In this paper,a liquid-solid origami composite design is proposed for the improvement of impact resistance.Employing this design strategy,Kresling origami composite structures with different fillings were designed and...In this paper,a liquid-solid origami composite design is proposed for the improvement of impact resistance.Employing this design strategy,Kresling origami composite structures with different fillings were designed and fabricated,namely air,water,and shear thickening fluid(STF).Quasi-static compression and drop-weight impact experiments were carried out to compare and reveal the static and dynamic mechanical behavior of these structures.The results from drop-weight impact experiments demonstrated that the solid-liquid Kresling origami composite structures exhibited superior yield strength and reduced peak force when compared to their empty counterparts.Notably,the Kresling origami structures filled with STF exhibited significantly heightened yield strength and reduced peak force.For example,at an impact velocity of 3 m/s,the yield strength of single-layer STF-filled Kresling origami structures increased by 772.7%and the peak force decreased by 68.6%.This liquid-solid origami composite design holds the potential to advance the application of origami structures in critical areas such as aerospace,intelligent protection and other important fields.The demonstrated improvements in impact resistance underscore the practical viability of this approach in enhancing structural performance for a range of applications.展开更多
The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the...The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.展开更多
The woven glass fiber reinforced composites(GFRP)subjected to high-speed impact is investigated to identify the hygrothermal aging effect on the impact resistance.Both the hygrothermal aged and unaged glass/epoxy lami...The woven glass fiber reinforced composites(GFRP)subjected to high-speed impact is investigated to identify the hygrothermal aging effect on the impact resistance.Both the hygrothermal aged and unaged glass/epoxy laminates are subjected to different impact velocities,which is confirmed as a sensitive factor for the failure modes and mechanisms.The results show the hygrothermal aging effect decreases the ballistic limit by 14.9%,but the influence on ballistic performance is limited within the impact velocity closed to the ballistic limit.The failure modes and energy dissipation mechanisms are confirmed to be slightly influenced by the hygrothermal aging effect.The hygrothermal aging effect induced localization of structural deformation and degradation of mechanical properties are the main reasons for the composite undergoing the same failure modes at smaller impact velocities.Based on the energy absorption mechanisms,analytical expressions predict the ballistic limit and energy absorption to reasonable accuracy,the underestimated total energy absorption results in a relatively poor agreement between the measured and predicted energy absorption efficiency.展开更多
The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highr...The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highresolution transmission electron microscopy(HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength(σb)and elongation(δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m^(3) at 2000 s^(-1) and 177.34 MJ/m^(3) at 5000 s^(-1) which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10;kg·m/s, the T6I6shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.展开更多
The mechanical property of a novel expanded polystyrene cement-based material （EPS-C）, which was prepared by compressing semi-dry materials molding, was investigated. The compressive behavior was analyzed by compres...The mechanical property of a novel expanded polystyrene cement-based material （EPS-C）, which was prepared by compressing semi-dry materials molding, was investigated. The compressive behavior was analyzed by compression tests to gain the energy absorbed during failure. Performance for impact resistance was tested by a self-made device. The results figures out that the EPS-C has good toughness and can reach swain of 0.7 without failure. The stress-strain curve is quite different from that of normal EPS concrete. It can be divided into three stages and in the third stage the compressing exhibits the highest energy absorption. With the rising of cement ratio, the impact force absorption （IEA） decreases first and then increases. The impact energy absorption （IEA） increases first and then decreases. The lowest IEA and the highest lEA appear at the cement dosage from 233 g/L to 267 g/L and from 233 g/L to 300 g/L, respectively.展开更多
In order to develop a rotary percussive bit with diamond enhanced cutters assisted by high pressure water jets, it is necessary to study the damage mechanism and the penetration properties of PDC cutters subject to di...In order to develop a rotary percussive bit with diamond enhanced cutters assisted by high pressure water jets, it is necessary to study the damage mechanism and the penetration properties of PDC cutters subject to different impact load level and rock types. Therefore the impact experiments of the single PDC cutters with different attack angles in four rocks: black basalt, Missouri red granite, Halston limestone, and a very soft (Roubidoux) sandstone were carried out, and the effects of rake angles of PDC cutters on both the penetration and impact resistance of PDC cutters have been discussed in detail. Test results show that a PDC insert can withstand a very strong impact in compression but is easily damaged by impact shearing, the PDC cutters are more easily damaged by shearing if the attack angles are relatively small, the 45? PDC cutters have the least penetration resistance among the cutters tested. Thus it is suggested that the attack angles of PDC cutters should be larger than 30? for bits which must withstand impact from a hammer.展开更多
A study is performed on a newly developed Polycrystalline Diamond Cutter(PDC) with improved impact resistance.Impact resistance of PDC is dependent on diamond grain size,binder content and property of the substrate.A ...A study is performed on a newly developed Polycrystalline Diamond Cutter(PDC) with improved impact resistance.Impact resistance of PDC is dependent on diamond grain size,binder content and property of the substrate.A crack might initiate in the substrate by the impact transferred from the diamond layer if substrate is not tough enough to absorb it.This failure is caused by the residual stress at the interface resulting from the difference of thermal expansion coefficient between diamond and substrate. This kind of failure could be reduced to some extent by optimizing the grain size of WC and content of Co in the substrate.PDC with much improved impact resistance is produced by also optimizing the diamond size and the content of binder phase in the layer. Drop-test with different conditions of energy and speed are carried out on the newly developed PDC and wear resistance test is done and the result is compared with that of previous PDC. It is found that the newly developed PDC shows 40%better impact resistance than previous PDC.展开更多
The packaging materials with cushioning performance are used to prevent the internal contents from being damaged by the impact and vibration of external forces.The polyurethane microcellular elastomers(PUMEs)can absor...The packaging materials with cushioning performance are used to prevent the internal contents from being damaged by the impact and vibration of external forces.The polyurethane microcellular elastomers(PUMEs)can absorb energy through cell collapse and molecular chain creep.In this study,PUMEs with different densities were investigated by scanning electron microscopy,dynamic mechanical analysis and dynamic compression tests.PUMEs exhibited significant im pact resistance and the maximum peak stress attenuation ratio reached 73.33%.The protective equipment was made by PUME with the optimal density of 600 kg/m^(3),and then the acceleration sensing device installed with the same protective equipment fell from a height of 3,5 and 10 m to evaluate the energy-absorbing property and reusability of PUMEs.The results showed that PUMEs equipment reduced the peak acceleration of the device by 93.84%,with a maximum deviation of 9%between actual test and simulation,and shortened the impact time of first landing by 57.39%.In addition,the equipment PUMEs equipment could effectively reduce the stress on the protected items.展开更多
Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,max...Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,maximum impact force withstood,and impact force efficiency was evaluated using Ansys finite element simulation software to simulate the structure's impact.To examine the impact of ribs on the structural performance of the bionic porcupine quills,a control structure was developed.According to the results of the finite element simulation,the presence of ribs in the Bionic porcupine quills structure can transfer stress uniformly to the overall structure and share stress for some of the rupture-prone regions.Ribs reduce stress concentration in specific areas and increase the impact force efficiency of the structure.The SEA and IFE values of bionic porcupine quills were 30.01 kJ/kg and 84.22%,respectively.The structure is then optimized for parameter design in order to find the optimal structure by response surface in order to improve the structure's SEA and decrease its MIF.In order to evaluate the precision of the response surface,the optimal structure predicted is validated using finite element simulation.展开更多
Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome thi...Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.展开更多
A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer com...A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-（propylene glycol） bis（2-aminopropyl） ether chains and 2-ureido-4[1H]-pyrimidinone moieties（UPy） self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.展开更多
The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer （IPC） were investigated. Different annealing temperatures ranging from 80 ℃ to 160 ℃ were selecte...The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer （IPC） were investigated. Different annealing temperatures ranging from 80 ℃ to 160 ℃ were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The crystalline structure changes in the IPC sample, including the iPP matrix and PE component, were investigated using wide angle X-ray diffraction （WAXD） and differential scanning calorimetry （DSC）. Dynamic mechanical analysis （DMA） was used to analyze the relaxation extent of 1PC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing tem. perature （140 ℃）, largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.展开更多
In the present paper, Charpy impact resistance of aluminum-epoxy laminated composites in both crack divider and crack ar-rester configurations has been investigated. In both configurations, an analytical investigation...In the present paper, Charpy impact resistance of aluminum-epoxy laminated composites in both crack divider and crack ar-rester configurations has been investigated. In both configurations, an analytical investigation has been carried out to evaluate the effects of layers thickness on impact resistance of the specimens. A model based on fuzzy logic for predicting impact re-sistance of the specimens has been presented. For purpose of building the model, training and testing using experimental re-sults from 126 specimens produced from two basic composites were conducted. The data used for the input data in fuzzy logic models are arranged in a format of 7 input parameters that cover the thickness of layers, the number of layers, the adhesive type, the crack tip configuration, the content of SiC particles, the content of methacrylated butadiene-styrene particles and the number of test trial. According to these input parameters, in the fuzzy logic model, the impact resistance of each specimen was predicted. The training and testing results in the fuzzy logic model have shown a strong potential for predicting impact resis-tance of aluminum-epoxy laminated composites.展开更多
Failure mechanism and impact resistance of a human porous cranium are studied in detail by means of theoretical and numerical methods.It is hypothesized that pore distribution of a cranium directly affects cranial ene...Failure mechanism and impact resistance of a human porous cranium are studied in detail by means of theoretical and numerical methods.It is hypothesized that pore distribution of a cranium directly affects cranial energy absorption,and a stretched beam model and a real beam model are taken as the example for the verification.Meanwhile,for the purpose of comparison with numerical results,a theoretical model is also proposed for the prediction of residual velocity and contact force of the impactor for an impacted skull.Compared with the real beam model,the stretched beam model containing through-thickness pores is easily deformed under the impact,thereby buffering well the external impact energy.The energy absorption efficiency of both the stretched beam model and real beam model is concerned with the threshold velocity for penetration which is directly related to the size of the structural damage area.Overall,there is good agreement between numerical and theoretical results.In addition,the effect of structural geometric parameters(shape and size of the impactor)on the impact resistance of the skull bone is theoretically investigated.The study provides reference for the evaluation of the energy absorption and failure mechanism of the skull under impact loads.展开更多
Solid–liquid composites(SLCs)with novel thermal/electronic/mechanical properties imparted by programmable and functional liquid inclusions have attracted considerable research interest in recent years,and are widely ...Solid–liquid composites(SLCs)with novel thermal/electronic/mechanical properties imparted by programmable and functional liquid inclusions have attracted considerable research interest in recent years,and are widely used in smart electronics and soft robotics.The feasible application of SLCs requires that they exhibit excellent static physical properties as well as dynamic impact resistance to satisfy complex service conditions,such as drops and impacts.This paper examined the impact resistance of SLCs fabricated by using microfluidic 3D printing.The results of dynamic split-Hopkinson pressure bar(SHPB)tests showed that the performance of the fabricated SLCs improved in terms of energy dissipation and impact resistance compared with pristine materials.In case of dynamic impact in the strain rates ranging from 100 to 400s−1,the SLC specimen deformed without fracture,and its energy dissipation was dominated by the viscosity of the liquid inclusions.For dynamic impact in the strain rates ranging from 500 to 800s−1,the SLC specimen fractured and its energy dissipation was determined by the volume fraction of the liquid inclusions.Thus,the energy dissipation of the SLCs could be tuned by regulating the viscosity and volume fraction of the liquid inclusions to satisfy the requirements of protection against different strain rates.Furthermore,the process of fracture of the SLCs under the dynamic SHPB tests was recorded and analyzed by using a high-speed camera.The results showed that distributed liquid inclusions changed the paths of crack propagation to enhance energy dissipation in the SLCs.This study experimentally verified the enhancement in the energy dissipation of SLCs,and provided design strategies for developing multifunctional SLCs with high impact resistance.展开更多
A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the impact resistance property of PP/KT specimens(with similar interparticles distance,1.8μm)w...A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the impact resistance property of PP/KT specimens(with similar interparticles distance,1.8μm)was studied by notched izod impact tests.It was found that the brittle-ductile transition(BDT)of the PP/KT microcomposites took place at the filler content of about 4%,and the impact strength attains the maximum at 5%(with filler particles size of 1.5μm),which is about 2.5 times that of unfilled iPP specimens.The impact fracture morphology was investigated by scanning electron micro-scopy(SEM).For the PP/KT specimens and the high-density polyethylene/KT(HDPE/KT)specimens in ductile fracture mode,many microfibers could be found on the whole impact fracture surface.It was the filler particles that induced the plastic deformation of interparticles ligament and hence improved the capability of iPP matrix on absorbing impact energy dramatically.The determinants on the BDT were further discussed on the basis of stress concentration and debonding resistance.It can be con-cluded that aside from the interparticle distance,the filler particles size also plays an important role in semicrystal-line polymer toughening.展开更多
The friction and wear properties under impact load and dry friction conditions of metal-plastic multilayer composites filled with glass fiber, treated with rare earth elements, were investigated. The worn surfaces wer...The friction and wear properties under impact load and dry friction conditions of metal-plastic multilayer composites filled with glass fiber, treated with rare earth elements, were investigated. The worn surfaces were observed and analyzed by scanning electron microscopy (SEM). It shows that applying rare earth elements surface modifier to treat the glass fiber surface can enhance the interfacial adhesion between the glass fiber and polytetrafluoroethylene (PTFE), as well as promote the interface properties of the composites. This helps to form a uniformly distributed and high adhesive transfer film on the counterface and abate the friction between the composite and the counterface. As a result, the wear of composite is greatly reduced. The composite exhibits excellent friction properties and impact wear-resistance.展开更多
In this paper the effect of rare earth elements on the toughness and impact wear resistance of nitrocarburiz- ing layers is studied.The experimental results show that the toughness and impact wear resistance of RE-nit...In this paper the effect of rare earth elements on the toughness and impact wear resistance of nitrocarburiz- ing layers is studied.The experimental results show that the toughness and impact wear resistance of RE-nitrocarburizing layers are increased significantly compared with that of conventional nitrocarburizing lay- ers.The service life of hot die for manufacturing bicycle bolts increased more than 100%.The impact wear mechanism of RE-nitrocarburizing layers is investigated by SEM as well.展开更多
The low-energy multi-impact fracture resistance of the cross rolled low chromium cast semi-steel containing RE grinding balls was studied. Moreover, its damage mode was analyzed by means of metallographic examination,...The low-energy multi-impact fracture resistance of the cross rolled low chromium cast semi-steel containing RE grinding balls was studied. Moreover, its damage mode was analyzed by means of metallographic examination, scanning electron microscopic examination and drop ball test. The results show that it can obtain extractive impact fracture resistance after proper heat treatment. More advantages were obtained for the ball worked in the condition of low-imp ductility act. The main reasons are the function of RE and the change in morphology of eutectic carbide network.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12302151 and 52105575)the BIT Research and Innovation Promoting Project(Grant No.2023YCXY049)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.QTZX23063)the Aeronautical Science Foundation of China(Grant No.2022Z073081001)the Open Research Funds of State Key Laboratory of Intelligent Manufacturing Equipment and Technology(Grant No.IMETKF2024008).
文摘In this paper,a liquid-solid origami composite design is proposed for the improvement of impact resistance.Employing this design strategy,Kresling origami composite structures with different fillings were designed and fabricated,namely air,water,and shear thickening fluid(STF).Quasi-static compression and drop-weight impact experiments were carried out to compare and reveal the static and dynamic mechanical behavior of these structures.The results from drop-weight impact experiments demonstrated that the solid-liquid Kresling origami composite structures exhibited superior yield strength and reduced peak force when compared to their empty counterparts.Notably,the Kresling origami structures filled with STF exhibited significantly heightened yield strength and reduced peak force.For example,at an impact velocity of 3 m/s,the yield strength of single-layer STF-filled Kresling origami structures increased by 772.7%and the peak force decreased by 68.6%.This liquid-solid origami composite design holds the potential to advance the application of origami structures in critical areas such as aerospace,intelligent protection and other important fields.The demonstrated improvements in impact resistance underscore the practical viability of this approach in enhancing structural performance for a range of applications.
基金Project(50578026) supported by the National Natural Science Foundation of ChinaProject supported by FCT (SFRH/BPD/22680/2005)and Research Center of Mathematics of the University of Minho through the FCT Pluriannual Funding Program
文摘The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.
基金supported by the Ph.D.Research Startup Funding of Eastern Liaoning University(Grant no.2019BS009).
文摘The woven glass fiber reinforced composites(GFRP)subjected to high-speed impact is investigated to identify the hygrothermal aging effect on the impact resistance.Both the hygrothermal aged and unaged glass/epoxy laminates are subjected to different impact velocities,which is confirmed as a sensitive factor for the failure modes and mechanisms.The results show the hygrothermal aging effect decreases the ballistic limit by 14.9%,but the influence on ballistic performance is limited within the impact velocity closed to the ballistic limit.The failure modes and energy dissipation mechanisms are confirmed to be slightly influenced by the hygrothermal aging effect.The hygrothermal aging effect induced localization of structural deformation and degradation of mechanical properties are the main reasons for the composite undergoing the same failure modes at smaller impact velocities.Based on the energy absorption mechanisms,analytical expressions predict the ballistic limit and energy absorption to reasonable accuracy,the underestimated total energy absorption results in a relatively poor agreement between the measured and predicted energy absorption efficiency.
基金Projects(52075166, 51875197) supported by the National Natural Science Foundation of ChinaProjects(2019RS2064,2019GK5043) supported by the Science and Technology Planning Project of Hunan Province,China。
文摘The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highresolution transmission electron microscopy(HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength(σb)and elongation(δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m^(3) at 2000 s^(-1) and 177.34 MJ/m^(3) at 5000 s^(-1) which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10;kg·m/s, the T6I6shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.
基金Funded by the Kwang-Hua Fund for College of Civil Engineering,Tongji Universitythe National Natural Science Fundation of China(No.41002093)the National Science and Technology Support Project of China(No.2012BAK24B04)
文摘The mechanical property of a novel expanded polystyrene cement-based material （EPS-C）, which was prepared by compressing semi-dry materials molding, was investigated. The compressive behavior was analyzed by compression tests to gain the energy absorbed during failure. Performance for impact resistance was tested by a self-made device. The results figures out that the EPS-C has good toughness and can reach swain of 0.7 without failure. The stress-strain curve is quite different from that of normal EPS concrete. It can be divided into three stages and in the third stage the compressing exhibits the highest energy absorption. With the rising of cement ratio, the impact force absorption （IEA） decreases first and then increases. The impact energy absorption （IEA） increases first and then decreases. The lowest IEA and the highest lEA appear at the cement dosage from 233 g/L to 267 g/L and from 233 g/L to 300 g/L, respectively.
文摘In order to develop a rotary percussive bit with diamond enhanced cutters assisted by high pressure water jets, it is necessary to study the damage mechanism and the penetration properties of PDC cutters subject to different impact load level and rock types. Therefore the impact experiments of the single PDC cutters with different attack angles in four rocks: black basalt, Missouri red granite, Halston limestone, and a very soft (Roubidoux) sandstone were carried out, and the effects of rake angles of PDC cutters on both the penetration and impact resistance of PDC cutters have been discussed in detail. Test results show that a PDC insert can withstand a very strong impact in compression but is easily damaged by impact shearing, the PDC cutters are more easily damaged by shearing if the attack angles are relatively small, the 45? PDC cutters have the least penetration resistance among the cutters tested. Thus it is suggested that the attack angles of PDC cutters should be larger than 30? for bits which must withstand impact from a hammer.
文摘A study is performed on a newly developed Polycrystalline Diamond Cutter(PDC) with improved impact resistance.Impact resistance of PDC is dependent on diamond grain size,binder content and property of the substrate.A crack might initiate in the substrate by the impact transferred from the diamond layer if substrate is not tough enough to absorb it.This failure is caused by the residual stress at the interface resulting from the difference of thermal expansion coefficient between diamond and substrate. This kind of failure could be reduced to some extent by optimizing the grain size of WC and content of Co in the substrate.PDC with much improved impact resistance is produced by also optimizing the diamond size and the content of binder phase in the layer. Drop-test with different conditions of energy and speed are carried out on the newly developed PDC and wear resistance test is done and the result is compared with that of previous PDC. It is found that the newly developed PDC shows 40%better impact resistance than previous PDC.
基金financially supported by the National Natural Science Foundation of China(No.22270509)。
文摘The packaging materials with cushioning performance are used to prevent the internal contents from being damaged by the impact and vibration of external forces.The polyurethane microcellular elastomers(PUMEs)can absorb energy through cell collapse and molecular chain creep.In this study,PUMEs with different densities were investigated by scanning electron microscopy,dynamic mechanical analysis and dynamic compression tests.PUMEs exhibited significant im pact resistance and the maximum peak stress attenuation ratio reached 73.33%.The protective equipment was made by PUME with the optimal density of 600 kg/m^(3),and then the acceleration sensing device installed with the same protective equipment fell from a height of 3,5 and 10 m to evaluate the energy-absorbing property and reusability of PUMEs.The results showed that PUMEs equipment reduced the peak acceleration of the device by 93.84%,with a maximum deviation of 9%between actual test and simulation,and shortened the impact time of first landing by 57.39%.In addition,the equipment PUMEs equipment could effectively reduce the stress on the protected items.
基金supported by the National Natural Science Foundation of China(No.11972158)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20221044)the Military Commission Science and Technology Committee Basic Strengthening Program Technology Fund(No.2020-JCJQ-JJ-356)and(No.2019-JCJQ-JJ-150).
文摘Using an electron microscope to observe the microstructure of a porcupine quills cross-section and a bionic method,a new bionic structure was proposed.The performance of the structure in terms of energy absorption,maximum impact force withstood,and impact force efficiency was evaluated using Ansys finite element simulation software to simulate the structure's impact.To examine the impact of ribs on the structural performance of the bionic porcupine quills,a control structure was developed.According to the results of the finite element simulation,the presence of ribs in the Bionic porcupine quills structure can transfer stress uniformly to the overall structure and share stress for some of the rupture-prone regions.Ribs reduce stress concentration in specific areas and increase the impact force efficiency of the structure.The SEA and IFE values of bionic porcupine quills were 30.01 kJ/kg and 84.22%,respectively.The structure is then optimized for parameter design in order to find the optimal structure by response surface in order to improve the structure's SEA and decrease its MIF.In order to evaluate the precision of the response surface,the optimal structure predicted is validated using finite element simulation.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11802243 and 11802241).
文摘Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.
文摘A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-（propylene glycol） bis（2-aminopropyl） ether chains and 2-ureido-4[1H]-pyrimidinone moieties（UPy） self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.
基金financially supported by the National Natural Science Foundation of China(No.51173151)the Distinguished Young Scholars Foundation of Sichuan(No.2012JQ0057)
文摘The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer （IPC） were investigated. Different annealing temperatures ranging from 80 ℃ to 160 ℃ were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The crystalline structure changes in the IPC sample, including the iPP matrix and PE component, were investigated using wide angle X-ray diffraction （WAXD） and differential scanning calorimetry （DSC）. Dynamic mechanical analysis （DMA） was used to analyze the relaxation extent of 1PC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing tem. perature （140 ℃）, largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.
文摘In the present paper, Charpy impact resistance of aluminum-epoxy laminated composites in both crack divider and crack ar-rester configurations has been investigated. In both configurations, an analytical investigation has been carried out to evaluate the effects of layers thickness on impact resistance of the specimens. A model based on fuzzy logic for predicting impact re-sistance of the specimens has been presented. For purpose of building the model, training and testing using experimental re-sults from 126 specimens produced from two basic composites were conducted. The data used for the input data in fuzzy logic models are arranged in a format of 7 input parameters that cover the thickness of layers, the number of layers, the adhesive type, the crack tip configuration, the content of SiC particles, the content of methacrylated butadiene-styrene particles and the number of test trial. According to these input parameters, in the fuzzy logic model, the impact resistance of each specimen was predicted. The training and testing results in the fuzzy logic model have shown a strong potential for predicting impact resis-tance of aluminum-epoxy laminated composites.
基金This study was funded in part by the National Natural Science Foundation of China(Grant 12002107)the National Postdoctoral Program for Innovative Talents(Grant BX20190101)+3 种基金the China Postdoctoral Science Foundation(Grant 2019M661268)the Heilongjiang Postdoctoral Financial Assistance(Grant LBH-Z19061)The present work was also supported in part by Alexander von Humboldt Foundation(Grant 1155520)(University of Siegen,Germany)the Science and Technology on Advanced Composites in Special Environment Laboratory,Young Elite Scientist Sponsorship Program by CAST(Grant YESS20160190).
文摘Failure mechanism and impact resistance of a human porous cranium are studied in detail by means of theoretical and numerical methods.It is hypothesized that pore distribution of a cranium directly affects cranial energy absorption,and a stretched beam model and a real beam model are taken as the example for the verification.Meanwhile,for the purpose of comparison with numerical results,a theoretical model is also proposed for the prediction of residual velocity and contact force of the impactor for an impacted skull.Compared with the real beam model,the stretched beam model containing through-thickness pores is easily deformed under the impact,thereby buffering well the external impact energy.The energy absorption efficiency of both the stretched beam model and real beam model is concerned with the threshold velocity for penetration which is directly related to the size of the structural damage area.Overall,there is good agreement between numerical and theoretical results.In addition,the effect of structural geometric parameters(shape and size of the impactor)on the impact resistance of the skull bone is theoretically investigated.The study provides reference for the evaluation of the energy absorption and failure mechanism of the skull under impact loads.
基金the National Natural Science Foundation of China(NSFC)under Grant nos.11988102,91848201,11521202,11872004,and 11802004China Postdoctoral Science Foundation under Grant no.2020M680222.
文摘Solid–liquid composites(SLCs)with novel thermal/electronic/mechanical properties imparted by programmable and functional liquid inclusions have attracted considerable research interest in recent years,and are widely used in smart electronics and soft robotics.The feasible application of SLCs requires that they exhibit excellent static physical properties as well as dynamic impact resistance to satisfy complex service conditions,such as drops and impacts.This paper examined the impact resistance of SLCs fabricated by using microfluidic 3D printing.The results of dynamic split-Hopkinson pressure bar(SHPB)tests showed that the performance of the fabricated SLCs improved in terms of energy dissipation and impact resistance compared with pristine materials.In case of dynamic impact in the strain rates ranging from 100 to 400s−1,the SLC specimen deformed without fracture,and its energy dissipation was dominated by the viscosity of the liquid inclusions.For dynamic impact in the strain rates ranging from 500 to 800s−1,the SLC specimen fractured and its energy dissipation was determined by the volume fraction of the liquid inclusions.Thus,the energy dissipation of the SLCs could be tuned by regulating the viscosity and volume fraction of the liquid inclusions to satisfy the requirements of protection against different strain rates.Furthermore,the process of fracture of the SLCs under the dynamic SHPB tests was recorded and analyzed by using a high-speed camera.The results showed that distributed liquid inclusions changed the paths of crack propagation to enhance energy dissipation in the SLCs.This study experimentally verified the enhancement in the energy dissipation of SLCs,and provided design strategies for developing multifunctional SLCs with high impact resistance.
基金This work was supported by Japan Science and Technology Agency(JST)the National Natural Science Foundation of China(Grant No.50803058)Program for Changjiang Scholars and Innovative Research Team in University(No.0654).
文摘A novel phenolic rigid organic filler(KT)was used to modify isotactic polypropylene(iPP).The influence of KT particles on the impact resistance property of PP/KT specimens(with similar interparticles distance,1.8μm)was studied by notched izod impact tests.It was found that the brittle-ductile transition(BDT)of the PP/KT microcomposites took place at the filler content of about 4%,and the impact strength attains the maximum at 5%(with filler particles size of 1.5μm),which is about 2.5 times that of unfilled iPP specimens.The impact fracture morphology was investigated by scanning electron micro-scopy(SEM).For the PP/KT specimens and the high-density polyethylene/KT(HDPE/KT)specimens in ductile fracture mode,many microfibers could be found on the whole impact fracture surface.It was the filler particles that induced the plastic deformation of interparticles ligament and hence improved the capability of iPP matrix on absorbing impact energy dramatically.The determinants on the BDT were further discussed on the basis of stress concentration and debonding resistance.It can be con-cluded that aside from the interparticle distance,the filler particles size also plays an important role in semicrystal-line polymer toughening.
文摘The friction and wear properties under impact load and dry friction conditions of metal-plastic multilayer composites filled with glass fiber, treated with rare earth elements, were investigated. The worn surfaces were observed and analyzed by scanning electron microscopy (SEM). It shows that applying rare earth elements surface modifier to treat the glass fiber surface can enhance the interfacial adhesion between the glass fiber and polytetrafluoroethylene (PTFE), as well as promote the interface properties of the composites. This helps to form a uniformly distributed and high adhesive transfer film on the counterface and abate the friction between the composite and the counterface. As a result, the wear of composite is greatly reduced. The composite exhibits excellent friction properties and impact wear-resistance.
基金the National Natural Science Foundation of China
文摘In this paper the effect of rare earth elements on the toughness and impact wear resistance of nitrocarburiz- ing layers is studied.The experimental results show that the toughness and impact wear resistance of RE-nitrocarburizing layers are increased significantly compared with that of conventional nitrocarburizing lay- ers.The service life of hot die for manufacturing bicycle bolts increased more than 100%.The impact wear mechanism of RE-nitrocarburizing layers is investigated by SEM as well.
文摘The low-energy multi-impact fracture resistance of the cross rolled low chromium cast semi-steel containing RE grinding balls was studied. Moreover, its damage mode was analyzed by means of metallographic examination, scanning electron microscopic examination and drop ball test. The results show that it can obtain extractive impact fracture resistance after proper heat treatment. More advantages were obtained for the ball worked in the condition of low-imp ductility act. The main reasons are the function of RE and the change in morphology of eutectic carbide network.
