FeAl/TiC composites were fabricated by hot pressing blended elemental powders. The effects of Ni-doping on thedensification and mechanical properties of the composites were studied. Results show that the density of th...FeAl/TiC composites were fabricated by hot pressing blended elemental powders. The effects of Ni-doping on thedensification and mechanical properties of the composites were studied. Results show that the density of the composites decreases with the content of TiC increasing, and the addition of Ni significantly improves the densificationprocess by enhancing mass transfer in the bonding phase. The mechanical properties of the composites are closelyrelated with their porosity. Besides increasing the density of the composites, the addition of Ni improves the mechanical properties by other three effects: solution-strengthening the bonding phase, strengthening the FeAI-TiC interfaceand increasing ductile fracture in FeAl phase.展开更多
Poly（1,8-octanediol-co-citrate） （POC） represents a new promising biocompatible and biodegradable polyester that has been extensively investigated for soft tissue engineering. However, the poor mechanical performan...Poly（1,8-octanediol-co-citrate） （POC） represents a new promising biocompatible and biodegradable polyester that has been extensively investigated for soft tissue engineering. However, the poor mechanical performance and poor bioactivity limit its application in bone regeneration. In this study, a series of POC/bioactive glasses （BG） composites were developed using 45S5 Bioglass^Θ and a phytic acid- derived bioactive glass （referred as PSC）. The results indicated that calcium in BG could enhance the crosslinking of the POC/BG composites by forming calcium dicarboxylate bridges and thus improve their mechanical performances. When PSC were used, the composites exhibited significantly better mechanical properties compared to composites with 45S5 Bioglass^Θ. For example, by incorporating 70wt% PSC, the compressive strength of POC/PSC composites could be improved to approximately 50 MPa and modulus 1.3-h 0.1 GPa. Furthermore, all these POC/PSC composites showed good in vitro bioactivity and cellular biocompatibility. Histology results in femoral condyle defects of Sprague-Dawley rats indicated that the POC/PSC samples integrated well with surrounding tissues and stimulated bone regeneration. The improved mechanical properties and bioactivity of POC/PSC composites make them promising for potential application in bone regeneration.展开更多
Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the ...Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the composites were increased by the addition of SiC platelet until the content up to 20 vol pct. A slight decrease in flexural Strength was measured at room temperature with increasing SiC platelet content. The high temperature flexural strength tests at 1150, 1250, and 1350℃ were conducted. It was found that the flexural strength at elevated temperature was degraded with the rising temperature, and the downward trend of flexural strength for the composite containing 10 vol. pct SiC platelet was less. The results indicate that SiC platelet had a positive influence on the high temperature strength. Effects of SiC platelet reinforcement were presented展开更多
The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were ...The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.展开更多
Diamond particles reinforced aluminum–silicon matrix composites,abbreviated as Al（Si）/diamond composites,were fabricated by squeeze casting.The effect of Si content on the microstructure and mechanical properties o...Diamond particles reinforced aluminum–silicon matrix composites,abbreviated as Al（Si）/diamond composites,were fabricated by squeeze casting.The effect of Si content on the microstructure and mechanical properties of the composites were investigated.The mechanical properties are found to increase monotonically with Si content increasing up to 7.0 wt%.The Al-7.0 wt% Si/diamond composite exhibits tensile strength of 78 MPa,bending strength of 230 MPa,and compressive strength of426 MPa.Al–Si eutectic phases are shown to connect with Al matrix and diamond particles tightly,which is responsible for the enhancement of mechanical properties in the Al（Si）/diamond composites.展开更多
An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid com- posite materials. The initial yield equations of l...An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid com- posite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.展开更多
Calcium sulfate whiskers（CSWs） modified with glutaraldehyde-crosslinked poly（vinyl alcohol）（PVA） or traditional surface modifiers,including silane coupling agent,titanate coupling agent and stearic acid,were use...Calcium sulfate whiskers（CSWs） modified with glutaraldehyde-crosslinked poly（vinyl alcohol）（PVA） or traditional surface modifiers,including silane coupling agent,titanate coupling agent and stearic acid,were used to strengthen poly（vinyl chloride）（PVC）,and the morphologies,mechanical and heat resistant properties of the resulting composites were compared.The results clearly show that glutaraldehyde cross-linked PVA modified CSW/PVC composite（c PVA@CSW/PVC） has the strongest interfacial interaction,good and stable mechanical and heat resistant properties.Nielsen＇s modified Kerner＇s equation for Young＇s modulus is better than other models examined for the CSW/PVC composites.The half debonding angle θ of c PVA@CSW/PVC composite is lower than that of other composites except silane coupling agent modified CSW/PVC composites,indicating a very strong interfacial adhesion between c PVA@CSW and PVC.In general,cross-linked PVA is effective and environmentally friendly in modifying inorganic fillers.展开更多
Centrifugal casting was applied to produce cylindrical castings using SiCp/Al composite slurry,which contained 20%SiC particles.The castings comprised a particle free zone and a particle rich zone.The amount of SiC pa...Centrifugal casting was applied to produce cylindrical castings using SiCp/Al composite slurry,which contained 20%SiC particles.The castings comprised a particle free zone and a particle rich zone.The amount of SiC particles had a dramatic transformation from the particle rich zone to the particle free zone,and the maximum content of SiC particles in the particle rich zone reached up to 40 vol%.The ultimate tensile strength（UTS） of the as-cast SiCp / Al composites in the particle rich zone was 143 MPa,and the fracture was caused by the desorption of SiC particles from matrix alloy.The coefficient of thermal expansion（CTE） of the SiC_p / Al composites in the range of 20 and 100 ℃ was determined as 16.67×10^（-6） s^（-1）,and the experimental CTE was lower than the predicted data based on the Kerner＇s model.The results show that the decrease in CTE in the case of the composites at high temperature stage can be attributed to the solute concentration of Si in Al and the plastic deformation of the matrix alloy in the composites with void architecture.展开更多
Carbon fiber reinforced high density polyethylene multi-layered laminated composite panels（HDPE/CF MLCP） with excellent in-plane properties along transverse direction have been formulated. Composite architectures wi...Carbon fiber reinforced high density polyethylene multi-layered laminated composite panels（HDPE/CF MLCP） with excellent in-plane properties along transverse direction have been formulated. Composite architectures with carbon fiber（CF） designed in 2D layout in conventional composites can alleviate their properties in thickness direction, but all attempts so far developed have achieved restrained success. Here,we have exposed an approach to the high strength composite challenge, without altering the 2D stack design on the basis of concept of fiber reinforced laminated composites that would provide enhanced mechanical and thermal properties along transverse direction. CF sheets allowed the buckling of adjoining plies in 2D MLCP. We fabricated 2D MLCP by stacking the alternative CF and HDPE layers under different loading conditions, which resulted in high strength composites. These plies of CF and HDPE served as unit cells for MLCP, with CF offering much-needed fracture toughness and hardness to these materials.For 2D HDPE/CF MLCP, we demonstrated noteworthy improvement in physical and chemical interaction between CF and HDPE, in-plane fracture strain, flexural strength（30.684 MPa）, bending modulus（7436.254 MPa）, thermal stability（40.94%）, and surface morphology, upon increasing the CF layers up to twenty, enabling these composites truly for high temperature and high strength applications.展开更多
Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such ...Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such as gas porosity and shrinkage void. Through die casting and squeezing casting, most of the defects in Mg matrix composites could be eliminated, but the mechanical properties were improved limitedly. On the other hand, after hot extrusion, not only most of the defects of as-cast composites ingots were eliminated, but also the mechanical properties were improved markedly. With the addition of SiC, the tensile strength, yield strength and elastic modulus of as extrusion SiCp/AZ61 composites increased remarkably, and the elongation decreased obviously.展开更多
In order to investigate the draping behavior of non-crimp fabrics（NCFs）, two types of carbon NCFs with tricot-chain stitches or chain stitches were formed on a hemispherical mould via a stretch forming process. The ...In order to investigate the draping behavior of non-crimp fabrics（NCFs）, two types of carbon NCFs with tricot-chain stitches or chain stitches were formed on a hemispherical mould via a stretch forming process. The shear angle and forming defects of the fabrics were measured on the hemisphere, under different blank holder forces（BHFs）. The results showed that increasing BHF could enhance the shear angle slightly, reduce the asymmetry for the deformation of the fabrics, and change the main type of the process-induced defects. Besides, compression tests were performed on the corresponding composite components. By analyzing the change of fiber volume fraction and structural parameters of the textile reinforcements, the effects of draping behavior of NCFs on the mechanical performance of the composites were studied. The results reveal that draping process has distinguishable impacts on the mechanical properties of the final components, which is closely related to the stitching pattern of the NCFs.展开更多
Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructure...Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructures of composites at different temperatures were observed by optical microscope and scanning electron microscope, respectively. The results showed that the main weight loss range of carbon/phenolic is from 300 to 800 ℃, before 700 ℃ the weight loss was resulted from pyrolysis and after that the weight loss was mainly by oxidation in the fiber phase; with the heat treatment temperature rising, the bonding at the interface of carbon fibers and resin matrix weakened; in the pyrolysis temperature range, the interlaminar shear strength（ILSS） of carbon/phenolic showed a rapid drop with temperature rising, and then decrease in the rate of ILSS became relatively slower; the fiber oxidation had little influence on the ILSS.展开更多
A novel chemical technique combined with unique plasma activated sintering（PAS） was utilized to prepare consolidated copper matrix composites（CMCs） by adding Cu-SnO2-rGO layered micro powders as reinforced fillers...A novel chemical technique combined with unique plasma activated sintering（PAS） was utilized to prepare consolidated copper matrix composites（CMCs） by adding Cu-SnO2-rGO layered micro powders as reinforced fillers into Cu matrix. The repeating Cu-SnO2-rGO structure was composed of inner dispersed reduced graphene oxide（r GO）, SnO2 as intermedia and outer Cu coating. SnO2 was introduced to the surface of rGO sheets in order to prevent the graphene aggregation with SnO2 serving as spacer and to provide enough active sites for subsequent Cu deposition. This process can guarantee rGO sheets to suffi ciently disperse and Cu nanoparticles to tightly and uniformly anchor on each layer of rGO by means of the SnO2 active sites as well as strictly control the reduction speed of Cu^2＋. The complete cover of Cu nanoparticles on rGO sheets thoroughly avoids direct contact among rGO layers. Hence, the repeating structure can simultaneously solve the wettability problem between rGO and Cu matrix as well as improve the bonding strength between rGO and Cu matrix at the well-bonded Cu-SnO2-rGO interface. The isolated rGO can effectively hinder the glide of dislocation at Cu-rGO interface and support the applied loads. Finally, the compressive strength of CMCs was enhanced when the strengthening effi ciency reached up to 41.展开更多
In the present study,the chemical and mechanical properties and the thermal expansion of a carbon nanotube（CNT）-based crystalline nano-aluminum（nano Al） composite were reported.The properties of nanocomposites wer...In the present study,the chemical and mechanical properties and the thermal expansion of a carbon nanotube（CNT）-based crystalline nano-aluminum（nano Al） composite were reported.The properties of nanocomposites were tailored by incorporating CNTs into the nano Al matrix using a physical mixing method.The elastic moduli and the coefficient of thermal expansion（CTE） of the nanocomposites were also estimated to understand the effects of CNT reinforcement in the Al matrix.Microstructural characterization of the nanocomposite reveals that the CNTs are dispersed and embedded in the Al matrix.The experimental results indicate that the incorporation of CNTs into the nano Al matrix results in the increase in hardness and elastic modulus along with a concomitant decrease in the coefficient of thermal expansion The hardness and elastic modulus of the nanocomposite increase by 21%and 20%,respectively,upon CNT addition.The CTE of CNT/A1 nanocomposite decreases to 70%compared with that of nano Al.展开更多
Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles...Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion（20-100 ℃） of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner＇s model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.展开更多
The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magn...The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magnesium in the composites using acid aluminum phosphate binder. The interfacial reaction products MgO are beneficial to interfacial bonding between SiCw and the Mg matrix. resulting in an improvement of the mechanical properties of the composite.展开更多
In this paper,stress distribution is obtained by employing the interface element to simulate the interphase feature between fiber-matrix in single-ply laminar which consists of fiber arranged periodically in the x-axi...In this paper,stress distribution is obtained by employing the interface element to simulate the interphase feature between fiber-matrix in single-ply laminar which consists of fiber arranged periodically in the x-axis direction and matrix,and which is subjected to far-field transverse load the contour of stress σsz and radial stress σr in the vicinity of interphase are plotted for three different interphase cases.It is made known that the effect of interphase properties in stress distribution is obvious.展开更多
In this work, we make the best use of the vanadium element; a series of A1-V-B alloys and VB2/A390 composite alloys were fabricated. For Ak-10V-6B alloy, the grain size of VB2 can be controlled within about 1 μm and ...In this work, we make the best use of the vanadium element; a series of A1-V-B alloys and VB2/A390 composite alloys were fabricated. For Ak-10V-6B alloy, the grain size of VB2 can be controlled within about 1 μm and is distributed uniformly in the AI matrix. Further, it can be found that VB2 promises to be a useful reinforcement particle for piston alloy. The addition of VB2 can improve the mechanical properties of the A390 composite alloys significantly. The results show that with 1 % VB2 addition, A390 composite alloy exhibits the best performance. Compared with the A390 alloy, the coefficient of thermal expansion is 13.2 × 10^-6 K-1, which decreased by 12.6%; the average Brinell hardness can reach 156.5 HB, wear weight loss decreased by 28.9% and ultimate tensile strength at 25℃ （UTS25 ℃） can reach 355 MPa, which increased by 36.5%.展开更多
An approach named direct reaction synthesis (DRS) has been developed to fabricate particulate composites with an extremely fine reinforcement size. ID situ Al matrix composites were fabri-cated by DRS. Extensive analy...An approach named direct reaction synthesis (DRS) has been developed to fabricate particulate composites with an extremely fine reinforcement size. ID situ Al matrix composites were fabri-cated by DRS. Extensive analysis of the composites microstructure using SEM and TEM identify that the reinforcement formed during the DRS process is Ti carbide (TiC) particle, generally less than 1.0 μm. The reacted, semisolid extruded samples exhibit a homogeneous distribution of fine TiC particles in Al-Cu matrix, Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure although the ductility and strength are limited by the presence of coarse titanium aluminides (Al3Ti).展开更多
Evaluation of concrete structures in nuclear power plants(NPPs)under long-term irradiation exposure is important to ensure a safe and reliable operation of NPPs during extended service life from 40 to 80 years.In this...Evaluation of concrete structures in nuclear power plants(NPPs)under long-term irradiation exposure is important to ensure a safe and reliable operation of NPPs during extended service life from 40 to 80 years.In this study,a comprehensive multiscale framework of theoretical models was developed to predict the deformation and degradation of mechanical properties of concrete materials subject to long-term neutron irradiation.The generalized self-consistent model and the Mori-Tanaka model were used to characterize the mechanical properties of concrete with multiple phases and multiple scale internal structures.The overall expansion and degradation of mechanical properties of concrete resulted from neutron irradiation as well as elevated temperature were estimated using a composite damage mechanics approach.The neutron radiation-induced degradation,volumetric expansion of aggregates,thermal strains,and shrinkage of cement paste were considered in the comprehensive model.The model can be used as a predictive tool for the effect of long-term neutron irradiation on concrete used in NPPs.展开更多
基金This work was supported by Hunan Provincial Natural Science Foundation.
文摘FeAl/TiC composites were fabricated by hot pressing blended elemental powders. The effects of Ni-doping on thedensification and mechanical properties of the composites were studied. Results show that the density of the composites decreases with the content of TiC increasing, and the addition of Ni significantly improves the densificationprocess by enhancing mass transfer in the bonding phase. The mechanical properties of the composites are closelyrelated with their porosity. Besides increasing the density of the composites, the addition of Ni improves the mechanical properties by other three effects: solution-strengthening the bonding phase, strengthening the FeAI-TiC interfaceand increasing ductile fracture in FeAl phase.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB12020300)National Natural Science Foundation of China (No. 31370985)
文摘Poly（1,8-octanediol-co-citrate） （POC） represents a new promising biocompatible and biodegradable polyester that has been extensively investigated for soft tissue engineering. However, the poor mechanical performance and poor bioactivity limit its application in bone regeneration. In this study, a series of POC/bioactive glasses （BG） composites were developed using 45S5 Bioglass^Θ and a phytic acid- derived bioactive glass （referred as PSC）. The results indicated that calcium in BG could enhance the crosslinking of the POC/BG composites by forming calcium dicarboxylate bridges and thus improve their mechanical performances. When PSC were used, the composites exhibited significantly better mechanical properties compared to composites with 45S5 Bioglass^Θ. For example, by incorporating 70wt% PSC, the compressive strength of POC/PSC composites could be improved to approximately 50 MPa and modulus 1.3-h 0.1 GPa. Furthermore, all these POC/PSC composites showed good in vitro bioactivity and cellular biocompatibility. Histology results in femoral condyle defects of Sprague-Dawley rats indicated that the POC/PSC samples integrated well with surrounding tissues and stimulated bone regeneration. The improved mechanical properties and bioactivity of POC/PSC composites make them promising for potential application in bone regeneration.
文摘Hoppressed Si3N4/SiC platelet composites had been investigated with respect to their microstructure and mechanical properties. The results indicate that Vickers hardness, elastic modulus and fracture toughness of the composites were increased by the addition of SiC platelet until the content up to 20 vol pct. A slight decrease in flexural Strength was measured at room temperature with increasing SiC platelet content. The high temperature flexural strength tests at 1150, 1250, and 1350℃ were conducted. It was found that the flexural strength at elevated temperature was degraded with the rising temperature, and the downward trend of flexural strength for the composite containing 10 vol. pct SiC platelet was less. The results indicate that SiC platelet had a positive influence on the high temperature strength. Effects of SiC platelet reinforcement were presented
基金the financial assistance received from the Department of Science and Technology(Government of India)for conducting this investigation(Project-SR/FTP/PS-054/2011(G))
文摘The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.
基金financially supported by the National Natural Science Foundation of China (No.51271017)the Fundamental Research Funds for the Central Universities (No.FRFTP-13-033A)the Program for New Century Excellent Talents in University (No.NCET-10-0227)
文摘Diamond particles reinforced aluminum–silicon matrix composites,abbreviated as Al（Si）/diamond composites,were fabricated by squeeze casting.The effect of Si content on the microstructure and mechanical properties of the composites were investigated.The mechanical properties are found to increase monotonically with Si content increasing up to 7.0 wt%.The Al-7.0 wt% Si/diamond composite exhibits tensile strength of 78 MPa,bending strength of 230 MPa,and compressive strength of426 MPa.Al–Si eutectic phases are shown to connect with Al matrix and diamond particles tightly,which is responsible for the enhancement of mechanical properties in the Al（Si）/diamond composites.
基金the China Postdoctoral Science Foundation (20060400465)the National Natural Science Foundation of China (10702033)
文摘An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid com- posite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.
基金financially supported by the National Natural Science Foundation of China(U 1507123)the Foundation from Qinghai Science and Technology Department(2014-HZ-817)Kunlun Scholar Award Program of Qinghai Province
文摘Calcium sulfate whiskers（CSWs） modified with glutaraldehyde-crosslinked poly（vinyl alcohol）（PVA） or traditional surface modifiers,including silane coupling agent,titanate coupling agent and stearic acid,were used to strengthen poly（vinyl chloride）（PVC）,and the morphologies,mechanical and heat resistant properties of the resulting composites were compared.The results clearly show that glutaraldehyde cross-linked PVA modified CSW/PVC composite（c PVA@CSW/PVC） has the strongest interfacial interaction,good and stable mechanical and heat resistant properties.Nielsen＇s modified Kerner＇s equation for Young＇s modulus is better than other models examined for the CSW/PVC composites.The half debonding angle θ of c PVA@CSW/PVC composite is lower than that of other composites except silane coupling agent modified CSW/PVC composites,indicating a very strong interfacial adhesion between c PVA@CSW and PVC.In general,cross-linked PVA is effective and environmentally friendly in modifying inorganic fillers.
基金Funded by the National Natural Science Foundation of China(No.51174244)the Foundational and Cutting-edge Research Plan of Chongqing,China(No.csts2013jcyj A50014)the Fundamental Research Funds for Central University,China(No.CDJZR12240056)
文摘Centrifugal casting was applied to produce cylindrical castings using SiCp/Al composite slurry,which contained 20%SiC particles.The castings comprised a particle free zone and a particle rich zone.The amount of SiC particles had a dramatic transformation from the particle rich zone to the particle free zone,and the maximum content of SiC particles in the particle rich zone reached up to 40 vol%.The ultimate tensile strength（UTS） of the as-cast SiCp / Al composites in the particle rich zone was 143 MPa,and the fracture was caused by the desorption of SiC particles from matrix alloy.The coefficient of thermal expansion（CTE） of the SiC_p / Al composites in the range of 20 and 100 ℃ was determined as 16.67×10^（-6） s^（-1）,and the experimental CTE was lower than the predicted data based on the Kerner＇s model.The results show that the decrease in CTE in the case of the composites at high temperature stage can be attributed to the solute concentration of Si in Al and the plastic deformation of the matrix alloy in the composites with void architecture.
文摘Carbon fiber reinforced high density polyethylene multi-layered laminated composite panels（HDPE/CF MLCP） with excellent in-plane properties along transverse direction have been formulated. Composite architectures with carbon fiber（CF） designed in 2D layout in conventional composites can alleviate their properties in thickness direction, but all attempts so far developed have achieved restrained success. Here,we have exposed an approach to the high strength composite challenge, without altering the 2D stack design on the basis of concept of fiber reinforced laminated composites that would provide enhanced mechanical and thermal properties along transverse direction. CF sheets allowed the buckling of adjoining plies in 2D MLCP. We fabricated 2D MLCP by stacking the alternative CF and HDPE layers under different loading conditions, which resulted in high strength composites. These plies of CF and HDPE served as unit cells for MLCP, with CF offering much-needed fracture toughness and hardness to these materials.For 2D HDPE/CF MLCP, we demonstrated noteworthy improvement in physical and chemical interaction between CF and HDPE, in-plane fracture strain, flexural strength（30.684 MPa）, bending modulus（7436.254 MPa）, thermal stability（40.94%）, and surface morphology, upon increasing the CF layers up to twenty, enabling these composites truly for high temperature and high strength applications.
基金Funded by the Program for New Century Excellent Talents in University(NCET-12-1040)the National Natural Science Foundation of China(Nos.50901048 and 51174143)+2 种基金the Key Project of Chinese Ministry of Education(No.2012017)the Program Foundation of Ministry of Education of China(No.20101402110008)Natural Science Foundation of Shanxi(No.2010021022-5)
文摘Mg matrix composites with SiC particles ranging from 5vol%-25vol% were prepared using stirring casting method. Die casting, squeezing casting, and extrusion were applied for inhibiting or eliminating the defects such as gas porosity and shrinkage void. Through die casting and squeezing casting, most of the defects in Mg matrix composites could be eliminated, but the mechanical properties were improved limitedly. On the other hand, after hot extrusion, not only most of the defects of as-cast composites ingots were eliminated, but also the mechanical properties were improved markedly. With the addition of SiC, the tensile strength, yield strength and elastic modulus of as extrusion SiCp/AZ61 composites increased remarkably, and the elongation decreased obviously.
基金Funded by the National Natural Science Foundation of China(No.51203144)
文摘In order to investigate the draping behavior of non-crimp fabrics（NCFs）, two types of carbon NCFs with tricot-chain stitches or chain stitches were formed on a hemispherical mould via a stretch forming process. The shear angle and forming defects of the fabrics were measured on the hemisphere, under different blank holder forces（BHFs）. The results showed that increasing BHF could enhance the shear angle slightly, reduce the asymmetry for the deformation of the fabrics, and change the main type of the process-induced defects. Besides, compression tests were performed on the corresponding composite components. By analyzing the change of fiber volume fraction and structural parameters of the textile reinforcements, the effects of draping behavior of NCFs on the mechanical performance of the composites were studied. The results reveal that draping process has distinguishable impacts on the mechanical properties of the final components, which is closely related to the stitching pattern of the NCFs.
基金the Innovation Foundation of Postgraduate of Jiangsu Province,China(No.CX08B_134Z)Beforehand Research Fund of Defense Technology(No.404040301)The Fundamental Research Funds for the Central Universities(No.NUST2011XQTR13)
文摘Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructures of composites at different temperatures were observed by optical microscope and scanning electron microscope, respectively. The results showed that the main weight loss range of carbon/phenolic is from 300 to 800 ℃, before 700 ℃ the weight loss was resulted from pyrolysis and after that the weight loss was mainly by oxidation in the fiber phase; with the heat treatment temperature rising, the bonding at the interface of carbon fibers and resin matrix weakened; in the pyrolysis temperature range, the interlaminar shear strength（ILSS） of carbon/phenolic showed a rapid drop with temperature rising, and then decrease in the rate of ILSS became relatively slower; the fiber oxidation had little influence on the ILSS.
基金Funded by the National Natural Science Foundation of China(51572208)the 111 Project(B13035)+1 种基金the National Natural Science Foundation of Hubei Province(2014CFB257 and 2014CFB258)the Fundamental Research Funds for the Central Universities(WUT:2015-III-059)
文摘A novel chemical technique combined with unique plasma activated sintering（PAS） was utilized to prepare consolidated copper matrix composites（CMCs） by adding Cu-SnO2-rGO layered micro powders as reinforced fillers into Cu matrix. The repeating Cu-SnO2-rGO structure was composed of inner dispersed reduced graphene oxide（r GO）, SnO2 as intermedia and outer Cu coating. SnO2 was introduced to the surface of rGO sheets in order to prevent the graphene aggregation with SnO2 serving as spacer and to provide enough active sites for subsequent Cu deposition. This process can guarantee rGO sheets to suffi ciently disperse and Cu nanoparticles to tightly and uniformly anchor on each layer of rGO by means of the SnO2 active sites as well as strictly control the reduction speed of Cu^2＋. The complete cover of Cu nanoparticles on rGO sheets thoroughly avoids direct contact among rGO layers. Hence, the repeating structure can simultaneously solve the wettability problem between rGO and Cu matrix as well as improve the bonding strength between rGO and Cu matrix at the well-bonded Cu-SnO2-rGO interface. The isolated rGO can effectively hinder the glide of dislocation at Cu-rGO interface and support the applied loads. Finally, the compressive strength of CMCs was enhanced when the strengthening effi ciency reached up to 41.
基金supported by the Defence Research and Development Organization, New Delhi (No.ARMREB/CDSW/2011/135)
文摘In the present study,the chemical and mechanical properties and the thermal expansion of a carbon nanotube（CNT）-based crystalline nano-aluminum（nano Al） composite were reported.The properties of nanocomposites were tailored by incorporating CNTs into the nano Al matrix using a physical mixing method.The elastic moduli and the coefficient of thermal expansion（CTE） of the nanocomposites were also estimated to understand the effects of CNT reinforcement in the Al matrix.Microstructural characterization of the nanocomposite reveals that the CNTs are dispersed and embedded in the Al matrix.The experimental results indicate that the incorporation of CNTs into the nano Al matrix results in the increase in hardness and elastic modulus along with a concomitant decrease in the coefficient of thermal expansion The hardness and elastic modulus of the nanocomposite increase by 21%and 20%,respectively,upon CNT addition.The CTE of CNT/A1 nanocomposite decreases to 70%compared with that of nano Al.
基金Funded by the National Natural Science Foundation of China(51371077)
文摘Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion（20-100 ℃） of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner＇s model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.
基金National Natllral S(tience l.'oundation of China (No. 59631080).
文摘The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magnesium in the composites using acid aluminum phosphate binder. The interfacial reaction products MgO are beneficial to interfacial bonding between SiCw and the Mg matrix. resulting in an improvement of the mechanical properties of the composite.
文摘In this paper,stress distribution is obtained by employing the interface element to simulate the interphase feature between fiber-matrix in single-ply laminar which consists of fiber arranged periodically in the x-axis direction and matrix,and which is subjected to far-field transverse load the contour of stress σsz and radial stress σr in the vicinity of interphase are plotted for three different interphase cases.It is made known that the effect of interphase properties in stress distribution is obvious.
基金supported by the National Basic Research Program of China ("973 Program", No. 2012CB825702)the National Natural Science Foundation of China (Nos. 51001065 and 51071097)+1 种基金the Taishan Scholar Blue Industry Talents Support Program of Shandong Province (2013)Young Scholars Program of Shandong University
文摘In this work, we make the best use of the vanadium element; a series of A1-V-B alloys and VB2/A390 composite alloys were fabricated. For Ak-10V-6B alloy, the grain size of VB2 can be controlled within about 1 μm and is distributed uniformly in the AI matrix. Further, it can be found that VB2 promises to be a useful reinforcement particle for piston alloy. The addition of VB2 can improve the mechanical properties of the A390 composite alloys significantly. The results show that with 1 % VB2 addition, A390 composite alloy exhibits the best performance. Compared with the A390 alloy, the coefficient of thermal expansion is 13.2 × 10^-6 K-1, which decreased by 12.6%; the average Brinell hardness can reach 156.5 HB, wear weight loss decreased by 28.9% and ultimate tensile strength at 25℃ （UTS25 ℃） can reach 355 MPa, which increased by 36.5%.
文摘An approach named direct reaction synthesis (DRS) has been developed to fabricate particulate composites with an extremely fine reinforcement size. ID situ Al matrix composites were fabri-cated by DRS. Extensive analysis of the composites microstructure using SEM and TEM identify that the reinforcement formed during the DRS process is Ti carbide (TiC) particle, generally less than 1.0 μm. The reacted, semisolid extruded samples exhibit a homogeneous distribution of fine TiC particles in Al-Cu matrix, Mechanical property evaluation of the composites has revealed a very high tensile strength relative to the matrix alloy. Fractographic analysis indicates ductile failure although the ductility and strength are limited by the presence of coarse titanium aluminides (Al3Ti).
基金sponsored by National Natural Science Foundation of China(Grant Nos.52222808 and 52478323)the University of Chicago Argonne LLC.Subcontract #6F-30823 to University of Colorado Boulder,and Beijing Nova Program(No.20230484437).
文摘Evaluation of concrete structures in nuclear power plants(NPPs)under long-term irradiation exposure is important to ensure a safe and reliable operation of NPPs during extended service life from 40 to 80 years.In this study,a comprehensive multiscale framework of theoretical models was developed to predict the deformation and degradation of mechanical properties of concrete materials subject to long-term neutron irradiation.The generalized self-consistent model and the Mori-Tanaka model were used to characterize the mechanical properties of concrete with multiple phases and multiple scale internal structures.The overall expansion and degradation of mechanical properties of concrete resulted from neutron irradiation as well as elevated temperature were estimated using a composite damage mechanics approach.The neutron radiation-induced degradation,volumetric expansion of aggregates,thermal strains,and shrinkage of cement paste were considered in the comprehensive model.The model can be used as a predictive tool for the effect of long-term neutron irradiation on concrete used in NPPs.
