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Reactive processing of poly(lactic acid)/poly(ethylene octene) blend film with tailored interfacial intermolecular entanglement and toughening mechanism

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Journal of Materials Science & Technology 2022年第3期98卷 186-196页

作者： Wenjun He Lin Ye Phil Coates Fin Caton-Rose Xiaowen Zhao State Key Laboratory of Polymer Materials Engineering of China Polymer Research Institute of Sichuan UniversityChengdu 610065China School of Engineering Design and TechnologyUniversity of BradfordBradfordUK

In order to obtain a uniform and effectively toughened poly(lactic acid)film by blending with low content of poly(ethylene octene)(POE)with high elasticity,the tailored interfacial intermolecular interaction and entanglement between the two phases of the PLA/POE blend was innovatively constructed via the facile reactive melt blending process through the reaction of the epoxy/anhydride groups grafted on the POE chains with the end groups of PLA chains(PLA/GPOE-MPOE).It was observed that POE domains were embedded tightly in PLA matrix with a fuzzy interface and abundant interface transition area,and the impact fractured surface of the blend showed an obvious plastic deformation with less occurrence of fibrillation of PLA matrix or interfacial de-bonding.Compared with neat PLA and directly blended PLA/POE blends,the PLA/GPOE-MPOE blend exhibited much higher complex viscosity/storage modulus,much lower tanδvalues in the terminal region,and obvious strain-hardening behavior.The deviation in viscoelastic behavior of PLA/GPOE-MPOE from linear PLA indicated the enhanced molecular entanglement between the long-branched chains,resulting in an enhancement of the stretching ability during biaxial drawing of the blend.Uniform PLA/GPOE-MPOE films with draw ratio as high as 7×7 were obtained through biaxial stretching,which showed much higher tensile strength and the elongation at break than that of neat PLA and PLA/POE film.This work provides a facile method for fabricating toughening PLA films with application potentials.

关键词： Poly(lactic acid)/poly(ethylene octene)(PLA/POE)blend film Reactive processing Tailored interfacial intermolecular interaction Long-chain branched structure toughening mechanism

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Preparation and toughening mechanism of Al_(2)O_(3) composite ceramics toughened by B_(4)C@TiB_(2) core–shell units

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Journal of Advanced Ceramics 2023年第12期12卷 2371-2381页

作者： Yingjie Shi Weixing Li Xiaorong Zhang Jiachao Jin Jilin Wang Yu Dong Jingbo Mu Guangsuo Wang Xiaoliang Zhang Zhixiao Zhang Key Laboratory of New Inorganic Nonmetallic Composites of Handan College of Materials Science and EngineeringHebei University of EngineeringHandan 056038China Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province College of Mechanical and Equipment EngineeringHebei University of EngineeringHandan 056038China College of Materials Science and Engineering Guilin University of TechnologyGuilin 532100China School of Civil and Mechanical Engineering Curtin UniversityPerth 6845Australia

In this paper, the concept of incorporating core–shell structured units as secondary phases totoughen Al_(2)O_(3) ceramics is proposed. Al_(2)O_(3) composite ceramics toughened by B_(4)C@TiB_(2) core–shellunits are successfully synthesized using a combination of molten salt methodology and spark plasmasintering. The synthesis of B_(4)C@TiB_(2) core–shell toughening units stems from the prior production ofcore–shell structural B_(4)C@TiB_(2) powders, and this core–shell structure is effectively preserved withinthe Al_(2)O_(3) matrix after sintering. The B_(4)C@TiB_(2) core–shell toughening unit consists of a micron-sizedB4C core enclosed by a shell approximately 500 nm in thickness, composed of numerous nanosizedTiB2 grains. The regions surrounding these core–shell units exhibit distinct geometric structures andencompass multidimensional variations in phase composition, grain dimensions, and thermal expansioncoefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks inmultiple dimensions. This behavior consumes a considerable amount of crack propagation energy,thereby enhancing the fracture toughness of the Al_(2)O_(3) matrix. The resulting Al_(2)O_(3) composite ceramicsdisplay relative density of 99.7%±0.2%, Vickers hardness of 21.5±0.8 GPa, and fracture toughness6.92±0.22 MPa·m1/2.

关键词： Al_(2)O_(3)composite ceramics microstructure design core-shell structure toughening mechanism spark plasma sintering(SPS)

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Self-assembling nacre-like high-strength and extremely tough polymer composites with new toughening mechanism

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Journal of Materials Science & Technology 2023年第5期136卷 236-244页

作者： Yu Bu Xu Wang Xiuming Bu Zhengyi Mao Zhou Chen Zebiao Li Fengqian Hao Johnny C.Ho Jian Lu CityU-Shenzhen Futian Research Institute Shenzhen 518045China Centre for Advanced Structural Materials City University of Hong Kong Shenzhen Research InstituteGreater Bay Joint DivisionShenyang National Laboratory for Materials Science8 Yuexing 1st RoadShenzhen Hi-Tech Industrial ParkNanshan DistrictShenzhen 518000China MOE Key Laboratory of Impact and Safety Engineering Ningbo UniversityNingbo 315211China Department of Materials Science and Engineering City University of Hong KongHong Kong SAR 999077China Department of Mechanical Engineering City University of Hong KongHong Kong SAR 999077China

Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of these properties.Here,a self-assembling nacre-like polymer composite is designed to achieve ex-tremely tough with increasing strength.This special design significantly improved polymer’s mechanical properties,including an ultra-high fracture strain of 1180%,a tensile strength of 55.4 MPa and a toughness of 506.9 MJ/m^(3),which far exceed the highest values previously reported for polymer composites.This ex-cellent combination of properties can be attributed to a novel toughening mechanism,achieved by the synergy of the domain-limiting effect of metallic glass fragments with the strain-gradient-induced orien-tation and crystallisation within the polymer during stretching.Our approach opens a promising avenue for designing robust polymer materials in armour and aerospace engineering for a range of innovative applications.

关键词： Polymer composites Metallic glass thin film Toughness toughening mechanism Nacre-like fracture

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High MXene loading, nacre-inspired MXene/ANF electromagnetic interference shielding composite films with ultralong strain-tofailure and excellent Joule heating performance

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Nano Research 2024年第3期17卷 2061-2069页

作者： Jiaen Wang Tianliang Song Wei Ming Moxi Yele Longfu Chen Hao Zhang Xiaojuan Zhang Benliang Liang Guangsheng Wang School of Physical Science and Engineering Beijing Jiaotong UniversityBeijing 100044China College of Chemistry and Materials Engineering Beijing Technology and Business UniversityBeijing 100048China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education School of ChemistryBeihang UniversityBeijing 100191China

The high power density and intelligence of next-generation flexible electronic devices bring many challenges to fabricate flexible composite films with electromagnetic interference(EMI)shielding effectiveness(SE)property and excellent toughness via a simple method.Herein,inspired by the layered structure and biopolymer matrix networks in natural nacre,nacre-like layered Ti_(3)C2TX(MXene)/aramid nanofiber(ANF)films were fabricated through sol-gel,vacuum-assisted filtration,and hot-pressing.Three-dimensional(3D)interconnected aramid nanofibers networks between adjacent layered MXene result in an ultralong strain-to-failure of the film.Even though the functional filler MXene contents are as high as 60 wt.%and 70 wt.%,the strain-to-failure of the films could reach astonishing values of 18.34%±1.86%and 14.43%±1.26%,respectively.And the tensile strength could maintain about 85 MPa.Excitingly,with such a high filler,the film can also withstand double folding and vigorous rubbing without damage,which could better adapt to a harsh application environment.The result means that this work provides a convenient way to prepare other high functional filler composite films with excellent mechanical performance.The EMI SE values could reach 45 and 52.15 dB at 60 wt.%and 70 wt.%MXene in 8.2–12.4 GHz.Meanwhile,the films have prominent Joule heating properties,high sensitivity(<15 s),small voltage operation(0.5 V),and high operation constancy(1300 s).Therefore,nacre-inspired MXene/ANF composite films in this work have ability to apply in many areas including communication technology,military,and aerospace.

关键词： bioinspired aramid nanofiber networks ultralong strain-to-failure toughening mechanism electromagnetic interference shielding

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toughening mechanism of lined Al_2O_3-ZrO_2 multiphaseceramics in SHS composite pipes

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Journal of University of Science and Technology Beijing 2006年第2期13卷 178-182页

作者： Guibo Yu Wen Yan Shuhai Wang Baoxin Su Baolai Tan Mechanical Engineering College of Shijiazhuang Shijiazhuang 050003 China

Hypoeutectic and hypereutectic Al2O3-ZrO2 multiphase ceramics-lined composite pipes were produced by using the gravitational separation self-propagate high-temperature synthesis （SHS） process. The microstructure of the ceramics was observed by means of SEM and EPMA. The fracture toughness of the multiphase ceramics was tested by using the Vickers indentation method. The fracture toughness of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.96 MPa·m^1/2 and that of hypoeutectic Al2O3-ZrO2 multiphase ceramics is 15.23 MPa·m^1/2. The toughening mechanisms were systematically investigated by means of SEM and XRD. The results show that the bridging toughening mechanism, stress induced ZrO2 transformation toughening mechanism, and microcrack toughening mechanism are the predominant toughening mechanism.

关键词： SHS multiphase ceramics eutectic structure toughening mechanism

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toughening mechanism of Nanocomposite Physical Hydrogels Fabricated by a Single Gel Network with Dual Crosslinking-- The Roles of the Dual Crosslinking Points

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Chinese Journal of Polymer Science 2017年第1期35卷 25-35页

作者： fu-kuan shi ming zhong li-qin zhang xiao-ying liu 谢续明 Key Laboratory of Advanced Materials (MOE) Department of Chemical Engineering Tsinghua University Beijing 100084 China

A facile method to fabricate tough and highly stretchable polyacrylamide （PAM） nanocomposite physical hydrogel （NCP gel） was proposed. The hydrogels are dually crosslinked single network with the PAM grafted vinyl hybrid silica nanoparticles （VSNPs） as the analogous covalent crosslinking points and the reversible hydrogen bonds among the PAM chains as the physical crosslinking points. In order to further elucidate the toughening mechanism of the PAM NCP gel, especially to understand the role of the dual crosslinking points, the PAM hybrid hydrogels （H gels） and a series of poly（acrylamide-co-dimethylacrylamide）（P（AM-co-DMAA）） NCP gels were designed and fabricated. Their mechanical properties were compared with those of the PAM NCP gels. The PAM H gels are prepared by simply mixing the PAM chains with bare silica nanoparticles （SNPs）. Relative to the poor mechanical properties of the PAM H gel, the PAM NCP gel is remarkably tough and stretchable and also generates large number of micro-cracks to stop notch propagation, indicating the important role of PAM grafted VSNPs in toughening the NCP gel. In the P（AM-co-DMAA） NCP gels, the P（AM-co- DMAA） chains are grafted on VSNPs and the polydimethylacrylamide （PDMAA） only forms very weak hydrogen bonds between themselves. It is found that mechanical properties of the PAM NCP gel, such as the tensile strength and the elongation at break, are enhanced significantly, but those of the P（AM-co-DMAA） NCP gels decreased rapidly with decreasing AM content. This result reveals the role of the hydrogen bonds among the grafted polymer chains as the physical crosslinking points in toughening the NCP gel.

关键词： Dual crosslinking single network Nanocomposite physical hydrogel toughening mechanism

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Microstructure, mechanical properties and toughening mechanism of directional Fe2B crystal in Fe-B alloy with trace Cr addition

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Journal of Materials Science & Technology 2020年第22期54卷 172-179页

作者： Yongxin Jian Zhifu Huang Xiaoting Liu Jialin Sun Jiandong Xing State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXian710049China

Exploring the effective way to improve Fe2 B's toughness has always been the hot topic in the researches of Fe-B wear resistant alloys.In the present work,the effects of Cr on the microstructure,mechanical properties and lattice structure of directional Fe2 B have been investigated.The affecting mechanism of Cr addition has been discussed according to the experimental and first-principle calculation analysis.The results show Cr addition can improve the toughness of directional Fe2 B on the longitudinal sections perpendicular to(002) crystal plane,without sacrificing the hardness distinctly.The toughening mechanism by Cr substitution has been revealed:Cr addition enriches the electron density between the B atoms along [002] direction,contributing to the shrinkage of the bond length and the enhancement of the bond strength of B-B bonds.The obtained results provide insight into the intrinsic reason for toughening Fe2 B by Cr doping.

关键词： Directional Fe2B Cr addition Lattice evolution toughening mechanism

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Effect of lamellar structural parameters on the bending fracture behavior of AA1100/AA7075 laminated metal composites

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Journal of Materials Science & Technology 2022年第4期99卷 28-38页

作者： Taiqian Mo Zejun Chen Dayu Zhou Guangming Lu Yongmeng Huang Qing Liu Joint International Research Laboratory for Light Alloys Ministry of EducationCollege of Materials Science and EngineeringChongqing UniversityChongqing 400044China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 210009China

The lamellar structure has an important impact on the mechanical properties of dissimilar laminated metal composites(LMCs),including the thickness ratio of dissimilar metal constituent layers and the number of layers.AA1100 and AA7075 with thickness ratios of 1:4 and 3:4 were fabricated for multilayer AA1100/AA7075 LMCs by hot accumulative roll bonding(ARB)technology.The bending fracture characteristics of AA1100/AA7075 LMCs with different thickness ratios and numbers of constituent layers were investigated.The research results indicated that AA1100/AA7075 LMCs with a low thickness ratio exhibited better bending ductility and toughness than those with a high thickness ratio,which was attributed to the crack growth resistance caused by the thickness of the soft AA1100 layer.The toughening mechanism introduced by crack deflection or arresting contributed to the enhancement in the toughness of the LMCs compared with that of the single 7075 Al layer.The bonding interfaces of AA1100/AA7075 LMCs with different numbers of layers are continuous and straight due to the high ARB temperature.A decrease in bending toughness was observed as the number of layers increased.Unlike LMCs with a low number of layers,crack deflection or interface delamination is also considered a main toughening mechanism in dissimilar LMCs in addition to the thickness effect.

关键词： Laminated metal composite Mechanical properties Bending Fracture behavior toughening mechanism

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A Review of Experimental Research on the Mode I Fracture Behavior of Bamboo

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Journal of Renewable Materials 2023年第6期11卷 2787-2808页

作者： Yue Chen Haitao Li Lei Gao Wei Xu Rodolfo Lorenzo Milan Gaff College of Civil Engineering Nanjing Forestry UniversityNanjing210037China Joint International Research Laboratory for Bio-Composite Building Materials and Structures Nanjing Forestry UniversityNanjing210037China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing211106China University College London LondonWC1E 6BTUK Department of Furniture Design and Habitat BrnoMendel University in BrnoBrno61300Czech Republic Faculty of Civil Engineering Experimental CentreCzech Technical University in PragueThakurova 7Prague16629Czech Republic

Bamboo is an eco-friendly material with light weight,high strength,short growth cycle and high sustainability,which is widely used in building structures.Engineered bamboo has further promoted the development of modern bamboo structures due to its unrestricted size and shape.However,as a fiber-reinforced material,fracture damage,especially Mode I fracture damage,becomes the most likely damage mode of its structure,so Mode I fracture characteristics are an important subject in the research of mechanical properties of bamboo.This paper summarizes the current status of experimental research on the Mode I fracture properties of bamboo based on the three-point bending(TPB)method,the single-edge notched beam(SENB)method,the compact tension(CT)method and the double cantilever beam(DCB)method,compares the fracture toughness of different species of bamboo,analyzes the toughening mechanisms and fracture damage modes,discusses the applicability of different theoretical calculation methods,and makes suggestions for future research priorities,aiming to provide a reference for future research and engineering applications in related fields.

关键词： Mode I fracture properties test method toughening mechanism fracture damage modes

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ON THE EFFECT OF NANO-PARTICLE CLUSTERING ON toughening OF NANO-COMPOSITE CERAMICS

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Acta Mechanica Sinica 2002年第2期18卷 146-158页

作者：董照旭方岱宁苏爱嘉 Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China Department of Mechanical EngineeringThe University of Hong KongHong KongChina

In this paper,two and three-dimensional clustering models are de-veloped to characterize the effect of nano-particle clustering on toughening of nano-composite ceramics.It is found that crack pinning toughens the nano-compositeceramics because a higher stress intensity factor is needed for crack to propagatearound or to pull-out the nano-particle.The nano-particle along the grain boundarysteers the crack into the matrix grain due to the strong cohesion between the nano-particle and the matrix.Since the fracture resistance of the grain boundary is lowerthan that of the grain lattice,the higher the probability of transgranular fractureinduced by nano-particles,the tougher is the nano-composite.However,both crackpinning and transgranular fracture are affected by nano-particle clustering.Nano-particle clustering,which increases with increasing volume fraction of nano-particles,leads to reduction of both the strength and toughness of the nano-composite ceram-ics.The larger the size of the clustered particle,and the more defects it contains,theeasier it is for the crack to pass through the clustered particle,which means that thenano-particle clustering can reduce toughening induced by crack pinning and trans-granular fracture.The theoretical prediction,based on the combination of the threemechanisms of nano-particles,is in agreement with the experimental data.

关键词： nano-particle clustering ceramic fracture toughening mechanism

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