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1.
The interaction between masonry units and mortar is a crucial factor for the quality of a wall. The most important factor is the adhesion between bricks and mortar in order to construct a masonry wall with adequate strength, good impermeability, and durability. In this work mortars were produced with various cement/lime/aggregates ratio. The adhesion properties of the mortars with clay bricks were tested with a simplified tensile/tear testing measurement. In order to investigate the adhesion properties in relation with microstructure the mortars were characterized with X-ray diffraction and were further investigated with scanning electron microscopy and stereoscopy. It was found that adhesion is favored by the formation of a Si–Al matrix with a low Ca content in the brick/mortar interface and the formation of fine Ca–Al–Si phases which can penetrate into the brick.  相似文献   

2.
In this study, cement mortars were modified with a commercial polymer admixture. The aim of this study is to investigate the influence of the polymer content on the mechanical and adhesion properties of the mortars and to relate these properties with mortars’ microstructure. A series of mortars were produced with various polymer/cement/water/aggregate ratios. The adhesion properties of the mortars to clay bricks were tested with a simplified tensile testing measurement. The microstructure of mortars, as well as interfaces, were evaluated by Scanning Electron Microscopy (SEM). It was found that with high polymer content, large size hardened particles are formed, reducing the compressive strength of the mortars. Polymer addition enhances the adhesion between the mortar and brick. The mortar microstructure at the interface affects the adhesion properties and the mode of failure.  相似文献   

3.
Sensitivity analyses were carried out to assess the behaviour of a fluidized bed wood gasifier simulation model in response to changes in the values of design variables, operating variables, and model coefficients. The model was originally developed using the modified Bubble Assemblage Model. Physical design specifications of the fluidized bed were found to have little influence on the quality of the product gas; in fact the composition of the gas was found to depend almost exclusively on the degree of approach to equilibrium. Overall thermal efficiency could be improved only by increasing the dry wood to oxygen ratio and reducing the moisture content in the wood feed. Because wood gasifiers produce volatiles that greatly enhance the chance of slugging, the influences of the design and operating variables on the occurrence of slugging were also investigated. The onset of slugging was found to be related most strongly to the dynamic bed height.  相似文献   

4.
    
Focusing the adhesive bonding of thermoset carbon fiber reinforced plastics (CFRPs) due to release agent residues on a surface pretreatment prior to the bonding process is inevitable to guarantee sufficient adhesion. Based on different material and process-related phenomena, a huge variety of parameters (e.g. treatment time) influence the treatment effectiveness. This often leads to intense parameter studies in which pretreatment methods are qualified by different mechanical tests and which require significant effort in terms of time and resources. Those qualification procedures are sometimes standardized by different and mostly company-specific standards. To increase the efficiency of this qualification process by increasing the general validity, this paper presents a comparison of different mechanical test methods (namely single lap shear test, floating roller peel test, double cantilever beam (DCB) test, and cross-tension test) in terms of their sensitivity to the detection of adhesion or delamination defects, even if they normally test different aspects of a joint. However, it could be found that the most common test – the single lap shear test – can only reveal large defect levels, while different tests, e.g. DCB test, show a good sensitivity for all investigated failures and others show intermediate performance.  相似文献   

5.
The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly.  相似文献   

6.
    
Joints, which are the most critical part of fibre-reinforced epoxy plastic structures, can be exposed to continuous hydrothermal action. In order to estimate their long-term performance, an accelerated ageing process was performed on adhesively bonded joints of glass-fibre-reinforced epoxy plastics with [0/90/45/?45]s fibre orientations. Changes in the static tensile properties of single lap shear samples due to hot-wet exposure were investigated for one- and two-week immersion periods and at three different water temperatures (50°C, 70°C, and 90°C). Both the ageing temperature and immersion time were found to be influential on load–displacement characteristics, maximum failure loads, and apparent failure modes of joints bonded with Loctite Hysol-9466 epoxy type adhesive. Due to the hydrothermal exposure, maximum failure loads, distance to failure values, and stiffness of joints decreased by a certain amount in proportion to the immersion time and temperature. While unaged samples and those aged at 50°C and 70°C exhibited mainly light fibre-tear (LFT) failures, the samples treated at 90°C ruptured through the material cross section in stock-break (SB) failure mode.  相似文献   

7.
The temperature effect on bending and shear strength of single lap joints, composed by metal–composite substrates with fixed geometry, was evaluated in this paper. The tests provide analysis associated with a system frequently used in the oil and gas industry, characterized by the use of polymeric composite materials with adhesives for repairing and reinforcing pipelines. The results revealed that the tensile behavior of the composite is highly affected by temperature and can be predicted by a linear function with good agreement. The bending stiffness and tensile-shear strength of composite–metal single lap joints are also dependent of the test temperature. The first can be represented by a linear equation and the second by a power law, both with good agreement.  相似文献   

8.
The effect of the surrounding liquid on the strength of the polymer/fibre interface was studied. For this purpose, the shear adhesive strength, τ, between an epoxy composition EDT-10 (based on diglycidyl ether of bisphenol A) and a steel wire of diameter 150 μm was tested by the pull-out technique at 20°C. Loading of the speciments was made in water, ethanol, and in their mixtures of different composition, i.e. in polar liquids with different surface tension γ: (23.5γ72) mN m−1. It was shown from loading the epoxy/steel wire joints in these liquids that their adhesive strength is lower than the adhesive strength of the specimens tested in air. The losses in adhesive strength do not depend on the surface tension of the surrounding liquids under investigation. The possible mechanisms of the strength decrease are discussed.  相似文献   

9.
浅谈土木工程专业普通化学的教学改革   总被引:1,自引:0,他引:1  
本文针对土木工程专业普通化学教学中教学内容和方法手段等方面存在的问题,进行了探讨和研究,提出了改革方案,包括教材内容、教学形式和方法、实验教学、网站建设等四方面的具体措施。  相似文献   

10.
王荣贤 《当代化工》2014,(12):2699-2701
纤维增强塑料筋在土木工程中的使用是目前建筑行业的热点之一,纤维增强塑料筋可以有效克服传统钢筋在使用过程中的面临的腐蚀性。在综合国内外相关资料的基础上对纤维增强塑料筋的使用情况进行研究总结,提出了展望和需进一步解决的问题  相似文献   

11.
    
Glued-in rods are an increasingly used technical solution for numerous structural applications in timber engineering, and demonstrate the potential of adhesively bonded connections. During the insertion process the adhesive fills a very narrow gap over significant anchorage contact area, raising concerns that manufacturing defects may impact the structural performance of the bonded joint, namely the possible lack of adhesion resulting from inadequate preparation of the joint on site. Previous studies on the effect of bonding defects on the capacity of bonded joints identified a nuanced relationship that depends on the ductility of the adhesive.This paper presents experimental evidence that sheds light on the relationship between defects and capacity of glued timber joints. Joints composed of softwood glulam members and mild steel glued-in threaded rods were manufactured with two types of defects likely to be encountered on-site: i) rods placed at an angle inside drill hole instead of aligned with the joint axis, and ii) rod placed against the side of the drill hole instead of fully centered. To establish performance benchmarks a first phase studied the influence of the anchorage length and the rod diameter using three different adhesives. The effect of these defects on joint capacity was investigated with three different adhesives in combination with three different rod anchorage lengths. The investigations demonstrated that joints with sufficient rod anchorage (herein 10 times the rod diameter) do not exhibit a statistically significant loss of capacity, if compared to defect free joints. These results can contribute towards better understanding of the influence that the studied parameters have on the performance on timber joints with glued-in rods, as well as to translate this information to promote the development of further applications.  相似文献   

12.
    
Determining the effect of defects in fiber-reinforced materials, such as polymer matrix composites (PMCs), can be studied by creating artificial flaws in these materials, for example by introducing artificial PTFE foil to induce material delaminations. For fiber-reinforced ceramics (CMCs), this approach is more difficult due to the more complicated production routes of CMCs, which involve several processing steps at elevated temperatures. This work deals with the fabrication and introduction of defined defects in carbon fiber reinforced silicon carbide (C/C-SiC) composites in a way, which allows their detection by non-destructive material testing methods during and after each production step of the composite. It was shown that the defects produced using boron nitride (BN) and alumina fiber roving were stable over the entire manufacturing process and could be detected by ultrasound and x-ray tomography techniques. To determine any possible effects, an initial sampling of bending samples with artificial defects was manufactured, tested and compared with defect-free reference materials. These tests showed a lower bending strength and failure strain for the defect samples compared to samples without defects.  相似文献   

13.
In this study, the surface of ultra-high-molecular-weight-polyethylene (UHMWPE) fibers was modified by ozone pretreatment, followed by ultraviolet (UV) grafting, to enhance the interfacial properties of UHMWPE fibers/rubber composites. The fibers were first pretreated by ozone to introduce oxygen-functional groups. The graft polymerization of glycidyl methacrylate (GMA) onto the ozone-treated fibers was implemented by UV irradiation. The effects of time and GMA concentration on the grafting efficiency were investigated. The modified fibers were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The XPS and FTIR results revealed that GMA was successfully grafted onto the fibers with epoxy groups. SEM images confirmed that a continuous layer of poly-(GMA) (PGMA) was grafted onto the fibers. The interfacial adhesion force of UHMWPE fibers with rubber matrix was characterized by H pullout testing, which showed that the maximum force the fibers/rubber composites increased by 79% over that of the untreated fibers.  相似文献   

14.
The purpose of this study was to investigate the effects of titania addition on adhesion strength of silver colloids to glass substrate. Our results indicated that when the pH was adjusted to 10, the mixed slurry of titania and silver colloids was stable with no sign of settling at approximately 4 hr. After film deposition by doctor blade method and subsequent sintering treatment, the adhesion strength between silver film and glass substrate was measured by both ASTM D3359 and D4541 standards. The results showed positive correlation of adhesion strength to both the titania concentration and sintering temperature. The adhesion strength reached 7.0 MPa when we added 8 wt% titania (based on silver) and sintered the film at 320°C for 20 min. X-ray photoelectron spectroscopy data revealed that interdiffusion of Ti into both glass substrate and silver colloid might be responsible for adhesion enhancement. On the other hand, the electrical resistivity of films increased with titania addition. This fact implied that we need to compromise between these two properties when titania addition was used to improve adhesion between silver colloid and glass substrate. An empirical model was subsequently proposed to simulate the compromise between adhesion strength and electrical resistivity.  相似文献   

15.
Defining anchor lengths of steel and CFRP plates bonded to concrete   总被引:8,自引:0,他引:8  
At Luleå University of Technology, research is taking place in the area of plate bonding, i.e. when concrete members are strengthened by bonding steel or fibre-reinforced plastic (FRP) plates to their surface. The research work started in 1988. Both comprehensive experimental work and theoretical work have been performed. This paper presents the results of tests performed on concrete prisms onto which steel or carbon-fibre-reinforced plastic (CFRP) plates have been bonded. The criteria for the necessary anchor lengths for both the materials are presented as well as the critical strain level in the concrete at failure. Tests are compared with the Volkerson theory for lap joints. The results from the tests show that there is a specific anchor length for each material used. The tests also show that the strain limit in the concrete is the governing factor for failure. Furthermore, a compression between test and theory shows that the derived elastic theory can be used for moderate levels of load.  相似文献   

16.
    
A special unilateral NMR sensor has been designed for investigations of thin samples with a thickness of less than 1 mm and of surface effects of polymers. For use with the bar‐magnet NMR‐MOUSE®, the so‐called “crazy coil” is introduced with a low penetration depth. It is a flat meander coil etched on a printed circuit board with wiggles in the conductors. The design of the new coil and FEM simulations of the B 1 field are presented. Different applications are discussed by means of illustrative examples. They are the detection of surface damage in rubber samples, the swelling and drying of a latex membrane exposed to cyclohexane vapor mimicking a chemical sensor, and the drying of a thin sprayed adhesive layer.

Bar‐magnet NMR‐MOUSE® with crazy coil.  相似文献   


17.
冯莉  赵春雁 《中国塑料》2016,30(3):73-77
以聚乙烯(PE)基木塑复合材料为研究对象,利用弯曲振动法和纵向振动法对PE基木塑复合材料进行了动态弹性模量的检测。研究了木塑比与偶联剂等主要因素对动态弹性模量的影响规律。对比了加工因素对密度和动态弹性模量影响的关系曲线,并进行了加工因素和密度对动态弹性模量的相关性分析。结果表明,木塑比是影响动态弹性模量的首要因素;在木塑比55:45~70:30的范围内,PE基木塑复合材料的动态弹性模量与木塑比成正比关系;偶联剂含量为2 %~5 %时,随着偶联剂含量的增加,PE基木塑复合材料的动态弹性模量也随之升高;利用成型温度、偶联剂含量和密度对PE基木塑复合材料的动态弹性模量进行预测是可行的。  相似文献   

18.
This work proposes a methodology utilizing functional unfold principal component regression (FUPCR), for application to industrial batch process data as a process modeling and optimization tool. The methodology is applied to an industrial fermentation dataset, containing 30 batches of a production process operating at Novozymes A/S. Following the FUPCR methodology, the final product concentration could be predicted with an average prediction error of 7.4%. Multiple iterations of preprocessing were applied by implementing the methodology to identify the best data handling methods for the model. It is shown that application of functional data analysis and the choice of variance scaling method have the greatest impact on the prediction accuracy. Considering the vast amount of batch process data continuously generated in industry, this methodology can potentially contribute as a tool to identify desirable process operating conditions from complex industrial datasets. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1986–1994, 2016  相似文献   

19.
葛自力 《当代化工》2015,(1):117-119
碳纤维复合材料是随着纤维增强材料的一个重要组成部分,碳纤维复合材料对于结构补强加固十分有效,其施工质量高,施工效率高,加固效果和综合效益好,具有轻质高强、可设计性强的特点。因此,对碳纤维复合材料的研究和探索,一直是土木工程中关注的重点内容。  相似文献   

20.
    
This paper presents a Bayesian methodology for computer‐aided experimental design for hydrogen peroxide formulations. Hydrogen peroxide is one of the oldest known active antimicrobial chemicals and is used in many cleaning/disinfecting formulations. It is favourable as an active antimicrobial in that it degrades only to water and oxygen, and does not contaminate the environment. However hydrogen peroxide is difficult to stabilise, and disinfecting products based on it soon lose their antimicrobial activity. Moreover, regulatory agencies such as U.S. Environmental Protection Agency (EPA) and Health Canada require that disinfecting products do not lose more than 5–10% of their active concentration throughout their shelf life. Therefore, it is very important while formulating hydrogen peroxide‐based products to test for their stability. An effective way to improve hydrogen peroxide stability in a solution is to use stabilisers. It is desired to use these chemicals in as low concentrations as possible for environmental and economic considerations. On the other hand, due to tight market competition, the new products need to be formulated as quickly as possible, and therefore there is limited time to ensure product stability. In this paper, prior information has been used in the form of a model, based on historical experiments. A Bayesian D‐optimality criterion is used to design a few additional experiments so that the resulting model can have an acceptable prediction power. It is shown that a design which uses the Bayesian D‐optimality criterion taking advantage of prior information can be more efficient than even a resolution IV fractional factorial design in the sense that using fewer trials gives a model with equivalent prediction capability. This can be critical where experiments are expensive to perform.  相似文献   

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