难粘高分子材料的难粘原理

胶粘剂与被粘物要形成牢固的胶接接头,涉及到一系列的复杂问题.如胶粘剂的选择及组成配方,被粘粕物的表面特性及表面处理,粘接工艺及条件的控制,胶接接头的设计及性能检验等.但是从形成胶接接头的基本条件来分析,一般必须满足两个条件:第一,胶粘剂在涂胶过程中,应当具有流动性,对被粘物表面有良好的润湿作用,形成的接触角要小;第二,胶粘剂在固化过程中,要能与被粘物表面形成化学键或次价键,即在粘     

家庭用胶粘剂的选择

近年来,随着粘接技术的发展,胶粘剂的品种和数量与日俱增,各行各业应用极为广泛,特别在人民生活中尤为突出。因此,笔者就自己在工作和学习中的体会谈谈家庭用胶粘剂的选择。家庭选择胶粘剂,必须考虑被粘物的种类和性质,对被粘物了解得越透彻,所选用的胶粘剂就越合适,粘接的效果就越好。同时还应考虑胶接接头承受应力的类型、大小及持续时间、胶接件使用的环境条件(如温度、介质等)、被粘物所允许固化的最高温度和压力、胶接接头的形状、胶接面的大     

胶粘剂粘接强度影响因素的探究

研究了影响胶粘剂粘接强度的主要因素,探讨了粘接物表面粗糙程度、粘接物表面处理方法、固化温度与时间、胶层厚度、固化压力以及水分对胶粘剂粘接强度的影响。     

胶粘剂弹性模量对折曲胶接接头应力分布的影响

通过ANSYS有限元软件建立了折曲胶接接头的弹塑性有限元模型,考察了胶粘剂的力学性能参数弹性模量对其应力分布的影响。研究结果表明:四种不同的胶粘剂,其弹性模量越大,胶层中各应力的峰值越大,搭接区被粘物剥离应力峰值逐渐呈现出上升的趋势;当胶粘剂弹性模量为50 MPa时,被粘物的各应力分量存在较大的应力尖角(应力集中现象)。     

航空用环氧胶粘剂非最佳固化

本文中，检测了用于飞机制造和修理的四种环氧胶膜，当偏离厂家提供的最佳固化周期时，建立了偏差的影响，评价了固化周期的变化及铝被粘物两种表面制备方法（铬酸浸蚀或打磨后硅烷处理）用热分析法检测胶粘测胶剂固化程度和玻璃化转变温度，通过测量剪切强度，胶接耐久性和有浸蚀体中的化学性来评价胶粘剂的性能，上述胶粘剂的性能受偏离最佳固化条件的影响取决于胶粘剂的组成，需要进行测定，而不能预测。     

高性能航空KH-CL-RTV-2型硅橡胶胶粘剂的粘接工艺研究

以高性能航空KH-CL-RTV-2型硅橡胶作为胶粘剂,采用单因素试验法着重考察了固化工艺、稀释剂用量、金属基材、单双面喷胶、胶层厚度和填料等因素对胶粘剂粘接强度的影响,从而优选出胶接件的最佳施胶工艺;最后利用硅橡胶黏度-时间曲线对胶接件的固化过程进行了验证和解释。研究结果表明:稀释剂环己烷用量对胶接件的粘接强度无影响;胶接件的最佳施胶工艺是双面喷胶、胶层厚度为0.50 mm、被粘基材为除油打磨处理后的铝合金、固化温度为50℃和固化时间为36 h,此时胶接件的粘接强度(为3.04 MPa)相对较大。     

国内外胶粘剂拉伸剪切强度试验方法(金属对金属)标准的对比

对国内外主要几个胶粘剂单搭接拉伸剪切强度试验方法(金属对金属)标准进行了对比,并总结了各标准之间的相似和差异.发现随着加载速度和被粘试片厚度的增加,胶粘剂强度和试样拉伸模量都会有所提高,但数据的标准偏差会有所增加.随着试样长度及搭接长度的增加,试样的拉伸剪切强度会有较大提高,但拉伸模量会降低很多,数据的平行性会有所改善...     

台阶搭接铝合金接头应力分布的数值分析

用弹塑性有限元法研究了被粘物上台阶高度和长度对铝合金单搭接接头胶层中应力分布的影响。结果表明,被粘物自由端内侧的台阶使搭接区接头端部处的应力峰值显著下降,应力向搭接区中部转移;胶层中应力峰值大体上随着台阶高度的增大而降低,随台阶长度的增大而向中部转移;当台阶高度为0．5mm而台阶长度为4．5mm时,接头上胶层中应力分布较好。     

通用型不饱和聚酯树脂室温潮湿条件下固化体系的研究

一、前言通用型不饱和聚酯树脂胶粘剂粘度低,浸润速度快,对各种金属和非金属材料具有良好的粘附力,可常温固化,是一种工艺性较好的非结构胶粘剂。我厂几年前就将不饱和聚酯树脂胶用于生产。但由于不饱和聚酯树脂通用的I~#固化体系(过氧化环己酮——环烷酸钴),在夏季高湿度(相对湿度>80％)环境条件下,不能使树脂充分固化,使粘接强度显著下降,严重影响产品质量,为了适应生产的需要,我们对I~#固化体系进行了改进,使不饱和聚酯胶可在室温高湿条件下固化。二、分析与对策当环境湿度过大时,被粘物表面吸附了一定量的水份,胶接时,被粘物表面的水份与I~#固化体系中的钴盐容易形成络合物,这种络合物比钴本身的     

电热载荷对CFRP修理搭接接头剪切性能的影响

采用单层预浸料搭接简化构型,研究电热载荷对复合材料层板挖补修理搭接接头层间剪切性能的影响。通过自制的复合材料电热测试平台,测试了不同电流制度下,随搭接长度不同试样接头处温度分布。研究了不同电流强度下搭接接头温度变化规律,初步揭示了搭接接头长度-温度-电阻之间的关系,并对不同电流载荷下挖补搭接接头的层间剪切性能进行研究。研究结果表明,通电过程中,搭接区域温度升高较快,非搭接区域温度无明显变化。低电流时,电热促使接头树脂进一步固化,适当提高了接头搭接界面的粘接性能,其剪切强度略有上升;当通电电流过大时,接头温度急剧上升,对搭接区域产生过热损伤,降低了接头的剪切强度。     

Prediction of the tensile load-bearing capacity of a co-cured single lap joint considering residual thermal stresses

In this paper, stress distributions in a co-cured single lap joint subjected to a tensile load were investigated using the finite element analysis. Residual thermal stresses, which resulted from the curing process of the co-cured single lap joint, were also considered. Since the adhesive layer in the co-cured single lap joint was about 10 μm thick, very thin compared with the thickness of both adherends, the interface between the steel and composite adherends was assumed to be perfectly bonded. The co-cured single lap joint was analyzed with respect to several bond parameters such as the bond length and stacking sequence of the composite adherend. The failure mechanism of the co-cured single lap joint was partial cohesive failure in the composite material, which was significantly affected by the interfacial tensile stress at the free edge of the co-cured single lap joint. Interfacial tensile stress was a primary factor that caused interfacial delamination between the steel and composite adherends in the co-cured single lap joint. Finally, tensile load-bearing capacities calculated from the Ye-delamination failure criterion were compared with the experimental results, and relatively good agreement was found.     

Effect of Autoclave Bonding Pressure and Temperature on Polycarbonate Single Lap Joints with polyurethane adhesive

Adhesive joints are good replacement for bolted and welded joints. Adhesive joint performance over the life depends on joint strength. Strength of joint depends upon curing process parameters used during bonding. This study investigates the effect of cure temperature and pressure on the mechanical performance of autoclave-bonded single lap joints (SLJ). Joint load transfer capacity (LTC) data and failure mode analysis are provided. Test joints are made of two polycarbonate lexan adherends that are autoclave-bonded together using aliphatic polyether (Polyurethane) film adhesive (Huntsman PE399). Two levels of cure pressure and cure temperature are investigated, for their effect on joint load transfer capacity, failure mode, and joint stiffness after heat cycling at a low or high level of relative humidity. Experimental results showed higher cure temperature increases joint performance.     

Thermal non-linear elastic stress analysis of an adhesively bonded T-joint

Adhesive joints consist of adherends and an adhesive layer having different thermal and mechanical properties. When they are exposed to uniform thermal loads the mechanical-thermal mismatches of the adherends and adhesive layer result in uniform but different thermal strain distributions in the adhesive and adherends. The thermal stresses arise near and along the adherend-adhesive interfaces. The present thermal stress analyses of adhesively bonded joints assume a uniform temperature distribution or a constant temperature imposed along the outer boundaries of adhesive lap joints. This paper outlines the thermal analysis and geometrically non-linear stress analysis of adhesive joints subjected to different plate edge conditions and varying thermal boundary conditions causing large displacements and rotations. In addition, the geometrically non-linear thermal stress analysis of an adhesively bonded T-joint with single support plus angled reinforcement was carried out using the incremental finite element method, which was subjected to variable thermal boundary conditions, i.e. air streams with different temperatures and velocities parallel and perpendicular to its outer surfaces. The steady state heat transfer analysis showed that the temperature distribution through the joint members was non-uniform and high heat fluxes occurred inside the adhesive fillets at the adhesive free ends. Based on the geometrically non-linear stress analysis of the T-joint bonded to both rigid and flexible bases for different plate edge conditions, stress concentrations were observed at the free ends of adhesive-adherend interfaces and inside the adhesive fillets around the adhesive free ends, and the horizontal and vertical plates also experienced considerable stress distributions along outer surfaces. In addition, the effect of support length on the peak thermal adhesive stresses was found to be dependent on the plate edge conditions, when a support length allowing moderate adhesive stresses was present.     

Benchmark tests on adhesive strengths in butt, single and double lap joints and double-cantilever beams

The RC99 committee of the Japan Society for Mechanical Engineers conducted the benchmark tests on strengths of adhesive joints using different testing methods. The effects of joint configuration, loading mode, adherend yield strength and so on, on the strength and data scatter were investigated using two typical epoxy adhesives. The strengths obtained by various tests were compared with each other. The relationships among strengths of butt, single lap and double lap joints and fracture toughness were given. Thirteen member institutes of the committee participated in this project. The benchmark results allow us to recognize that the joint strengths are strongly affected by the curing process. The key to obtaining the appropriate joint strength, is precise temperature control inside the adhesive layer for curing. Toughened adhesives do not always give higher joint strengths than untoughened adhesives. The yield strength of adherends much affects the observed lap joint strength of adhesives.     

Optimal Design of the Adhesively-Bonded Tubular Single Lap Joint

In this paper, a method for the optimal design of the adhesively-bonded tubular single lap joint was proposed based on the failure model of the adhesively-bonded tubular single lap joint. The failure model incorporated the nonlinear mechanical behavior of the adhesive as well as the different failure modes in which the adhesive failure mode changed from bulk shear failure, via transient failure, to interfacial failure between the adhesive and the adherend, according to the magnitudes of the residual thermal stresses induced by fabrication.

The effects of the design parameters for the adhesively-bonded tubular single lap joint, such as the thicknesses of adhesive layer and adherends, the bonding length, and the scarfs of adherends, on the torque transmission capability and the efficiency of the adhesive joint were investigated.     

Optimal Design of the Adhesively-Bonded Tubular Single Lap Joint

In this paper, a method for the optimal design of the adhesively-bonded tubular single lap joint was proposed based on the failure model of the adhesively-bonded tubular single lap joint. The failure model incorporated the nonlinear mechanical behavior of the adhesive as well as the different failure modes in which the adhesive failure mode changed from bulk shear failure, via transient failure, to interfacial failure between the adhesive and the adherend, according to the magnitudes of the residual thermal stresses induced by fabrication.

The effects of the design parameters for the adhesively-bonded tubular single lap joint, such as the thicknesses of adhesive layer and adherends, the bonding length, and the scarfs of adherends, on the torque transmission capability and the efficiency of the adhesive joint were investigated.     

CRH3高速动车组空调通风口胶接结构设计

通过理论分析和计算确定了动车组空调通风口部件与铝合金车体胶接用胶粘剂的强度指标。介绍了胶粘剂的选择及胶接结构的设计原则,考查了搭接长度、搭接宽度、胶层厚度和被粘接材料厚度等对胶接件粘接强度的影响。结果表明:车体与空调通风口部件的胶接接头选择受剪切应力作用的搭接接头较适宜,并且搭接接头的承载能力随搭接长度或宽度增加呈先快速上升后趋于稳定态势;当搭接长度为10 mm、胶层厚度为6 mm、铝合金板厚度为5 mm且常温湿固化型单组分PU(聚氨酯)胶粘剂的剪切强度超过0.23 MPa时,搭接接头的承载能力相对最大。     

Dynamic strength of single lap joints with similar and dissimilar adherends

The increased use of adhesives for joining structural parts demands a thorough understanding of their load carrying capacity. The strength of the adhesive joints depends on several factors such as the joint geometry, adhesive type, adherend properties and also on the loading conditions. Particularly polymer based adhesives exhibit sensitivity to loading rate and therefore it is important to understand their behavior under impact like situations. The effect of similar versus dissimilar adherends on the dynamic strength of adhesive lap joints is addressed in this study. The dynamic strength is evaluated using the split-cylinder lap joint geometry in a split Hopkinson pressure bar setup. The commercial adhesive Araldite 2014 is used for preparing the joints. The adherend materials considered included steel and aluminum. The results of the study indicated that the dynamic strength of the lap joint is influenced by the adherend material and also by the adherent combination. Even in the case of joints with similar adherends, the strength was affected by the adherend type. The strength of steel–steel joints was higher than that for aluminum–aluminum joints. In the case of dissimilar adherends, the strength was lower than that of the case of similar adherends. The results of this study indicate that the combination of adherend material should also be accounted for while designing lap joints.     

Analytical models of adhesively bonded joints—Part II: Comparative study

The literature survey presented in Part I describes the major analytical models for adhesively bonded joints, especially for single lap joints. By consulting the summary table given in Part I, the designer can choose from a wide range of models which is the best for a particular situation. However, the information given in the summary table is not sufficient for a proper selection. The designer also needs to know the time required for setting up an analysis and solving it. Another important factor is the accuracy of strength prediction. Therefore, models of increasing complexity were selected from the summary table and a comparative study was made in terms of time requirements and failure prediction for various cases. Three main situations were considered: elastic adherends and adhesive, elastic adherends with nonlinear adhesive, and nonlinear analyses for both adherends and adhesive. The adherends were both isotropic (metals) and anisotropic (composites). The effects of the overlap length and the adhesive thickness were also considered.     

The determination of dynamic strength of single lap joints using the split Hopkinson pressure bar

The current investigation focuses on the determination of the strength of adhesive-bonded single lap joints under impact with the use of a split Hopkinson pressure bar (Kolsky bar). For this, experiments were conducted at different loading rates, for identical metallic adherends bonded by a two-part epoxy adhesive. Four different types of specimens were adopted, all with a given adhesive thickness. The length of overlap and the width of the adherends were varied resulting in four different areas of overlap. It was found that the average strength, as calculated from the readings obtained from a Kolsky bar, increases with decrease of overlap area. An elastodynamic model for the shear strain of the adhesive-bonded single lap joint was developed to investigate this drastic effect of overlap area on the average strength of the joint. The mathematical model was found to be dependent on both the material properties of the adherend and adhesive, as well as the structural properties of the joint, viz. the width and the thickness of the adhesive layer. A combined experimental-numerical technique was used to predict the strain distribution over the length of the bond in the adhesive. It was found that the edges of the adhesive were subjected to maximum strain, while a large part of the adhesive was found to exhibit zero shear strain. The effect of the lap length and the width was studied individually. The cumulative effect of averaging the strain over the entire overlap area, was decreased shear strain for an increased overlap area. The Kolsky bar was identified to give conservative values of the shear strength of an adhesive bonded lap joint under high rates of loading.