The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observed by SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values at critical crazing ...The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observed by SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values at critical crazing and yielding and the craze stability of PPQ-E samples depend on the thermal-dealing condition for the samples. From the point of view of cohesional entanglements and energy absorbed by samples, the experiment results were explained.展开更多
This work highlights the benefits of environmental crazing for the control over the hydrophilic-lipophilic balance of glassy amorphous and semicrystalline polymers:poly(ethylene terephthalate)(PET)and biodegradable po...This work highlights the benefits of environmental crazing for the control over the hydrophilic-lipophilic balance of glassy amorphous and semicrystalline polymers:poly(ethylene terephthalate)(PET)and biodegradable polycaprolactone(PCL).Task-oriented encapsulation of diverse commercial and natural hydrophilic(polyethyleneoxide,polyvinylpyrrolidone,gelatin)and hydrophobic vip additives(perfluoroorgano siloxanes,water-repellent impregnation)into mesoporous host polymer(PET,PCL)matrixes allows targeted control over the wettability of the resultant nanocomposite materials.Depending on the nature of the vip additive,the properties of the modified polymers can be varied from hydrophilic to hydrophobic:contact angle(CA)of PET can be adjusted from 47_(⊥)/38_(||)to 130_(⊥)/117_(||)°(for initial PET,CA=82°)and CA of PCL from 40°to 114°(for initial PCL CA=75°).The unique benefits of environmental crazing for structural modification are related to the universal character of this approach which can be applied to a broad range of polymers and allows preparation of diverse high-performance materials with tunable hydrophilic-lipophilic balance.展开更多
A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, incr...A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, increased with the content of POE. SEM micrographs showed the poor compatibility between PS and POE. In simple tensile tests, it is very easy to achieve the ratio of crazing deformation, i.e. K by measuring the size changes of samples. The K values decreased with increasing the content of POE, and the deformations of PS/POE blends were dominated by crazing. The plots of the change of volume （△V） against longitudinal variation （△I） showed a linear relationship, and the slope of lines decreased with the content of POE. Measuring samples at the tensile velocities of 5 mm/min, 50 mm/min, and 500 mm/min respectively, the K values kept unchanged for each PS/POE blends.展开更多
The nanoparticle(NP) functionalization is an effective method for enhancing their compatibility with polymer which can influence the fracture property of the polymer nanocomposites(PNCs). This work aims to further und...The nanoparticle(NP) functionalization is an effective method for enhancing their compatibility with polymer which can influence the fracture property of the polymer nanocomposites(PNCs). This work aims to further understand the cavitation and crazing process, hoping to uncover the fracture mechanism on the molecular level. By adopting a coarse-grained molecular dynamics simulation, the fracture energy of PNCs first increases and then decreases with increasing the NP functionalization degree α while it shows a continuous increase with increasing the interaction εpA between polymer and modified beads. The bond orientation degree is first characterized which is referred to as the elongation. Meanwhile, the stress by polymer chains is gradually reduced with increasing the α or the εpA while that by NPs is enhanced.Furthermore, the percentage of stress by polymer chains first increases and then decreases with increasing the strain while that by NPs shows a contrast trend. Moreover, the number of voids is quantified which first increases and then decreases with increasing the strain which reflects their nucleation and coalescence process. The voids prefer to generate from the polymer-NP interface to the polymer matrix with increasing α o r εpA.As a result, the number of voids first increases and then decreases with increasing α while it continuously declines with the εpA. In summary, our work provides a clear understanding on how the NP functionalization influences the cavitation and crazing process during the fracture process.展开更多
Glassy polymers can be substantially toughened by incorporation of rubber particles at a certain volume percentage. The toughness is related to crazing initiated by rubber particles. The blend of styrene-acrylonitrile...Glassy polymers can be substantially toughened by incorporation of rubber particles at a certain volume percentage. The toughness is related to crazing initiated by rubber particles. The blend of styrene-acrylonitrile random copolymer (abbreviated as SAN)and SAN grafted on polybutadiene (abbreviated as SAN-g-PBd; the SAN chain of SAN-g-PBd abbreviated as g-SAN)is one of the most important copolymer alloys. Transmission Electron Microscope (TEM) was employed to determine the relationship between the morphology and crazing of the blend.展开更多
The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomen...The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomenological or empirical formulas.In this study,we present a physics-guided machine learning(ML)framework to model shear and craze in polymeric materials.The effects of all three principal stresses for the craze initiation are considered other than the maximum tensile principal stress solely in previous works.We implemented a finite element framework through a user-defined material subroutine and applied the constitutive model to the deformation in three polymers(PLA 4060D,PLA 3051D,and HIPS).The result shows that our ML-based model can predict the stress-strain and volume-strain responses at different strain rates with high accuracy.Notably,the ML-based approach needs no assumptions about yield criteria or hardening laws.This work highlights the potential of hybrid physics-ML paradigms to overcome the trade-offs between model complexity and accuracy in polymer mechanics,paving the way for computationally efficient and generalizable constitutive models for thermoplastic materials.展开更多
Labubu has become a global star,from Paris and New York to London and Milan.These charming figurines from Chinese toy manufacturer Pop Mart,with their soft fur,expressive eyes,pointed teeth and rabbit ears,have captiv...Labubu has become a global star,from Paris and New York to London and Milan.These charming figurines from Chinese toy manufacturer Pop Mart,with their soft fur,expressive eyes,pointed teeth and rabbit ears,have captivated buyers both in shops and online.展开更多
An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding an...An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.展开更多
The tensile-shear failure zone of the laminated damping steel sheet was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It is found that there exists cohesive failure in polymer sand...The tensile-shear failure zone of the laminated damping steel sheet was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It is found that there exists cohesive failure in polymer sandwich and sub-boundary failure between the steel sheet and the polymer. The sub-boundary layer is dominantly polymer material. The tensile-shear failure of the laminated damping steel sheet is a process during which the crazes form, grow up and merge into cracks.展开更多
Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which...Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which is assigned to glass transition peak of craze fibrils. The decreaseof glass transition temperature of polymer in craze fibrils is due to the high values of surface tovolume ratio. The glass transition temperature ratio of craze fibrils to bulk material （T;/Tg） hasbeen expressed as a function of the fibrils diameter （d）. From T;of craze fibrils,the value of fibrildiameter can be calculated. Annealing the crazed specimen at room temperature makes the fibrilsplastically deform and cause the fibrils to thin slightly,whereas annealing the crazed specimen atthe temperature near T;of the craze fibrils makes the fibrils bundle together.展开更多
“Have you learned any Chinese today?”has become a“top searched item”worldwide.With the rapid rise of China’s international status and its continuing endeavor to open up to the outside world,Chinese language,which...“Have you learned any Chinese today?”has become a“top searched item”worldwide.With the rapid rise of China’s international status and its continuing endeavor to open up to the outside world,Chinese language,which is imbued with profound Chinese cultural connotations,has come into the global spotlight,and become an important language for international cultural exchanges.展开更多
Pluta polarizing interference microscope was used to follow the crazing that occur on the surface of stretched polypropylene fibres at different drawing conditions. The samples were stretched until crazing initiated, ...Pluta polarizing interference microscope was used to follow the crazing that occur on the surface of stretched polypropylene fibres at different drawing conditions. The samples were stretched until crazing initiated, and then craze propagation was monitored as a function of drawing speed and test temperature. The effect of craze dimension on their propagation velocity was taken into account. Three-dimensional birefringence profile for crazed polypropylene fibre has been demonstrated to investigate the birefringence of crazed fibre at different test times for fixed drawing speed value. Also the mean birefringence values of crazed polypropylene fibres were calculated and the results showed that, these values increased with the areal craze density. Video images were used to calculate the craze velocity. Optical micrographs and microinterferograms were presented for demonstrations.展开更多
In recent years, more and more people choose to become civil servants for stability of the work and respect of the society. Civil servants not only have a better treatment, but also a higher social status. However, th...In recent years, more and more people choose to become civil servants for stability of the work and respect of the society. Civil servants not only have a better treatment, but also a higher social status. However, the condition is not true in England. This thesis will demonstrate the current condition of ＂Government Office Worker Craze＂, meanwhile, analyze the reasons of this phenomenon by comparing with England. The thesis will firstly display the advantages and disadvantages of this phenomenon; then demonstrate traditional understanding of the two countries separately to find out common characters; the reason of ＂Government Office Worker Craze ＂ in China by exploring the historical cultures; finally, the thesis shows intersections between the two countries and give proper suggestions.展开更多
正At 19 o'clock, October 11th, Beijing time, the Swedish Academy awarded the 2012 Nobel Prize for Literature to the Chinese writer Mo Yan. Within several hours, Mo Yan's works were struck by the "Nobel ef...正At 19 o'clock, October 11th, Beijing time, the Swedish Academy awarded the 2012 Nobel Prize for Literature to the Chinese writer Mo Yan. Within several hours, Mo Yan's works were struck by the "Nobel effect", sales shooting up in both bookstores and online marts. Some websites also jumped on the bandwagon and put up a reservation service for the new editions.展开更多
Shandong Province is currently basking in the limelight of a tourism boom,fueled by the BBQ craze that has seen foodies from all over the country lining up to indulge in a fusion of protein and pancakes.But hold the s...Shandong Province is currently basking in the limelight of a tourism boom,fueled by the BBQ craze that has seen foodies from all over the country lining up to indulge in a fusion of protein and pancakes.But hold the skewers!For tourists looking to nurture their minds as well as their rumbling bellies,Qufu city might also be the perfect place for a fim-filled long weekend.展开更多
The animated film,Ne Zha 2,became a blockbuster this year.Its soaring box-office receipts became a vivid showcase of the innovative vitality,charm and strength of Chinese culture.The film not only took the world by st...The animated film,Ne Zha 2,became a blockbuster this year.Its soaring box-office receipts became a vivid showcase of the innovative vitality,charm and strength of Chinese culture.The film not only took the world by storm,it also ignited a travel craze among fans,who were eager to explore locations associated with the film and its mythological roots.展开更多
Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with comp...Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with computer image analysis (CIA) and the transition of shear yielding zone (A_(sh)) with rubber volume fraction (V_f) was also manipulated. Results showed that the B-D transition of impact strength of blends corresponded to the fracture mechanism in PP/EPDM blends, from matrix crazing to matrix shear yielding. In addition, two new parameters, density of energy dissipation for crazing zone (F_(cz)) and for shear yielding zone (F_(sh)), are first obtained in this paper. The value of F_(sh) is about four times larger than that of F_(cz) for PP/EPDM blends, which confirmed that the matrix shear yielding is a more effective way of energy dissipation in blends.展开更多
There is a new craze among young people—flocking to so-called kuakuaqun, or flattery groups, on the Internet, where they praise one an other, at times even paying to be exaggeratedly complimented.
基金This work was supported by the National Key Projects for Fundamental Research--"Macromolecular Condensed State",The State Science and Technology Commission of China and by the Science Foundation of PPLAS
文摘The crazing of polyphenylquinoxaline (PPQ-E) films during in situ stretching has been observed by SEM. The crazing phenomena and craze morphology of PPQ-E films were interpreted. The strain values at critical crazing and yielding and the craze stability of PPQ-E samples depend on the thermal-dealing condition for the samples. From the point of view of cohesional entanglements and energy absorbed by samples, the experiment results were explained.
基金funding from the Ministry of Science and Higher Education of the Russian Federation(Agreement No.075-15-2020-794)。
文摘This work highlights the benefits of environmental crazing for the control over the hydrophilic-lipophilic balance of glassy amorphous and semicrystalline polymers:poly(ethylene terephthalate)(PET)and biodegradable polycaprolactone(PCL).Task-oriented encapsulation of diverse commercial and natural hydrophilic(polyethyleneoxide,polyvinylpyrrolidone,gelatin)and hydrophobic vip additives(perfluoroorgano siloxanes,water-repellent impregnation)into mesoporous host polymer(PET,PCL)matrixes allows targeted control over the wettability of the resultant nanocomposite materials.Depending on the nature of the vip additive,the properties of the modified polymers can be varied from hydrophilic to hydrophobic:contact angle(CA)of PET can be adjusted from 47_(⊥)/38_(||)to 130_(⊥)/117_(||)°(for initial PET,CA=82°)and CA of PCL from 40°to 114°(for initial PCL CA=75°).The unique benefits of environmental crazing for structural modification are related to the universal character of this approach which can be applied to a broad range of polymers and allows preparation of diverse high-performance materials with tunable hydrophilic-lipophilic balance.
文摘A method to quantify crazing deformations by tensile tests for polystyrene （PS） and polyolefin elastomer （POE） blends was investigated. The toughness of PS/POE blends, reflected by the Charpy impact strength, increased with the content of POE. SEM micrographs showed the poor compatibility between PS and POE. In simple tensile tests, it is very easy to achieve the ratio of crazing deformation, i.e. K by measuring the size changes of samples. The K values decreased with increasing the content of POE, and the deformations of PS/POE blends were dominated by crazing. The plots of the change of volume （△V） against longitudinal variation （△I） showed a linear relationship, and the slope of lines decreased with the content of POE. Measuring samples at the tensile velocities of 5 mm/min, 50 mm/min, and 500 mm/min respectively, the K values kept unchanged for each PS/POE blends.
基金financially supported by the National Natural Science Foundation of China (Nos. 21704003 and 51673013)the Foundation for Innovative Research Groups of the NSF of China (No. 51521062)。
文摘The nanoparticle(NP) functionalization is an effective method for enhancing their compatibility with polymer which can influence the fracture property of the polymer nanocomposites(PNCs). This work aims to further understand the cavitation and crazing process, hoping to uncover the fracture mechanism on the molecular level. By adopting a coarse-grained molecular dynamics simulation, the fracture energy of PNCs first increases and then decreases with increasing the NP functionalization degree α while it shows a continuous increase with increasing the interaction εpA between polymer and modified beads. The bond orientation degree is first characterized which is referred to as the elongation. Meanwhile, the stress by polymer chains is gradually reduced with increasing the α or the εpA while that by NPs is enhanced.Furthermore, the percentage of stress by polymer chains first increases and then decreases with increasing the strain while that by NPs shows a contrast trend. Moreover, the number of voids is quantified which first increases and then decreases with increasing the strain which reflects their nucleation and coalescence process. The voids prefer to generate from the polymer-NP interface to the polymer matrix with increasing α o r εpA.As a result, the number of voids first increases and then decreases with increasing α while it continuously declines with the εpA. In summary, our work provides a clear understanding on how the NP functionalization influences the cavitation and crazing process during the fracture process.
文摘Glassy polymers can be substantially toughened by incorporation of rubber particles at a certain volume percentage. The toughness is related to crazing initiated by rubber particles. The blend of styrene-acrylonitrile random copolymer (abbreviated as SAN)and SAN grafted on polybutadiene (abbreviated as SAN-g-PBd; the SAN chain of SAN-g-PBd abbreviated as g-SAN)is one of the most important copolymer alloys. Transmission Electron Microscope (TEM) was employed to determine the relationship between the morphology and crazing of the blend.
基金supported by the National Natural Science Foundation of China(NSFC)Excellent Research Group Program for“Multiscale Problems in Nonlinear Mechanics”(Grant No.12588201)。
文摘The inelastic behavior of thermoplastic polymers may involve shearing and crazing,and both depend on temperature and strain rate.Traditional constitutive models account for temperature and strain rate through phenomenological or empirical formulas.In this study,we present a physics-guided machine learning(ML)framework to model shear and craze in polymeric materials.The effects of all three principal stresses for the craze initiation are considered other than the maximum tensile principal stress solely in previous works.We implemented a finite element framework through a user-defined material subroutine and applied the constitutive model to the deformation in three polymers(PLA 4060D,PLA 3051D,and HIPS).The result shows that our ML-based model can predict the stress-strain and volume-strain responses at different strain rates with high accuracy.Notably,the ML-based approach needs no assumptions about yield criteria or hardening laws.This work highlights the potential of hybrid physics-ML paradigms to overcome the trade-offs between model complexity and accuracy in polymer mechanics,paving the way for computationally efficient and generalizable constitutive models for thermoplastic materials.
文摘Labubu has become a global star,from Paris and New York to London and Milan.These charming figurines from Chinese toy manufacturer Pop Mart,with their soft fur,expressive eyes,pointed teeth and rabbit ears,have captivated buyers both in shops and online.
基金Project(51275185)supported by the National Natural Science Foundation of China
文摘An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.
文摘The tensile-shear failure zone of the laminated damping steel sheet was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It is found that there exists cohesive failure in polymer sandwich and sub-boundary failure between the steel sheet and the polymer. The sub-boundary layer is dominantly polymer material. The tensile-shear failure of the laminated damping steel sheet is a process during which the crazes form, grow up and merge into cracks.
文摘Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which is assigned to glass transition peak of craze fibrils. The decreaseof glass transition temperature of polymer in craze fibrils is due to the high values of surface tovolume ratio. The glass transition temperature ratio of craze fibrils to bulk material （T;/Tg） hasbeen expressed as a function of the fibrils diameter （d）. From T;of craze fibrils,the value of fibrildiameter can be calculated. Annealing the crazed specimen at room temperature makes the fibrilsplastically deform and cause the fibrils to thin slightly,whereas annealing the crazed specimen atthe temperature near T;of the craze fibrils makes the fibrils bundle together.
文摘“Have you learned any Chinese today?”has become a“top searched item”worldwide.With the rapid rise of China’s international status and its continuing endeavor to open up to the outside world,Chinese language,which is imbued with profound Chinese cultural connotations,has come into the global spotlight,and become an important language for international cultural exchanges.
文摘Pluta polarizing interference microscope was used to follow the crazing that occur on the surface of stretched polypropylene fibres at different drawing conditions. The samples were stretched until crazing initiated, and then craze propagation was monitored as a function of drawing speed and test temperature. The effect of craze dimension on their propagation velocity was taken into account. Three-dimensional birefringence profile for crazed polypropylene fibre has been demonstrated to investigate the birefringence of crazed fibre at different test times for fixed drawing speed value. Also the mean birefringence values of crazed polypropylene fibres were calculated and the results showed that, these values increased with the areal craze density. Video images were used to calculate the craze velocity. Optical micrographs and microinterferograms were presented for demonstrations.
文摘In recent years, more and more people choose to become civil servants for stability of the work and respect of the society. Civil servants not only have a better treatment, but also a higher social status. However, the condition is not true in England. This thesis will demonstrate the current condition of ＂Government Office Worker Craze＂, meanwhile, analyze the reasons of this phenomenon by comparing with England. The thesis will firstly display the advantages and disadvantages of this phenomenon; then demonstrate traditional understanding of the two countries separately to find out common characters; the reason of ＂Government Office Worker Craze ＂ in China by exploring the historical cultures; finally, the thesis shows intersections between the two countries and give proper suggestions.
文摘正At 19 o'clock, October 11th, Beijing time, the Swedish Academy awarded the 2012 Nobel Prize for Literature to the Chinese writer Mo Yan. Within several hours, Mo Yan's works were struck by the "Nobel effect", sales shooting up in both bookstores and online marts. Some websites also jumped on the bandwagon and put up a reservation service for the new editions.
文摘Shandong Province is currently basking in the limelight of a tourism boom,fueled by the BBQ craze that has seen foodies from all over the country lining up to indulge in a fusion of protein and pancakes.But hold the skewers!For tourists looking to nurture their minds as well as their rumbling bellies,Qufu city might also be the perfect place for a fim-filled long weekend.
文摘The animated film,Ne Zha 2,became a blockbuster this year.Its soaring box-office receipts became a vivid showcase of the innovative vitality,charm and strength of Chinese culture.The film not only took the world by storm,it also ignited a travel craze among fans,who were eager to explore locations associated with the film and its mythological roots.
基金Project supported by the National Natural Science Foundation of China.
文摘Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with computer image analysis (CIA) and the transition of shear yielding zone (A_(sh)) with rubber volume fraction (V_f) was also manipulated. Results showed that the B-D transition of impact strength of blends corresponded to the fracture mechanism in PP/EPDM blends, from matrix crazing to matrix shear yielding. In addition, two new parameters, density of energy dissipation for crazing zone (F_(cz)) and for shear yielding zone (F_(sh)), are first obtained in this paper. The value of F_(sh) is about four times larger than that of F_(cz) for PP/EPDM blends, which confirmed that the matrix shear yielding is a more effective way of energy dissipation in blends.
文摘There is a new craze among young people—flocking to so-called kuakuaqun, or flattery groups, on the Internet, where they praise one an other, at times even paying to be exaggeratedly complimented.
