1994 Vol. 11, No. 1
1994, 11(1): 1-7.
Abstract:
This paper presents a review of the research on nanocomposites.The methods of preparing this newly developed materials are described. The microstructure,mechanical behaviour and enhancing mechanism are also included.Finally,comments are given to the prospects of this kind of materials.
This paper presents a review of the research on nanocomposites.The methods of preparing this newly developed materials are described. The microstructure,mechanical behaviour and enhancing mechanism are also included.Finally,comments are given to the prospects of this kind of materials.
1994, 11(1): 9-14.
Abstract:
In this paper,the kinetics of air oxidation of felt base carbon/carbon composites is investigated at different temperatures (773-1173 K). With the help of SEM, the micrographs of carbon/carbon composites are studied after different debrees of oxidation.The experimental results are shown that the oxidation rate of felt base carbon/carbon composites is constant at a given temperature.When the oxidation temperature is below and above 873k,the oxidation mechanisms of carbon/carbon composites are different and their apparent activation energies are 96 kJ/mol and 128 kJ/mol respectively.During the carbon/carbon composites oxidation initial stage,carbon felt is oxidized much more rapidly than matrix carbon,while during the carbon/carbon composites oxidation final stage,oxidation rate of matrix carbon increases.Otherwise,the oxidation rate of felt base carbon/carbon composites is influenced by the carbon/carbon composite surface reaction rate,the gas phase diffusion and the catalysts.
In this paper,the kinetics of air oxidation of felt base carbon/carbon composites is investigated at different temperatures (773-1173 K). With the help of SEM, the micrographs of carbon/carbon composites are studied after different debrees of oxidation.The experimental results are shown that the oxidation rate of felt base carbon/carbon composites is constant at a given temperature.When the oxidation temperature is below and above 873k,the oxidation mechanisms of carbon/carbon composites are different and their apparent activation energies are 96 kJ/mol and 128 kJ/mol respectively.During the carbon/carbon composites oxidation initial stage,carbon felt is oxidized much more rapidly than matrix carbon,while during the carbon/carbon composites oxidation final stage,oxidation rate of matrix carbon increases.Otherwise,the oxidation rate of felt base carbon/carbon composites is influenced by the carbon/carbon composite surface reaction rate,the gas phase diffusion and the catalysts.
1994, 11(1): 15-21.
Abstract:
SiC whiskers from five manufactures were characterized by bulk chemical techninues, X-ray photoelectron spectroscopy, X-ray diffraction,and TEM.The oxygen content with oxide of SiC whisker sintered from rice hull resembles Si-O-C glass, while the oxyen content with oxide of SiC whisker sintered from C and SiO2 resembles SiO2.The thesis comes to the conclusion that BP-SiCw produced by CHN is as Good in characters as other four samples of SiCw manufactured by USA and Japan,respectively.
SiC whiskers from five manufactures were characterized by bulk chemical techninues, X-ray photoelectron spectroscopy, X-ray diffraction,and TEM.The oxygen content with oxide of SiC whisker sintered from rice hull resembles Si-O-C glass, while the oxyen content with oxide of SiC whisker sintered from C and SiO2 resembles SiO2.The thesis comes to the conclusion that BP-SiCw produced by CHN is as Good in characters as other four samples of SiCw manufactured by USA and Japan,respectively.
1994, 11(1): 23-28.
Abstract:
Chemical analysis, Infrared Spectroscopy(IR) and X-Ray Diffraction(XRD) have been used to study the preparation process of kaofinite-polyacrylamide intercalation com pound.Acrylamide morower was intercalated by displacing DMSO from kaolinite-DMSO intercalation compound. IR spectroscopy showed the formation of hydrogen bonds between the organic molecules and the external hydroxyls of kaolinite.When the organic mole-cules were intercalated,XRD pattern showed the increasing of the basal spacing of kaolinite.After the ltaolinite-acrylamide intercaiation compound was properly heated,the polymerization of acrylamide monomer between the layers of kaolinite was completed. The resulted kaolinite-polyacrylamide intercalation compound was resistant to decomposition by wates washing.
Chemical analysis, Infrared Spectroscopy(IR) and X-Ray Diffraction(XRD) have been used to study the preparation process of kaofinite-polyacrylamide intercalation com pound.Acrylamide morower was intercalated by displacing DMSO from kaolinite-DMSO intercalation compound. IR spectroscopy showed the formation of hydrogen bonds between the organic molecules and the external hydroxyls of kaolinite.When the organic mole-cules were intercalated,XRD pattern showed the increasing of the basal spacing of kaolinite.After the ltaolinite-acrylamide intercaiation compound was properly heated,the polymerization of acrylamide monomer between the layers of kaolinite was completed. The resulted kaolinite-polyacrylamide intercalation compound was resistant to decomposition by wates washing.
1994, 11(1): 29-35.
Abstract:
Dissolving behaviour of WC in WC/steel composite material has been investigated.Qualitative and quantitative analyses of the phase composition have been conducted with an electron probe and SEM. The phase structure analyses have been performed by using an X-ray diffractometer.The microstructure of the composite material has been examined by using optical microscope and TEM. Results are shown that dissolving and precipitation processes between WC and steel matrix of the WC/steel compolite material occur during sintering and heat treatment because of the interaction between WC and steel matrix,and the chemical composition of the matrix changed.This may affect the heat treatment process and the structure and properties of the composite material.
Dissolving behaviour of WC in WC/steel composite material has been investigated.Qualitative and quantitative analyses of the phase composition have been conducted with an electron probe and SEM. The phase structure analyses have been performed by using an X-ray diffractometer.The microstructure of the composite material has been examined by using optical microscope and TEM. Results are shown that dissolving and precipitation processes between WC and steel matrix of the WC/steel compolite material occur during sintering and heat treatment because of the interaction between WC and steel matrix,and the chemical composition of the matrix changed.This may affect the heat treatment process and the structure and properties of the composite material.
1994, 11(1): 36-41.
Abstract:
The possibility of producing short carbon fiber reinforced copper matrix composite has been studied in the paper.The composite has high density and carbon fibers are well-distributed in the matrix The effect of volume of carbon fiber on the tensile strength,thermal expansion coefficient thermal conductivity and electrical con ductivity of the composite has been studied.The results indicate that the tensile strength,thermal expansion coefficient,thermal rease with the increase of the conductivity and electrical conductivity decvolume of carbon fiber.
The possibility of producing short carbon fiber reinforced copper matrix composite has been studied in the paper.The composite has high density and carbon fibers are well-distributed in the matrix The effect of volume of carbon fiber on the tensile strength,thermal expansion coefficient thermal conductivity and electrical con ductivity of the composite has been studied.The results indicate that the tensile strength,thermal expansion coefficient,thermal rease with the increase of the conductivity and electrical conductivity decvolume of carbon fiber.
1994, 11(1): 42-47.
Abstract:
In this paper tensile tests at different temperatures and TEM analyses of SiCp/Al-Li composite fabricated by powder metallurgy technique were carried out.The results indicate that the composite exhibits high am bient temperature strength and tow elongation-to-failure.The precipitate free zones (PFZs) were formed on the grain boundaries and the interfaces between SiC particulates and Al-Li matrix.Microcracks often initiate on the grain boundaries and the interfaces.The composite displays the fracture features of the dimple and intergranular fracture.
In this paper tensile tests at different temperatures and TEM analyses of SiCp/Al-Li composite fabricated by powder metallurgy technique were carried out.The results indicate that the composite exhibits high am bient temperature strength and tow elongation-to-failure.The precipitate free zones (PFZs) were formed on the grain boundaries and the interfaces between SiC particulates and Al-Li matrix.Microcracks often initiate on the grain boundaries and the interfaces.The composite displays the fracture features of the dimple and intergranular fracture.
1994, 11(1): 49-58.
Abstract:
In this paper we first review a recent effective medium theory for composite materials properties.It is then suitably extended for the description of the elastic properties of isotropic binary composites.The formulation is used to study the shear modulus of a ccmposite with a dispersion of spheres,srecializing to the limiting cases of rigid and soft inclusions.Exact formulas for the two cases are obtained and compared with known experimental results.
In this paper we first review a recent effective medium theory for composite materials properties.It is then suitably extended for the description of the elastic properties of isotropic binary composites.The formulation is used to study the shear modulus of a ccmposite with a dispersion of spheres,srecializing to the limiting cases of rigid and soft inclusions.Exact formulas for the two cases are obtained and compared with known experimental results.
1994, 11(1): 59-65.
Abstract:
The bending characteristic of large deflections for the glass fiber-epoxy matrix multidirectional laminates,including the specimen of beams, rectangular and triangular plates under the action of concentrated load at point A are investigated in this paper.The maximum deflections 8 are between 2.5 to 10.0 times of the thickness h of the specimens.The basic behavior and the law revealed from these experiments will be of help to develop a foundational theory and the calculation method for the laminates.
The bending characteristic of large deflections for the glass fiber-epoxy matrix multidirectional laminates,including the specimen of beams, rectangular and triangular plates under the action of concentrated load at point A are investigated in this paper.The maximum deflections 8 are between 2.5 to 10.0 times of the thickness h of the specimens.The basic behavior and the law revealed from these experiments will be of help to develop a foundational theory and the calculation method for the laminates.
1994, 11(1): 67-72.
Abstract:
This paper presents a new method for predicting notched strength of composites——the method of stress field intensity,in which the intensity of stress field near the notch was taken as the parameter to estimate the notched specimen,but not only the peak stress value at the notch root.A general expression for predicting notched strength was given and formula for use easily was deduced.The results of predicting some experimental data using this method show that this new method is satisfactory.
This paper presents a new method for predicting notched strength of composites——the method of stress field intensity,in which the intensity of stress field near the notch was taken as the parameter to estimate the notched specimen,but not only the peak stress value at the notch root.A general expression for predicting notched strength was given and formula for use easily was deduced.The results of predicting some experimental data using this method show that this new method is satisfactory.
1994, 11(1): 73-84.
Abstract:
The Hamilton canonical equation for laminated composite plates is derived,and a semi-analytical solution is also obtained in this paper.By the separation of variables, the general finite element method can be used in the direction of the thickness and is derived by the state space control method,and the shear effect is solved.By employing the transfer matrix method,the continuity of displacem ents and stresses is satisfied, and the number of variables is greatly reduced.
The Hamilton canonical equation for laminated composite plates is derived,and a semi-analytical solution is also obtained in this paper.By the separation of variables, the general finite element method can be used in the direction of the thickness and is derived by the state space control method,and the shear effect is solved.By employing the transfer matrix method,the continuity of displacem ents and stresses is satisfied, and the number of variables is greatly reduced.
1994, 11(1): 85-93.
Abstract:
The transverse compression properties and failure features of glass fibre,carbon fibre and carbon/glass hybrid fibres composites are investigated with two epoxy resins as matrix.The fact that the experimental values of the transverse compression strength of composites are more than the theoretical values predicted by Greszczuk's formula, and Tsars formula and Chamis' formula are examined.The resul is are as follows 1.The transverse compression properties of composites rely on the properties of matrix and fibre.The transverse compression modulus is increased with matrix modulus.For the same matrix, the moduli are:GFRP>HFRP>CFRP. 2.The internal stress changement in composites under compression is different from that under tensile.Although the transverse compression strength of composites is mainly dependent on that of matrix,it is not less than but more than the compression strength of matrix.The prediction of the transverse compression strength can not imitate the treating method of the transverse tensile.3.The semi-emprical formula of the prediction for the transverse compression strength of composites is given.The predictions are in agreement with the experimental values and the formula is identified with the pretro-spective experiment.
The transverse compression properties and failure features of glass fibre,carbon fibre and carbon/glass hybrid fibres composites are investigated with two epoxy resins as matrix.The fact that the experimental values of the transverse compression strength of composites are more than the theoretical values predicted by Greszczuk's formula, and Tsars formula and Chamis' formula are examined.The resul is are as follows 1.The transverse compression properties of composites rely on the properties of matrix and fibre.The transverse compression modulus is increased with matrix modulus.For the same matrix, the moduli are:GFRP>HFRP>CFRP. 2.The internal stress changement in composites under compression is different from that under tensile.Although the transverse compression strength of composites is mainly dependent on that of matrix,it is not less than but more than the compression strength of matrix.The prediction of the transverse compression strength can not imitate the treating method of the transverse tensile.3.The semi-emprical formula of the prediction for the transverse compression strength of composites is given.The predictions are in agreement with the experimental values and the formula is identified with the pretro-spective experiment.
1994, 11(1): 95-103.
Abstract:
A description is given for a complex variable-variational method (CYVM) to investigate the stress intensity factors (S.I.F.)for the double notch edbe crack in isotropic or orthotropic plate subjected to pin loads.Numerical studies reveal that the convergent results are given by a quite simple program whicli reduces data manipulation and computer time. A very satisfactory degree of accuracy is obtained from the results when compared with the findings of earlier studies.
A description is given for a complex variable-variational method (CYVM) to investigate the stress intensity factors (S.I.F.)for the double notch edbe crack in isotropic or orthotropic plate subjected to pin loads.Numerical studies reveal that the convergent results are given by a quite simple program whicli reduces data manipulation and computer time. A very satisfactory degree of accuracy is obtained from the results when compared with the findings of earlier studies.
1994, 11(1): 105-111.
Abstract:
For the effective elastic moduli (EEM) of composites only the shapes of inclusions and the mechanical properties of matrix and inclusions are considered,and the sizes as well as the interaction of inclusions are discarded by the Eshelby equivalent inclusion method[1], the Budiansky and Wu pelf-consistent method[3].The paper takes it into account that the volume fraction of inclusions increases and the interaction of ones is more pro mivent.According to this,EEM of materiais are deduced by considering the shapes,sizes,distribution and interaction of inclusions in the paper.Finally,the distribution of inclusions and the Poisson-ratio of matrix which a fect EEM of composites are given and some results are compared with the ezperirrental data reported in the paper.From the comparison of results, the results of the paper coincide well with the experimental data.
For the effective elastic moduli (EEM) of composites only the shapes of inclusions and the mechanical properties of matrix and inclusions are considered,and the sizes as well as the interaction of inclusions are discarded by the Eshelby equivalent inclusion method[1], the Budiansky and Wu pelf-consistent method[3].The paper takes it into account that the volume fraction of inclusions increases and the interaction of ones is more pro mivent.According to this,EEM of materiais are deduced by considering the shapes,sizes,distribution and interaction of inclusions in the paper.Finally,the distribution of inclusions and the Poisson-ratio of matrix which a fect EEM of composites are given and some results are compared with the ezperirrental data reported in the paper.From the comparison of results, the results of the paper coincide well with the experimental data.
1994, 11(1): 113-118.
Abstract:
The mode I interlaminar fracture toubhness of graphitc bismaleimide composite is investigated in this paper by using the hinge double cantilever beam specimen.Some expressions of interlaminar fracture toughness GIC are evaluated and compared. The results obtained by methods based on adopting the third polynomial and power function to fit the experimentally measured compliance are satisfactory.The result of test in dicates that the influence of fiber bridging on GIC of unidirection lamina is obvious.The value of GIC will decrease twenty percent and the scatter of GIC will also decrease obviously after cutting bridging fiber by razor blade.In addition,the value of GIC increases with the increase of specimen thickness.
The mode I interlaminar fracture toubhness of graphitc bismaleimide composite is investigated in this paper by using the hinge double cantilever beam specimen.Some expressions of interlaminar fracture toughness GIC are evaluated and compared. The results obtained by methods based on adopting the third polynomial and power function to fit the experimentally measured compliance are satisfactory.The result of test in dicates that the influence of fiber bridging on GIC of unidirection lamina is obvious.The value of GIC will decrease twenty percent and the scatter of GIC will also decrease obviously after cutting bridging fiber by razor blade.In addition,the value of GIC increases with the increase of specimen thickness.
