2006 Vol. 23, No. 1
2006, 23(1): 1-11.
Abstract:
Researches on the selection of mat rix and reinforcement , fabrication methods , microst ructure , interfacial , oxidation behavior , and mechanical properties of in si tu reinforced titanium mat rix composites are reviewed.The processing of in situ synthesized composites by reactive hot pressing (RHP) is int roduced in detail according tothe authors’ research , and the mechanical properties and microst ructure of the composites are analyzed respectively.The review concludes with bringing forward the problems and proposing the potential development trends of the composites.
Researches on the selection of mat rix and reinforcement , fabrication methods , microst ructure , interfacial , oxidation behavior , and mechanical properties of in si tu reinforced titanium mat rix composites are reviewed.The processing of in situ synthesized composites by reactive hot pressing (RHP) is int roduced in detail according tothe authors’ research , and the mechanical properties and microst ructure of the composites are analyzed respectively.The review concludes with bringing forward the problems and proposing the potential development trends of the composites.
2006, 23(1): 12-16.
Abstract:
To cont rol the degree of fiber compaction , insure the quality of composites and reduce the cost , it is necessary to study how the state of fiber compaction changes and the factors that affect it . A parameter which is calledcompaction index Ic is used to show the degree of fiber compaction of unidirectional composite laminates. The greater the Ic , the greater the degree of fiber compaction. For the hot pressing process , the effect s of pressure , timingof the applying pressure and the number of layers on Ic were analyzed by means of optical microscope along thethickness of the laminates. The result s show that Ic increases nonlinearly with pressure , decreases with the increaseof resin viscosity at the timing of applying pressure and reduces linearly with the number of layers. These results provide some important experimental evidence to optimize the hot pressing process and establish a short2distance flow model.
To cont rol the degree of fiber compaction , insure the quality of composites and reduce the cost , it is necessary to study how the state of fiber compaction changes and the factors that affect it . A parameter which is calledcompaction index Ic is used to show the degree of fiber compaction of unidirectional composite laminates. The greater the Ic , the greater the degree of fiber compaction. For the hot pressing process , the effect s of pressure , timingof the applying pressure and the number of layers on Ic were analyzed by means of optical microscope along thethickness of the laminates. The result s show that Ic increases nonlinearly with pressure , decreases with the increaseof resin viscosity at the timing of applying pressure and reduces linearly with the number of layers. These results provide some important experimental evidence to optimize the hot pressing process and establish a short2distance flow model.
2006, 23(1): 17-25.
Abstract:
The cure kinetics of a bicomponent high performance epoxy resin was studied by dynamic DSC analysis ,and the parameters of the cure reaction were obtained to establish a phenomenological model. The relationshipbetween glass t ransition temperature ( Tg ) and cure degree (α) was analyzed with an isothermal plus dynamic DSCmethod based on DiBenedetto equation , and a mathematical description of Tg as a function of both time and temperature was suggested. Round disk compression mode DMA was employed to study the gelation at different temperatures , and the relationship between gel-time and temperature was obtained. The conversion at gelation turned out tobeαgel = 0. 4539 , while the temperature at which vit rification line and gelation line t ransected was found to be Tg ,gel =70. 18 ℃. The time-temperature-transition ( TTT) diagram was plotted based on the works above , which served as atool for process optimization in advanced composites manufacture.
The cure kinetics of a bicomponent high performance epoxy resin was studied by dynamic DSC analysis ,and the parameters of the cure reaction were obtained to establish a phenomenological model. The relationshipbetween glass t ransition temperature ( Tg ) and cure degree (α) was analyzed with an isothermal plus dynamic DSCmethod based on DiBenedetto equation , and a mathematical description of Tg as a function of both time and temperature was suggested. Round disk compression mode DMA was employed to study the gelation at different temperatures , and the relationship between gel-time and temperature was obtained. The conversion at gelation turned out tobeαgel = 0. 4539 , while the temperature at which vit rification line and gelation line t ransected was found to be Tg ,gel =70. 18 ℃. The time-temperature-transition ( TTT) diagram was plotted based on the works above , which served as atool for process optimization in advanced composites manufacture.
2006, 23(1): 26-30.
Abstract:
The EPL EXOR 500 N of Germany GABO company was used to determine the dynamic mechanical properties of carbon and glass fiber composites , which can offer a maximal load of 500 N compared to other DMAequipment . All experiment s were carried out in the three-point bending mode , at 25 ℃ and 10 Hz. The effect s ofexperiment parameters , such as preload , dynamic load , fiber type and modulus on dynamic viscoelasticities wereinvestigated. The result s show that the storage modulus increases with the preload , but decreases with the dynamicload , and the fiber type has little influence on the viscoelastic behavior , but the modulus influences it obviously.
The EPL EXOR 500 N of Germany GABO company was used to determine the dynamic mechanical properties of carbon and glass fiber composites , which can offer a maximal load of 500 N compared to other DMAequipment . All experiment s were carried out in the three-point bending mode , at 25 ℃ and 10 Hz. The effect s ofexperiment parameters , such as preload , dynamic load , fiber type and modulus on dynamic viscoelasticities wereinvestigated. The result s show that the storage modulus increases with the preload , but decreases with the dynamicload , and the fiber type has little influence on the viscoelastic behavior , but the modulus influences it obviously.
2006, 23(1): 31-36.
Abstract:
By regulating the pressure to cont rol the volume f raction of fibers Vf , the saturated permeability alongthe thickness of the fiber bed was measured by the unidirectional saturated flow method. The influence of pressureon Vf was investigated. Several factors which affect the permeability were studied , including Vf , the number of layers of the fiber bed , the ply stacking sequence and the kinds of fibers. The result s indicate that the degree of increaseof Vf with pressure decreases when Vf exceeds a critical value. The number of layers does not affect the permeabilityfor the unidirectional and bidirectional ply stacking while for the plain weave the permeability decreases with thenumber of layers. In addition , the kinds of fibers influence the permeability remarkably.
By regulating the pressure to cont rol the volume f raction of fibers Vf , the saturated permeability alongthe thickness of the fiber bed was measured by the unidirectional saturated flow method. The influence of pressureon Vf was investigated. Several factors which affect the permeability were studied , including Vf , the number of layers of the fiber bed , the ply stacking sequence and the kinds of fibers. The result s indicate that the degree of increaseof Vf with pressure decreases when Vf exceeds a critical value. The number of layers does not affect the permeabilityfor the unidirectional and bidirectional ply stacking while for the plain weave the permeability decreases with thenumber of layers. In addition , the kinds of fibers influence the permeability remarkably.
2006, 23(1): 37-43.
Abstract:
The carbon/ carbon (C/ C) composites within the mat rix-crack microst ructure were prepared by pyrolyzing carbon fiber/ phenolic resin composite which was compacted by hot pressing. The material density of C/ C composites was about 1. 27 g/ cm3 , and the open porosity was 27 % af ter pyrolysis at 900 ℃. The alterations of density ,open porosity and mass loss during pyrolysis from 200 ℃to 900 ℃were investigated. The microst ructural evolutionof phenolic resin2based C/ C composites during pyrolysis was analyzed. The phenolic resin mainly decomposed f rom400 ℃to 700 ℃, and the decomposition rate was 4 times that of other temperature ranges. A high amount of regularly spaced segmentation cracks formed above 400 ℃, and further increased and expanded with elevated temperature. A microscopic network of the characteristic interconnecting crack pattern within C/ C composites was developed af ter pyrolysis at 900 ℃. The total pore volume of C/ C composites was 0. 17cm3 / g , and 81 % of the poreswere in the radius range of 122. 190～2. 440μm.
The carbon/ carbon (C/ C) composites within the mat rix-crack microst ructure were prepared by pyrolyzing carbon fiber/ phenolic resin composite which was compacted by hot pressing. The material density of C/ C composites was about 1. 27 g/ cm3 , and the open porosity was 27 % af ter pyrolysis at 900 ℃. The alterations of density ,open porosity and mass loss during pyrolysis from 200 ℃to 900 ℃were investigated. The microst ructural evolutionof phenolic resin2based C/ C composites during pyrolysis was analyzed. The phenolic resin mainly decomposed f rom400 ℃to 700 ℃, and the decomposition rate was 4 times that of other temperature ranges. A high amount of regularly spaced segmentation cracks formed above 400 ℃, and further increased and expanded with elevated temperature. A microscopic network of the characteristic interconnecting crack pattern within C/ C composites was developed af ter pyrolysis at 900 ℃. The total pore volume of C/ C composites was 0. 17cm3 / g , and 81 % of the poreswere in the radius range of 122. 190～2. 440μm.
2006, 23(1): 44-50.
Abstract:
Polypropylene ( PP) was reinforced with nano-silica pret reated by graf ting polystyrene onto the particles.The microst ructure of the composites was studied by using atomic force microscopy ( AFM) and t ransmissionelect ron microscopy( TEM) . The observations were correlated with the tensile and impact properties of the composites. In order to illuminate the role of silica agglomerates in the composites , microscratching and nanoindentationwere investigated using AFM. The microhardness and dynamic mechanical properties (DMA) were examined as areference. It was found that the graf ted silica agglomerates possess load-bearing capacity , leading to differentresponses of the composites against the microhardness and DMA measurement s. The result s present direct evidencefor the effect of the t reated nano-silica agglomerates on the mechanical behavior of polypropylene. That is , the double percolation behavior of st ress volumet ric spheres accounted for the significant improvement on the mechanicalproperties of the composites.
Polypropylene ( PP) was reinforced with nano-silica pret reated by graf ting polystyrene onto the particles.The microst ructure of the composites was studied by using atomic force microscopy ( AFM) and t ransmissionelect ron microscopy( TEM) . The observations were correlated with the tensile and impact properties of the composites. In order to illuminate the role of silica agglomerates in the composites , microscratching and nanoindentationwere investigated using AFM. The microhardness and dynamic mechanical properties (DMA) were examined as areference. It was found that the graf ted silica agglomerates possess load-bearing capacity , leading to differentresponses of the composites against the microhardness and DMA measurement s. The result s present direct evidencefor the effect of the t reated nano-silica agglomerates on the mechanical behavior of polypropylene. That is , the double percolation behavior of st ress volumet ric spheres accounted for the significant improvement on the mechanicalproperties of the composites.
2006, 23(1): 51-55.
Abstract:
The continuous carbon fiber bundle was separated to single fiber tapes by the air comb , used as the reinforced materials in the carbon fiber/ phenolic resin composites af ter being t reated by 60 % nit ric acid. The microst ructure characteristics of the composites were investigated by scanning elect ron microscope , Raman spect roscopy ,etc. The result s of the mechanical test indicate that the composite reinforced by the continuous separated carbon fibertape has doubled it s flexural st rength and t ripled it s interlaminar shear st rength but losing some impact st rengthcompared to the composites reinforced by the continuous carbon fiber bundle.
The continuous carbon fiber bundle was separated to single fiber tapes by the air comb , used as the reinforced materials in the carbon fiber/ phenolic resin composites af ter being t reated by 60 % nit ric acid. The microst ructure characteristics of the composites were investigated by scanning elect ron microscope , Raman spect roscopy ,etc. The result s of the mechanical test indicate that the composite reinforced by the continuous separated carbon fibertape has doubled it s flexural st rength and t ripled it s interlaminar shear st rength but losing some impact st rengthcompared to the composites reinforced by the continuous carbon fiber bundle.
2006, 23(1): 56-62.
Abstract:
The curing properties and rheological behavior of resin systems were studied with DSC analysis andviscometer measurement s respectively. A dual-Arrhenius viscosity model and an engineering viscosity model wereestablished to predict the resin rheological behavior of the resin system. The two viscosity models were compared.The result s show the two models are both suitable to predict the viscosity in the mould-filling stage in resin transfermoulding. However , the engineering model provides a more accurate prediction of the viscosity near the gel point .The effectiveness of the engineering viscosity model is verified both in isothermal and non-isothermal conditions.The limitation of the engineering model is that it cannot be used to predict the viscosity af ter crosslinking of thecuring system. The engineering viscosity models can be used to predict the processing windows of different processing parameters of RTM process , which is critical for the simulation and optimization of composite manufacturingprocesses.
The curing properties and rheological behavior of resin systems were studied with DSC analysis andviscometer measurement s respectively. A dual-Arrhenius viscosity model and an engineering viscosity model wereestablished to predict the resin rheological behavior of the resin system. The two viscosity models were compared.The result s show the two models are both suitable to predict the viscosity in the mould-filling stage in resin transfermoulding. However , the engineering model provides a more accurate prediction of the viscosity near the gel point .The effectiveness of the engineering viscosity model is verified both in isothermal and non-isothermal conditions.The limitation of the engineering model is that it cannot be used to predict the viscosity af ter crosslinking of thecuring system. The engineering viscosity models can be used to predict the processing windows of different processing parameters of RTM process , which is critical for the simulation and optimization of composite manufacturingprocesses.
2006, 23(1): 63-68.
Abstract:
In order to prevent nano-particle aggregating , the nano-Al2O3 particle was covered with PS by emulsionpolymerization. The st ructure of the emulsion polymeric Al2O3 / PS composite particle was characterized by TEMand FTIR. The result s indicate that the Al2O3 / PS composite particles take an approximate ball shape and the particle consist s of centered core (Al2O3 ) and outer shell ( PS) , and the shell thickness is about 10～20nm. The st ructureof polystyrene modified by Al2O3 / PS composite particles af ter SLS was studied by SEM and FE-SEM , respectively.It is found that the nano2particles disperse in the mat rix well , and the interfacial compatibility and adhesion propertyare improved , and the density of the sintering body is increased.
In order to prevent nano-particle aggregating , the nano-Al2O3 particle was covered with PS by emulsionpolymerization. The st ructure of the emulsion polymeric Al2O3 / PS composite particle was characterized by TEMand FTIR. The result s indicate that the Al2O3 / PS composite particles take an approximate ball shape and the particle consist s of centered core (Al2O3 ) and outer shell ( PS) , and the shell thickness is about 10～20nm. The st ructureof polystyrene modified by Al2O3 / PS composite particles af ter SLS was studied by SEM and FE-SEM , respectively.It is found that the nano2particles disperse in the mat rix well , and the interfacial compatibility and adhesion propertyare improved , and the density of the sintering body is increased.
2006, 23(1): 69-74.
Abstract:
MMT/ TiO2 / PI hybrid films with various nano-filler content s were successfully prepared via in-situintercalation and sol-gel process. The molecule st ructure , fracture morphology and thermal properties were investigated by FTIR , UV-Vis , SEM and TGA , respectively. The mechanical properties at cryogenic temperature (77 K)were studied as a function of TiO2 mass f raction. The result s show that the MMT and TiO2 particles are welldispersed in the polyimide mat rix. Td of hybrid films is higher than that of the pure PI film. At 77 K, the tensilest rength of TiO2 / PI hybrid film decreases with the increase of TiO2 mass f raction while that of MMT/ TiO2 / PIhybrid film increases with the increase of TiO2 mass f raction and reaches the maximum when the TiO2 mass f ractionis 2 %. The elastic modulus increases with the increase of TiO2 mass f raction but the elongation decreases with theincrease of TiO2 mass f raction.
MMT/ TiO2 / PI hybrid films with various nano-filler content s were successfully prepared via in-situintercalation and sol-gel process. The molecule st ructure , fracture morphology and thermal properties were investigated by FTIR , UV-Vis , SEM and TGA , respectively. The mechanical properties at cryogenic temperature (77 K)were studied as a function of TiO2 mass f raction. The result s show that the MMT and TiO2 particles are welldispersed in the polyimide mat rix. Td of hybrid films is higher than that of the pure PI film. At 77 K, the tensilest rength of TiO2 / PI hybrid film decreases with the increase of TiO2 mass f raction while that of MMT/ TiO2 / PIhybrid film increases with the increase of TiO2 mass f raction and reaches the maximum when the TiO2 mass f ractionis 2 %. The elastic modulus increases with the increase of TiO2 mass f raction but the elongation decreases with theincrease of TiO2 mass f raction.
2006, 23(1): 75-79.
Abstract:
Polypyrrole/ polyaniline microtubules were prepared by using the chemical method. The influencing factorsincluding ratio of pyrrole/ aniline , adding method of aniline , concent ration of β-NSA and adding speed of APS werestudied through SEM. The result s show that the optimum preparing condition of polypyrrole/ aniline microtubules isthat pyrrole/ aniline is 1∶3 , adding speed of aniline is 1drop/ min , concent ration of β-NSA is 0. 6 mol/ L , and addingspeed of APS is 0.5 drop/ min. Pyrrole controlled the size of polypyrrole/ polyaniline microtubules in the process of reaction.
Polypyrrole/ polyaniline microtubules were prepared by using the chemical method. The influencing factorsincluding ratio of pyrrole/ aniline , adding method of aniline , concent ration of β-NSA and adding speed of APS werestudied through SEM. The result s show that the optimum preparing condition of polypyrrole/ aniline microtubules isthat pyrrole/ aniline is 1∶3 , adding speed of aniline is 1drop/ min , concent ration of β-NSA is 0. 6 mol/ L , and addingspeed of APS is 0.5 drop/ min. Pyrrole controlled the size of polypyrrole/ polyaniline microtubules in the process of reaction.
2006, 23(1): 80-84.
Abstract:
The surface of Hydroxyapatite ( HA) particles was modified by monophosphatase coupling agent . Themodified HA/ high density polyethylene ( HDPE) artificial bone composites were prepared with the fusing and mixingmethod. The composites were investigated by IR , TGA and burning test ; the rheological properties , thermal andmechanical properties were studied in detail. The result s show that the modified composites possess better rheologi2cal and mechanical properties than those of unmodified ones , good thermal properties and homogeneity. The artifi2cial bone biomaterials with good mechanical properties can be prepared through cont rolling the content of modifiedHA or HDPE in the composites.
The surface of Hydroxyapatite ( HA) particles was modified by monophosphatase coupling agent . Themodified HA/ high density polyethylene ( HDPE) artificial bone composites were prepared with the fusing and mixingmethod. The composites were investigated by IR , TGA and burning test ; the rheological properties , thermal andmechanical properties were studied in detail. The result s show that the modified composites possess better rheologi2cal and mechanical properties than those of unmodified ones , good thermal properties and homogeneity. The artifi2cial bone biomaterials with good mechanical properties can be prepared through cont rolling the content of modifiedHA or HDPE in the composites.
2006, 23(1): 85-91.
Abstract:
The tensile properties in warp and weft directions of four different st ructural kinds of carbon/ resin 3Dwoven composites are evaluated based on a series of experiment comparison and analysis. The result s indicate thatthe load-displacement curves of the four kinds of 3D woven composites in both directions show double linearity , andthe initial module is higher than the second module ; there is no yield point st rength at load-displacement curves of allkinds of 3D woven composites , which shows that the composites are brittle material ; 3D woven composites providegood mechanical behavior , and achieve higher tensile properties in both directions for one st ructural kind of composites ; the function of warp-stuffer is increasing the tensile st rength and module in the warp direction greatly , and thepurpose of increasing wef t density is increasing the tensile st rength and module in the wef t direction ; the compositeswith warp-stuffer and wef t-stuffer possesses the best mechanical properties among the four different st ructural kindsof 3D woven composites.
The tensile properties in warp and weft directions of four different st ructural kinds of carbon/ resin 3Dwoven composites are evaluated based on a series of experiment comparison and analysis. The result s indicate thatthe load-displacement curves of the four kinds of 3D woven composites in both directions show double linearity , andthe initial module is higher than the second module ; there is no yield point st rength at load-displacement curves of allkinds of 3D woven composites , which shows that the composites are brittle material ; 3D woven composites providegood mechanical behavior , and achieve higher tensile properties in both directions for one st ructural kind of composites ; the function of warp-stuffer is increasing the tensile st rength and module in the warp direction greatly , and thepurpose of increasing wef t density is increasing the tensile st rength and module in the wef t direction ; the compositeswith warp-stuffer and wef t-stuffer possesses the best mechanical properties among the four different st ructural kindsof 3D woven composites.
2006, 23(1): 92-98.
Abstract:
In order to solve the problem of weld formation , a new process using non-reinforced insert was put forward for elct ron beam welding of SiC particle reinforced aluminum mat rix composites. The influence of non-reinforced insert on weld forming characteristics , the formation of brittle compound Al4C3 and porosity was investigated.The result s show that the non-reinforced insert can improve the weld formation quality obviously and suppress theformation of Al4C3 , but the porosity problem is still serious. On the basis of a discussion of the influence of processand composition on weld defect s and mechanical properties of welded joint s , several main technical point s wereobtained.
In order to solve the problem of weld formation , a new process using non-reinforced insert was put forward for elct ron beam welding of SiC particle reinforced aluminum mat rix composites. The influence of non-reinforced insert on weld forming characteristics , the formation of brittle compound Al4C3 and porosity was investigated.The result s show that the non-reinforced insert can improve the weld formation quality obviously and suppress theformation of Al4C3 , but the porosity problem is still serious. On the basis of a discussion of the influence of processand composition on weld defect s and mechanical properties of welded joint s , several main technical point s wereobtained.
2006, 23(1): 99-104.
Abstract:
AlN-15BN (mass f raction , %) composite ceramics were fabricated with two different kinds of AlN powders with specific surface areas of 4. 26 m2 / g and a 17. 4 m2 / g , respectively , and 5 %Y2O3 as sintering additives.The effect s of the specific surface area of AlN powders on the densification of AlN-BN composite ceramics werestudied. The result s show that the specific surface area of AlN powders has great influence on the densificationprocess of composite ceramics. The densification temperature of composite ceramics is at 1500～1650 ℃with highspecific surface area AlN powder , and AlN-BN ceramics with relative density 95. 6 % was obtained af ter sintering at1650 ℃for 3 h. The density of this composite does not increase with the further increasing of sintering temperature.For AlN-BN ceramics prepared with low specific surface area AlN powders , the densification temperature is in therange of 1600～1850 ℃, and AlN-BN ceramics with relative density 86. 4 % was obtained af ter sintering at 1850 ℃for3 h. The high specific surface area of AlN powders can enhance the densification of AlN -BN composite ceramics.
AlN-15BN (mass f raction , %) composite ceramics were fabricated with two different kinds of AlN powders with specific surface areas of 4. 26 m2 / g and a 17. 4 m2 / g , respectively , and 5 %Y2O3 as sintering additives.The effect s of the specific surface area of AlN powders on the densification of AlN-BN composite ceramics werestudied. The result s show that the specific surface area of AlN powders has great influence on the densificationprocess of composite ceramics. The densification temperature of composite ceramics is at 1500～1650 ℃with highspecific surface area AlN powder , and AlN-BN ceramics with relative density 95. 6 % was obtained af ter sintering at1650 ℃for 3 h. The density of this composite does not increase with the further increasing of sintering temperature.For AlN-BN ceramics prepared with low specific surface area AlN powders , the densification temperature is in therange of 1600～1850 ℃, and AlN-BN ceramics with relative density 86. 4 % was obtained af ter sintering at 1850 ℃for3 h. The high specific surface area of AlN powders can enhance the densification of AlN -BN composite ceramics.
2006, 23(1): 105-111.
Abstract:
Carbon fibers (CF) were modified with different oligomeric silsesquioxane ( SSO) coatings to improvethe interfacial property of carbon fibers/ polyarylacetylene (CF/ PAA) . The interlaminar shear st rength ( ILSS) ofCF/ PAA was tested to make out the effect of t reatment . Atomic force microscopy (AFM) in the force modulationmode was adopted to study the cross-section surface of unidirectional CF/ PAA composites and the relative stiffnessof various phases , including CF , interphase and resin. Probability histogram and line dist ributing of CF/ PAA crosssection surface relative stiffness , obtained from the statistical analysis of the relative stiffness image , were used tocompare and study the interface characterizations of composites. The results show that the ILSS increases effectivelyand the effect s on interfacial characterizations are different af ter the CF surface was modified with different SSOcoatings owing to the different st ructures. Cage oligomeric silsesquioxane including large organic group s (Methacrylisobutyl-POSS) has the better t reatment result . AFM observations lead to the conclusion that an interfacial t ransi2tion layer with different morphology and stiffness appears in CF/ PAA composites af ter being t reated by the SSOcoatings of different st ructures. It can be inferred that the appearance of the t ransition layer may cont ribute to theimprovement on fibre/ mat rix adhesion.
Carbon fibers (CF) were modified with different oligomeric silsesquioxane ( SSO) coatings to improvethe interfacial property of carbon fibers/ polyarylacetylene (CF/ PAA) . The interlaminar shear st rength ( ILSS) ofCF/ PAA was tested to make out the effect of t reatment . Atomic force microscopy (AFM) in the force modulationmode was adopted to study the cross-section surface of unidirectional CF/ PAA composites and the relative stiffnessof various phases , including CF , interphase and resin. Probability histogram and line dist ributing of CF/ PAA crosssection surface relative stiffness , obtained from the statistical analysis of the relative stiffness image , were used tocompare and study the interface characterizations of composites. The results show that the ILSS increases effectivelyand the effect s on interfacial characterizations are different af ter the CF surface was modified with different SSOcoatings owing to the different st ructures. Cage oligomeric silsesquioxane including large organic group s (Methacrylisobutyl-POSS) has the better t reatment result . AFM observations lead to the conclusion that an interfacial t ransi2tion layer with different morphology and stiffness appears in CF/ PAA composites af ter being t reated by the SSOcoatings of different st ructures. It can be inferred that the appearance of the t ransition layer may cont ribute to theimprovement on fibre/ mat rix adhesion.
2006, 23(1): 112-116.
Abstract:
Based on experimental result s , a dilation model of CFRP tubes confining concrete columns under axialcompression is set up. By use of the calculating variation regulation of confining pressure from the dilation model ,the constitutive model of axial compression of active confinement concrete columns and the failure criterion of concrete under multi-axial st ress , the theoretical expression of st ress-st rain relationships of axial compression for thepassive confinement concrete columns is derived. According to the properties , the content s , the st ress dist ributionunder axial compression of every component and the deformation equations , the constitutive relationships of CFRPtubes confining concrete columns under axial compression are found. The experiment s demonst rate that the predicted result s of the theory are quite identical with the experimental results.
Based on experimental result s , a dilation model of CFRP tubes confining concrete columns under axialcompression is set up. By use of the calculating variation regulation of confining pressure from the dilation model ,the constitutive model of axial compression of active confinement concrete columns and the failure criterion of concrete under multi-axial st ress , the theoretical expression of st ress-st rain relationships of axial compression for thepassive confinement concrete columns is derived. According to the properties , the content s , the st ress dist ributionunder axial compression of every component and the deformation equations , the constitutive relationships of CFRPtubes confining concrete columns under axial compression are found. The experiment s demonst rate that the predicted result s of the theory are quite identical with the experimental results.
2006, 23(1): 117-123.
Abstract:
Based on the experiment , a micro-mechanical model is developed to investigate the evolution of themicrost ructure and effective properties of the cement paste in the hydration of the cement , assuming that the cementpaste composite consist s of anhydrous cement particles , cement gel and pores in the model. The cement particleshave a periodic dist ribution and are wrapped by the cement gel. The instantaneous Youngps modulus and Poissonratio of the cement paste are calculated by the direct average method and two-scale expansion method. A comparisonbetween the numerical results and experimental data shows that this model can simulate the evolution of the microst ructure and properties of the cement in the hydration. The present method can be extended to model propertyevolution of other hydrous media.
Based on the experiment , a micro-mechanical model is developed to investigate the evolution of themicrost ructure and effective properties of the cement paste in the hydration of the cement , assuming that the cementpaste composite consist s of anhydrous cement particles , cement gel and pores in the model. The cement particleshave a periodic dist ribution and are wrapped by the cement gel. The instantaneous Youngps modulus and Poissonratio of the cement paste are calculated by the direct average method and two-scale expansion method. A comparisonbetween the numerical results and experimental data shows that this model can simulate the evolution of the microst ructure and properties of the cement in the hydration. The present method can be extended to model propertyevolution of other hydrous media.
2006, 23(1): 124-128.
Abstract:
The wool fibers were carved and corroded to get rough surface by using ult raviolet radiation. So the antibacterial wool fibers were prepared by graf ting the nanometer silicon dioxide silver-loaded antibacterial agent . Thephysical , antibacterial and washable properties were characterized by using SEM , IR , etc. The surface layer of 200nm thickness was const ructed , and the nanometer antibacterial agent s are connected with the wool fibers by thechemical bonds. And the nanometer antibacterial agent is not simply attached to the surface by physical adsorption.The antibacterial efficiency of Escherichia col i and S taphy lococcus aureus is up to more than 96 % without washing ,and it is more than 90 % af ter repeated washing (at least 20 times) .
The wool fibers were carved and corroded to get rough surface by using ult raviolet radiation. So the antibacterial wool fibers were prepared by graf ting the nanometer silicon dioxide silver-loaded antibacterial agent . Thephysical , antibacterial and washable properties were characterized by using SEM , IR , etc. The surface layer of 200nm thickness was const ructed , and the nanometer antibacterial agent s are connected with the wool fibers by thechemical bonds. And the nanometer antibacterial agent is not simply attached to the surface by physical adsorption.The antibacterial efficiency of Escherichia col i and S taphy lococcus aureus is up to more than 96 % without washing ,and it is more than 90 % af ter repeated washing (at least 20 times) .
2006, 23(1): 129-134.
Abstract:
The modifying t reatment s of sisal for improving physical and chemical performance were investigated ,and the optimum modifying procedure was achieved. The modified sisals were used as reinforced fiber in f rictionmaterials. The wear properties were investigated by means of D-MS constant speed tester and the result s were com2pared with the raw sisal enhanced and mineral / steel fiber reinforced f riction materials. The result s show that thef riction factor is good for fitting with low fluctuations for different temperature values. The sisal is an ideal substi2tute for asbestos.
The modifying t reatment s of sisal for improving physical and chemical performance were investigated ,and the optimum modifying procedure was achieved. The modified sisals were used as reinforced fiber in f rictionmaterials. The wear properties were investigated by means of D-MS constant speed tester and the result s were com2pared with the raw sisal enhanced and mineral / steel fiber reinforced f riction materials. The result s show that thef riction factor is good for fitting with low fluctuations for different temperature values. The sisal is an ideal substi2tute for asbestos.
2006, 23(1): 135-141.
Abstract:
The planar and spatial yarn paths were analyzed systematically based on a 3D braiding process. A geomet ric unit cell model of the three-dimensional and seven-directional braided composite is established to describe thebasic st ructure , and the relationship between braiding parameters is deduced. This paper proposes the base for theanalysis of the mechanical properties of 3D and 7D braiding composites.
The planar and spatial yarn paths were analyzed systematically based on a 3D braiding process. A geomet ric unit cell model of the three-dimensional and seven-directional braided composite is established to describe thebasic st ructure , and the relationship between braiding parameters is deduced. This paper proposes the base for theanalysis of the mechanical properties of 3D and 7D braiding composites.
2006, 23(1): 142-146.
Abstract:
On the basis of st ructural similarity and equal stiffness , a scaling-down wing-box and a wing model forflutter test s were designed based on the original metal models. A design method based on design element s for composite st ructures was proposed and a sof tware was developed for scaling-down st ructures and composite st ructuredesign. The models were manufactured with low modulus composite materials and the modal analysis and test s weremade. The result s of analysis are in good agreement with those of the test s. The design method is very practical inengineering and the model with frame-skin st ructure , which realizes the st ructural and dynamic similarities , is muchbetter than the t raditional one , which is of beam2holding appearance st ructure.
On the basis of st ructural similarity and equal stiffness , a scaling-down wing-box and a wing model forflutter test s were designed based on the original metal models. A design method based on design element s for composite st ructures was proposed and a sof tware was developed for scaling-down st ructures and composite st ructuredesign. The models were manufactured with low modulus composite materials and the modal analysis and test s weremade. The result s of analysis are in good agreement with those of the test s. The design method is very practical inengineering and the model with frame-skin st ructure , which realizes the st ructural and dynamic similarities , is muchbetter than the t raditional one , which is of beam2holding appearance st ructure.
2006, 23(1): 147-153.
Abstract:
The continuity damage mechanics method , combined with an analysis on the contact problem of composite beams without damage , is int roduced into the analysis on the contact damage problem of composite beams understatic contact loading. The analysis on the contact problem of the non-damaged composite beam is solved by aninverse method. The approach of additional loading and iteration are applied to the analysis of the interlaminar damage and delamination problem of composite beams under static contact loading. The damage dist ribution and st ressdist ribution of glue layers are obtained. The result shows that this method has nice behavior of convergence , and isconvenient for application.
The continuity damage mechanics method , combined with an analysis on the contact problem of composite beams without damage , is int roduced into the analysis on the contact damage problem of composite beams understatic contact loading. The analysis on the contact problem of the non-damaged composite beam is solved by aninverse method. The approach of additional loading and iteration are applied to the analysis of the interlaminar damage and delamination problem of composite beams under static contact loading. The damage dist ribution and st ressdist ribution of glue layers are obtained. The result shows that this method has nice behavior of convergence , and isconvenient for application.
2006, 23(1): 154-160.
Abstract:
Nonlinear instability associated with composite laminates with a delamination under dynamic loads wasstudied. A dynamic instability equation , called Methieu equation , considering the nonlinear elastic and dampingeffect s , was deduced and the corresponding solution in terms of analytical expressions was obtained on the basis ofReddy’s simple higher order shear deformation theory and the delaminnation model developed by the authors. Thedynamic instability of the parameter vibration was investigated. From some typical examples , it is clear that theeffect s of delamination lengths and locations on the natural frequency , buckling load and instability regions , and theeffect of excitation f requency of dynamic load on the amplitude of the first parameter vibration are significant . Theinfluence of linear and nonlinear damping on the maximum deepness of“t raction”is discussed. Some typical examples indicate that the dynamic instability behavior of the laminates gradually decreases with increasing delamination ;especially , when delamination is close to the mid-plane of the laminates , the influence of delamination on the dynamic instability behavior of the laminates is most remarkably.
Nonlinear instability associated with composite laminates with a delamination under dynamic loads wasstudied. A dynamic instability equation , called Methieu equation , considering the nonlinear elastic and dampingeffect s , was deduced and the corresponding solution in terms of analytical expressions was obtained on the basis ofReddy’s simple higher order shear deformation theory and the delaminnation model developed by the authors. Thedynamic instability of the parameter vibration was investigated. From some typical examples , it is clear that theeffect s of delamination lengths and locations on the natural frequency , buckling load and instability regions , and theeffect of excitation f requency of dynamic load on the amplitude of the first parameter vibration are significant . Theinfluence of linear and nonlinear damping on the maximum deepness of“t raction”is discussed. Some typical examples indicate that the dynamic instability behavior of the laminates gradually decreases with increasing delamination ;especially , when delamination is close to the mid-plane of the laminates , the influence of delamination on the dynamic instability behavior of the laminates is most remarkably.
2006, 23(1): 161-166.
Abstract:
The dynamic characteristic of the elect rorheological ( ER) sandwich beams with a compressible core wasstudied. Assuming that the t ransverse displacement s vary with the thickness of the ER layer , a compressional-shearmodel was developed based on a first order shear deformation theory and the energy approach. Then the dynamicequations were solved by the finite element method. The result s show that the t ransverse displacement s of the topelastic layer and the bottom layer are different . The difference is small in the low-f requency range , but obvious inthe high-f requency range. Increasing the intensity of the applied electric field will decrease the difference. The thicker the ER layer , the larger the difference.
The dynamic characteristic of the elect rorheological ( ER) sandwich beams with a compressible core wasstudied. Assuming that the t ransverse displacement s vary with the thickness of the ER layer , a compressional-shearmodel was developed based on a first order shear deformation theory and the energy approach. Then the dynamicequations were solved by the finite element method. The result s show that the t ransverse displacement s of the topelastic layer and the bottom layer are different . The difference is small in the low-f requency range , but obvious inthe high-f requency range. Increasing the intensity of the applied electric field will decrease the difference. The thicker the ER layer , the larger the difference.
2006, 23(1): 167-172.
Abstract:
In order to investigate the interlayer toughening effect on damage resistance and damage tolerance , carbon fiber/ bismaleimide resin laminates HT3/ Q Y8911 were interlayer toughened with thermoplastic particles. Thequasi-static indentation (QSI) test and compression test af ter impact were conducted to determine the damage resistance and damage tolerance of non-interleaved and interleaved specimens. Visual observation and ult ra-sonic C scanwere also employed to inspect the damage size. The delamination onset load for 2 mm thickness interleaved specimens is remarkably increased , while the delamination onset load2drop magnitude for 4 mm thickness interleaved onesis significantly decreased. These two parameters can be used to characterize damage resistance under quasi-staticforce. Under the same load or same impact energy per unit thickness , interleaved specimens have a smaller damagearea at the expense of relative deeper indentation in the local region. In the case of similar damage size , the compression st rength af ter impact and the ultimate failure st rain of interleaved HT3/ Q Y8911 are obviously improved , andtherefore higher damage tolerance is achieved.
In order to investigate the interlayer toughening effect on damage resistance and damage tolerance , carbon fiber/ bismaleimide resin laminates HT3/ Q Y8911 were interlayer toughened with thermoplastic particles. Thequasi-static indentation (QSI) test and compression test af ter impact were conducted to determine the damage resistance and damage tolerance of non-interleaved and interleaved specimens. Visual observation and ult ra-sonic C scanwere also employed to inspect the damage size. The delamination onset load for 2 mm thickness interleaved specimens is remarkably increased , while the delamination onset load2drop magnitude for 4 mm thickness interleaved onesis significantly decreased. These two parameters can be used to characterize damage resistance under quasi-staticforce. Under the same load or same impact energy per unit thickness , interleaved specimens have a smaller damagearea at the expense of relative deeper indentation in the local region. In the case of similar damage size , the compression st rength af ter impact and the ultimate failure st rain of interleaved HT3/ Q Y8911 are obviously improved , andtherefore higher damage tolerance is achieved.
2006, 23(1): 173-179.
Abstract:
An efficient and accurate random vibration algorithm for the composite laminated st ructures attachedwith the viscoelastic damping layer is proposed. Both the Adams damping of the composite laminated st ructures andthe attached f requency-dependant damping were taken into account in the analysis. For the resulting non-classicallydamped and f requency-dependant complex system , in combination with the real-mode-based degree-reductionscheme , a pseudo excitation method is developed to solve the reduced random vibration equation. The combined algorithm has been implemented on the DDJ sof tware system. A composite horizontal tail of the Boeing737 aircraf tst ructure was computed and studied. Such complex computations and the reasonable result s show that the proposedmethod is quite useful for the analysis and design of composite st ructures.
An efficient and accurate random vibration algorithm for the composite laminated st ructures attachedwith the viscoelastic damping layer is proposed. Both the Adams damping of the composite laminated st ructures andthe attached f requency-dependant damping were taken into account in the analysis. For the resulting non-classicallydamped and f requency-dependant complex system , in combination with the real-mode-based degree-reductionscheme , a pseudo excitation method is developed to solve the reduced random vibration equation. The combined algorithm has been implemented on the DDJ sof tware system. A composite horizontal tail of the Boeing737 aircraf tst ructure was computed and studied. Such complex computations and the reasonable result s show that the proposedmethod is quite useful for the analysis and design of composite st ructures.
2006, 23(1): 180-184.
Abstract:
Experimental study on parameter optimization of the maximal influencing factor layer of alternately laminated anisot ropic damped st ructures was carried out with dynamic mechanical analyzer (DMA Q800) . The influencesof different orientation angles , thicknesses and multilayer substitutes of the main cont rolled const rained layer ontemperature and f requency characteristics of the st ructural stiffness and damping were discussed. The experimentalresult s show that the st ructural damping characteristics are better while the orientation angle of the layer is close to90°(including the laminating of two 90°layers) ,and the optimal thickness is different in different st ructures , andthe st ructural damping characteristic is better while the ratio of the total thickness of the damping layers to the maincont rolled anisot ropic layer is about 10.
Experimental study on parameter optimization of the maximal influencing factor layer of alternately laminated anisot ropic damped st ructures was carried out with dynamic mechanical analyzer (DMA Q800) . The influencesof different orientation angles , thicknesses and multilayer substitutes of the main cont rolled const rained layer ontemperature and f requency characteristics of the st ructural stiffness and damping were discussed. The experimentalresult s show that the st ructural damping characteristics are better while the orientation angle of the layer is close to90°(including the laminating of two 90°layers) ,and the optimal thickness is different in different st ructures , andthe st ructural damping characteristic is better while the ratio of the total thickness of the damping layers to the maincont rolled anisot ropic layer is about 10.
