The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere(DI–SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed ...The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere(DI–SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder–binder suspension onto expanded polystyrene spheres(EPSs). Afterwards, the DI–SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy(SEM), and energy-dispersive X-ray spectroscopy(EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI–SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.展开更多
In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas l...In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.展开更多
Multi-walled carbon nanotubes(MWCNTs) reinforced hollow glass microspheres(HGMs)/epoxy syntactic foam was fabricated. The effects of ultrasonication on the density, compression strength, and water absorption prope...Multi-walled carbon nanotubes(MWCNTs) reinforced hollow glass microspheres(HGMs)/epoxy syntactic foam was fabricated. The effects of ultrasonication on the density, compression strength, and water absorption properties were studied. Better dispersed MWCNTs can be obtained after ultrasonication treatment, but an increasing viscosity will lead to a larger amount of voids during syntactic foam preparation especially when the content of HGMs is more than 70 vol%. The existing voids will decrease the density of epoxy syntactic foam. However, the ultrasonication does not change the compression strength much. Ultrasonication treatment will decrease the water absorption content due to the better dispersion and hydrophobic properties of MWCNTs. But a significant increase of water absorption content occurs when HGMs is more than 70 vol%, which is attributed to the higher viscosity and larger amount of voids.展开更多
An aluminum matrix syntactic foam, incorporated with hollow-structured fly ash particles, was fabricated by pressure infiltration technique. X-ray micro-computed tomography was used to characterize its heterogeneous m...An aluminum matrix syntactic foam, incorporated with hollow-structured fly ash particles, was fabricated by pressure infiltration technique. X-ray micro-computed tomography was used to characterize its heterogeneous microstructure three dimensionally (3D). The quantification of some microstructure features, such as content and size distribution of hollow fly ash particles, was acquired in 3D. The tomographic data were exploited as a rapid method to generate a microstructurally accurate and robust 3D meshed model. The thermal transport behavior has been modeled using a commercial finite-element code to conduct steady state analyses. Simulation of the thermal conductivity showed good correlation with experimental result.展开更多
The elastic properties of syntactic foams with coated hollow spherical inclusions have been studied by means of Mori and Tanaka's concept of average stress in the matrix and Eshelby's equivalent inclusion theo...The elastic properties of syntactic foams with coated hollow spherical inclusions have been studied by means of Mori and Tanaka's concept of average stress in the matrix and Eshelby's equivalent inclusion theories.Some formulae to predict the effective modulus of this material have been derived theoretically.Based on these formulae,the influences of coating parameters such as the thickness and (Poisson's) ratio on the modulus of the syntactic foams have been discussed at the same time.展开更多
A new syntactic foam material was prepared by screening three different average particle sizes of cenospheres(150,200,and 300μm)from industrial waste fly ash.Axial impact testing on syntactic foam filler and foam-fil...A new syntactic foam material was prepared by screening three different average particle sizes of cenospheres(150,200,and 300μm)from industrial waste fly ash.Axial impact testing on syntactic foam filler and foam-filled tubes was conducted using a drop hammer test machine.The effects of parameters,such as the size of cenospheres and the impact velocity,on the mechanism of deformation,mechanical characteristics,and capacity for energy absorption of the specimen were investigated.On this basis,the differences in compressive properties exhibited by the syntactic foam-filled tubes under the two loading conditions were investigated.The results indicate that with the decrease in the average diameter of cenospheres,the initial peak crushing load and mean crushing load of foam-filled tubes increase,while the compression efficiency decreases.The specific energy absorption(SEA)of the syntactic foam-filled tube can reach 25 J/g.With the increase of impact velocity,the SEA of the specimen increases slightly.It was demonstrated that the syntactic foam-filled tube exhibits a higher effective energy absorption ratio under impact loading compared to quasi-static loading.展开更多
Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studi...Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression.In this study,the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix.Drop-weight tests are performed on composite tubes,and a digital image correlation(DIC)-based technique is used to capture their load-displacement behaviour.This eliminates the use of electronic data acquisition systems,load cells,and accelerometers.The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour.Although the mean crush load shows a drop,an increase in crush length is noticed.The specific energy absorbed by the tubes improves with an increase in GMB volume fraction.The addition of 0.1,0.2,0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by6.6%,14.7%,24%and 36.6%,respectively,compared to neat glass fibre-epoxy tubes.Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.展开更多
文摘The effects of sphere size on the microstructural and mechanical properties of ductile iron–steel hollow sphere(DI–SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder–binder suspension onto expanded polystyrene spheres(EPSs). Afterwards, the DI–SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy(SEM), and energy-dispersive X-ray spectroscopy(EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI–SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.
文摘In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.
基金Funded by the National Natural Science Foundation of China(Nos.51301029 and 51375071)the Fundamental Research Funds for the Central Universities(No.DUT17RC(3)012)
文摘Multi-walled carbon nanotubes(MWCNTs) reinforced hollow glass microspheres(HGMs)/epoxy syntactic foam was fabricated. The effects of ultrasonication on the density, compression strength, and water absorption properties were studied. Better dispersed MWCNTs can be obtained after ultrasonication treatment, but an increasing viscosity will lead to a larger amount of voids during syntactic foam preparation especially when the content of HGMs is more than 70 vol%. The existing voids will decrease the density of epoxy syntactic foam. However, the ultrasonication does not change the compression strength much. Ultrasonication treatment will decrease the water absorption content due to the better dispersion and hydrophobic properties of MWCNTs. But a significant increase of water absorption content occurs when HGMs is more than 70 vol%, which is attributed to the higher viscosity and larger amount of voids.
基金Funded by the National Natural Science Foundation of China (No. 51001037)the Fundamental Research Funds for the Central Universities (No. HIT.NSRIF.2013003)
文摘An aluminum matrix syntactic foam, incorporated with hollow-structured fly ash particles, was fabricated by pressure infiltration technique. X-ray micro-computed tomography was used to characterize its heterogeneous microstructure three dimensionally (3D). The quantification of some microstructure features, such as content and size distribution of hollow fly ash particles, was acquired in 3D. The tomographic data were exploited as a rapid method to generate a microstructurally accurate and robust 3D meshed model. The thermal transport behavior has been modeled using a commercial finite-element code to conduct steady state analyses. Simulation of the thermal conductivity showed good correlation with experimental result.
文摘The elastic properties of syntactic foams with coated hollow spherical inclusions have been studied by means of Mori and Tanaka's concept of average stress in the matrix and Eshelby's equivalent inclusion theories.Some formulae to predict the effective modulus of this material have been derived theoretically.Based on these formulae,the influences of coating parameters such as the thickness and (Poisson's) ratio on the modulus of the syntactic foams have been discussed at the same time.
基金the National Natural Science Foundation of China(Nos.51578201 and 51778196)the Heilongjiang Provincial Natural Science Foundation of China(No.LH2020E058).
文摘A new syntactic foam material was prepared by screening three different average particle sizes of cenospheres(150,200,and 300μm)from industrial waste fly ash.Axial impact testing on syntactic foam filler and foam-filled tubes was conducted using a drop hammer test machine.The effects of parameters,such as the size of cenospheres and the impact velocity,on the mechanism of deformation,mechanical characteristics,and capacity for energy absorption of the specimen were investigated.On this basis,the differences in compressive properties exhibited by the syntactic foam-filled tubes under the two loading conditions were investigated.The results indicate that with the decrease in the average diameter of cenospheres,the initial peak crushing load and mean crushing load of foam-filled tubes increase,while the compression efficiency decreases.The specific energy absorption(SEA)of the syntactic foam-filled tube can reach 25 J/g.With the increase of impact velocity,the SEA of the specimen increases slightly.It was demonstrated that the syntactic foam-filled tube exhibits a higher effective energy absorption ratio under impact loading compared to quasi-static loading.
基金supported by the Department of Science and Technology(DST,India)through the Indo-Russian collaborative project scheme。
文摘Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression.In this study,the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix.Drop-weight tests are performed on composite tubes,and a digital image correlation(DIC)-based technique is used to capture their load-displacement behaviour.This eliminates the use of electronic data acquisition systems,load cells,and accelerometers.The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour.Although the mean crush load shows a drop,an increase in crush length is noticed.The specific energy absorbed by the tubes improves with an increase in GMB volume fraction.The addition of 0.1,0.2,0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by6.6%,14.7%,24%and 36.6%,respectively,compared to neat glass fibre-epoxy tubes.Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.