2003 Vol. 20, No. 4
2003, 20(4): 1-4.
Abstract:
In this paper, the superplastic characteristics of the 15vol％SiC whisker reinforced Zn-22Al alloy composite, fabricated by low-pressure infiltration and solute-treatment after extrusion with the extrusion rate of 10∶1, were investigated. The composite exhibited a tensile elongation of 150% and a strain rate sensitivity value of about 0.33 at the initial strain rate of 6.67×10-2s-1 at 658K.
In this paper, the superplastic characteristics of the 15vol％SiC whisker reinforced Zn-22Al alloy composite, fabricated by low-pressure infiltration and solute-treatment after extrusion with the extrusion rate of 10∶1, were investigated. The composite exhibited a tensile elongation of 150% and a strain rate sensitivity value of about 0.33 at the initial strain rate of 6.67×10-2s-1 at 658K.
2003, 20(4): 5-9.
Abstract:
Alumina and carbon short fibers reinforced ZL109 aluminum alloy hybrid composites were fabricated by squeeze casting.The effects of the alumina volume fraction on dry sliding friction and wear properties of the hybrid composites with the fixed carbon fiber volume fraction 4 % were investigated.The results show that the carbon fiber is of self-lubricant in a certain degree,however,the friction coefficient of the hybrid composites improves due to addition of alumina fiber and increases with the increase of alumina fiber volume fraction.The transition load from mild wear to severe wear of the hybrid composites improves markedly because of the mutual effect of alumina and carbon short fibers and increases with the increase of alumina fiber volume fraction.There exists a critical value of alumina fiber volume fraction which influences the wear property of the hybrid composites with the lowest wear rate at the volume fraction of 12 % when the experimental load is below the transition load.Dominant wear mechanisms of composites are grooving wear and delamination during mild wear.Whereas dominant wear mechanisms of matrix and composites will be shifted to severe adhesion when the experimental load is above the transition load.
Alumina and carbon short fibers reinforced ZL109 aluminum alloy hybrid composites were fabricated by squeeze casting.The effects of the alumina volume fraction on dry sliding friction and wear properties of the hybrid composites with the fixed carbon fiber volume fraction 4 % were investigated.The results show that the carbon fiber is of self-lubricant in a certain degree,however,the friction coefficient of the hybrid composites improves due to addition of alumina fiber and increases with the increase of alumina fiber volume fraction.The transition load from mild wear to severe wear of the hybrid composites improves markedly because of the mutual effect of alumina and carbon short fibers and increases with the increase of alumina fiber volume fraction.There exists a critical value of alumina fiber volume fraction which influences the wear property of the hybrid composites with the lowest wear rate at the volume fraction of 12 % when the experimental load is below the transition load.Dominant wear mechanisms of composites are grooving wear and delamination during mild wear.Whereas dominant wear mechanisms of matrix and composites will be shifted to severe adhesion when the experimental load is above the transition load.
2003, 20(4): 10-13.
Abstract:
The microstructure and composition distribution of the iron-nickel alloy lined layer in a composite steel pipe produced by centrifugal-SHS process were investigated. The results showed that a martensitic transition region has been found between the iron-nickel layer and carbon steel matrix. A composition gradient of alloying elements exists in the iron-nickel alloy layer in the radial direction of the composite pipe. The alloying element contents in the lined layer are higher near the inner surface than near the outside surface. The intermetallic compounds AlNi3 and AlNi precipitate in the iron-nickel alloy.
The microstructure and composition distribution of the iron-nickel alloy lined layer in a composite steel pipe produced by centrifugal-SHS process were investigated. The results showed that a martensitic transition region has been found between the iron-nickel layer and carbon steel matrix. A composition gradient of alloying elements exists in the iron-nickel alloy layer in the radial direction of the composite pipe. The alloying element contents in the lined layer are higher near the inner surface than near the outside surface. The intermetallic compounds AlNi3 and AlNi precipitate in the iron-nickel alloy.
2003, 20(4): 14-17.
Abstract:
The possible equilibrium products and their compositions of a complex thermite reaction which was used for centrifugal-thermit process have been performed by means of the free-energy minimization method. The effects of the composition of thermit, preheating temperature and inert addition on the equilibrium composition, the heat of reaction and the adiabatic temperature of the system were investigated. It shows that apart from Al2O3,Fe,Cr,Ni, in the equilibrium products exist TiC,Cr7C3,CrN,AlNi,AlNi3,FeAl2O4,CaS and TiN. The intermetallics such as NiAl and Ni3Al in the equilibrium products increase with an increase in the aluminum content in the thermit. The CaO can act as desulphurizer. In addition, CaO decreases the adiabatic temperature of the system. The adiabatic temperature of the system increases with a rise in the preheating temperature.
The possible equilibrium products and their compositions of a complex thermite reaction which was used for centrifugal-thermit process have been performed by means of the free-energy minimization method. The effects of the composition of thermit, preheating temperature and inert addition on the equilibrium composition, the heat of reaction and the adiabatic temperature of the system were investigated. It shows that apart from Al2O3,Fe,Cr,Ni, in the equilibrium products exist TiC,Cr7C3,CrN,AlNi,AlNi3,FeAl2O4,CaS and TiN. The intermetallics such as NiAl and Ni3Al in the equilibrium products increase with an increase in the aluminum content in the thermit. The CaO can act as desulphurizer. In addition, CaO decreases the adiabatic temperature of the system. The adiabatic temperature of the system increases with a rise in the preheating temperature.
2003, 20(4): 18-22.
Abstract:
Effect of the added reinforcement on the nucleation processing of aluminum alloys was studied by a differential scanning calorimetry (DSC). The onset temperature measurement of monolithic alloys and composites reveals that nucleation of the aluminum phase is restricted with the presence of the reinforcement. In addition, the undercooling of α-Al phase increases with the decreasing of inter-fiber spacing. So α-Al phase cannot preferentially nucleate and grow on the reinforcement surface. In contrast to α-Al phase, the undercooling of primary silicon decreases with the presence of the reinforcement, which shows that the reinforcement can act as preferential nucleation sites for the primary silicon. It is effective to study the nucleation phenomenon of aluminum metal matrix composites by the DSC.
Effect of the added reinforcement on the nucleation processing of aluminum alloys was studied by a differential scanning calorimetry (DSC). The onset temperature measurement of monolithic alloys and composites reveals that nucleation of the aluminum phase is restricted with the presence of the reinforcement. In addition, the undercooling of α-Al phase increases with the decreasing of inter-fiber spacing. So α-Al phase cannot preferentially nucleate and grow on the reinforcement surface. In contrast to α-Al phase, the undercooling of primary silicon decreases with the presence of the reinforcement, which shows that the reinforcement can act as preferential nucleation sites for the primary silicon. It is effective to study the nucleation phenomenon of aluminum metal matrix composites by the DSC.
2003, 20(4): 23-28.
Abstract:
The tensile mechanical properties are studied for the aluminium alloy matrix gradient composites reinforced with SiC particles. Gradient coefficient Kx, a new evaluating index of mechanical properties of materials, is put forward. The results of the basic research show that a tri-axial stress will be produced in the tensile specimens because of components property difference of the metal matrix gradient composites (MMGC). The results of the tensile test and fracture analysis show that the elastic modulus E and yield strengthσ0.2 of the MMGC obey approximately the Role of Mixture (ROM) law. The tensile mechanical properties of the composites are remarkably influenced by the distribution of SiC particles. Fracture of the tensile specimen appears to have a toughness character and the composites can develop their potential in tensile properties when the matrix component is in outside and the component with high SiC volume fraction is in inside. Conversely, the fracture appears to have a brittleness character and mechanical properties of the composites will be decreased. The fracture way and the crack propagating orientation will be changed by the influence of many factors when the crack grows through the bonding interface. Interface cracking could be produced if there is a great difference of SiC volume fraction between two layers of the composites. The coefficients Kσb and Kδ can be used to identify gradient distribution and tensile properties level, but the coefficient KE can be used to identify steadiness extent of the composites.
The tensile mechanical properties are studied for the aluminium alloy matrix gradient composites reinforced with SiC particles. Gradient coefficient Kx, a new evaluating index of mechanical properties of materials, is put forward. The results of the basic research show that a tri-axial stress will be produced in the tensile specimens because of components property difference of the metal matrix gradient composites (MMGC). The results of the tensile test and fracture analysis show that the elastic modulus E and yield strengthσ0.2 of the MMGC obey approximately the Role of Mixture (ROM) law. The tensile mechanical properties of the composites are remarkably influenced by the distribution of SiC particles. Fracture of the tensile specimen appears to have a toughness character and the composites can develop their potential in tensile properties when the matrix component is in outside and the component with high SiC volume fraction is in inside. Conversely, the fracture appears to have a brittleness character and mechanical properties of the composites will be decreased. The fracture way and the crack propagating orientation will be changed by the influence of many factors when the crack grows through the bonding interface. Interface cracking could be produced if there is a great difference of SiC volume fraction between two layers of the composites. The coefficients Kσb and Kδ can be used to identify gradient distribution and tensile properties level, but the coefficient KE can be used to identify steadiness extent of the composites.
2003, 20(4): 29-33.
Abstract:
The exothermic dispersion method is used to study the dynamics mechanism CuO/Al reaction in-situ reinforced Al matrix composites. With the heat effect testing of CuO/Al reaction, the micro structural observing of materials and the mechanism analysis of the reaction process, a dynamics model of the compounding reaction is set up. The analysis illustrates that to increase the reaction temperature of the system and the content of aluminum will be beneficial to the reaction processing of forming Al2O3. The diffusion rate of Cu has a great influence on the reaction rate. Increasing the temperature and decreasing the thickness of the reaction film can increase the diffusion rate. The well-distributed Al2O3 in composite can be obtained. The higher the temperature, the longer the time, and the lower the viscosity of the medium, the smaller the size of particles, the more beneficial to the distribution of particles. Since Al2O3 is a phase with a higher melting point and because of the existence of CuAl2, most of the Al2O3 is distributed in the crystal boundary.
The exothermic dispersion method is used to study the dynamics mechanism CuO/Al reaction in-situ reinforced Al matrix composites. With the heat effect testing of CuO/Al reaction, the micro structural observing of materials and the mechanism analysis of the reaction process, a dynamics model of the compounding reaction is set up. The analysis illustrates that to increase the reaction temperature of the system and the content of aluminum will be beneficial to the reaction processing of forming Al2O3. The diffusion rate of Cu has a great influence on the reaction rate. Increasing the temperature and decreasing the thickness of the reaction film can increase the diffusion rate. The well-distributed Al2O3 in composite can be obtained. The higher the temperature, the longer the time, and the lower the viscosity of the medium, the smaller the size of particles, the more beneficial to the distribution of particles. Since Al2O3 is a phase with a higher melting point and because of the existence of CuAl2, most of the Al2O3 is distributed in the crystal boundary.
2003, 20(4): 34-38.
Abstract:
Si/C/N nano whisker with certain composition was prepared by Chemical Vapor Deposition (CVD). The phase of the whisker was determined as β-SiC by XRD. TG analysis indicated that the whisker can resist oxidation up to 700℃. Dependence of the dielectric constant and loss tangent on the frequency was investigated. Based on the dielectric constant, mono and double layer absorber materials were designed, and the absorber property of the designed materials was estimated. The mechanism of microwave depletion by Si/C/N nano whisker was discussed, which is due to the dopant of nitrogen atoms in SiC lattice.
Si/C/N nano whisker with certain composition was prepared by Chemical Vapor Deposition (CVD). The phase of the whisker was determined as β-SiC by XRD. TG analysis indicated that the whisker can resist oxidation up to 700℃. Dependence of the dielectric constant and loss tangent on the frequency was investigated. Based on the dielectric constant, mono and double layer absorber materials were designed, and the absorber property of the designed materials was estimated. The mechanism of microwave depletion by Si/C/N nano whisker was discussed, which is due to the dopant of nitrogen atoms in SiC lattice.
2003, 20(4): 39-45.
Abstract:
(Ti,W,Ta,Mo)(C,N)-(Co,Ni) cermets of less amount of Mo were produced using the self-made pre-alloyed solid solution powders of carbides or/and nitrides. Effects of phase composition of powders on the microstructure and properties were studied. The results suggest that the good corresponding relationships between the lattice constant of the pre-alloyed solid solution powders and the solid solution extent of elements are obtained. The addition of the pre-alloyed solid solution powders including the heavy metal elements of Ta and W is favorable to the spreading of heavy metal elements in the binders. The dissolution of Ti(C,N) reduces. The performance of cerments is improved. The cermets have the monolayer core-rim structure. The content of hard grains of wealthy Ti reduces and the content of hard grains of wealthy Ta and W increases. The grains of cerments are fine. The features of aggregation are not observed.
(Ti,W,Ta,Mo)(C,N)-(Co,Ni) cermets of less amount of Mo were produced using the self-made pre-alloyed solid solution powders of carbides or/and nitrides. Effects of phase composition of powders on the microstructure and properties were studied. The results suggest that the good corresponding relationships between the lattice constant of the pre-alloyed solid solution powders and the solid solution extent of elements are obtained. The addition of the pre-alloyed solid solution powders including the heavy metal elements of Ta and W is favorable to the spreading of heavy metal elements in the binders. The dissolution of Ti(C,N) reduces. The performance of cerments is improved. The cermets have the monolayer core-rim structure. The content of hard grains of wealthy Ti reduces and the content of hard grains of wealthy Ta and W increases. The grains of cerments are fine. The features of aggregation are not observed.
2003, 20(4): 46-50.
Abstract:
The aim of this paper is to study the effect of the interface on the macroscopic strength of ductile composites on the microscopic scale. An interface model based on microscopic fluctuation displacement (MFD) is proposed. Considering that the debonding of an interface can be regarded as a kind of material fracture, the strength of the interface is characterized by means of fracture toughness. The numerical results show that the effect of the interface on the off-axial strength of fiber-reinforced composites is most intensive and that the interface failure changes the distributing of the plastic zone in the matrix.
The aim of this paper is to study the effect of the interface on the macroscopic strength of ductile composites on the microscopic scale. An interface model based on microscopic fluctuation displacement (MFD) is proposed. Considering that the debonding of an interface can be regarded as a kind of material fracture, the strength of the interface is characterized by means of fracture toughness. The numerical results show that the effect of the interface on the off-axial strength of fiber-reinforced composites is most intensive and that the interface failure changes the distributing of the plastic zone in the matrix.
2003, 20(4): 51-57.
Abstract:
The crash characteristics are an important requirement of army helicopters. It is a main technical measure that the bottom fuselage structure possesses high impact energy-absorbing capability. The study of crash impact behavior of typical composite structure components is carried out the first time in China in this paper. Based on the components study, an optimum new structural assembly combining composite wave beams and thick honeycomb elements is put forward, which possesses high impact energy-absorbing capability. Theoretical calculating and testing are combined to do this research work. The validation and effectiveness of estimating and theoretical calculating are demonstrated by the results of tests. Also, the study result of this paper has been applied to the practical design of helicopter structures.
The crash characteristics are an important requirement of army helicopters. It is a main technical measure that the bottom fuselage structure possesses high impact energy-absorbing capability. The study of crash impact behavior of typical composite structure components is carried out the first time in China in this paper. Based on the components study, an optimum new structural assembly combining composite wave beams and thick honeycomb elements is put forward, which possesses high impact energy-absorbing capability. Theoretical calculating and testing are combined to do this research work. The validation and effectiveness of estimating and theoretical calculating are demonstrated by the results of tests. Also, the study result of this paper has been applied to the practical design of helicopter structures.
2003, 20(4): 58-62.
Abstract:
A general theory on stress analysis of laminated composite plate pressed by distributed loading is presented for overcoming the defect of classical plate theory and improving the precision of interfacial stress analysis. By means of the principle of superposition, the loading state of the composite laminated plate is decomposed into symmetric anti-symmetric states. The Fourier series and Legendre series are applied to describe the displacement field of each composite ply and glue layer in the above states. The principle of generalized potential energy is used to determine the unknown coefficients of the above series. In addition, the glue layers are considered to have finite thickness and finite elastic constants in this analysis. From the computational results, it can be shown that the displacements and stresses converge very well, and the distributions of transversal shearing and normal stresses obtained from the constitutive equation agree with those obtained from the equilibrium equation very well.
A general theory on stress analysis of laminated composite plate pressed by distributed loading is presented for overcoming the defect of classical plate theory and improving the precision of interfacial stress analysis. By means of the principle of superposition, the loading state of the composite laminated plate is decomposed into symmetric anti-symmetric states. The Fourier series and Legendre series are applied to describe the displacement field of each composite ply and glue layer in the above states. The principle of generalized potential energy is used to determine the unknown coefficients of the above series. In addition, the glue layers are considered to have finite thickness and finite elastic constants in this analysis. From the computational results, it can be shown that the displacements and stresses converge very well, and the distributions of transversal shearing and normal stresses obtained from the constitutive equation agree with those obtained from the equilibrium equation very well.
2003, 20(4): 63-66.
Abstract:
A numerical method, cell-element method, which establishes the relation between microstructure and macro-response in 3D braided composites is presented in this paper. Firstly, a 3-D braided composite structure is meshed by the unit cells, then based on the analysis of the micro-structure, the variables of the micro-structure are translated into the variables of macro-nodes, and the stiffness of the cell-element is formulated. The numerical results show that this method can feedback the response of macro-variables to any tiny change in the micro-structure.
A numerical method, cell-element method, which establishes the relation between microstructure and macro-response in 3D braided composites is presented in this paper. Firstly, a 3-D braided composite structure is meshed by the unit cells, then based on the analysis of the micro-structure, the variables of the micro-structure are translated into the variables of macro-nodes, and the stiffness of the cell-element is formulated. The numerical results show that this method can feedback the response of macro-variables to any tiny change in the micro-structure.
2003, 20(4): 67-71.
Abstract:
In this paper, by adding EVA to magnesian oxychloride cement in different amount and adopting different EVA for the fiber treatment, mechanical and microscopic tests for the composites samples were carried out to research the effect of EVA emulsoid on the interfacial adhesion strength and discuss its mechanism. The results indicate that EVA added to cement as an additive can improve the interfacial adhesion strength of the glass fiber reinforced magnesian oxychloride cement obviously; while using EVA as a surface active agent to deal with glass fibers has no evident influence on the interfacial adhesion strength of composites.
In this paper, by adding EVA to magnesian oxychloride cement in different amount and adopting different EVA for the fiber treatment, mechanical and microscopic tests for the composites samples were carried out to research the effect of EVA emulsoid on the interfacial adhesion strength and discuss its mechanism. The results indicate that EVA added to cement as an additive can improve the interfacial adhesion strength of the glass fiber reinforced magnesian oxychloride cement obviously; while using EVA as a surface active agent to deal with glass fibers has no evident influence on the interfacial adhesion strength of composites.
2003, 20(4): 72-76.
Abstract:
This paper describes interfacial microstructures of hydrated products of cement and three types of superfine powders, which are fly ash, silica fume and nano-SiO2. Hydration mechanics of these three superfine powders and cement and their improvement of interfacial microstructures are researched also; therefore a concept of secondary interface is developed. The authors believe that these three superfine powders can improve interfacial microstructures and their effect degrees increased by fly ash, silica fume and nano-SiO2. From the analysis of interfacial microstructures of hydrated products, the hydrated product of nano-SiO2 is the densest and homogeneous when these three powders are used alone, and on the other hand, the hydration degree of mixture of these three powders shows much higher.
This paper describes interfacial microstructures of hydrated products of cement and three types of superfine powders, which are fly ash, silica fume and nano-SiO2. Hydration mechanics of these three superfine powders and cement and their improvement of interfacial microstructures are researched also; therefore a concept of secondary interface is developed. The authors believe that these three superfine powders can improve interfacial microstructures and their effect degrees increased by fly ash, silica fume and nano-SiO2. From the analysis of interfacial microstructures of hydrated products, the hydrated product of nano-SiO2 is the densest and homogeneous when these three powders are used alone, and on the other hand, the hydration degree of mixture of these three powders shows much higher.
2003, 20(4): 77-80.
Abstract:
The molding filling process is a very important phase in RTM. This paper studies the RTM process and its resin flow process. The governing equations of resin flow are built up. The boundary-fitted coordinate system and the finite difference method are employed for simulating the resin flow process. The successive resin flow front position and the pressure distribution at the final stage are obtained, and good agreement is found between the numerical simulation and experimental results as well as other investigations.
The molding filling process is a very important phase in RTM. This paper studies the RTM process and its resin flow process. The governing equations of resin flow are built up. The boundary-fitted coordinate system and the finite difference method are employed for simulating the resin flow process. The successive resin flow front position and the pressure distribution at the final stage are obtained, and good agreement is found between the numerical simulation and experimental results as well as other investigations.
2003, 20(4): 81-87.
Abstract:
A kind of highly moisture-resistant epoxy resin, 9,9-bis fluorene (Ⅱ), was synthesized. The optimal epoxidizing condition was obtained by studying the influence of different factors in the reaction, such as the amount of the reactants and their concentration, the amount of the catalyzer, the reaction temperature and time. As a result the epoxy value of the products reached 97% of the calculated value. The mechanical properties of the cured pure Ⅱ resin were studied. The water-absorbance, the glass transfer temperature and the module of the pure Ⅱ and the Ⅱ/AG-80 mixtures before and after absorbing water were investigated. The results indicate that the water-absorbance of the resin mixturesis reduced by the addition of Ⅱ, and Tg and E' remain comparatively high after absorbing water compared with the pure AG-80. The addition of Ⅱ could improve the hot-wet property of AG-80.
A kind of highly moisture-resistant epoxy resin, 9,9-bis fluorene (Ⅱ), was synthesized. The optimal epoxidizing condition was obtained by studying the influence of different factors in the reaction, such as the amount of the reactants and their concentration, the amount of the catalyzer, the reaction temperature and time. As a result the epoxy value of the products reached 97% of the calculated value. The mechanical properties of the cured pure Ⅱ resin were studied. The water-absorbance, the glass transfer temperature and the module of the pure Ⅱ and the Ⅱ/AG-80 mixtures before and after absorbing water were investigated. The results indicate that the water-absorbance of the resin mixturesis reduced by the addition of Ⅱ, and Tg and E' remain comparatively high after absorbing water compared with the pure AG-80. The addition of Ⅱ could improve the hot-wet property of AG-80.
2003, 20(4): 88-95.
Abstract:
A novel nano-magnesium hydroxide powder was chosen as a dispersion phase material and mixed with nitrile rubber(NBR), ethylene-propylene-diene mischpolymer (EPDM), styrene-butadiene rubber(SBR) and silicone rubber(SiR) to make a series of composites. By scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and Payne effect, the dispersion morphology and network structure of the composites were investigated in detail. The experimental results indicate that viscosity and surface energy of the matrix play very important roles in dispersion and network forming of nano-powder in rubber. The higher the viscosity or surface energy (EPDM, NBR) of the matrix, the finer the dispersion of nano-powder, and the more easily the network forms. The network is flexible due to the large proportion macromolecules involved. But in the rubber (SiR) with low viscosity and surface energy, there exist isolated agglomerates, not forming network in the low loading condition, while in the high loading condition the rigid network is formed by direct contacting of agglomerates, and the proportion of the macromolecule in the network is low. Traditional models can not describe the effect of main factors on the force on the agglomerates; a new modified model is proposed to introduce the effect of surface energy of the matrix.
A novel nano-magnesium hydroxide powder was chosen as a dispersion phase material and mixed with nitrile rubber(NBR), ethylene-propylene-diene mischpolymer (EPDM), styrene-butadiene rubber(SBR) and silicone rubber(SiR) to make a series of composites. By scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and Payne effect, the dispersion morphology and network structure of the composites were investigated in detail. The experimental results indicate that viscosity and surface energy of the matrix play very important roles in dispersion and network forming of nano-powder in rubber. The higher the viscosity or surface energy (EPDM, NBR) of the matrix, the finer the dispersion of nano-powder, and the more easily the network forms. The network is flexible due to the large proportion macromolecules involved. But in the rubber (SiR) with low viscosity and surface energy, there exist isolated agglomerates, not forming network in the low loading condition, while in the high loading condition the rigid network is formed by direct contacting of agglomerates, and the proportion of the macromolecule in the network is low. Traditional models can not describe the effect of main factors on the force on the agglomerates; a new modified model is proposed to introduce the effect of surface energy of the matrix.
2003, 20(4): 96-100.
Abstract:
By using acrylic acid to modify phenolic epoxy resin, an acid resistant resin matrix formulation for pultrusion insulant rod which was toughened by DDSA was optimized. The curing reaction of the modified epoxy resin system was studied by DSC, TGA and FT-IR. The acid resistance, heat resistance, mechanical and electrical properties of the cured compound epoxy resin (cast) and the glass fiber reinforced epoxy resin matrix pultrusion rod were also studied. Experiments show that the resin matrix was suited for pultrusion, and the properties of the insulant rod are excellent.
By using acrylic acid to modify phenolic epoxy resin, an acid resistant resin matrix formulation for pultrusion insulant rod which was toughened by DDSA was optimized. The curing reaction of the modified epoxy resin system was studied by DSC, TGA and FT-IR. The acid resistance, heat resistance, mechanical and electrical properties of the cured compound epoxy resin (cast) and the glass fiber reinforced epoxy resin matrix pultrusion rod were also studied. Experiments show that the resin matrix was suited for pultrusion, and the properties of the insulant rod are excellent.
2003, 20(4): 101-106.
Abstract:
PBO super fibre is submitted to a corona treatment, and the properties of the interphase between PBO fibres and epoxy matrix systems are optimized by a surface treatment process of the fibres. The relation is studied between this surface treatment and the resulting chemical and physical surface structure, as measured with XPS,FT-IR,SEM and surface wettability. The adhesion strength in fibre-epoxy systems, as measured with single-fibre pull-out and short beam shear experiments, has been established and related to the macromechanical data of real composites. It is concluded that corona-treated fibres may cause 25.6% improvement in the interfacial shear strength(IFSS) due to the increase of the oxygen surface content and the well wettability to water. But the short beam shear strength values from the corona-treated and untreated fibres showed only small differences.
PBO super fibre is submitted to a corona treatment, and the properties of the interphase between PBO fibres and epoxy matrix systems are optimized by a surface treatment process of the fibres. The relation is studied between this surface treatment and the resulting chemical and physical surface structure, as measured with XPS,FT-IR,SEM and surface wettability. The adhesion strength in fibre-epoxy systems, as measured with single-fibre pull-out and short beam shear experiments, has been established and related to the macromechanical data of real composites. It is concluded that corona-treated fibres may cause 25.6% improvement in the interfacial shear strength(IFSS) due to the increase of the oxygen surface content and the well wettability to water. But the short beam shear strength values from the corona-treated and untreated fibres showed only small differences.
2003, 20(4): 107-110.
Abstract:
This paper studied the near-infrared reflectance spectroscopy of glass-fiber reinforced phenolic resin prepreg. The mathematical models between near-infrared spectral parameters and resin content, pre-curing degree and volatile content are built up and the effects of the analysis accuracy were investigated using the chemometrics method. It was found that average absolute errors of the three estimate outcomes were under 0.74 %,1.18 % and 0.26 % respectively. The above results show the feasibility of the near-infrared analytic technology for detecting the quality of composite prepregs.
This paper studied the near-infrared reflectance spectroscopy of glass-fiber reinforced phenolic resin prepreg. The mathematical models between near-infrared spectral parameters and resin content, pre-curing degree and volatile content are built up and the effects of the analysis accuracy were investigated using the chemometrics method. It was found that average absolute errors of the three estimate outcomes were under 0.74 %,1.18 % and 0.26 % respectively. The above results show the feasibility of the near-infrared analytic technology for detecting the quality of composite prepregs.
2003, 20(4): 111-116.
Abstract:
The vacuum infusion molding process is becoming popular as a new type of Liquid Composites Molding Processes. In the paper, the vacuum infusion molding process based on grooves was investigated by experiments, and the parameters of width, depth and spacing for flow grooves and spacing for supply grooves were optimized according on the molding experiments and various factors that had influence on the mold filling process were discussed. Furthermore, the whole vacuum infusion procedure is introduced in detail, taking the manufacture of a sandwich panel in one infusion for a case.
The vacuum infusion molding process is becoming popular as a new type of Liquid Composites Molding Processes. In the paper, the vacuum infusion molding process based on grooves was investigated by experiments, and the parameters of width, depth and spacing for flow grooves and spacing for supply grooves were optimized according on the molding experiments and various factors that had influence on the mold filling process were discussed. Furthermore, the whole vacuum infusion procedure is introduced in detail, taking the manufacture of a sandwich panel in one infusion for a case.
2003, 20(4): 117-121.
Abstract:
The effects of longitudinal constant tensile loads on transverse behaviors and transverse loads on longitudinal behaviors of a single ply of nylon cord-rubber composite are studied respectively under biaxial tensile condition with cruciform specimens in this paper. Experiment results indicate that the effects of longitudinal constant tensile loads on transverse tensile behaviors are obvious. Transverse stress-strain behaviors change largely compared with uniaxial transverse tensile behavior; transverse tensile strength increases first and then decreases; fracture strain and deformation energy decrease by increasing of longitudinal tensile loads; the results are induced by common actions of rigidification and damnification caused by longitudinal tensile loads. However, the effects of transverse constant tensile load on longitudinal tensile mechanical behavior are not distinctive. It can be ascribed to large discrepancy between longitudinal and transverse properties of nylon cord-rubber composite.
The effects of longitudinal constant tensile loads on transverse behaviors and transverse loads on longitudinal behaviors of a single ply of nylon cord-rubber composite are studied respectively under biaxial tensile condition with cruciform specimens in this paper. Experiment results indicate that the effects of longitudinal constant tensile loads on transverse tensile behaviors are obvious. Transverse stress-strain behaviors change largely compared with uniaxial transverse tensile behavior; transverse tensile strength increases first and then decreases; fracture strain and deformation energy decrease by increasing of longitudinal tensile loads; the results are induced by common actions of rigidification and damnification caused by longitudinal tensile loads. However, the effects of transverse constant tensile load on longitudinal tensile mechanical behavior are not distinctive. It can be ascribed to large discrepancy between longitudinal and transverse properties of nylon cord-rubber composite.
2003, 20(4): 122-127.
Abstract:
Kinetics and influencing factors (such as pH value, TEOS concentration and temperature) of sol-gel transition of SiO2 sol prepared through the hydrolytic method were studied. The activated energy of the transition was calculated also. The results showed that the molecule growth mode of sol is linear in acid conditions. A gradual increase in coagulation time of sol is observed for pH value lower than 2. Further increase of PH value slightly decreases the coagulation time. Reaction activated energy is related to pH value of systems also. The results were explained by chemical bond, charge density and reaction mechanism.
Kinetics and influencing factors (such as pH value, TEOS concentration and temperature) of sol-gel transition of SiO2 sol prepared through the hydrolytic method were studied. The activated energy of the transition was calculated also. The results showed that the molecule growth mode of sol is linear in acid conditions. A gradual increase in coagulation time of sol is observed for pH value lower than 2. Further increase of PH value slightly decreases the coagulation time. Reaction activated energy is related to pH value of systems also. The results were explained by chemical bond, charge density and reaction mechanism.
2003, 20(4): 128-132.
Abstract:
A kind of composite called wood-inorganic composite was produced by the method of double ions diffusion with fast growing Poplar wood, which is abundant in China, as the raw material and the ionic compound of silicon, aluminum, boron and phosphorous ions as the dipping solution. There were deposit reactions between the various kinds of ions in the walls and vessels of wood's cells. The wood's performance of decomposition in high temperature and strength were improved owing to water-fast deposits filling in holes of the wood. The results show that the performance of the wood is much more improved with the method of impregnating the solution into the wood by force by a self-made plus-minus pressure system compared to the method of impregnating the solution into the wood at normal press and temperature, and its WPG increases by 3~5 times. The SEM micrographs show that inorganic substance is filled not only in the vessels, fibers but also in the pits of the wood. The DTA Curve shows that the highest decomposition temperature of the treated wood is 420℃ and its loss percent of weight is 32 % at 550℃.In the research area,the strength of the treated wood is in positive proportion with the weight percent gain of the composites.
A kind of composite called wood-inorganic composite was produced by the method of double ions diffusion with fast growing Poplar wood, which is abundant in China, as the raw material and the ionic compound of silicon, aluminum, boron and phosphorous ions as the dipping solution. There were deposit reactions between the various kinds of ions in the walls and vessels of wood's cells. The wood's performance of decomposition in high temperature and strength were improved owing to water-fast deposits filling in holes of the wood. The results show that the performance of the wood is much more improved with the method of impregnating the solution into the wood by force by a self-made plus-minus pressure system compared to the method of impregnating the solution into the wood at normal press and temperature, and its WPG increases by 3~5 times. The SEM micrographs show that inorganic substance is filled not only in the vessels, fibers but also in the pits of the wood. The DTA Curve shows that the highest decomposition temperature of the treated wood is 420℃ and its loss percent of weight is 32 % at 550℃.In the research area,the strength of the treated wood is in positive proportion with the weight percent gain of the composites.
2003, 20(4): 133-135.
Abstract:
The degree and pattern of damage in composite armors influenced by the shock wave were decided by comprehensive factors. Herein, a wave-absorbed layer was used to decrease the degree of damage in materials by shock wave. Meanwhile, some effective measures were adopted to improve the ballistic performance of composite armors based on decreasing the reflection and overlapping of the shock wave. The experiment results shows that the wave-absorbed layer improves the ballistic performance of composite armors remarkably.
The degree and pattern of damage in composite armors influenced by the shock wave were decided by comprehensive factors. Herein, a wave-absorbed layer was used to decrease the degree of damage in materials by shock wave. Meanwhile, some effective measures were adopted to improve the ballistic performance of composite armors based on decreasing the reflection and overlapping of the shock wave. The experiment results shows that the wave-absorbed layer improves the ballistic performance of composite armors remarkably.
2003, 20(4): 136-140.
Abstract:
The vacuum infusion molding process is becoming increasingly popular as a new type of Liquid Composites Molding Processes for the production of large composite parts with complex geometry. In the paper, the vacuum infusion molding process based on a high-permeable medium was investigated by experiments. The optimistic high-permeable medium was selected according to the visualization molding experiments and various factors that had influence to the mold filling process were discussed. Furthermore, the whole procedure is introduced in detail, taking the manufacture of a model boat in one infusion for a case.
The vacuum infusion molding process is becoming increasingly popular as a new type of Liquid Composites Molding Processes for the production of large composite parts with complex geometry. In the paper, the vacuum infusion molding process based on a high-permeable medium was investigated by experiments. The optimistic high-permeable medium was selected according to the visualization molding experiments and various factors that had influence to the mold filling process were discussed. Furthermore, the whole procedure is introduced in detail, taking the manufacture of a model boat in one infusion for a case.
