1990 Vol. 7, No. 4
1990, 7(4): 1-8.
Abstract:
The development and research status of ceramic matrix composites are reviewed an danalysc din this paper.The main topics includes the development process and application prospects of ceramic matrix composites, the research of fibsr material,the toughening research of various ceramic matrix materials,the fabrication techniques,the toughening mechanisms and structure properties of ceramic matrix composites.Finally, some simplc opinions on the further development of ceramic matrix composites are presented.
The development and research status of ceramic matrix composites are reviewed an danalysc din this paper.The main topics includes the development process and application prospects of ceramic matrix composites, the research of fibsr material,the toughening research of various ceramic matrix materials,the fabrication techniques,the toughening mechanisms and structure properties of ceramic matrix composites.Finally, some simplc opinions on the further development of ceramic matrix composites are presented.
1990, 7(4): 9-15.
Abstract:
A series of tensile experiments with the testing strain rate ranging from 10-4 to 102 S-1,were performed for glass fibre,kevlar-49 and carbon fibre bundle-s by DT-5000 Material Testing Machine and a self-designed Pendulum Tensile Impact Set-up. It was the first time to obtain the stress-strain curves of above materials at high strain rates.The results show that for glassfibre the strength,fracturo strain and critical strain energy density are very sensitive to strain rate, and the elastic modulus increases with the rising of the rate.For the kevlar-49 fibre,the strain rate sensitivity is reduced:And for the carbon fibre,however.the mechanical properties are indepen dent of the strain rate.
A series of tensile experiments with the testing strain rate ranging from 10-4 to 102 S-1,were performed for glass fibre,kevlar-49 and carbon fibre bundle-s by DT-5000 Material Testing Machine and a self-designed Pendulum Tensile Impact Set-up. It was the first time to obtain the stress-strain curves of above materials at high strain rates.The results show that for glassfibre the strength,fracturo strain and critical strain energy density are very sensitive to strain rate, and the elastic modulus increases with the rising of the rate.For the kevlar-49 fibre,the strain rate sensitivity is reduced:And for the carbon fibre,however.the mechanical properties are indepen dent of the strain rate.
1990, 7(4): 17-27.
Abstract:
Most composite sandwich plates have cores with finite compressed modulus(i.e.Ezo≠∞). A new revised theory for Reissner model has been developed to sole bending problem of composite sand with plates with thick and soft cores, in which two aspects of revision to Reissner theory have been done as following.
Most composite sandwich plates have cores with finite compressed modulus(i.e.Ezo≠∞). A new revised theory for Reissner model has been developed to sole bending problem of composite sand with plates with thick and soft cores, in which two aspects of revision to Reissner theory have been done as following.
1990, 7(4): 29-34.
Abstract:
The static tensile tests of carbon fiber reinforced composite specimens ([O°],[1±45°],[0°/90°]s)without notch,with double edge notch,central hole and central notch have been investigated experimentally. Using ultrasonic scanning and imager method,internal damage and damage persentage in different loading regions of carbon/epoxy composite were detected.The curves of loading-damage percentage and pictures of internal flaw distribution in different depths were obtained.The results show that during static tensile test,the crack propagates along tha direction of the fiber interface instead of that of the edge notch in specimen.The notch doesnot affect the load-bearing capacity of ligament of the specimen.For the specimen with central notch,interface crack occurs at the tip of the notch And the specim en with central hole,damage initiates around the hole, later,it extends along the fiber direction.In this paper. the failure mecha nism is analysed also.
The static tensile tests of carbon fiber reinforced composite specimens ([O°],[1±45°],[0°/90°]s)without notch,with double edge notch,central hole and central notch have been investigated experimentally. Using ultrasonic scanning and imager method,internal damage and damage persentage in different loading regions of carbon/epoxy composite were detected.The curves of loading-damage percentage and pictures of internal flaw distribution in different depths were obtained.The results show that during static tensile test,the crack propagates along tha direction of the fiber interface instead of that of the edge notch in specimen.The notch doesnot affect the load-bearing capacity of ligament of the specimen.For the specimen with central notch,interface crack occurs at the tip of the notch And the specim en with central hole,damage initiates around the hole, later,it extends along the fiber direction.In this paper. the failure mecha nism is analysed also.
1990, 7(4): 35-43.
Abstract:
A semi-analytical and semi-numerical method for various structure analyses of composite materials is proposed in this paper.This method has a stronger applicability than purely analytical ore and is easy to command as well as involves small amount of calculation and higher accuracy than purely numerical one and is easy to carry out on micro-computers.The method presented here is helpful to provide a practical and efficient approach for mechanical analyses of composite materials.
A semi-analytical and semi-numerical method for various structure analyses of composite materials is proposed in this paper.This method has a stronger applicability than purely analytical ore and is easy to command as well as involves small amount of calculation and higher accuracy than purely numerical one and is easy to carry out on micro-computers.The method presented here is helpful to provide a practical and efficient approach for mechanical analyses of composite materials.
1990, 7(4): 45-51.
Abstract:
In this article,a single-mode optical fibre is used instead of an ordinary fibre to be covered up with polyester.When the He-Ne laser light goes through the single-mode optical fibre and the reference optical fibre of the same length,we could test the stress and strain in the optical fibre in composites from the interference of the two beams of light. Then we could get many results about the interface micro-mechanics in composites.This article has developed a new sensitive test method about composites.
In this article,a single-mode optical fibre is used instead of an ordinary fibre to be covered up with polyester.When the He-Ne laser light goes through the single-mode optical fibre and the reference optical fibre of the same length,we could test the stress and strain in the optical fibre in composites from the interference of the two beams of light. Then we could get many results about the interface micro-mechanics in composites.This article has developed a new sensitive test method about composites.
1990, 7(4): 54-59.
Abstract:
The elastic modulus of short fibre reinforced rubber composites and the factors that influence them have been cxamined.A half-empiric equation describing the ralation between the elastic modulus and the short fibre volume fraction is introduced to predict the modulus of composits, This equation is based upon Halpin-Tsai equation and approximately agrees with experimental results.
The elastic modulus of short fibre reinforced rubber composites and the factors that influence them have been cxamined.A half-empiric equation describing the ralation between the elastic modulus and the short fibre volume fraction is introduced to predict the modulus of composits, This equation is based upon Halpin-Tsai equation and approximately agrees with experimental results.
1990, 7(4): 61-66.
Abstract:
Fourier transform infrared (FT-IR)spectroscopy was used to determine the reaction rate of glycidyl dibromophenyl ether(G-48)with methyl tetrahydrophthalic anhydride(THPA) and to compare it with that of the bisphenol-A epoxy resin(E-39)with THPA. The comparison of the reaction rates of the two systems showed that they were noticeably different in various temperature ranges.The apparent energies of activation of the two systems were approximately equal.The curing process of a system composed of a mixture of G-48 and E-39 with THPA as curing agent also was studied by FT-IR.It has been found that the curing behavior of G-48/E-39 with THPA matched the reaction characteristics of the combination of E-39 and G-48 reacting alone with THPA. The curing mechanism of G-48/F-39 mixture system with THPA was proposed.
Fourier transform infrared (FT-IR)spectroscopy was used to determine the reaction rate of glycidyl dibromophenyl ether(G-48)with methyl tetrahydrophthalic anhydride(THPA) and to compare it with that of the bisphenol-A epoxy resin(E-39)with THPA. The comparison of the reaction rates of the two systems showed that they were noticeably different in various temperature ranges.The apparent energies of activation of the two systems were approximately equal.The curing process of a system composed of a mixture of G-48 and E-39 with THPA as curing agent also was studied by FT-IR.It has been found that the curing behavior of G-48/E-39 with THPA matched the reaction characteristics of the combination of E-39 and G-48 reacting alone with THPA. The curing mechanism of G-48/F-39 mixture system with THPA was proposed.
1990, 7(4): 67-71.
Abstract:
Orientation relationship between the whisker and the matrix in a silicon carbide whisker reinforced aluminium composite made by squeeze casting has been investigated by using transmission electron microscopy (TEM) technique. Through observation a new phenomenon has been revealed:<110>SiC//<110>Al and <111>SiC//<100>Al,(about 4°difference). According to the above experimental result a semi-coherent model of the interfacial microstructure in the SiCw/Al composite has been presented.
Orientation relationship between the whisker and the matrix in a silicon carbide whisker reinforced aluminium composite made by squeeze casting has been investigated by using transmission electron microscopy (TEM) technique. Through observation a new phenomenon has been revealed:<110>SiC//<110>Al and <111>SiC//<100>Al,(about 4°difference). According to the above experimental result a semi-coherent model of the interfacial microstructure in the SiCw/Al composite has been presented.
1990, 7(4): 73-78.
Abstract:
The infiltration processes of melt aluminium alloy into SiC whisker pre-form were analyzed during the fabrication of SiCw/Al composite by squeeze casting method.The infiltration pressure was calculated to be less than 2 MPa.The compressive tests of the SiC whisker preforms with different whisker volume fraction were carried out in the condition similar to that of the infiltration processes,and the experimental results showed that with the increase of the fabrication prefssure,the preform was compressed and so the volume fraction of whisker of the preform was increased.Based on the analysis of the fabrication processes,it was considered that it needs a period of time for the infiltration processes to be finished so that the preforms were compressed before they were infiltrated by melt aluminium when the fabrication pressure reached the maximum value,and therefore the volume fraction of whisker of preforms was increased.When the pressing speed was very high, the volume fraction of whisker of the SiCw/Al composite was mainly decided by the whisker volume fraetion of preform and the fabrication pressure.
The infiltration processes of melt aluminium alloy into SiC whisker pre-form were analyzed during the fabrication of SiCw/Al composite by squeeze casting method.The infiltration pressure was calculated to be less than 2 MPa.The compressive tests of the SiC whisker preforms with different whisker volume fraction were carried out in the condition similar to that of the infiltration processes,and the experimental results showed that with the increase of the fabrication prefssure,the preform was compressed and so the volume fraction of whisker of the preform was increased.Based on the analysis of the fabrication processes,it was considered that it needs a period of time for the infiltration processes to be finished so that the preforms were compressed before they were infiltrated by melt aluminium when the fabrication pressure reached the maximum value,and therefore the volume fraction of whisker of preforms was increased.When the pressing speed was very high, the volume fraction of whisker of the SiCw/Al composite was mainly decided by the whisker volume fraetion of preform and the fabrication pressure.
1990, 7(4): 79-84.
Abstract:
Bismaleimides are being increasingly used as matrix resins for advanced composites.There are some ploblems,however,such as the brittleness of this kind of polymers due to the high crosslink density in network polymgrs.In this article,the recent advancement of modified bismaleimide resin systems with improved toughness as matrix for composites is summarized.The chemical methods for toughening bismaleimide such as rubber toughening of bismaleimide,copolymerizing it with allylphenyl compounds Michael addition chain extention,taking thermoplastics as toughening modifiers,using bismaleimide-modified epoxy resins and synthesizing chain-extended bismaleimides are reviewed.
Bismaleimides are being increasingly used as matrix resins for advanced composites.There are some ploblems,however,such as the brittleness of this kind of polymers due to the high crosslink density in network polymgrs.In this article,the recent advancement of modified bismaleimide resin systems with improved toughness as matrix for composites is summarized.The chemical methods for toughening bismaleimide such as rubber toughening of bismaleimide,copolymerizing it with allylphenyl compounds Michael addition chain extention,taking thermoplastics as toughening modifiers,using bismaleimide-modified epoxy resins and synthesizing chain-extended bismaleimides are reviewed.
