2003 Vol. 20, No. 2
2003, 20(2): 1-6.
Abstract:
As an innovative curing technology conforming to the developing trend of low cost and nuisance free, the electron beam (EB) curing of composites has been receiving extensive attention in recent years. Many works about fundamental research of EB curing should be done to promote its development. The effects of reinforce fiber on electron beam curing process and curing degree of epoxy resin matrix were studied in the paper. The results of observing the cured areas indicate that the obvious interspace exists around the fiber in the cured mixture of untreated carbon fiber and epoxy resins. After the carbon fiber was treated with acid, the combination at interface of fiber and resin matrix is improved in the radiated samples. The curing degree in the cured samples containing fiber decreases with the radiation depth, unlike the top curing degree that occurs at some depth instead of the radiated surface in the neat resin system. When the reinforce fibers are mixed with resin, the thickness of the radiation-cured area and curing degree decrease. The effect of carbon fiber is more obvious than that of glass fiber.
As an innovative curing technology conforming to the developing trend of low cost and nuisance free, the electron beam (EB) curing of composites has been receiving extensive attention in recent years. Many works about fundamental research of EB curing should be done to promote its development. The effects of reinforce fiber on electron beam curing process and curing degree of epoxy resin matrix were studied in the paper. The results of observing the cured areas indicate that the obvious interspace exists around the fiber in the cured mixture of untreated carbon fiber and epoxy resins. After the carbon fiber was treated with acid, the combination at interface of fiber and resin matrix is improved in the radiated samples. The curing degree in the cured samples containing fiber decreases with the radiation depth, unlike the top curing degree that occurs at some depth instead of the radiated surface in the neat resin system. When the reinforce fibers are mixed with resin, the thickness of the radiation-cured area and curing degree decrease. The effect of carbon fiber is more obvious than that of glass fiber.
2003, 20(2): 7-12.
Abstract:
By adding several micro-step absorbing particles, a satisfactory absorbing property can be obtained. According to the absorbing level of 10 dB, the effective absorbing band of a plane-boarded specimen is about 10 GHz. The test of the dynamic mechanical property of non-standard specimens shows that this kind of structural absorbing composite has a higher resist-impact property; however, the stationary mechanical property of standard specimens is low compared with traditional material.
By adding several micro-step absorbing particles, a satisfactory absorbing property can be obtained. According to the absorbing level of 10 dB, the effective absorbing band of a plane-boarded specimen is about 10 GHz. The test of the dynamic mechanical property of non-standard specimens shows that this kind of structural absorbing composite has a higher resist-impact property; however, the stationary mechanical property of standard specimens is low compared with traditional material.
2003, 20(2): 13-18.
Abstract:
All specimens of MoS2 and carbon fiber reinforced polyamide 1010(PA1010) composites were prepared by a micro injection machine. The friction coefficient and wear rate of composites were investigated with the ring-block test rig. The results show that hybrid fillers can considerably improve the tribological properties of PA1010 composites under dry sliding friction conditions. The dominant wear mechanisms of composites were abrasive wear and fatigue wear at a low normal pressure; the fatigue cracking and peeling due to thermal effect resulted in the severe wear of composites with the increase of normal pressure. The tribochemical reactions between MoS2 and counterface Fe were found to generate FeS2 and FeSO4 which were more effective to promote the adhesive strength to the counterpart, and also MoS2 was partially oxidized to MoO3 during sliding.
All specimens of MoS2 and carbon fiber reinforced polyamide 1010(PA1010) composites were prepared by a micro injection machine. The friction coefficient and wear rate of composites were investigated with the ring-block test rig. The results show that hybrid fillers can considerably improve the tribological properties of PA1010 composites under dry sliding friction conditions. The dominant wear mechanisms of composites were abrasive wear and fatigue wear at a low normal pressure; the fatigue cracking and peeling due to thermal effect resulted in the severe wear of composites with the increase of normal pressure. The tribochemical reactions between MoS2 and counterface Fe were found to generate FeS2 and FeSO4 which were more effective to promote the adhesive strength to the counterpart, and also MoS2 was partially oxidized to MoO3 during sliding.
2003, 20(2): 19-24.
Abstract:
The prepreg of continuous glass fiber reinforced PP was prepared by using powder impregnation process and cut into the pellets of long fiber reinforced PP. The compression molding process of such long fiber reinforced PP was investigated. The mechanical properties and their influential factors of the products were also studied. It was found that the parts with an excellent mechanical property could be obtained after the powder impregnating long fiber reinforced PP was compression molded. With the increment in the cut length of the prepreg and fiber content, the mechanical property increased. The modification of the interfacial adhesion between glass fiber and PP by using functionalized polypropylene grafted polar group (MPP) played a significant role in improving the mechanical properties of the composites, but the impact strength decreased above a certain level of MPP. The mechanical properties would increase when increasing the molding pressure and the temperature of mould and molding compound during the compression molding processing.
The prepreg of continuous glass fiber reinforced PP was prepared by using powder impregnation process and cut into the pellets of long fiber reinforced PP. The compression molding process of such long fiber reinforced PP was investigated. The mechanical properties and their influential factors of the products were also studied. It was found that the parts with an excellent mechanical property could be obtained after the powder impregnating long fiber reinforced PP was compression molded. With the increment in the cut length of the prepreg and fiber content, the mechanical property increased. The modification of the interfacial adhesion between glass fiber and PP by using functionalized polypropylene grafted polar group (MPP) played a significant role in improving the mechanical properties of the composites, but the impact strength decreased above a certain level of MPP. The mechanical properties would increase when increasing the molding pressure and the temperature of mould and molding compound during the compression molding processing.
2003, 20(2): 25-29.
Abstract:
Carbon nanotubes (CNTs) were prepared by the catalytic floating method in a vertical furnace. They were compounded with acrylonitrile-butadiene-styrene (ABS) after surface treatment. The tensile strength and modulus of the CNTs/ABS composite had increased greatly, but the impact strength had decreased for addition of CNTs. The tensile strength increased from 45.00 MPa to 69.96 MPa, modulus from 0.75 GPa to 1.93 GPa when the content of CNTs in composite increased from 0 wt% to 12 wt%. The radar absorbing property of the CNTs/ABS composite was also studied, and it was found that the composite material exhibited the radar absorbing property in some band range.
Carbon nanotubes (CNTs) were prepared by the catalytic floating method in a vertical furnace. They were compounded with acrylonitrile-butadiene-styrene (ABS) after surface treatment. The tensile strength and modulus of the CNTs/ABS composite had increased greatly, but the impact strength had decreased for addition of CNTs. The tensile strength increased from 45.00 MPa to 69.96 MPa, modulus from 0.75 GPa to 1.93 GPa when the content of CNTs in composite increased from 0 wt% to 12 wt%. The radar absorbing property of the CNTs/ABS composite was also studied, and it was found that the composite material exhibited the radar absorbing property in some band range.
2003, 20(2): 30-34.
Abstract:
Effects of curing agents and curing conditions on the intercalation and exfoliation behavior of epoxy/clay nanocomposites were investigated. Five curing agents used were DETA,DDM,DMP-30 and two modified amines. The curing degree and distance between layers of the clay were measured by FT-IR , XRD and TEM respectively. It was found that epoxy resin is easy to intercalate the clay,but clay exfoliation in epoxy resin was dependent more on the curing conditions than on the curing agents. When the curing speed of epoxy resin interlayers is faster than that of extralayers and fully reaches curing, exfoliation easily takes place, and epoxy/clay nanocomposites can be prepared.
Effects of curing agents and curing conditions on the intercalation and exfoliation behavior of epoxy/clay nanocomposites were investigated. Five curing agents used were DETA,DDM,DMP-30 and two modified amines. The curing degree and distance between layers of the clay were measured by FT-IR , XRD and TEM respectively. It was found that epoxy resin is easy to intercalate the clay,but clay exfoliation in epoxy resin was dependent more on the curing conditions than on the curing agents. When the curing speed of epoxy resin interlayers is faster than that of extralayers and fully reaches curing, exfoliation easily takes place, and epoxy/clay nanocomposites can be prepared.
2003, 20(2): 35-40.
Abstract:
One of the main factors to influence the interfacial properties of composites is the surface characteristics of the aramid fiber. Ultrasound is used to treat the surface of the aramid fiber and the change of surface structure of the aramid fiber under the ultrasonic treatment is investigated in this paper. The results show that the content of polar group and the specific surface area increase so as to improve the wettability between the aramid fiber and epoxy resin.
One of the main factors to influence the interfacial properties of composites is the surface characteristics of the aramid fiber. Ultrasound is used to treat the surface of the aramid fiber and the change of surface structure of the aramid fiber under the ultrasonic treatment is investigated in this paper. The results show that the content of polar group and the specific surface area increase so as to improve the wettability between the aramid fiber and epoxy resin.
2003, 20(2): 41-46.
Abstract:
Interfacial reactions mechanism between SiO2 grain and Al-Mg matrix is investigated, and20wt% SiO2/Al-Mg composites were fabricated by powder metallurgy. As a result, MgAl2O4, MgO, Mg2Si and a little Al and Si were created in formerly SiO2 grain. MgAl2O4 is in an all irregular shape, and MgAl2O 4 is closed about Al. The structure of MgO, Mg2Si and Si is slice layer. There is no SiO2 in the formerly SiO2 grain, which shows that whole SiO2 had been reacted with Al-Mg matrix by 620℃sinter for 30min. Si created by reaction of SiO2 and Al-Mg matrix was pushed into Al-Mg matrix. There are Al, Si and Mg2Si in the matrix. Mg2Si is in a grain shape, its size being smaller than 0.2μm. There is no simple Mg in the matrix because the Mg there had been reacted to form Mg2Si.
Interfacial reactions mechanism between SiO2 grain and Al-Mg matrix is investigated, and20wt% SiO2/Al-Mg composites were fabricated by powder metallurgy. As a result, MgAl2O4, MgO, Mg2Si and a little Al and Si were created in formerly SiO2 grain. MgAl2O4 is in an all irregular shape, and MgAl2O 4 is closed about Al. The structure of MgO, Mg2Si and Si is slice layer. There is no SiO2 in the formerly SiO2 grain, which shows that whole SiO2 had been reacted with Al-Mg matrix by 620℃sinter for 30min. Si created by reaction of SiO2 and Al-Mg matrix was pushed into Al-Mg matrix. There are Al, Si and Mg2Si in the matrix. Mg2Si is in a grain shape, its size being smaller than 0.2μm. There is no simple Mg in the matrix because the Mg there had been reacted to form Mg2Si.
2003, 20(2): 47-52.
Abstract:
Monolithic mesoporous CdS/SiO2 assembly systems were obtained by sol-gel technique. The characteristic peaks of CdS in Raman spectrum were observed at room temperature. The as-prepared samples were annealed under air and nitrogen, respectively. It is observed that the absorption edge of the CdS/SiO2 shifts in comparison with that of the bulk CdS as the annealing temperature change as well as the loading of CdS in SiO2. The calculating result showed that the size of CdS particles in the mesoporous SiO2 is similar to its exciton radius on quantity. The shift of the absorption edge was attributed to the quantum size effect.
Monolithic mesoporous CdS/SiO2 assembly systems were obtained by sol-gel technique. The characteristic peaks of CdS in Raman spectrum were observed at room temperature. The as-prepared samples were annealed under air and nitrogen, respectively. It is observed that the absorption edge of the CdS/SiO2 shifts in comparison with that of the bulk CdS as the annealing temperature change as well as the loading of CdS in SiO2. The calculating result showed that the size of CdS particles in the mesoporous SiO2 is similar to its exciton radius on quantity. The shift of the absorption edge was attributed to the quantum size effect.
2003, 20(2): 53-57.
Abstract:
The cross-linking and pyrolysis of hydrogen-containing polysiloxane(PSO) and divinylbenzene(DVB) were investigated in this paper. It was found that only catalyzed with H2PtCl6 could DVB/PSO cure completely. The mass ratio of DVB/PSO had a great effect on ceramic yield. The ceramic yield was the highest of 76 % when the mass ratio of DVB/PSO was 0.5. The content of Si, O, C in the product pyrolyzed at 1000 ℃ was 38.3 wt%, 27.4 wt%, and 34.3 wt%, respectively. Three-dimensional carbon fiber reinforced silicon oxycarbide composites (3D-B Cf/Si-O-C) were fabricated via precursor infiltration and pyrolysis using DVB/PSO as a precursor. The results indicated that the mechanical properties of 3D-B Cf/Si-O-C could be increased markedly if the first pyrolysis cycle was assisted by hot-pressing. The flexural strength and the fracture toughness of the composite, which was hot-pressed at 1600 ℃ for 5 min with a pressure of 10 MPa in the first pyrolysis cycle and treated subsequently with six cycles of vacuum infiltration and pyrolysis with a pressure of 1 atm, were 502 MPa and 23.7 MPa·m1/2, respectively. The high properties were mainly attributed to the ideal interface microstructures.
The cross-linking and pyrolysis of hydrogen-containing polysiloxane(PSO) and divinylbenzene(DVB) were investigated in this paper. It was found that only catalyzed with H2PtCl6 could DVB/PSO cure completely. The mass ratio of DVB/PSO had a great effect on ceramic yield. The ceramic yield was the highest of 76 % when the mass ratio of DVB/PSO was 0.5. The content of Si, O, C in the product pyrolyzed at 1000 ℃ was 38.3 wt%, 27.4 wt%, and 34.3 wt%, respectively. Three-dimensional carbon fiber reinforced silicon oxycarbide composites (3D-B Cf/Si-O-C) were fabricated via precursor infiltration and pyrolysis using DVB/PSO as a precursor. The results indicated that the mechanical properties of 3D-B Cf/Si-O-C could be increased markedly if the first pyrolysis cycle was assisted by hot-pressing. The flexural strength and the fracture toughness of the composite, which was hot-pressed at 1600 ℃ for 5 min with a pressure of 10 MPa in the first pyrolysis cycle and treated subsequently with six cycles of vacuum infiltration and pyrolysis with a pressure of 1 atm, were 502 MPa and 23.7 MPa·m1/2, respectively. The high properties were mainly attributed to the ideal interface microstructures.
2003, 20(2): 58-63.
Abstract:
Al2O3/Ni composites were prepared by hot-pressing from Ni-coated Al2O3. In this paper, the effect of sintering temperature on densification, phase compositions and microstructure was mainly studied. The relation curve of relative densities and sintering temperature showed the composites obtained the maximum relative density at 1400℃, and the relative densities decreased with Ni content increasing. Phase analysis indicated the new phase composed of Al, Ni, O, C was produced on the surface layer of the sintered body besides Al2O3 and Ni when the temperature was higher than 1350℃. As observed from TEM images, the agglomerated and grown Ni particles were located at the triangle boundary at 1300℃;when sintering temperature was 1400℃, most large Ni particles were seated at the grain boundary and a small number of nano-Ni particles were located within Al2O3 grain; and at 1450℃, the interspace existed at the interface of Al2O3/Ni and the exaggerated growth of Al2O3 grain was found.
Al2O3/Ni composites were prepared by hot-pressing from Ni-coated Al2O3. In this paper, the effect of sintering temperature on densification, phase compositions and microstructure was mainly studied. The relation curve of relative densities and sintering temperature showed the composites obtained the maximum relative density at 1400℃, and the relative densities decreased with Ni content increasing. Phase analysis indicated the new phase composed of Al, Ni, O, C was produced on the surface layer of the sintered body besides Al2O3 and Ni when the temperature was higher than 1350℃. As observed from TEM images, the agglomerated and grown Ni particles were located at the triangle boundary at 1300℃;when sintering temperature was 1400℃, most large Ni particles were seated at the grain boundary and a small number of nano-Ni particles were located within Al2O3 grain; and at 1450℃, the interspace existed at the interface of Al2O3/Ni and the exaggerated growth of Al2O3 grain was found.
2003, 20(2): 64-70.
Abstract:
On the basis of experimental data, a densification rate mode to describe the woven preform deposited in the thermal gradient CVI process was put forward. It was found to be fit to the index densification equation which was usually used to describe the kinetic process that organic molecules filled in pores of substrate as well as in the ICVI process. Simultaneously, it was also found that the thermal gradient field and the directional flow field of input gas within the deposited preform could largely raise the densification rate of the preform, for they can accelerate the diffusion rate of filled molecules and reduce the surface crust formation of the preform in the thermal gradient CVI process.
On the basis of experimental data, a densification rate mode to describe the woven preform deposited in the thermal gradient CVI process was put forward. It was found to be fit to the index densification equation which was usually used to describe the kinetic process that organic molecules filled in pores of substrate as well as in the ICVI process. Simultaneously, it was also found that the thermal gradient field and the directional flow field of input gas within the deposited preform could largely raise the densification rate of the preform, for they can accelerate the diffusion rate of filled molecules and reduce the surface crust formation of the preform in the thermal gradient CVI process.
2003, 20(2): 71-75.
Abstract:
According to the character of primary QI impurities composed of carbonaceous particles with the size of several micrometers, the coal tar was purified by the solvent flocculation method. Using the purified tar as raw material, high performance impregnating pitch with low QI content was prepared. The rheologic behavior and permeability of high performance impregnating pitch were comparatively studied. It has been confirmed that the high performance impregnating pitch modifies greatly impregnation efficiency. The mechanical characteristics of C/C composite have been evidently improved.
According to the character of primary QI impurities composed of carbonaceous particles with the size of several micrometers, the coal tar was purified by the solvent flocculation method. Using the purified tar as raw material, high performance impregnating pitch with low QI content was prepared. The rheologic behavior and permeability of high performance impregnating pitch were comparatively studied. It has been confirmed that the high performance impregnating pitch modifies greatly impregnation efficiency. The mechanical characteristics of C/C composite have been evidently improved.
2003, 20(2): 76-80.
Abstract:
In the 3-D braiding procedure, the braiding yarn is tended to move along the direction of its carrier movement. Based on the movement of carriers, this paper presents a control region method to analyze the yarn traces systematically in 4-step 3-d tubular braided preforms. Then, four interior cells and two surface cells are established. For the whole structure of the preform, it can be assembled by these unit cells. The geometry of each cell is deeply dependent on its position in the cross-section of the preform. All cells are oriented in the same reference frame as the preform, which is quite suitable for the analysis of the mechanical properties.
In the 3-D braiding procedure, the braiding yarn is tended to move along the direction of its carrier movement. Based on the movement of carriers, this paper presents a control region method to analyze the yarn traces systematically in 4-step 3-d tubular braided preforms. Then, four interior cells and two surface cells are established. For the whole structure of the preform, it can be assembled by these unit cells. The geometry of each cell is deeply dependent on its position in the cross-section of the preform. All cells are oriented in the same reference frame as the preform, which is quite suitable for the analysis of the mechanical properties.
2003, 20(2): 81-87.
Abstract:
On the basis of the relatively true microstructure, utilizing the method of piling up the unit cells, the relationships between geometric structure parameters and braiding process parameters are derived in this paper in order to provide the dependable theoretical formula foundation for practical process design. At the same time, some experiments are used to test and verify the accuracy of the relationships between the geometric parameters and the braiding process parameters effectively.
On the basis of the relatively true microstructure, utilizing the method of piling up the unit cells, the relationships between geometric structure parameters and braiding process parameters are derived in this paper in order to provide the dependable theoretical formula foundation for practical process design. At the same time, some experiments are used to test and verify the accuracy of the relationships between the geometric parameters and the braiding process parameters effectively.
2003, 20(2): 88-93.
Abstract:
The fiber reinforced plastic shells with honeycomb sandwich are commonly applied to space structures. To describe the structures' behavior and connect laminate with 3D brick elements better, a kind of 32 nodes and 3 layers shell element with relative-freedom is presented based on the 3D FEM. To eliminate the discontinuity of the interlaminar stress and satisfy the load boundary conditions, a method for computing interlaminar stresses is presented also. 3D brick elements combined with 32 nodes and 3 layers shell elements are applied for modeling complex structures such as laminated composite shells with variable thickness or reinforcements. Numerical examples indicate that the results obtained by the present method are satisfying.
The fiber reinforced plastic shells with honeycomb sandwich are commonly applied to space structures. To describe the structures' behavior and connect laminate with 3D brick elements better, a kind of 32 nodes and 3 layers shell element with relative-freedom is presented based on the 3D FEM. To eliminate the discontinuity of the interlaminar stress and satisfy the load boundary conditions, a method for computing interlaminar stresses is presented also. 3D brick elements combined with 32 nodes and 3 layers shell elements are applied for modeling complex structures such as laminated composite shells with variable thickness or reinforcements. Numerical examples indicate that the results obtained by the present method are satisfying.
2003, 20(2): 94-99.
Abstract:
Taking into account the effect of temperature dependency of material properties,the transient temperature fields in the plate made of a functionally gradient material that consists of ZrO2 and Ti-6Al-4V under convective heat transfer boundary are analyzed by the finite element method(FEM)and the finite difference method (FDM). At the same time,the accuracy of this method is examined.Finally, the transient temperature field distributions under the convective heat transfer boundary are obtained and compared with the results of temperature-independent properties. From the numerical results it can be seen that the temperature dependency of the material properties is one of the most important factors in the accurate evaluation of the temperature. In addition, the temperature distribu-tions are substantially changed with the change of the temperature of the surrounding and the parameter M and the convective heat transfer coefficients.The results of this paper provide the foundations of calculation for material design and further thermal stress analysis.
Taking into account the effect of temperature dependency of material properties,the transient temperature fields in the plate made of a functionally gradient material that consists of ZrO2 and Ti-6Al-4V under convective heat transfer boundary are analyzed by the finite element method(FEM)and the finite difference method (FDM). At the same time,the accuracy of this method is examined.Finally, the transient temperature field distributions under the convective heat transfer boundary are obtained and compared with the results of temperature-independent properties. From the numerical results it can be seen that the temperature dependency of the material properties is one of the most important factors in the accurate evaluation of the temperature. In addition, the temperature distribu-tions are substantially changed with the change of the temperature of the surrounding and the parameter M and the convective heat transfer coefficients.The results of this paper provide the foundations of calculation for material design and further thermal stress analysis.
2003, 20(2): 100-105.
Abstract:
The elastic modulus of polypropylene/polystyrene (PP/PS) blend was predicted by means of meso-mechanics of composite materials. Based upon the systematical studies of the effects of composition and mixing time on the elastic modulus and morphology of immiscible blends PP/PS, the relation of microscopic morphology and macroscopic mechanical property was discussed. Tensile tests showed that the meso-mechanical models were valid for the prediction of elastic modulus, and Mori-Tanaka model would be a more effective method for designing materials in comparison with Halpin-Tsai model and modified mixture model because there is no restriction on the experimental parameters.
The elastic modulus of polypropylene/polystyrene (PP/PS) blend was predicted by means of meso-mechanics of composite materials. Based upon the systematical studies of the effects of composition and mixing time on the elastic modulus and morphology of immiscible blends PP/PS, the relation of microscopic morphology and macroscopic mechanical property was discussed. Tensile tests showed that the meso-mechanical models were valid for the prediction of elastic modulus, and Mori-Tanaka model would be a more effective method for designing materials in comparison with Halpin-Tsai model and modified mixture model because there is no restriction on the experimental parameters.
2003, 20(2): 106-111.
Abstract:
A random spring model is used to simulate mesoscopic fracture processes in cement-based composites. The 3-D spatial distribution of aggregate inclusions is modeled based on a given grading and gravel content in the composite. The 2-D space of the cement matrix and interfacial zone is divided into small elements using the concept of Voronoi polygons. Both the elements and aggregate inclusions are assumed to be rigid bodies connected by the normal and tangential springs. Numerical results are given for a fracture test of concrete CT specimens and concrete cube specimen under uniaxial compression, and useful information concerning the mesoscopic behavior of the failure process is obtained.
A random spring model is used to simulate mesoscopic fracture processes in cement-based composites. The 3-D spatial distribution of aggregate inclusions is modeled based on a given grading and gravel content in the composite. The 2-D space of the cement matrix and interfacial zone is divided into small elements using the concept of Voronoi polygons. Both the elements and aggregate inclusions are assumed to be rigid bodies connected by the normal and tangential springs. Numerical results are given for a fracture test of concrete CT specimens and concrete cube specimen under uniaxial compression, and useful information concerning the mesoscopic behavior of the failure process is obtained.
2003, 20(2): 112-117.
Abstract:
Functionally gradient materials(FGM)have complex meso-scopic structure,so it is the main developing direction to investigate the properties of FGM by using the method of meso-scopic mechanics. An analysis on the meso-scopic structure and property of uneven hot-resistant FGM with spheroid inclusions was introduced in this paper.A meso-scopic mechanical model was established. The research includes the damage evolution and failure of FGM.The result was applied to the meso-scopic stress analysis and properties prediction of multi-phase inclusions FGM. For the convenience of engineering application, all result was provided in explicit forms.
Functionally gradient materials(FGM)have complex meso-scopic structure,so it is the main developing direction to investigate the properties of FGM by using the method of meso-scopic mechanics. An analysis on the meso-scopic structure and property of uneven hot-resistant FGM with spheroid inclusions was introduced in this paper.A meso-scopic mechanical model was established. The research includes the damage evolution and failure of FGM.The result was applied to the meso-scopic stress analysis and properties prediction of multi-phase inclusions FGM. For the convenience of engineering application, all result was provided in explicit forms.
2003, 20(2): 118-122.
Abstract:
Applying fast electric heating techniques, the ultra-high temperature condition of hybrid carbon-carbon composites in practice is simulated. Then its tensile and compressive mechanical properties are measured, both strength and modulus in the longitudinal and the transverse directions of composites are obtained, and simple regressive polynomial fit curves are given also. Results show that both strength and modulus increase with temperature in a certain range, and get the peak at 2000K~2400K, and drop quickly after 2700K. Furthermore, tensile and compressive properties in the longitudinal direction change flatter than those in the transverse direction, and also the strength changes in a narrower range than the modulus.
Applying fast electric heating techniques, the ultra-high temperature condition of hybrid carbon-carbon composites in practice is simulated. Then its tensile and compressive mechanical properties are measured, both strength and modulus in the longitudinal and the transverse directions of composites are obtained, and simple regressive polynomial fit curves are given also. Results show that both strength and modulus increase with temperature in a certain range, and get the peak at 2000K~2400K, and drop quickly after 2700K. Furthermore, tensile and compressive properties in the longitudinal direction change flatter than those in the transverse direction, and also the strength changes in a narrower range than the modulus.
