Heterocyclic aramid fibers,a typical kind of high-performance fibers,have been widely used in aerospace and protection fields because of their excellent mechanical properties.However,the application of heterocyclic ar...Heterocyclic aramid fibers,a typical kind of high-performance fibers,have been widely used in aerospace and protection fields because of their excellent mechanical properties.However,the application of heterocyclic aramid fibers as a reinforcement is hindered by the weak interfacial combination with matrix materials,especially epoxy.Traditional strategies enhancing the interfacial shear strength(IFSS)usually decrease the tensile strength.Therefore,simultaneous enhancement of both mechanical properties remains a challenge.Herein,we report a novel heterocyclic aramid fiber with high interfacial shear strength(49.3 MPa)and tensile strength(6.27 GPa),in which 4,4′-diamino-2′-chlorobenzanilide(DABA-Cl)and a small amount of graphene oxide(GO)are introduced through in-situ polymerization.Hydrogen bonds andπ–πinteraction between GO and polymer chains trigger the enhancement in crystallinity,orientation,and lateral interaction of the fibers,thus improving the tensile strength and interfacial shear strength of the fibers.Moreover,the interfacial interaction between fiber and epoxy is enhanced due to the improvement of the surface polarity of the fibers caused by DABA-Cl.Therefore,a method to improve both tensile strength and interfacial shear strength of heterocyclic aramid fibers was found by introducing GO and DABA-Cl,which may provide guidance for the design and preparation of other high-performance fibers.展开更多
Accurate measurement of the interfacial shear strength between ice and solid surface has important reference significance for the design of anti-icing and de-icing functional surfaces.In this paper,a new method is pro...Accurate measurement of the interfacial shear strength between ice and solid surface has important reference significance for the design of anti-icing and de-icing functional surfaces.In this paper,a new method is proposed based on the shear lag model of a single fiber pulled out from matrix,in order to accurately determine the interfacial shear strength(ISS)between ice and metals.The maximum pull-out force at the initiation of interface debonding is well measured in the pull-out test of a metal fiber embedded in an ice matrix.A shear lag model similar to the pull-out test is established and a closed-form relation between the non-uniform interfacial shear stress and the pull-out force is achieved.When the pull-out force reaches its peak value,the ice/metal ISS can be consequently determined as the maximum interfacial shear stress.Such a method takes into account the stress concentration at the interface,which overcomes underestimation of ice/solid ISS based on the apparent strength in previous studies.The achieved ISS is proven to not only have good convergence,but also be independent of the size and embedded depth of metal fibers.Based on the present method,the enhancing effects of freezing temperature and surface roughness on the ice adhesion are further disclosed.The present research provides a simple and reliable approach to accurately calibrate the ice/solid ISS,which should be of important reference significance for the design and assessment of anti-icing functional surfaces.展开更多
Thailand has a huge variability of bast fiber plants,some of which have been little researched regarding their applicability in composites.Bast fiber(bundle)s from different species were investigated and incorporated ...Thailand has a huge variability of bast fiber plants,some of which have been little researched regarding their applicability in composites.Bast fiber(bundle)s from different species were investigated and incorporated into a polylactide(PLA)matrix by injection molding.Hemp and kenaf were used as well-studied fibers,while roselle,Fryxell and paper mulberry are less extensively characterized.Tensile strength,tensile modulus and interfacial shear strength(IFSS)of single fiber(bundle)s were highest for hemp,followed by kenaf,roselle,Fryxell and paper mulberry.Despite the lower tensile strength and IFSS of paper mulberry,the highest tensile strength was achieved for the paper mulberry/PLA composite followed by hemp/PLA.Scanning electron microscope(SEM)analyses showed that the single cells in paper mulberry fiber bundles,in contrast to the other fiber types investigated,were only partially bonded to each other,which explains the lower strength of the fiber bundles.The higher aspect ratio of fiber(bundle)s of paper mulberry in the PLA composite can explain the good composite characteristics.Apart from hemp,paper mulberry shows the best reinforcing effect in the PLA matrix and offers interesting potential for composite applications.Compared to neat PLA,the tensile strength could be increased by 24%and the tensile modulus by 54%.展开更多
To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the...To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the quantitative relationship between the maximum bridging force and Z-pin diameter,embedded length,interfacial shear strength and tensile strength is acquired.The Z-pin″bridging law″test and Z-pin tensile test are carried out to study the effect of Z-pin′s curing degree on bridging effect,and the bridging efficiency is defined to evaluate the reinforcement effect of Z-pin.The modeⅠinterlaminar fracture toughness(G_(ⅠC))is measured by the double cantilever beam test.The experimental results show that Z-pin′s co-curing with laminate matrix can improve the bridging force significantly and the fitting results show a linear relationship between Z-pin curing degree and interfacial shear strength.The three-dimensional images of the surface of pullout Z-pins indicate that the failure mode changed from totally interfacial debonding to a mixed mode.Finally,the reinforcement by partly-cured Z-pin can be used to further enhance the interlaminar toughness.Compared with completely-cured Z-pin,G_(ⅠC) of Z-pin with 67.6% curing degree increases by 47.0%.展开更多
The ratio of Fe-Al compound at interface, which could determine the quantity of Fe-Al compound at the interface of steel-mushy Al-20Sn bonding plate, was used to characterize the interfacial structure of steel-mushy A...The ratio of Fe-Al compound at interface, which could determine the quantity of Fe-Al compound at the interface of steel-mushy Al-20Sn bonding plate, was used to characterize the interfacial structure of steel-mushy Al-20Sn bonding plate quantitatively. The effect of ratio of Fe-Al compound at interface on interfacial shear strength was investigated perfectly. The results show that the relationship between ratio of Fe-Al compound at interface and interfacial shear strength is S=3.3+1.91t-0.0135t^2 (where t is ratio of Fe-Al compound at interface and S is interfacial shear strength). When the ratio of Fe-Al compound at interface is 71%, the largest interfacial shear strength 70.9 MPa is got. This reasonable ratio of Fe-Al compound at interface is a quantitative criterion of interfacial embrittlement. When the ratio of Fe-Al compound at interface is higher than 71%, interfacial embrittlement will occur.展开更多
The bonding of steel-mushy Al-7graphite was studied. The relationship between interfacial shear strength of bonding plate and solid fraction of Al-7graphite mushy was obtained, and the interfacial structure of bonding...The bonding of steel-mushy Al-7graphite was studied. The relationship between interfacial shear strength of bonding plate and solid fraction of Al-7graphite mushy was obtained, and the interfacial structure of bonding plate was determined. The results showed that: under the condition of 500℃ for preheat temperature of steel plate and 10mm/s for rolling speed, the largest interfacial shear strength of bonding plate was 70.1 MPa when solid fraction of Al-7graphite mushy was 34.6%.展开更多
CFRPs have high strength despite low density, but little impact resistance. In addition, the debonding of the interface between reinforcement fiber and matrix causes one of the fractures of FRPs. Therefore, the purpos...CFRPs have high strength despite low density, but little impact resistance. In addition, the debonding of the interface between reinforcement fiber and matrix causes one of the fractures of FRPs. Therefore, the purpose of this study is to investigate the interfacial bonding characteristics between the reinforcement fiber and matrix of FRPs, not only under static loading but also under dynamic loading. Moreover, an effective method to improve the impact resistance of FRPs from the viewpoint of interfacial bonding characteristics was proposed. First, two types of UD-FRPs in which the reinforcement fiber was glass fiber<span "=""> </span>or carbon fiber, were<span "=""> prepared to investigate the energy absorption under a bending load. A bending load was applied to the specimen statically and dynamically to measure the energy absorption until failure. The interfacial bonding characteristics between the reinforcement fiber and matrix were measured using a fragmentation method with a single fiber-embedded specimen. A dynamic tensile load was applied to the specimen using a tensile-type split Hopkinson pressure bar apparatus. Test results showed that the energy absorption of UD-CFRP decreased with an increase in strain rate, whereas that of UD-GFRP increased with an increase in strain rate. When the epoxy resin was modified by adding sub-micron glass fiber, both the interfacial shear strength between the carbon fiber and matrix, and the energy absorption of UD-CFRP improved.</span>展开更多
基金the Ministry of Science and Technology of China(No.2016YFA0200100)the Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXTD-202001)+1 种基金the National Natural Science Foundation of China(Nos.52102035,52021006,T2188101,51720105003,and 21790052)the Strategic Priority Research Program of CAS(No.XDB36030100).
文摘Heterocyclic aramid fibers,a typical kind of high-performance fibers,have been widely used in aerospace and protection fields because of their excellent mechanical properties.However,the application of heterocyclic aramid fibers as a reinforcement is hindered by the weak interfacial combination with matrix materials,especially epoxy.Traditional strategies enhancing the interfacial shear strength(IFSS)usually decrease the tensile strength.Therefore,simultaneous enhancement of both mechanical properties remains a challenge.Herein,we report a novel heterocyclic aramid fiber with high interfacial shear strength(49.3 MPa)and tensile strength(6.27 GPa),in which 4,4′-diamino-2′-chlorobenzanilide(DABA-Cl)and a small amount of graphene oxide(GO)are introduced through in-situ polymerization.Hydrogen bonds andπ–πinteraction between GO and polymer chains trigger the enhancement in crystallinity,orientation,and lateral interaction of the fibers,thus improving the tensile strength and interfacial shear strength of the fibers.Moreover,the interfacial interaction between fiber and epoxy is enhanced due to the improvement of the surface polarity of the fibers caused by DABA-Cl.Therefore,a method to improve both tensile strength and interfacial shear strength of heterocyclic aramid fibers was found by introducing GO and DABA-Cl,which may provide guidance for the design and preparation of other high-performance fibers.
基金supported by the National Natural Science Foundation of China(Grant Nos.12032004,12272043,12293000,and 12293002)。
文摘Accurate measurement of the interfacial shear strength between ice and solid surface has important reference significance for the design of anti-icing and de-icing functional surfaces.In this paper,a new method is proposed based on the shear lag model of a single fiber pulled out from matrix,in order to accurately determine the interfacial shear strength(ISS)between ice and metals.The maximum pull-out force at the initiation of interface debonding is well measured in the pull-out test of a metal fiber embedded in an ice matrix.A shear lag model similar to the pull-out test is established and a closed-form relation between the non-uniform interfacial shear stress and the pull-out force is achieved.When the pull-out force reaches its peak value,the ice/metal ISS can be consequently determined as the maximum interfacial shear stress.Such a method takes into account the stress concentration at the interface,which overcomes underestimation of ice/solid ISS based on the apparent strength in previous studies.The achieved ISS is proven to not only have good convergence,but also be independent of the size and embedded depth of metal fibers.Based on the present method,the enhancing effects of freezing temperature and surface roughness on the ice adhesion are further disclosed.The present research provides a simple and reliable approach to accurately calibrate the ice/solid ISS,which should be of important reference significance for the design and assessment of anti-icing functional surfaces.
基金The present work was funded within the framework of the BMBF Exchange Project“Thai-German Agro-Based Fiber Exchange Programme-Sustainable Development:From Plant to Product(Acronym:AgroFiber)”under Registration No.01DP15016.
文摘Thailand has a huge variability of bast fiber plants,some of which have been little researched regarding their applicability in composites.Bast fiber(bundle)s from different species were investigated and incorporated into a polylactide(PLA)matrix by injection molding.Hemp and kenaf were used as well-studied fibers,while roselle,Fryxell and paper mulberry are less extensively characterized.Tensile strength,tensile modulus and interfacial shear strength(IFSS)of single fiber(bundle)s were highest for hemp,followed by kenaf,roselle,Fryxell and paper mulberry.Despite the lower tensile strength and IFSS of paper mulberry,the highest tensile strength was achieved for the paper mulberry/PLA composite followed by hemp/PLA.Scanning electron microscope(SEM)analyses showed that the single cells in paper mulberry fiber bundles,in contrast to the other fiber types investigated,were only partially bonded to each other,which explains the lower strength of the fiber bundles.The higher aspect ratio of fiber(bundle)s of paper mulberry in the PLA composite can explain the good composite characteristics.Apart from hemp,paper mulberry shows the best reinforcing effect in the PLA matrix and offers interesting potential for composite applications.Compared to neat PLA,the tensile strength could be increased by 24%and the tensile modulus by 54%.
基金financially supported by the Aeronautical Science Fund(No.2015ZE52049)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities(No.3082615NS2015056)
文摘To study the bridging effect of partly-cured Z-pin,Z-pins with different curing degrees are manufactured by controlling pultrusion parameters.A unit cell is selected to analyze the stress of Z-pinned laminates and the quantitative relationship between the maximum bridging force and Z-pin diameter,embedded length,interfacial shear strength and tensile strength is acquired.The Z-pin″bridging law″test and Z-pin tensile test are carried out to study the effect of Z-pin′s curing degree on bridging effect,and the bridging efficiency is defined to evaluate the reinforcement effect of Z-pin.The modeⅠinterlaminar fracture toughness(G_(ⅠC))is measured by the double cantilever beam test.The experimental results show that Z-pin′s co-curing with laminate matrix can improve the bridging force significantly and the fitting results show a linear relationship between Z-pin curing degree and interfacial shear strength.The three-dimensional images of the surface of pullout Z-pins indicate that the failure mode changed from totally interfacial debonding to a mixed mode.Finally,the reinforcement by partly-cured Z-pin can be used to further enhance the interlaminar toughness.Compared with completely-cured Z-pin,G_(ⅠC) of Z-pin with 67.6% curing degree increases by 47.0%.
基金Funded by the National Natural Science Foundation of China(No.50274047 and 50304001) ,BeijingJiaotong University Founda-tion and the Foundation of the Ministry of Education of China ,andthe National Science Foundation of Beijing
文摘The ratio of Fe-Al compound at interface, which could determine the quantity of Fe-Al compound at the interface of steel-mushy Al-20Sn bonding plate, was used to characterize the interfacial structure of steel-mushy Al-20Sn bonding plate quantitatively. The effect of ratio of Fe-Al compound at interface on interfacial shear strength was investigated perfectly. The results show that the relationship between ratio of Fe-Al compound at interface and interfacial shear strength is S=3.3+1.91t-0.0135t^2 (where t is ratio of Fe-Al compound at interface and S is interfacial shear strength). When the ratio of Fe-Al compound at interface is 71%, the largest interfacial shear strength 70.9 MPa is got. This reasonable ratio of Fe-Al compound at interface is a quantitative criterion of interfacial embrittlement. When the ratio of Fe-Al compound at interface is higher than 71%, interfacial embrittlement will occur.
基金This work was financially supported by the China and Tsinghua-Zhongda Postdoctoral Science Foundation.
文摘The bonding of steel-mushy Al-7graphite was studied. The relationship between interfacial shear strength of bonding plate and solid fraction of Al-7graphite mushy was obtained, and the interfacial structure of bonding plate was determined. The results showed that: under the condition of 500℃ for preheat temperature of steel plate and 10mm/s for rolling speed, the largest interfacial shear strength of bonding plate was 70.1 MPa when solid fraction of Al-7graphite mushy was 34.6%.
文摘CFRPs have high strength despite low density, but little impact resistance. In addition, the debonding of the interface between reinforcement fiber and matrix causes one of the fractures of FRPs. Therefore, the purpose of this study is to investigate the interfacial bonding characteristics between the reinforcement fiber and matrix of FRPs, not only under static loading but also under dynamic loading. Moreover, an effective method to improve the impact resistance of FRPs from the viewpoint of interfacial bonding characteristics was proposed. First, two types of UD-FRPs in which the reinforcement fiber was glass fiber<span "=""> </span>or carbon fiber, were<span "=""> prepared to investigate the energy absorption under a bending load. A bending load was applied to the specimen statically and dynamically to measure the energy absorption until failure. The interfacial bonding characteristics between the reinforcement fiber and matrix were measured using a fragmentation method with a single fiber-embedded specimen. A dynamic tensile load was applied to the specimen using a tensile-type split Hopkinson pressure bar apparatus. Test results showed that the energy absorption of UD-CFRP decreased with an increase in strain rate, whereas that of UD-GFRP increased with an increase in strain rate. When the epoxy resin was modified by adding sub-micron glass fiber, both the interfacial shear strength between the carbon fiber and matrix, and the energy absorption of UD-CFRP improved.</span>
