水泥基次轻高强复合材料力学性能及应用研究

针对某高抗力防护设施需要,研发了水泥基次轻高强复合材料,并采用XRD、SEM分析了复合材料的成分、养护与微观结构关系。结果表明,随着胶凝材料中粉煤灰掺量的增加,复合材料的力学性能提高;对于有活性掺合料的复合材料,蒸汽养护能明显提高材料的强度;钢纤维的掺入起到了很好的阻裂效应,改善了高强复合材料的抗压性能和材料脆性,改变了破坏时的形态。采用该复合材料的受弯构件充分发挥了钢和高强水泥基材料的受力性能优势,达到了良好的组合效果,在减轻自重的同时,承载力还高出设计荷载约19%。

高强高韧水泥基复合材料的配合比优化及微观结构破坏机理

文章基于正交试验法,以硅灰、粉煤灰、钢纤维和水胶比为参数,设计并制备了四因素、三水平的水泥基复合材料。通过抗压和抗折力学性能试验,分析了四因素对水泥基复合材料力学性能的影响。另外,通过扫描电镜及X-CT试验,从微观表征解释了高强度和高韧性的形成机理。结果表明,钢纤维掺量对抗压强度的影响最大,最佳掺量为1.8%;当粉煤灰与水泥比由0.48增至0.52时,抗压和抗折强度下降幅度很大;随着水化反应的进程,28 d龄期的水泥基复合材料孔隙微观结构比7 d龄期的更致密,且钢纤维在基体微裂缝中起到了桥连作用,提升了水泥基复合材料的抗压和抗折强度。

高强高模聚乙烯复合材料超高速碰撞实验研究

高强高模聚乙烯(UHIMPE)复合材料具有许多优异性能,在航空航天领域有着广泛的应用前景。利用二级轻气炮,开展了UHIMPE复合材料Whipple防护结构超高速碰撞实验,并与相同面密度的硬铝2A12进行了对比,对前板开孔和后板破坏情况进行了测量和观察。根据实验结果定性分析了UHIMPE复合材料防护结构弹道极限曲线的走向。实验结果表明,UHIMPE复合材料不能更有效地破碎弹丸,有着比硬铝2A12更差的防护性能。

高强度高延性水泥基复合材料的弯曲性能

高强度高延性水泥基复合材料(HSHDCC)由于具有超高强度和超高延性等优异的力学性能,近年来在建筑结构抗震加固和修复领域得到了广泛的关注。但是,HSHDCC的高成本是其大规模工程化应用的瓶颈之一。通过引入高强度高弹性模量低成本的碳酸钙晶须,制备了新型的HSHDCC材料,研究了水胶比和碳酸钙晶须对HSHDCC弯曲性能的影响。研究发现,HSHDCC的抗弯强度随水胶比的增大而降低,但其延性随水胶比的增大而提高,HSHDCC的弯曲裂缝随水胶比的增大而逐渐饱和。引入碳酸钙晶须改善了HSHDCC的抗弯性能,碳酸钙晶须通过晶须拔出、裂纹偏转和裂纹桥联等微观作用机制产生更多的微裂源,提高裂缝的稳定扩展能力,从而改善HSHDCC的多缝开裂能力和弯曲挠度硬化行为,HSHDCC的延性得到了显著提升。

高强柔性复合材料平板圆柱模板施工技术

传统的用于圆柱定型的钢模板体系、木模板、玻璃钢筒模模板体系多具有拼缝多、造价高等不足,给模板施工带来了难题。为此,以广州星河湾六期工程采用柔性复合材料平板圆柱模板技术进行施工为例,介绍了该模板具有接缝少、成本低及采用其施工应用的混凝土圆柱光洁度高等的优点。实践证明,采用该施工技术的混凝土成型质量较好,取得了较好的社会效益和经济效益。

烧结温度对碳化钨/高强钢复合材料界面微观组织和元素扩散的影响

利用"冷压成型-真空烧结法"制备了碳化钨/高强钢复合材料。结合光学显微镜、扫描电镜和显微硬度计等分析测试技术对不同烧结温度下获得的复合材料以及界面的显微组织和硬度进行了分析。实验结果表明,烧结温度高于1 300℃时,碳化钨/高强钢复合界面存在明显的过渡层,且Fe、Co、Cr元素发生了明显的扩散,W元素在1 340℃时有微量扩散;随着烧结温度的升高,WC孔隙逐渐减少并趋于致密化;同时WC晶粒尺寸逐渐变大,且WC晶粒形状逐渐规则化。烧结温度为1 300和1 320℃时,WC晶粒尺寸均匀; WC的硬度随着烧结温度的升高而呈增大趋势,烧结温度为1 340℃时WC的硬度达到1 575 Hv_(0.1);在靠近结合界面处WC硬度明显高于碳化钨基体;在不同温度下,心部的高速钢材料硬度都在500 Hv_(0.1)左右。

光固化高强玻璃纤维复合材料管道补强技术研究

为了有效控制管道施工质量,提高施工效率,针对国内复合材料修复普遍采用的湿缠绕法存在的现场质量管控困难、效率低、易受污染、环境影响大等缺点,开发了一种光固化高强纤维复合材料预浸料,并对该预浸料的拉伸强度、拉伸模量、吸水性、剥离强度、微观形貌以及修复能力进行了试验研究。研究结果表明,光固化高强纤维复合材料预浸料各项性能优异,明显高于湿缠绕法的同等试样水平;光固化高强纤维复合材料预浸料的显微结构更加紧凑,树脂对纤维的浸润效果更好。此外,修复结构的水压试验表明,该纤维复合材料的修复作用是通过缺陷塑性变形实现应力传递的,且纤维复合材料修复结构的变形由内到外逐渐减弱。

高强聚氨酯复合材料加固混凝土梁抗弯性能研究

为研究高强聚氨酯复合材料(HSPUC)加固混凝土梁抗弯性能,开展了2根采用不同梁底加固范围的HSPUC加固混凝土梁和1根对比混凝土梁的静力破坏试验,分析了试验梁破坏形态、承载能力、裂缝特征、变形及应变发展规律和界面滑移性能。采用ABAQUS有限元软件建立了HSPUC加固混凝土梁抗弯性能精细化数值模型,分析了加固层抗折强度和加固层厚度对抗弯性能影响。研究结果表明:采用梁底非通长HSPUC加固试验梁和采用梁底通长HSPUC加固试验梁分别发生了加固端保护层剥离破坏和塑性弯曲破坏,极限承载力较未加固试验梁分别提高了30.4%、79.4%;HSPUC加固法充分发挥了HSPUC材料的高强力学性能,延缓了裂缝的发展,有效抑制了混凝土梁因裂缝扩展而引起的刚度下降,对混凝土梁抗弯刚度和极限承载力的提高作用显著;各加固梁试验过程中HSPUC层与混凝土梁间具有可靠的黏结强度和良好的协同工作性能;数值模型计算荷载–跨中挠度曲线与试验曲线吻合良好,可用于HSPUC加固混凝土梁受弯全过程计算分析。

S_2/TDE85复合材料耐自然库存与加速湿热老化的性能研究

本文对高强 2号玻璃纤维 (S2 )增强环氧 (TDE85 -MCD体系 )基复合材料单向板经自然库存与加速湿热老化后力学性能的变化进行了研究。研究结果表明 ,温度和湿度的作用会使单向板的拉伸、弯曲、剪切性能有所降低 ;温度越高、湿度越大 ,力学性能变化越大 ;可用加速湿热试验值来表征自然库存条件下的试验值。

结构间隙对夹芯式复合装甲结构抗侵彻性能的影响

采用由厚度为8 mm的前置钛合金板、面密度为60 kg/m2的高强聚乙烯纤维增强复合材料层合板抗弹芯层、厚度为8 mm的后置钢板构成的夹芯式复合装甲,模拟舰船舷侧复合夹芯舱壁结构。根据面板与芯层间是否设置20 mm的间隙,将复合装甲结构定义为无间隙式、后间隙式及前后间隙式。为研究以上3种结构在55 g圆柱体弹高速冲击下的抗弹性能及破坏机理,开展了系列弹道实验,分析了钛合金板、高强聚乙烯纤维增强复合材料层合板芯层及钢质面板的破坏模式,探讨了结构间隙对复合装甲结构抗弹性能的影响。结果表明:前置钛合金板的破坏模式为剪切冲塞,靶板背弹面产生脆性断裂并伴随碎块崩落现象;聚乙烯纤维增强复合材料板的破坏模式及钢质背板的变形范围受间隙的影响较大,前置钛合金板受间隙影响较小;相同载荷侵彻下,间隙的存在有利于提高复合装甲结构的抗弹性能。

高强不锈钢绞线网增强工程水泥基复合材料受拉应力-应变关系

为了研究高强不锈钢绞线网增强工程水泥基复合材料(Engineered cementitious composites,EEC)的受拉性能,考虑高强不锈钢绞线配筋率、ECC抗拉强度、高强不锈钢绞线网增强ECC试件宽度3个影响因素,对设计的27个高强不锈钢绞线网增强ECC试件进行了单轴拉伸试验。试验结果表明,高强不锈钢绞线网增强ECC受拉试件的开裂应力和极限应力随着钢绞线配筋率、ECC抗拉强度的增大而增大;增大试件宽度对试件的开裂应力和极限应力几乎无影响。基于试验结果,提出并建立了高强不锈钢绞线网增强ECC受拉本构模型,推导了开裂应力和极限应力计算公式。经验证,计算结果与试验结果吻合良好,说明所建立的受拉本构模型可准确描述高强不锈钢绞线网增强ECC的受拉应力-应变关系。

Research on High-Velocity Impact Damage Monitoring Method of CFRP Based on Guided Wave

Carbon fiber-reinforced polymer(CFRP)is widely used in aerospace applications.This kind of material may face the threat of high-velocity impact in the process of dedicated service,and the relevant research mainly considers the impact resistance of the material,and lacks the high-velocity impact damage monitoring research of CFRP.To solve this problem,a real high-velocity impact damage experiment and structural health monitoring(SHM)method of CFRP plate based on piezoelectric guided wave is proposed.The results show that CFRP has obvious perforation damage and fiber breakage when high-velocity impact occurs.It is also proved that guided wave SHM technology can be effectively used in the monitoring of such damage,and the damage can be reflected by quantifying the signal changes and damage index(DI).It provides a reference for further research on guided wave structure monitoring of high/hyper-velocity impact damage of CFRP.

新能源汽车车身材料特性及发展现状浅谈

随着能源枯竭,环境污染日趋严重化,给国际汽车工业变更面提出了新的挑战。能源的枯竭带动了新能源的迅速发展,但是新能源发展给整车的重量提出了一个新的挑战,一些新生材料的应用起到了关键性的作用。研究表明,一般汽车每减轻1kg的重量,1L的汽油可使汽车多行驶约1m。车身在整车中占约25%左右的重量,所以车身的材料对整车的重量减轻起着关键性的作用。

关于储油罐维修若干问题的探讨

总结了塔7站储油罐维修的经验和方法。针对固定顶式储罐罐顶板严重腐蚀、罐壁板整体腐蚀不大的情况,提出整体更换和内胆补强2种基本解决方案。针对固定顶式储罐罐顶无环向巡检通道、罐底边缘板防腐防水不足及外浮顶油罐转动浮梯导轮防静电和火花等问题进行了探讨分析,给出了相应的优化改进或补救方法。这些方法已在现场实施,效果良好,对解决类似问题具有一定的借鉴作用。

非金属双层地下油罐在加油站中的推广运用

随着社会的发展进步,人们对环保越来越重视,积极引进国外环保方面的新技术、新产品,来改善和提高我国的各行各业,特别是存在较大潜在污染威胁的危险行业的安全环保水平,已经成为一种发展趋势。文章重点介绍非金属油罐的基本情况,高强复合材料双层地下油罐的技术特点及在加油站中的推广运用。

Experimental and numerical study on flexural behaviors of steel reinforced engineered cementitious composite beams

To investigate the flexural behaviors of steel reinforced engineered cementitious composite （ECC） beams, the behaviors of the steel reinforced ECC beam and the conventional steel reinforced concrete beam subjected to flexural load are experimentally compared. The experimental results show that the flexural strength and ductility of the steel reinforced ECC beam are 24.8% and 187.67% times larger than those of the steel reinforced concrete beam, and the substitution of concrete with ECC can significantly delay the propagation of cracks. Additionally, a simplified constitutive model of the ECC material is used to simulate the flexural behaviors of beams by the finite element analysis （FEA）. The results show a good agreement between the simulation and test results. The crack width of the steel reinforced ECC beam can be limited to 0.4 mm under the service load conditions. The application of ductile ECC can significantly increase the flexural performance in terms of flexural strength, deformation capacity and ductility of the beams.

SRP加固预制节段拼装桥墩在车辆撞击下的动态响应

为了减轻车辆对预制节段拼装桥墩的撞击作用,采用高强钢丝织物复合材料(Steel Reinforced Polymer,SRP)加固预制节段拼装桥墩并进行数值模拟与分析。使用LS-DYNA建立预制节段拼装桥墩受冲击的数值模型,并与已有实验数据对比,验证了该数值模拟方法的准确性。在相同车辆撞击条件下,对比分析了RC墩与SRP加固墩撞击力时程曲线、侧向位移和墩身损坏情况。以SRP加固位置、SRP包裹层数和初始预应力水平为变量,研究其对车辆-桥墩接触面撞击力和桥墩变形的影响规律。研究结果表明:采用SRP对预制节段拼装桥墩进行合理加固,可以有效减小接触面撞击力、墩身位移和桥墩损伤;在桥墩底部及接缝处采用SRP加固对墩身具有更好的保护作用;SRP包裹层数由1层增加到3层可以更好地限制墩身位移变形。

Influence of different curing regimes on the microstructure and macro performance of UHPFRCC

This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP）. The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.

Seismic behaviors of steel reinforced ECC/RC composite columns under low-cyclic loading

To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.

Flexural behavior of steel reinforced engineered cementitious composite beams

In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretical analyses of the SRECC beam including crack propagation and stress-strain distributions along the depth of the composite beam in different loading stages are conducted. A theoretical model and simplified design method are proposed to calculate the load carrying capacity. Based on the proposed theoretical model, the relationship between the moment and corresponding curvature is derived. The theoretical results are verified with the finite element analysis. Finally, an extensive parametric study is performed to study the effect of the matrix type, steel shape ratio, reinforced bar ratio, ECC compressive strength and ECC tensile ductility on the mechanical behavior of SRECC beams. The results show that substitution concrete with ECC can effectively improve the bearing capacity and ductility of composite beams. The steel shape and longitudinal reinforcement can enhance the loading carrying capacity, while the ductility decreases with the increase of steel shape ratio. ECC compressive strength has significant effects on both load carrying capacity and ductility, and changing the ultimate strain of ECC results in a very limited variation in the mechanical behavior of SRECC beams.