Compressive properties of glue-laminated timber circular post modified by basalt fiber reinforced polymer

Glued timber structure is one of the main forms of modern wood architecture,which has gradually developed towards mid-and high-rise buildings.Glue-laminated timber(GLT)is comprised of several laminates of parallel-to-grain dimension lumber that are bonded together with durable,moisture resistant structural adhesives.GLT can be used in horizontal applications as a beam and in vertical applications as a post.So,its compressive performance has a significant impact on structural safety.Fiber reinforced polymers(FRPs)were commonly used to improve the bearing capacity of GLT components,and the structural and process parameters largely determined the reinforcement effect.This study was aimed at investigating the influence of structural and process parameters on the axial compression performance of GLT components.Three wrapping methods(middle-part,end-part and full wrapping)and three lengths(0.6,0.8,and 1.0 m)of wood post specimens were designed in this work and the axial compression performance and ductility of GLT post specimens modified by basalt fiber reinforced polymer(BFRP)were studied.The results showed that the effect of different BFRP wrapping methods on the compressive strength and elastic modulus of laminated wood was not statistically significant(P>0.05).The compressive bearing capacity of unreinforced GLT posts decreased with the increase of aspect ratio.The GLT posts with middle-part and end-part wrapping still followed this pattern,while the compressive bearing capacity of GLT posts with full wrapping showed a pattern of first decreasing and then increasing.For GLT with low aspect ratios(4.0 or 5.3),there was no correlation between the wrapping method and the compressive bearing capacity,while the compressive bearing capacity of GLT with a high aspect ratio(6.7)for middle-part,end-part and full wrapping increased by 3.5%,7.5%and 9.7%,respectively.Compared to the unreinforced group,the ultimate axial compressive strength and modulus of elasticity(MOE)of the 6-E series specimens reinforced at both ends decreased by 2.58%and 6.70%,respectively.The ultimate axial compressive strength of the 8-E specimens reinforced at both ends increased by 8.62%and the MOE decreased by 1.91%.The compressive strength of the 10-E specimens reinforced at both ends increased by 7.51%and the MOE increased by 8.14%.The failure modes of GLT with different aspects were consistent under the same BFRP wrapping,while the failure modes of GLT with the same aspect ratio were different for different BFRP wrapping methods.The ductility performance of GLT with different aspects ratio was improved by the BFRP wrapping.

BFRP筋回收轮胎钢纤维混凝土黏结性能分析

对玄武岩纤维增强复合材料(BFRP)筋在回收轮胎钢纤维(RTSF)混凝土中的黏结性能进行了试验和分析研究.对不同RTSF体积掺量、BFRP筋直径和嵌入长度的试件进行了拉拔试验,研究其对黏结破坏模式、黏结滑移响应和黏结强度的影响,并提出了BFRP筋RTSF混凝土的黏结滑移理论模型.结果表明:BFRP筋RTSF混凝土黏结破坏类型包括拔出破坏、劈裂破坏以及拔出且劈裂破坏;BFRP筋直径对黏结破坏模式无显著影响,而RTSF体积掺量、BFRP筋直径和嵌入长度均对黏结强度有较大影响,且RTSF体积掺量与极限黏结强度呈正相关,BFRP筋直径和嵌入长度对其影响与之相反;当RTSF体积掺量从0增大至1.5%时,其极限黏结强度最大可提高约23.87%.与已有模型相比,所提出的黏结滑移理论模型对BFRP筋RTSF混凝土的黏结滑移曲线具有更高的拟合精度.

BFRP模壳不排水加固RC墩柱恢复力模型

为研究玄武岩纤维增强聚合物(basalt fiber reinforced polymer, BFRP)模壳不排水加固钢筋混凝土(reinforced concrete, RC)墩柱抗震恢复力模型,在拟静力试验基础上,采用OpenSees有限元软件对模壳加固墩柱进行数值分析,主要研究参数为填充层混凝土强度、模壳厚度、加固高度、轴压比。研究表明:填充层混凝土强度等级越高,墩柱抗震性能有所增强,但C40以上的填充层混凝土强度等级墩柱的抗震性能较为接近;模壳加固厚度较大墩柱的抗震性能优于厚度较小墩柱;当模壳加固高度较高时,墩柱的抗震性能较好,当加固高度大于2~3倍原墩柱塑性铰高度时,抗震性能提升效果趋于稳定;轴压比越大,墩柱的刚度退化较快,不利延性发展。后通过数据回归分析,建立了BFRP模壳加固RC墩柱恢复力模型,对比可知,恢复力模型与试验曲线拟合较好,能有效反映加固墩柱的滞回性能,可为此类结构的抗震性能分析提供参考。

Research on Radiation Characteristics of Polymeric Plastic Fiber

The anti-radiation mechanism of polymeric plastic fiber is analyzed. The radiation characteristic of this type fiber is studied. Our experimental results indicate that under the low radiation dosage (below 1 kGy) the plastic optical fiber’s transmission rate rises instead of descends while this type of fiber is radiated by γ ray, electron beam and proton beam respectively. After a period of time, it gradually reaches a constant value. But under the high radiation dosage (above 1 kGy) the fiber’s transmission rate descends after radiation. Later, it gradually goes up to a constant value.

Quasi-solid-state polymer plastic crystal electrolyte for subzero lithium-ion batteries

Succinonitrile(SN)-based polymer plastic crystal electrolytes(PPCEs)have attracted considerable attention as solid-state electrolytes owing to their high ionic conductivities similar to those of liquid electrolytes,excellent contacts with the electrodes,and good mechanic properties.As a crucial property of a solid-state electrolyte,the ionic conductivity of the PPCE directly depends on the interactions between the constituent parts including the polymer,lithium salt,and SN.A few studies have focused on the effects of polymer–lithium–salt and polymer–SN interactions on the PPCE ionic conductivity.Nevertheless,the impact of the lithium–salt–SN combination on the PPCE ionic conductivity has not been analyzed.In particular,tuning of the lithium-salt–SN interaction to fabricate a subzero PPCE with a high low-temperature ionic conductivity has not been reported.In this study,we design and fabricate five PPCE membranes with different weight ratios of Li N(SO2 CF3)2(Li TFSI)and SN to investigate the effect of the Li TFSI–SN interaction on the PPCE ionic conductivity.The ionic conductivities of the five PPCEs are investigated in the temperature range of–20 to 60°C by electro-chemical impedance spectroscopy.The interaction is analyzed by Fourier-transform infrared spectroscopy,Raman spectroscopy,and differential scanning calorimetry.The Li TFSI–SN interaction significantly influences the melting point of the PPCE,dissociation of the Li TFSI salt,and thus the PPCE ionic conductivity.By tuning the Li TFSI–SN interaction,a subzero workable PPCE membrane having an excellent low-temperature ionic conductivity(6×10-4 S cm–1 at 0°C)is obtained.The electro-chemical performance of the optimal PPCE is evaluated by using a Li Co O2/PPCE/Li4 Ti5 O12 cell,which confirms the application feasibility of the proposed quasisolid-state electrolyte in subzero workable lithium-ion batteries.

Humanoid Based Intelligence Control Strategy of Plastic Cement Die Press Work-Piece Forming Process for Polymer Plastics

The plastic cement belongs to a sort of polymer material, the chemical composition is very complex, and the plastic cement work-piece is generally manufactured by die press forming. Aimed at being difficult to control in parameters of forming process, the paper explored the humanoid based intelligence control strategy. In the paper, it made the anatomy in control puzzle resulted in uncertainty such as chemical component of plastic cement etc., summarized up the characteristic of cybernetics in forming process, researched on the humanoid based intelligence control strategy, and constructed the control algorithm of forming process in plastic cement work-piece. Taking the process experiment of temperature and pressure control as an example, it validated the good dynamic and static control quality through simulation of control algorithm constructed in this paper. The experimental results show that the control algorithm explored in this paper is reasonably available.

Tailoring the Properties of Polyhydroxyalkanoates from Plastics to Elastomers via Stereoselective Copolymerizations of rac-β-Butyrolactone and β-Propiolactone

Poly(3-hydroxybutyrate),a crucial member of the large biodegradable polyhydroxyalkanoate family,suffers from its brittleness.To enhance its performance,we employed a straightforward approach involving the ring-opening copolymerization of racemic-β-butyrolactone(rac-β-BL)andβ-propiolactone(β-PL)using the syndio-selective amino-alkoxy-bis(phenolate)-yttrium complex as a catalyst,thanks to the excellent ductility of poly(3-hydroxypropionate).Control over the rac-β-BL/β-PL feeding ratios and polymerization time yielded random or block copolymers with tunable thermal and mechanical properties comparable to traditional fossil-based plastics.Furthermore,we achieved one-pot synthesis of hard-soft-hard triblock copolymers by exploiting monomers’different copolymerization rates and a bifunctional initiator,thus transforming polyhydroxyalkanoates from hard and tough plastics to soft and ductile thermoplastic elastomers.

Recycled polymer:Green roads for polyester plastics

Plastics are integral to numerous significant social advancements.Nonetheless,their contribution to environmental pollution and climate crises cannot be disregarded,as their negative impact on the environment increases with incremental production capacity and demand.Concerted global action is urgently required to promote the green recycle of plastics to prevent their accumulation in the environment and mitigate carbon emissions.This review aims to reveal the paths of green development for polyester plastics,incorporating the trends of the green revolution in mature commercial polyester plastics,newly emerging biodegradable polyester plastics,and future polyester plastics.A critical discussion was conducted on the current and potential future research areas from multiple perspectives,including raw materials,processes,and recycling,to propel us into a future marked by sustainability.

Factors Influencing Strength of Super Absorbent Polymer(SAP)Concrete

Super absorbent polymers (SAPs) are gradually being applied in concrete production as internal curing agents. SAP can effectively reduce early age autogenous shrinkage of concrete, alleviate the hazards caused by concrete cracking and improve its freeze–thaw resistance. However, the relationships between SAP dosage, SAP particle size and the water–cement ratio of concrete have certain influences on the evolution of the compressive strength of SAP-incorporated concrete. In this study, experiments were conducted to investigate the relationships between the water–cement ratio of concrete, the SAP dosage and SAP particle size. The significant factors influencing concrete strength are determined and equations are proposed for predicting the strength of SAP-incorporated concrete at 3, 7 and 28 days. The findings from this study, such as the SAP dosage should not be larger than 0.2%, are expected to form a theoretical basis for the rational use of SAP as an additive to concrete. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Hybrid polymer electrolyte for Li–O_2 batteries

Li–O_2 batteries have attracted much attention because of their high specific energy. However, safety problem generated mainly from the flammable organic liquid electrolytes have hindered the commercial use of Li–O_2 batteries. One of the competitive alternatives is polymer electrolytes due to their flexibility and non-flammable property. Moreover, the hybrid polymer electrolyte with enhanced electrochemical properties would be achieved by incorporating inorganic filler, liquid plasticizer and redox mediator into the polymer. While most researches of the hybrid polymer electrolyte focused on Li-ion batteries, few of them took account into its application in Li–O_2 batteries. In this review, we mainly discuss hybrid polymer electrolytes for Li–O_2 batteries with different composition. The critical issues including conductivity and stability of electrolytes are also discussed in detail. Our review provides some insights of hybrid polymer electrolytes for Li–O_2 batteries and offers necessary guidelines for designing the suitable hybrid polymer electrolyte for Li–O_2 batteries as well.

Modified Vegetable Oil Based Additives as a Future Polymeric Material—Review

Polymeric materials from renewable resources have attracted a lot of attention in recent years. The development and utilization of vegetable oils for polymeric materials are currently in the spotlight of the polymer and chemical industry, as they are the largest renewable platform due to their universal wide availability, ingrained biodegradability, low cost, and excellent environmental aspects (i.e., low ecotoxicity and low toxicity toward humans). These excellent natural characteristics are now being taken advantage of in research and development, with vegetable oil derived polymers/polymeric materials/composites being used in numerous applications including paints and coatings, adhesives, and nanocomposites. The aim of this review paper is to give a fundamental description of the various vegetable oil applications in polymer materials and its recent developments. Particular emphasis will be placed on study and main application of triglyceride based additive for polymer and to give the reader an insight into the main developments is discussed.

Synthesis and characterization of novel low band-gap polymers containing squaraine units

Novel conjugated polymers based on squaric acid having 2,5-Bis[（E）-N-alkylpyrrol-2-ylvinyl]-3-alkylthiophene （PVTVP） unit in the main chain were successfully synthesized in good yields through polycondensation reaction. Their molecular structures were characterized by PT-IR and IH NMR. They have good solubility in common organic solvents, good thermal stability by thermal gravimetric analysis and high molecular weights. Their optical properties were investigated by UV-vis absorption spectra in CH2C12 solution, the results indicated all these compounds showed broad and strong spectral responses from 200 nm to 900 nm, suggesting their potential for application as organic plastic solar cells.

初始静载对不同剪跨比BFRP筋混凝土梁动态剪切性能的影响

为揭示初始静载对玄武岩纤维增强(basalt fiber reinforced polymer,BFRP)筋混凝土(BFRP-RC)梁动态剪切性能的影响,建立了考虑混凝土非均质性、混凝土与BFRP筋间相互作用及各材料应变率效应的三维细观数值模型。在验证了该模拟方法合理性与准确性的基础上,分析了初始静载对不同剪跨比BFRP-RC梁破坏过程与失效机制的影响。研究结果表明:BFRP-RC梁的抗剪承载力及变形能力均随应变率增大而提高;应变率对梁抗剪承载力的增强作用随剪跨比增大而减弱;在峰值荷载前应变率突增,BFRP-RC梁的刚度增加,抗剪承载力提高;在峰后软化段应变率突增,BFRP-RC梁的峰后软化转变为峰后硬化,而后出现第二峰值荷载;BFRP筋混凝土梁的动态抗剪承载力均随初始静载增大而降低,但梁抗剪承载力的降低量是否与后续应变率有关取决于初始静载水平;在各应变率下,BFRP筋混凝土梁的变形能力及损伤程度均随初始静载的增大而减小,但增大后续应变率会削弱初始静载对梁动态性能的影响。

Experimental Investigation of Natural Fiber Reinforced Polymers

The potential usage of virgin Low density polyethelyne (LDPE) reinforced with different concentrations (2%, 5% and 6% by weight) of treated rice straw with different lengths (2 mm, 4 mm and 6 mm) is investigated to produce high value products that have technical and environmental demand. The two treatment methods used for rice straw are alkali and acidic treatments of rice straw. The removal of impurities and waxy substances from fiber surface avoid creation of rougher topography after treatment and improves the quality of fiber, also content of hemi cellulose and lignin decrease so increase effectiveness of fiber due to dispersing of fiber in matrix. The reinforcing material is embedded in the matrix material to enhance tensile and flexural behaviors of the synthesized composite. The result of investigating these two mechanical properties, using statistical analysis & design of experiments, showed an enhancement in the mechaniccal properties of the virgin polymer composite compared to the virgin polymer. The flexural stress of the composite increased three times the virgin flexural stress, while the tensile stress increased eight times the original tensile stress.

BFRP筋增强海水海砂混凝土梁的抗冲击性能

为研究玄武岩纤维增强复合材料(basalt fiber reinforced polymer,BFRP)筋增强海水海砂混凝土(seawater sea-sand concrete,SSC)梁的抗冲击性能,利用落锤冲击装置研究了不同冲击能量(1818 J,2727 J,3636 J,4848 J)作用下,不同混凝土强度(30 MPa,50 MPa)和配筋率(0.23%,0.48%)的BSFP-SSC梁冲击响应,并测试了冲击后梁的残余承载力。结果表明,随着冲击能量的增加,BFRP-SSC梁的破坏模式由弯曲破坏转变为剪切破坏,梁的残余承载力系数逐渐降低。提高配筋率或海水海砂混凝土强度,均可有效降低梁的最大跨中位移,提升初始峰值冲击力和抗冲击性能。该研究可为BFRP筋增强海水海砂混凝土梁的抗冲击设计提供重要依据。

玻璃纤维增强聚合物管约束高强混凝土柱轴压试验研究

为研究玻璃纤维增强聚合物管约束高强混凝土柱的轴压性能,设计了6个不同长细比的试件并对其进行了轴心受压试验,分析了其破坏过程及破坏形态、承载力、位移、荷载-位移曲线、骨架曲线、荷载-应变曲线。研究表明:玻璃纤维增强聚合物管约束混凝土柱轴压承载性能优异,随着长细比的减小,试件的轴压承载力提升显著;加载后期,该组合结构的破坏模式为玻璃纤维增强聚合物管发生环向破坏,内部混凝土被压溃;玻璃纤维增强聚合物空管轴压承载力相对较低,破坏时脆性特征明显;随着长细比的减小,玻璃纤维增强聚合物管约束高强混凝土柱的承载力和刚度逐步增加,长细比对结构的承载能力影响显著。研究结果对玻璃纤维增强聚合物管约束高强混凝土柱的理论研究和工程应用具有一定的指导意义。

高性能高分子材料体系自立自强发展战略研究

高性能高分子材料具有高强高模、高绝缘、耐腐蚀、耐辐照或绿色低碳等特点,是保障国家安全和国民经济发展的战略性材料之一,广泛应用于航空航天、电子电器、生物医疗等重要领域。本文系统梳理了高性能树脂及工程塑料、有机纤维、生物基树脂及可降解材料、特种橡胶及弹性体四大类高性能高分子材料中的重点品种,分析了国内外重点品种的发展现状和特点。研究发现,目前我国在高性能高分子材料方面已建立起比较完备的化工原料–合成–加工改性–制品应用上下游产业体系,但同时也存在关键原料保障不足、产品应用开发有待拓展等问题。在此基础上,从加强技术创新、推进关键原料保障、组建创新联合体等方面提出对策建议,以期为我国高性能高分子材料体系发展提供参考。

Strengthening effects of BFRP on reinforced concrete beams

Reinforced concrete （RC） beams externally bonded with basalt fiber reinforced polymer （BFRP） are experimentally investigated by using different numbers of bonding plies, transverse anchorages as well as the initial conditions of strengthened beams. The performances of the BFRP strengthening are compared with those of the carbon fiber reinforced polymer （CFRP） and the glass fiber reinforced polymer （GFRP） under the same experimental condition. Experimental results indicate that the strength and ductility of the strengthened beam with two plies of the BFRP are improved remarkably than those with one ply. The strengthening effects of the BFRP lie between those of the CFRP and the GFRP. The BFRP strengthening is little influenced by pre-cracks of concrete. Most failures are caused by interfaciai debonding induced by flexural cracks in the experiment. Clamping of Uwraps along the whole beam is less efficient than endpoint anchorage for increasing the ultimate load of the strengthened beam. Finally, the models suggested by the five guidelines for predicting the debonding strain of the CFRP are extended to the BFRP and the conservative estimates of the debonding strain of the BFRP are given as well.

Experimental study on the durability of BFRP bars embedded in concrete

This paper presents an experimental study on the alkali-resistant properties of basalt fiber reinforced polymers （BFRP） bars under a typical concrete environment. BFRP bars were embedded in concrete and exposed to different aggressive environments, including tap water, saline solution and ambient temperature environments, to study the effects of the type of solution and relative humidity （RH） on the durability of BFRP. Meanwhile, BFRP bars were directly immersed in an alkaline solution for comparison. The acceleration factor describing the relationship between the alkaline solution immersion and the moisture-saturated concrete was also obtained. Aging was accelerated with a temperature of 60 ℃. The results show that the chloridion in the saline solution does not have any harmful effects on the degradation of the concrete-encased BFRP bars. Contact with an alkaline （high pH） concrete pore-water solution is the primary reason for the degradation of the BFRP bars. The degradation rate of concrete-encased BFRP bars is accelerated when a high temperature and a high humidity are present simultaneously. The degradation rate of the BFRP bars is relatively quick at the initial stage and slows down with exposure time. Results show that the degradation of 2.18 years in moisture-saturated concrete at 60 ℃corresponds to that of one year when directly immersed in an alkaline solution （other conditions remaining the same） for the BFRP bars analyzed.