1999 Vol. 16, No. 1
1999, 16(1): 1-7.
Abstract:
This paper gives a brief introduction to recent development in SMA intelligent composite structures research.Emphasis is placed on results dealing with constitutive modeling,vibration,structural acoustics,low velocity impact and crack growth control by embedding SMA in composite structures.Some further investigations of this area are also suggested.
This paper gives a brief introduction to recent development in SMA intelligent composite structures research.Emphasis is placed on results dealing with constitutive modeling,vibration,structural acoustics,low velocity impact and crack growth control by embedding SMA in composite structures.Some further investigations of this area are also suggested.
1999, 16(1): 8-13.
Abstract:
The design idea of Functionally Gradient Materials(FGM) is adopted to develop Metal Matrix Composites(MMCs) and the aluminum alloy matrix gradient composites reinforced with SiC particles are fabricated successfully. Experimental study is made on microscopic structure and compressive performance of the materials at high temperature. The results show that specific density of the materials can be increased and the gradient boundary layers can be eliminated by means of the second compressing and resintering power metallurgy technique, the true stress strain curves of the materials at the high temperature can be divided into two parts, strain hardening and strain weakening, the matrix has influence on strength at the high temperature but not the particles, relatively sliding motion is not found in the gradient boundary layers of the materials, and the deformation is related to the ways of gradient distribution of the materials.
The design idea of Functionally Gradient Materials(FGM) is adopted to develop Metal Matrix Composites(MMCs) and the aluminum alloy matrix gradient composites reinforced with SiC particles are fabricated successfully. Experimental study is made on microscopic structure and compressive performance of the materials at high temperature. The results show that specific density of the materials can be increased and the gradient boundary layers can be eliminated by means of the second compressing and resintering power metallurgy technique, the true stress strain curves of the materials at the high temperature can be divided into two parts, strain hardening and strain weakening, the matrix has influence on strength at the high temperature but not the particles, relatively sliding motion is not found in the gradient boundary layers of the materials, and the deformation is related to the ways of gradient distribution of the materials.
1999, 16(1): 14-21.
Abstract:
The paper declares the course of metal explosive welding and its essence of metal physics, summarizes its character and usage, and the paper introduces the variety and assortment of metal composite material by explosive welding. The way of explosive welding and metal composite material have a good prospect. The article points out its important technique and economic value, and it should have a good development in our country.
The paper declares the course of metal explosive welding and its essence of metal physics, summarizes its character and usage, and the paper introduces the variety and assortment of metal composite material by explosive welding. The way of explosive welding and metal composite material have a good prospect. The article points out its important technique and economic value, and it should have a good development in our country.
1999, 16(1): 22-29.
Abstract:
Oxide sols were prepared with Si(OEt)4, AlCl3, and Al(NO3) 3. Well distributed and inseparable Al2O3 SiO2 coating, which can be transformed to Mullite crystalline at high temperature, on carbon fibers was obtained by sol gel and inorganization processes. The coating improved carbon fiber's resistance to oxidation at high temperature and compatibilities with the matrixes of aluminum and SiC ceramic.
Oxide sols were prepared with Si(OEt)4, AlCl3, and Al(NO3) 3. Well distributed and inseparable Al2O3 SiO2 coating, which can be transformed to Mullite crystalline at high temperature, on carbon fibers was obtained by sol gel and inorganization processes. The coating improved carbon fiber's resistance to oxidation at high temperature and compatibilities with the matrixes of aluminum and SiC ceramic.
1999, 16(1): 30-34.
Abstract:
The microstructure, shape and interface of plasma spraying nickel coating on aluminium alloy were observed by metallography and SEM. An irregular melting line was formed by thick oxide film between aluminium alloy and spraying nickel coating,which stopped the welding reaction. So the available technological condition had some difficulty to get metallurgical bond. And the bonding mechanism of them was discussed.
The microstructure, shape and interface of plasma spraying nickel coating on aluminium alloy were observed by metallography and SEM. An irregular melting line was formed by thick oxide film between aluminium alloy and spraying nickel coating,which stopped the welding reaction. So the available technological condition had some difficulty to get metallurgical bond. And the bonding mechanism of them was discussed.
1999, 16(1): 35-40.
Abstract:
Interface is a very important factor in composite. In this paper, a reasonable theoretical model will be founded on the basis of the experimental analysis. By the axi symmetrical and three dimensional finite element method, the effects of interfacial performance on the mechanical behavior of short fiber reinforced metal matrix composites are studied systematically and deeply. The effects of interfacial characteristics on such aspects as stress transfer, modulus, stress strain curve and fracture mechanism are discussed. As a result, the change of interfacial performance will influence stress transfer, and thus change the modulus, stress strain curve and fracture mechanism of the composite. The interface controlling is a key factor in the design of composites.
Interface is a very important factor in composite. In this paper, a reasonable theoretical model will be founded on the basis of the experimental analysis. By the axi symmetrical and three dimensional finite element method, the effects of interfacial performance on the mechanical behavior of short fiber reinforced metal matrix composites are studied systematically and deeply. The effects of interfacial characteristics on such aspects as stress transfer, modulus, stress strain curve and fracture mechanism are discussed. As a result, the change of interfacial performance will influence stress transfer, and thus change the modulus, stress strain curve and fracture mechanism of the composite. The interface controlling is a key factor in the design of composites.
1999, 16(1): 41-44.
Abstract:
A method of fabricating glass fiber/epoxy matrix composites with low sectional electrion and dielectric loss has been introduced.The composite was fabricated by using the special equipment and process and tested by using the instruments of sectional electrion and dielectric loss bridge,all made in German,in accordance with GB7354-87 and GB1408-76 respectively.The results show that the solidified composite has properties of low sectional electrion(less than 2pc)and low dielectric loss tangent(less than 0.01)and the chief reasons of successful experiment have been also discussed.At present,this method has been used in production.
A method of fabricating glass fiber/epoxy matrix composites with low sectional electrion and dielectric loss has been introduced.The composite was fabricated by using the special equipment and process and tested by using the instruments of sectional electrion and dielectric loss bridge,all made in German,in accordance with GB7354-87 and GB1408-76 respectively.The results show that the solidified composite has properties of low sectional electrion(less than 2pc)and low dielectric loss tangent(less than 0.01)and the chief reasons of successful experiment have been also discussed.At present,this method has been used in production.
1999, 16(1): 45-51.
Abstract:
The experiments on Kevlar49 fibre bundles under quasi static tension and tensile impact were performed in MTS810 and Bar Bar Tensile Impact Apparatus, respectively. The stress strain curves of Kevlar49 fibre bundles were obtained at strain rates ranging from 10-4 /s to 103/s. The test results show that the mechanical behavior of Kevlar49 fibre bundles is rate dependent. Compared with glass fibre bundles, the rate sensitive degree of Kevlar49 fibre bundles is higher in the quasi static loading region, while it is less great in the high rate loading region.
The experiments on Kevlar49 fibre bundles under quasi static tension and tensile impact were performed in MTS810 and Bar Bar Tensile Impact Apparatus, respectively. The stress strain curves of Kevlar49 fibre bundles were obtained at strain rates ranging from 10-4 /s to 103/s. The test results show that the mechanical behavior of Kevlar49 fibre bundles is rate dependent. Compared with glass fibre bundles, the rate sensitive degree of Kevlar49 fibre bundles is higher in the quasi static loading region, while it is less great in the high rate loading region.
1999, 16(1): 52-57.
Abstract:
The kinetic parameters of two kinds of latent (epoxy resin) systems were discussed. The results indicate that an ideal latent resin system should possess higher reactive activation energy ( E a ) and frequency factor ( A ), or possess a variable reactive activation energy, that is, the resin system should possess a higher activation energy at room temperature and a lower one at elevated temperature.
The kinetic parameters of two kinds of latent (epoxy resin) systems were discussed. The results indicate that an ideal latent resin system should possess higher reactive activation energy ( E a ) and frequency factor ( A ), or possess a variable reactive activation energy, that is, the resin system should possess a higher activation energy at room temperature and a lower one at elevated temperature.
1999, 16(1): 58-62.
Abstract:
In this paper, a BMI type adhesive is introduced, which could be cured at 300℃ by traditional technology. It has good heat resistant properties and good shear strength at 300℃ and 400℃. It can be applied to adhere aluminium alloy or composite material, and can be used in aerospace industry as composite matrix resin to make the aircraft work correctly.
In this paper, a BMI type adhesive is introduced, which could be cured at 300℃ by traditional technology. It has good heat resistant properties and good shear strength at 300℃ and 400℃. It can be applied to adhere aluminium alloy or composite material, and can be used in aerospace industry as composite matrix resin to make the aircraft work correctly.
1999, 16(1): 63-66.
Abstract:
The effect of PTFE with different content on the property of composite material PI/PTFE is discussed in this paper. The results show that the addition of PTFE can improve the friction and wear property of PI effectively; when the content of PTFE is about 10～20%, the friction coefficient of PI decreases apparently. Co wear property mainly includes abrasive wear and adhesive wear. The results show that when the content of PTFE is 20%, the comprehensive property of composite material is the best.
The effect of PTFE with different content on the property of composite material PI/PTFE is discussed in this paper. The results show that the addition of PTFE can improve the friction and wear property of PI effectively; when the content of PTFE is about 10～20%, the friction coefficient of PI decreases apparently. Co wear property mainly includes abrasive wear and adhesive wear. The results show that when the content of PTFE is 20%, the comprehensive property of composite material is the best.
1999, 16(1): 67-71.
Abstract:
The weak interfacial strength is the important factor influencing the mechanical performance of aramid/epoxy composites. In this paper, the ultrasonic technique is applied to increase the impregnation of the resin during resin impregnating aramid fiber, which improves the interfacial properties of the composites. The optimal parameter of treatment is studied, emphasizing on the research of the effect of the ultrasonic treatment on the mechanical performance of composites.
The weak interfacial strength is the important factor influencing the mechanical performance of aramid/epoxy composites. In this paper, the ultrasonic technique is applied to increase the impregnation of the resin during resin impregnating aramid fiber, which improves the interfacial properties of the composites. The optimal parameter of treatment is studied, emphasizing on the research of the effect of the ultrasonic treatment on the mechanical performance of composites.
1999, 16(1): 72-76.
Abstract:
Pure bend sandwich beam specimen plays an important part in evaluating the fracture resistance of interface. The explicit solution of the strain energy release rate of crack propagation along the pure bend sandwich beam specimen has been deduced in the paper by use of the superposition principle of the energy and section inversion method. Based on the critical load of crack propagation along the interface through the testing measurement, the fracture toughness of four point bending Si3N4/Al/Si3N4 specimens along Si3N 4/Al diffusion joining interface has been obtained by using the explicit solution.
Pure bend sandwich beam specimen plays an important part in evaluating the fracture resistance of interface. The explicit solution of the strain energy release rate of crack propagation along the pure bend sandwich beam specimen has been deduced in the paper by use of the superposition principle of the energy and section inversion method. Based on the critical load of crack propagation along the interface through the testing measurement, the fracture toughness of four point bending Si3N4/Al/Si3N4 specimens along Si3N 4/Al diffusion joining interface has been obtained by using the explicit solution.
1999, 16(1): 77-80.
Abstract:
Because of the merits of optical fiber sensor comparing to other sensors, it is especially adapted to monitor the functions of composites and its varying with surroundings when embedded into composites during production, this technology has developed with the study of smart materials and structures. This paper analyzed the relationship between the varying of optical phase in the fiber and strain induced into by load or change of surroundings of composites using the results of weak wave guide theory; the special case of single mode Corning optical fiber has shown the sensitivity of optical phase changing to strain; meanwhile experimental results were provided to prove the theory, and errors were also analyzed.
Because of the merits of optical fiber sensor comparing to other sensors, it is especially adapted to monitor the functions of composites and its varying with surroundings when embedded into composites during production, this technology has developed with the study of smart materials and structures. This paper analyzed the relationship between the varying of optical phase in the fiber and strain induced into by load or change of surroundings of composites using the results of weak wave guide theory; the special case of single mode Corning optical fiber has shown the sensitivity of optical phase changing to strain; meanwhile experimental results were provided to prove the theory, and errors were also analyzed.
1999, 16(1): 81-86.
Abstract:
This paper discusses the optimum design for laminated plates which can bear the internal pressure and simultaneously the one dimensional and unstable temperature field in the radial direction. The thickness of laminated plates is considered as the object function and the winding angle as the design variable. A calculated example is given, in which the optimum design data are provided for the filament wound pressure vessel under internal pressure and every moment in the whole process of the sudden inner medium temperature change to stable temperature field.
This paper discusses the optimum design for laminated plates which can bear the internal pressure and simultaneously the one dimensional and unstable temperature field in the radial direction. The thickness of laminated plates is considered as the object function and the winding angle as the design variable. A calculated example is given, in which the optimum design data are provided for the filament wound pressure vessel under internal pressure and every moment in the whole process of the sudden inner medium temperature change to stable temperature field.
1999, 16(1): 87-92.
Abstract:
The macro and micro mechanical behavior of smart composite materials reinforced by SMA was described by an analytical and numerical approach. The constitutive relations of the composite and dynamic equations of the SMA transformation were predicted. The numerical results in the uniaxial loading case illustrate the transformation mechanism of SMA under elastic matrix constraint and shape memory effect of the composites. It is shown that properties of the composite are considerably influenced by shape memory effect of SMA as well as the constituent properties, fraction and environment variable such as temperature.
The macro and micro mechanical behavior of smart composite materials reinforced by SMA was described by an analytical and numerical approach. The constitutive relations of the composite and dynamic equations of the SMA transformation were predicted. The numerical results in the uniaxial loading case illustrate the transformation mechanism of SMA under elastic matrix constraint and shape memory effect of the composites. It is shown that properties of the composite are considerably influenced by shape memory effect of SMA as well as the constituent properties, fraction and environment variable such as temperature.
1999, 16(1): 93-98.
Abstract:
On the basis of Zweben's shear lag assumptions, this paper proposes a modified shear lag model to study the micro stress redistributions induced by the interaction of the failures of the low elongation layer, interlaminated interface and some fibers in high elongation layers in interlaminated hybrid composites and to discuss the influence of interfacial failure on the stress concentration factors in high elongation fibers, and provides the theoretical basis for the micro statistical analysis for the ultimate tensile failure of interlaminated hybrid composites.
On the basis of Zweben's shear lag assumptions, this paper proposes a modified shear lag model to study the micro stress redistributions induced by the interaction of the failures of the low elongation layer, interlaminated interface and some fibers in high elongation layers in interlaminated hybrid composites and to discuss the influence of interfacial failure on the stress concentration factors in high elongation fibers, and provides the theoretical basis for the micro statistical analysis for the ultimate tensile failure of interlaminated hybrid composites.
1999, 16(1): 99-104.
Abstract:
This paper proposes a microscopic statistical theory for the ultimate tensile failure of unidirectionally interlaminated hybrid composites with interply interface failure, based on the random critical core theory in conjunction with the results of the stress concentration which are obtained by a shear lag model. A function of the strength distribution and a failure criterion with the effect of interfacial shear strength are derived and a relationship between the ultimate tensile strength and interfacial shear strength is obtained. The results show that the ultimate strength of hybrid composites, interfacial shear strength and hybrid ratio have an optimal match relation, and that the present failure strains are relatively close to the existing experimental value.
This paper proposes a microscopic statistical theory for the ultimate tensile failure of unidirectionally interlaminated hybrid composites with interply interface failure, based on the random critical core theory in conjunction with the results of the stress concentration which are obtained by a shear lag model. A function of the strength distribution and a failure criterion with the effect of interfacial shear strength are derived and a relationship between the ultimate tensile strength and interfacial shear strength is obtained. The results show that the ultimate strength of hybrid composites, interfacial shear strength and hybrid ratio have an optimal match relation, and that the present failure strains are relatively close to the existing experimental value.
1999, 16(1): 105-110.
Abstract:
The authors review some research results of ceramic matrix nanocomposites both at home and abroad in recent years, including mechanical properties and their factors, uniform dispersing of nano particles and mixed with ceramic matrix, shape forming of the materials, its structure, the mechanism of strengthening and toughening.
The authors review some research results of ceramic matrix nanocomposites both at home and abroad in recent years, including mechanical properties and their factors, uniform dispersing of nano particles and mixed with ceramic matrix, shape forming of the materials, its structure, the mechanism of strengthening and toughening.
1999, 16(1): 111-116.
Abstract:
TiN/Ti composite material was prepared with high power CO2 laser focused on the surface of titanium alloy in nitrogen ambient. The microstructure, composition and micro hardness of the material were analyzed with SEM, XRD, EP (electron probe) and Micro hardometer. The results show that nitride layers consist of TiN and α-Ti phase. TiN dendrites distribute in nitride layer homogeneously. The nitride level and maximum micro hardness increase with reaction time increasing. The cross section micro hardness of the material changes continuously. The higher laser energy density, the deeper nitride layers. The depth of nitride layer and the surface micro hardness are 350μm and Hv1600 as the laser power density is of 3.35×105 W·cm-2 , scanning velocity of 300mm·min -1 , and nitrogen pressure of 0.35MPa respectively.
TiN/Ti composite material was prepared with high power CO2 laser focused on the surface of titanium alloy in nitrogen ambient. The microstructure, composition and micro hardness of the material were analyzed with SEM, XRD, EP (electron probe) and Micro hardometer. The results show that nitride layers consist of TiN and α-Ti phase. TiN dendrites distribute in nitride layer homogeneously. The nitride level and maximum micro hardness increase with reaction time increasing. The cross section micro hardness of the material changes continuously. The higher laser energy density, the deeper nitride layers. The depth of nitride layer and the surface micro hardness are 350μm and Hv1600 as the laser power density is of 3.35×105 W·cm-2 , scanning velocity of 300mm·min -1 , and nitrogen pressure of 0.35MPa respectively.
1999, 16(1): 117-124.
Abstract:
This paper is concerned with the determination of the effective elastic behavior of two damaged composites. The changes of elastic moduli are studied in different particle shapes when the partially debonded and completely debonded particles coexist. For the convenience of application, all results are provided in explicit forms.
This paper is concerned with the determination of the effective elastic behavior of two damaged composites. The changes of elastic moduli are studied in different particle shapes when the partially debonded and completely debonded particles coexist. For the convenience of application, all results are provided in explicit forms.
1999, 16(1): 125-130.
Abstract:
The problem considered here is the response of a substrate/coating structure subjected to dynamic heating. By utilizing Laplace transform and Fourier transform technique, the general solutions for temperature fields and stress fields are derived. The dynamic thermal stresses are presented under different heating rates for various substrate and coating thicknesses. The possible failure mode and the optimized coating thickness are analyzed.
The problem considered here is the response of a substrate/coating structure subjected to dynamic heating. By utilizing Laplace transform and Fourier transform technique, the general solutions for temperature fields and stress fields are derived. The dynamic thermal stresses are presented under different heating rates for various substrate and coating thicknesses. The possible failure mode and the optimized coating thickness are analyzed.
1999, 16(1): 131-136.
Abstract:
The Resin Transfer Molding (RTM) is becoming an efficient production method for advanced fibre composite parts. The molding filling process, a very important phase of two dimensional molds, where heterogeneous reinforced material is laid, is digitally simulated. Calculated results are compared with experimental observation.
The Resin Transfer Molding (RTM) is becoming an efficient production method for advanced fibre composite parts. The molding filling process, a very important phase of two dimensional molds, where heterogeneous reinforced material is laid, is digitally simulated. Calculated results are compared with experimental observation.
1999, 16(1): 137-141.
Abstract:
Because the conventional approach to fracture analysis is not capable of coping with the degree of complexity required for composite materials, a proper fracture mechanics analysis method for composite material is necessitated. This paper proposes a macro micro model which divides a composite material containing a flaw into local and global regions and deals with the problem in each region by different methods. By means of the finite element analysis, more useful results are obtained.
Because the conventional approach to fracture analysis is not capable of coping with the degree of complexity required for composite materials, a proper fracture mechanics analysis method for composite material is necessitated. This paper proposes a macro micro model which divides a composite material containing a flaw into local and global regions and deals with the problem in each region by different methods. By means of the finite element analysis, more useful results are obtained.
1999, 16(1): 142-148.
Abstract:
Forming principle and parameter determination of Jones Nelson Morgan Model are expounded. The nonlinear constitutive relations of filament wound composites are studied with J N M model. The large deformation formulae of filament wound case (FWC) are derived, and the finite element model of the FWC is established. The large deformation of the FWC under internal pressure loads is analyzed. Combining material nonlinearity with large deformation, the computational results of the FWC have been obtained. The results are better than those of considering only large deformation, and it is in good agreement with test data.
Forming principle and parameter determination of Jones Nelson Morgan Model are expounded. The nonlinear constitutive relations of filament wound composites are studied with J N M model. The large deformation formulae of filament wound case (FWC) are derived, and the finite element model of the FWC is established. The large deformation of the FWC under internal pressure loads is analyzed. Combining material nonlinearity with large deformation, the computational results of the FWC have been obtained. The results are better than those of considering only large deformation, and it is in good agreement with test data.
1999, 16(1): 149-158.
Abstract:
This paper is concerned with the buckling load analysis of laminates with a pre existing delamination, using the finite element method based on the Mindlin plate theory. To obtain the physically possible buckling mode, i.e. to avoid the penetration between two delaminated layers, some artificial springs are introduced into the contacting area. Moreover, the formulations for calculating the stiffness parameters of these springs and iterative process for contact analysis are presented. The global structural stiffness matrix can be modified by employing these springs and the penetration between two delaminated layers can be overcome effectively. Numerical results demonstrate the effectiveness of this method and the importance of the contact analysis in the buckling analysis. The effects of various sizes, shapes and positions of the delamination and the fiber angle of delaminated layer on the buckling load are also investigated.
This paper is concerned with the buckling load analysis of laminates with a pre existing delamination, using the finite element method based on the Mindlin plate theory. To obtain the physically possible buckling mode, i.e. to avoid the penetration between two delaminated layers, some artificial springs are introduced into the contacting area. Moreover, the formulations for calculating the stiffness parameters of these springs and iterative process for contact analysis are presented. The global structural stiffness matrix can be modified by employing these springs and the penetration between two delaminated layers can be overcome effectively. Numerical results demonstrate the effectiveness of this method and the importance of the contact analysis in the buckling analysis. The effects of various sizes, shapes and positions of the delamination and the fiber angle of delaminated layer on the buckling load are also investigated.
1999, 16(1): 159-164.
Abstract:
In this paper, two real crystals of Ag and Ni were selected. The following two conditions were studied by the Molecular Dynamics (MD) simulation method: the first one is that the two bulk metals are too far to form interface; the second one is that they form interface. By simulating the static relaxation and dynamics bending process, the differences between the two conditions were compared. The results show that the existence of interface affects greatly, sometimes even controls the mechanical properties of the composite.
In this paper, two real crystals of Ag and Ni were selected. The following two conditions were studied by the Molecular Dynamics (MD) simulation method: the first one is that the two bulk metals are too far to form interface; the second one is that they form interface. By simulating the static relaxation and dynamics bending process, the differences between the two conditions were compared. The results show that the existence of interface affects greatly, sometimes even controls the mechanical properties of the composite.
