Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part I: Experimental study

This work is aimed at studying the strengthening of reinforced concrete (R. C.) beams using prestressed glass fi- ber-reinforced polymer (PGFRP). Carbon fiber-reinforced polymer (CFRP) has recently become popular for use as repair or rehabilitation material for deteriorated R. C. structures, but because CFRP material is very stiff, the difference in CFRP sheet and concrete material properties is not favorable for transferring the prestress from CFRP sheets to R. C. members. Glass fi- ber-reinforced polymer (GFRP) sheets with Modulus of Elasticity quite close to that of concrete was chosen in this study. The load-carrying capacities (ultimate loads) and the deflections of strengthened R. C. beams using GFRP and PGFRP sheets were tested and compared. T- and ⊥-shaped beams were used as the under-strengthened and over-strengthened beams. The GFRP sheets were prestressed to one-half their tensile capacities before being bonded to the T- and ⊥-shaped R. C. beams. The prestressed tension in the PGFRP sheets caused cambers in the R. C. beams without cracks on the tensile faces. The PGFRP sheets also enhanced the load-carrying capacity. The test results indicated that T-shaped beams with GFRP sheets increased in load-carrying capacity by 55% while the same beams with PGFRP sheets could increase load-carrying capacity by 100%. The ⊥-shaped beams with GFRP sheets could increase load-carrying capacity by 97% while the same beams with PGFRP sheets could increase the loading-carrying capacity by 117%. Under the same external loads, beams with GFRP sheets underwent larger deflections than beams with PGFRP sheets. While GFRP sheets strengthen R. C. beams, PGFRP sheets decrease the beams’ ductility, especially for the over-strengthened beams (⊥-shaped beams).

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part I of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP (glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.

STUDY ON THE POLYMERIZATION DEGREE OF SILICATE ANIONS IN THE SILICATE GLASS BY TRIMETHYLSILYLATION METHOD

In the present paper,a mixed solvent method is applied to the trimethylsilylation of silicate glass,and the polymerization degree and its distribution of silicate anions in the silicate glass are measured by means of the analyses of gas chromatography-mass spectrography.

Preparation and Mechanical Properties of UV⁃Assisted Filament Winding Glass Fiber Reinforced Polymer⁃Matrix Composite

This paper studied the preparation and mechanical properties of glass fiber reinforced polymer-matrix composite rings prepared by filament winding assisted by ultraviolet(UV)curing.A ray-tracing method was used to calculate the penetration ability of UV light in the resin casting,and then a typical composite ring with dual⁃curing characteristics was prepared by UV-assisted curing.The effects of winding speed and thermal initiator concentration on the distribution of fiber fraction and mechanical properties were studied.Microscopic morphology was used for the observation of the differences in fiber volume fraction.Mechanical properties tests and scanning electron micrographs were performed to investigate the failure and damage mechanisms of the composite ring samples.The ray tracing results indicate that the UV light can pass through a single yarn thickness and the energy transmitted is sufficient to cure the back side quickly.The experimental results show that the mechanical properties of the composite ring prepared in this paper are comparable to those of the heat-cured samples,which is sufficient to meet the requirements of the flywheel.

原位聚合法制备连续玻璃纤维增强尼龙6复合材料的改性和性能

尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,文中对连续玻璃纤维增强尼龙6(CGF/PA6)复合材料开展了研究。首先,采用阴离子开环聚合制备PA6,确定了其最佳制备工艺;其次,用硅烷偶联剂KH550(AP)对连续玻璃纤维(CGF)进行改性,并对其进行了红外光谱表征;最后,通过原位聚合法制备了CGF/PA6复合材料,研究了AP改性对CGF/PA6复合材料力学性能的影响,并对CGF/PA6复合材料的拉伸断口进行了扫描电镜分析。结果表明,AP被键合到了CGF表面,AP改性可以增强CGF/PA6复合材料的界面黏附性,从而使CGF/PA6复合材料的拉伸强度得到改善,当AP用量为2%时,CGF/PA6复合材料的拉伸强度高达88.52 MPa,此时,复合材料的断裂伸长率最低,为4.90%。CGF/PA6复合材料的冲击强度变化不大,均在50 k J/m2左右,说明复合材料的韧性受CGF表面改性影响较小。

XPS and Raman studies of electron irradiated sodium silicate glass

The microstructure modifications of sodium silicate glass induced by 1.2-MeV electron irradiation are studied by x-ray photoelectron spectroscopy and Raman spectroscopy. Depth profile analyses are also performed on the irradiated glass at 109 Gy. A sodium-depleted layer with a thickness of a few tens of nanometers and the corresponding increase of network polymerization on the top surface are observed after electron bombardment, while the polymerization in the subsurface region has a negligible variation with the irradiation dose. Moreover, the formation of molecular oxygen after electron irradiation is evidenced, which is mainly aggregated in the first two-micron-thick irradiated glass surface. These modifications are correlated to the network relaxation process as a consequence of the diffusion and desorption of sodium species during electron irradiation.

Chemical Mechanical Polishing of Glass Substrate with α-Alumina-g-Polystyrene Sulfonic Acid Composite Abrasive

Abrasive is the one of key influencing factors during chemical mechanical polishing（CMP） process. Currently, α-Alumina （α-Al2O3） particle, as a kind of abrasive, has been widely used in CMP slurries, but their high hardness and poor dispersion stability often lead to more surface defects. After being polished with composite particles, the surface defects of work pieces decrease obviously. So the composite particles as abrasives in slurry have been paid more attention. In order to reduce defect caused by pure α-Al2O3 abrasive, α-alumina-g-polystyrene sulfonic acid （α-Al2O3-g-PSS） composite abrasive was prepared by surface graft polymerization. The composition, structure and morphology of the product were characterized by Fourier transform infrared spectroscopy（FTIR）, X-ray photoelectron spectroscopy（XPS）, time-of-flight secondary ion mass spectroscopy（TOF-SIMS）, and scanning electron microscopy（SEM）, respectively. The results show that polystyrene sulfonic acid grafts onto α-Al2O3, and has well dispersibility. Then, the chemical mechanical polishing performances of the composite abrasive on glass substrate were investigated with a SPEEDFAM-16B-4M CMP machine. Atomic force microscopy（AFM） images indicate that the average roughness of the polished glass substrate surface can be decreased from 0.835 nm for pure α-Al2O3 abrasive to 0.583 nm for prepared α-Al2O3-g-PSS core-shell abrasive. The research provides a new and effect way to improve the surface qualities during CMP.

Influences of SiO2/Na2O Molar Ratio on Aging and Chemical Modification of Water Glass

In this paper, the content of water glass before and after adding modifying agent was measured by Trimethylsilyl-gas-chromatography. The experimental results showed that different modulus of water glass could generate different content of mono-silicate acid and oligomeric silicate acid in water glass. After a period of storage, different modulus of water glass led to decrease of silicate content at different levels. Because higher content of Na2O in water glass tended to incur the alkaline polymerization, the occurrence of depolymerization of silicate species would lead to an increase of oligomeric silicate species, resulting in a drawback of silicate species content after a period of storage. And contrary to that, lower content of Na2O in water glass tended to incur the acidic polymerization. When the modifying agent was added to the newly made water glass, the amount of mono-silicate acid and oligomeric silicate acid also decreased. In modified water glass, the change of each silicate acid species was less than that in unmodified water glass. These results showed that the modifying agent retarded the aging of water glass. It had remarkable significance on the theory and practical application of water glass chemistry.

基于因子设计的低温快干卷烟接嘴水基胶的制备

【目的】降低接嘴胶的玻璃化转变温度。【方法】选取乳化剂、增塑剂及3种聚合单体的配比为试验因子,采用因子设计法探究各因子及其交互作用对玻璃化转变温度的影响规律,并制备出低温快干接嘴胶。【结果】①乳化剂及3种单体的配比是影响接嘴胶玻璃化转变温度的主要因子,且乳化剂与乙酸乙烯酯(VAc)和丙烯酸(AA)、丙烯酸丁酯(BA)与AA间存在交互作用;②在试验所涉及的水平范围内,玻璃化转变温度随着BA及乳化剂用量增加而降低,随着VAc及AA用量的增加而升高;③乳化剂、VAc、BA及AA的配比分别为5.50%、24.00%、12.00%、0.40%时,接嘴胶的玻璃化转变温度可降至-1.83℃,95%置信水平下的置信区间为(-6.44,2.79)℃。【结论】采用因子设计法对水基胶主要原料的配比进行优化,能明显降低接嘴水基胶的玻璃化转变温度。

高分子量聚异丁烯制备影响因素分析

以稀土金属钪正离子配合物为催化剂研究了异丁烯催化聚合反应,通过筛选催化体系、调节单体与催化剂配比、调控反应温度和反应时间等一系列影响因素,对聚异丁烯的分子量及其分布和玻璃化转变温度进行了考察。结果表明,在5种稀土金属钪正离子催化剂中,空间位阻相对较小的限制几何构型钪双烷基催化剂对异丁烯的催化活性最高;异丁烯单体与催化剂的物质的量之比越大,所得聚合物的数均相对分子质量就越高;聚合反应温度越低,聚合物的数均相对分子质量就越高,但当温度低于-60℃时聚合物的数均相对分子质量却大幅减小;聚合反应时间对聚合物相对分子质量变化的影响不大;此外,聚合反应温度和聚合反应时间对聚异丁烯玻璃化转变温度无明显影响。

原位聚合PLA/HA复合材料的性能研究

采用原位聚合法和超声波辅助分散溶液共混法,分别制备了羟基磷灰石质量分数为30%的聚乳酸(PLA)/羟基磷灰石(HA)生物可降解复合材料,对其结构与力学性能进行了研究。结果表明,HA的存在对乳酸的聚合有一定的影响,使其摩尔质量降低、分布变宽。与共混法相比,原位聚合法改善了HA在复合材料中的分散性,在PLA与HA之间形成了较强的结合界面,从而提高了PLA玻璃化温度和力学性能。

苯丙乳液的制备及其性能影响因素研究

以苯乙烯、丙烯酸丁酯为主单体,丙烯酸(AA)为功能单体,SDS/OP-10为复合乳化剂,过硫酸铵为引发剂,采用单体预乳化、半连续种子乳液聚合工艺,制备出性能优异的苯丙乳液。采用FT-IR、DSC、GPC、Nano-ZS90等对聚合物乳液进行了表征,系统研究了单体配比、复合乳化剂、引发剂用量、聚合温度等因素对乳液成膜性、耐水性、稳定性等常规性能的影响。结果表明,乳胶粒粒径受复合乳化剂种类及用量的影响较大,同时也与引发剂用量有关;单体配比是乳液玻璃化温度(Tg)的关键影响因素。

开环聚合酚醛树脂基复合材料的研究——ALPF/GF层压板的研制

合成了含有环状结构的苯并恶嗪中间休,加入适量催化剂,通过开环聚合制得一种新型酚醛树脂基玻璃有层压板。采用凝胶化时间测定、差热分析、热重分析等方法研究了树脂的固化行为和热稳定性,确定了较为合理的玻璃布浸胶、烘焙和压制条件。性能测试表明,玻璃布层压板的耐电弧性达183s,氧指数为52,在155℃的弯曲强度为350MPa,其弯曲强度保持率达59％,而电性能在155℃保持良好,适于用作155℃使用的耐高温结构材料和电绝缘材料。

PEEK/ZrO_2固体合金的探索研究

在聚醚醚酮 (PEEK)玻璃化转变温度以下 ,用外动式高能旋转球磨机使PEEK和二氧化锆 (ZrO2 )混合物反复变形、断裂和结合 ,并形成新的相 ,即形成PEEK/ZrO2固体合金 .通过扫描电镜 (SEM)、差示扫描量热仪 (DSC)、红外光谱 (FT IR)和动态热力学分析装置 (DMTA)对PEEK/ZrO2 =1/2和 2 /1固体合金的结构及性能进行研究 ;并与纯PEEK对比 ,探讨PEEK与ZrO2 形成固体合金的可能性 ;讨论固体合金化工艺对PEEK/ZrO2 固体合金性能的影响 ,分析PEEK/ZrO2

开环聚合酚醛树脂复合材料的研究──ALPF3-EGF层压板的研制

采用低分子量可溶性酚醛树脂合成了一种新型的苯并噁嗪中间体（ＡＬＰＦ３）树脂溶液，制备了高性能的玻璃布层压板。采用凝胶时间测定、差热分析和热重分析等方法研究了树脂的固化行为和热稳定性，确定了较为合理的玻璃布浸胶、烘焙和压制工艺，测试了玻璃布层压板的一般性能。结果表明，ＡＬＰＦ３树脂溶液及浸胶玻璃布贮存期长、工艺性好；玻璃布层压板性能优良，玻璃化转变温度达２８０℃，常态和１８０℃的弯曲强度为４６３ＭＰａ和３８０ＭＰａ，保留率达８２％。适用于１５５～１８０℃用的耐高温结构材料和电绝缘材料。

开环聚合酚醛树脂基玻璃布层压板耐化学腐蚀性能的研究

采用苯并恶嗪中间体与环氧树脂为主要原料合成粘接剂，经ＫＨ５６０处理的无碱玻璃布制成了高性能的玻璃布层压板。采用常规手段和ＩＲ、光学显微照相等方法，研究了玻璃布层压板在各种化学介质、不同温度下的耐化学腐蚀性能及化学腐蚀形貌。结果表明，玻璃布层压板在真空泵油、浓氨水和浓磷酸、饱和食盐水中均显示出良好的耐腐蚀性，可望作为耐化学腐蚀的结构材料。

耐热ABS树脂的制备

采用乳液聚合法合成了一系列 N-苯基马来酰亚胺(NPMI)-苯乙烯(St)-丙烯腈(AN)共聚物(简称SMIA 树脂),将其与 AN-丁二烯-St 三元共聚物(ABS)熔融共混制备了耐热 ABS 树脂。采用傅里叶变换红外光谱、差示扫描量热法对 SMIA 树脂进行了表征,探讨了 SMIA 树脂组成对 ABS 树脂性能的影响。结果发现:NPMI 的引入可以显著提高 ABS 树脂的耐热性能,当 w(NPMI)为10%～20%、m(St)/m(AN)为70:30时,ABS 树脂既具有较高的玻璃化转变温度,又具有较好的力学性能。

水溶性丙烯酸树脂的合成及表征

用于水性油墨的水溶性丙烯酸树脂可以由丙烯酸丁酯 (BA)、甲基丙烯酸甲酯 (MMA)、丙烯酸 (AA) 3种单体采用传统的自由基溶液聚合方式合成 ,通过大量的对比实验 ,获得了最佳合成工艺 ,包括引发剂、溶剂、加料方式、聚合时间和温度。对影响树脂性能的指标如共聚物组成、玻璃化转变温度 (Tg)等因素 ,采用DSC。

透辉石对石英-粘土-长石三组分陶瓷显微结构的影响

以 30 %石英 -4 0 %高岭土 -30 %碱性长石 (质量分数 ,下同 )为基本配方 ,并分别以 10 %和 2 0 %透辉石等量替代碱性长石组成新的配方 ,通过 115 0～ 14 0 0℃烧结实验 ,研究透辉石对于三组分陶瓷烧成体物相、成分和结构的影响。结果表明 :透辉石替代 10 %左右碱性长石可以明显提高坯体的密实度和颗粒配位数 ,有利于烧结过程中坯体的致密化。透辉石的熔融增加了熔体中Ca2 + 和Mg2 + 等网络修饰阳离子的含量 ,减弱了熔体的聚合程度 ,对于斜长石 -透辉石低温共结体系的形成和鳞石英的生长以及气孔排除具有明显促进作用 。

含硅羟基丙烯酸酯乳液的合成

采用单体预乳化方法结合半连续种子乳液聚合工艺,制得了耐水性好和附着力高的含硅羟基丙烯酸酯乳液。考察了乳化剂用量、引发剂用量、羟基单体用量、有机硅单体用量与引入方式对乳液聚合稳定性的影响。结果表明:当w(乳化剂B)为0.90%、w(引发剂)为0.45%、w(HEA)为10%、w(A-151)为5%时,合成的含硅羟基丙烯酸酯乳液的聚合稳定性能最佳。