1992 Vol. 9, No. 1
1992, 9(1): 1-6.
Abstract:
The dyramic tensile rrocesses of silicon carbide whisker reinforced 6061A1 composite (SiGw/6061A1)have been in situ observed by scanning clectron microscope.T he effect of off-a xis angle on strength and fracture behavior has been studied in detail.The results show that microcracks are resalted from the matrix adjacent to whiskers.The initiation and propagation of crack depend on the off-axis angle of whisker,and the optimum off-axis angle (θ0) at which the transition from forward fracture to shear fracture occurs is about 45-50°.
The dyramic tensile rrocesses of silicon carbide whisker reinforced 6061A1 composite (SiGw/6061A1)have been in situ observed by scanning clectron microscope.T he effect of off-a xis angle on strength and fracture behavior has been studied in detail.The results show that microcracks are resalted from the matrix adjacent to whiskers.The initiation and propagation of crack depend on the off-axis angle of whisker,and the optimum off-axis angle (θ0) at which the transition from forward fracture to shear fracture occurs is about 45-50°.
1992, 9(1): 7-12.
Abstract:
The superplasticity of SiCp/2024Al composite made by PM was studied.The strain rate sensitivity index of hot-0xtruded SiCp/2024Al composite tension and compression was measured.The effect of technical parameters on superplasticity of SiCp/2024Al composite was analyzed and the superplastically forming parameters were chosen.The preliminary study of the microstructure of SiCp/2024Al composite and the fracture mechanism of superplastic tensile specimens were conducted.
The superplasticity of SiCp/2024Al composite made by PM was studied.The strain rate sensitivity index of hot-0xtruded SiCp/2024Al composite tension and compression was measured.The effect of technical parameters on superplasticity of SiCp/2024Al composite was analyzed and the superplastically forming parameters were chosen.The preliminary study of the microstructure of SiCp/2024Al composite and the fracture mechanism of superplastic tensile specimens were conducted.
1992, 9(1): 13-18.
Abstract:
Coating silicon oarbtde (SiC) on the surface of carbon fibers (CFs) is a good way to improve the oxidation-resistance of Chs and resist interaction between GFs and metals at high temperature.In this paper chemical vapor deposition(CVD) have been used for coating SiC continuously. The investigation of dependency of canting thickness,deposition and crystal structure on deposition parameters have been conducted to obtain the mean activation energy of 165 KJ/mol in the system and main structure of β-SiC. And we emphatically analysed the strength of coating CFs and identified that the degrease in strength of SiC-coated GFs was caused by the chemical attack of H+ and other ions during GYD,existence of free silicon as well as residual stress.
Coating silicon oarbtde (SiC) on the surface of carbon fibers (CFs) is a good way to improve the oxidation-resistance of Chs and resist interaction between GFs and metals at high temperature.In this paper chemical vapor deposition(CVD) have been used for coating SiC continuously. The investigation of dependency of canting thickness,deposition and crystal structure on deposition parameters have been conducted to obtain the mean activation energy of 165 KJ/mol in the system and main structure of β-SiC. And we emphatically analysed the strength of coating CFs and identified that the degrease in strength of SiC-coated GFs was caused by the chemical attack of H+ and other ions during GYD,existence of free silicon as well as residual stress.
1992, 9(1): 19-22.
Abstract:
Processing is one of the most important aspects of metal matrix composites.The physical properties of carbon fibre reinforced silver and copper composites were measured to prove the effect of sintering processing on the properties of composites.The characteristic of short carbon fibre must be considered owing to the influence of carbon fibre on the sintering processing of composite.
Processing is one of the most important aspects of metal matrix composites.The physical properties of carbon fibre reinforced silver and copper composites were measured to prove the effect of sintering processing on the properties of composites.The characteristic of short carbon fibre must be considered owing to the influence of carbon fibre on the sintering processing of composite.
1992, 9(1): 23-30.
Abstract:
Functionally gradient material (FGM) was a new concept developed by Japanese scientists six years ago.The two sides of FGM are composed of different kinds of materials with different properties to face harsh conditions. While the composition and micro-structure of the materials between the two parts are changing gradiently that there are no interfaces inside FGM. In this way,we can eliminate the non-matching factors of properties in linking parts.This kind of materials will find wide applications and high service value in astronautic technology and nuclear industry.This paper describes the design idea of FGM, the advances on the study of FGM, and the work on FGM conducted by ourselves.Different preparation methods are reviewed and compared.
Functionally gradient material (FGM) was a new concept developed by Japanese scientists six years ago.The two sides of FGM are composed of different kinds of materials with different properties to face harsh conditions. While the composition and micro-structure of the materials between the two parts are changing gradiently that there are no interfaces inside FGM. In this way,we can eliminate the non-matching factors of properties in linking parts.This kind of materials will find wide applications and high service value in astronautic technology and nuclear industry.This paper describes the design idea of FGM, the advances on the study of FGM, and the work on FGM conducted by ourselves.Different preparation methods are reviewed and compared.
1992, 9(1): 31-36.
Abstract:
Vinylester resin can be thickened by diisocyanate eompounds.The factors which influence the thickening of vinylester resin were investigated. It was found from IR spectroscopy and chemical analysis that the amount of -NCO and -OH groups in the system decrease during the thickening process.
Vinylester resin can be thickened by diisocyanate eompounds.The factors which influence the thickening of vinylester resin were investigated. It was found from IR spectroscopy and chemical analysis that the amount of -NCO and -OH groups in the system decrease during the thickening process.
1992, 9(1): 37-41.
Abstract:
The residual stress arising from the volume shrinkage on curing can be measured by means of measuring the nenequilibrium voltage of bridge which consists of a straingage resistance immersing into the surface layer of resin as an arm.By using the method,we measured the residual shear stresses with an order of 10'Pa for T31-Epoxy resin system which is small compared with imidazole-epoxy resin and triethanolamine-epoxy resin system,
The residual stress arising from the volume shrinkage on curing can be measured by means of measuring the nenequilibrium voltage of bridge which consists of a straingage resistance immersing into the surface layer of resin as an arm.By using the method,we measured the residual shear stresses with an order of 10'Pa for T31-Epoxy resin system which is small compared with imidazole-epoxy resin and triethanolamine-epoxy resin system,
1992, 9(1): 43-48.
Abstract:
A new high temperature bismaleimide resin system with improved processability are prepared,which consists of a hot melting mixture of two bismaleimides and divinylbenzene.One of two bismaleimides is 4,4'-bisma leidodiphenylmethane,a comercial product, and another is a substituted bismaleimide which was synthesised by ourselves.This new bismalcimide resin system has a low melting point (about 60℃),better solubility (soluble in aceton,solution can be used in making prepreg), and low curing temperature(180℃).Composite fabricated from this resin exhibits high thermal stability,and its strength retentivity at 250℃ is more than 60%.
A new high temperature bismaleimide resin system with improved processability are prepared,which consists of a hot melting mixture of two bismaleimides and divinylbenzene.One of two bismaleimides is 4,4'-bisma leidodiphenylmethane,a comercial product, and another is a substituted bismaleimide which was synthesised by ourselves.This new bismalcimide resin system has a low melting point (about 60℃),better solubility (soluble in aceton,solution can be used in making prepreg), and low curing temperature(180℃).Composite fabricated from this resin exhibits high thermal stability,and its strength retentivity at 250℃ is more than 60%.
1992, 9(1): 49-58.
Abstract:
In this paper,the general equations of motion for displacements of thin elastic orthotropic spherical shell are derived.These equations also contain the influences of rotatory inertia.On this basis, the response of spherical shell subiected to a shock load is calculated by using finite difference method.Finally, this result is compared with the test of helmets of motrobicycle subjected to a shock load.
In this paper,the general equations of motion for displacements of thin elastic orthotropic spherical shell are derived.These equations also contain the influences of rotatory inertia.On this basis, the response of spherical shell subiected to a shock load is calculated by using finite difference method.Finally, this result is compared with the test of helmets of motrobicycle subjected to a shock load.
1992, 9(1): 59-64.
Abstract:
In this paper a triangular element method of composite sandwich plates is developed for which the bending stiffness and coupling stiffness of faceplates are considered. The general buckling of composite sandwich plates is calculated and analysed.The effects of plies of faceplates and ratio of the thick ness bettween the core and the faceplates on buckling load have been discussed.The equations related with resultant forces, moments and strains are derived.These formulas have been analysed and finally it is pointed out in the paper that the effects of coupling stiffness of faceplates can not be arbitrarily neglected,even under the condition that all the plies of sandwich plate is symmetrical.
In this paper a triangular element method of composite sandwich plates is developed for which the bending stiffness and coupling stiffness of faceplates are considered. The general buckling of composite sandwich plates is calculated and analysed.The effects of plies of faceplates and ratio of the thick ness bettween the core and the faceplates on buckling load have been discussed.The equations related with resultant forces, moments and strains are derived.These formulas have been analysed and finally it is pointed out in the paper that the effects of coupling stiffness of faceplates can not be arbitrarily neglected,even under the condition that all the plies of sandwich plate is symmetrical.
1992, 9(1): 65-69.
Abstract:
The Felicity effect of the acoustic emission in glass reinforced composite was explored in this paper. The tests were performed for interlaminar shear specimens and specimens with a surface notch under uniaxial tension.Total counts, count rate and amplitude level of AE were detected under loading.The results indicate that characteristics of AE for specimens with a surface notch are similar to one of interlaminar shear specimens.However,the difference of AE signals for two types of specimens is apparent when they approach final failure.Especially,it should also be noted that the Kaiser effect sppeares at lower loading level,but the Felicity effect is increasingly apparent with the raise of load level for two types of specimens.
The Felicity effect of the acoustic emission in glass reinforced composite was explored in this paper. The tests were performed for interlaminar shear specimens and specimens with a surface notch under uniaxial tension.Total counts, count rate and amplitude level of AE were detected under loading.The results indicate that characteristics of AE for specimens with a surface notch are similar to one of interlaminar shear specimens.However,the difference of AE signals for two types of specimens is apparent when they approach final failure.Especially,it should also be noted that the Kaiser effect sppeares at lower loading level,but the Felicity effect is increasingly apparent with the raise of load level for two types of specimens.
1992, 9(1): 70-78.
Abstract:
The orthogot al multilayer sandwich plate which provides considerable strength,stiffness and stability has been used in some important engineering structures,such as the composite material bridge.The analytical theory proposed in this paper is based on the multilayer sandwich plate consisting of orthogonal decks and cores with various thickness and different shear deformations in cores, and the theory posseses generality in nature.It can be readily shown that Hoff's theory and Reissner's theory are merely the particular cases of multilayer sandwich plate when reduced to the single layer condition.
The orthogot al multilayer sandwich plate which provides considerable strength,stiffness and stability has been used in some important engineering structures,such as the composite material bridge.The analytical theory proposed in this paper is based on the multilayer sandwich plate consisting of orthogonal decks and cores with various thickness and different shear deformations in cores, and the theory posseses generality in nature.It can be readily shown that Hoff's theory and Reissner's theory are merely the particular cases of multilayer sandwich plate when reduced to the single layer condition.
1992, 9(1): 79-84.
Abstract:
The paper presents a self-consistent finite element method (SCFEM) dealing with inclusion problems.Based on self-consistent model, the average elastic properties of effective medium are calculated by the finite element iteration procedure.As applications of this method, the average elastic moduli for unidirectional short-fiber composites are obtained and the effect of fiber geometry on average elastic properties of composites are investigated.The numerical results agree well with those of experiments.
The paper presents a self-consistent finite element method (SCFEM) dealing with inclusion problems.Based on self-consistent model, the average elastic properties of effective medium are calculated by the finite element iteration procedure.As applications of this method, the average elastic moduli for unidirectional short-fiber composites are obtained and the effect of fiber geometry on average elastic properties of composites are investigated.The numerical results agree well with those of experiments.
1992, 9(1): 85-91.
Abstract:
The integrated 3-D braid technique for composites is a new textile high technology developed in the United States in 80's.A new structure of composites is created by means of the technology,so that mechanical properties of composites are improved obviously in many aspects.It is indicated by the present applications that the high technology and new structure could be applied in mzny areas,such as aeronautics and astronautics communications,transportation,oil and chemical industry,weaponry,sports goods, etc.The characteristics,structural fabrics and some excellent performances are described in this paper.
The integrated 3-D braid technique for composites is a new textile high technology developed in the United States in 80's.A new structure of composites is created by means of the technology,so that mechanical properties of composites are improved obviously in many aspects.It is indicated by the present applications that the high technology and new structure could be applied in mzny areas,such as aeronautics and astronautics communications,transportation,oil and chemical industry,weaponry,sports goods, etc.The characteristics,structural fabrics and some excellent performances are described in this paper.
1992, 9(1): 93-99.
Abstract:
The Finite-Layer Nlethcd is presented in this paper.By using Jones model of materials and the Finite-Layer Method the maxrnum deflection and coupled effect between bending and extension under cylindrical bending of 2-layer angle ply compression are discussed.The Method mentioned above is applicable to the calculation of symmetric and aniisymmetric angle-ply Laminates with different moduli subjected to the tension or compression loads.
The Finite-Layer Nlethcd is presented in this paper.By using Jones model of materials and the Finite-Layer Method the maxrnum deflection and coupled effect between bending and extension under cylindrical bending of 2-layer angle ply compression are discussed.The Method mentioned above is applicable to the calculation of symmetric and aniisymmetric angle-ply Laminates with different moduli subjected to the tension or compression loads.
