应变硬化水泥基复合材料单轴拉伸性能及其温度影响规律研究

发布时间：2018-05-26 04:39

本文选题：应变硬化水泥基复合材料 + 单轴拉伸　；参考：《青岛理工大学》2013年硕士论文

【摘要】：在应变硬化水泥基复合材料（Strain Hardening Cement-based Composite,SHCC）的研究过程中，学者们发现单轴拉伸试验是检验SHCC能否表现出准应变硬化特性最直接可靠的方法，某些纤维材料在弯曲或其他力的作用下能够出现应变硬化现象，但在单轴拉伸作用力下仍表现出了应变软化，，而且单轴拉伸应力应变曲线是SHCC的特征曲线。基于这一基础，本文针对应变硬化水泥基复合材料在不同的原材料选择、不同配比、不同龄期以及不同高温、冻融损伤下的单轴拉伸性能进行了试验研究；同时对SHCC在不同条件下的裂缝控制能力这一新课题展开了深入的研究，主要内容如下：（1）SHCC材料中掺入粉煤灰可以有效改善纤维与基体接触面的特性，减弱纤维与基体间的界面黏结力，进而在一定范围内增强了SHCC的应变硬化特性。本文选择了I级、II级粉煤灰两组对比材料，并对SHCC单轴拉伸性能的影响进行了测定。研究结果发现无论是从强度上还是从应变硬化性能上，I级粉煤灰都比II级粉煤灰要好很多。（2）从所用细骨料来看，除了少数人选用的是普通河砂之外，多数科研团队还是参考国外选用了石英砂。所以砂子不同种类、粒径对SHCC单轴拉伸性能的影响是目前需要研究的问题。通过对普通河砂、不同粒径石英砂对SHCC单轴拉伸性能及裂缝宽度的影响进行了深入的研究。结果表明石英砂无论是在提高强度上还是在控制裂缝能力上都优于普通河砂，而且石英砂粒径越小这一效果越明显。（3）硅灰的掺入可以有效提高SHCC材料的强度，但对其应变硬化特性及裂缝控制能力的影响是需要研究的课题。通过对不同硅灰掺量的三组试件进行单轴拉伸试验及不同应变下的裂缝开展情况进行观测并运用image pro-plus软件进行数据分析处理。结果表明，硅灰的掺入可以大大提高材料的拉伸强度，且对材料的应变能力影响不大，但对材料的裂缝控制能力产生了较大的负面影响。在工程实际应用中可根据结构对裂缝控制能力或强度的要求对材料配比进行选择。（4）通过试验研究了SHCC（最大粒径为0.3mm石英砂配比）在3d、7d、14d、28d四个龄期下单轴拉伸性能。结果表明，SHCC试件的初裂强度随龄期的延长逐渐增大，而其韧性受强度的影响随龄期延长逐渐减小。（5）高温作用可以促进基体中的各项水化反应，使得试件的强度显著提高，但高温对材料的应变硬化性能及裂缝控制能力有何影响是本课题需要研究的内容。通过对不同配比的三组试件在高温（20-200℃范围内多个温度）损伤下的单轴拉伸性能进行了研究，结果表明石英砂配比材料对温度的敏感性较强，随着温度的升高初裂强度大幅度上升。而另外两组配比试件在高温作用下应力、应变的变化与上组试件的变化趋势基本相同，但幅度有所减小。通过对石英砂组试件在20℃、50℃、80℃、100℃四个温度在不同应变状态下的裂缝控制情况进行了研究，结果表明四个温度下的试件在极限状态下其平均裂缝宽度仍能够控制在80μm以内。（6）研究了SHCC（细骨料为最大粒径0.3mm的石普通河砂）试件在0、50、100、150、200、300次冻融循环损伤之后的单轴拉伸性能，结果表明在拉伸强度稍有降低的情况下，材料仍保持了良好的韧性。
[Abstract]:In the research process of strain hardening cement-based composites (Strain Hardening Cement-based Composite, SHCC), the uniaxial tensile test has been found to be the most direct and reliable method to test whether SHCC can show quasi strain hardening characteristics. Some fiber materials can appear strain hardening under the action of bending or other forces. The strain softening is still shown under the axial tensile force, and the stress-strain curve of the uniaxial tensile stress is the characteristic curve of SHCC. Based on this basis, the uniaxial tensile properties of strain hardening cement-based composites under different raw material selection, different proportions, different ages and different temperatures and freezing thawing damage have been tested in this paper. At the same time, the new topic of crack control capacity of SHCC under different conditions has been studied in depth. The main contents are as follows:
(1) the addition of fly ash in SHCC material can effectively improve the properties of the contact surface of fiber and matrix, weaken the interfacial bonding force between the fiber and the matrix, and then enhance the strain hardening characteristic of SHCC in a certain range. This paper selects two groups of contrast materials of I grade and II grade fly ash, and studies the influence of the uniaxial tensile properties of SHCC. The results show that I grade fly ash is better than II grade fly ash in terms of strength and strain hardening properties.
(2) in terms of the fine aggregate used, most research teams have chosen quartz sand in addition to ordinary river sand. Therefore, the influence of different kinds of sand and particle size on the uniaxial tensile properties of SHCC is the problem that needs to be studied at present. Through the common river sand, the tensile properties and cracking of different particle sizes of quartz sand on the SHCC uniaxial tensile properties The effect of the width of the seams has been studied in depth. The results show that the quartz sand is better than the ordinary river sand in both the strength and the control of the crack ability, and the smaller the quartz sand particle size, the more obvious the effect.
(3) the addition of silica fume can effectively improve the strength of SHCC material, but the influence on the strain hardening characteristic and the crack control ability is a subject that needs to be studied. Through the uniaxial tensile test and the crack development under different strain, three groups of different silica fume content are observed and the data are divided by the image Pro-Plus software. The results show that the addition of silica fume can greatly improve the tensile strength of the material, and it has little effect on the strain capacity of the material, but has a great negative effect on the crack control ability of the material. In the practical application of the engineering, the material ratio can be selected according to the requirement of the crack control ability or the strength of the structure.
(4) the uniaxial tensile properties of SHCC (the ratio of maximum particle size of 0.3mm quartz sand) at the four ages of 3D, 7d, 14d and 28d were studied by experiments. The results showed that the initial crack strength of SHCC specimens gradually increased with the prolongation of the age, and the influence of strength on the tenacity gradually decreased with the prolongation of the age.
(5) the effect of high temperature can promote the hydration reaction in the matrix, which makes the strength of the specimen greatly improved, but what is the influence of the high temperature on the strain hardening property and the crack control ability of the material is the subject needed to be studied in this subject. Through the uniaxial tension of three groups of specimens with different proportions at high temperature (20-200 degrees centigrade temperature range) The results show that the material of quartz sand ratio is more sensitive to temperature, and the initial crack strength increases with the increase of temperature. The change of the strain in the other two groups is basically the same as that of the upper group, but the amplitude is reduced. The sample of quartz sand group is at 20 C through the quartz sand group. The crack control of 50 C, 80 and 100 C under different strain states is studied. The results show that the average crack width of the specimens at the four temperatures is still less than 80 m under the limit state.
(6) the uniaxial tensile properties of SHCC (the stone ordinary river sand with the maximum particle size of 0.3mm) after the 0,50100150200300 freezing and thawing cycle damage have been studied. The results show that the material still maintains good toughness when the tensile strength is slightly reduced.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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