1996 Vol. 13, No. 3
EFFECT OF COUPLING AGENTS ON DIELECTRICAL PROPERTIES OF GLASS FIBER/EPOXY MATRIX COMPOSITE INTERFACE
1996, 13(3): 1-4.
Abstract:
Influence of five kinds of coupling agents on the wetting property of glass fiber and on the dielectrical property of glass fiber/epoxy composite interface was studied. The results show that after glass fiber being treated with coupling agents and activation energy of glass fiber for wetting being decreased, the reaction activity and wettability between glass fiber and epoxy resin matrix can be improved. A good interface adhesion of glass fiber/epoxy results in an improvement of dielectrical propertys of glass fiber/epoxy composite interface. Its improvement range depends on the polarity and chemical structure of the coupling agents.
Influence of five kinds of coupling agents on the wetting property of glass fiber and on the dielectrical property of glass fiber/epoxy composite interface was studied. The results show that after glass fiber being treated with coupling agents and activation energy of glass fiber for wetting being decreased, the reaction activity and wettability between glass fiber and epoxy resin matrix can be improved. A good interface adhesion of glass fiber/epoxy results in an improvement of dielectrical propertys of glass fiber/epoxy composite interface. Its improvement range depends on the polarity and chemical structure of the coupling agents.
1996, 13(3): 5-11.
Abstract:
Experimental results show that the surface chemical modification, with chemical reaction by the polyfunctional epoxide(Ag80) or 3-chloropropene into the skin layer of the aramid fiber(Kevlar 49) increases noticeably the moisture-thermo-esistant properties of the aramid fiber and of the interfacial adhesion between aramid fiber and X4502 resin.
Experimental results show that the surface chemical modification, with chemical reaction by the polyfunctional epoxide(Ag80) or 3-chloropropene into the skin layer of the aramid fiber(Kevlar 49) increases noticeably the moisture-thermo-esistant properties of the aramid fiber and of the interfacial adhesion between aramid fiber and X4502 resin.
1996, 13(3): 12-20.
Abstract:
The HDPE/glass spheres and the HDPE/CaCO3 filled systems were taken as the investigated models, and the influence of the interfacial adhesion, the filler content and its particle size on the properties of filled HDPE composites and the crystalline morphology of their matrices was investigated by using scanning electron microscopy, infrared spectra meter, polarizing microscope, small angle light scattering, material universal testing machine, etc.The results show that in the higher interfacial bonding strength condition, the produced interfacial stress from the contraction of matrix in the composite injection molding can disturb the spherulites grrowving surroundings in the matrix,strain-induces the crystallization of matrix in the area surrounding the filler, and leads to forming the extended-chain crystal structure. Meanwhile, it was found that the properties of filled HDPE composites were also obviously changed, and that the interfacial bonding strength was an important factor in producing the strain-induced crystallization, controlling the multiphase crystallization and modifying the properties of the filled composites.
The HDPE/glass spheres and the HDPE/CaCO3 filled systems were taken as the investigated models, and the influence of the interfacial adhesion, the filler content and its particle size on the properties of filled HDPE composites and the crystalline morphology of their matrices was investigated by using scanning electron microscopy, infrared spectra meter, polarizing microscope, small angle light scattering, material universal testing machine, etc.The results show that in the higher interfacial bonding strength condition, the produced interfacial stress from the contraction of matrix in the composite injection molding can disturb the spherulites grrowving surroundings in the matrix,strain-induces the crystallization of matrix in the area surrounding the filler, and leads to forming the extended-chain crystal structure. Meanwhile, it was found that the properties of filled HDPE composites were also obviously changed, and that the interfacial bonding strength was an important factor in producing the strain-induced crystallization, controlling the multiphase crystallization and modifying the properties of the filled composites.
1996, 13(3): 21-26.
Abstract:
A micromechanics model of a single carbon fiber embedded in an epoxy system containing an elastoplastic interlayer is described. The finite element method is used to study the effect of thickness and modulus of the interlayer on the stress transfer in this composite system after thefiber breakage. Analysis results indicate that the optimum interlayer can decrease the shear stress concentration and improve the load carrying capabilities of the broken fiber under different interfacial bonding conditions.
A micromechanics model of a single carbon fiber embedded in an epoxy system containing an elastoplastic interlayer is described. The finite element method is used to study the effect of thickness and modulus of the interlayer on the stress transfer in this composite system after thefiber breakage. Analysis results indicate that the optimum interlayer can decrease the shear stress concentration and improve the load carrying capabilities of the broken fiber under different interfacial bonding conditions.
1996, 13(3): 27-32.
Abstract:
Al2O3/TiB2/SiCw composite was fabricated by hot pressing with SiC whiskers and TiB2 as toughening phase. The mechanical properties and microstructure as well as toughening mechanisms were investigated. Results showed that the sintering temperature and the temperature holding time should be increased as the SiCw content increased. Significant improvement in fracture toughness will be obtained for the Al2O3/TiB2/SiCw composite, in comparison with Al2O3/TiB2 composite. Toughening mechanisms in the composite are mainly pullout of SiC whiskers crack deflection by TiB2 grains and whiskers bridging.Considerable improvement in fracture toughness at high temperature was observed for the composite.
Al2O3/TiB2/SiCw composite was fabricated by hot pressing with SiC whiskers and TiB2 as toughening phase. The mechanical properties and microstructure as well as toughening mechanisms were investigated. Results showed that the sintering temperature and the temperature holding time should be increased as the SiCw content increased. Significant improvement in fracture toughness will be obtained for the Al2O3/TiB2/SiCw composite, in comparison with Al2O3/TiB2 composite. Toughening mechanisms in the composite are mainly pullout of SiC whiskers crack deflection by TiB2 grains and whiskers bridging.Considerable improvement in fracture toughness at high temperature was observed for the composite.
1996, 13(3): 33-37.
Abstract:
In this paper, the research has been given on the double weldable ceramic cutting tool by means of the acoustic micro scope.At the same time,the analysis has been made about the affecting factors on the materials boundary and its uniformity.It has not been found that there is a uniformity between the boundary of the two kinds of materials.A new way to improve the materials,designing has been presented.
In this paper, the research has been given on the double weldable ceramic cutting tool by means of the acoustic micro scope.At the same time,the analysis has been made about the affecting factors on the materials boundary and its uniformity.It has not been found that there is a uniformity between the boundary of the two kinds of materials.A new way to improve the materials,designing has been presented.
1996, 13(3): 38-42.
Abstract:
Composite ceramics of cubic or tetrahedral ZrO2 phase on the microstructure, phase composition,bending strength,fracture toughness as well as ionic resistivity were tested and the mechanisms were discussed.The results showed that small amount of ZrO2, especially the partial-stabilized t-phase which can transform to m-phase under stress,could effectively improve the properties of single phase β"-Al2O3 ceramics.
Composite ceramics of cubic or tetrahedral ZrO2 phase on the microstructure, phase composition,bending strength,fracture toughness as well as ionic resistivity were tested and the mechanisms were discussed.The results showed that small amount of ZrO2, especially the partial-stabilized t-phase which can transform to m-phase under stress,could effectively improve the properties of single phase β"-Al2O3 ceramics.
1996, 13(3): 43-47.
Abstract:
This paper deals with high-tensile-strength C/Mg composite with b>1000M Pa fabricated by vacuum casting.T 300 fibers coated with C-Si-O gradient coatings are aligned in casting moulds,and then infiltrated with molten ZM-5 alloy under vacuum 4000Pa.The tensile strength of specimens containing fibers of 0.35 volume fraction reaches up to 1050M Pa.The effects of C-Si-O gradient coating on tensile strength of composites are mainly discussed.
This paper deals with high-tensile-strength C/Mg composite with b>1000M Pa fabricated by vacuum casting.T 300 fibers coated with C-Si-O gradient coatings are aligned in casting moulds,and then infiltrated with molten ZM-5 alloy under vacuum 4000Pa.The tensile strength of specimens containing fibers of 0.35 volume fraction reaches up to 1050M Pa.The effects of C-Si-O gradient coating on tensile strength of composites are mainly discussed.
1996, 13(3): 48-52.
Abstract:
Abstract The coefficient of thermal expansion and thermal conductivity of the squeeze casting SiCw/Al composites were measured and analyzed. The experimental results showed that with the increasing temperature, the coefficients of thermal expansion of both SiCw/Al composite and aluminium alloy are increased. The coefficient of thermal expansion of the T 6 state SiCw/Al composite is lower than that of the as-cast composite, and the deep-cooled(-196℃) SiCw/Al composite shows the lowest coefficient of thermal expansion. It is also found that with the increase of the whisker volumefraction, the coefficient of thermal expanlion of the SiCw/Al composite is obviously decreased, and the thermal conductivity of the composite is also decreased.
Abstract The coefficient of thermal expansion and thermal conductivity of the squeeze casting SiCw/Al composites were measured and analyzed. The experimental results showed that with the increasing temperature, the coefficients of thermal expansion of both SiCw/Al composite and aluminium alloy are increased. The coefficient of thermal expansion of the T 6 state SiCw/Al composite is lower than that of the as-cast composite, and the deep-cooled(-196℃) SiCw/Al composite shows the lowest coefficient of thermal expansion. It is also found that with the increase of the whisker volumefraction, the coefficient of thermal expanlion of the SiCw/Al composite is obviously decreased, and the thermal conductivity of the composite is also decreased.
1996, 13(3): 53-59.
Abstract:
Review is given here on some aspects of recent developments in the structure analysis, principles and models of Graphite Intercalation Compounds(GICs),and also presented are some of the modern analysis technics.
Review is given here on some aspects of recent developments in the structure analysis, principles and models of Graphite Intercalation Compounds(GICs),and also presented are some of the modern analysis technics.
1996, 13(3): 60-64.
Abstract:
The cutting surface quality of the squeeze casting ZA22/Al2O3 composites was researched with a hard metal alloy cutter.The results show that the surface quality of the composites is better than that of ZA22 alloy under the same parameters.Higher cutting velocity,lower amount of feed and cutting thickness can improve the surface quality of the composites.With the increase of the volume fraction of Al2O3 fibers, the cutting surface roughness of the composites is lowered.
The cutting surface quality of the squeeze casting ZA22/Al2O3 composites was researched with a hard metal alloy cutter.The results show that the surface quality of the composites is better than that of ZA22 alloy under the same parameters.Higher cutting velocity,lower amount of feed and cutting thickness can improve the surface quality of the composites.With the increase of the volume fraction of Al2O3 fibers, the cutting surface roughness of the composites is lowered.
1996, 13(3): 65-70.
Abstract:
The mode Ⅱ delamination of a glass fiber reinforced epoxy composite was studied by both static and fatigue tests.The ultrasound technic was used to measure the elastic moduli of studied composites.The measured results are proved to agree well with that obtained with mixed rulers.ENF specimens were used to obtain GⅡC and the relationship between da/dN and ΔGⅡ.By theoretical analysis,the GⅡ value calculated with classical beam theories is 3% lower than the exact value.The observation under SEM shows that different fracture modes can result in different microscopic aspects of rupture surface.
The mode Ⅱ delamination of a glass fiber reinforced epoxy composite was studied by both static and fatigue tests.The ultrasound technic was used to measure the elastic moduli of studied composites.The measured results are proved to agree well with that obtained with mixed rulers.ENF specimens were used to obtain GⅡC and the relationship between da/dN and ΔGⅡ.By theoretical analysis,the GⅡ value calculated with classical beam theories is 3% lower than the exact value.The observation under SEM shows that different fracture modes can result in different microscopic aspects of rupture surface.
INFLUENCE OF THREE DIMENSIONAL AND MULTIDIRECTIONAL BRAID STRUCTURES ON THE PROPERTIES OF COMPOSITES
1996, 13(3): 71-75.
Abstract:
In this paper a study was made on the properties of three dimensional and multidirectional braided composites with and without axial reinforcement under three braid stuctures 1×1, 1×2 and 1×3. The tensile strength and modulus, flexural strength and modulus of the composites were tested and analyzed. The results show that the three dimensional braided composite has good behaviour and the braid structures have a great influence on it. The fiber apparent angle and fiber volume fraction are two important factors in the improvement of properties. By means of adding in axially non-braiding reinforced fibers, the properties of braided composites including tension and bending have been improved considerably.
In this paper a study was made on the properties of three dimensional and multidirectional braided composites with and without axial reinforcement under three braid stuctures 1×1, 1×2 and 1×3. The tensile strength and modulus, flexural strength and modulus of the composites were tested and analyzed. The results show that the three dimensional braided composite has good behaviour and the braid structures have a great influence on it. The fiber apparent angle and fiber volume fraction are two important factors in the improvement of properties. By means of adding in axially non-braiding reinforced fibers, the properties of braided composites including tension and bending have been improved considerably.
1996, 13(3): 76-80.
Abstract:
The 3-D braiding technique for composites is a new textile technology developed in the United States in the 80 s.The composite of 3-D braided structure is a new kind of composites.Its shock-damage-resistant property,mechanical property and fire-resistant property are fairly good.In this paper,the unit cell geometry of the 3-D braided structure of composites was discussed and the relationships of the structural parameters were established.
The 3-D braiding technique for composites is a new textile technology developed in the United States in the 80 s.The composite of 3-D braided structure is a new kind of composites.Its shock-damage-resistant property,mechanical property and fire-resistant property are fairly good.In this paper,the unit cell geometry of the 3-D braided structure of composites was discussed and the relationships of the structural parameters were established.
MECHANICAL CHARACTERIZATION AND PARAMETER DETERMINATION OF THE FIBER REINFORCED COMPOSITE INTERPHASE
1996, 13(3): 81-86.
Abstract:
A micromechanics analysis on the interphase of fiber reinforced polymer compolite is presented. The representative volume element of coaxial combined cylinder model is adopted. Four compliance parameters Sij(i,j=1, 2) are used do characterize the interphase effect, which generalizes Hashin's two}arameter interface mode. A relation between these parameters and macro behaviour of composite is established based on the equivalent principle of a multiphase body. By experiment,interfacial parameters are first determined for two kinds of composites:T300/ST 350 and Glass/Polyester.
A micromechanics analysis on the interphase of fiber reinforced polymer compolite is presented. The representative volume element of coaxial combined cylinder model is adopted. Four compliance parameters Sij(i,j=1, 2) are used do characterize the interphase effect, which generalizes Hashin's two}arameter interface mode. A relation between these parameters and macro behaviour of composite is established based on the equivalent principle of a multiphase body. By experiment,interfacial parameters are first determined for two kinds of composites:T300/ST 350 and Glass/Polyester.
1996, 13(3): 87-92.
Abstract:
As laminated composite plates have relatively low transverse shear modulus, Kirchhoff theory has been proved to be inadequate for calculating the eigenvalues and their sensitivity in laminated plates.A first-order shear deformation theory is used for symmetrically laminated plates in the paper. The orientation angle of fibres, the material parameter and the vertical distance from the middle plane of the laminated plates of the upper surface of each ply are treated as design variables, and the sensitivity of eigenvalues for the symmetrically laminated plates is studied.
As laminated composite plates have relatively low transverse shear modulus, Kirchhoff theory has been proved to be inadequate for calculating the eigenvalues and their sensitivity in laminated plates.A first-order shear deformation theory is used for symmetrically laminated plates in the paper. The orientation angle of fibres, the material parameter and the vertical distance from the middle plane of the laminated plates of the upper surface of each ply are treated as design variables, and the sensitivity of eigenvalues for the symmetrically laminated plates is studied.
1996, 13(3): 93-99.
Abstract:
A combined method of experiment-boundary element is suggested for stress analysis in photo-orthotropic-elasticity, and a corresponding program system BEMSC is developed. One item experimend ata(isochromatic line) is only needed by applying the method. It is also applicable to the problem of photo-orthotropic-elastic analysis for the modd m at erials with residual stresses. An example of stress analysis is given in photo-orthotropic-elasticity.
A combined method of experiment-boundary element is suggested for stress analysis in photo-orthotropic-elasticity, and a corresponding program system BEMSC is developed. One item experimend ata(isochromatic line) is only needed by applying the method. It is also applicable to the problem of photo-orthotropic-elastic analysis for the modd m at erials with residual stresses. An example of stress analysis is given in photo-orthotropic-elasticity.
1996, 13(3): 100-104.
Abstract:
The fluidstructure interaction vibration of stiffened structures is studied by using the method combining the finite element(FEM)with the boundary element(BEM).During the calculation, the damp stiffness of the structure is considered. A modified RITZ vector method and Newmark direct integral method are employed to overcome the difficulties of the numerical analysis caused by the unsymmetrical added mass.For numerical examples, the vibration and response of the composite cantilever plates and stiffened structures are analysed. Moreover, the effect of underwater explosion on a composite shiphull is liven.
The fluidstructure interaction vibration of stiffened structures is studied by using the method combining the finite element(FEM)with the boundary element(BEM).During the calculation, the damp stiffness of the structure is considered. A modified RITZ vector method and Newmark direct integral method are employed to overcome the difficulties of the numerical analysis caused by the unsymmetrical added mass.For numerical examples, the vibration and response of the composite cantilever plates and stiffened structures are analysed. Moreover, the effect of underwater explosion on a composite shiphull is liven.
1996, 13(3): 105-110.
Abstract:
A discrete-layer shear deformation theory is used to analyse the free vibration of laminated shells.The theory adopts an assumption that the transverse shear strains across any two layers are linearly dependent on each other. The theory contains the same dependent variables as the first-order shear deformation theory, but the set of governing differential equations is of twelfth order. No shear correction factors are required. Free vibrations of a short circular cylindrical shell and two shallow shells are calculated. The numerical results are compared with the classical lamination theory first-order shear deformation theory and other shear deformation theory solutions.free vibration analysis, laminated shells, transverse shear effects, discrete-layer shear deformation theory
A discrete-layer shear deformation theory is used to analyse the free vibration of laminated shells.The theory adopts an assumption that the transverse shear strains across any two layers are linearly dependent on each other. The theory contains the same dependent variables as the first-order shear deformation theory, but the set of governing differential equations is of twelfth order. No shear correction factors are required. Free vibrations of a short circular cylindrical shell and two shallow shells are calculated. The numerical results are compared with the classical lamination theory first-order shear deformation theory and other shear deformation theory solutions.free vibration analysis, laminated shells, transverse shear effects, discrete-layer shear deformation theory
1996, 13(3): 111-116.
Abstract:
It had been proved experimentally that Graphite(AS4)/Epoxy(3501-6) unbalanced laminates with inplane negative Poisson's ratio have higher fracture toughness and notch fracture strength. In this paper, a study is made of the near-tip stress fields for crack and the stress intensity factors in unbalanced laminates with inplane negative Poisson's ratio by the complex variable-variational method. The results obtained are compared with the results of halaneed lamlnates.Three layups, [0/15/75/15],0/25/65/25]s with negative Poisson's ratio and [0/60/90/-60]s with positive Poisson's ratio are analysed. Emphasis is put on research into the elations between principal stress's orientations and fiber's orientations as well as between stress intensity factors and fracture toughness. The calculation results show that these laminates with negative Poisson's ratio have higher notch fracture strength.
It had been proved experimentally that Graphite(AS4)/Epoxy(3501-6) unbalanced laminates with inplane negative Poisson's ratio have higher fracture toughness and notch fracture strength. In this paper, a study is made of the near-tip stress fields for crack and the stress intensity factors in unbalanced laminates with inplane negative Poisson's ratio by the complex variable-variational method. The results obtained are compared with the results of halaneed lamlnates.Three layups, [0/15/75/15],0/25/65/25]s with negative Poisson's ratio and [0/60/90/-60]s with positive Poisson's ratio are analysed. Emphasis is put on research into the elations between principal stress's orientations and fiber's orientations as well as between stress intensity factors and fracture toughness. The calculation results show that these laminates with negative Poisson's ratio have higher notch fracture strength.
1996, 13(3): 117-124.
Abstract:
Electrorheo logical(ER) fluids exhibit changes in rheological behavior in the presence of an electric field. This paper provides a summary of the current state of electrorhe-ological fluids application and development.A critique of proposed mechanisms for the ER phenomenon, a description of basic material configurations used in controllable system components, and a discussion of controllable devices are presented. Meantime, for the double layer composite beam featuring eletrorheological fluids, the effect of electric field on the vibrational characteristics of beam is focused. The active controllable damper featuring electrorheological fluids is studied, and the vibrational characteristics of the damper are also evaluated when subjected to an external electric field.
Electrorheo logical(ER) fluids exhibit changes in rheological behavior in the presence of an electric field. This paper provides a summary of the current state of electrorhe-ological fluids application and development.A critique of proposed mechanisms for the ER phenomenon, a description of basic material configurations used in controllable system components, and a discussion of controllable devices are presented. Meantime, for the double layer composite beam featuring eletrorheological fluids, the effect of electric field on the vibrational characteristics of beam is focused. The active controllable damper featuring electrorheological fluids is studied, and the vibrational characteristics of the damper are also evaluated when subjected to an external electric field.
1996, 13(3): 125-128.
Abstract:
A new approach for analysis of laminated plates of bimodulus composite materials called Finite Layer Element Method(FLEM) is presented. The difficulty for selecting tenlion modulus or compression modulus in analysis of laminated plates of bimodulus composite materials is overcome by using FLE Method developed here. Compared with the Finite Layers Method, the accuracy of solutions is improved significantly. The present solutions are compared with the numerical results existing in the literature for special cases, and good agreement is obtained.
A new approach for analysis of laminated plates of bimodulus composite materials called Finite Layer Element Method(FLEM) is presented. The difficulty for selecting tenlion modulus or compression modulus in analysis of laminated plates of bimodulus composite materials is overcome by using FLE Method developed here. Compared with the Finite Layers Method, the accuracy of solutions is improved significantly. The present solutions are compared with the numerical results existing in the literature for special cases, and good agreement is obtained.
