1995 Vol. 12, No. 4
1995, 12(4): 1-7.
Abstract:
Whiskers are now playing an increasingly important role in the development of new types of composite materials with high performance.This paper presents an overview of the whiskers,Including thelr characteristics and properties,methods and technology of preparation,microstructure and growth mechanisms,strengthening and toughening effects in composites,and in particular,their practlcal applications in industry.Also included are some problems to be solved for further development and extensive use of the whisker-reinforced composite materials.
Whiskers are now playing an increasingly important role in the development of new types of composite materials with high performance.This paper presents an overview of the whiskers,Including thelr characteristics and properties,methods and technology of preparation,microstructure and growth mechanisms,strengthening and toughening effects in composites,and in particular,their practlcal applications in industry.Also included are some problems to be solved for further development and extensive use of the whisker-reinforced composite materials.
1995, 12(4): 8-11.
Abstract:
Technology of manufacturing boron carbide particle/magnesium alloy(B4CP/ZMS) composite by squeeze casting process and second processing properties of the blank of thls composite have been investigated.The compressive strength,hardness and density of boron carbide partlcle/magneslum alloy composite were measured.The boron carbide particle/magnesium alloy composite 15 shown to have low density,high strength and hardness,good forming and second processing propertles.
Technology of manufacturing boron carbide particle/magnesium alloy(B4CP/ZMS) composite by squeeze casting process and second processing properties of the blank of thls composite have been investigated.The compressive strength,hardness and density of boron carbide partlcle/magneslum alloy composite were measured.The boron carbide particle/magnesium alloy composite 15 shown to have low density,high strength and hardness,good forming and second processing propertles.
1995, 12(4): 12-16.
Abstract:
The research on the principle and process of crystallized alumina-silica short fiber was made in this paper in order to lmprove the properties of the amorphous fibers and the composlte materials.The reaction phenomena of flbers with Al-51 alloys were examinedby EDX,X-ray diffraction,EPMA and TEM.As a result,the crystallized alumlna-silica short fibers show hlgher hardness than amorphous alumina-silica short fiber and have remarkable stability in chemical reaction with molten metal.Increase in ultimate tensile strength at elevated temperature of the crystalllzed alumina-sillca fibers reinforced Al-Si alloy was observed.
The research on the principle and process of crystallized alumina-silica short fiber was made in this paper in order to lmprove the properties of the amorphous fibers and the composlte materials.The reaction phenomena of flbers with Al-51 alloys were examinedby EDX,X-ray diffraction,EPMA and TEM.As a result,the crystallized alumlna-silica short fibers show hlgher hardness than amorphous alumina-silica short fiber and have remarkable stability in chemical reaction with molten metal.Increase in ultimate tensile strength at elevated temperature of the crystalllzed alumina-sillca fibers reinforced Al-Si alloy was observed.
1995, 12(4): 17-21.
Abstract:
A ceramic matrix composite was made from aiumina and iron grain with electroless nickel coating.The influence of the iron grain on the properties of the composite material was investigated.The strengthening mechanlsm of lron grain with nickel coating was studied.
A ceramic matrix composite was made from aiumina and iron grain with electroless nickel coating.The influence of the iron grain on the properties of the composite material was investigated.The strengthening mechanlsm of lron grain with nickel coating was studied.
1995, 12(4): 22-29.
Abstract:
To examine the wettability between Ni3Al and TiC,this work uses a densified TiC matrix and two kinds of raw Ni3Al materlals one is a mass form prepared by a melting method and the other 15 a Powder form prepared by an SHS method.By using a hightemperature mlcroscope,the Ni3Al-TIC contact angle is measured under 142O℃ with the protection of Ar gas.The result indicates that for either of the two kinds of Ni3Al,the Ni3Al-TIC contact angle is within 18°,showing a good wettability between the two materials.When Mo is added into the Ni3Al powder,the contact angle is decreased to 11°Then,the composition struture fracture image and element distribution of the tested specimens are also analysed,and the mechanism improving the Ni3Al-TIC wettability by adding Mo is discussed.
To examine the wettability between Ni3Al and TiC,this work uses a densified TiC matrix and two kinds of raw Ni3Al materlals one is a mass form prepared by a melting method and the other 15 a Powder form prepared by an SHS method.By using a hightemperature mlcroscope,the Ni3Al-TIC contact angle is measured under 142O℃ with the protection of Ar gas.The result indicates that for either of the two kinds of Ni3Al,the Ni3Al-TIC contact angle is within 18°,showing a good wettability between the two materials.When Mo is added into the Ni3Al powder,the contact angle is decreased to 11°Then,the composition struture fracture image and element distribution of the tested specimens are also analysed,and the mechanism improving the Ni3Al-TIC wettability by adding Mo is discussed.
1995, 12(4): 30-34.
Abstract:
In thls paper,the propertles of electroless deposlted NI-P-B4C coating,Ni-P-SiC coating,Ni-P coating and electroplated chromium coating were compared It was found that electroless deposlted Ni-P-B<4C coatlng is the best wear resisting material.Since B4C particles have higherh:trdness and antl-mlcrocut capabillty,the wear reslstance of Ni-P-B4C coating is higher than that of Ni-P-SiC coating and of Ni-P coating.Because the coating hardness will drop down rapidly with frlctlonal heat rising,the wear reslstance of electroplated chromlum coating is worse in them.
In thls paper,the propertles of electroless deposlted NI-P-B4C coating,Ni-P-SiC coating,Ni-P coating and electroplated chromium coating were compared It was found that electroless deposlted Ni-P-B<4C coatlng is the best wear resisting material.Since B4C particles have higherh:trdness and antl-mlcrocut capabillty,the wear reslstance of Ni-P-B4C coating is higher than that of Ni-P-SiC coating and of Ni-P coating.Because the coating hardness will drop down rapidly with frlctlonal heat rising,the wear reslstance of electroplated chromlum coating is worse in them.
1995, 12(4): 35-38.
Abstract:
A review is given as to the state of affairs and future trends of aircraft composite materials.Summarized are the properties the composites have to Possess,in order to meet the requirements set by the aeronautlcal and astronautical technology.Resin matrlx Composites are classified according to their applications to different components of the aircraft,and their corresponding different properties requirernents are Put forward.It is clearly pointed out that the resin matrix plays an important role in determining the material properties.The approaches to this respect are analyzed and the gaps between home and abroad are found.Finally some suggestions are made on how to make use of the foreign experlence,and how to develop and perfect our own series according to domestic conditions.
A review is given as to the state of affairs and future trends of aircraft composite materials.Summarized are the properties the composites have to Possess,in order to meet the requirements set by the aeronautlcal and astronautical technology.Resin matrlx Composites are classified according to their applications to different components of the aircraft,and their corresponding different properties requirernents are Put forward.It is clearly pointed out that the resin matrix plays an important role in determining the material properties.The approaches to this respect are analyzed and the gaps between home and abroad are found.Finally some suggestions are made on how to make use of the foreign experlence,and how to develop and perfect our own series according to domestic conditions.
1995, 12(4): 39-43.
Abstract:
In this paper,effects of peroxlde on curing reaction of modified BMI resin (designed as 4501A)with low dielectric loss were studied.Baslc components of 4501A are N,N'-blsmaleimidodiphenyl methane and allylphenyl compound.Tests,such as DSC analysis,gel characteristics of resin and propertles of neat resin show that the inltlator can strikingly reduce the curing temperature of resln.Propertles of both neat resin and composlte contalning initiator were all shown.Results indicated that the initiator has no effect on dielectric properties of neat resin but can greatly improve its heat distortion temperature.
In this paper,effects of peroxlde on curing reaction of modified BMI resin (designed as 4501A)with low dielectric loss were studied.Baslc components of 4501A are N,N'-blsmaleimidodiphenyl methane and allylphenyl compound.Tests,such as DSC analysis,gel characteristics of resin and propertles of neat resin show that the inltlator can strikingly reduce the curing temperature of resln.Propertles of both neat resin and composlte contalning initiator were all shown.Results indicated that the initiator has no effect on dielectric properties of neat resin but can greatly improve its heat distortion temperature.
1995, 12(4): 44-48.
Abstract:
The technical properties of a new high molecular weight PPS and rnethods of preparing middle-length fiber relnforced composites of this polyme:have been studied.It is made sure that suspension impregnatlon of fiber-felt process is an avallable method to make the new composlte.Epoxy is used as a bonder to bind up PPS and felt as well as a cover to prevent PPS from oxidatlon.Mechanical properties of the new composite are tested and the “Uniformity design”is used to find out the best technical parameters.The middle-length fiber reinforced thermoplastlc PPS composite prepared by this Process has better ProPerties than that prepared by the RFC process developed in the Dow Chemical Company.Especially, when the temperature is up to 250C,its tensile strength still remains 89MPa.
The technical properties of a new high molecular weight PPS and rnethods of preparing middle-length fiber relnforced composites of this polyme:have been studied.It is made sure that suspension impregnatlon of fiber-felt process is an avallable method to make the new composlte.Epoxy is used as a bonder to bind up PPS and felt as well as a cover to prevent PPS from oxidatlon.Mechanical properties of the new composite are tested and the “Uniformity design”is used to find out the best technical parameters.The middle-length fiber reinforced thermoplastlc PPS composite prepared by this Process has better ProPerties than that prepared by the RFC process developed in the Dow Chemical Company.Especially, when the temperature is up to 250C,its tensile strength still remains 89MPa.
1995, 12(4): 49-54.
Abstract:
Based on the friction and wear behavior of poly(ether ether ketone)(PEEK),its structure characteristics including the bulk one and the debris which results from the Process of the friction and wear rate were studied to reveal the mechanism.The load dependence of the frictlon coefficient and wear rate in the high-load region was found to be different from that in the high one.It has been shown that the friction surficial layer of PEEK bulk experiences a change in solid structure but remalns unmelted,and wear is due to its fatigue fracture during the friction when the load is low.However,the:urficial layer is in a rnelted state and crossllnking takes place in it when the load is hlgh.At this time,the friction surface Increases and the wear is related to the adheslon transfer of PEEK into the steel wheel.
Based on the friction and wear behavior of poly(ether ether ketone)(PEEK),its structure characteristics including the bulk one and the debris which results from the Process of the friction and wear rate were studied to reveal the mechanism.The load dependence of the frictlon coefficient and wear rate in the high-load region was found to be different from that in the high one.It has been shown that the friction surficial layer of PEEK bulk experiences a change in solid structure but remalns unmelted,and wear is due to its fatigue fracture during the friction when the load is low.However,the:urficial layer is in a rnelted state and crossllnking takes place in it when the load is hlgh.At this time,the friction surface Increases and the wear is related to the adheslon transfer of PEEK into the steel wheel.
1995, 12(4): 55-60.
Abstract:
In order to lmprove theh,gh temperature oxldatlon resistance of carbon/carbon composites,superfine slllcon carbide was added to carbon fiber fabrlc/phenolic aldehyde conlposites,and then sintered at hlgh temperature in the atmosphere of pure argon.A new composite——carbon fiber fabr,c reinforced SIC/C co-slntered alloy was developed. Thermogravlmetrlc analysls Indlcated that the oxidatlon reslstance of the slntered alloy at high temperature was several ten times hlgher than that of the carbon/carbon composites in use of the airplane brake-shoe.The rnaceratlon of the alloy with liquid phenolic aldehyde could highly enhance the denslty,mechanical propertles and high temperature oxidatlon reslstance of the alloy.In thls paper,the effects of the materlals ratio,the formation technology and the maceratlon on the mlcrostructure and propertles of the alloy were studied in detail.
In order to lmprove theh,gh temperature oxldatlon resistance of carbon/carbon composites,superfine slllcon carbide was added to carbon fiber fabrlc/phenolic aldehyde conlposites,and then sintered at hlgh temperature in the atmosphere of pure argon.A new composite——carbon fiber fabr,c reinforced SIC/C co-slntered alloy was developed. Thermogravlmetrlc analysls Indlcated that the oxidatlon reslstance of the slntered alloy at high temperature was several ten times hlgher than that of the carbon/carbon composites in use of the airplane brake-shoe.The rnaceratlon of the alloy with liquid phenolic aldehyde could highly enhance the denslty,mechanical propertles and high temperature oxidatlon reslstance of the alloy.In thls paper,the effects of the materlals ratio,the formation technology and the maceratlon on the mlcrostructure and propertles of the alloy were studied in detail.
1995, 12(4): 61-65.
Abstract:
The isolated oxygen barrier layer of circuit protection devices consisting of organic PTC (positive temperature coefficient)is studied. The experimental results indicate that the electrical.stability of the devices is improved when they are covered with an epoxy resins layer of which oxygen permeability rate is less than 4×10-9cc/cm2/mm/sec/cm Hg at 25℃.
The isolated oxygen barrier layer of circuit protection devices consisting of organic PTC (positive temperature coefficient)is studied. The experimental results indicate that the electrical.stability of the devices is improved when they are covered with an epoxy resins layer of which oxygen permeability rate is less than 4×10-9cc/cm2/mm/sec/cm Hg at 25℃.
1995, 12(4): 66-71.
Abstract:
The three-phase ceramic composite(Ti,Zr)N has been prepared by high temperature nitridation and anneal of an ultra pure TiZr alloy. This result is different from the previous works which had concluded that the titanium nitride and zirconium nitride could only form a single solid solution with complete miscibility through all the composition range. The techniques including X-ray diffraction (XRD),energy-dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM) have been used to characterize the crystal structures and the chemical composition of the composite. The XRD analyses have given the information about the structural properties of the material (3 phases,all having face centered cubic structure with different lattice parameters).The chemical microanalyses have given the relative atomic percentage ratios of the metailic elements in each phase as well as their approximative chemical expressions. In combination with HRTEM,it was finally established that the phase with the biggest lattice parameter is rich in Zr,the phase with the smallest lattice parameter rich in Ti,and the phase with a middle lattice parameter has nearly equalatomic metallic elements.
The three-phase ceramic composite(Ti,Zr)N has been prepared by high temperature nitridation and anneal of an ultra pure TiZr alloy. This result is different from the previous works which had concluded that the titanium nitride and zirconium nitride could only form a single solid solution with complete miscibility through all the composition range. The techniques including X-ray diffraction (XRD),energy-dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM) have been used to characterize the crystal structures and the chemical composition of the composite. The XRD analyses have given the information about the structural properties of the material (3 phases,all having face centered cubic structure with different lattice parameters).The chemical microanalyses have given the relative atomic percentage ratios of the metailic elements in each phase as well as their approximative chemical expressions. In combination with HRTEM,it was finally established that the phase with the biggest lattice parameter is rich in Zr,the phase with the smallest lattice parameter rich in Ti,and the phase with a middle lattice parameter has nearly equalatomic metallic elements.
1995, 12(4): 72-78.
Abstract:
The statistical analysis of in-situ fiber bundle failure was examined for 3D C/C composites by different processing technology. An in-situ interfacial strength testing instrument was used to determine the fiber/matrix bond properties of C/C composites. This paper also introduces a micromechanics model for the study of the stress and strain fields along the fiber/matrix interface and provides a description method of the interface properties by the debonding force and mechanical properties of fiber,matrix and composites. The analysis shows that the results can provide an optimal design of C/C composites. Associated with high temperature processing are the phenomena of fiber bundle strength loss up to about 20%.Comparing the different interfaces reveals that fiber bundles in the z direction have the best bonding and the strongest interphase.
The statistical analysis of in-situ fiber bundle failure was examined for 3D C/C composites by different processing technology. An in-situ interfacial strength testing instrument was used to determine the fiber/matrix bond properties of C/C composites. This paper also introduces a micromechanics model for the study of the stress and strain fields along the fiber/matrix interface and provides a description method of the interface properties by the debonding force and mechanical properties of fiber,matrix and composites. The analysis shows that the results can provide an optimal design of C/C composites. Associated with high temperature processing are the phenomena of fiber bundle strength loss up to about 20%.Comparing the different interfaces reveals that fiber bundles in the z direction have the best bonding and the strongest interphase.
1995, 12(4): 79-83.
Abstract:
The method of reduced region is used to solve the layer sequence optimization problem of composite laminates that have the specified layer number and angles,to satisfy the requirements of vibration frequencies and modal damping. By means of calculation of a 20-ply symmetrical composite laminate,it can be shown that using this method can not only save a lot of computational time,but also make the frequencies and modal damping capacities coincide well with the experimental results,and thus the reliability of this method is proved.The research in this paper can be used as an effective method in engineering design,and the software is of special engineering value.
The method of reduced region is used to solve the layer sequence optimization problem of composite laminates that have the specified layer number and angles,to satisfy the requirements of vibration frequencies and modal damping. By means of calculation of a 20-ply symmetrical composite laminate,it can be shown that using this method can not only save a lot of computational time,but also make the frequencies and modal damping capacities coincide well with the experimental results,and thus the reliability of this method is proved.The research in this paper can be used as an effective method in engineering design,and the software is of special engineering value.
1995, 12(4): 84-89.
Abstract:
This paper describes an experimental study on the creep damage behavior of cross-plied glass cloth/epoxy composites. Based on Kachanov-Rabotnov's theoretical pattern,the damage evaluation equation and creep constitutive equation including shear yield can be developed. The experimental results show that the creep deformation along the fiber direction can be ignored since it is very small. However,the creep deformation is quite large,even when the load is applied in other directions. The results demonstrate that the experimental data is stable and coincides with the theoretical curve as the working stress is within the scope of 45-60% of the rupture stress.
This paper describes an experimental study on the creep damage behavior of cross-plied glass cloth/epoxy composites. Based on Kachanov-Rabotnov's theoretical pattern,the damage evaluation equation and creep constitutive equation including shear yield can be developed. The experimental results show that the creep deformation along the fiber direction can be ignored since it is very small. However,the creep deformation is quite large,even when the load is applied in other directions. The results demonstrate that the experimental data is stable and coincides with the theoretical curve as the working stress is within the scope of 45-60% of the rupture stress.
1995, 12(4): 90-93.
Abstract:
1995, 12(4): 94-98.
Abstract:
Applying plane photoelastic experiment and strain measurement with three resistance strain gages,the stress concentration factors of a limited wide orthotropic elastic tensile plate around a hole in the centre were determined. A comparison suggests that the results from the two methods are quite in agreement,which shows that they are effective and practical.
Applying plane photoelastic experiment and strain measurement with three resistance strain gages,the stress concentration factors of a limited wide orthotropic elastic tensile plate around a hole in the centre were determined. A comparison suggests that the results from the two methods are quite in agreement,which shows that they are effective and practical.
1995, 12(4): 99-105.
Abstract:
The physical basis of nondestructive testing for composite structures using the coin-tap method has been investigated. A typical criterion of inspecting defects is established. Meantime.the minimum detectable defect for GFRP composite laminates including different defects has been analyzed in detail. A defect of lOmm diameter under a 2mm thick laminate is at the margin of detectability. Therefore,the method is particularly attractive for use in the field and on laminate structures that may be porous.
The physical basis of nondestructive testing for composite structures using the coin-tap method has been investigated. A typical criterion of inspecting defects is established. Meantime.the minimum detectable defect for GFRP composite laminates including different defects has been analyzed in detail. A defect of lOmm diameter under a 2mm thick laminate is at the margin of detectability. Therefore,the method is particularly attractive for use in the field and on laminate structures that may be porous.
1995, 12(4): 106-111.
Abstract:
The compressive bifurcation of a laminated plate composed of fibers and matrix under uniaxial compression,which is assumd to be a damage strain softening material,is investigated:Using the finite deformation theory and semi-analytical finite element method,the bifurcation equations are established,and then a numerical simulation is evaluated. The results show that the bifurcation occurs during a strain softening of the damage materials,and this bifurcation is a one of shearing band. In a damaged material the shear strain is concentrated and the shear strain jumping appears in the neighbourhood of an interface between the fibers and matrix.
The compressive bifurcation of a laminated plate composed of fibers and matrix under uniaxial compression,which is assumd to be a damage strain softening material,is investigated:Using the finite deformation theory and semi-analytical finite element method,the bifurcation equations are established,and then a numerical simulation is evaluated. The results show that the bifurcation occurs during a strain softening of the damage materials,and this bifurcation is a one of shearing band. In a damaged material the shear strain is concentrated and the shear strain jumping appears in the neighbourhood of an interface between the fibers and matrix.
1995, 12(4): 112-118.
Abstract:
The sectional warping corrective theory is used. The statics equilibrium equation for composite laminated plates is derived by means of the principle of minimum potential energy. In the plate plane,two-dimension hierarchical displacement functions are adopted during numerical analysis. The obtained numerical results for both displacement and stress distrihution in the thickness direction of a rectanguler bidirectional composite laminated plate are compared tenth the exact solution;as a consequence,the present method is shown to have good convergence.
The sectional warping corrective theory is used. The statics equilibrium equation for composite laminated plates is derived by means of the principle of minimum potential energy. In the plate plane,two-dimension hierarchical displacement functions are adopted during numerical analysis. The obtained numerical results for both displacement and stress distrihution in the thickness direction of a rectanguler bidirectional composite laminated plate are compared tenth the exact solution;as a consequence,the present method is shown to have good convergence.
1995, 12(4): 119-124.
Abstract:
The constitutive relation of pure bending deformation of the shape memory alloy wire hybrid fiber reinforced composite beam is obtained in terms of the one dimensional thermo-mechanical constitutive relation of the shape memory alloy. The curvature change of the beam due to the variation of temperature is analysed.
The constitutive relation of pure bending deformation of the shape memory alloy wire hybrid fiber reinforced composite beam is obtained in terms of the one dimensional thermo-mechanical constitutive relation of the shape memory alloy. The curvature change of the beam due to the variation of temperature is analysed.
1995, 12(4): 125-129.
Abstract:
This paper presents a Fourier series solution for bending problems of unsymmetric angle-ply plates with various boundary conditions,using the generalized virtual load method. Moreover,the formulation for accelerating convergence of Fourier series and the method for differentiating the series,item by item and arbitrary times,are given.
This paper presents a Fourier series solution for bending problems of unsymmetric angle-ply plates with various boundary conditions,using the generalized virtual load method. Moreover,the formulation for accelerating convergence of Fourier series and the method for differentiating the series,item by item and arbitrary times,are given.
