The final thickness of a product after the vacuum infusion process （VIP）, which is equal to the fiber volume fraction, depends in part on the compression responses of the preform because one of the mold faces is fle...The final thickness of a product after the vacuum infusion process （VIP）, which is equal to the fiber volume fraction, depends in part on the compression responses of the preform because one of the mold faces is flexible in VIE This study aims at investigating the compression responses of different fabrics under dry or wet conditions. The main factors affecting the compression response under investigation include, the vacuum pressure, the loading and unloading repeatability on the preform, the layup design, the kinds of fabrics, and the resin viscosity. Besides, the effects of some internal factors such as nesting and elastic recovery of fibers, lubrication of resin, friction between fibers, and so on, are also studied. In the end, this article expatiates the meaning of the matching requirements of the permeability of the preform and that of the distribution medium.展开更多
The Auxetic Structure(AS)exhibits significant densification strain due to its concave cell architecture,functioning as an effective energy-absorbing metamaterial.However,its limited plateau stress hampers further enha...The Auxetic Structure(AS)exhibits significant densification strain due to its concave cell architecture,functioning as an effective energy-absorbing metamaterial.However,its limited plateau stress hampers further enhancement of energy absorption.The deep-sea Glass Sponge(GS)has high plateau stress due to its diagonal braces.Inspired by GS,the Glass-Sponge-Auxetic Structure(GSAS)is proposed,featuring concave cells reinforced by diagonal braces to achieve both high plateau stress and densification strain.Different structural configurations incorporating various brace arrangements and thicknesses for GSAS are designed and compared through finite element analysis.An optimal GSAS is achieved with a 0.5 mm strut thickness and an asymmetric arrangement of crossing and uncrossing braces.The GSAS is fabricated using Ti6Al4V through selective laser melting and compared with AS,GS,body-centered cube,and honeycomb in compression tests.The unique bending-stretching deformation and non-simultaneous fracturing pattern results in simultaneous high plateau stress and densification strain,and the highest energy absorption and specific energy absorption.Compared to AS,these values are enhanced by 156%and 75%,respectively.The exceptional energy absorption capability of GSAS presents promising prospects in fields such as automobile collision avoidance and vibration damping,with its customizable cell numbers offering the potential for more specific applications.展开更多
The coal mining process is afected by various water sources such as groundwater and coal seam water injection.Understanding the dynamic mechanical parameters of water-immersed coal is helpful for coalmine safe product...The coal mining process is afected by various water sources such as groundwater and coal seam water injection.Understanding the dynamic mechanical parameters of water-immersed coal is helpful for coalmine safe production.The impact compression tests were performed on coal with diferent moisture contents by using theϕ50 mm Split Hopkinson Pressure Bar(SHPB)experimental system,and the dynamic characteristics and energy loss laws of water-immersed coal with diferent compositions and water contents were analyzed.Through analysis and discussion,it is found that:(1)When the moisture content of the coal sample is 0%,30%,60%,the stress,strain rate and energy frst increase and then decrease with time.(2)When the moisture content of the coal sample increases from 30%to 60%,the stress“plateau”of the coal sample becomes more obvious,resulting in an increase in the compressive stress stage and a decrease in the expansion stress stage.(3)The increase of moisture content of the coal sample will afect its impact deformation and failure mode.When the moisture content is 60%,the incident rod end and the transmission rod end of the coal sample will have obvious compression failure,and the middle part of the coal sample will also experience expansion and deformation.(4)The coal composition ratio suitable for the coal immersion softening impact experiment is optimized.展开更多
A strategy was developed for the synthesis of highly ordered 2D arrays of Ag-PNIPAM hybrid microgel. The highly ordered 2D arrays of PNIPAM microgel were prepared by dispersing PNIPAM microgel on a charge-reversible s...A strategy was developed for the synthesis of highly ordered 2D arrays of Ag-PNIPAM hybrid microgel. The highly ordered 2D arrays of PNIPAM microgel were prepared by dispersing PNIPAM microgel on a charge-reversible substrate. The microgel spheres self-assembled into a 3D colloidal crystal, and the first 111 plane was fixed in situ onto the substrate as a result of spontaneous charge reversal of the substrate, leaving a high-quality 2D array of PNIPAM microgel. Ag nanoparticles were then synthesized in situ inside the microgel spheres by introduction of Ag＋ ions into the microgel spheres and reduction with sodium borohydride. The resulting 2D arrays are highly ordered. The inter-particle distance in the array can be tuned. In addition, the method allows the synthesis of large size arrays and the use of nonplanar substrate.展开更多
Here, we present a numerical investigation of the mechanical behavior of ellipsoids under triaxial com- pression for a range of aspect ratios. Our simulations use a multi-sphere approach in a three-dimensional discret...Here, we present a numerical investigation of the mechanical behavior of ellipsoids under triaxial com- pression for a range of aspect ratios. Our simulations use a multi-sphere approach in a three-dimensional discrete element method. All assemblies were prepared at their densest condition, and triaxial compres- sion tests were performed up to extremely large strains, until a critical state was reached. The stress-strain relationship and the void ratio-strain behavior were evaluated. We found that the stress-dilatancy rela- tionship of ellipsoids with different aspect ratios could be expressed as a linear equation. In particular, the aspect ratio influenced the position of the critical state lines for these assemblies. Particle-scale char- acteristics at the critical state indicate that particles tend to be flat lying, and the obstruction of particle rotation that occurs with longer particles affects their contact mechanics. Lastly, anisotropic coefficients related to aspect ratio were investigated to probe the microscopic origins of the macroscopic behavior. A detailed analysis of geometrical and mechanical anisotropies revealed the microscopic mechanisms underlying the dependency of peak and residual strengths on aspect ratio.展开更多
文摘The final thickness of a product after the vacuum infusion process （VIP）, which is equal to the fiber volume fraction, depends in part on the compression responses of the preform because one of the mold faces is flexible in VIE This study aims at investigating the compression responses of different fabrics under dry or wet conditions. The main factors affecting the compression response under investigation include, the vacuum pressure, the loading and unloading repeatability on the preform, the layup design, the kinds of fabrics, and the resin viscosity. Besides, the effects of some internal factors such as nesting and elastic recovery of fibers, lubrication of resin, friction between fibers, and so on, are also studied. In the end, this article expatiates the meaning of the matching requirements of the permeability of the preform and that of the distribution medium.
基金supported by National Natural Science Foundation of China,China(Grant ID:52105343)National Key Research and Development Program of China,China(Grant ID:2022YFB4600203)+3 种基金Young Elite Scientists Sponsorship Program by Jilin Association for Science and Technology,China(Grant ID:QT202323)Changchun Science and Technology Bureau,China(Grant ID:23YQ13)Department of Science and Technology of Jilin Province,China(Grant ID:20230402063GH)The Fundamental Research Funds for the Central Universities,China,Jilin University,China(Grant ID:2023-JCXK-21).
文摘The Auxetic Structure(AS)exhibits significant densification strain due to its concave cell architecture,functioning as an effective energy-absorbing metamaterial.However,its limited plateau stress hampers further enhancement of energy absorption.The deep-sea Glass Sponge(GS)has high plateau stress due to its diagonal braces.Inspired by GS,the Glass-Sponge-Auxetic Structure(GSAS)is proposed,featuring concave cells reinforced by diagonal braces to achieve both high plateau stress and densification strain.Different structural configurations incorporating various brace arrangements and thicknesses for GSAS are designed and compared through finite element analysis.An optimal GSAS is achieved with a 0.5 mm strut thickness and an asymmetric arrangement of crossing and uncrossing braces.The GSAS is fabricated using Ti6Al4V through selective laser melting and compared with AS,GS,body-centered cube,and honeycomb in compression tests.The unique bending-stretching deformation and non-simultaneous fracturing pattern results in simultaneous high plateau stress and densification strain,and the highest energy absorption and specific energy absorption.Compared to AS,these values are enhanced by 156%and 75%,respectively.The exceptional energy absorption capability of GSAS presents promising prospects in fields such as automobile collision avoidance and vibration damping,with its customizable cell numbers offering the potential for more specific applications.
基金This research was funded by the National Natural Science Foundation of China(51974176,51934004)ShandongProvince Natural Science Foundation of Outstanding Youth Fund(ZR2020JQ22)+1 种基金Shandong Province Colleges and Universities Youth Innovation and Technology Support Program(2019KJH006)Taishan Scholars Project(TS20190935).
文摘The coal mining process is afected by various water sources such as groundwater and coal seam water injection.Understanding the dynamic mechanical parameters of water-immersed coal is helpful for coalmine safe production.The impact compression tests were performed on coal with diferent moisture contents by using theϕ50 mm Split Hopkinson Pressure Bar(SHPB)experimental system,and the dynamic characteristics and energy loss laws of water-immersed coal with diferent compositions and water contents were analyzed.Through analysis and discussion,it is found that:(1)When the moisture content of the coal sample is 0%,30%,60%,the stress,strain rate and energy frst increase and then decrease with time.(2)When the moisture content of the coal sample increases from 30%to 60%,the stress“plateau”of the coal sample becomes more obvious,resulting in an increase in the compressive stress stage and a decrease in the expansion stress stage.(3)The increase of moisture content of the coal sample will afect its impact deformation and failure mode.When the moisture content is 60%,the incident rod end and the transmission rod end of the coal sample will have obvious compression failure,and the middle part of the coal sample will also experience expansion and deformation.(4)The coal composition ratio suitable for the coal immersion softening impact experiment is optimized.
基金financially supported by the National Natural Science Foundation of China(Nos.21374048 and 51625302)Tianjin Committee of Science and Technology(No.16JCZDJC32900)
文摘A strategy was developed for the synthesis of highly ordered 2D arrays of Ag-PNIPAM hybrid microgel. The highly ordered 2D arrays of PNIPAM microgel were prepared by dispersing PNIPAM microgel on a charge-reversible substrate. The microgel spheres self-assembled into a 3D colloidal crystal, and the first 111 plane was fixed in situ onto the substrate as a result of spontaneous charge reversal of the substrate, leaving a high-quality 2D array of PNIPAM microgel. Ag nanoparticles were then synthesized in situ inside the microgel spheres by introduction of Ag＋ ions into the microgel spheres and reduction with sodium borohydride. The resulting 2D arrays are highly ordered. The inter-particle distance in the array can be tuned. In addition, the method allows the synthesis of large size arrays and the use of nonplanar substrate.
基金This research was supported by the National Natural Science Foundation of China （51479027, 51539008）.
文摘Here, we present a numerical investigation of the mechanical behavior of ellipsoids under triaxial com- pression for a range of aspect ratios. Our simulations use a multi-sphere approach in a three-dimensional discrete element method. All assemblies were prepared at their densest condition, and triaxial compres- sion tests were performed up to extremely large strains, until a critical state was reached. The stress-strain relationship and the void ratio-strain behavior were evaluated. We found that the stress-dilatancy rela- tionship of ellipsoids with different aspect ratios could be expressed as a linear equation. In particular, the aspect ratio influenced the position of the critical state lines for these assemblies. Particle-scale char- acteristics at the critical state indicate that particles tend to be flat lying, and the obstruction of particle rotation that occurs with longer particles affects their contact mechanics. Lastly, anisotropic coefficients related to aspect ratio were investigated to probe the microscopic origins of the macroscopic behavior. A detailed analysis of geometrical and mechanical anisotropies revealed the microscopic mechanisms underlying the dependency of peak and residual strengths on aspect ratio.
