胶接接头力学研究回顾

回顾了胶接接头力学性能方面的研究进展 ,并讨论了进一步研究的方向。     

胶层厚度对胶接性能的影响

本文介绍了胶层厚度影响胶接接头力学性能、耐久性能的若干现象及作者对这些现象的初步理解。     

胶接接头无损检测研究进展

介绍了胶接接头无损检测技术近年来的发展情况，对超声波、声、应力波等无损检测技术的发展作了概要的阐述，同时对胶接接头的强度检测进行了分析，认为检测中所选用的强度相关参数，应充分体现胶接接头对应力的响应，这样才可能实现胶接强度的定量检测。     

胶接接头剪切和正拉强度试验方法的分析

分析了胶接接头现行剪切强度和正拉强度测试方法中存在的问题，指出由于应力集中及多种应力的综合作用导致测试值出现较大偏差，提出了胶接接头剪切强度和正拉强度测试方法的改进意见。     

胶接接头90年耐久性的评价方法

胶接接头,特别是结构性的胶接接头的耐久性或长期可靠性的评价,是一个非常重要、也非常困难的课题。每当遇到粘接问题,特别是结构粘接的问题时,人们总是会问：“能用多少年？”就是因为影响粘接强度和耐久性的因素太多、太复杂,而至今尚无一个科学可靠的评价方法,所以人们很难不心存疑虑。     

胶层的粘弹性与内应力松弛

内应力的形成与胶层的粘弹性变化直接有关。胶层在粘流态、高弹性和转变区固化都不会形成巨大的内应力，只有在玻璃态、高度交联和高度结晶状态深度固化，才会形成永久性的巨大内应力，避免在这些状态下深度固化，是胶粘剂配方设计和固化工艺制订时必须遵守的原则。     

胶接工艺对粘接强度的影响

介绍了胶接件的表面处理以及胶黏剂的配制、涂胶、晾置、黏合和固化等因素对粘接强度的影响。表面处理介绍了常用方法,重点描述表面粗糙度与粘接强度的关系。胶黏剂的配制介绍了温度平衡、组分调整与预混、混合调配和配制顺序。涂胶介绍了涂胶方法和注意事项。晾置介绍了不同种类胶黏剂的晾置时间。黏合介绍了粘合方法和时机。固化介绍了固化方式、方法和固化条件三要素,重点描述固化温度、时间和压力与粘接强度的关系。     

胶接接头耐久性的综合研究

以AG—80/DDS、环氧—聚砜和环氧—丁腈结构胶为胶粘剂,45~#钢和LY_(12)—CZ铝合金为被粘材料,综合研究了胶接接头的耐久性。研究结果表明,除胶粘剂外,内外应力、温度、介质和被粘物的表面状态均是影响接头耐久性的重要因素。激光双折射法测定胶接接头内应力是较可行的新方法。     

用聚合物水泥砂浆作新老混凝土的胶接材料

聚合物水泥砂浆的抗裂性能和粘接强度明显优于普通水泥砂浆，是新老混凝土界面的理想胶接材料。本文介绍了聚合物乳液对水泥砂浆的改性机理、聚合物水泥砂浆的配比及性能、应用实例和效果。     

Process variable effect on the strength of autoclave-bonded film adhesive joints

This study investigates the effect of five independently-controlled process variables and variable combinations on the shear strength of autoclave-bonded film adhesive joints. Studied variables include the cure temperature, cure pressure and their respective ramp rates, as well as the duration of cure time. A full factorial design of experiment (DoE) at two levels for each variable is conducted with 3 replicas of each test. Test coupons are made of two layers of polycarbonate lexan that are autoclave-bonded using aliphatic polyether film adhesive (Huntsman PE399). Two set of test joints are used for generating test data on shear strength and failure mode. Bonded joints in the first set are tested prior to any environmental cycling, in order to generate baseline data on joint shear strength and failure mode. However, samples from the second set of autoclave-bonded joints were heat-cycled, in an environmental chamber at high relative humidity, prior to testing for shear strength. Test data on shear strength and failure mode is statistically analyzed using ANOVA.     

Bonding adhesive joints with radio-frequency dielectric heating

The feasibility of using radio-frequency (RF) dielectric heating to cure thermoset adhesives has been evaluated. Thermoset and thermoplastic polymer panels have been bonded to steel using conventional one-and two-part epoxy and two-part urethane adhesives. Process cycle times for adhesive cure using RF heating were about 20 to 60 seconds, compared with about 20 to 30 minutes for the same materials using conventional oven-cure methods. Thermoset substrates bonded included glass fibre-reinforced composite panels based on sheet moulding compound (SMC) and resin transfer moulding styrene-vinylester (RTM). Thermoplastics such as polycarbonate, polyarylate, Noryl, ABS and polymethylmethacrylate were also successfully bonded. RF bonding experiments were performed by preparing and testing lap-shear joints as well as by joining a large test structure with a 25 mm x 1.25 m bondline. Bonding of painted steel to SMC composite, SMC to SMC and steel to RTM composite were also accomplished using the RF dielectric heating process.     

Creep testing of carbon containing refractories under reducing conditions

Mechanical testing of carbon containing refractories at high temperatures requires measures to protect the sample from oxidation. Therefore, special setups for tensile and compressive creep testing were developed to prevent the oxidation of carbon in the sample. A MgO-C refractory was selected for a case study. These developments allow the quantification of the tensile and compressive creep behaviour of MgO-C refractories at temperatures up to 1500?°C. The creep parameters are determined by an inverse evaluation method for the obtained experimental data. They enable the consideration of creep in a thermomechanical finite element simulation of refractory linings in service.     

胶层局部缺陷对胶接接头承载能力的影响研究

针对汽车车身中应用日益广泛的钢板胶接结构,通过实验得到了不同胶层局部缺陷对接头承载能力的影响规律,进而采用接头的三维弹塑性有限元模型,解释了实验结果,并提出了接头承载危险系数(K)的概念。研究结果表明,胶层为四角缺陷时,接头处的危险系数随缺陷面积的增加而增大(从0.66增加到0.91),接头的断裂强度由8640N降低到8121N;胶层为中央缺陷时,接头处的危险系数随中央缺陷面积的增加增幅较小,接头承载能力基本不变。     

Creep Resistance of Pressure Sensitive Mounting Tapes

The first part of the paper deals with an approach towards a systematic testing procedure to evaluate the creep behavior of single lap shear specimens bonded with PSA mounting tapes under the influence of temperature and humidity. The study includes commercial tapes as well as self-formulated pressure sensitive adhesives based on styrene block copolymers. The second part of the paper relates the obtained data, consisting of the time-dependent sample deformation and time-to-failure, to the observed failure modes. The results show that the creep behavior of a pressure sensitive adhesive is not only dependent on the environmental, conditions but also on the substrate material and its surface composition. The results for the self-formulated adhesives reveal the possibility of enhancing creep resistance of PSA's by adding fillers to the formulation. The paper closes with a modification of the Burgers model that is suitable for describing the creep/creep recovery behavior of tested lap shear specimens. The effect of nonlinear behavior in cyclic loading experiments is described and a thesis for the relation of nonlinear creep behavior to damaging processes in the adhesive bond is presented.     

Surface pretreatment of plastics for adhesive bonding

Abstraet-Many plastics have a poor tendency to bond to other materials because of their inherent inert chemical structure and thus require a pretreatment. Wet chemical methods are expensive because of the disposal of the waste liquids. In this study, the corona treatment (Ional process), the low-pressure plasma process, and the fluorination process were tested and compared with each other. The following plastics were tested: PP (polypropylene), PBT (polybutyleneterephthalate), PBT blends, and a high-temperature thermoplastic, PEEK (polyetheretherketone). In particular, the low-temperature plasma process results in excellent adhesion strength. In addition, we have shown that the stability of freshly plasma-treated surfaces could be maintained for time periods of at least several days.     

Effects of a sheet metal stamping lubricant on static strength of adhesive-bonded aluminum alloys

Stamping lubricant is often applied to sheet metal surface to improve the formability. In this study, the effect of stamping lubricant on the strength of adhesive-bonded 1.0-mm-thick bare aluminum (Novelis X610-T4PD) and 0.9-mm-thick bare aluminum (Novelis X626-T4P) joints was investigated. It was found that while a proper amount of lubricant (~2.21 g/m², 1.5?μL lubricant on the 25?×?25 mm coupon) applied on the surface of the substrate had little effect on the joint strength, levels more than 2.21 g/m² lubricant significantly decreased the joint strength. When the lubricant amount exceeds the adhesive’s compatibility with the lubricant, the negative effects of pores from lubricant evaporation during curing on the strength overrides the positive effect of increased adhesion energy. Furthermore, the presence of 2.21 g/m² lubricant minimized the reduction of the strength of the joints pre-exposed to neutral salt spray (i.e. a concentration of 50?±?5 g/L sodium chloride solution). Careful analyses of the results indicated that corrosion of aluminum substrate surfaces of the pre-exposed joints led to the degradation in bond adhesion between the adhesive and substrates, and consequently resulted in the decrease of the joint strength. The hydrophobic lubricant protected the aluminum substrate from electrochemical reaction by damage of the bond adhesion between the adhesive and substrates leading to the lubricated joints having better corrosion resistance than the unlubricated joints.     

溶剂型橡胶系压敏胶的研究

采用自交联工艺合成溶剂型橡胶系压敏胶,讨论了增粘树脂的用量、软化剂的用量、交联剂的用量、聚合反应温度、烘胶温度和烘胶时间对压敏胶性能的影响。实验表明,增粘树脂可以有效地提高压敏胶的初粘性和剥离强度,交联剂能够全面调节压敏胶的性能,适当的烘烤温度和烘烤时间有利于提高压敏胶的粘接性能。得出了最佳工艺条件为:增粘树脂与天然橡胶的质量比为701∶00,软化剂含量为20%,交联剂为0.4%,接枝共聚的温度为80℃。     

Analysis of aircraft adhesive joints under combined thermal and mechanical cyclic loadings

The effect of thermal aging on the static and fatigue behavior of adhesively bonded aircraft joints has been investigated. The aging cycle consisted of high and low temperatures at different levels of humidity in accordance with ASTM D1183-70 test procedure C for exterior land and air conditions. Single lap joints of aluminum 7075-T6 and 3M structural adhesive prepreg were used. The static loading behavior showed no effect of thermal cycling on the load-carrying capacity of the joints. However, the joints' static deformation increased with increasing number of aging cycles. The specific energy of damage concept was used to extract parameters characteristic of the joint resistance to fatigue loading. These parameters are the specific energy of damage, y', and the energy dissipation coefficient, β'. It was found that the specific energy of damage, γ', was reduced from 35.40 kJ/m³ for joints without thermal cycling to 28.9, 27.1, and 25.9 kJ/m³ for joints subjected to 2, 4, and 6 thermal aging cycles, respectively. However, the energy dissipation coefficient, β', increased from 23 x 10^-5 for joints without thermal aging to 26.5 x 10^-5, 27.6 x 10^-5, and 28.8 x 10^-5 for joints with 2, 4, and 6 aging cycles, respectively. The decrease in the value of y' and the increase in β' indicate a loss of resistance to fatigue crack propagation. The greatest loss of fatigue resistance was encountered after the first two thermal aging cycles. While the static results showed an enhancement in the joints' fracture toughness, based on the area under the load-displacement curve, the fatigue crack propagation data showed a considerable loss in resistance due to aging. Hence this paper emphasizes that it is important to evaluate the resistance of adhesive joints to combined thermal and mechanical cycling if the joints are expected to serve in such conditions.     

On the effect of pulsed laser ablation on shear strength and mode I fracture toughness of Al/epoxy adhesive joints

The present work describes an experimental study about the shear strength and the mode I fracture toughness of adhesive joints with substrates pre-treated by pulsed laser ablation. An ytterbium-doped pulsed fiber laser was employed to perform laser irradiation on AA6082-T4 alloy. Morphological and chemical modifications were evaluated by means of surface profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Thick adherend shear tests were carried out in order to assess the shear strength while the mode I fracture toughness was determined using the double cantilever beam. For comparison, control samples were prepared using classical surface degreasing. The results indicated that laser ablation has a favorable effect on the mechanical behavior of epoxy bonded joints; however, while a + 20% increase was recorded for shear strength, a remarkable threefold enhancement of fracture toughness was observed with respect to control samples. XPS analyses of treated substrates and SEM observations of the fracture surfaces indicated that laser pre-treatment promoted chemical and morphological modifications able to sustain energy dissipation through mechanical interlocking. As a result cohesive failure within the adhesive bond-line was enabled under predominant peel loading.