2023 Vol. 40, No. 4

Influencing factors and research progress of self-piercing riveting process for resin matrix composite
FU Pingpo, ZENG Xiangrui, DING Hua, ZHANG Nana, LUO Shiqing
2023, 40(4): 1819-1840. doi: 10.13801/j.cnki.fhclxb.20220707.004
The application of hybrid material body structure combined with composite material and lightweight or high strength metal is an important way of automobile lightweight, and the effective connection between composites and heterogeneous materials has become the key link of hybrid material body manufacturing. Self-piercing riveting (SPR) technology, with its high quality and efficiency, shows advantages and good applicability in composite material connection and has received extensive attention and research. Summarizing the research results of composite SPR connection in recent years, it is found that: The strength values of SPR joints between composite materials and aluminum alloy sheets are mostly concentrated at about 4 kN, which is comparable to that of SPR joints between metal plates. The main factors affecting the joint performance are the property of base material, rivet structure, riveting process parameters and service condition, meanwhile, the key points to improve the joint performance are to enhance the strength of the composite sheet, reduce the internal riveting damage and defects of the composite material, and improve the mechanical internal locking combination between the rivet foot and the lower sheet. In addition, when the SPR joint combined with bonding process, its comprehensive performance can be significantly improved.
Research progress of photocatalytic CO2 reduction based on CsPbBr3 perovskite
HUANG Xing, ZHU Wenqiang, LI Zhenzhen
2023, 40(4): 1841-1856. doi: 10.13801/j.cnki.fhclxb.20221019.001
Exploring green development and solving the energy crisis has become a trend of commercial development in recent years. Metal halide perovskites have attracted great attentions due to their unique photocatalytic properties. Among them, CsPbBr3 perovskite has high photocatalytic activity and excellent stability, and has developed rapidly in photocatalytic CO2 reduction. Under the trend of energy development, reducing carbon emissions and catalytic reduction of CO2 as fuels are research hotspots and main approaches. However, the poor CO2 adsorption capacity, severe charge recombination, and low charge efficiency of pure CsPbBr3 seriously hinder the commercialization of perovskite photocatalysis. In order to solve a series of problems in photocatalysis of pure CsPbBr3 materials, surface modification the of CsPbBr3 perovskite or construct on of multicomponent composites is currently the most economical and promising solution. In this review, we systematically review the latest research on photocatalytic CO2 reduction of CsPbBr3 perovskites and their composites, discuss the photocatalytic reaction mechanism of CsPbBr3 perovskites, and then propose obstacles to development. Finally, we expect this review to provide new exploration directions for building more stable, efficient and sustainable photocatalysts for CO2 emission reduction.
Research progress of organic-inorganic composite electrolytes for all-solid-state lithium batteries
SONG Xin, GAO Zhihao, LUO Lin, MA Kang, ZHANG Jianmin
2023, 40(4): 1857-1878. doi: 10.13801/j.cnki.fhclxb.20221031.002
At present, lithium-ion batteries face many problems due to the use of liquid electrolytes, such as narrow operating temperature range, poor thermal stability, easy leakage, and formation of lithium dendrites. The development of all-solid-state lithium batteries is one of the feasible ways to improve the energy density and safety of batteries. In this paper, the types and conduction mechanisms of solid electrolytes are firstly summarized, and then the selection of polymer matrix and lithium salt in organic-inorganic composite solid electrolytes and the effects of inorganic fillers of different dimensions on electrolyte properties, especially mechanical properties, are described in detail. Finally, the research summary and prospect of organic-inorganic composite solid electrolytes are presented.
Classification of conductive composite hydrogels and their application in flexible wearable devices
JIANG Wenjing, LIAO Jingwen, ZHANG Xuehui, WANG Yanqin
2023, 40(4): 1879-1895. doi: 10.13801/j.cnki.fhclxb.20220926.002
In recent years, hydrogel-based conductive materials as flexible wearable devices have attracted wide attention. Flexible wearable devices can not only be used to collect physiological signals of human body for remote health monitoring, but also show great application potential in man-machine interface, soft robot and other aspects. Conductive hydrogels with good electrical conductivity, high extensibility, adjustable flexibility, biocompatibility and multiple stimulus response become an ideal material for flexible wearable devices. Up to now, various conductive materials have been widely used to prepare conductive hydrogels. In this paper, conductive composite hydrogels are classified according to conductive materials, including ionic conductive hydrogels (based on salt ions, ionic liquids, polyelectrolytes) and electronic conductive hydrogels (based on conductive polymers, carbon materials, MXene and metal), and then introduce the application progress of conductive hydrogels in flexible wearable devices such as human movement monitoring, health monitoring and human-machine interface.
Research progress on antibacterial textiles of MXene and its composite materials
LI Yanyan, ZHAO Lihuan, YANG Yujie
2023, 40(4): 1896-1912. doi: 10.13801/j.cnki.fhclxb.20220627.002
MXene materials are two-dimensional transition metal carbides, nitrides or carbonitride nanomaterials with two-dimensional layered structures. Due to their excellent physical and chemical properties, MXene materials have been widely used in biosensing, cancer photothermal therapy, antibacterial and other aspects. Based on the research status of antibacterial properties of MXene, the antibacterial mechanism of MXene and its composite materials was explored, the antibacterial properties of MXene and its composite materials and the research progress of antibacterial finishing fabrics, antibacterial fibers and antibacterial dressings were described, and the future research direction of antibacterial textiles based on MXene and its composite materials was proposed.
Direct ink writing of lignin-based composites and their applications
JIANG Bo, GUO Xinyu, JIAO Huan, JIN Yongcan
2023, 40(4): 1913-1923. doi: 10.13801/j.cnki.fhclxb.20221205.002
As the most abundant renewable aromatic biopolymer in nature, lignin recently has received extensive attention in the fields of energy, environment, and medicine. In particular, the use of 3D printing technology to construct lignin-based composites with tunable and desired structures and functions is one of the important ways to pro-mote the high-value utilization of lignin, which can also avoid the negative effects during traditional material preparation that caused by the diverse chemical structure, high polydispersity in molecular weight, and rigid structure of lignin. This paper focuses on the direct ink writing of lignin-based composites, mainly with the achievements and recent progress critically reviewed. Firstly, the structural features of lignin and the technology of direct ink writing are briefly summarized. Subsequently, the structure-rheology behavior relationship during 3D printing of lignin-based composites is discussed. Finally, the functional applications of 3D printed lignin-based composites in engineering, energy, and environment, as well as the potential problems and challenges, are summarized. Further, the main points towards future directions on lignin composites based on direct in writing are also highlighted.
Research progress of MOFs and their derived materials for Li-ion battery anodes
DAI Lianghong, LIU Jinyuan, PENG Hongjian, XIE Youqing
2023, 40(4): 1924-1936. doi: 10.13801/j.cnki.fhclxb.20220727.001
The metal organic frameworks (MOFs) have large specific surface area and tunable pore size, and they are composed of metal ions and organic ligands, both of which have good charge carrying capacity. In recent years, MOFs have attracted widespread attention for Li-ion battery anode materials. The review introduces the commonly used MOFs anode materials for Li-ion batteries (LIBs) and summarizes the modification strategies and research progress of MOFs and their derived materials for Li-ion battery anodes. Finally, the main design principles about the structure and morphology of MOFs anode materials are analyzed systematically, and challenges for the future development of advanced anode materials for LIBs will be considered.
Applications of graphene-organic compound photocatalytic materials
LIU Yangyang, YI Min, CHEN Tao, DONG Shuyu
2023, 40(4): 1937-1950. doi: 10.13801/j.cnki.fhclxb.20220628.003
The great application potential of photocatalysis technology with green and safe characteristics has been shown on the field of energy and environment. Over recent years, the organic photocatalysts have been familiar with their advantages of visible light response, low cost and also some shortcomings. Graphene materials which surface area was large and high carrier mobility have natural advantages in the field of catalyst construction. The graphene-organic semiconductor as an photocatalysis materials, this work introduced three typical graphene-organic photocatalysis materials: Graphene/conjugated polymer, graphene/metal organic framework and graphene/dye and various synthesis methods. This work have discussed some application fields of energy and environment, including photocatalysis of water for hydrogen evolution, CO2 reduction, organic matter degradation, heavy metal ion reduction and bacterial inactivation etc. Some suggestions for future development of the graphene materials with organic compound photocatalyst are given.
Research progress of in-situ fibrous composite foamed material
SUN Junwei, JIANG Jing, ZHAO Na, WANG Xiaofeng, DUAN Tongsheng, LI Qian
2023, 40(4): 1951-1965. doi: 10.13801/j.cnki.fhclxb.20220704.001
In-situ fibrous composite foamed material is one type of foams, which is based on in-situ micro fibrillation (IMF) composites and microcellular foaming technology. In addition to the performance of traditional foamed materials such as light weight, shock absorption, insulation, noise reduction, etc., the presence of fiber network structure constructed in IMF composite can significantly improve the microcellular foaming ability of the matrix. Leading to the in-situ fibrous composite foamed material is a kind of new foam with high strength and functionality. This paper first summarized the fabrication process of IMF composites and regulatory factors. The influence of IMF network structure on the crystallization and rheological behaviors were emphatically analyzed. Then reviewed the preparation and pore structure regulation methods of in-situ fibrous composite foamed materials for various IMF composites and microcellular foaming process. The mechanism of strong mechanical properties and application in the field of heat insulation and oil-water separation were then elaborated and listed. Finally, looking forward to the future research directions of in-situ fibrous composite foamed materials.
Researches and applications of lignin and its derivatives in 3D printing photosensitive resins
WANG Huihui, YANG Jian, YANG Yiluo, GUO Taoli, YANG Shengda, HU Die, PAN Gangyuan, CHENG Zhengbai, CAO Haibing, LIU Hongbin, AN Xingye
2023, 40(4): 1966-1980. doi: 10.13801/j.cnki.fhclxb.20220819.003
It is eagerly necessary to further develop the low-carbon and environmentally friendly 3D printing feedstocks, such as biomass-based three-dimensional (3D) printing photosensitive resin polymers, considering the continuous transformation of social consumption demands to green and sustainable development direction and the proposal of the national “double carbon” strategic goal. Lignin, as the second renewable and green biopolymer after cellulose, has exhibited its great application prospects in 3D printing feedstocks. The aim of this paper is to provide a critical review on the most cutting-edge researches of lignin and its derivatives as biomaterial feedstocks of 3D printing photosensitive resins, including the applications mechanism and performance effects of lignin-based photosensitive oligomers, lignin-derived reactive diluents, lignin-derived photo-initiators, as well as the lignin-based additives. Finally, the challenges and industrial prospects of lignin-based photosensitive resins as 3D printing feedstocks are analyzed and prospected.
Progress of study on cellulose nanocrystals as chiral templates
DENG Yanmei, ZHI Yunfei, SHAN Shaoyun, HU Shuai, ZHANG Churu
2023, 40(4): 1981-1991. doi: 10.13801/j.cnki.fhclxb.20221030.001
Cellulose nanocrystals (CNC) is a kind of nanocellulose with high crystallinity, which is prepared by the acid hydrolysis of natural cellulose. CNC can form iridescent films with chiral nematic liquid crystal phase through evaporation-induced self-assembly (EISA). The preparation process of CNC is simple, and CNC has biological sustainability and inherent chiral nematic structure that shows unique optical properties. Advanced optical materials can be prepared by co-assembling CNC as chiral templates with polymers or inorganic materials, which has a broad application prospect in the fields of sensors, photoelectric devices, and intelligent display. The preparation of CNC, the formation of chiral structure and the study of CNC as template are introduced in this paper, and the application status of CNC in the preparation fields of ordered mesoporous materials, functional nanocomposite membranes and new optical materials are briefly reviewed. Finally, some problems in the preparation and application of CNC chiral materials are summarized, which is expected to provide reference for the application of CNC chiral materials in the future.
Research Progress of Cellulose-based Thermoelectric Composites
CHEN Luzheng, MA Hongliang, LOU Jiang, JIANG Yifei, HAN Wenjia
2023, 40(4): 1992-2003. doi: 10.13801/j.cnki.fhclxb.20220530.004
With the booming development of the global economy, the human demand for energy is increasing, so the research and application of green thermoelectric materials is urgent.As the most abundant natural polymer in nature, cellulose has rich three-dimensional network structure and excellent thermal stability. It is one of the ideal substrates for flexible thermoelectric composite materials. The large-scale development and utilization of cellulose is in line with the concept of green and sustainable development. Cellulose-based thermoelectric composite material can fully convert the waste heat generated by human body and fossil energy into electric energy, which has the advantages of stable performance, green and environmental protection, long service life, low cost and easy processing. This paper summarizes the development status and application field of cellulose matrix composite in recent years, focusing on polymer composite, carbon matrix composite and Bi-Te alloy composite. The challenges of cellulose matrix composites and the future research trends are summarized and discussed.
Progress in improving the mechanical durability of superhydrophobic materials
ZHAO Yamei, HUO Mengdan, CAO Tingting, DING Siqi, CHEN Li
2023, 40(4): 2004-2014. doi: 10.13801/j.cnki.fhclxb.20220923.001
Superhydrophobic materials are widely used in many fields such as antifouling and anticorrosion, underwater drag reduction and oil-water separation due to their unique wettability. However, when most superhydrophobic materials are subjected to external mechanical wear, it is easy to cause the collapse of the surface microstructure or the consumption of low surface energy substances, which affects or loses the superhydrophobic properties. Through the analysis of the surface wetting model, two main ideas for enhancing the mechanical durability of superhydrophobic materials are clarified, and the typical testing methods and characteristics of the mechanical durability of superhydrophobic materials are introduced. Then, based on the analysis and review of the research status and development trends at home and abroad, four strategies to improve the mechanical durability of superhydrophobic materials are summarized, including designing micro-nano multi-level rough structure, introducing polymer bonding layer, constructing self-similar structures and self-healing functionalization. Finally, the challenges to improve the mechanical durability of superhydrophobic materials are summarized, and their future development prospects are prospected.
Resin Polymer Composite
Infrared-assisted automated fiber placement process on the structure and properties of continuous glass fiber reinforced polypropylene composites
JIANG Wei, ZHOU Yue, YANG Fei, HUANG Zhigao, CHEN Cheng, ZHOU Huamin
2023, 40(4): 2015-2025. doi: 10.13801/j.cnki.fhclxb.20220513.004
Compared with laser and hot air heating, infrared (IR) heating has outstanding advantages such as low cost and low pollution, and is an ideal heat source for automated fiber placement (AFP) forming of low-melting thermoplastic composites. However, the coupling of IR-assisted AFP process parameters is strong, and the effects on forming accuracy, defect formation and macroscopic properties are still unclear, and there is a lack of data accumulation of related processes. In this paper, for the IR-assisted AFP in-situ forming process, continuous glass fiber reinforced polypropylene composite unidirectional laminates were prepared by regulating the lay-up pressure and speed, and the effects of lay-up temperature and pressure on the thinning effect, warpage deformation, crystallinity and porosity were investigated, and the influence of structure and defects on the macroscopic mechanical properties such as bending strength and interlaminar shear strength were further investigated. The results show that: Too high temperature leads to severe thinning effect, too low leads to high porosity; Too high forming pressure causes severe warpage and fiber deformation and reduces interlaminar shear strength. Through reasonable control of temperature and pressure, the porosity can be reduced to 1%, which meets the requirement of 2% threshold for civil-composite components; The bending strength of specimens is up to 466 MPa, which is only 6% lower compared with hot pressing forming.
Effect of low-temperature plasma surface modification on the adhesive performance of CFRP
WANG Dawei, LI Ye, LIU Zhihao, ZOU Tianchun
2023, 40(4): 2026-2037. doi: 10.13801/j.cnki.fhclxb.20220516.003
Ar, N2 and O2 were used as low-temperature plasma excitation gases to treat the surface of carbon fiber reinforced plastics (CFRP). The effects of plasma gas, discharge power and treatment time on the physicochemical properties, including wettability, roughness, microscopic morphology and chemical components of CFRP surface, were characterized by contact angle measurement, AFM, SEM and XPS. The adhesive joint property was investigated through tensile shear experiment and failure morphology analysis. Compared with untreated, the tensile shear strength of CFRP adhesive joints after Ar, N2 and O2 plasma treatment can significantly improve the bonding performance of CFRP, and when the plasma discharge power is 800 W and treatment time is 20 s, the adhesive joint strength increases by 138%, 172% and 253%, respectively. The surface test analysis shows that the improvement of CFRP adhesive strength after argon plasma treatment is mainly induced by improving the surface cleanliness and increasing the surface area for interfacial adhesive, and the failure modes of samples changes from interfacial failure to mixed failure mode with cohesive failure as the main mode. Compared with Ar, a greater number of polar chemical groups (—NH2) are generated on the CFRP surface after N2 plasma treatment, which increase the surface activity and further improve the interfacial adhesive strength between CFRP and adhesive. Compared with the above two gases, O2 plasma etch the CFRP surface more vigorously, as well as reorganize the surface chemical groups, forming a more polar —COOH functional group, so that the specimen adhesive strength is improved most effectively, and the specimen failure mode changes from interface failure to substrate failure. In addition, under the excessively high density and energy of the active particles, the adhesive performance will be reduced to some extent with the expansion of the pores by plasma etching.
Effects of fiber addition on the mechanical and thermal properties of jute fiber reinforced resin composites
HE Liping, LIU Longzhen, SU Shengpei, XIA Fan, HOU Shujuan
2023, 40(4): 2038-2048. doi: 10.13801/j.cnki.fhclxb.20220802.001
In order to develop green bast fiber reinforced resin composites with low carbon, energy saving and excellent mechanical and thermal properties and widen their applications, a new kind of modified jute fiber reinforced polypropylene composites (modified JF/PP) with fiber content in range of 10wt%-25wt% was fabricated by a hybrid technique of mill mixing and injection molding process, in which the jute fiber was modified with amino silicone oil invented by our research group in the present work. The effects of modified bast fiber content on the mechanical properties, crystallization behavior, heat resistance (heat deflection temperature) and thermal dimensional stability (linear expansion coefficient) of JF/PP composites were systematically and comprehensively studied. The compatibility and interfacial bonding strength in between the modified and non-modified fiber and PP matrix were analyzed by contact angle test and SEM images. The results indicate that the tensile and flexural strength of JF/PP composites increase with the increase of modified jute fiber content, while the impact strength decreases because the interfacial adhesion between jute fiber and polypropylene matrix is enhanced by modifying jute fiber with amino silicone oil. It is also found from the analyses of DSC, heat deflection temperature and linear expansion coefficient that the addition of modified JF can promote the heterogeneous nucleation of PP and hindered the mobility of PP molecular chain, which lead to the enhancement of the heat resistance property of modified JF/PP composites. The higher the fiber content, the higher heat resistance property of the modified JF/PP will be. When the content of modified JF is 25wt%, the heat deflection temperature of the modified JF/PP is 142.5 ℃, which is 53.5% higher than that of pure PP. Meanwhile, the linear expansion coefficient (CLE) of the modified JF/PP composites decrease significantly with the increase of fiber addition, which suggests that the fiber addition can significantly improve the thermal dimensional stability of the modified JF/PP composites. The linear expansion coefficients of pure PP and the modified JF/PP composites present anisotropic feature. Compared with pure PP, when the fiber addition is 25wt%, the linear expansion coefficientsof the composites decrease by 73.2% in the parallel flow direction and 14.4% in the vertical flow direction. The better mechanical and thermal properties of the modified JF/PP composites will achieve when the fiber addition is in range of 15wt%-20wt%.
Bamboo structure like carbon fiber reinforced porous polyethersulfone matrix composites
XU Peijun, HAN Lei, WANG Linjiang, GUO Xinliang, LIU Ronghai, GAO Shanglin
2023, 40(4): 2049-2055. doi: 10.13801/j.cnki.fhclxb.20220525.002
Bamboo is a natural composite material, which is composed of bamboo fiber as reinforcement and lignin as matrix. The bamboo fiber structure endows bamboo with the characteristics of high strength, and the porous lignin structure endows bamboo with the characteristics of light and high toughness. In this paper, carbon fiber reinforced bamboo structure porous polyethersulfone matrix composites (CF/foam PES) were prepared by imitating the structural characteristics of bamboo, and porous polyethersulfone was deposited on the surface of carbon fiber by liquid immersion method and immersion precipitation phase transformation method. The results show that: compared with traditional carbon fiber reinforced dense polyethersulfone matrix composites (CF/condense PES), CF/foam PES prepared in this paper has low apparent density; the specific strength and specific modulus of CF/foam PES are 234.5% and 192.6% higher than those of CF/condense PES. Moreover, the porous polyethersulfone matrix enhances the energy absorption properties of CF/foam PES.
Preparation and properties of bacterial cellulose/phenolic resin composite transparent film
CONG Wenzhong, MU Jiahui, CAO Mengyao, CHEN Sheng, XU Feng
2023, 40(4): 2056-2065. doi: 10.13801/j.cnki.fhclxb.20220526.002
In recent years, the plastics pollution is becoming more and more serious due to the overuse of fossil-derived transparent films. It is significant to prepare the composite transparent film with excellent comprehensive properties based on green environment-friendly materials. Cellulose is an ideal raw material for the preparation of flexible composite transparent materials because of its advantages of environmental friendliness, renewability and sustainability. In this study, bacterial cellulose (BC) was immersed in phenolic resin (PF) solution, and BC/PF composite transparent film was prepared by hot pressing technology. The effects of phenolic resin concentration and hot-pressing temperature on the microstructure, optical properties, thermal stability, mechanical properties and wettability of BC/PF composite transparent film were investigated. The results show that the BC/PF composite film has a more compact structure and smooth surface when compared with BC film, and its transmittance as high as 88%. The mechanical strength, thermal stability, and waterproof performance of the BC/PF composite film are also significantly improved. The dry strength and wet strength of BC/PF composite film are 2.2 times and 3.4 times higher than that of BC film. This study has scientific guiding significance for alleviating pollution of plastic transparent film and exploring the rapid preparation of green transparent film.
Effect of the surface enrichment of coupling agent on the interfacial properties and interlaminar fracture toughness of GFRPs
GUO Miaocai, LI Yafeng, ZHANG Dujuan, HONG Xuhui
2023, 40(4): 2066-2074. doi: 10.13801/j.cnki.fhclxb.20220526.001
Sizing agents are the key component to form the composite interface. Understanding the influence of sizing agents on the interfacial and mechanical properties of composites has important scientific value for the development of high-performance composites. The surface structures, interfacial properties and interlaminar fracture toughness of two high strength glass fiber fabric reinforced epoxy resin composites (GFRPs) with two different sizing agents were studied. The results show that one of the sizing agent has significant surface enrichment of the silane coupling agent, resulting in the increase in dynamic contact angle and the decrease in interfacial shear strength between fiber and resin. Contrarily, another sizing agent has less surface enrichment of silane coupling agent. The corresponding fiber has smaller dynamic contact angle and higher interfacial shear strength with the epoxy resin. The mode I and mode II fracture of the composites with these two sizing agents are based on the same mechanism, i.e., the interfacial debonding between resin and fiber. The interfacial continuity is reduced for the composite with the sizing agent existing higher surface enrichment of silane coupling agent. While for the composite with the sizing agent with less silane coupling agent surface enrichment, a continuous interface formed between the interphase and resin, resulting in good interfacial adhesion. The mode I and mode II interlaminar fracture toughness increased by 56.5% and 62.2% compared with these of the former composite, respectively.
MOF in-situ growth modified poly(p-chloromethyl styrene)-polyvinylidene fluoride forward osmosis composite membrane and its anti-fouling performance for emulsified oil wastewater
CHEN Fen, DU Chunhui, HU Jintai, WU Chunjin
2023, 40(4): 2075-2084. doi: 10.13801/j.cnki.fhclxb.20220606.002
Metal-organic framework (MOF) material is expected to improve the water flux and antifouling property of forward osmosis (FO) membrane, and improves its separation performance to emulsified oil wastewater. In order to introduce MOF into FO membrane, poly(p-chloromethyl styrene)-polyvinylidene fluoride (PCMS-PVDF) blend substrate was prepared by phase inversion method. The chloromethyl group (—CH2Cl) in the substrate reacted with secondary or tertiary amine in 2-methylimidazole (Hmim), and then reacted with zinc nitrate (Zn(NO3)2). The antifouling FO membrane was prepared by in-situ growth of metal-organic zeolite imidazolium ester skeleton-8 (ZIF-8) and interfacial polymerization. The surface chemical structures and hydrophilic/hydrophobic property of substrate membrane and FO membrane were characterized by SEM, XPS, FTIR, contact angle analyzer and so on. The results show that ZIF-8 grows uniformly on the surface of PCMS-PVDF substrate, and the nanocrystals are cubic crystals with regular shape. Due to the presence of ZIF-8, the substrate surface is hydrophobic, but the new polyamide layer formed by interfacial polymerization makes the membrane surface hydrophilic again. The results show that the water flux of the FO membrane (PCMS-PVDF-FO) without ZIF-8 modification is only 12.4 L·m−2·h−1, but the FO membrane (ZIF-8/PCMS-PVDF-FO) modified with ZIF-8 reach 20.7 L·m−2·h−1 when using 1 mol/L NaCl as the drawing solution in FO mode. The separation experiment of emulsified oil simulated wastewater shows that the recovery ratio of pure water flux of FO membrane (ZIF-8/PCMS-PVDF-FO) is remained 89.9%, the total fouling ratio is 27.5% after running four cycles for pure water-emulsified oil separation. But under the same condition, the flux recovery rate of PCMS-PVDF-FO is only 66.9%, and the total fouling ratio increases to 66.2%. Based on the above, it can be seen that the FO composite membrane modified by in-situ growth of ZIF-8 exhibits excellent performance in emulsified oil wastewater separation.
Influence of interphase dispersion state of nanoparticles on crystal morphology and dielectric properties in montmorillonite elastomer/polypropylene composites
GAO Junguo, YAO Ziheng, LIU Yanli, LIU Hongshuo, WANG Ran, LIU Liwei, GUO Ning, LI Lili
2023, 40(4): 2085-2095. doi: 10.13801/j.cnki.fhclxb.20220606.001
With the increasing demand for cable, environmental protection and energy-saving insulation has become a new development trend, and the research and development of polypropylene (PP) has become the first choice of dielectric researchers. In order to improve dielectric properties of polypropylene-elastomer blends, MMT-POE/PP nano-modified blends were prepared by two-step melting blending method with two different compatibilizers and organically treated montmorillonite (MMT). And then the effects of interphase dispersion states of nanoparticles in different phase zones on dielectric properties of nano-modified blends were investigated. The microstructure, crystalline morphology and crystallization parameters were characterized by SEM, electrostatic force microscopy (EFM), polarizing microscope (PLM) and DSC. The micro-mechanism of phase dispersion on MMT-POE/PP composites was discussed through the breakdown properties test of the blend sample. The experimental results show that when MMT layers tend to disperse in the PP phase, the crystallization size decreases about 5.9 μm, the crystallization speed increases, and the crystallinity increases about 2.1%. And then the dielectric constant and insulation conductivity decrease obviously, and the alternating current (AC) breakdown field strength increases from 82.69 kV/mm to 95.16 kV/mm. The dielectric properties of nano-modified blends can be positively improved by regulating the tendency of nanoparticles to disperse uniformly in the PP phase.
Effect of styrene-maleic anhydride on phase morphology and properties of PLA/PBAT blends
MO Zhixiang, LIU Xiaochao, LIU Yuejun, MAO Xusheng, ZHENG Wei
2023, 40(4): 2096-2106. doi: 10.13801/j.cnki.fhclxb.20220630.001
Poly(butylene adipate-terephthalate) (PBAT) has outstanding ductility, but its strength is low, then, high modulus of polylactic acid (PLA) can solve the defects of PBAT. The styrene-maleic anhydride (SMA) was used as compatibilizer to prepare poly(lactic acid)/poly(butylene adipate-co-butylene terephthalate) (PLA/PBAT) blends. The effect of the content of SMA on the crystallization performance, thermal performance, rheological behavior and tensile properties of the blends were investigated. The results show that the SMA can significantly reduce the particle size of PLA, and the size of the dispersed PLA phase decreases from 1.75 μm to 0.60 μm when the content of SMA is 1.5wt%. The SMA can increase the crystallinity of PBAT, and as the SMA is added up to 2wt%, the crystallinity reaches up to the maximum value of 9.22%. It is found by the Han curves that low content of the SMA can give rise to closely homogeneous blends, and the elasticity of PLA/PBAT melt increase gradually with the increase in amount of SMA content. Moreover, the SMA enhance the tensile properties of PLA/PBAT blends. As the addition of SMA, the tensile strength and elongation at break both increase first and then decrease. The tensile strength of the composite with 1.5wt% SMA is 21.8 MPa, which is 21% higher than that of the counterpart without SMA (18.1 MPa). The elongation at break reaches the maximum value of 433.7% when SMA content is 1wt%, which is 25% higher than that of the composite without SMA.
Functional Composite
Preparation and performance of water and oil-resistant packaging paper based on polysaccharide-vegetable wax-nano-SiO2
ZHU Ruifeng, LONG Zhu, QIN Chengrong, LV Wenzhi, ZHENG Hui, WANG Zhiying
2023, 40(4): 2107-2118. doi: 10.13801/j.cnki.fhclxb.20220622.001
With the development of society, the demand for non-toxic and environmentally friendly food packaging materials has been increasing. At this stage, there are few studies on fluorine-free food packaging paper that take into account both water and oil resistance. In this study, a compound oil-proof agent was prepared by cross-linking chitosan solution and sodium alginate solution with ferulic acid, and coated on the food packaging base paper to prepare oil-resistant paper. Then a compound water-proof agent was prepared by using carnauba wax and silica nanoparticles as raw materials, water and oil-resistant paper was prepared by dipping method, and investigated the effects of different mass ratios and coating amounts on the water and oil resistant effect of paper and paper performance. The results show that when the compound mass ratio of chitosan and sodium alginate solution is 8∶2 and the coating amount is 4 g/m2, the oil-resistant paper can reach the highest oil-proof grade (grade 12). When the compound mass ratio of carnauba wax and silica nanoparticles is 4∶3 and the dipping amount is 3 g/m2, the water absorption of paper surface (Cobb) value of the paper is 5.93 g/m2 and the water contact angle is 158.40°, which significantly improves the water and oil-resistant performance of the base paper. In addition, compared with the base paper, the tensile strength of the water and oil-resistant paper shows a raise of 30% and the air permeability shows a reduction of 60%. In short, the preparation process of this study is simple, the raw materials are fluorine-free and environmentally friendly and the coated paper shows better water and oil resistance, which is expected to be applied in food packaging.
Preparation of flame retardant microcapsules based on microfluidic technology and properties and flame-retardant mechanism of modified epoxy resin
LU Yizhou, GENG Haichun, SHEN Jinrong, FANG Yuan
2023, 40(4): 2119-2130. doi: 10.13801/j.cnki.fhclxb.20220610.001
In order to further improve the flame retardant performance of epoxy resin, FR-PN@ETPTA flame retardant microcapsules with ethoxylated trimethylpropane triacrylate (ETPTA) as the shell and phosphorus-nitrogen flame retardant (FR-PN) as the core material were prepared by microfluidic technology and applied to epoxy resin (EP). The thermal stability, flame retardancy and mechanical properties of FR-PN/EP and FR-PN@ETPTA/EP were compared. The effects of FR-PN@ETPTA flame retardant microcapsules on the combustion performance and thermal degradation behavior of EP were discussed, and the flame-retardant mechanism of FR-PN@ETPTA flame retardant microcapsules was revealed. The results show that the flame retardancy of EP is improved by flame retardant microcapsule. When the amount of flame retardant microcapsule is 10wt%, the limiting oxygen index (LOI) value increased to 37.3%, and the UL-94 reached V-0. The tensile and flexural properties of epoxy resin are reduced by adding FR-PN or flame retardant microcapsules, but the tensile and flexural properties of the specimens with flame retardant microcapsules are better than those with flame retardant. After adding 10wt% flame retardant microcapsules, the impact strength of the resin increases by 39% than that of pure EP. The results show that the flame-retardant mechanism of flame retardant microcapsule modified epoxy resin is the combination of gas phase flame retardant and condensed phase flame retardant.
Preparation and application of multinuclear rare earth ion doped organic complex light conversion agents
ZHOU Mingming, LIU Wei, YANG Chengxiang, ZHAO Xiuxian, YANG Zhen, LU Xiangxiang, JIANG Xuchuan
2023, 40(4): 2131-2139. doi: 10.13801/j.cnki.fhclxb.20220519.001
In order to accelerate the transition to new from old economic engines and build a strong modern agricultural country, light conversion agricultural film has been regarded as one of the important research directions in the field of "optical agriculture". The light conversion agents must have good weather resistance and excellent light conversion characteristics to fabricate the light conversion agricultural film. However, the existing light conversion agents have the problems of single emission spectrum and narrow emission range, which leads to the poor matching between the emission spectrum of light conversion agents and the absorption spectrum of plant photosynthesis, and seriously restricts the development of light conversion agricultural film. In this paper, a kind of organic complex (light conversion agents) doped with a variety of rare earth ions (Sm3+, Eu3+, and Y3+) were synthesized by use salicylic acid and o-phenanthroline as ligands. The results show that the fluorescence spectra of this kind of light conversion agents are significantly broadened by the incorporation of Sm3+. A light conversion agricultural film with the function of converting ultraviolet light to red light was prepared by mixing the synthesized light conversion agent into ethylene-1-hexene copolymer (PO) film by blow molding. The composition and structure of the light conversion agents were determined by FTIR and XPS. At the same time, the thermal stability and optical properties of light conversion agents and light conversion agricultural film were characterized by TGA55 and steady state and transient state fluorescence spectrometer (FLS920). The test results show that the synthesized light conversion agents can absorb ultraviolet light (λ=250-400 nm) and emits red light (λ=610-660 nm). The spectral property is highly matched with the absorption spectrum of plant photosynthesis in the red light region, and the light conversion agricultural film prepared with this kind of light conversion agents still maintains good luminescence performance, which will be conducive to the popularization and application of light conversion agents in the field of agricultural film. This study provides a practical method to broaden the fluorescence emission range of light conversion agents and improve the matching with the absorption spectrum of plant photosynthesis in the red band. The light conversion agents are successfully applied to the preparation of light conversion agricultural film, which achieve the purpose of converting ultraviolet light into red light.
Synthesis and characterization of the barium titanate-potassium sodium niobate relaxor ferroelectric energy storage ceramics
JIN Quan, SONG Enpeng, CAI Ke
2023, 40(4): 2140-2154. doi: 10.13801/j.cnki.fhclxb.20220509.002
The low comprehensive energy storage performance, such as the charging energy density, discharging energy density, and energy storage efficiency, is a key scientific problem to be solved urgently in the energy storage ceramics field. Both improving the polarization difference (∆P) and breakdown field strength (BDS) of the ceramics are the key to enhance their comprehensive energy storage performance. With the main crystal phase BaTiO3 (BT), utilizing the K0.5Na0.5NbO3 (KNN) as the coating agent, sintering aid and additives, the BT-KNN ceramics with the grain sizes of 100 nm and 200 nm was synthesized, respectively. The BT-KNN ceramics has obvious nanodomains, relaxation behaviors and dielectric temperature stability, and with a high ∆P and high BDS. Compared with the BT-KNN ceramics with the grain size of 100 nm, the BT-KNN ceramics with the grain size of 200 nm has a better comprehensive energy storage properties, including high charging energy density W (2.50 J·cm−3), recoverable energy density Wrec (2.08 J·cm−3) and energy storage efficiency η (83.2%). This research may provide a theoretical basis for preparing high comprehensive energy storage performance ceramics.
Porous carbon supported ruthenium single atom and ruthenium nanoclusters catalysts for efficient hydrogen evolution reaction
LI Chuang, WANG Yu, HOU Liqiang, LIU Xi'en
2023, 40(4): 2155-2168. doi: 10.13801/j.cnki.fhclxb.20220512.001
The preparation of electrocatalyst for high efficiency hydrogen evolution reaction (HER) is of great significance to the large-scale promotion of hydrogen energy. In this paper, using sodium carboxymethyl cellulose (CMC-NA) and RuCl3 as raw materials, Ru-CMC-Na hydrogel was prepared by the coordination of Ru ions with CMC-Na in solution. Then, porous carbon supported Ru single atom and Ru nanocluster catalyst RuSA+NC/C-2 was prepared by freeze-drying, high temperature annealing and pickling. The catalyst RuSA+NC/C-2 shows excellent HER activity and stability in both acidic and alkaline electrolytes, reaching 10 mA·cm−2 current density at 20 mV and 23 mV, respectively. After 12 h chronoamperometry test, the activity of RuSA+NC/C-2 shows no obvious attenuation. The mass activity of RuSA+NC/C-2 is 5.8 times that of commercial Pt/C when the overpotential is 0.05 V in 1 mol/L KOH electrolyte. The physical characterization of RuSA+NC/C-2 catalyst shows that the porous structure and large specific surface area of RuSA+NC/C-2 catalyst can expose more active sites. Ru single atom and Ru nanocluster structure improve the utilization rate of Ru atom. XPS analysis shows that there is a strong interaction between Ru and carbon support, resulting in the formation of electron-deficient Ru, thus improving HER activity of the catalyst.
Effect of in-situ assembling zeolite imidazolate frameworks on the photoelectric properties of paper-based ZnO nanorod array
YU Haihan, TAN Xiaoran, SUN Shubo, ZHANG Lina, ZHU Peihua, YU Jinghua, GAO Chaomin
2023, 40(4): 2169-2175. doi: 10.13801/j.cnki.fhclxb.20220518.001
The design and preparation of photoelectrode materials with excellent performance are crucial for the development and application of photoelectrochemical (PEC) technique. Paper-based photosensitive materials have been widely studied due to their large surface area, environmental friendliness and low cost. Among them, as one photoelectric material with high photoelectric activity, high electron mobility and non-toxic, paper-based ZnO nanorods have broad application prospects. However, the high recombination rate of charge carriers and photocorrosion seriously restrict the improvement of its PEC performance. Aiming to address these issues, zeolitic imidazolate frameworks-8 (ZIF-8) is in-situ assembled on paper-based ZnO through hydrothermal method to construct paper-based one-dimensional ZnO/ZIF-8 nanorod array. The results show that the ZIF-8 are uniformly and densely grown on the surface of ZnO nanorods, their seamless interface contact can facilitate the charge transport. Meantime, the ZnO surface enriched with abundant oxygen vacancy is etched and converted into ZIF-8, which can restrain the photocorrosion. Besides, due to the matched energy band structure, the formed ZnO/ZIF-8 heterojunction can realize the bidirectional transfer of photogenerated electrons and holes, thereby efficiently promoting the charge separation. Compared with pure ZnO, paper-based ZnO/ZIF-8 composites exhibit higher photocurrent density and enhanced photostability.
Ag nanoparticles modified (K0.5Na0.5)NbO3/PVDF flexible energy harvester and its performance
ZHAO Zifan, XIONG Juan, DAN Zhigang
2023, 40(4): 2176-2186. doi: 10.13801/j.cnki.fhclxb.20220525.003
The piezoelectric energy harvester which can convert mechanical energy into electrical energy provides a continuous and independent power supply scheme for portable wearable electronic devices, and promotes the development of flexible electronic technology in the direction of intelligence, integration and multi-function. In this paper, Ag nanoparticles decorated potassium sodium niobate (KNN) particles were synthesized by the method of photoreduction, which were compounded with polyvinylidene fluoride (PVDF) to obtain Ag-KNN/PVDF piezoelectric composite films. Then, the flexible composite piezoelectric films with sandwich structure (PAKP) and piezoelectric flexible energy collectors were prepared by thermal pressing Ag-KNN/PVDF film with upper and lower layers of PVDF. The results show that when the amount of Ag nanoparticle is 1% mole fraction, the piezoelectric output performance of PAKP flexible composite film is the best, the output voltage can reach 6.39 V, which is 1.43 times that of the sample without Ag decoration, and the maximum instantaneous power of the device is 150.5 nW. After 3000 cycle tests, the voltage output amplitude of the device has no obvious decline. The 220 nF capacitor can be charged to 1.2 V in 200 s by fixing it on the bicycle frame and collecting the mechanical energy of the bicycle, which shows that it has a good application prospect in the field of self-power supply of low-power electronic devices.
Study on the properties of flame-retardant epoxy resin HPCTP-DOPS/EP with double groups synergistic flame retardant effect
XU Zhiyan, HOU Zeming, YE Xiaolin, QI Yuzhao, XU Songjiang, BAO Dongmei, ZHANG Daohai, ZHOU Guoyong, CAI Xiaodong, ZOU Guanglong, WEN Zhu
2023, 40(4): 2187-2198. doi: 10.13801/j.cnki.fhclxb.20220607.006
The flame retardant effect of single phosphaphenanthrene and phosphazenes was limited. In order to improve the flame retardant effect of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (DOPS) on epoxy resin (EP), DOPS and hexa (phenoxy) cyclotriphosphazene (HPCTP) were compounded and applied in EP. When the total P content was 1.2wt%, DOPS and HPCTP were added to EP by adjusting the ratio of P content in the phosphaphenanthrene and phosphazene groups to prepare EP composites. The limiting oxygen index test (LOI), vertical flame test (UL-94), thermogravimetric analysis (TGA), cone calorimeter test (CONE), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and thermogravimetric-infrared spectroscopy analysis (TG-IR) were used to study the effects of different proportions of phosphaphenanthrene and phosphazene groups on the thermal stability, and combustion performance of EP, and explored the law and mechanism of double groups synergistic flame retardancy. The results show that there is synergistic flame retardancy between P and S elements. When the total P content is 1.2wt%, the LOI value and UL-94 grade of HPCTP-DOPS/EP increase with the increase of S content in the composite system. and the ratio of P content between HPCTP and DOPS is 0.2∶1, the LOI of HPCTP-DOPS/EP composite system is 30.4%, reaching UL-94 V-0 grade, the total heat release (THR) and peak heat release rate (PHRR) decreased significantly, The EP/HPCTP/DOPS composite has a more dense and stable expanding carbon layer after combustion, which is superior to the flame retardant effect of the two flame retardants on EP solely, there is a synergistic flame retardant effect between the phosphazene and phosphaphenanthrene flame retardants. From the perspective of flame retardant mechanism, DOPS and HPCTP plays a flame retardant role in gas phase and condensed phase respectively.
Preparation and characterization of electrochromic thin films based on fast response f-La2O3/PANI
DAI Yan, XU Zifang, FU Yuhao, ZHANG Xiang
2023, 40(4): 2199-2208. doi: 10.13801/j.cnki.fhclxb.20220623.007
Based on the fact that electrochromic films have important research and development prospects in military camouflage, building energy saving, automobiles and other industrial fields, the surface of La2O3 was modified by silane coupling agent KH-550 and compounded with conductive polymer polyaniline (PANI) to prepare f-La2O3/PANI electrochromic material. Comparative analysis of composite electrode and pure PANI electrode by XRD, FTIR, SEM-EDS, UV-vis, and electrochemical workstation. The effect of f-La2O3 addition on the structure, morphology, electrochemical properties and electrochromic properties of PANI was investigated. The results show that the incorporation of f-La2O3 makes the PANI fibers tend to be smaller, and the composite material has higher crystallinity and molecular chain orientation than pure PANI; f-La2O3 will break the network cross-linking structure of PANI, resulting in a decrease in the electrochemical performance of the composite, but it can accelerate the transition process of PANI protonation and deprotonation, and effectively inhibit the oxidative degradation of PANI during the electrochromic process of the film; When f-La2O3/aniline molar ratio is 1∶3.5, the electrochromic performance of f-La2O3/PANI composite reaches the best, the coloration efficiency (CE) at 570 nm is 22.81 cm2·C−1, and the fading and coloring response time (τb, τc) are 1.29 s and 1.33 s, respectively. After 320 cycles of fading, the electrochemical activity of the thin films remains about 50% of the initial value.
Pinning/sliding behaviors and underlying mechanism of water droplets on ultra-slippery surfaces under temperature and force fields stimuli
GU Jianfeng, HUANG Jiuhui, LI Dayu, LIU Lin, ZHU Suwan, XIAO Yi
2023, 40(4): 2209-2215. doi: 10.13801/j.cnki.fhclxb.20220701.001
In recent years, stimuli-responsive slippery liquid-infused porous surfaces (SLIPSs) have attracted widespread attention in the field of microfluidic manipulation. However, most reported responsive SLIPSs function under a single stimulus, which are challenging to satisfy the generalized application scenarios. Here, a kind of dual-responsive slippery surface (DRSS) is fabricated through femtosecond laser cross-scanning method. Relying on the synergic action of temperature and force field, the sliding/pinning behaviors of water droplets on DRSS can be dynamically controlled. The impact of diverse parameters on the critical sliding volume of droplets is systematically investigated, including lubricant infusion amount, groove depth and spacing. The dynamic mechanism of droplet sliding/pinning behaviors is revealed. This kind of DRSS could be used in the related fields such as lab-on-a-chip and microfluidic reactors.
Process optimization of high-performance soft magnetic composite based on phosphate and bismaleimide coated iron powders
YU Hongya, GUAN Shaocong, LI Jingzhou, LIU Zhongwu, GUO Baochun, CHEN Rongyin
2023, 40(4): 2216-2223. doi: 10.13801/j.cnki.fhclxb.20220520.001
Electronic devices are developing towards miniaturization, integration, and high frequency with the development of electronic industry. The soft magnetic cores require better loss characteristics and higher reliability becaues their magnetic properties would decline due to the sharply increased magnetic loss and serious heating with the high-frequency application. In this work, high-performance soft magnetic composites with phosphate-bismaleimide@Fe structure were prepared by phosphating treatment and bismaleimide (BMI) coating, and the effects of insulation coating methods on the reliability of soft magnetic composites were investigated. The results indicate that the excellent comprehensive magnetic properties of soft magnetic composites have been obtained as the content of BMI resin is 2wt% and the compaction pressure is 800 MPa, the effective permeability is 32.2, the total loss is 1181 kW/m3 under the condition of 50 mT@200 kHz and the quality factor Q can reach 46.2 at 1 MHz. Moreover, it is found that the resin layer between iron powder particles can play a role of stress buffer to reduce the formation of internal stress and the total loss of soft magnetic composites. The aging of soft magnetic composites due to the oxidation of the magnetic powders which was proved by flourier infrared spectrum analysis. The phosphating treatment and BMI coating can effectively slow down the aging to improve the high-temperature reliability of soft magnetic composites and perform stable magnetic properties after long-term accelerated aging test at 180℃.
Civil Construction Composite
Experimental study on bond behavior of GFRP bar and seawater coral aggregate concrete after exposure to high temperatures
ZHOU Chunheng, WANG Junyi, WANG Xintang, CHEN Zongping
2023, 40(4): 2224-2239. doi: 10.13801/j.cnki.fhclxb.20220623.001
To study the residual bond performance of glass fiber reinforced polymer (GFRP) bars and seawater coral aggregate concrete after exposure to high temperature, the pull-out tests were performed through 54 GFRP bars coral aggregate concrete specimens and steel bars coral aggregate concrete specimens. The highest temperature of 350℃ and concrete classes of C20 to C30 were considered in this experiment. The surface changes and bond failure modes of specimens after high temperatures were observed. The bond stress-slippage curves, bond strength, stiffness and peak slippage were obtained. The influences of temperatures, bar diameters and concrete strengths on the bond properties of GFRP bars and coral aggregate concrete after high temperatures were analyzed. Furthermore, the deterioration mechanism of GRFP bars seawater coral aggregate concrete after high temperatures was revealed based on the analysis of mass loss rate and XRD tests. Finally, the bond stress-slippage constitutive relation and residual bond strength of GFRP bars and coral aggregate concrete after high temperatures were proposed. The results show that even though the failure modes of specimens after high temperature are similar to those at room temperature, the interface of GFRP bar and coral aggregate concrete is degraded significantly due to the carbonization of GFRP bar and pyrolysis of coral aggregate concrete. The bond strength of specimens decreases and the peak slippage increases as the temperature increasing. The smaller the diameter of GFRP bars, the lower the residual bond strength and stiffness of specimens after high temperatures. The higher the strength classes of coral aggregate concrete, the greater the residual bond stiffness and the smaller the peak slippage. The calculated results of the proposed bond stress-slippage constitutive model and residual bond strength of GFRP bars-coral aggregate concrete after high temperatures show a good agreement with the experimental results.
Crack propagation law and failure precursor of steel fiber reinforced concrete based on acoustic emission and microseism monitoring
LIU Chengyu, CHEN Chenghai, ZHANG Xiangxiang, CAO Yangbing, HE Xiyang
2023, 40(4): 2240-2250. doi: 10.13801/j.cnki.fhclxb.20220725.001
Uniaxial compression tests were performed on the steel fiber reinforced concrete (SFRC) specimens with different ages and steel fiber volume fractions. The acoustic emission (AE) and microseismic (MS) signals were monitored during the loading progress. Through the in-depth analysis of testing results, the feature of AE and MS signals and the evolution of crack propagation in SFRC were studied. The results show that: (1) The crack propagation of SFRC during uniaxial compression can be divided into four stages: Crack compaction stage (I), crack stable development stage (II), crack unstable propagation stage (III) and post-peak failure stage (IV). Different stages show different AE and MS characteristics. (2) With the increase of age, the energy rates and count rates of AE and MS in stages I and II decrease, as well as the generation rates of micro-, meso- and macro- cracks of the whole specimen. However, the energy rate and count rate of AE and MS in stages III and IV increase, as well as the generation rates of micro-, meso- and macro-cracks of the whole specimen increase. (3) With the increase of steel fiber volume fraction, the AE energy rate, AE count rate and micro-crack generation rate of the whole specimen in stages II, III and IVincrease, while the MS energy rate and MS count rate in each stage decrease, and the MS energy surge time rate in each stage increase. Furthermore, the generation rates of meso- and macro- cracks of the whole specimen in each stage decrease, and the failure time is delayed. (4) Before the failure of SFRC, the energy rates and count rates of AE and MS increase sharply, as well as MS energy ratio. These variables can be used as the precursor index of SFRC failure.
Self-healing and frost resistance of ultra-high performance concrete
KAN Lili, QIAO Hongzhuo, WANG Fei, LIU Neng, WANG Jingbo
2023, 40(4): 2251-2260. doi: 10.13801/j.cnki.fhclxb.20220617.002
In order to study the self-healing and frost resistance performance of cracked ultra-high performance concrete (UHPC) in service, UHPC specimens with hybrid steel fibers were pre-loaded to the tensile strain level of 0.05% and 0.1%, respectively, cured in water for 28 days and then used for performing 300 freezing and thawing cycles experiment. The indexes including uniaxial tensile property, characteristics of crack, mass and ultrasonic pulse velocity (UPV) were utilized to comprehensively evaluate the self-healing and frost resistance performance. Meanwhile scanning electronic microscope and energy disperse spectroscopy (SEM-EDS) were adopted to analyze microstructure and self-healing products. The results show that: after 28 days water-curing, the specimen with pre-loaded strain of 0.05% exhibits better self-healing, in which the tensile strength, tensile strain and strain energy are higher than those of the reference specimen, and all surface cracks close; The parameters of tensile properties of the specimens with pre-loaded strain of 0.1% are lower compared to the reference specimen, with a partially healed maximum crack (the width of 69 μm). After 300 freezing and thawing cycles, the initial cracking strength and tensile strength of two types of pre-damaged specimens further increase, while both the tensile strain and strain energy show the decrease trend. The variation of relative mass and UPV can well reflect the secondary-hydration effect of two specimens. The results of SEM-EDS demonstrate that, the fiber-matrix bonding near crack is stronger; The healing products are mainly Ca(OH)2 and CaCO3 on the surface of crack, and calcium silicate hydrated (C-S-H) gel in the inner side of crack.
Mechanical properties and crack width control of seawater coral sand ECC
WANG Zhenbo, HAO Rusheng, LI Pengfei, HAN Yudong, SUN Peng
2023, 40(4): 2261-2272. doi: 10.13801/j.cnki.fhclxb.20220607.002
In order to address the brittleness and durability issues of coral aggregate concrete, seawater coral sand engineered cementitious composites (SCECC) was prepared by using the regional raw materials located in islands and reefs. The effects of different aggregate types, maximum grain size and fineness modulus on the compressive, tensile properties and crack control ability of ECC were experimentally investigated. The results show that with the decrease of the fineness modulus of coral sand, the compressive strength of SCECC first increases and then decreases, which maximizes (63.3 MPa) at SCECC with the maximum grain size of 2.36 mm. Reducing the maximum grain size of coral sand results in improved tensile performance to varying extents. SCECC with a maximum grain size of 0.60 mm exhibits the best tensile properties, and its initial cracking strength, tensile strength and ultimate tensile strain are 2.29 MPa, 4.11 MPa and 5.15%, respectively. Meanwhile, its average crack width approaching strain capacity is controlled at 81 μm. Compared with tap water-quartz sand ECC, SCECC possesses higher compressive strength and more rapid development of early strength (its 7 days compressive strength can arrive at 73%-78% of 28 days compressive strength). The failure modes of aggregate and polyvinyl alcohol (PVA) fiber in these two ECCs are different, resulting in slightly lower tensile strength, elastic modulus and crack control ability at peak strain, but significantly enhanced tensile ductility of SCECC.
Experimental investigations on the influence of nozzle travel speed and height on the mechanical properties of 3D printed concrete
SHI Qingxuan, WAN Shengmu, WANG Qiuwei, TAO Yi, HUO Jian
2023, 40(4): 2273-2284. doi: 10.13801/j.cnki.fhclxb.20220607.001
In order to study the influence of printed parameters such as nozzle travel speed and nozzle height on the mechanical properties of 3D printed concrete (3D PC), the same mix proportion of cast test blocks and printed test blocks with different printed parameters were prepared. Through concrete cubic compressive test, prismatic axial compressive test and cubic splitting tensile test, the failure process and failure mode were investigated, the influence of nozzle travel speed and nozzle height on the mechanical properties of 3D PC were analyzed, the axial compression stress-strain curve of 3D PC was obtained, and the relationships between the strengths of 3D PC were established. The results show that the cubic compressive strength, axial compressive strength and splitting tensile strength of 3D PC decrease with the acceleration of nozzle travel speed and the increase of nozzle height, and the adverse effect of nozzle height on strengths is stronger than that of nozzle travel speed. Under the optimal combination of printed parameters, the compressive strength of printed test block is higher than that of cast test block. However, due to the weak interlayer bonding surface of printed test block, the splitting section is at the interlayer interface, resulting in an obvious smooth section, and the splitting tensile strength is lower than that of cast test block. Through regression analysis, the functional relationships between the strengths of 3D PC and printed parameters, as well as the conversion relationships between axial compressive strength, splitting tensile strength and cubic compressive strength were established.
Strength characteristics of biopolymer modified sand under dry-wet cycle
SONG Zezhuo, HAO Shefeng, MEI Hong, LIU Jin, REN Jinghua, BU Fan, WANG Zi
2023, 40(4): 2285-2295. doi: 10.13801/j.cnki.fhclxb.20220623.006
The strength characteristics of biopolymer (XG)/sand composites were studied by unconfined compres-sive strength test and triaxial shear test. The effects of different XG contents (mass ratio to sand) and different dry-wet cycles on the strength characteristics of XG/sand were analyzed. The microstructure of different XG/sand was analyzed and studied by scanning electron microscope and low field NMR analyzer. The results show that with the increase of biopolymer content, the unconfined compressive strength, peak deviator stress and cohesion of XG/sand increase, and the internal friction angle varies in the range of 27°-32°. With the increase of the number of dry-wet cycles, the unconfined compressive strength, peak partial stress and cohesion of XG/sand decrease. The strength of XG/sand decreases about 29% after 4 dry-wet cycles. With the continuous increase of the number of dry-wet cycles, the decrease of strength is stable at about 20%. Biopolymers can form a large number of network structures on the surface and pores of sand. A large number of network structures are connected to each other as a network membrane, connecting the sand as a whole. The change of water in the environment will cause some damage to the reticular membrane, which reduces the mechanical properties of XG/sand. However, XG/sand still has strong structural and mechanical properties compared with the unmodified sand.
Dispersion behavior of ultra-low dosage graphene oxide and its effect on structures and performances of cement-based materials
WU Lei, LV Shenghua, LI Zexiong, LI Yao, LIU Leipeng
2023, 40(4): 2296-2307. doi: 10.13801/j.cnki.fhclxb.20220623.004
The existence state and dispersion behavior of graphene oxide (GO) nanosheets in aqueous phase and dispersant were studied. It is found that the main reason for the large dosage, high cost and unstable and insignificant application effect of GO when it is applied to cement-based materials is that GO nanosheets are easy to agglomerate and cannot be evenly dispersed in the cement matrix. Amphoteric polycarboxylate dispersant (APC) and its composite with GO (APC-GO) were prepared. The result finds that GO no longer exists in the cluster state in APC-GO composite , and is mainly adsorbed on APC multi-chain molecules and presents a multi-chain dispersion state. The mechanical properties and durability of cement-based materials can be significantly improved by the addition of APC-GO composite with ultra-low content (mass ratio to cement) of GO of 0.0003%. SEM results show that cement-based materials have regular and compact microstructure morphology. The results show that GO can be uniformly dispersed in cement matrix and has regular regulation effect on the morphology and structure of cement hydration products. The research results have guiding significance for the application of GO.
Influence mechanism of curing temperature on the characteristics of dredged ultrafine mortar from Yangtze River
CHEN Xudong, WU Chaoguo, CHEN Zhang, NING Yingjie, BAI Lihui
2023, 40(4): 2308-2320. doi: 10.13801/j.cnki.fhclxb.20220607.005
In order to realize the comprehensive utilization of dredged sand in the lower Yangtze River and expand the source of fine aggregate, the effects of different maintenance temperatures on different dredged sand admixtures mortar characteristics were investigated. Using dredged sand as raw material, three mortar mix ratios with different dredged sand admixtures were designed, and the effects of four curing temperatures of 40, 60, 80 and 90℃ on the compressive and flexural strengths at different ages were investigated, The microstructures of specimens with different curing temperatures and different dredged sand admixtures were analyzed by combining X-ray diffraction, thermogravimetric-differential scanning calorimetry, scanning electron microscopy and mercury injection test. The results show that with the increase of curing temperature, the distribution of hydration products in mortar is uneven, which hinder the subsequent hydration reaction. The compressive and flexural strengths of mortar increase first and then decrease. The higher the curing temperature is, the greater the steam curing damage is. The particle size of dredged sand is very small, and it has good filling effect. Appropriate incorporation of dredged sand can improve the compactness of the system, and reduce the number of harmful holes and multiple harmful holes, thereby improving the mechanical properties of mortar. Under the condition of steam curing, the pore structure defects of mortar increase, and the optimization effect of dredged sand is amplified, which can offset some adverse effects of steam curing to a certain extent. The enhancement rate of the dredged sand on the compressive strength gradually decreases with the increase of the curing temperature, and the maximum could enhance 31.35%. The enhancement of the flexural strength increases first and then decreases, and the maximum could enhance 14.29%.
Nonlinear regression models of compressive performance and pore structure of rubber aggregate alkaline mortar
SHI Yuhang, MA Qinyong, XU Zifang, MA Dongdong, HUANG Kun
2023, 40(4): 2321-2330. doi: 10.13801/j.cnki.fhclxb.20220519.002
The disposal of used tires causes many environmental problems, and the crushed rubber powder can replace fine aggregate in building mortar. The content and particle size of rubber aggregate in mortar are the main factors affecting the strength of rubber concrete. Alkali-activated slag can replace ordinary Portland cement and improve the environmental friendliness of mortar. The influence of multi-factor coupling on the compressive properties of rubber aggregate mortar was studied. By testing the compressive strength of mortar, significance analysis of the test results was completed and the multivariate nonlinear regression model was established. The microscopic pore measurement and SEM test of mortar samples were carried out to explore the degradation mechanism of rubber aggregate on the compressive strength of mortar. The results show that the increase of rubber aggregate content in mortar will cause the decrease of compressive strength of mortar. Compared with the control group, the average compressive strength of alkali activated mortar decreases by 49.93% and the silicate mortar decreases by 66.62% under 40vol% aggregate replacement rate. Under the high alkaline environment of alkali-activated mortar, the average compressive strength of mortar using 0.38 mm rubber aggregate is 69.65% of the control group, which is the optimal value in the test group. In the low alkaline environment of silicate mortar, with the decrease of rubber aggregate size, the average compressive strength of mortar decreased from 61.46% of the control group to 37.98%.
Multi-scale degradation mechanism of aeolian sand concrete under salt-frost condition
LI Yugen, ZHANG Huimei, CHEN Shaojie, HU Dawei, GAO Wei
2023, 40(4): 2331-2342. doi: 10.13801/j.cnki.fhclxb.20220607.004
It is of great guiding significance to study the salt-frost degradation and reveal the degradation mechanism of aeolian sand concrete for its popularization and application. The salt-frost degradation rule of aeolian sand concrete was studied based on the fast indoor test and mechanical properties test, and its degradation mechanism was revealed from multi-scale combining with the SEM, XRD, NMR and damage mechanics theory. The results show that aeolian sand affects the frost resistance of concrete, and the optimal frost resistance is achieved with 100% aeolian sand replacement despite its low strength. The loss rates of mass and compressive strength increase with the increase number of salt-frost cycling, while the relative dynamic elastic modulus decreases with the increase number of salt-frost cycling. The salt-frost damage of aeolian sand concrete is dominated by physical-chemical effects, and the bone-slurry debonding in the interfacial transition zone (ITZ) and the cracking of the nearby mortar matrix are the main reasons for the degradation of its macroscopic physical and mechanical properties. Aeolian sand can change the pore structure of concrete and the moisture transmission path in it, thereby affects the pore saturation and the salt-frost resistance of concrete.
Flexural toughness and damping property of recycled PET plastic aggregate mortar
BAO Cong, ZHAO Xiaoqin, FAN Wei, LIANG Chaofeng, ZHAN Haihua
2023, 40(4): 2343-2354. doi: 10.13801/j.cnki.fhclxb.20220623.002
In order to study the flexural toughness and damping characteristics of recycled polyethylene terephthalate (PET) plastic aggregate mortar (RPAM), the recycled PET plastic aggregate (RPA) was prepared from the wasted PET plastics. Taking RPA substitution rate as the variable, the three-point bending loading test and the suspension beam bending free vibration test on RPAM were carried out. The load-deflection curve, flexural toughness, first-order damping ratio and frequency of RPAM with different RPA substitution rates were analyzed. Besides, the damping mechanism of RPA interface was analyzed based on the SEM test. The results show that with the increase of RPA substitution rate, the ductility of RPAM increases, the slopes of loading branch and unloading branch of load-deflection curve gradually decrease, and the initial crack strength and flexural strength decrease. The addition of RPA makes the failure of RPAM more ductile, which increases the initial crack deflection and peak deflection significantly. The toughness indexes I5, I10 and I20 are 4.17, 5.65 and 5.89 times larger than that of ordinary mortar, respectively. The residual strength of RPAM increases gradually as the RPA substitution rate increasing. With the increase of RPA substitution rate, the first-order frequency of RPAM decreases by 9.0%-25.9%, while the damping ratio increases by 11.3%-58.1%. The micro structure of interface transition zone (ITZ) between RPA and cement matrix is loose. The slippage and friction of the ITZ and the viscosity of RPA increase the damping energy consumption of RPAM, and the recommended dosage of RPA is in the range of 15.5vol%-17.2vol%.
Composite Micro-mechanics
A simulation method of forming wrinkle defects in thermoplastic woven fabric prepregs in a wide temperature range based on non-orthogonal constitutive model
LV Bingyi, WANG Shiyu, XIAO Jinyou, WEN Lihua, HOU Xiao
2023, 40(4): 2355-2364. doi: 10.13801/j.cnki.fhclxb.20220812.001
The forming quality of thermoplastic composite preforms directly affects the manufacturing quality of structure. Due to the high melting temperature and viscosity of thermoplastic matrix, unreasonable design of forming process temperature will lead to forming defects such as wrinkles, which brings challenges to high-quality forming of thermoplastic composite structures. Currently, the existing researches on thermoforming of thermoplastic prepregs are mainly based on the continuous, the discrete and the semi-discrete approaches, the anisotropic large deformation behavior of thermoplastic prepreg is analyzed by establishing a multi-mechanism coupled constitutive model, which is not fully considered the influence of process control on wrinkle defects during forming macroscopic deformation. In this paper, a simulation method of forming wrinkle defects in thermoplastic prepregs in a wide temperature range was developed. By characterizing the mechanical properties of thermoplastic woven fabric prepregs at different temperatures and loads, the non-orthogonal constitutive model parameters of thermoplastic prepregs in a wide temperature range were obtained. The effect of temperature on forming wrinkle defects in thermoplastic prepregs was proposed, and the deformation mechanism of wrinkle defects in a wide temperature range in the forming process was revealed, and the optimal control scheme of forming temperature was obtained. The research results show that the initiation and evolution of wrinkle defects has been affected by the in-plane shear and compressive deformation behaviors at different temperatures, the deformation degree of wrinkle defects of prepreg has been decreased with the increase of temperature. The simulation results of the non-orthogonal constitutive model are basically closer to the experimental results.
Impact resistance of horn-inspired tubular composite structure
XU Jing, LI Yan, FU Kunkun
2023, 40(4): 2365-2376. doi: 10.13801/j.cnki.fhclxb.20220530.006
Horns exhibit excellent impact resistance due to their unique tubular microstructure. This study draws inspiration from the microstructure of horns and designs a tubular structure. Based on 3D printing fused deposition technology, a horn-inspired tubular structure (HTS) was fabricated using chopped carbon fiber reinforced nylon composites. The impact test results show that there is a long high-load platform region in the impact force-displacement curve of HTS, which absorbs a large amount of impact energy at this stage. Compared with the un-biomimetic structure sample, the energy absorption of HTS sample increases by 143.9%, and the specific energy absorption value increases by 178.8%. The HTS impact finite element model was proposed, and the simulation prediction results are in good agreement with the experimental results of the impact response and crack propagation path, which verifies the validity of the model. Based on the analysis of the model, it is found that a large stress concentration is generated around the tube during the impact process, which deflects the crack and captures the crack, and re-initiates new cracks in other positions of the tube and expands toward the next tube. This process is repeated to absorb a large amount of impact energy. Finally, the influences of geometric parameters and material properties on impact energy absorption of HTS were explored based on the finite element model. This study explored the impact energy absorption characteristics and energy absorption mechanism of the horn-inspired tubular composite structure, which was of great significance for the design and manufacture of new impact-resistant equipment.
Experimental verification and numerical simulation of buckling behavior of variable stiffness composite plates and open-hole plates
ZHANG Yahui, CHEN Puhui, KONG Bin
2023, 40(4): 2377-2389. doi: 10.13801/j.cnki.fhclxb.20220513.001
To verify the application potential of the variable stiffness design based on tow curve laying in improving the buckling behavior of typical aerospace structures, variable stiffness composite plates and open-hole plates were designed and manufactured. Through the strain gauge and the non-contact 3D optical measurement system, the out-of-plane displacement and load direction strain of the specimens under uniaxial compressive load were comprehensively measured. The experimental results show that the buckling loads of the variable stiffness plates and open-hole plates are increased by 53.4% and 46.6%, respectively, compared with the same configuration of the linear lay-up specimens; The mechanical responses of the specimens are similar, the stiffness is greatly reduced after linear loading to the buckling load, and the post-buckling stage of the variable stiffness specimens is approximately linear, while the linear lay-up specimens vary continuously. The numerical model was refined according to the experimental scheme, and the calculated results of buckling load, out-of-plane displacement and strain are basically consistent with the experimental results. On this basis, the stiffness distribution and load distribution of load section in the numerical models were extracted, and the anti-buckling mechanism of the variable stiffness design was clarified. For the specimens in this paper, the variable stiffness design can also significantly increase the failure load, reduce the side load and relieve the stress concentration.
Axial compression behavior of novel concrete-filled circular CFRP-UHPC composite tubular columns
LIU Lei, HE Zhen, WANG Peng, CAI Xinhua, HAN Diyang, LUO Tao
2023, 40(4): 2390-2404. doi: 10.13801/j.cnki.fhclxb.20220623.003
In order to study the feasibility of replacing steel tubes of concrete filled carbon fiber-reinforced polymer (CFRP)-steel tube columns with ultra high performance concrete (UHPC) tubes, a novel concrete-filled CFRP-UHPC tube (CFFUT) column was proposed. The CFFUT column consists of a combination of UHPC precast tubes externally wrapped with CFRP and an internal cast-in-place filled normal concrete. Ten CFFUT columns, including two contrast columns, were tested under monotonic axial compression, and the influences of UHPC tube thickness, CFRP layer numbers and filled concrete strength were investigated. The results show that CFRP-UHPC tube can effectively improve the bearing capacity, deformation capacity and ductility of composite columns. The failure of CFFUT column is mainly manifested as the collapse of filled concrete, cracking of UHPC tube and rupture of CFRP. The integrity of CFFUT column is good after failure, and it belongs to ductility failure mode. The ultimate bearing capacity of CFFUT column is positively correlated with the thickness of UHPC tube, the number of CFRP layers and the strength of filled concrete. Ductility factor increases with the increase of UHPC tube thickness and CFRP layer number, and increases first and then decreases with the increase of filled concrete strength. The interface strengthening mechanism of CFFUT column is revealed. The ultimate bearing capacity of CFFUT columns is 93.9%-203.5% higher than that of normal concrete columns with the same section, and the ultimate bearing capacity of CFFUT columns is equivalent to that of concrete-filled CFRP- steel tube columns to a certain extent. The theoretical calculation model of ultimate bearing capacity is established and verified by finite element analysis. The calculated and simulated values are in good agreement with the test results.
Effect of thickness of carbon fiber susceptor on mechanical property and fracture mode of carbon fiber reinforced thermoplastic composite induction welded joint
WANG Feiyun, LUO Jiebang, ZHANG Pingze, LIU Xing, ZHAN Xiaohong
2023, 40(4): 2405-2414. doi: 10.13801/j.cnki.fhclxb.20220618.001
The carbon fiber susceptors with different thicknesses of 0.2 mm, 0.3 mm and 0.5 mm were prepared based on carbon fabric and resin film by the hot moulding process, and the temperature simulation and process experiment of induction welding for carbon fiber reinforced thermoplastic composite (CFRTP) were carried out. The fusion morphologies of welded joints with carbon fiber susceptors of different thicknesses were observed. To investigate the effect of thickness of carbon fiber susceptor on the mechanical property and fracture mode of CFRTP induction welded joint, the fracture morphologies and fracture modes of welded joints with different susceptors thicknesses were analyzed after the tensile-shear test. The results show that carbon fiber susceptor enables high quality induction welding of CFRTP without introducing heterogeneous materials, but a significant inhomogeneity in temperature distribution exists at the joining interface. As the thickness of the susceptor, not only the effective joining area at the interface is reduced but also the forming effect, joining quality and mechanical property of welded joint deteriorate due to the excessive melted resin. The maximum tensile-shear strength of the welded joint is 23.77 MPa when the thickness of the susceptor is 0.2 mm. The fracture modes of welded joints include cohesive failure of the susceptor, self failure of base material, mixed failure and interface failure, which change according to the thickness of added susceptor.
Numerical simulation of microwave curing of resin matrix composites workpiece
LONG Xikun, LI Shujian, CHEN Rong, CAO Zheng, LI Changping, CHANG Tengfei
2023, 40(4): 2415-2426. doi: 10.13801/j.cnki.fhclxb.20220419.009
Taking T800 carbon fiber/X850 epoxy composites T-shaped workpiece as the combined object, using COMSOL Multiphysics simulation software, the finite element simulation model reflecting the microwave curing of single feed resonant cavity of composites workpiece was established, and the distribution laws of electromagnetic field, temperature field and curing degree field inside the microwave cavity and workpiece and their mapping relationship with microwave input power were studied. The results show that there are opposite electric field intensity distributions in the microwave cavity and the workpiece. In the composite workpiece, the electric field intensity in the area far away from the microwave feed port is higher than that near the feed port, and there is a strong tip effect in the angular area of the workpiece; With the increase of microwave input power, the electric field intensity in the microwave cavity and the workpiece increases. The maximum electric field intensity appears on the upper and lower surfaces, and the temperature of the lower surface is significantly higher than that of the upper surface; Increasing the microwave input power will lead to the rapid temperature rise of the workpiece, and then induce the gradient of temperature and curing degree. In the middle and late stage of heating up, the gradient of temperature and curing degree is obvious. This study recommends that the microwave input power should be controlled within 500 W.
Interface mechanical bonding properties between coarse synthetic polypropylene fiber and cement mortar
LI Changhui, CHEN Xuefang, ZHANG Xianmin, WANG Huiying
2023, 40(4): 2427-2440. doi: 10.13801/j.cnki.fhclxb.20220624.001
The interfacial bonding mechanical properties of fiber-embedded cement-based materials play an important role in the mechanical properties of fiber-reinforced concrete materials. The pull-out test of single fiber can better simulate the stress conditions between the fiber and the cement matrix material interface. Therefore, a pull-out test of a single coarse polypropylene fiber from cement mortar matrix was carried out which considered three fiber diameters (0.2 mm, 0.6 mm, 0.8 mm), three fiber embedding lengths (10 mm, 20 mm, 30 mm), three fiber surface properties (indentation type, wave type, smooth type) and three kinds of cement mortar matrix water-binder ratio (0.66, 0.51, 0.41) influencing factors. The morphological characteristics of the fibers after being pulled out were observed by SEM, a numerical model of the fiber pull-out process was established by ABAQUS finite element to study the shear stress between a single fiber and the cement-based interface. At the same time, the experimental results and the simulation results were numerically fitted, and the influence rules of various factors on the interface bonding mechanical properties were obtained: (1) The optimum water-binder ratio of cement mortar is 0.41-0.49; (2) The embedded length of the synthetic crude polypropylene fiber is 8-10 mm, and the optimal fiber diameter is in the range of 0.26-0.39 mm; (3) When the fiber surface properties are indentation type, the utilization rate of fibers in cement-based materials is large, and the interface bonding performance with cement mortar is good.
Implosion response and anti-explosion performance of fabric bags
XIE Jiang, GAO Binyuan, JIANG Yilun, PAN Hanyuan, FENG Zhenyu
2023, 40(4): 2441-2450. doi: 10.13801/j.cnki.fhclxb.20220630.003
Aramid and ultra-high molecular weight polyethylene (UHMWPE) fiber fabric bags were designed for the disposal of improvised explosive device (IED). The implosion test was carried out, and a finite element (FE) model of fabric bag implosion was established. The anti-explosion abilities of the two fabric bags were compared from the perspectives of external overpressure and critical thickness, and the effects of the initial implosion distance and the thickness of the fabric bag on the anti-explosion ability were analyzed. The results show that the main failure modes of the fabric bag under implosion load are broken hole in the center area and the failure of the sealing zipper. The critical thickness of the fabric bag increases approximately linearly with the charge in the range of 20-100 g TNT charge. The critical thickness of the aramid fabric bag is significantly larger than that of the UHMWPE fabric bag when the charges are the same. The UHMWPE fabric bag has a better anti-explosion ability without considering the influence of the explosion fireball. When the thicknesses are the same, the overpressure outside the aramid fabric bag is smaller, indicating that the overpressure attenuation ability of the aramid fabric bag is better. As the initial implosion distance of the fabric bag increases, the critical thickness decreases. There is an overpressure higher than the human body which can withstand within a certain range outside the fabric bag. Taking the 30 g TNT, 3 mm aramid fabric bag condition as an example, the overpressure at 665 mm from the center of the fabric bag is 34.2 kPa, exceeding the eardrum damage threshold.