2006 Vol. 23, No. 6
2006, 23(6): 1-8.
Abstract:
In this paper , research on permeability prediction in RTM process is reviewed based on the study report sin this area both at home and abroad. Several classical models in the analytical method and numerical method aresystematically discussed. The numerical methods applied in permeability prediction are elaborated. The existingproblems in models are also analyzed. A comparison is made between the models to evaluate their respective disadvantages. This article gives a description of the capillary model and regular cylinder model for permeability prediction of unidirectional reinforcement s in details. It also report s the numerical method for permeability prediction ofunidirectional reinforcement s and woven preforms focusing on the asymptotic homogenization method , Lattice-Boltzman method and cell method. The study for permeability estimation of fiber is mainly reviewed based on experimentation at home , the relationship between fiber st ructure and permeability parameter is analyzed , and the effect ofpermeability on resin t ransfer molding progress is studied. Af ter a brief review of the current problems in this arearecent development s and new t rends of research are also described.
In this paper , research on permeability prediction in RTM process is reviewed based on the study report sin this area both at home and abroad. Several classical models in the analytical method and numerical method aresystematically discussed. The numerical methods applied in permeability prediction are elaborated. The existingproblems in models are also analyzed. A comparison is made between the models to evaluate their respective disadvantages. This article gives a description of the capillary model and regular cylinder model for permeability prediction of unidirectional reinforcement s in details. It also report s the numerical method for permeability prediction ofunidirectional reinforcement s and woven preforms focusing on the asymptotic homogenization method , Lattice-Boltzman method and cell method. The study for permeability estimation of fiber is mainly reviewed based on experimentation at home , the relationship between fiber st ructure and permeability parameter is analyzed , and the effect ofpermeability on resin t ransfer molding progress is studied. Af ter a brief review of the current problems in this arearecent development s and new t rends of research are also described.
2006, 23(6): 9-13.
Abstract:
Permeability of the three- dimensional braiding preform was measured by radial flow techniques. Thepermeability values were calculated by an iterative approach of the modified inlet radii. These iterations are conveniently performed based on a procedure with Visual C + + . The orientation of the principal permeability tensor wasobtained according to the following steps. Firstly , the flow f ront was ext racted via an image processing algorithm ofselecting a threshold. Secondly , the flow f ront ellipse was fitted by using the nonlinear least squares curve fittingalgorithm in Matlab. The orientation between ellipse major and braiding axes was calculated in Matlab. The result sshow that braided parameters influence the permeability. The principal permeability decreases with increasing thefiber volume fraction when the braiding angle is constant , and it also decreases with increasing the braiding anglewhen the fiber volume f raction is constant . However , the orientation of the principal permeability does not vary withthe braiding angle , and it keep s on coinciding with their braiding direction.
Permeability of the three- dimensional braiding preform was measured by radial flow techniques. Thepermeability values were calculated by an iterative approach of the modified inlet radii. These iterations are conveniently performed based on a procedure with Visual C + + . The orientation of the principal permeability tensor wasobtained according to the following steps. Firstly , the flow f ront was ext racted via an image processing algorithm ofselecting a threshold. Secondly , the flow f ront ellipse was fitted by using the nonlinear least squares curve fittingalgorithm in Matlab. The orientation between ellipse major and braiding axes was calculated in Matlab. The result sshow that braided parameters influence the permeability. The principal permeability decreases with increasing thefiber volume fraction when the braiding angle is constant , and it also decreases with increasing the braiding anglewhen the fiber volume f raction is constant . However , the orientation of the principal permeability does not vary withthe braiding angle , and it keep s on coinciding with their braiding direction.
2006, 23(6): 14-20.
Abstract:
The nano-CaCO3 / PP composites modified by four kinds of compatibilizers were prepared respectively.The crystallization and melting behavior of PP - base composites were investigated using DSC and WXRD. Theresult s indicate that the addition of nano-CaCO3 increases the crystallization temperature of PP and induces the formation ofβ-PP crystal due to the heterogeneous nucleation of nano-CaCO3 . The heterogeneous nucleation of PP-g-AAand PP-g-MA is also observed for PP crystallization. The synergism of heterogeneous nucleation of nano-CaCO3and PP-g-AA ( PP-g-MA or POE-g-MA) further increases the crystallization and melting temperatures of nano-CaCO3 / PP composites. Addition of PP-g-MA and POE-g-MA induces the formation of moreβ2PP crystal in nano-CaCO3 / PP composites. However , addition of EVA-g-MA decreases the heterogeneous nucleation of nano-CaCO3 .The result s suggest that the heterogeneous nucleation of PP in nano-CaCO3 / PP composites depends on the interfacial interaction between nano-CaCO3 and PP , which is influenced by compatibilizers.
The nano-CaCO3 / PP composites modified by four kinds of compatibilizers were prepared respectively.The crystallization and melting behavior of PP - base composites were investigated using DSC and WXRD. Theresult s indicate that the addition of nano-CaCO3 increases the crystallization temperature of PP and induces the formation ofβ-PP crystal due to the heterogeneous nucleation of nano-CaCO3 . The heterogeneous nucleation of PP-g-AAand PP-g-MA is also observed for PP crystallization. The synergism of heterogeneous nucleation of nano-CaCO3and PP-g-AA ( PP-g-MA or POE-g-MA) further increases the crystallization and melting temperatures of nano-CaCO3 / PP composites. Addition of PP-g-MA and POE-g-MA induces the formation of moreβ2PP crystal in nano-CaCO3 / PP composites. However , addition of EVA-g-MA decreases the heterogeneous nucleation of nano-CaCO3 .The result s suggest that the heterogeneous nucleation of PP in nano-CaCO3 / PP composites depends on the interfacial interaction between nano-CaCO3 and PP , which is influenced by compatibilizers.
2006, 23(6): 21-28.
Abstract:
The aim is to study the effect s of dynamic mechanics properties and geomet rical parameters of each layermaterial on the sound absorption properties of the multilayered polymer composites. A three-dimensional transfermat rix model was presented to simulate the sound absorption coefficient s of the composites. Numerical calculationsfor the composites at normal incident were compared with the experimental result s. It is shown that the calculatedresult s are in agreement with the experimental result s. Based on the three-dimensional t ransfer mat rix model , studies were made to understand the effect s of the geomet rical and physical parameters of each layer materials on thesound absorption properties of composite st ructures. The result s show that the material thickness , modulus , lossfactor and Poisson’s ratio have evident effect s on the sound absorption properties of the composite st ructures. Andthe effect s of the exterior layer material parameters on the sound absorption properties of composite st ructures arelarger than those of the interior layer material parameters on the sound absorption properties.
The aim is to study the effect s of dynamic mechanics properties and geomet rical parameters of each layermaterial on the sound absorption properties of the multilayered polymer composites. A three-dimensional transfermat rix model was presented to simulate the sound absorption coefficient s of the composites. Numerical calculationsfor the composites at normal incident were compared with the experimental result s. It is shown that the calculatedresult s are in agreement with the experimental result s. Based on the three-dimensional t ransfer mat rix model , studies were made to understand the effect s of the geomet rical and physical parameters of each layer materials on thesound absorption properties of composite st ructures. The result s show that the material thickness , modulus , lossfactor and Poisson’s ratio have evident effect s on the sound absorption properties of the composite st ructures. Andthe effect s of the exterior layer material parameters on the sound absorption properties of composite st ructures arelarger than those of the interior layer material parameters on the sound absorption properties.
2006, 23(6): 29-36.
Abstract:
This study explored the feasibility and potential benefit s provided by the addition of through-thicknessstitched composite closed -cell foam sandwich st ructures. For comparison purposes , unstitched foam and Nomexhoneycomb core sandwich panels were produced using the same face sheet s and manufacturing methodology. Thedensity measurements , flexural testing , flatwise tensile and compression , core shear , edgewise compression , anddamage resistance/ damage tolerance test s were performed. The experimental result s show significant increasing inthe flexural stiffness to mass ratio , flexural st rength to mass ratio , out-of-plane tensile and compression st rength ,core shear st rength and modulus , edgewise compression st rength and CAI st rength and failure st rain of the stitchedfoam sandwich st ructures. This innovative concept of stitched foam sandwich st ructures may be utilized in theaircraf t design of lightweight and low-cost st ructures with higher load-carrying capability , lower manufacturing andmaintaining cost .
This study explored the feasibility and potential benefit s provided by the addition of through-thicknessstitched composite closed -cell foam sandwich st ructures. For comparison purposes , unstitched foam and Nomexhoneycomb core sandwich panels were produced using the same face sheet s and manufacturing methodology. Thedensity measurements , flexural testing , flatwise tensile and compression , core shear , edgewise compression , anddamage resistance/ damage tolerance test s were performed. The experimental result s show significant increasing inthe flexural stiffness to mass ratio , flexural st rength to mass ratio , out-of-plane tensile and compression st rength ,core shear st rength and modulus , edgewise compression st rength and CAI st rength and failure st rain of the stitchedfoam sandwich st ructures. This innovative concept of stitched foam sandwich st ructures may be utilized in theaircraf t design of lightweight and low-cost st ructures with higher load-carrying capability , lower manufacturing andmaintaining cost .
2006, 23(6): 37-45.
Abstract:
Glass2fiber cored lead-net ( GF-Pb net) reinforced rubber composites ( GF-Pb/ R) with different st ructures and different interfaces were prepared. And their dynamic properties were studied within 3～20 Hz by testingtheir hysteresis loop s. It tells that the dynamic mechanical property and damping property of GF-Pb/ R are improvedsimultaneously. The increasing ratios of dynamic properties of GF- Pb net vertically reinforced rubber composite(V- GF-Pb/ R) are higher than those of GF- Pb net horizontally reinforced rubber composite ( H- GF- Pb/ R) . Andthe increasing ratios of dynamic stiffness and damping loss factor are 49 % and 25 % for V- GF- Pb/ R with theGF-Pb net volume f raction of 4 %. It is concluded that the damping of GF- Pb/ Rresults from material damping ,micro-slippage damping and damping f rom micro-plastic deformation of lead. The interface bond st rength influencesthe mechanical property and the damping behavior of GF- Pb/ R remarkably. The dynamic stiffness of GF-Pb/ Rincreases with increasing the interface bond st rength. However , the loss factor is a maximum when the interfacebond st rength is between weak bond and st rong bond.
Glass2fiber cored lead-net ( GF-Pb net) reinforced rubber composites ( GF-Pb/ R) with different st ructures and different interfaces were prepared. And their dynamic properties were studied within 3～20 Hz by testingtheir hysteresis loop s. It tells that the dynamic mechanical property and damping property of GF-Pb/ R are improvedsimultaneously. The increasing ratios of dynamic properties of GF- Pb net vertically reinforced rubber composite(V- GF-Pb/ R) are higher than those of GF- Pb net horizontally reinforced rubber composite ( H- GF- Pb/ R) . Andthe increasing ratios of dynamic stiffness and damping loss factor are 49 % and 25 % for V- GF- Pb/ R with theGF-Pb net volume f raction of 4 %. It is concluded that the damping of GF- Pb/ Rresults from material damping ,micro-slippage damping and damping f rom micro-plastic deformation of lead. The interface bond st rength influencesthe mechanical property and the damping behavior of GF- Pb/ R remarkably. The dynamic stiffness of GF-Pb/ Rincreases with increasing the interface bond st rength. However , the loss factor is a maximum when the interfacebond st rength is between weak bond and st rong bond.
2006, 23(6): 46-51.
Abstract:
Quasi-static and high st rain rate compressive experiment s on the vinyl ester resin casting were carriedout by using a material universal testing machine and Hopkinson bar , and the behaviors of compressive instabilityand f racture of the resin casting at different st rain rates were investigated. The result s indicate that the response behavior of the resin casting is cont rolled by different mechanisms at different st rain rates and some mechanical properties of vinyl ester casting are rate-dependent : the castings are dest royed in a toughness mode at st rain rate 3. 3 ×10-4 / s～6. 6 ×10 -3 / s , while the castings are dest royed in a brittleness mode at st rain rate 950/ s～5800/ s. Theyield st ress , yield st rain energy density are all increased with the increasing of st rain rates under quasi-static loadingas well as under high st rain rates loading. What is interesting is that the yield st rain is decreased with the st rain rateincreasing under quasi-static loadings while it is increased under high st rain rate loadings. It is considered that in thecasting there occurred forced high elastic deformation at high st rain rates. The damage of the specimens is mainlycont rolled by axial st ress before unstable deformation , while mainly cont rolled by shear stress after unstable deformation , and then all f racture finally. The development of the cracks inside the castings is also rate-dependent .
Quasi-static and high st rain rate compressive experiment s on the vinyl ester resin casting were carriedout by using a material universal testing machine and Hopkinson bar , and the behaviors of compressive instabilityand f racture of the resin casting at different st rain rates were investigated. The result s indicate that the response behavior of the resin casting is cont rolled by different mechanisms at different st rain rates and some mechanical properties of vinyl ester casting are rate-dependent : the castings are dest royed in a toughness mode at st rain rate 3. 3 ×10-4 / s～6. 6 ×10 -3 / s , while the castings are dest royed in a brittleness mode at st rain rate 950/ s～5800/ s. Theyield st ress , yield st rain energy density are all increased with the increasing of st rain rates under quasi-static loadingas well as under high st rain rates loading. What is interesting is that the yield st rain is decreased with the st rain rateincreasing under quasi-static loadings while it is increased under high st rain rate loadings. It is considered that in thecasting there occurred forced high elastic deformation at high st rain rates. The damage of the specimens is mainlycont rolled by axial st ress before unstable deformation , while mainly cont rolled by shear stress after unstable deformation , and then all f racture finally. The development of the cracks inside the castings is also rate-dependent .
2006, 23(6): 52-56.
Abstract:
The longitudinal tensile and compression test s were conducted on the pre-damaged three-dimensionalbraided composites. The varying rules of tensile and compressive properties and the failure mechanism of the materials were investigated. Four kinds of damage processes were discussed , single-edge cut on the width , single-edgecut on the thickness , double-edge cut on the width and edge cut on the thickness and width. Experimental resultsreveal that the cut edge on the width of specimen barely affects the longitudinal properties , except that the compressive modulus deduces by 20 %; while cut on the thickness makes a relatively great deduction on the properties.When the surface angle is 20°, stress-strain curves of tension and compression tend to linearity , and the failuremechanism has brittle f racture characteristics ; when the surface angle is 35°, the stress-strain curves of compressionexpress non-linearity to some extent .
The longitudinal tensile and compression test s were conducted on the pre-damaged three-dimensionalbraided composites. The varying rules of tensile and compressive properties and the failure mechanism of the materials were investigated. Four kinds of damage processes were discussed , single-edge cut on the width , single-edgecut on the thickness , double-edge cut on the width and edge cut on the thickness and width. Experimental resultsreveal that the cut edge on the width of specimen barely affects the longitudinal properties , except that the compressive modulus deduces by 20 %; while cut on the thickness makes a relatively great deduction on the properties.When the surface angle is 20°, stress-strain curves of tension and compression tend to linearity , and the failuremechanism has brittle f racture characteristics ; when the surface angle is 35°, the stress-strain curves of compressionexpress non-linearity to some extent .
2006, 23(6): 57-63.
Abstract:
A novel nano-silica surface-modified by silane was used as a reinforcing filler for HTV (heat vulcanization) silicone rubber. The dispersion morphologies and network st ructure of the composites were analysed by scanning elect ronic microscopy (SEM) and Payne effect ; the crystal behavior at low temperature was studied by differential scanning calorimet ry(DSC) . And the effect of these fillers on the mechanical properties of silicone rubber was investigated. Because the surface of these nanoparticles was enwrapped by apolar methyl , they can disperse in therubber perfectly without adding any dispersant . The result s indicate that at respective optimum content , the catenarian nano-silica (DNS-3) has evidently better reinforcement to silicone rubber in the tensile st rength , tear st rengthand elongation at break than the silica nanoparticle synthesized by aerosol method (A-200) . The DNS-2 nano-silicahas a similar reinforcing effect to nanO2silica compared with A-200 , but the gross rubber of the DNS-2 system wassof ter and has better processability than that of A-200.
A novel nano-silica surface-modified by silane was used as a reinforcing filler for HTV (heat vulcanization) silicone rubber. The dispersion morphologies and network st ructure of the composites were analysed by scanning elect ronic microscopy (SEM) and Payne effect ; the crystal behavior at low temperature was studied by differential scanning calorimet ry(DSC) . And the effect of these fillers on the mechanical properties of silicone rubber was investigated. Because the surface of these nanoparticles was enwrapped by apolar methyl , they can disperse in therubber perfectly without adding any dispersant . The result s indicate that at respective optimum content , the catenarian nano-silica (DNS-3) has evidently better reinforcement to silicone rubber in the tensile st rength , tear st rengthand elongation at break than the silica nanoparticle synthesized by aerosol method (A-200) . The DNS-2 nano-silicahas a similar reinforcing effect to nanO2silica compared with A-200 , but the gross rubber of the DNS-2 system wassof ter and has better processability than that of A-200.
2006, 23(6): 64-68.
Abstract:
Resin mat rix composites are of ten used with metallic materials. The unidirectional laminate was fabricated by a filament wound method. The Fiber Bragg Grating ( FBG) was embedded between filament wound compositelamination and aluminum plate to monitor the interface performance of two different materials during the cureprocess , and it was compared with the result s f rom the internal composite monitoring. The result s show that thetemperature evolution of the composite cure process was monitored exactly by the Fiber Bragg Grating ; it was foundthat there is an obvious difference between the st rains before and af ter the curing process. The Fiber Bragg Gratingprovides a tool to monitor the cure process between two different materials and a new method to analyze the interfaceperformance.
Resin mat rix composites are of ten used with metallic materials. The unidirectional laminate was fabricated by a filament wound method. The Fiber Bragg Grating ( FBG) was embedded between filament wound compositelamination and aluminum plate to monitor the interface performance of two different materials during the cureprocess , and it was compared with the result s f rom the internal composite monitoring. The result s show that thetemperature evolution of the composite cure process was monitored exactly by the Fiber Bragg Grating ; it was foundthat there is an obvious difference between the st rains before and af ter the curing process. The Fiber Bragg Gratingprovides a tool to monitor the cure process between two different materials and a new method to analyze the interfaceperformance.
2006, 23(6): 69-74.
Abstract:
The modified poly (p2phenylene benzoxazole) ( PBO) containing ionic groups in polymer chains (sulfonatedpoly p - phenylene benzoxazole , SPBO) was obtained by copolymerization from 1 , 3 - diamino -4 , 6 -dihydroxybenzenedihydrochloride (DAR) and terephthalic acid ( TPA) , with addition of certain amount s of 52sulfoisophthalicacid monosodium salt in replace of TPA , in polyphosphoric acid. The SPBO fiber was obtained for the first timethrough a dry-jet wet-spinning technique. After incorporation of ionic groups into PBO macromolecular chains , thewetting properties of PBO fiber are improved. The contact angles of water and ethanol on PBO fiber surface decreasef rom 71. 4°and 37. 2°to 66. 3°and 30. 6°respectively. And the surface f ree energy of SPBO fiber increases tO38. 9 mJ·m- 2 , which is 9. 6 % higher than that of PBO fiber. XPS analysis shows that the surface nit rogen-to-carbon ratio is increased f rom 0. 0157 to 0. 0471 and oxygen2tO2carbon ratio is increased f rom 0. 2331 to 0. 3070 , andthe ionization energy (or binding energy) of C1s and O1s decreases. The interfacial shear st rength ( IFSS) was determined by the microbond pull out test . The int roduction of ionic group s leads to a 23 % increase in IFSS f rom8. 2 MPa for PBO/ epoxy to 10. 1 MPa for SPBO/ epoxy. In addition , the surface morphology of the pull-outed PBOand SPBO fibers was observed by scanning elect ron microscopy. It is found that the failure mode changed f romfiber/ mat rix interface adhesive failure to partly cohesive failure mode.
The modified poly (p2phenylene benzoxazole) ( PBO) containing ionic groups in polymer chains (sulfonatedpoly p - phenylene benzoxazole , SPBO) was obtained by copolymerization from 1 , 3 - diamino -4 , 6 -dihydroxybenzenedihydrochloride (DAR) and terephthalic acid ( TPA) , with addition of certain amount s of 52sulfoisophthalicacid monosodium salt in replace of TPA , in polyphosphoric acid. The SPBO fiber was obtained for the first timethrough a dry-jet wet-spinning technique. After incorporation of ionic groups into PBO macromolecular chains , thewetting properties of PBO fiber are improved. The contact angles of water and ethanol on PBO fiber surface decreasef rom 71. 4°and 37. 2°to 66. 3°and 30. 6°respectively. And the surface f ree energy of SPBO fiber increases tO38. 9 mJ·m- 2 , which is 9. 6 % higher than that of PBO fiber. XPS analysis shows that the surface nit rogen-to-carbon ratio is increased f rom 0. 0157 to 0. 0471 and oxygen2tO2carbon ratio is increased f rom 0. 2331 to 0. 3070 , andthe ionization energy (or binding energy) of C1s and O1s decreases. The interfacial shear st rength ( IFSS) was determined by the microbond pull out test . The int roduction of ionic group s leads to a 23 % increase in IFSS f rom8. 2 MPa for PBO/ epoxy to 10. 1 MPa for SPBO/ epoxy. In addition , the surface morphology of the pull-outed PBOand SPBO fibers was observed by scanning elect ron microscopy. It is found that the failure mode changed f romfiber/ mat rix interface adhesive failure to partly cohesive failure mode.
2006, 23(6): 75-79.
Abstract:
In order to improve the st rength of the quartz fiber/ SiO2 composite , and escape the reduction of themechanical property by crystallization of the quartz fiber , the crystallization is studied in detail. The chemical bondst ructure of the quartz fiber was examined by FT-IR , and the crystallization process of the quartz fiber was analyzedby DSC and XRD. The crystallization photograph and production were observed by SEM and TEM. The resultsindicate that there are some Si —OH bonds in the quartz fiber and the crystallization process is cont rolled by st ructure rearrangement which can be seen in the DSC curve. The crystallization start s at 950 ℃ and get s to the top at1400 ℃. The XRD result shows that the product is onlyα-cristobalite , and the beginning temperature is lower thanthat of the bulk quartz glass. The Si —OH bond , impurity and phase interface are the important factors for the crystallization temperature of the quartz fiber to be lower than that of the quartz glass.
In order to improve the st rength of the quartz fiber/ SiO2 composite , and escape the reduction of themechanical property by crystallization of the quartz fiber , the crystallization is studied in detail. The chemical bondst ructure of the quartz fiber was examined by FT-IR , and the crystallization process of the quartz fiber was analyzedby DSC and XRD. The crystallization photograph and production were observed by SEM and TEM. The resultsindicate that there are some Si —OH bonds in the quartz fiber and the crystallization process is cont rolled by st ructure rearrangement which can be seen in the DSC curve. The crystallization start s at 950 ℃ and get s to the top at1400 ℃. The XRD result shows that the product is onlyα-cristobalite , and the beginning temperature is lower thanthat of the bulk quartz glass. The Si —OH bond , impurity and phase interface are the important factors for the crystallization temperature of the quartz fiber to be lower than that of the quartz glass.
2006, 23(6): 80-85.
Abstract:
A wear resistant metal silicide composite consisting of Cr13Ni5Si2 ternary metal silicide dendrites and thenickel-base solid solution (γ) mat rix (Cr13Ni5Si2 /γ) was designed and fabricated by the laser melting/ continuousdeposition process. High - temperature sliding wear resistance as a function of wear test temperature and high -temperature sliding wear mechanisms of the Cr13Ni5Si2 /γ composite were studied. The result s indicate that theCr13Ni5Si2 /γ composite has excellent wear resistance , low temperature-sensitivity of wear and anomalous wear-temperature dependence under high-temperature sliding wear test conditions due to the st rong atomic binding forces andanomalous hardness - temperature dependence of Cr13Ni5Si2 , good toughness and st rength of the Cr13Ni5Si2 /γcomposite and the t ransferred cover-layer on the worn surface of the Cr13Ni5Si2 /γ composite during the high-temperature sliding wear process. The wear resistance of the Cr13Ni5Si2 ternary metal silicide at 600 ℃was improved tO4 times by adding a ductileγ-Ni mat rix.
A wear resistant metal silicide composite consisting of Cr13Ni5Si2 ternary metal silicide dendrites and thenickel-base solid solution (γ) mat rix (Cr13Ni5Si2 /γ) was designed and fabricated by the laser melting/ continuousdeposition process. High - temperature sliding wear resistance as a function of wear test temperature and high -temperature sliding wear mechanisms of the Cr13Ni5Si2 /γ composite were studied. The result s indicate that theCr13Ni5Si2 /γ composite has excellent wear resistance , low temperature-sensitivity of wear and anomalous wear-temperature dependence under high-temperature sliding wear test conditions due to the st rong atomic binding forces andanomalous hardness - temperature dependence of Cr13Ni5Si2 , good toughness and st rength of the Cr13Ni5Si2 /γcomposite and the t ransferred cover-layer on the worn surface of the Cr13Ni5Si2 /γ composite during the high-temperature sliding wear process. The wear resistance of the Cr13Ni5Si2 ternary metal silicide at 600 ℃was improved tO4 times by adding a ductileγ-Ni mat rix.
2006, 23(6): 86-91.
Abstract:
The wear resistant Mo/ Mo2Ni3 Si metal silicide alloys consisting of ref ractory metal molybdenum primarydendrites toughening phase and interdendritic Mo2Ni3 Si ternary metal silicide mat rix were designed and fabricated bythe laser melt deposition process with molybdenum , nickel and silicon elemental powder as the raw materials.Microst ructures of the alloys were characterized by optical microscopy (OM) , scanning elect ron microscopy (SEM) ,X2ray diff raction (XRD) and energy dispersive spect roscopy ( EDS) . The volume f raction of molybdenum primarydendrites increases with increasing of the molybdenum atomic f raction in the raw material , while the hardness of thealloy decreases as increasing the molybdenum atomic f raction in the raw material. Wear resistance of the laser meltdeposited Mo/ Mo2Ni3 Si metal silicide alloys was evaluated under dry sliding wear test conditions at room temperature. The result s indicate that Mo/ Mo2Ni3 Si metal silicide alloys have out standing wear resistance because of theexcellent combination of high st rength and ductility of the ref ractory metal molybdenum primary dendrites and thehigh hardness and st rong atomic bonds of the Mo2Ni3 Si ternary metal silicide.
The wear resistant Mo/ Mo2Ni3 Si metal silicide alloys consisting of ref ractory metal molybdenum primarydendrites toughening phase and interdendritic Mo2Ni3 Si ternary metal silicide mat rix were designed and fabricated bythe laser melt deposition process with molybdenum , nickel and silicon elemental powder as the raw materials.Microst ructures of the alloys were characterized by optical microscopy (OM) , scanning elect ron microscopy (SEM) ,X2ray diff raction (XRD) and energy dispersive spect roscopy ( EDS) . The volume f raction of molybdenum primarydendrites increases with increasing of the molybdenum atomic f raction in the raw material , while the hardness of thealloy decreases as increasing the molybdenum atomic f raction in the raw material. Wear resistance of the laser meltdeposited Mo/ Mo2Ni3 Si metal silicide alloys was evaluated under dry sliding wear test conditions at room temperature. The result s indicate that Mo/ Mo2Ni3 Si metal silicide alloys have out standing wear resistance because of theexcellent combination of high st rength and ductility of the ref ractory metal molybdenum primary dendrites and thehigh hardness and st rong atomic bonds of the Mo2Ni3 Si ternary metal silicide.
2006, 23(6): 92-97.
Abstract:
A multilayer amorphous Ni-P composite coating with a potential difference above 160mV was preparedin the same bath by varying the temperature , p H value and elect ric field alternately. The anti-corrosion behavior ofthe composite coating was studied in the environment with H2S and CO2 , and the result s show that the terraceamorphous Ni-P composite coating performed well in corrosion-resistance in the environment with H2S and CO2 .An even corrosive film formed on the surface of the composite terrace coating af ter 100h. Corrosive cracks appearedon the composite coating’s surface af ter 300h , and the cracks expanded along the parallel direction of the base. Theenrichment of phosphorus occurred in the places where the elect rodeposited coating was deprived. The corrosion results indicated that this multilayer Ni2P coating of 12μm thickness possessed better anti-corrosion properties thanthe plain elect roless coating of 25μm.
A multilayer amorphous Ni-P composite coating with a potential difference above 160mV was preparedin the same bath by varying the temperature , p H value and elect ric field alternately. The anti-corrosion behavior ofthe composite coating was studied in the environment with H2S and CO2 , and the result s show that the terraceamorphous Ni-P composite coating performed well in corrosion-resistance in the environment with H2S and CO2 .An even corrosive film formed on the surface of the composite terrace coating af ter 100h. Corrosive cracks appearedon the composite coating’s surface af ter 300h , and the cracks expanded along the parallel direction of the base. Theenrichment of phosphorus occurred in the places where the elect rodeposited coating was deprived. The corrosion results indicated that this multilayer Ni2P coating of 12μm thickness possessed better anti-corrosion properties thanthe plain elect roless coating of 25μm.
2006, 23(6): 98-102.
Abstract:
SiCP reinforced aluminum mat rix composites were t reated by microarc oxidation method. The micro-structure and composition of ceramic film were analyzed , and the phase constituent and microhardness profile werealso measured. The corrosion behavior of the composite was evaluated by polarization test . The ceramic film deposi2ted in silicate elect rolyte consist s of mullite ,α-Al2O3 , γ-Al2O3 and amorphous SiO2 phases. A few residual SiCParticles were remained in the film close to the film/ composite interface. The silicon content in the outer layer film israther high , which mainly comes f rom the elect rolyte , while the mullite synthesis in the inner layer film is related tothe oxidation of SiC reinforcement s in the plasma discharge channel. Af ter the microarc oxidation surface t reatment ,the corrosion resistance of the SiCP/ 2024 composite was significantly improved due to the formation of a continuousthick film.
SiCP reinforced aluminum mat rix composites were t reated by microarc oxidation method. The micro-structure and composition of ceramic film were analyzed , and the phase constituent and microhardness profile werealso measured. The corrosion behavior of the composite was evaluated by polarization test . The ceramic film deposi2ted in silicate elect rolyte consist s of mullite ,α-Al2O3 , γ-Al2O3 and amorphous SiO2 phases. A few residual SiCParticles were remained in the film close to the film/ composite interface. The silicon content in the outer layer film israther high , which mainly comes f rom the elect rolyte , while the mullite synthesis in the inner layer film is related tothe oxidation of SiC reinforcement s in the plasma discharge channel. Af ter the microarc oxidation surface t reatment ,the corrosion resistance of the SiCP/ 2024 composite was significantly improved due to the formation of a continuousthick film.
2006, 23(6): 103-107.
Abstract:
The effect s of volume f raction of alumina silicate short fibers in crystal and their length on micro yieldbehaviors of Al2O3-SiO2 ( sf) / Al2Si metal mat rix composites (MMCs) fabricated with squeezing cast were investigated by continuous loading on an Inst ron5569 tester with measuring installation of accuracy 10 - 7 . It is shown that themicro yield st rength of the MMCs decreases while the macro yield st rength and Youngps modulus increase when thevolume f raction of alumina silicate short fibers increases and the micro yield strength of the MMCs decreases whilethe macro yield st rength increases when the length of the short fibers in crystal increases.
The effect s of volume f raction of alumina silicate short fibers in crystal and their length on micro yieldbehaviors of Al2O3-SiO2 ( sf) / Al2Si metal mat rix composites (MMCs) fabricated with squeezing cast were investigated by continuous loading on an Inst ron5569 tester with measuring installation of accuracy 10 - 7 . It is shown that themicro yield st rength of the MMCs decreases while the macro yield st rength and Youngps modulus increase when thevolume f raction of alumina silicate short fibers increases and the micro yield strength of the MMCs decreases whilethe macro yield st rength increases when the length of the short fibers in crystal increases.
2006, 23(6): 108-113.
Abstract:
The SiCP preformed compact was prepared by Powder Injection Molding ( PIM) , and the melting aluminum penet rated into the SiCP preformed compact by the pressure infilt ration method to manufacture the elect ronicpackage box of SiCP (65 %) / Al composites. SiCP (65 %) / Al composite manufactured by pressure infilt ration has highdensity and homogeneous microst ructure. The density of the composite is 2. 98 g/ cm3 ; the thermal expansion coefficient and thermal conductivity of the composite are 8. 0 ×10 -6 / K and nearly 130 W/ (m·K) at room temperature ,respectively , which is up to the request of the elect ronic package.
The SiCP preformed compact was prepared by Powder Injection Molding ( PIM) , and the melting aluminum penet rated into the SiCP preformed compact by the pressure infilt ration method to manufacture the elect ronicpackage box of SiCP (65 %) / Al composites. SiCP (65 %) / Al composite manufactured by pressure infilt ration has highdensity and homogeneous microst ructure. The density of the composite is 2. 98 g/ cm3 ; the thermal expansion coefficient and thermal conductivity of the composite are 8. 0 ×10 -6 / K and nearly 130 W/ (m·K) at room temperature ,respectively , which is up to the request of the elect ronic package.
2006, 23(6): 114-119.
Abstract:
Effect s of subst rate temperature on flattening morphologies of NiCrCoAlY and zirconia droplets in plasmaspraying metal mat rix composites were studied by analyzing and comparing SEM micrographs. The result s showthat when depositing on the non-preheated polished stainless steel subst rate , the NiCrCoAl Y splat s are in disk-likeshape with piled edges and splashed fragments , which have inevitably influence on the following flattening droplets.If the subst rate is preheated up to 200 ℃, the piled edges and splashed fragments within NiCrCoAl Y splatsdecrease , and the flattening behavior of the following droplet s is improved. The zirconia splat morphology on thenon-preheated polished stainless steel subst rate is round in shape with crack and finger prolongation. The number ofcracks and finger prolongations reduces correspondingly with increasing the subst rate temperature. Furthermore ,when the subst rate is preheated up to 200 ℃, NiCrCoAlY coating porosity changes unapparently while the zirconiacoating porosity reduces profoundly.
Effect s of subst rate temperature on flattening morphologies of NiCrCoAlY and zirconia droplets in plasmaspraying metal mat rix composites were studied by analyzing and comparing SEM micrographs. The result s showthat when depositing on the non-preheated polished stainless steel subst rate , the NiCrCoAl Y splat s are in disk-likeshape with piled edges and splashed fragments , which have inevitably influence on the following flattening droplets.If the subst rate is preheated up to 200 ℃, the piled edges and splashed fragments within NiCrCoAl Y splatsdecrease , and the flattening behavior of the following droplet s is improved. The zirconia splat morphology on thenon-preheated polished stainless steel subst rate is round in shape with crack and finger prolongation. The number ofcracks and finger prolongations reduces correspondingly with increasing the subst rate temperature. Furthermore ,when the subst rate is preheated up to 200 ℃, NiCrCoAlY coating porosity changes unapparently while the zirconiacoating porosity reduces profoundly.
2006, 23(6): 120-126.
Abstract:
The effect s of Ag on the microstr ucture and mechanical and electrical proper ties of Cu2 Fe in2situ com2posit es were investigated. Four in2situ composites, Cu2 12 wt%Fe, Cu2 14 wt%Fe2 1 wt%Ag, Cu2 14 wt%Fe2 3 wt%Agand Cu2 11 wt%Fe2 6 wt%Ag were prepared by the cast and drawn process. T he ult imate tensile st rength and elec2tr ical resistivity of the composites at each draw ratio wer e measur ed. T he microstructure evolution of the compositeswas investigated using scanning electr on micr oscopy ( SEM) and dist ribution of Fe and Ag in the matrix was ana2lyzed by EDS equipped on SEM. The results show that the presence of Ag can refine the primar y Fe dendrites andreduce the solution of Fe in Cu at high temper ature as well, which leads to the simult aneous increment in bothst rength and conduct ivit y. H owever, the Cu2 Fe2 Ag composites show a bit lower plasticity and the fr act ur e surfacesexhibit shear character istic at a lower dr aw r atio.
The effect s of Ag on the microstr ucture and mechanical and electrical proper ties of Cu2 Fe in2situ com2posit es were investigated. Four in2situ composites, Cu2 12 wt%Fe, Cu2 14 wt%Fe2 1 wt%Ag, Cu2 14 wt%Fe2 3 wt%Agand Cu2 11 wt%Fe2 6 wt%Ag were prepared by the cast and drawn process. T he ult imate tensile st rength and elec2tr ical resistivity of the composites at each draw ratio wer e measur ed. T he microstructure evolution of the compositeswas investigated using scanning electr on micr oscopy ( SEM) and dist ribution of Fe and Ag in the matrix was ana2lyzed by EDS equipped on SEM. The results show that the presence of Ag can refine the primar y Fe dendrites andreduce the solution of Fe in Cu at high temper ature as well, which leads to the simult aneous increment in bothst rength and conduct ivit y. H owever, the Cu2 Fe2 Ag composites show a bit lower plasticity and the fr act ur e surfacesexhibit shear character istic at a lower dr aw r atio.
2006, 23(6): 127-133.
Abstract:
The influence of ext rusion temperature on the tensile properties of 15 vol % SiCP / Mg-9Al composite produced by powder ext rusion was investigated. The result s show that between 350～450 ℃, the mechanical propertiesof the composite such as tensile st rength , yield st rength and elongation increase with the increase of the ext rusiontemperature. At the same time , with the increase of ext rusion temperature the f racture mode changes from particle/mat rix debonding to particle f racture.
The influence of ext rusion temperature on the tensile properties of 15 vol % SiCP / Mg-9Al composite produced by powder ext rusion was investigated. The result s show that between 350～450 ℃, the mechanical propertiesof the composite such as tensile st rength , yield st rength and elongation increase with the increase of the ext rusiontemperature. At the same time , with the increase of ext rusion temperature the f racture mode changes from particle/mat rix debonding to particle f racture.
2006, 23(6): 134-137.
Abstract:
Ti3SiC2 / Al nanocomposite was prepared by using the powder metallurgy method. The result s indicatethat the conformation of the mixture has a significant difference with the milling ball. The particle size of Ti3SiC2 will be decreased to about 100 nm and the particles dist ribute homogeneously in the aluminum powder prepared withzirconia balls , whereas the conglomeration will be formed using steel balls and agate balls. Bulk homogeneousTi3SiC2 / Al nanocomposite can be synthesized by hot -pressing the mixed powder under a pressure of 20 MPa at550 ℃. Compared with the popular Ti3SiC2 / Al composite , the Ti3SiC2 / Al nanocomposite has a significant improvement in hardness (from HV 60 to HV 80) and st rength (from 110 MPa to 150 MPa) .
Ti3SiC2 / Al nanocomposite was prepared by using the powder metallurgy method. The result s indicatethat the conformation of the mixture has a significant difference with the milling ball. The particle size of Ti3SiC2 will be decreased to about 100 nm and the particles dist ribute homogeneously in the aluminum powder prepared withzirconia balls , whereas the conglomeration will be formed using steel balls and agate balls. Bulk homogeneousTi3SiC2 / Al nanocomposite can be synthesized by hot -pressing the mixed powder under a pressure of 20 MPa at550 ℃. Compared with the popular Ti3SiC2 / Al composite , the Ti3SiC2 / Al nanocomposite has a significant improvement in hardness (from HV 60 to HV 80) and st rength (from 110 MPa to 150 MPa) .
2006, 23(6): 138-143.
Abstract:
Using phenolic resin as the raw material , complex-shaped component s , which were composed of SiC , Cand Si , were formed by stereolithography technology. X-ray diff raction was employed to analyze the phase of carbontemplates and ceramic components. The pyrolysis behaviors and the forming mechanism of the porous system werestudied with thermo-gravimet ric analysis. The microst ructures of the ceramic component s were observed with scanning elect ron microscope. A model of the mechanism of reactive infilt ration of Si into the carbon template was built .The carbon templates obtained by the pyrolysis of phenolic resin precursor possess amorphous state st ructures , andthe residual carbon is 65 wt %. The ceramic component s obtained at 1500 ℃ by reactive infilt ration of Si are denseceramics containing SiC , C and Si. At 1650 ℃the ceramics are porous ceramics. The porous system formed by photocurable resin st ructures and starch powders could effectively prevent the carbon templates from breaking andcracking and facilitate penet rating Si to the carbon templates to form SiC. The thickness of SiC obtained at 1500 ℃for 30 min is 20μm.
Using phenolic resin as the raw material , complex-shaped component s , which were composed of SiC , Cand Si , were formed by stereolithography technology. X-ray diff raction was employed to analyze the phase of carbontemplates and ceramic components. The pyrolysis behaviors and the forming mechanism of the porous system werestudied with thermo-gravimet ric analysis. The microst ructures of the ceramic component s were observed with scanning elect ron microscope. A model of the mechanism of reactive infilt ration of Si into the carbon template was built .The carbon templates obtained by the pyrolysis of phenolic resin precursor possess amorphous state st ructures , andthe residual carbon is 65 wt %. The ceramic component s obtained at 1500 ℃ by reactive infilt ration of Si are denseceramics containing SiC , C and Si. At 1650 ℃the ceramics are porous ceramics. The porous system formed by photocurable resin st ructures and starch powders could effectively prevent the carbon templates from breaking andcracking and facilitate penet rating Si to the carbon templates to form SiC. The thickness of SiC obtained at 1500 ℃for 30 min is 20μm.
2006, 23(6): 144-148.
Abstract:
Si/ SiC coatings were prepared on C/ SiC composites by a slurry-precoating reaction process. The slurrycomponent s with which non-cracked coatings were prepared were concluded through theoretical calculation and experiment s. The effects of powder embedded sintering and vapor silicon vacuum-reaction-sintering atmosphere on themorphology and components of the Si/ SiC coatings were studied. The effect s of single-coating-process (SCP) anddouble-coating-process (DCP) on the st ructure of the subst rate were compared. The micrographs of the coatingswere observed by SEM. The component s and crystal st ructure of the coatings were analyzed by XRD. The result sshow that the non-cracked coatings prepared with slurry in which the mass ratio of C∶Si is 1∶1. 25 and the coatingsprepared by vapor silicon vacuum- reaction- sintering are dense and st rongly bonded with the subst rate , while thecoatings prepared by powder embedded sintering become powder. The st ructure of the subst rate becomes denserthan the coatings prepared by SCP , while the subst rate remaines porous af ter being coated by DCP.
Si/ SiC coatings were prepared on C/ SiC composites by a slurry-precoating reaction process. The slurrycomponent s with which non-cracked coatings were prepared were concluded through theoretical calculation and experiment s. The effects of powder embedded sintering and vapor silicon vacuum-reaction-sintering atmosphere on themorphology and components of the Si/ SiC coatings were studied. The effect s of single-coating-process (SCP) anddouble-coating-process (DCP) on the st ructure of the subst rate were compared. The micrographs of the coatingswere observed by SEM. The component s and crystal st ructure of the coatings were analyzed by XRD. The result sshow that the non-cracked coatings prepared with slurry in which the mass ratio of C∶Si is 1∶1. 25 and the coatingsprepared by vapor silicon vacuum- reaction- sintering are dense and st rongly bonded with the subst rate , while thecoatings prepared by powder embedded sintering become powder. The st ructure of the subst rate becomes denserthan the coatings prepared by SCP , while the subst rate remaines porous af ter being coated by DCP.
2006, 23(6): 149-157.
Abstract:
Twenty standard bond specimens of GFRP rod were tested under monotonic load and cyclic load to studythe changes of bond st rength , the slip at the loaded end , unloading stiffness and hysteretic energy dissipation. Theresult s indicate that the GFRP rod does not exhibit steady bond behavior under constant stress reversals (Δτ=017τu ) , and the bond st rength of the specimens subjected to variable st ress reversals degrades significantly as cyclesincrease. The envelop curves and the common-point curves show basically the same profile as thoseτ s curves fromthe monotonic static test . The ratios of the bond st resses in the common-point curves to those in the envelop curvesat the same slip range f rom 0. 50 to 0. 75. More serious damage can be observed around the ribs of the GFRP rod inthe specimens after stress reversals than those subjected to monotonic static test . No splitting cracks can be seen inthe concrete. From the investigation of the slip at the loaded end , hysteretic energy dissipation and unloading stiffness asreversals increase , the load history and accumulative damage status were found to be the two key influencing factors.
Twenty standard bond specimens of GFRP rod were tested under monotonic load and cyclic load to studythe changes of bond st rength , the slip at the loaded end , unloading stiffness and hysteretic energy dissipation. Theresult s indicate that the GFRP rod does not exhibit steady bond behavior under constant stress reversals (Δτ=017τu ) , and the bond st rength of the specimens subjected to variable st ress reversals degrades significantly as cyclesincrease. The envelop curves and the common-point curves show basically the same profile as thoseτ s curves fromthe monotonic static test . The ratios of the bond st resses in the common-point curves to those in the envelop curvesat the same slip range f rom 0. 50 to 0. 75. More serious damage can be observed around the ribs of the GFRP rod inthe specimens after stress reversals than those subjected to monotonic static test . No splitting cracks can be seen inthe concrete. From the investigation of the slip at the loaded end , hysteretic energy dissipation and unloading stiffness asreversals increase , the load history and accumulative damage status were found to be the two key influencing factors.
2006, 23(6): 158-162.
Abstract:
The cracking- r esistance and flexural propert y of the r ubberized concr ete wer e investigated based on thetests of paste, morta r and concrete specimens. The cr acking- resistance was eva luated based on the cracking time ofa ring specimen, which was prepared by incor porating waste tir e rubber particles in the cement paste, and threediffer ent water-cement rat ios ( 0. 3, 0. 4, 0. 5) and five different r ubber volume fractions( 10%, 15%, 20%, 30%,50%) were used. T he r esult s show that the addition of rubber par ticles dela ys the cracking time and improves thecr acking- r esistance of the specimens and the delayed t ime increases with the incr ease of t he water2 cement r atio andthe volume fraction of rubber particles. T he flexural propert ies wer e evaluated based on the bending tests of bothmort ar and concrete, four rubber volume fr actions ( 8%, 16%, 21. 4%, 32%) were used for mor tar and threerubber fractions ( 10%, 12. 5%, 15%) for concrete. The results show t hat the r ubberized mor tar and concr et e specimen exhibited ductile fa ilure and underwent signif icant deformation befor e fr actur e. The ultimate deformat ions ofboth mortar and concrete specimen increase substant ially compar ed to the contr ol specimens.
The cracking- r esistance and flexural propert y of the r ubberized concr ete wer e investigated based on thetests of paste, morta r and concrete specimens. The cr acking- resistance was eva luated based on the cracking time ofa ring specimen, which was prepared by incor porating waste tir e rubber particles in the cement paste, and threediffer ent water-cement rat ios ( 0. 3, 0. 4, 0. 5) and five different r ubber volume fractions( 10%, 15%, 20%, 30%,50%) were used. T he r esult s show that the addition of rubber par ticles dela ys the cracking time and improves thecr acking- r esistance of the specimens and the delayed t ime increases with the incr ease of t he water2 cement r atio andthe volume fraction of rubber particles. T he flexural propert ies wer e evaluated based on the bending tests of bothmort ar and concrete, four rubber volume fr actions ( 8%, 16%, 21. 4%, 32%) were used for mor tar and threerubber fractions ( 10%, 12. 5%, 15%) for concrete. The results show t hat the r ubberized mor tar and concr et e specimen exhibited ductile fa ilure and underwent signif icant deformation befor e fr actur e. The ultimate deformat ions ofboth mortar and concrete specimen increase substant ially compar ed to the contr ol specimens.
2006, 23(6): 163-167.
Abstract:
Graphite/ aluminate cement conductive composites , which will be used as the bipolar plate of proton exchange membrane fuel cell ( PEMFC) , were prepared by mold pressing at room temperature. The effect factors ofgraphite/ aluminate cement composite bipolar plate on the elect rical conductivity and the flexural st rength were investigated and discussed. The water content , gel capillary pore size and dist ribution and H2 permeability of compositebipolar plate composites were measured. The test result s show that the conductivity and the flexural st rength of thecomposite bipolar plate can meet the PEMFC requirement s when the graphite content is 60 wt %. The compositebipolar plate contains capillary pores and the water content of the composite bipolar plate is about 7 wt % , which isdifferent f rom other composite bipolar plates. Therefore , it possesses self-humidifying function during the operatingprocess of the fuel cell. In addition , H2 permeability of the composite bipolar plate is little.
Graphite/ aluminate cement conductive composites , which will be used as the bipolar plate of proton exchange membrane fuel cell ( PEMFC) , were prepared by mold pressing at room temperature. The effect factors ofgraphite/ aluminate cement composite bipolar plate on the elect rical conductivity and the flexural st rength were investigated and discussed. The water content , gel capillary pore size and dist ribution and H2 permeability of compositebipolar plate composites were measured. The test result s show that the conductivity and the flexural st rength of thecomposite bipolar plate can meet the PEMFC requirement s when the graphite content is 60 wt %. The compositebipolar plate contains capillary pores and the water content of the composite bipolar plate is about 7 wt % , which isdifferent f rom other composite bipolar plates. Therefore , it possesses self-humidifying function during the operatingprocess of the fuel cell. In addition , H2 permeability of the composite bipolar plate is little.
2006, 23(6): 168-173.
Abstract:
Base on the model of the authorps interior cell , the fiber t race of Chenps surface cell and the section shapeof the bundle described by Chou , et al , a new combined model including surface cells and interior cells is proposed.This model can simulate the st ructure of the three- dimensional four - step braided composites accurately. On thebasis of this model , the elastic properties of three-dimensional four- step braided composites are predicted throughthe finite element calculation. By comparing the theoretical prediction with the experimental data , the influence ofthe surface cells on the whole elastic properties was discussed. The result indicates that the surface cells are impor-tant for predicting the elastic properties of three-dimensional four-step braided composites.
Base on the model of the authorps interior cell , the fiber t race of Chenps surface cell and the section shapeof the bundle described by Chou , et al , a new combined model including surface cells and interior cells is proposed.This model can simulate the st ructure of the three- dimensional four - step braided composites accurately. On thebasis of this model , the elastic properties of three-dimensional four- step braided composites are predicted throughthe finite element calculation. By comparing the theoretical prediction with the experimental data , the influence ofthe surface cells on the whole elastic properties was discussed. The result indicates that the surface cells are impor-tant for predicting the elastic properties of three-dimensional four-step braided composites.
2006, 23(6): 173-178.
Abstract:
The equivalent characteristic constitutive equations were founded in this paper. Based on the classic composites laminates theory , the stiffness mat rix and the equivalent damping mat rix of the laminates which can be described by elastic constant s and damping constant s were determined. The explicit relationship between elastic constant s and the mode was determined , as well as the explicit relationship between damping constant s and the mode.The equivalent damping mat rix of any laminates can be easily calculated out when the equivalent damping constant sin the constitutive equations are identified. The validity of this method is demonst rated through numerical examples.
The equivalent characteristic constitutive equations were founded in this paper. Based on the classic composites laminates theory , the stiffness mat rix and the equivalent damping mat rix of the laminates which can be described by elastic constant s and damping constant s were determined. The explicit relationship between elastic constant s and the mode was determined , as well as the explicit relationship between damping constant s and the mode.The equivalent damping mat rix of any laminates can be easily calculated out when the equivalent damping constant sin the constitutive equations are identified. The validity of this method is demonst rated through numerical examples.
2006, 23(6): 179-185.
Abstract:
A 3D fiber waviness model was presented. Based on the finite element method and periodic boundaryconditions , a method to analyze the compressive st rength of stitched laminates was established , which adopted abridging model and maximum st ress criteria to predict the development of damage and obtain the compressivest rength. The predicted result s are in good agreement with the test data. The effects of stitching parameters on thecompressive st rength of stitched laminates are discussed in detail. The results indicate that when stitching along thefiber on the surface of laminates , smaller stitch space and step and larger stitch radius result in higher compressivest rength. However , when stitching perpendicular to the fiber on the surface , smaller stitch space and radius andlarger stitch step result in higher compressive st rength.
A 3D fiber waviness model was presented. Based on the finite element method and periodic boundaryconditions , a method to analyze the compressive st rength of stitched laminates was established , which adopted abridging model and maximum st ress criteria to predict the development of damage and obtain the compressivest rength. The predicted result s are in good agreement with the test data. The effects of stitching parameters on thecompressive st rength of stitched laminates are discussed in detail. The results indicate that when stitching along thefiber on the surface of laminates , smaller stitch space and step and larger stitch radius result in higher compressivest rength. However , when stitching perpendicular to the fiber on the surface , smaller stitch space and radius andlarger stitch step result in higher compressive st rength.
2006, 23(6): 186-191.
Abstract:
Analytical solutions of laminated shells with magnetost rictive and viscoelastic layers are presented in thispaper. In the mechanics model , it is assumed that the viscoelastic layer only has shear deformation and the magnetost rictive materials can be studied by employing a biased linear constitution. Solving the motion equations of thelaminated thin shell with magnetost rictive layer , viscoelastic layer and composite layer , the natural f requency andthe loss factor of a st ructure are deduced. The result s show that the loss factor of a laminated st ructure is stepped upby using magnetost rictive material as the const rained layer.
Analytical solutions of laminated shells with magnetost rictive and viscoelastic layers are presented in thispaper. In the mechanics model , it is assumed that the viscoelastic layer only has shear deformation and the magnetost rictive materials can be studied by employing a biased linear constitution. Solving the motion equations of thelaminated thin shell with magnetost rictive layer , viscoelastic layer and composite layer , the natural f requency andthe loss factor of a st ructure are deduced. The result s show that the loss factor of a laminated st ructure is stepped upby using magnetost rictive material as the const rained layer.
2006, 23(6): 192-198.
Abstract:
Based on an analysis of the filament winding pattern and filament undulation , a new method for calculating the elastic modulus of filament winding composites is presented. A representative filament winding pattern wasselected and the pattern was divided into a laminate field and a filament undulation field to calculate their elastic moduli respectively. For the laminate field , the elastic modulus was calculated according to the classical laminate theoryand , for filament undulation field , the elastic modulus was calculated according to the meso-scale filament undulation situation. The whole elastic modulus of the pattern was obtained through combining the two-field elastic moduliwith the area ratios of each field to the whole pattern. The calculated elastic moduli are in good agreement with thoseof carbon/ epoxy filament winding composite tubes under tensile loading , which shows that the presented method isvaluable for calculating the elastic modulus of filament winding composites.
Based on an analysis of the filament winding pattern and filament undulation , a new method for calculating the elastic modulus of filament winding composites is presented. A representative filament winding pattern wasselected and the pattern was divided into a laminate field and a filament undulation field to calculate their elastic moduli respectively. For the laminate field , the elastic modulus was calculated according to the classical laminate theoryand , for filament undulation field , the elastic modulus was calculated according to the meso-scale filament undulation situation. The whole elastic modulus of the pattern was obtained through combining the two-field elastic moduliwith the area ratios of each field to the whole pattern. The calculated elastic moduli are in good agreement with thoseof carbon/ epoxy filament winding composite tubes under tensile loading , which shows that the presented method isvaluable for calculating the elastic modulus of filament winding composites.
