高强度易拆胶的光学用胶粘剂的研制

透明型光学用胶粘剂可用作透明光学材料如光学镜头的粘接。它应具有良好的光学性能，粘接强度高并且容易拆胶返修不合格粘合件。目前市场上光学胶品种很多，也基本上能满足使用要求；但高粘接强度和易拆胶性这两个方面一致难以同时满足。国内光学仪器厂有的采用很麻烦的拆胶方法，有的使用进口胶种，有的对难拆开的元件只好忍痛丢弃，造成浪费。为获得能满足上述要求的胶粘剂，我们选定以不饱和聚酯树脂为主体来制备。因为该体系树脂具有粘度低、光学性能好、固化速度易调节且有较高的粘接力等特点。但通用型不饱和聚酯树脂性脆易裂，柔韧性…     

胶层尺寸对单搭胶接接头性能的影响研究

针对汽车车身中应用日益广泛的钢板胶接结构,通过试验得到了不同胶层尺寸对胶接接头承载能力的影响规律,建立了钢板单搭接头的三维弹塑性有限元模型,分析了胶层尺寸对胶接接头应力分布的影响.研究结果表明:随着胶层厚度的增加,胶接件的承载能力呈先升后降的趋势,合理的胶层厚度应为0.3-0.5 mm;无论胶层厚度为多少,增加搭接区域胶层的长度或宽度.均会提高胶接件的承载能力.     

J-133胶黏剂铝合金胶接接头湿热老化性能的研究

选取J-133环氧结构胶黏剂,制备铝合金胶接接头。通过在湿热条件下对试样进行环境试验,对结构胶黏剂和胶接接头的耐久性进行了评价。采用TG、IR和光学显微镜分别对胶黏剂样品变化和胶接接头破坏面形貌进行分析。分析结果表明:该胶黏剂在55℃和80℃,2200h湿热老化后剪切强度下降分别超过5%和7%;胶黏剂热失重峰温度下降,发生了断链分解;断链反应发生在固化生成的新官能团部位;胶接界面层和胶黏剂层都受到了水分的影响。     

飞机发动机导管的胶接增强研究

介绍了用于不锈钢管增强的SY-ZQ增强带的力学性能及加速老化性能、胶接工艺和典型件的疲劳性能。试验结果表明SY-ZQ增强带的综合性能良好，胶接工艺新颖可靠，能够提高导管部件的疲劳寿命10倍以上。     

钛合金‑芳纶纤维复合材料单搭接胶接接头渐进破坏分析

采用芳纶纤维复合材料与钛合金制备单搭接胶接连接实验件。利用万能实验机、DIC、应变采集系统等手段，对胶接接头的极限载荷、应变场、应变分布和破坏模式进行表征，分析了拉伸载荷下胶接接头的应变分布规律和复合材料层合板刚度折减规律，探究了异质材料单搭接胶接接头的破坏过程。结果表明，胶接接头破坏模式为搭接接头两端胶层界面破坏，中间部位复合材料层间破坏。接头破坏过程为渐进破坏，受载时复合材料端头产生较大的剪切应变，裂纹在此处萌生，并不断向钛合金端头扩展，扩展部位复合材料层合板刚度不断折减，直到搭接面积过小胶层突然发生界面破坏。     

环境友好型底胶的研究进展

在航空工业中的胶接领域,为了降低底胶中含有的大量挥发性有机溶剂（VOC）和铬酸盐,促进了环保型底胶的研发。对于水基底胶、无机底胶以及不合铬酸盐的底胶的胶接耐久性试验表明,一些新型的环保型底胶的性能与传统的溶剂型底胶处于同一水平甚至更好。新型底胶也同样能够提高复合材料的胶接强度和耐久性能,但应该寻找更环保、更简便的方法来获得耐久性的胶接。磷酸阳极化作为铝合金胶接中最好的表面处理方法本身具有很好的耐久性,使用耐久性较好胶粘剂获得耐久胶接是较好的方案之一。     

复材/复材二次胶接胶接质量及强度影响因素研究

通过不同尺寸的高温结构胶-双马基碳纤维层压板的二次胶接试验,对二次胶接过程中影响胶接内部质量和胶接强度的因素进行了分析。结果表明,在胶接反应过程中,复材板与复材板之间的实际配合间隙大于复材板制造的叠合公差,准确测量配合间隙及适当进行胶膜补充是提高胶接质量的重要保障,通过模拟胶接过程来测量配合间隙可行。对大尺寸胶接界面,通过提高胶膜的流动性能够提高胶接质量,但却降低了胶接强度。胶接强度随胶膜厚度增加而增加,但达到极值后随胶层厚度的增加而减小。     

碳纤维传动轴胶接胶层应力均匀化分析

碳纤维传动轴胶接联接在传递载荷时,会出现端部胶层应力大、中间应力小的现象,这种现象会使胶接接头的胶层首先从端部破坏,影响联接性能。从应变角度阐述胶接胶层应力曲线规律,说明了影响胶层应力分布的因素有胶层内、外周向变形量和胶层厚度,提出几种胶接胶层应力均匀化方法,并用有限元分析方法进行了验证。结果表明:(1)增加胶层厚度可以使胶层应力均匀化,但均匀化程度不明显,且在工程中会增加胶层缺陷;(2)采用变胶层厚度的鼓形结构胶接能够使胶层应力均匀化明显,最后指出影响鼓形胶接胶层应力均匀化的因素有变厚度胶层长度L、胶层的最大厚度H。     

磷化处理对金属胶接接头拉剪强度的影响

以结构钢为研究对象，对常用磷化液的各主要成份对胶接接头拉剪强度的影响进行了研究并进行了优化，结果指出，采用本文的磷化液对被粘件进行表面处理，可使胶接接头的拉剪强度在现有常规处理工艺的基础上得到一定程度的提高。     

复合材料胶接（下）

三、胶接接头设计1．胶接接头设计的基本原则归纳起来，胶接接头设计的基本原则有：（a）力求胶层受力均匀，避免或减小应力集中；（b）尽可能使胶层承受剪切力和拉伸压缩力，避免避裂力和剥离力；（c）合理地增大度接面积，提高接头的承载能力；（d）避免冲击载荷；（e）对层状制品的胶接要防止层间剥离；（f）应选择线热膨胀系数与复合材料一致的胶粘剂，或加一定填料改性；（g）应综合考虑接头的工艺性、经济性和环境影响，适当采用胶一铆，胶一焊和胶一螺栓等混合胶接形式。2．胶粘接接头的结构形式接头的结构形式有多种多样，以被粘物…     

Nonlinear Analysis of theTorque Transmission Capability of Adhesively Bonded Tubular Lap Joints

Calculated torque transmission capability of adhesively bonded tubular lap joints using linear elastic material properties is usually much less than the experimentally-determined one because the majority of the load transfer of the adhesively bonded joints is accomplished by the nonlinear behavior of rubber-toughened epoxy adhesives.

Although the adhesively bonded tubular double lap joint has better torque transmission capability and reliability than the single lap joint, the nonlinear analytic or numerical analysis for the adhesively bonded tubular double lap joint has not been performed because of numerical complications.

An iterative solution that includes the nonlinear shear behavior of the adhesive was derived using the analytic solution. Since the iterative solution can be obtained very quickly due to the simplicity of the algorithm, it is an attractive method of designing adhesively bonded tubular single and double lap joints.     

Piezoelectric monitoring of the reliability of adhesive joints

Since the reliability of adhesively bonded joints for composite structures is dependent on many parameters such as the shape and dimensions of joints, type of applied load, and environment, so an accurate estimation of the fatigue life of adhesively bonded joints is seldom possible, which necessitates an in-situ reliability monitoring of the joints during the operation of structures. In this study, a self-sensor method for adhesively bonded joints was devised, in which the adhesive used works as a piezoelectric material to send changing signals depending on the integrity of the joint. In order to validate the method, the piezoelectric properties of the adhesive were measured during the fatigue test. Electrically conducting adherends were used as electrodes without embedded sensors, and the adhesively bonded joint was modeled as the equivalent parallel circuit composed of electric charge and capacitance. From the investigation, it was found that the electric charge increased gradually as cracks initiated and propagated in the adhesive layer, and had its maximum value when the adhesively bonded joint failed. So it is feasible to monitor the integrity of the joint during its lifetime. Finally, a relationship between the piezoelectric property of the adhesive and crack propagation was obtained from the experimental results.     

Improvement in Strength of Adhesively Bonded Single-Lap Joints Using Reinforcements

In order to enhance the strength of adhesively bonded single-lap joints (SLJs), the adhesively bonded SLJs with reinforcements were proposed. Adhesively bonded SLJs of different substrates and with different reinforcements were investigated experimentally and numerically. Scanning electron microscopy was performed on the fracture surfaces of the joints to analyze the failure mechanism. Shear stresses and peeling stresses of the adhesive layer were calculated with finite element analyses (FEA). Results showed that the deformation of the joints decreased with an increase in stiffness at the end of the overlap region. The strength increase in adhesively bonded SLJs with reinforcements was validated by the results from experimental tests and FEA.     

Metal alkoxide primers in the adhesive bonding of mild steel

The effects of metal alkoxide type and relative humidity on the durability of alkoxide-primed, adhesively bonded steel wedge crack specimens have been determined. Aluminum tri-secbutoxide, aluminum tri-tert-butoxide, tetrabutyl orthosilicate, and titanium(IV ) butoxide were used as alkoxide primers. Grit-blasted, acetone-rinsed mild steel adherends were the substrates bonded with epoxy and polyethersulfone. The two aluminum alkoxides significantly enhanced the durability of the adhesively bonded steel, while the titanium alkoxide showed no improvement in durability over a nonprimed control. The silicon alkoxide-primed samples gave an intermediate response. The failure plane in the adhesively bonded samples varied with the relative humidity during the priming process.     

Adhesively bonded steel tubes — Part I: Experimental investigations

Circular hollow sections (CHS) represent a class of tubular structural steel elements that enjoy great popularity among architects, and civil engineers. Connections thereof, however, remain complicated, despite significant developments in welding procedures. The first part of this series of two articles summarises research on adhesive bonding as a substitute to traditional joining techniques for tubular sections on a large scale. For that purpose, suitable adhesives have been selected and fully characterised, their adequacy for the required strength in combination with steel verified on lap shear samples, and finally corresponding adhesively bonded tubular joints tested in quasi-static loading with diameters from 42 mm (joint capacities from 55 kN) up to 300 mm (joint capacities up to 1’800 kN). Additionally to various diameters and overlap lengths considered, effects resulting from different types of imperfections, as axial and angular misalignment, on joint strength were experimentally investigated. Presented results clearly indicate that adhesive bonding is a joining technique adapted for civil engineering applications. The second part of this series presents a design methodology for adhesively bonded tubular joints that fits into the conceptual framework of civil engineering practice.     

An updated review of adhesively bonded joints in composite materials

Continuing interest and more developments in recent years indicated that it would be useful to update Banea and da Silva paper entitled “Adhesively bonded joints in composite materials: an overview”. This paper presents an updated review of adhesively bonded joints in composite materials, which covers articles published from 2009 to 2016. The main parameters that affect the performance of bonded joints such as surface treatment, joint configuration, geometric and material parameters, failure mode etc. are discussed. The environmental factors such as pre-bond moisture, moisture and temperature are also discussed in detail and how they affect the durability of adhesive joints. Lots of shortcomings were resolved during the last years by developing new materials, new methods and models. However, there is still a potential to evaluate and identify the best possible combination of parameters which would give the best performance of composite bonded joints.     

Time-dependent behavior of adhesively bonded composite–composite beams under flexural loading

Abstract

Time-dependent behavior is characteristic of adhesively bonded structureswhen put under constant load (creep). In this study, adhesively bonded beam specimens prepared by adhesively bonding two unidirectional carbon fiber laminated beams were subjected to accelerated three-point bending creep tests. A three-point bending test was selected because of its simplicity and the fact that bending stresses tend to develop in structures under load even if not subjected to direct flexural load. The aim of this study is to predict the long-term behavior and to investigate the long-term creep response of the adhesively bonded composite system. The long-term creep behavior was predicted by time–temperature superposition principle (TTSP) and construction of the master curve at a reference temperature.     

Comparison between experimental and numerical study of the adhesively bonded scarf joint and double scarf joint: Influence of internal singularity created by geometry of the double scarf joint on the damage evolution

The objective is to investigate the influence of singularity created by the internal geometry of the double scarf joint, on the damage evolution to the adhesively bonded joint. Several finely instrumented tests are carried out to characterize the damage process unlike the ultimate failure of the adhesively bonded joint. The approach is to compare the micromechanical behavior of adhesively bonded scarf joint and double scarf joint, with the same scarf angle value. Experimental results are obtained by strain gauge measurements to distinguish three damage thresholds, which characterize the damage evolution of the adhesively bonded joint. Numerical results use a damage criterion in order to predict progressive damage evolution. The numerical results show the viability of the failure criterion and the complementarity between experimental and numerical works allows refining our final conclusions.     

Effects of adhesive fillers on the strength of tubular single lap adhesive joints

When an adhesively bonded joint is exposed to a high environmental temperature, the tensile load capability of the adhesively bonded joint decreases because the elastic modulus and failure strength of the adhesive decrease. In this paper, the elastic modulus and failure strength of the adhesive as well as the tensile load capability of the tubular single lap adhesively bonded joint were experimentally and theoretically investigated with respect to the volume fraction of filler and the environmental temperature. Two types of fillers - Al₂O₃ (alumina) and chopped fiber E glass - were used. From the experiment, it was found that the elastic modulus and failure strength of the adhesive increased in accordance with the increase of volume fraction of the filler and decreased with the environmental temperature rise. It was also found that the tensile load capability of the tubular single lap adhesively bonded joint decreased as the environmental temperature increased; however, it had no correlation with the volume fraction of filler because of the effect of the fabrication thermal residual stresses generated by the CTE difference between the adherend and adhesive.     

Failure behavior of adhesively bonded joints with a rubber modified epoxy adhesive under tensile-shear combined cyclic loading

Rubber-modified epoxy adhesives are used widely as structural adhesive owing to their properties of high fracture toughness. In many cases, these adhesively bonded joints are exposed to cyclic loading. Generally, the rubber modification decreases the static and fatigue strength of bulk adhesive without flaw. Hence, it is necessary to investigate the effect of rubber-modification on the fatigue strength of adhesively bonded joints, where industrial adhesively bonded joints usually have combined stress condition of normal and shear stresses in the adhesive layer. Therefore, it is necessary to investigate the effect of rubber-modification on the fatigue strength under combined cyclic stress conditions. Adhesively bonded butt and scarf joints provide considerably uniform normal and shear stresses in the adhesive layer except in the vicinity of the free end, where normal to shear stress ratio of these joints can cover the stress combination ratio in the adhesive layers of most adhesively bonded joints in industrial applications.

In this study, to investigate the effect of rubber modification on fatigue strength with various combined stress conditions in the adhesive layers, fatigue tests were conducted for adhesively bonded butt and scarf joints bonded with rubber modified and unmodified epoxy adhesives, wherein damage evolution in the adhesive layer was evaluated by monitoring strain the adhesive layer and the stress triaxiality parameter was used for evaluating combined stress conditions in the adhesive layer. The main experimental results are as follows: S–N characteristics of these joints showed that the maximum principal stress at the endurance limit indicated nearly constant values independent of combined stress conditions, furthermore the maximum principal stress at the endurance limit for the unmodified adhesive were nearly equal to that for the rubber modified adhesive. From the damage evolution behavior, it was observed that the initiation of the damage evolution shifted to early stage of the fatigue life with decreasing stress triaxiality in the adhesive layer, and the rubber modification accelerated the damage evolution under low stress triaxiality conditions in the adhesive layer.