αk and ak of the composite can reach 116.4MPa and 1.63kJ/m2,respectively.
The effect of anod treatment on the interface adhesion between carbon fibers with DMF cement has been investigated in this work.The experimental results show that the anod treatment is an effective method to increase the interface adhesion of carbon fibers/MDF cement.The strength σf and impact energy absorption αk of untreated carbon fiber reinforced MDF cement composite are lower than those of the matrix.The σf and αk of the composite,in which the carbon fibers are treated by anod treatment,are much greater than those of the matrix,and as a result the anod treatment can considerably increase the carbon fiber/MDF cement interface adhesion.When the content of pitch-based carbon fiber is 2.0wt% and is treated at optimum conditions,the σf and αk and ak of the composite can reach 116.4MPa and 1.63kJ/m2,respectively.
1995, 12(2): 52-58.
Abstract:
The thermal expansivity of particle-filled as well as unidirectional fibre reinforced composite materials is calculated by a numerical method based on Effective Medium Theory (EMT).Thermal expansion coefficients so obtained show good conformity with experimental data.A comparison with the results calculated from Schapery and Kerner equations is also made,indicating the good applicability of EMT to thermal expansivity of composites.
The thermal expansivity of particle-filled as well as unidirectional fibre reinforced composite materials is calculated by a numerical method based on Effective Medium Theory (EMT).Thermal expansion coefficients so obtained show good conformity with experimental data.A comparison with the results calculated from Schapery and Kerner equations is also made,indicating the good applicability of EMT to thermal expansivity of composites.
1995, 12(2): 59-66.
Abstract:
In the present paper the on-axis and off-axis elasticity of composite lamina is analysed.Through analysing the elastic characteristics of composite laminated plates and shells,a new set of general stability equations of composite laminate shells is established.
In the present paper the on-axis and off-axis elasticity of composite lamina is analysed.Through analysing the elastic characteristics of composite laminated plates and shells,a new set of general stability equations of composite laminate shells is established.
1995, 12(2): 67-76.
Abstract:
The behaviour of nonlinear stability of the stiffened plates under various inplane combined loadings is studied by variational principle and generalized Fourier series method.The equations are solved by use of Newton-gradient method.The pre-buckling compressing-bending coupling effect greatly affects the buckling and post-buckling behaviour of elastically supported composite stiffened plates so that the transverse deflection is produced when the compressing and shearing load starts to act on the plates.The pre-buckling coupling effect is not obvious only when the stiffened plates are clamped at four edges.Some relevant behaviour completely different from that of non-stiffened laminated plates is also obtained.The results predicted are in good agreement with the relevant calculated and experimental results in previous papers.
The behaviour of nonlinear stability of the stiffened plates under various inplane combined loadings is studied by variational principle and generalized Fourier series method.The equations are solved by use of Newton-gradient method.The pre-buckling compressing-bending coupling effect greatly affects the buckling and post-buckling behaviour of elastically supported composite stiffened plates so that the transverse deflection is produced when the compressing and shearing load starts to act on the plates.The pre-buckling coupling effect is not obvious only when the stiffened plates are clamped at four edges.Some relevant behaviour completely different from that of non-stiffened laminated plates is also obtained.The results predicted are in good agreement with the relevant calculated and experimental results in previous papers.
1995, 12(2): 77-82.
Abstract:
Residual thermo-strain and microcracks are the major factors which affect the behaviour of whisker toughening ceramic matrix composite materials(CMC).In this paper,the two factors are taken into account.Meanwhile,the effects of whiskers and microcracks on the effective modulus and strength of the material are researched,involving the random distribution and the content of the whiskers and the microcracks,the aspect ratio of the whiskers and the size of the microcracks.The theoretical results show that all those above factors have influence on the mechanic behaviour of the materials in different degrees.The conclusions are beneficial for the optimization of CMC.
Residual thermo-strain and microcracks are the major factors which affect the behaviour of whisker toughening ceramic matrix composite materials(CMC).In this paper,the two factors are taken into account.Meanwhile,the effects of whiskers and microcracks on the effective modulus and strength of the material are researched,involving the random distribution and the content of the whiskers and the microcracks,the aspect ratio of the whiskers and the size of the microcracks.The theoretical results show that all those above factors have influence on the mechanic behaviour of the materials in different degrees.The conclusions are beneficial for the optimization of CMC.
1995, 12(2): 83-88.
Abstract:
This paper studies the structure and property of 3-D reinforced fibrous composites.A micromechanical model is established by analysing a kind of 3-D manual textile structural composite,and based on this analytical model,the constitutive relation reflecting its macro-properties is obtained.Some experiments are carried out to prove the theoretical results of this paper by using the 3-D composites specimens that have the same textile structure.In addition,the contrastive tests are done between the 3-D reinforced composites and laminated composites.It shows that the average properties of composites,especially the interlayer property,are greatly improved and increased because of the 3-D reinforcement.
This paper studies the structure and property of 3-D reinforced fibrous composites.A micromechanical model is established by analysing a kind of 3-D manual textile structural composite,and based on this analytical model,the constitutive relation reflecting its macro-properties is obtained.Some experiments are carried out to prove the theoretical results of this paper by using the 3-D composites specimens that have the same textile structure.In addition,the contrastive tests are done between the 3-D reinforced composites and laminated composites.It shows that the average properties of composites,especially the interlayer property,are greatly improved and increased because of the 3-D reinforcement.
1995, 12(2): 89-94.
Abstract:
The creep property of ARALL laminates at 130℃ with different prestresses and different adhesives is investigated respectively in this paper.It imitated the creep curves of the laminates by using the aging theory which is one of the phenomenological analysis methods,and analysed them through combining macro-phenomenon and micro-mechanism.The results show that the creep of ARALL is mainly due to aluminium alloy,and applying prestress lowers the residual stress of the laminates,so the creep strain is reduced.On the other hand,adopting the adhesive with high modulus is advantageous to lowering the creep strain of the laminates.
The creep property of ARALL laminates at 130℃ with different prestresses and different adhesives is investigated respectively in this paper.It imitated the creep curves of the laminates by using the aging theory which is one of the phenomenological analysis methods,and analysed them through combining macro-phenomenon and micro-mechanism.The results show that the creep of ARALL is mainly due to aluminium alloy,and applying prestress lowers the residual stress of the laminates,so the creep strain is reduced.On the other hand,adopting the adhesive with high modulus is advantageous to lowering the creep strain of the laminates.
1995, 12(2): 95-101.
Abstract:
The impact force of laminates and sandwich panels in low velocity impact loading has been measured and calculated.The purpose of the study is to compare the impact behavior of laminates and sandwich panels and to determine the effect of protective surface layers on the impact behavior of the laminates and sandwich panels.
The impact force of laminates and sandwich panels in low velocity impact loading has been measured and calculated.The purpose of the study is to compare the impact behavior of laminates and sandwich panels and to determine the effect of protective surface layers on the impact behavior of the laminates and sandwich panels.
1995, 12(2): 102-107.
Abstract:
Solutions of elastic stresses of a single fiber-reinforced composite under an applied load parallel to the axis of the fiber are given.The radial distribution of the axial stress in the matrix,the distribution of the axial stress in the fiber and that of the interfacial shear stress along the fiber are presented.And the effects of the fiber-to-matrix elastic modulus ration on the maximum fiber axial stress and the maximum interfacial shear stress are studied.Also,a comparison between the present study and the existing works is made.Finally,this study gives the solutions of elastic stresses of a multi-fiber-reinforced composites.
Solutions of elastic stresses of a single fiber-reinforced composite under an applied load parallel to the axis of the fiber are given.The radial distribution of the axial stress in the matrix,the distribution of the axial stress in the fiber and that of the interfacial shear stress along the fiber are presented.And the effects of the fiber-to-matrix elastic modulus ration on the maximum fiber axial stress and the maximum interfacial shear stress are studied.Also,a comparison between the present study and the existing works is made.Finally,this study gives the solutions of elastic stresses of a multi-fiber-reinforced composites.
1995, 12(2): 108-117.
Abstract:
The average elastic-plastic behavior of composite materals is discussed.The general formulation of the composite material with prolate spheroid inclusion and with the matrix is shown when the matrix and the inclusion are isotropic materials.The volume of any inclusion is smaller than that of the matrix,and the inclusions fit tightly against the matrix.The overall average Young's modulus,average shear elasticity and average Poisson's ratio of the composite material with prolate spheroid inclusions are shown,and it is proved that this composite material is nonisotropic.The way to increase the average elastic moduli of the composite material is also found.
The average elastic-plastic behavior of composite materals is discussed.The general formulation of the composite material with prolate spheroid inclusion and with the matrix is shown when the matrix and the inclusion are isotropic materials.The volume of any inclusion is smaller than that of the matrix,and the inclusions fit tightly against the matrix.The overall average Young's modulus,average shear elasticity and average Poisson's ratio of the composite material with prolate spheroid inclusions are shown,and it is proved that this composite material is nonisotropic.The way to increase the average elastic moduli of the composite material is also found.
1995, 12(2): 118-123.
Abstract:
The Dinh-Armstrong constitutive equation is used to derive analytic expressions for the viscosity and the normal stress difference in shear and elongational deformation of nondilute,short-fiber suspensions in Newtonian media.This is achieved by approximating the fourth order orientation tensor of the integral constitutive equation with the components of the Finger strain tensor according to Curries expressions that relate the strain tensor to flow kinematics.The derived analytic expressions are in agreement with the numerical results given by Dinh-Armstrong in simple shear flow.In elongation,although the magnitudes of dimensionless viscosity at start-up and steady state are identical,there is quantitative disagreement in the values in-between.
The Dinh-Armstrong constitutive equation is used to derive analytic expressions for the viscosity and the normal stress difference in shear and elongational deformation of nondilute,short-fiber suspensions in Newtonian media.This is achieved by approximating the fourth order orientation tensor of the integral constitutive equation with the components of the Finger strain tensor according to Curries expressions that relate the strain tensor to flow kinematics.The derived analytic expressions are in agreement with the numerical results given by Dinh-Armstrong in simple shear flow.In elongation,although the magnitudes of dimensionless viscosity at start-up and steady state are identical,there is quantitative disagreement in the values in-between.
1995, 12(2): 124-126.
Abstract:
An introduction is presented to the formation process of bamboo/glass fiber reinforced plastics bridges by using the formation technique of three basic circle composite materials.In the present widely-used reinforced concrete bridges,stone bridges,and steel-girder bridges,up to 40-50% of the material is employed to support their own weight due to the heavy weight of the material itself,whereas a bamboo/glass fiber reinforced plastics bridge is featurde by its light weight and low cost.Experiments show that excellent properties of structures can be obtained by applying the formation technique of the three basic circle composite materials.
An introduction is presented to the formation process of bamboo/glass fiber reinforced plastics bridges by using the formation technique of three basic circle composite materials.In the present widely-used reinforced concrete bridges,stone bridges,and steel-girder bridges,up to 40-50% of the material is employed to support their own weight due to the heavy weight of the material itself,whereas a bamboo/glass fiber reinforced plastics bridge is featurde by its light weight and low cost.Experiments show that excellent properties of structures can be obtained by applying the formation technique of the three basic circle composite materials.
