2000 Vol. 17, No. 2
2000, 17(2): 1-7.
Abstract:
This paper outlines the trend of development of both macro and micro mechanics (MMM) and strengthening and toughening design (STD) for advanced composite materials both at home and abroad. The scientific meaning, main study topics as well as new challenges for the strengthening and toughening design on composites are illustrated. The basic mechanisms, principles as well as approaches of MMM and STD for advanced composites are discussed. The existent difficulties or open topics and the direction of development on MMM and STD for advanced composites are made clear as well.
This paper outlines the trend of development of both macro and micro mechanics (MMM) and strengthening and toughening design (STD) for advanced composite materials both at home and abroad. The scientific meaning, main study topics as well as new challenges for the strengthening and toughening design on composites are illustrated. The basic mechanisms, principles as well as approaches of MMM and STD for advanced composites are discussed. The existent difficulties or open topics and the direction of development on MMM and STD for advanced composites are made clear as well.
2000, 17(2): 8-11.
Abstract:
A new curing agent was synthesized by the reaction of phenylamine formaldehyde and dicyanodiamide. It had better solubility in epoxy resin and in a kind of low boiling point than dicyanodiamide, and it could cure epoxy resin under about 125℃ with accelerator. The cured resin had good mechanical properties and moisture resistance. With this resin curing system, a pre impregnating was obtained and the glass clothing composite had good mechanical properties and moisture resistance as the same product of abroad.
A new curing agent was synthesized by the reaction of phenylamine formaldehyde and dicyanodiamide. It had better solubility in epoxy resin and in a kind of low boiling point than dicyanodiamide, and it could cure epoxy resin under about 125℃ with accelerator. The cured resin had good mechanical properties and moisture resistance. With this resin curing system, a pre impregnating was obtained and the glass clothing composite had good mechanical properties and moisture resistance as the same product of abroad.
2000, 17(2): 12-15.
Abstract:
By using the prepolymer of o,o' diallyl bisphenol A modified bis(4.4' maleimide phenyl) metheat to modify the anhydride/epoxy resin curable system, a heat resistant resin matrix formulation was optimized. Curing mechanism and kinetic of the modified epoxy resin system were studied by DSC, TGA and FT IR. The all round properties of the cured compound epoxy resin system 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 have reached the requirements of the technical standards.
By using the prepolymer of o,o' diallyl bisphenol A modified bis(4.4' maleimide phenyl) metheat to modify the anhydride/epoxy resin curable system, a heat resistant resin matrix formulation was optimized. Curing mechanism and kinetic of the modified epoxy resin system were studied by DSC, TGA and FT IR. The all round properties of the cured compound epoxy resin system 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 have reached the requirements of the technical standards.
2000, 17(2): 16-19.
Abstract:
MC nylon reinforced with carbon fiber was prepared through anion polymerization. The influence of carbon fiber content on the properties and microstructure of the C/MC composite was studied. It was shown that the composite exhibited excellent mechanical properties. Uniform dispersion of carbon fiber in the matrix had been obtained. The composite possessed good adhesion properties between carbon fiber and the matrix.
MC nylon reinforced with carbon fiber was prepared through anion polymerization. The influence of carbon fiber content on the properties and microstructure of the C/MC composite was studied. It was shown that the composite exhibited excellent mechanical properties. Uniform dispersion of carbon fiber in the matrix had been obtained. The composite possessed good adhesion properties between carbon fiber and the matrix.
2000, 17(2): 20-24.
Abstract:
The behavior of matrix is an important factor for the performances of short fiber reinforced metal matrix composites. Through the elastic plastic finite element method, which is based on a 3 D single fiber model, the stress distributions and deformation characteristics of matrix in short fiber reinforced metal matrix composite were studied in different fiber orientations and interfacial bond. It is shown that the changes in fiber orientation and interfacial bond have great effect on the stress distributions and deformation characteristics of matrix.
The behavior of matrix is an important factor for the performances of short fiber reinforced metal matrix composites. Through the elastic plastic finite element method, which is based on a 3 D single fiber model, the stress distributions and deformation characteristics of matrix in short fiber reinforced metal matrix composite were studied in different fiber orientations and interfacial bond. It is shown that the changes in fiber orientation and interfacial bond have great effect on the stress distributions and deformation characteristics of matrix.
2000, 17(2): 25-29.
Abstract:
The behavior of matrix is an important factor in short fiber reinforced metal matrix composite. Through the experimental analysis and the axi symmetrical finite element method based on a certain theoretical model, the effects of matrix performance on the mechanical behavior of short fiber reinforced metal matrix composite were studied in detail. The effects of matrix characteristics on such aspects as stress transfer, tensile strength and fracture mechanism were discussed. As a result, the change of matrix performance influences stress transfer, and thus changes the tensile strength and fracture mechanism of the composite greatly.
The behavior of matrix is an important factor in short fiber reinforced metal matrix composite. Through the experimental analysis and the axi symmetrical finite element method based on a certain theoretical model, the effects of matrix performance on the mechanical behavior of short fiber reinforced metal matrix composite were studied in detail. The effects of matrix characteristics on such aspects as stress transfer, tensile strength and fracture mechanism were discussed. As a result, the change of matrix performance influences stress transfer, and thus changes the tensile strength and fracture mechanism of the composite greatly.
2000, 17(2): 30-33.
Abstract:
The corrosion resistance behavior of rare earth metal(REM) conversion coating on aluminum based metal matrix composites(MMC) Al6061/SiC P was examined by electrochemical method. Both anodic and cathodic reactions of corrosion were reduced by the existing film. Thus the corrosion rate was decreased. The microstructure of the film was studied by scanning electron microscope(SEM): the film consists of groups of different sizes of spherical particles which grew gradually to cover the background of the Al based MMC. The X ray diffraction (XRD) analysis revealed the non crystalline of the film. The constituent of the film was studied by X ray photoelectron spectroscopy (XPS): the film consists of cerium dioxide and hydrated cerium oxide.
The corrosion resistance behavior of rare earth metal(REM) conversion coating on aluminum based metal matrix composites(MMC) Al6061/SiC P was examined by electrochemical method. Both anodic and cathodic reactions of corrosion were reduced by the existing film. Thus the corrosion rate was decreased. The microstructure of the film was studied by scanning electron microscope(SEM): the film consists of groups of different sizes of spherical particles which grew gradually to cover the background of the Al based MMC. The X ray diffraction (XRD) analysis revealed the non crystalline of the film. The constituent of the film was studied by X ray photoelectron spectroscopy (XPS): the film consists of cerium dioxide and hydrated cerium oxide.
2000, 17(2): 34-37.
Abstract:
In the present paper a sol gel γ Al2O3 coating method was employed to modify the interface properties of the aluminum borate whisker reinforced 6061Al composites. Results indicate that an alumina coating with a thickness of about 40nm can be obtained on the aluminum borate whiskers. And due to the nearly continuous brittle spinel product by aluminum borate whisker and the matrix, the structure continuity of the whiskers has been greatly destroyed after the squeeze casting process. Although γ Al2O3 coating can't totally hinder the interfacial reaction, it effectively constrains the spinel reaction and preserves the structure integrity of the aluminum borate whisker.
In the present paper a sol gel γ Al2O3 coating method was employed to modify the interface properties of the aluminum borate whisker reinforced 6061Al composites. Results indicate that an alumina coating with a thickness of about 40nm can be obtained on the aluminum borate whiskers. And due to the nearly continuous brittle spinel product by aluminum borate whisker and the matrix, the structure continuity of the whiskers has been greatly destroyed after the squeeze casting process. Although γ Al2O3 coating can't totally hinder the interfacial reaction, it effectively constrains the spinel reaction and preserves the structure integrity of the aluminum borate whisker.
2000, 17(2): 38-41.
Abstract:
The A356 matrix composites reinforced by 20vol%SiC particulates were fabricated by vacuum stirring casting process. SiC particulates tend to be uniformly dispersed in the matrix. Tensile strength of the composite is 319MPa, elastic modulus is 98.9MPa, and elongation is 1.4%. Based on the test of PCD tool cutting SiC particles reinforced aluminum matrix composite, the article points out that the best total efficiency can be obtained when the cutting velocity is 30~40 m/min.
The A356 matrix composites reinforced by 20vol%SiC particulates were fabricated by vacuum stirring casting process. SiC particulates tend to be uniformly dispersed in the matrix. Tensile strength of the composite is 319MPa, elastic modulus is 98.9MPa, and elongation is 1.4%. Based on the test of PCD tool cutting SiC particles reinforced aluminum matrix composite, the article points out that the best total efficiency can be obtained when the cutting velocity is 30~40 m/min.
2000, 17(2): 42-45.
Abstract:
The microstructure and phase component of oxidation resistant MoSi2-SiC multilayer ceramic coating were observed and analyzed. The oxidation behaviour of the coated carbon/carbon composites was studied at various temperatures below 1650℃,and the activation energy of oxidation in each temperature interval was determined simultaneously. The relationship between oxidation behaviour, microstructure and component, and also, the mechanism of oxidation and the concept of the integrity of coating layer are explained from the theory of mass transportation. This analytical procedure offers a reasonable microstructure and component of the coating. The above results showed that the MoSi2-SiC ceramic coating for carbon/carbon composites has high oxidation resistance at temperature up to 1650℃.
The microstructure and phase component of oxidation resistant MoSi2-SiC multilayer ceramic coating were observed and analyzed. The oxidation behaviour of the coated carbon/carbon composites was studied at various temperatures below 1650℃,and the activation energy of oxidation in each temperature interval was determined simultaneously. The relationship between oxidation behaviour, microstructure and component, and also, the mechanism of oxidation and the concept of the integrity of coating layer are explained from the theory of mass transportation. This analytical procedure offers a reasonable microstructure and component of the coating. The above results showed that the MoSi2-SiC ceramic coating for carbon/carbon composites has high oxidation resistance at temperature up to 1650℃.
INVESTIGATION OF MICROSTRUCTURE AND FLEXURAL BEHAVIOR FOR OXIDATION PROTECTION COATED C/C COMPOSITES
2000, 17(2): 46-49.
Abstract:
Mechanical properties of MoSi2-SiC oxidation resistant coated C/C composites were investigated by three points bending tests. The microstructure of coated C/C composites and flexural fracture surface, and the interface characteristics of C/C composites were investigated; the influences of oxidation protection coating and its process on the flexural mechanical behavior of these materials were analyzed. The results showed that with the progress of the coating process, SiC conversion layer was formed in the interfaces of carbon fiber/carbon matrix and fiber bundle/matrix, and open pores or gaps existing within the composites. On the other hand, the pyro carbon matrix converted into SiC was easier than the carbon fiber. After infiltration process, the fracture behavior of C/C composite was changed. Also the correlation between microstructure and fracture behavior was discussed with the SEM results.
Mechanical properties of MoSi2-SiC oxidation resistant coated C/C composites were investigated by three points bending tests. The microstructure of coated C/C composites and flexural fracture surface, and the interface characteristics of C/C composites were investigated; the influences of oxidation protection coating and its process on the flexural mechanical behavior of these materials were analyzed. The results showed that with the progress of the coating process, SiC conversion layer was formed in the interfaces of carbon fiber/carbon matrix and fiber bundle/matrix, and open pores or gaps existing within the composites. On the other hand, the pyro carbon matrix converted into SiC was easier than the carbon fiber. After infiltration process, the fracture behavior of C/C composite was changed. Also the correlation between microstructure and fracture behavior was discussed with the SEM results.
2000, 17(2): 50-54.
Abstract:
Dense TiC-Al2O3-20Fe cermet was produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influences of pressing processes (delay time, high pressure and high pressure time) on density of TiC-Al2O3-20Fe cermets was researched. The composition, microstructure and properties of the products were analyzed. The results show that, in the process of preparing TiC-Al2O3-20Fe cermet by SHS/PHIP, the release of gases and the existence of the liquid are the important factors. The products consist of TiC and Al2O3 particles and quasi continuous Fe binder phase. The interfacial bonding between Fe and Al2O3 is very smooth. A thin diffusion layer was found between Fe and TiC. Transverse rupture strength and compressive strength are approximately 890MPa and 18.4GPa.
Dense TiC-Al2O3-20Fe cermet was produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influences of pressing processes (delay time, high pressure and high pressure time) on density of TiC-Al2O3-20Fe cermets was researched. The composition, microstructure and properties of the products were analyzed. The results show that, in the process of preparing TiC-Al2O3-20Fe cermet by SHS/PHIP, the release of gases and the existence of the liquid are the important factors. The products consist of TiC and Al2O3 particles and quasi continuous Fe binder phase. The interfacial bonding between Fe and Al2O3 is very smooth. A thin diffusion layer was found between Fe and TiC. Transverse rupture strength and compressive strength are approximately 890MPa and 18.4GPa.
2000, 17(2): 55-59.
Abstract:
Based on using the gravitational separation SHS process to produce ceramic lined pipes under the condition of mechanical vibration with different amplitudes and frequencies in a form of up down motion with one degree of freedom, the influences of mechanical vibration on SHS thermit combustion, ceramic solidification as well as structure and properties of pipes have been investigated. It was found that mechanical vibration with increasing frequency increased the combustion temperature, combustion rate and reaction transformation rate, promoted Al2O3-Fe liquid liquid phase gravitational separation and ceramic densification, and made Al2O3 dendrite crystal be changed in size and growth orientation. The results showed from mechanical tests that the various mechanical properties of pipes and surface quality of lined ceramic layers had been improved to a great extent following the mechanical vibration with increasing frequency.
Based on using the gravitational separation SHS process to produce ceramic lined pipes under the condition of mechanical vibration with different amplitudes and frequencies in a form of up down motion with one degree of freedom, the influences of mechanical vibration on SHS thermit combustion, ceramic solidification as well as structure and properties of pipes have been investigated. It was found that mechanical vibration with increasing frequency increased the combustion temperature, combustion rate and reaction transformation rate, promoted Al2O3-Fe liquid liquid phase gravitational separation and ceramic densification, and made Al2O3 dendrite crystal be changed in size and growth orientation. The results showed from mechanical tests that the various mechanical properties of pipes and surface quality of lined ceramic layers had been improved to a great extent following the mechanical vibration with increasing frequency.
2000, 17(2): 60-65.
Abstract:
A micro mechanical method is proposed to account for the influence of thermal residual stress on elastic plastic deformation of composites. The method is based on the secant moduli method with second order stress moment and the elastic micro mechanical method proposed by Ponte Castaneda and Willis. This model can account for the influence of volume fraction, shape, orientation, and distribution of inclusions on macroscopic properties of composites with or without thermal stress. Finite element calculations are also carried out for unidirectional composites and compared with the proposed model.
A micro mechanical method is proposed to account for the influence of thermal residual stress on elastic plastic deformation of composites. The method is based on the secant moduli method with second order stress moment and the elastic micro mechanical method proposed by Ponte Castaneda and Willis. This model can account for the influence of volume fraction, shape, orientation, and distribution of inclusions on macroscopic properties of composites with or without thermal stress. Finite element calculations are also carried out for unidirectional composites and compared with the proposed model.
2000, 17(2): 66-69.
Abstract:
Shear properties of the composite is studied by using the parameterized modeling technology for three dimensionally and 4 step braided composites and based on the “米” type model of a representative unit cell presented for FEM numerical prediction. First, the boundary conditions of the unit cell are discussed under shear deformation. Then, the shear moduli of the composite are predicted by FEM calculation. Finally, the relations of the shear moduli varying with different braiding angles and fiber volume fractions are concluded by analysis for the results.
Shear properties of the composite is studied by using the parameterized modeling technology for three dimensionally and 4 step braided composites and based on the “米” type model of a representative unit cell presented for FEM numerical prediction. First, the boundary conditions of the unit cell are discussed under shear deformation. Then, the shear moduli of the composite are predicted by FEM calculation. Finally, the relations of the shear moduli varying with different braiding angles and fiber volume fractions are concluded by analysis for the results.
2000, 17(2): 70-73.
Abstract:
On the basis of Mindlin first order shear effect plate theory, a linear and nonlinear finite element stability analysis method of the stiffened and non stiffened laminate plates with delamination damage under thermal and mechanical combined loading is established. The temperature dependent thermal and mechanical properties of the composites are considered. Two kinds of different thermal mechanical coupling problems have been studied. The numerical results of some typical examples are given. From numerical analysis for some typical examples, the coupling effects of the thermal mechanical loads, different delamination sizes and areas on buckling behavior of the stiffened and non stiffened plates are discussed. The numerical method and conclusions provided in the paper are useful for engineers of composite structures.
On the basis of Mindlin first order shear effect plate theory, a linear and nonlinear finite element stability analysis method of the stiffened and non stiffened laminate plates with delamination damage under thermal and mechanical combined loading is established. The temperature dependent thermal and mechanical properties of the composites are considered. Two kinds of different thermal mechanical coupling problems have been studied. The numerical results of some typical examples are given. From numerical analysis for some typical examples, the coupling effects of the thermal mechanical loads, different delamination sizes and areas on buckling behavior of the stiffened and non stiffened plates are discussed. The numerical method and conclusions provided in the paper are useful for engineers of composite structures.
2000, 17(2): 74-78.
Abstract:
Nonlinear thermal vibration of composite laminated plates has been studied by using a new generalized higher order computing model considering both the transverse normal strain and shear strains. The validity and effectiveness of the model are demonstrated by comparison with the solutions obtained by the other existent references. The effects of temperature on the curve of dimensionless nonlinear vibration frequencies vs dimensionless amplitudes are especially investigated by numerical results.
Nonlinear thermal vibration of composite laminated plates has been studied by using a new generalized higher order computing model considering both the transverse normal strain and shear strains. The validity and effectiveness of the model are demonstrated by comparison with the solutions obtained by the other existent references. The effects of temperature on the curve of dimensionless nonlinear vibration frequencies vs dimensionless amplitudes are especially investigated by numerical results.
2000, 17(2): 79-83.
Abstract:
This paper presents the concept of yarn state, solving the descriptive problem of preform structure of any 3 D woven composite. A cross equivalent curve board model is expounded, and with the help of cubic polynomial interpolation theory, the computer simulation model is developed which reflects the constitutive relation of 3 D woven composite. In addition, contrast tests are conducted to verify the model.
This paper presents the concept of yarn state, solving the descriptive problem of preform structure of any 3 D woven composite. A cross equivalent curve board model is expounded, and with the help of cubic polynomial interpolation theory, the computer simulation model is developed which reflects the constitutive relation of 3 D woven composite. In addition, contrast tests are conducted to verify the model.
2000, 17(2): 84-88.
Abstract:
The axisymmetric problem of an infinite long fiber perfectly bonded to a viscoelastic matrix which contains an annular crack surrounding the fiber is investigated for the case of tension or torsion loading. After obtaining the Laplace transformed solution from the elastic analysis, a Legendre polynomial method is used to invert the Laplace transform numerically. The time dependent stress intensity factors at the crack tips are presented. The results show that when the annular crack is away from the interface, the normalized stress intensity factors at the crack tips decrease with increasing time.
The axisymmetric problem of an infinite long fiber perfectly bonded to a viscoelastic matrix which contains an annular crack surrounding the fiber is investigated for the case of tension or torsion loading. After obtaining the Laplace transformed solution from the elastic analysis, a Legendre polynomial method is used to invert the Laplace transform numerically. The time dependent stress intensity factors at the crack tips are presented. The results show that when the annular crack is away from the interface, the normalized stress intensity factors at the crack tips decrease with increasing time.
2000, 17(2): 89-93.
Abstract:
The interface problem of composite materials has some particularity, complexity and importance. It not only is related to the processing of materials, but also has a prominent effect on the damage and failure process. In this paper, the micro deformation of a single fiber in the single fiber/epoxy composites is measured by using the laser Raman spectroscopy (LRS) technique and the micromechanics of stress transfer is investigated. From the experiment, it can be found that the average strain in fiber increases linearly with the applied strain up to 0.8%, at which the fiber occurs to fracture.
The interface problem of composite materials has some particularity, complexity and importance. It not only is related to the processing of materials, but also has a prominent effect on the damage and failure process. In this paper, the micro deformation of a single fiber in the single fiber/epoxy composites is measured by using the laser Raman spectroscopy (LRS) technique and the micromechanics of stress transfer is investigated. From the experiment, it can be found that the average strain in fiber increases linearly with the applied strain up to 0.8%, at which the fiber occurs to fracture.
2000, 17(2): 94-97.
Abstract:
According to the recent development trend and need of the frictional brake material, the 1- 2-3 model brake fraction multi material has been made out by adjusting the recipe and techniques. The mixing of two dimensional flake material vermiculite and one dimensional Kevlar fiber is used as the reinforced bulk. The modified resin is used as the basal bulk. Tests manifest that the properties of mechanics are high, and friction factors are suitable and stable. Especially in high temperatures wear is low. It is an excellent friction brake material.
According to the recent development trend and need of the frictional brake material, the 1- 2-3 model brake fraction multi material has been made out by adjusting the recipe and techniques. The mixing of two dimensional flake material vermiculite and one dimensional Kevlar fiber is used as the reinforced bulk. The modified resin is used as the basal bulk. Tests manifest that the properties of mechanics are high, and friction factors are suitable and stable. Especially in high temperatures wear is low. It is an excellent friction brake material.
2000, 17(2): 98-101.
Abstract:
A scanning electron microscope was used to observe the microstructure of the hole surfaces drilled on CFRP samples. SEM micrographs showed that some areas of the hole surface were covered with polymer while others were dominated by broken fibers. The latter increased with the increase of cutting speed. The roughness of the drilled surface also varied. The roughest parts located at the points where the fibers were fractured owing to bending shearing stresses. The broken face of each fiber was basically perpendicular to its own axis though the fibers broken by shearing appeared different with those by bending.
A scanning electron microscope was used to observe the microstructure of the hole surfaces drilled on CFRP samples. SEM micrographs showed that some areas of the hole surface were covered with polymer while others were dominated by broken fibers. The latter increased with the increase of cutting speed. The roughness of the drilled surface also varied. The roughest parts located at the points where the fibers were fractured owing to bending shearing stresses. The broken face of each fiber was basically perpendicular to its own axis though the fibers broken by shearing appeared different with those by bending.
2000, 17(2): 102-105.
Abstract:
硅钙材料具有轻质、耐火、保温诸优异性能 ,但吸水率高。吸水后 ,上述性能急剧降低。以往 ,表面涂覆或掺加憎水剂 ,效果不大而且昂贵。作者提出的全憎水化是一种全新的憎水化方法 ,即以硅藻土为载体 ,先吸附憎水剂 ,再掺入坯体中。水热处理过程中 ,憎水剂逐渐释放 ,并均匀分布于整个坯体中 ,从而获得了理想又经济的全憎水效果 (制品的重量吸水率从 330 %降到 3.9% ) ,而制品的高耐热性、高保温性、低容重仍保持不变。本文中给出了材料、掺量选择和基本性能的实验结果 ,探讨了全憎水化机理 ,并分析了效益与前景。
硅钙材料具有轻质、耐火、保温诸优异性能 ,但吸水率高。吸水后 ,上述性能急剧降低。以往 ,表面涂覆或掺加憎水剂 ,效果不大而且昂贵。作者提出的全憎水化是一种全新的憎水化方法 ,即以硅藻土为载体 ,先吸附憎水剂 ,再掺入坯体中。水热处理过程中 ,憎水剂逐渐释放 ,并均匀分布于整个坯体中 ,从而获得了理想又经济的全憎水效果 (制品的重量吸水率从 330 %降到 3.9% ) ,而制品的高耐热性、高保温性、低容重仍保持不变。本文中给出了材料、掺量选择和基本性能的实验结果 ,探讨了全憎水化机理 ,并分析了效益与前景。
2000, 17(2): 106-110.
Abstract:
Dispersive particles can be obtained with internal oxidation, but the distribution of the particles in the matrix is not uniform and the material is not dense. This article deals with the plastic deformation of Al2O3/Cu composites, and the recrystallization of the deformed composites. The experiments and analyses show that the material has a high work hardening coefficient, the dispersoid can obviously improve the recrystallization temperature of the composites, and thus the mechanical properties of the composites are increased greatly.
Dispersive particles can be obtained with internal oxidation, but the distribution of the particles in the matrix is not uniform and the material is not dense. This article deals with the plastic deformation of Al2O3/Cu composites, and the recrystallization of the deformed composites. The experiments and analyses show that the material has a high work hardening coefficient, the dispersoid can obviously improve the recrystallization temperature of the composites, and thus the mechanical properties of the composites are increased greatly.
2000, 17(2): 111-113.
Abstract:
Three dimensional finite element analysis with COMEP code was carried out on a plain weave glassfiber composite under tensile loading. A typical microscopic stress state and some significant characters were revealed from the results.
Three dimensional finite element analysis with COMEP code was carried out on a plain weave glassfiber composite under tensile loading. A typical microscopic stress state and some significant characters were revealed from the results.
2000, 17(2): 114-118.
Abstract:
Pure bending tests after low velocity impact and quasi static transverse indentation tests were carried out on composite Nomex honeycomb core sandwich panels. Methods of X ray, deply and visual inspection were used to measure the damage in specimens. Bending failure behavior was studied on the sandwich panels, in which the impacted face sheet was compressed and another face sheet tensioned. The damage caused by transverse indention was compared with that by low velocity impact. The damage and rules of contact force P against indent displacement Δ h were discussed at different transverse indent speeds. Results showed that the bending strength of honeycomb core sandwich panels was reduced extensively by low velocity impact and that the Nomex honeycomb core sandwich panels were not sensitive to transverse indent speed.
Pure bending tests after low velocity impact and quasi static transverse indentation tests were carried out on composite Nomex honeycomb core sandwich panels. Methods of X ray, deply and visual inspection were used to measure the damage in specimens. Bending failure behavior was studied on the sandwich panels, in which the impacted face sheet was compressed and another face sheet tensioned. The damage caused by transverse indention was compared with that by low velocity impact. The damage and rules of contact force P against indent displacement Δ h were discussed at different transverse indent speeds. Results showed that the bending strength of honeycomb core sandwich panels was reduced extensively by low velocity impact and that the Nomex honeycomb core sandwich panels were not sensitive to transverse indent speed.
2000, 17(2): 119-122.
Abstract:
A thermal vibration test for orthotropic, cross ply and antisymmetric laminated plates has been done in this paper respectively, and the valuable testing results are in good agreement with the nonlinear high order laminated theory which was proposed by the author.
A thermal vibration test for orthotropic, cross ply and antisymmetric laminated plates has been done in this paper respectively, and the valuable testing results are in good agreement with the nonlinear high order laminated theory which was proposed by the author.
