2022 Vol. 39, No. 1

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Review
Research progress of flexible nanocomposites for piezoresistive strain sensors
HU Hailong, MA Yalun, ZHANG Fan, YUE Jianling, LUO Shibin
2022, 39(1): 1-22. doi: 10.13801/j.cnki.fhclxb.20210729.004
Abstract:
Flexible nanocomposite piezoresistive strain sensors are becoming more and more attractive owing to their unprecedent merits in sensing performance and stretchability, which can be feasibly employed in the fields of wearable electronics and structural health monitoring.Inthiswork, three aspects including structural design, preparation methods and application prospects are briefly reviewed, where recent progress of composite piezoresistive strain sensors is mainly discussed by centering on materials chosen and structure configuration towards the sensing improvement. Crucial parameters in affecting the sensing performance as well as sensing mechanism have been initially analyzed in composite piezoresistive strain sensors. Subsequently, detailed discussion and analysis were performed on the recent advances of composite strain sensors by focusing on the main guideline of materials optimization-structural design/processing-performance improvement and practical applications. Recent achievements of finite element analysis (FEA) and artificial intelligence algorithm are also introduced to conduct the controlling and mechanism analysis of conductive network design (formation, overlapping and evolution) and multi-scale layered structural configuration in composite strain sensors, where both conductive network and structural configuration are playing a significant role in changing the sensing performance. Consequently, a multi-modality sensor with distinct sensing signal, high stability and low hysteresis is urgently needed to fulfill the demands of flexible nanocomposites for piezoresistive strain sensors, where main points towards future developments and future directions in composites strains sensors are also highlighted.
Research progress on application of superhydrophobic materials in anti-icing and de-icing technology
LI Jun, JIAO Weicheng, WANG Yinchun, YIN Yuxin, CHU Zhenming, HE Xiaodong
2022, 39(1): 23-38. doi: 10.13801/j.cnki.fhclxb.20210819.007
Abstract:
Icing and frosting bring many disadvantages to people's life. Ice accumulation will affect the flight safety of aircraft, delay the rocket launch mission, deform transmission lines and power networks, cause transportation obstacles, and even produce major economic problems and personal safety problems. Conventional anti-icing and de-icing methods are often costly, inefficient, or environmentally harmful. Superhydrophobic technology, which uses the intrinsic properties of materials to delay icing and significantly reduces the ice adhesion between ice and substrate, is a promising anti-icing and deicing technology. In this paper, firstly, the wetting phenomenon of solid surface and ice nucleation mechanism are introduced. It should be indicated that superhydrophobic surfaces face many problems such as the its wettability can be changed with decreasing the temperature and increasing the relative humidity, poor stability and mechanical robustness, and lack of facile and large-scale fabrication methods. Secondly, the research progress of superhydrophobic anti-icing and de-icing materials, stable and mechanically robust superhydrophobic surfaces, fabrication of superhydrophobic surfaces and multifunctional anti-icing and de-icing superhydrophobic materials are reviewed and analyzed. Finally, many applications of anti-icing and de-icing superhydrophobic materials in practical engineering are concluded and summarized. On this basis, the development trends and prospects of anti-icing and de-icing superhydrophobic materials are discussed.
Research progress of nanocellulose-based luminescent materials
ZHONG Weiting, WANG Zhixin, WANG Kun, PENG Xiaopeng, JIANG Jianxin
2022, 39(1): 39-47. doi: 10.13801/j.cnki.fhclxb.20210617.001
Abstract:
Nanocellulose-based lumnescent materials are normally obtained by physical and chemical modification of nanocellulose. Due to their unique photophysical or photochemical properties, and the characteristics of biodegradation, biocompatibility and environmental friendliness, nanocellulose-based luminescent materials further extend the universal applications of functionalized cellulose. This article introduces the luminescent principle of luminescent materials, summarizes the preparation methods and related applications of nanocellulose fluorescent materials, and summarizes the challenges and development trend of nanocellulose luminescent materials. According to the different preparation procedures, nanocellulose-based luminescent materials could be divided into three categories: composite luminescent materials of nanocellulose/carbon quantum dots, cellulose luminescent carbon quantum dots and composite luminescent materials of nanocellulose/fluorescent dye. Due to the unique optical and structural characteristics, nanocellulose luminescent materials have been extensively used as membrane, paper, hydrogel, aerogel, etc., and have great prospects in applications on ion detection, biological imaging, and photoelectric applications.
Research progress of carbon dots based white light emitting fluorescent films
CHEN Tong, LIU Xinghua, ZHENG Jingxia, YANG Yongzhen, LIU Xuguang
2022, 39(1): 48-63. doi: 10.13801/j.cnki.fhclxb.20210607.003
Abstract:
Carbon dots (CDs) have many excellent characteristics, including simple preparation, abundant sources, low toxicity and excellent optical properties, that can be served as fluorescent materials to prepare fluorescent films for solid-state lighting devices. The different ways of the CDs-based film formation and their white light emission make the variety properties of fluorescent films. Firstly, the photoluminescence mechanisms of CDs are introduced. Secondly, the fluorescent films are divided into two categories based on the film formations: CDs/polymer fluorescent films and CDs self-assembled fluorescent films, and their preparation methods are summarized. Thirdly, according to the types of fluorescent materials in the fluorescent film, two means of realizing white light emission of fluorescent films are introduced by mixing polychromatic fluorescent materials and using single white light CDs. Finally, the problems of CDs and their fluorescent films and the prospects for development of CDs-based fluorescent films are discussed.
Current status of carbon fiber reinforced polymer composites recycling and re-manufacturing
HU Qiaole, DUAN Yufang, LIU Zhi, ZHENG Xianhong, XU Zhenzhen
2022, 39(1): 64-76. doi: 10.13801/j.cnki.fhclxb.20210615.003
Abstract:
The rapid application and development of high-performance carbon fiber reinforced polymer composites (CFRPs) brought challenges for the recovery of composite waste. Recycling of carbon fiber reinforced thermoset composites has been particularly demanding. This paper reviewed the research status of CFRPs waste recycling from multiple perspectives in order to effectively promote their sustainability. Characteristics of various recycling technologies, application fields and new strategies for recycling CFRPs with biodegradable resin were reviewed. Finally, the future development trend of CFRPS recycling technology was prospected.
Research progress of shape memory polymer fibers and reinforced composites
LI Wenbing, WEI Wanting, LI Jinrong, LIU Junhao, QIAN Kun
2022, 39(1): 77-96. doi: 10.13801/j.cnki.fhclxb.20210729.005
Abstract:
Shape memory polymer fibers and reinforced composites are novel smart materials developed from shape memory polymers. They have advantages of light weight, low price, excellent deformation capability, reversible modulus, various driving methods and simple structures. Furthermore, they have some characteristics, like high elastic modulus, large recovery stress, etc., that can effectively amend the shortcomings of traditional shape memory polymers. This article first outlines the driving methods of shape memory polymer fibers and fiber reinforced shape memory polymers, and summarizes the spinning methods of shape memory polymer fibers. Then the potential applications of shape memory polymer fibers and fiber reinforced shape memory polymers in various fields are analyzed. Finally, the current problems are discussed and the future research is prospected.
Basic scientific problems of Ni rich cathode materials for Li-ion battery: Surface residual Li and its removal
WANG Xin, CHEN Xin, REN Li, WANG Shuo, LUO Hongji, ZHANG Jun, LV Genpin, XIANG Wei
2022, 39(1): 97-110. doi: 10.13801/j.cnki.fhclxb.20210608.001
Abstract:
The layered Ni-rich cathode materials are considered as the most promising cathode materials for Li-ion batteries due to their high reversible capacity, low self-discharge performance and low cost. However, they have some disadvantages, such as the unstable material structure, capacity decay and poor safety, hindered their practical application. The Ni-rich cathode materials with nickel content over 80% are easy to react with moisture and CO2 in the air, generating residual Li compounds such as Li2CO3, LiHCO3 and LiOH on the surface of materials. The presence of residual Li not only leads to structure instability and electrochemical performance degradation, but also causes battery safety problems. In this paper, the mechanism of the formation of residual Li and its hazards are reviewed. Then, the effect of factors (e.g. washing temperature, time, drying temperature, etc.) during water washing on the material property are discussed, and the mechanisms of structural deterioration and capacity degradation induced by water washing are elaborated. Lastly, other methods for removing residual Li compounds are introduced, especially the non-washing surface coating method, which shows great application potential in removing the influence of residual Li compounds.
Recent advances in uranium adsorption by biomass based composite
ZHANG Yunxiu, CAO Minghui, ZHENG Shaodi, JIANG Yuanping
2022, 39(1): 111-125. doi: 10.13801/j.cnki.fhclxb.20210625.002
Abstract:
With the development of nuclear energy, a large amount of uranium-containing radioactive wastewater has been produced, posing a great threat to ecological safety and human health. At the same time, with the gradual depletion of terrestrial uranium, it is imperative to exploit uranium from seawater to ensure long-term sufficient supply of nuclear fuel. In recent years, the adsorption method has attracted increasing attention in the treatment of uranium-contaminated wastewater and the extraction of uranium from seawater. And it is a green, economical and sustainable development strategy for uranium adsorption to prepare high value-added biomass-based materials with excellent performance based on its eco-friendliness, abundant reserves and low cost. This review focuses on the main progress of biomass-based uranium adsorption composite materials, covering its adsorption performance and adsorption mechanism. Finally, the future prospects and research direction are proposed for better biomass-based adsorbents.
Resin and Polymer Composite
Microstructure and properties of functionalized Al2O3@SiO2/phenolic epoxy-bismaleimide composites
CHEN Yufei, ZHAO Hui, DONG Lei
2022, 39(1): 126-133. doi: 10.13801/j.cnki.fhclxb.20210316.002
Abstract:
The Al2O3 and SiO2 were obtained by sol-gel method and the KH560-Al2O3@SiO2 were prepared with KH560 as the coupling agent. The KH560-Al2O3@SiO2/MBMI-EPN composites were prepared by in-situ polymerization, using bismaleimide resin and phenolic epoxy resin (MBMI-EPN) as matrix, KH560-Al2O3@SiO2 as the reinforcement and 4’4-diaminodiphenylmethane (DDM) as curing agent. The micro-structure of KH560-Al2O3@SiO2 were characterized and the effect of the reinforcement on properties of composites were studied. The results show that the Al2O3@SiO2 particles have clear core-shell structure. The short-fiber Al2O3 is inner core, and the amorphous SiO2 is outer shell, which are connected by chemical bonds. The KH560 is successfully grafted onto the surface of Al2O3@SiO2, and the particles packing phenomenon is weakened. The micro-structure of the composites shows that KH560-Al2O3@SiO2 forms a multi-phase structure in the MBMI-EPN matrix with good dispersion and stable interface. The cross-sectional shape is fish scale, and there are no Al2O3@SiO2 nanoparticle agglomerates and the overall structure is regular. When the content of KH560-Al2O3@SiO2 is 1.5wt%, bending strength and impact strength of the composites are 126 MPa and 14.7 kJ/m2, which are 21.2% and 27.8% higher than resin matrix, respectively. And the thermal decomposition temperature of the composites is 392.3℃, which is 14.5℃ higher than that of resin matrix.
Experimental study on picosecond laser cutting AFRP composites
YANG Jian, ZHANG Rui, ZHAO Yu, DU Tingting, YE Yunxia
2022, 39(1): 147-157. doi: 10.13801/j.cnki.fhclxb.20210426.002
Abstract:
A three wavelength picosecond pulsed solid-state laser with ultraviolet picosecond laser ( λ=355 nm), green picosecond laser ( λ=532 nm) and infrared picosecond laser ( λ=1064 nm) was used to cut 1 mm thick aramid fiber reinforced polymer (AFRP) by a single pass scanning. The slit width, thickness and thickness were measured by optical microscope (OM) and scanning electron microscope (SEM). The effects of laser wavelength, laser power and scanning speed on the notch shape and quality were analyzed. The results show that: compared with the infrared laser and green laser cutting AFRP, the cutting efficiency of ultraviolet laser is higher, and the cutting quality is better; the width of upper slit, slit depth and the width of upper surface heat affected zone increase with the increase of laser power, and decrease with the increase of laser scanning speed; the slit taper decreases with the increase of laser power, and increases with the increase of laser scanning speed. When the laser scanning speed is reduced properly, the ratio of slit depth to width is improved.
Electromagnetic absorption properties and mechanical properties of Fe-Ni alloy/polylactic acid composites fabricated by fused deposition modeling
WU Haihua, HU Zhenglang, LI Yutian, QIAN Peng, LIU Li, ZHOU Jianxin
2022, 39(1): 158-168. doi: 10.13801/j.cnki.fhclxb.20210311.003
Abstract:
The Fe-Ni alloy/polylactic acid (FeNi50/PLA) composite was prepared using fused deposition modeling (FDM) by PLA/FeNi50 composite filaments with different contents of FeNi50. Effects of FeNi50 on the micromorphology, magnetic properties, electromagnetic properties and mechanical properties of the composites were investigated using SEM, vibrating sample magnetometer, vector network analyzer and universal testing machine, and the reflection loss of composites were discussed. The results show that the saturation magnetisation strength and electromagnetic properties of the composites gradually increase as the FeNi50 content, resulting in improved reflection loss and a shift towards to low-frequency. The two-step mixing process enables FeNi50 particles to be distributed relatively uniformly in the PLA matrix, forming an island-like structure, which prevents FeNi50 agglomeration and isolates eddy currents, thus improving microwave absorption performance. Thanks to the above dispersion structure, the spherical particles are distributed in the crack extension direction, which absorbs the fracture energy and increases the elongation at break of the composites by 31.7% compared with the pure PLA. It is shown that the FDM-based FeNi50/PLA composites have good potential for microwave absorption and load-bearing applications.
Preparation and properties of polyethylene-based blended films base on mesoporous nano-SiO2 antioxidant active assembly
TANG Youkai, QIU Xiaolin, GONG Xuefeng, TANG Yali
2022, 39(1): 169-181. doi: 10.13801/j.cnki.fhclxb.20210330.003
Abstract:
The mesoporous nano-SiO2 carrier was prepared with cetyltrimethylammonium bromide (CTAB) that served as template. Then α-tocopherol (α-TCP) was integrated into the carrier to form antioxidant active assembly. Low-density polyethylene (LDPE) active films were prepared by flat extrusion. Linear low-density polyethylene (LLDPE) and polyolefin thermoplastic elastomer (POE) were used as modified resin to regulate the films for better performance. The assembly and α-TCP were introduced into the films, serving as antioxidant active factor. The structure of the nano-SiO2 carrier was studied by TEM, XRD and nitrogen adsorption/desorption apparatus. The thermal stability of the assembly was investigated by thermal gravimetric analysis (TGA). The physical and controlled release properties of the films were determined by mechanical performance test, release performance test, etc. Meanwhile, the additives’ synergistic effects on the films were studied. The results show that the active films’ thermal processing, mechanical and controlled release properties are significantly improved with introduction of the additives. The assembly’s insulating effect leads to thermal resistant temperature of α-TCP, which is integrated into assembly, increase by 70% when compared with the bared α-TCP. As compared with pure LDPE film, the mechanical properties of the active films are significantly improved by the additives. The tensile strength increase rate of the film modified by POE and assembly is more than 2.5 times as other samples’. As compared with the films modified with the bared α-TCP, the assembly reduces the diffusion coefficient of α-TCP by 45%-47%, which shows the remarkable controlled release property of the active films. The films’ crystallinity is negatively correlated with release rate of the antioxidant substance. As a result, the prepared materials can be used to regulate active substances’ release rate of antioxidant active package. And it shows a good potential for strengthing and toughing package films.
Construction of hierarchical structure of carbon nanotube-encapsulated ammonium polyphosphate/Mg(OH)2 and the synergistic effect on the fire safety of ethylene-vinyl acetate copolymer
LI Zhuoshi, LU Jingyi, DONG Chun, WANG Bibo, JIN Zhijian, FANG Quansheng, HU Yuan
2022, 39(1): 182-192. doi: 10.13801/j.cnki.fhclxb.20210312.006
Abstract:
In this paper, a hierarchical structure of carbon nanotube-encapsulated ammonium polyphosphate (APP@CNT) flame retardant was synthesized, and Mg(OH)2 was used in conjunction with nano-composite technology to prepare fire-safe wire and cable flame-retardant ethylene-vinyl acetate copolymer (EVA) composite material (APP@CNT/EVA-Mg(OH)2). The structure and performance of flame-retardant ethylene-vinyl acetate composite materials were studied by using SEM, TGA, limiting oxygen index (LOI), vertical combustion (UL-94), microscale combustion colorimeter (MCC), universal stretching machine and high resistance meter. The results show that the residual carbon rate of EVA increases from 2.4% to 43.9%, the peak heat release decreases by 57.85% compared with pure EVA, the total heat release decreases by 57.80%, and the yield strength increases by 408%. At the same time, the volume resistivity of APP@CNT/EVA-Mg(OH)2 is still as high as 3.9×1015 Ω·cm, indicating that the EVA composite material after flame retardant treatment is still an ideal wire and cable material. In addition, the oxygen index of APP@CNT/EVA-Mg(OH)2 has reached 38%, and the vertical combustion UL-94 has also reached the V-0 level, which further illustrates the hierarchical structure of APP@CNT and magnesium hydroxide. Flame-retardant ethylene-vinyl acetate composite material has high fire safety performance.
Resin polymer
Synergistic improvement of electrical conductivity and interlaminar toughness of carbon fiber resin matrix composites based on intercalation method
XIANG Dong, LIU Jialiang, ZHAO Chunxia, LI Hui, WANG Bing, LI Yuntao
2022, 39(1): 137-149. doi: 10.13801/j.cnki.fhclxb.20210407.001
Abstract:
Carbon fiber reinforced resin matrix composites (CFRP) are widely used in aerospace and is gradually replacing metal materials for aircraft structures as a result of their low density and high strength characteristics, while poor electrical conductivity and interlaminar shear fracture toughness could reduce their safety as structural components in use. In order to improve the poor electrical conductivity and interlaminar fracture toughness of CFRP, multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) doped polyethersulfone (PES) conductive thermoplastic films (CTFs) were prepared by solution casting in this work. Then CTFs were interleaved into carbon fiber/epoxy resin (CF/EP) prepregs to prepare composite laminates. The electrical conductivity and interlaminar fracture toughness of the composite laminates were investigated. The results show that compared with the control sample (CS), the conductivity of the laminate increases by 474% and 554% in the transverse (Y) and thickness (Z) directions, respectively. The Mode I and Mode II interlaminar fracture toughness values were evaluated by double cantilever beam (DCB) and end-notched flexure (ENF) testing. The data show that when the nano-filler mass ratio of CNT∶GNP is 2∶1 in the interleaved CTF, the Mode I interlaminar fracture toughness and fracture impedance of the composite laminates are increased by 441% and 165%, respectively. Moreover, when the nano-filler mass ratio of CNT∶GNP is 8: 1, the Mode II interlaminar fracture toughness of the composite laminates is increased by 79%. In addition, the microstructural morphology of the composite material was observed by SEM and its failure mechanism was studied.
Functional Composite
Polyaniline growing on polylactic acid substrate towards flexible and biodegradable supercapacitors
WEI Huige, LI Guixing, WAN Tong, CHEN Anli, PENG Zifang, ZHANG Huan
2022, 39(1): 193-202. doi: 10.13801/j.cnki.fhclxb.20210517.001
Abstract:
With the rapid development of global economy, the depletion of fossil fuels, and the severe environmental pollution, new electrochemical energy storage technologies are in urgent need. In recent years, supercapacitors have attracted extensive attention due to their advantages of high power density, long cycle life, wide working temperature window, and excellent cycling stability. Unfortunately, traditional supercapacitor devices are big and heavy, complicated to manufacture, and most of the time undegradable, and therefore cannot achieve sustainable development goals of the society. In this content, it is imperative to develop an innovative type of flexible and environmental friendly supercapacitor. Polyaniline-polylactic acid (PANI-PLA) biodegradable flexible supercapacitor electrode was prepared by in situ chemical polymerization method utilizing polylactic acid (PLA) film as the substrate. SEM, FTIR, and UV-Vis were performed to characterize the morphology and chemical structure of the electrode. The electrochemical tests show that under the three-electrode system, the areal specific capacitance of PANI-PLA can reach 5.00 mF·cm −2 (@0.10 mA·cm −2). Under the two-electrode system employing polyvinyl alcohol/sulfuric acid (PVA/H 2SO 4) as the gel electrolyte, the symmetric PANI-PLA//PANI-PLA solid supercapacitor delivers an areal capacitance of 0.20 mF·cm −2, a power density of 3.60 μW·cm −2, and a corresponding energy density of 0.02 μW·h·cm −2 (@0.004 mA·cm −2). The asymmetric solid supercapacitor consisting of polyaniline grown on stainless steel (PANI-SS) and PANI-PLA delivers an areal capacitance of 23.33 mF·cm −2, a power density of 30.09 μW·cm −2, and a corresponding energy density of 1.17 μW·h·cm −2 (@0.05 mA·cm −2).
Design of BiMn-doped Pd modified GO/MOF-74-Co composites for electrocatalytic oxidation of ethylene glycol
MO Han, WAN Zhengrui, ZHONG Yuting, WU Zhirui, HU Yalan, LIU Hongying, ZHOU Liqun
2022, 39(1): 203-212. doi: 10.13801/j.cnki.fhclxb.20210330.004
Abstract:
BiMn co-doped Pd alloy nanoparticles were successfully modified on the 3D pyramidal columnar-like reduced graphene oxide (rGO)/metal-organic frameworks (MOFs)-74-Co to obtain a new composite electrocatalyst PdBiMn@rGO/MOF-74-Co in which the mean particle diameter of Pd-Bi-Mn particles was about 7.8 nm, and MOF-74-Co was a porous face-centered hexagonal unit cell. PdBiMn@rGO/MOF-74-Co catalyst exhibites the highest catalytic activity and durability towards ethylene glycol (EG) electrooxidation under alkaline condition. The excellent electrocatalytic performance is mainly attributed to the strong synergistic effects of Pd, Bi and Mn nanoalloys and abundant reaction active sites in the catalyst, which are beneficial to adsorb more oxygen-containing substances and significantly enhance the resistance to toxicity and stability of the ternary catalyst. Furthermore, the unique microstructure of rGO/MOF-74-Co can provide superior electron transfer properties and multi-porous for the PdBiMn@rGO/MOF-74-Co electrocatalyst. Besides, the mechanism of electrocatalytic oxidation of EG drew up a detailed analysis. The novel composites’ design and outstanding performance would provide an essential reference for the application and development of direct alcohol fuel cells (DAFCs).
Preparation and catalytic performance of nickel-phosphorus-titanium silicalite zeolite composite
ZHANG Pingping, NIE Pengfei, WANG Guixue, WANG Zhaobo, ZHANG Baoquan
2022, 39(1): 213-221. doi: 10.13801/j.cnki.fhclxb.20210320.002
Abstract:
Nickel-phosphorus-titanium silicalite zeolite (Ni-P-HTS-1/NF-T) composite was prepared by electroless composite plating and in-situ treatment process with hierarchical titanium silicalite (HTS-1) zeolite as composite phase and nickel foam (NF) as matrix materials, and its electrocatalytic oxygen evolution reaction (OER) performance was studied. The results show that Ni-P-HTS-1/NF-T composite has faster OER kinetics and electron transfer rate, excellent OER performance and long-term stability in 1.0 mol/L KOH electrolyte. The doping of HTS-1 zeolite and in-situ treatment process reduce the electron transfer resistance of Ni-P-HTS-1/NF-T composite, increase its electrocatalytic active surface area, and change the chemical composition of the composite to form nickel phosphide and hydroxide which can provide catalytic active centers for electrocatalytic oxygen evolution reaction, thus effectively improving the OER performance of Ni-P-HTS-1/NF-T composite.
Preparation of ammoniated tobacco leave powder residue biochar and its adsorption behavior on Cr(VI)
YANG Jinhui, HU Shiqin, YANG Bin, XIE Shuibo, LEI Zengjiang, LI Cong
2022, 39(1): 222-231. doi: 10.13801/j.cnki.fhclxb.20210320.001
Abstract:
Using the waste cigarette leave powder residue as raw materials, after carbonization, the amino functional group was introduced to prepare the ammoniated tobacco leave powder residue biochar (NH 2/TPB), and the effects of pH, dosage, temperature and adsorption time on NH 2/TPB adsorption of Cr(Ⅵ) were studied. The mechanism was analyzed by scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and other techniques. The results show that when the initial concentration is 210 mg/L, pH=4, dosage is 0.8 g/L, temperature is 45℃, and adsorption time is 120 min, the maximum adsorption capacity of NH 2/TPB for Cr(Ⅵ) is 103.627 mg/g. The adsorption process conforms the quasi-second-order kinetic model and Langmuir adsorption isotherm model. The adsorption and removal mechanism of Cr(Ⅵ) mainly include electrostatic interaction, reduction reaction, coordination and complexation with —NH 2, —OH, —COOH, and “π-π” interaction with Si—O—Si. Through five times about adsorption-desorption tests, the Cr(Ⅵ) removal rate is more than 82.88%. This research presents that the ammoniated tobacco leave powder residue biochar has the potential to treat and repair acidic Cr(Ⅵ)-containing wastewater pollution.
Preparation of TiO2/MIL-100(Fe)/nylon composite and its decolorization for organic dye
WANG Jing, LOU Yaya, WANG Chunmei
2022, 39(1): 232-241. doi: 10.13801/j.cnki.fhclxb.20210507.002
Abstract:
TiO2/MIL-100(Fe)/PA composites were prepared by means of in-situ growth method loading TiO2 and MIL-100(Fe) on nylon (PA) at room temperature. FTIR, SEM, EDS, XRD and TG characterization methods were used to prove that TiO2/MIL-100(Fe) was successfully loaded on PA. The effects of light, H2O2, dye structure, sodium chloride and pH value on the decolorization of TiO2/MIL-100(Fe)/PA composite were discussed. The results show that the composite material has adsorption and decolorization effect for Reactive Black KN-B dye under dark condition. The decolorization rate of the composites for different reactive dyes is different under simulated solar light after adding H2O2. The decolorization rate for Reactive Black KN-B is the highest, followed by Reactive Brilliant Red M-3BE and Reactive Brilliant Blue KN-R. The decolorization rate can be reduced by adding NaCl in the dye solution, but the effect is not significant. The decolorization rate is decreased with the increase of pH value of dye solution.
Action mechanism of expanded graphite in the composite of expanded graphite/MnO2 supercapacitor electrode materials
GUI Yang, ZENG Jingyu, FAN Baoan, ZHANG Chuntao
2022, 39(1): 242-249. doi: 10.13801/j.cnki.fhclxb.20210313.001
Abstract:
The pure MnO2 and the composite of expanded graphite (EG)/MnO2 were prepared by a very facile method. The experimental results show that the composite presents higher specific capacitance and more stable rate capacity. The action mechanism of EG in the composite was investigated by the measurements of XRD, TG, EIS, BET, etc. It is found that the δ-MnO2 appears in the composite, whose mass percentage is approximately 30% compared with 3.4% of EG in the composite. The δ-MnO2 has a special layered structure compared with the channel structure of α-MnO2, which makes the ions diffuse and transport easier. The charge exchange resistance of the EG/MnO2 composite is significantly lower than that of pure α-MnO2 which may be caused by more tiny particles size of composite because the specific surface area of the composite being 38.7 m2·g−1, with the pure α-MnO2 of21.6 m2·g−1. The larger specific surface area makes the contact between the material particles and the electrolyte solution more sufficient along with lower charge exchange resistance. In all, the action mechanism of EG in the composite can be summed as follow. The δ-MnO2 with the layered structure is induced to grow on the surface of the EG which has the similar layered structure. At the same time, the grows-up of the MnO2 particles is restrained by EG which makes the contact of particles with electrolyte solution more sufficient with the result of the reduce of charge exchange resistance. And, therefore, the specific capacitance is elevated accompanied with more stable rate capacity.
Biological and Nano-composite
Preparation of self-healing oxidized sodium alginate-carboxymethyl chitosan hydrogel for sustained drug release
HOU Bingna, NI Kai, SHEN Huiling, LI Zhengzheng
2022, 39(1): 250-257. doi: 10.13801/j.cnki.fhclxb.20210518.005
Abstract:
The self-healing oxidized sodium alginate-carboxymethyl chitosan hydrogel (OSA-CMCS) was synthesized based on dynamic imine bonds. OSA was synthesized by oxidizing the uronic acid of sodium alginate, and self-healing OSA-CMCS hydrogels with different crosslinking degrees were prepared by Schiff base reaction with carboxymethyl chitosan, analyzed the microscopic morphology, viscoelastic properties, swelling properties, self-healing properties, enzymatic degradation properties and in vitro drug release properties of OSA-CMCS hydrogels. The results show that as the ratio of OSA to CMCS increase, the degree of crosslinking of the hydrogel gradually increase and the swelling ratio gradually decrease. OSA-CMCS hydrogel has the structural characteristics of highly porous and interconnected pores, and the pore size is in the range of 20-100 μm. At room temperature, OSA-CMCS hydrogel can realize self-healing within 6 hours without external stimulation. OSA-CMCS hydrogel is degradable, and as the degree of crosslinking increase, the degradation rate slow down. OSA-CMCS hydrogel has a slow-release effect on the water-soluble drug gemcitabine, and the drug release time can reach 4 days.
Influence of polar interface on the morphology and degradation performance of calcium alginate gel units
LI Yu, SHEN Yongbin, BIAN Pingyan, WANG Jianping.
2022, 39(1): 258-265. doi: 10.13801/j.cnki.fhclxb.20210330.002
Abstract:
The degradation of the bio-scaffold directly affects its structure, function and survival rate of the loaded cells. Sodium alginate as the raw material and calcium chloride as the cross-linking agent were used to prepare calcium alginate hydrogel bio-scaffold; by changing the ratio of iso-propyl alcohol (IPA) to deionized water (DW) in the crosslinking solvent, coaxial reaction flow interfaces with different polarity conditions were obtained, which affected the aggregation morphology of gel units of calcium alginate gel. The regulation ability of interface polarity on the degradation process of calcium alginate gel was investigated. The results show that the polarity index of the solvent changes from 9.0 to 3.9 with the increase of the proportion of IPA in the crosslinking agent; as the polarity of the interface decreases, the microscopic gel unit of the prepared fiber becomes more orderly; the degradation rate of alginate fibers is slowed down by the ordered and dense morphology of gel units; the mass-loss rate of DW-based fiber scaffold on the fifth day is 91.16% while that of IPA-based fiber scaffold is 73.86%; the denser the gel unit, the lower the swelling degree, and the swelling balance has a retarding effect on the degradation process.
Preparation of hexanoyl ethylene glycol chitosan/poloxamer composite hydrogel for drug release
XU Wenjing, ZHAO Linlin, ZHENG Zelin, GAO Liuyi, LI Zhengzheng
2022, 39(1): 266-274. doi: 10.13801/j.cnki.fhclxb.20210302.008
Abstract:
In order to reduce the dependence of the sol-gel transition temperature of the poloxamer hydrogel on the concentration, the poloxamer (P407) was used as the substrate, and hexanoyl ethylene glycol chitosan (HGC) was compounded with poloxamer to prepare HGC/P407 composite hydrogel. FTIR, SEM and tube inversion method were used to investigate the properties of HGC/P407 composite hydrogel in different mass ratios, and the in vitro drug release performance of HGC/P407 composite hydrogel was characterized by UV-vis spectroscopy. The results show that sol-gel transformation can occur in HGC/P407 hydrogel based on 3% poloxam by controlling the addition of HGC, and the sol-gel transition temperature of HGC/P407 hydrogel is between 32℃ and 37℃. HGC/P407 composite hydrogel has high porosity with interconnected pores which size ranging from 10 to 90 µm. The release amount of the anticancer drug gemcitabine of HGC/P407 composite hydrogel is 82%~90.6%, and the sustained release time can reach about 80 h. HGC/P407 composite hydrogel has important application prospects in the field of injectable drug carriers.
Metal and Ceramic Matrix Composite
Effect of compound field on microstructure and properties of SiCp/AZ91D magnesium matrix composites
LI Ziyang, BO Wenjie, ZHANG Qinglin, GENG Guihong, ZHOU Yuezhang, WANG Yue
2022, 39(1): 275-284. doi: 10.13801/j.cnki.fhclxb.20210325.001
Abstract:
SiCp/AZ91D magnesium matrix composites were prepared under four kinds of external field conditions: normal condition, electromagnetic simulated microgravity field condition, pulse current field condition and "electromagnetic simulated microgravity + pulse current" condition. The test results indicate that: In the normal condition, the grain size of the sample is coarse, the β-Mg17Al12 phase shows an irregular grid structure, and Mg2Si exists in the granular primary phase and dendritic eutectic phase. In the electromagnetic simulation microgravity field condition, the β-Mg17Al12 phase transforms into short rods and granules, and Mg2Si is transformed into patterned eutectic phase. In the pulse current field condition, the β-Mg17Al12 phase transforms into regular distribution of rectangular grid, and Mg2Si exists in dendritic eutectic phase with obvious directivity. The "electromagnetic simulated microgravity + pulse current" condition combines the advantages of the first two kinds of external field conditions, the grain size of the sample is obviously refined, the β-Mg17Al12 phase presents granular, short rod and rectangular grid structures and the Mg2Si is transformed into the pattern and dendritic eutectic structure throughout the grain. Compared with the sample under normal condition, the microhardness is improved by 25.1% and the friction property is improved by 31%.
Effect of fused MgAl2O4 on high temperature creep properties of Al2O3-MgAl2O4 refractory
LI Renjun, ZHANG Ling, ZHENG Peiyu
2022, 39(1): 285-291. doi: 10.13801/j.cnki.fhclxb.20210310.003
Abstract:
The Al2O3 bonded MgAl2O4 fire-resistant composites were prepared with tabular alumina and fused magnesia-alumina spinel as raw materials, and phosphoric acid as binder and then sintered at 1680℃. The creep resistance test was conducted at 1500℃ under 0.2 MPa with insulation for 50 h, The specimens after creep resistance test were characterized and analyzed by XRD, SEM and EDS to investigate the effect of adding amount of MgAl2O4 on high temperature creep resistance of Al2O3 bonded MgAl2O4 fire-resistant composites as well as its mechanism. The results show that Al2O3 bonded MgAl2O4 fire-resistant composites has better creep resistance than Al2O3 composite. During the creep test, magnesium-aluminum spinel aggregate will react with alumina matrix to form secondary spinel layer around the spinel particles, which effectively connects the matrix and aggregate and improves the creep resistance of the specimens. During the formation of the secondary spinel layer, due to the higher migration rate of Mg2+ and the higher thickness ratio on both sides of the reaction interface, the Kirkendall effect will be induced, resulting in a large number of vacancies and pores at the interface.
Fabrication of Ti layer on diamond surface with rotary friction extrusion heating method
LI Yi, YU Aibing, HONG Xin, YUAN Jiandong
2022, 39(1): 292-301. doi: 10.13801/j.cnki.fhclxb.20210409.001
Abstract:
In order to realize metallization of the diamond surface, a rotary friction extrusion heating method is proposed to fabricate Ti layer on the surface of artificial single crystal diamond. The micromorphology of the inner surface of Ti layer and the phase composition of the interface between the diamond and Ti layer were analyzed with a scanning electron microscope and an X-ray diffractometer, and element analysis was carried out with an energy disperse spectrometer. The effect of diffusion annealing temperature and holding time on phase composition of the inner surface of Ti layer was studied. The formation mechanism of the diamond/Ti layer interface was analyzed. The research results show that a uniform and dense Ti layer is formed on the diamond surface after rotary friction extrusion. After diffusion annealing at 600°C for 0.5 h, dot-shaped TiC grains were formed on the inner surface of Ti layer, and the chemical combination between diamond and Ti layer was realized. With the increase of diffusion annealing temperature and holding time, the morphology of TiC grains grows from dot-shaped to rod-shaped. The mass fraction of TiC of the interface increases with the increase of diffusion annealing temperature. The formation of Ti layer on the diamond surface with rotary friction extrusion heating method can be divided into five stages: initial stage, primary diffusion stage, secondary diffusion stage, TiC nucleation stage and TiC growth stage.
Civil Construction Composite
Ionic thermoelectric effect and mechanism of cement-based materials
CUI Yiwei, WANG Yaqiong, WEI Ya
2022, 39(1): 302-312. doi: 10.13801/j.cnki.fhclxb.20210311.001
Abstract:
At present, the thermoelectric effect of cement-based materials is mainly enhanced by adding a large amount of functional fillers. However, the high content of the functional filler increases the cost, degrades their mechanical properties and hinders their wide application. It is found in this study that the pure cement paste without any functional fillers shows a significant ionic thermoelectric effect due to the freely moving ions in the pore solution of the cement-based materials. The ionic thermoelectric effect of the cement-based materials was studied by comparing the thermoelectric voltage of pure cement paste before and after drying, and the mechanism of the ionic thermoelectric effect of pure cement paste was further explored through ion leaching and saturated alkali solution experiments. Results show that the pure cement paste before dry shows a significant n-type ionic thermoelectric effect due to the thermal diffusion of OH. The decrease of the concentration of OH in the leaching process leads to the change of ionic thermoelectric voltage from n-type to p-type. After saturated in NaOH solution, the type of cations has a significant effect on the ionic thermoelectric properties even under the condition of high OH concentration. In addition, the Seebeck coefficient of cement paste without any functional filler can reach 1.133 mV·℃−1, and the power factor PF can reach 0.042 μW·m−1·℃−2, which is higher than that of some cement-based composites with 5% functional filler in the literature.
Piezoresistivity of three dimensional graphene-carbon nanotubes/cement paste
LIU Jintao, HUANG Cunwang, YANG Yang, CAI Qianni
2022, 39(1): 313-321. doi: 10.13801/j.cnki.fhclxb.20210331.001
Abstract:
In order to explore the piezoresistivity of three dimensional graphene-carbon nanotubes (G-CNTs)/cement paste, the four-electrode method was used to study the resistivity change of the G-CNTs/cement paste under load. The influence of G-CNTs content, loading amplitude, loading speed and constant load on the resistivity change was analyzed. The results show that the resistivity decreases first and then tends to stabilize with the increase of the G-CNTs content. When the G-CNTs content increases from 0.2wt% to 1.6wt%, the resistivity decreases by 51.8%. The resistivity is negatively correlated with temperature. When the G-CNTs content is higher than 0.8wt%, the piezoresistivity of the cement paste is significantly improved, and the rate of change in resistivity has an obvious corresponding relationship with the stress-strain. The stress sensitivity coefficient and the strain sensitivity coefficient of the specimens with 1.2wt% G-CNTs are 2.3%/MPa and 291, respectively. The amplitude of the rate of change in resistivity of G-CNTs/cement paste increases as the loading amplitude increasing. The rate of change in resistivity curve corresponding to the stress-strain changes under different loading speeds and constant load exhibits good piezoresistivity.
Influence of warp and weft fiber volume fractions on tensile mechanical properties of alkali-resistant glass textile reinforced concrete
ZHU Deju, LI Xinliang, LI Anling
2022, 39(1): 322-334. doi: 10.13801/j.cnki.fhclxb.20210306.002
Abstract:
In order to study the influence of the warp and weft fiber volume fractions on the tensile mechanical properties of alkali-resistant glass textile reinforced concrete (ARG-TRC), quasi-static tensile tests were conducted on specimens with various volume fractions of warp yarn (0.24vol%, 0.49vol%, 0.73vol% and 1.09vol%) and weft yarn (0vol%, 0.20vol%, 0.48vol% and 0.96vol%) by a universal testing machine, and the crack strain distribution was obtained by digital image correlation (DIC) method. The results show that the tensile mechanical properties and failure modes of ARG-TRC mainly depend on the volume fractions of warp yarn, and the volume fractions of weft yarn do not show obvious effect. With the increase of the volume fractions of the warp yarn, the ultimate strength, peak strain and toughness increase significantly as well as the number of cracks. A trilinear model was obtained by fitting the experimental tensile stress-strain curves, and was compared with the ACK model. The crack-spacing calculation formula was modified based on the existing crack-spacing calculation model and experimental data, which show good consistency with the literature data. The findings will be helpful for the optimization of the configuration of textile in textile reinforced concrete (TRC), and for the improvement of the utilization efficiency of textiles, and be available for the performance design of TRC.
Mechanical properties of alkali activated slag concrete with ultra fine dredged sand from Yangtze River
LI Shengtao, CHEN Xudong, ZHANG Wei, FENG Ziming, WANG Runmin
2022, 39(1): 335-343. doi: 10.13801/j.cnki.fhclxb.20210419.003
Abstract:
The physical and chemical properties of ultra-fine dredged sand in the lower reaches of the Yangtze River were analyzed. Five kinds of alkali activated slag concrete (AASC) mix proportions with different contents of ultra-fine dredged sand were designed. The fluidity, compressive strength, splitting tensile strength, density and water absorption were studied. The microstructure and phase composition of AASC were analyzed by SEM, XRD and mercury intrusion porosimetry (MIP). The results show that the fineness modulus of the ultra-fine dredged sand is between 0.1 and 0.5. With the increase of ultra-fine dredged sand content, the compressive strength and splitting tensile strength first increase and then decrease, while the fluidity continues to decline. When the dredged sand content (mass ratio to fine aggregate) reaches 50%, AASC obtains proper mechanical properties and workability. The results of water absorption, density test, SEM observation and MIP test show that the appropriate addition of dredged sand can increase the compactness of concrete and improve the structure of interface transition zone, but excessive dredged sand can reduce the fluidity of concrete and increase the porosity of concrete.
Test on axial compression performance and bearing capacity calculation of GFRP bars reinforced coral aggregate marine concrete columns exposed to tidal area
ZHOU Ji, CHEN Zongping, CHEN Yuliang, YAO Rusheng
2022, 39(1): 344-360. doi: 10.13801/j.cnki.fhclxb.20210323.003
Abstract:
In order to solve insufficient durability of steel bars and shortage of offshore construction materials, a new type of glass fiber reinforced polymer (GFRP) bars reinforced coral aggregate marine concrete column was proposed. 28 columns in marine tidal area were tested under axial compression. Firstly, the failure process of the specimens was observed, the load-displacement curves and the stress-strain data were obtained. Then, the failure mechanism of the specimens and the influence of various parameters on the mechanical properties were analyzed. At last, the bearing capacity calculation of this new type of member in the tidal area was discussed. The results show that the failure modes of GFRP bars reinforced coral aggregate marine concrete columns include wide and sparse cracks on the surface, coarse aggregate fracture and cover concrete divided into strips. Compared with the reinforced concrete (RC) specimen, the bearing capacity of GFRP bars reinforced coral aggregate marine concrete specimen decreases by 38%, and the strain of characteristic points is smaller. For GFRP specimens, increasing the reinforcement ratio of longitudinal bars or spiral stirrups can’t effectively improve the bearing capacity of specimens, but can improve their deformation performance. In the short-term tidal environment within 270 days, the bearing capacity of specimens first decreases and then increases, and the ductility shows a fluctuating trend with a variation amplitude of 25%. Finally, the calculation formulas for calculating the bearing capacity of the GFRP bars reinforced coral aggregate marine concrete columns in the tidal area were proposed by fitting and introducing variation parameters of material property.
Interaction direct deduction prediction model of thermal conductivity of dry cement mortar with mixed defects of cavities and cracks
LI Yunbo, LI Zongli, YAO Xiwang, XIAO Shuaipeng, LIU Shida, TONG Taotao
2022, 39(1): 361-370. doi: 10.13801/j.cnki.fhclxb.20210328.002
Abstract:
Cement mortar is prone to product defects during of pouring, curing and loading, which will significantly change its heat conducting properties. The defects in cement mortar were divided into two basic types of cavities and cracks according to its external characteristics and effects. Based on the interaction direct deduction (IDD) estimation method of mesomechanics theory, the prediction models of equivalent thermal conductivity of dry cement mortar with both cavities and cracks alone or in combination were established. Based on the inverse method of numerical simulation results, the random distribution influence function of the cracks was proposed, which improved the prediction accuracy of the proposed model. The IDD calculation results were compared with the numerical simulation results to verify its rationality and accuracy. The results show that the prediction model fully reflects the influence of different contents and characteristics of cavities and cracks on the equivalent thermal conductivity of cement mortar. The model has high prediction accuracy. The proposed random distribution influence function of cracks has high accuracy and good applicability. In the case of a certain defect rate, the effect of cavities on the equivalent thermal conductivity of cement mortar is more significant than that of cracks. The prediction model has a clear physical basis and a simple form, which is convenient for engineering applications.
Lateral impact resistance of BFRP tendon under different pretensions and impact energies
ZHU Deju, LI Zhenkun, GUO Shuaicheng, LI Sheng, YI Yong
2022, 39(1): 371-380. doi: 10.13801/j.cnki.fhclxb.20210324.001
Abstract:
In order to study the low-velocity impact performance of basalt fiber reinforced polymer (BFRP) tendon, the drop-weight impact test of the BFRP tendon was conducted to examine the low-velocity impact response under different pretension ratios (2%, 10%, 20%, and 30%) and impact energies (12.76 -31.90 J). Meanwhile, the residual tensile loading capacity of the incompletely broken specimens was further measured. Experimental results indicate that the failure modes of BFRP tendon include resin failure on the impact side, partial fracture of the fiber and complete fracture of the BFRP tendon. Under 19.14 J impact energy, the failure mode of the BFRP tendon changes from resin failure on the impact side to partial fracture of the fiber when the pretension ratio is increased from 2% to 10% and 20%. Meanwhile, the applied pre-tension enhances energy consumption, but the influence on the peak force is minimal. When the BFRP tendon is not completely broken, the residual deformation, energy consumption and the impact contact time of the specimen are negatively related to the pretension ratio. When the BFRP tendon is completely broken, the residual deformation of BFRP tendon decreases with the pretension ratio while the energy consumption and impact time first increases and then decreases with the pretension ratio. And the residual tensile loading capacity of the BFRP tendon decreases with the increase of impact energy. The impact damage level of BFRP tendon can be appropriately assessed with both the residual tensile loading capacity and the ratio between energy consumption and total impact energy (energy absorption ratio) of the specimen. The results of this study can provide important reference for the impact resistance design of the pre-tensioned BFRP tendon.
Composite Micro-mechanics
Low-velocity impact performance of grid-honeycomb hybrid core sandwich structure
ZHANG Yawen, CHEN Bingzhi, SHI Shanshan, MAO Haitao
2022, 39(1): 381-389. doi: 10.13801/j.cnki.fhclxb.20210311.002
Abstract:
A grid-honeycomb hybrid core was proposed and investigated to address the disadvantage of poor impact resistance of traditional composite sandwich structures. The impact test system of hemisphere-head drop hammer was used to study the low-speed impact response of the carbon fiber aluminum honeycomb sandwich structure. Based on the nonlinear constitutive and perfect interface assumption, the low-speed impact simulation model of the carbon fiber aluminum honeycomb sandwich panel was established and investigated. Research shows that the experimental and simulation results are in good agreement. Finally, the failure mode and mechanical response of grid-reinforced honeycomb hybrid core sandwich panels under different impact positions and impact angles were studied. The results show that there are huge differences in structural damage modes and energy absorption modes under different impact positions and different impact angles. The grid-honeycomb hybrid core can significantly improve the low-speed impact resistance of the structure, and has a good limiting effect on impact damage.
Ply optimization of carbon fiber reinforced plastic control arm based on grey relational analysis
JIANG Rongchao, CI Shukun, LIU Dawei, SUN Haixia, WANG Dengfeng
2022, 39(1): 390-398. doi: 10.13801/j.cnki.fhclxb.20210323.002
Abstract:
Carbon fiber reinforced plastic (CFRP) was used for lightweight design of suspension control arm. In order to perform the excellent mechanical properties of CFRP, the multi-objective ply optimization of CFRP control arm was carried out. The finite element model of the control arm was constructed based on the test results of material mechanical properties of CFRP. And the structural properties of the steel control arm and the CFRP control arm were compared by finite element simulations. Considering the mass, modal frequency, stiffness and strength, the orthogonal experiment design method combined with grey relational analysis and principal component analysis were used to optimize the CFRP control arm ply parameters for determining the optimal ply scheme. The results show that the mass of the optimized CFRP control arm is reduced by 40.23% compared with the original steel control arm, which achieves a significant weight reduction. Meanwhile, the structural performance indexes of the optimized CFRP control arm are improved, except for a slight decrease in longitudinal stiffness.
Buckling characteristics of composite grid/corrugated sandwich structure based on refined plate theory
ZHU Xiujie, ZHENG Jian, XIONG Chao, YIN Junhui, DENG Huiyong, ZOU Youchun
2022, 39(1): 399-411. doi: 10.13801/j.cnki.fhclxb.20210309.003
Abstract:
An analytical model for analyzing the buckling characteristics of full composite grid/corrugated sandwich panels was provided. Regarding the corrugation and the grid core as a continuous single layer, the internal force-strain relationship of the full composite corrugated/grid sandwich panel was derived based on the refined plate theory. On the basis of considering the anisotropy and transverse shear deformation of the composite core panel, the equivalent elastic constants of composite orthogonal grid and trapezoidal corrugations cores were deduced based on the homogenization theory. Using the minimum potential energy principle, the buckling balance differential equation of full composite grid/corrugated sandwich panels was obtained, and the critical buckling load under three boundary conditions was transformed. The analytical results were compared with the finite element simulation and the errors are within 5%, which validates the correctness and effectiveness of the analytical model. The verified model was used to compare and analyze the effect of the layers angle, number of layers as well as the height of core, inclination angle of corrugation and grid spacing on the critical buckling load and the specific critical buckling load of the full composite grid/corrugated sandwich pane, which provides theoretical guidance for the buckling characteristic analysis and optimal design of this type of structure.
Uncertainty analysis of natural vibration characteristics of composite laminated plates with spatially varied stochastic volume fractions
YU Ruyu, ZHANG Xufang
2022, 39(1): 412-423. doi: 10.13801/j.cnki.fhclxb.20210310.004
Abstract:
In each layer of the composite laminate, the spatial uncertainty effect of the volume fraction was considered. Using exponential autocorrelation function, the relationship between the volume fraction of each layer and the spatial position was simulated. Combining the Galerkin-Riza discretization and K-L series expansion methods, the influence of autocorrelation length on the discretization accuracy was carried out. The stochastic finite element model of composite laminates with spatially random material properties was established. Taking the T300 carbon fiber/QY8911 epoxy aircraft vertical tail thin-gauge skin structure as an example, the relationships between the mean value, standard deviation and coefficient of variation of the natural frequency and the number of laminate layers were obtained. And the Monte-Carlo simulation method was used to verify the effectiveness of the method in this paper to carry out the natural frequency and mode uncertainty analysis of composite laminates. The results show that: the coefficient of variation of the natural frequency of the composite laminate structure increases with the decrease of the number of layers, and the less the number of layers, the greater influence of uncertainty of the fiber volume fraction on dispersion of the natural vibration characteristics.
Thermal scale effect analysis of enhanced Reddy’s laminated composite based on new modified couple stress theory
SI Junling, ZHANG Ying, YIN Dawei
2022, 39(1): 424-430. doi: 10.13801/j.cnki.fhclxb.20210301.003
Abstract:
Based on new modified couple stress theory, a model of thermal scale effect was proposed for the laminated composite plates of enhanced Reddy theory. The model contained only one materials length parameter \begin{document}$\ell $\end{document}, and the rotation variable was introduced through thickness direction for the first time. The equilibrium equations for the model were presented from the principle of virtual work, and displacements and stresses of micro-laminated composite/sandwich plates were analyzed by using Navier’s method under thermal loading. Numerical results show that the model can capture the thermal scale effect of plates well. As the material length parameter increases, the scale effects of plates are enhanced. Meanwhile, the scale effects are weakened with increasing of span-thickness ratio of plates, but there is a decline in the weakening extend.