线膨胀系数对拉伸剪切性能的影响

为获得高强稳定的粘接,绝不可忽视被粘材料和胶黏剂的线膨胀系数对粘接件力学性能的影响。西北工业大学理学院高分子研究所对此进行了专门实验研究,采用改性环氧胶黏剂粘接不同的材料,并对粘接件进行拉伸剪切强度测定和温度影响试验,试验条件为120℃／8h＋180℃／2d,得出了很有价值的结论：（1）被粘材料线膨胀系数不同,使胶层在热冷（热处理和冷却）变化过程中受内应力作用而破坏,同时热空气进入胶层而使胶层氧化变色,致使胶黏剂界面结合强度和胶黏剂本身强度降低,结果拉伸剪切强度下降。例如,     

改善单组分热固化胶粘剂流淌性的研究

单组分热固化胶粘剂在固化升温过程中因黏度下降而易出现流淌现象,造成胶接区域缺胶,从而增加了施工难度、降低了粘接可靠性。高分子尼龙织物的网孔易于存胶,可有效改善胶粘剂的流淌性;采用尼龙织物和金属丝网控制铝合金胶接件中的胶层厚度,并对上述胶接件在不同温度时的拉伸剪切强度进行了对比试验。研究结果表明:对同种单组分热固化胶粘剂而言,含尼龙织物胶接件的胶接强度并未下降,并且解决了胶粘剂在固化升温过程中因黏度降低而易流淌的问题,而且尼龙织物可较方便地控制胶层厚度。     

航天器电子产品用环氧胶粘剂粘接工艺研究

选择航天器电子产品中常用的三种环氧胶粘剂,采用具有交互作用的正交试验设计,研究了固化温度、固化时间、胶层厚度、被粘接件的表面状态以及固化压力等因素对拉伸剪切强度的影响规律,并通过数据分析得到三种胶粘剂的拉伸剪切强度回归方程和最优工艺条件。研究结果表明:固化温度对拉伸剪切强度的影响较为明显,较优工艺条件下的拉伸剪切强度实测值与回归方程的预测值基本一致,为航天器电子产品用环氧胶粘剂的选用和粘接工艺技术提供了试验依据。     

浇注型聚氨酯弹性体与金属粘接性能的研究

以CPUE(浇注型聚氨酯弹性体)和45#钢为试验对象,探讨了胶粘剂种类、金属表面处理、聚氨酯(PU)硬度、加热时间和保存时间对CPUE/金属胶接件粘接性能的影响。研究结果表明:在5种胶粘剂中,双组分胶粘剂245N的粘接强度相对最高,而胶粘剂240N的耐水性相对最好;聚酯型CPUE/金属胶接件的粘接强度高于聚醚型CPUE/金属胶接件,高硬度CPUE/金属胶接件的粘接强度高于低硬度CPUE/金属胶接件;胶粘剂的粘接强度随加热时间延长而逐渐降低,CPUE/金属胶接件的保存时间为7 d时,粘接强度仍相对较高。     

环氧树脂胶粘剂工程应用研究

采用某种型号的环氧树脂(EP)胶粘剂胶接LY12-CZ铝合金试片,在110～170℃范围内加热4 h后测定胶接件的剪切强度,并对该胶接件的不同加载速率与拉伸剪切强度的关系进行了研究。结果表明:短时高温加热对该胶粘剂的剪切强度没有影响,这有利于飞机组件的整体修复;拉伸剪切强度随着加载速率的增加而增大,这又为探讨加载速率对不同胶粘剂性能的影响提供了试验依据。     

激光表面处理提高铝合金胶接接头强度的研究

粘接作为重要的汽车轻量化连接技术之一,胶接接头的强度和性能是我们关注的重点,胶接接头的强度和性能完全取决于胶粘剂接触的表面类型,因此在粘接之前对基材表面进行一定处理是粘接工艺中最重要的环节之一。金属的表面处理包括溶剂擦拭、机械打磨、化学清洗和酸蚀。激光表面处理是一种新型绿色环保的表面处理工艺,它可以高速有效的清洁材料表面附着物,并且改变材料表面微观结构及材料表面自由能及浸润性。从而提高粘接接头十字拉伸强度、单搭接拉伸剪切强度和接头耐水性能。通过激光处理,所有接头的破坏形式由界面破坏转为内聚破坏。对铝合金环氧结构胶2098G胶接接头而言,十字拉伸强度、剪切强度和水浴剪切强度,激光处理后比溶剂擦拭分别提高了17.8%,133.8%,88.1%。对铝合金聚氨酯结构胶TS6015胶接接头而言,十字拉伸强度、剪切强度和水浴剪切强度,激光处理后比溶剂擦拭分别提高了698%,225%,223%。激光表面处理有效的使铝合金胶接接头的强度达到胶的本体强度的94%~100%,是铝合金粘接的有效表面处理方法。     

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。     

萘对HR-2抗氢钢粘接性能的影响

用EP(环氧树脂)-酸酐胶粘剂粘接HR-2抗氢钢,制成的胶接件在萘环境中储存1~2 a后会出现脱胶现象。采用扫描电镜(SEM)、X射线光电子能谱(XRD)法、热失重分析(TGA)法、差示扫描量热(DSC)法和红外光谱(FT-IR)法对萘环境中胶粘剂的性能变化进行了分析。研究结果表明:萘升华后渗透至胶粘剂内部,致使胶粘剂氧化降解,故胶粘剂的硬度降低、粘接强度下降;胶接件在萘环境中室温储存1 a后,其拉伸强度接近于0,因而发生脱胶现象,说明在萘环境中不能采用粘接的连接方式。     

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。     

一种新型水性聚氨酯(聚酯型)胶粘剂研制成功

山西省应用化学研究院胶粘剂工程技术开发部近日研制成功一种新型水性聚氨酯(聚酯型)胶粘剂,命名为WD—62 1 0胶粘剂。该胶粘剂不需要加热活化,可以冷粘接,室温下贴合具有极高的初粘力,贴合后即可进行下一工序。同时该胶粘剂还具有出色的耐水性,水中浸泡3个月无开胶现象,剥离试验仍为材料破裂(对PVC/ PVC)。耐热性能突出,加热到1 40℃的温度剥离试验仍为材料破裂,且胶层不变色、耐黄变,可用于浅色热敏性材料的胶接或其他耐温、耐水材料的胶接。如果热活化后粘接,强度、耐水性、耐热性更高。彻底克服了水性聚氨酯胶粘剂耐水性不理想、粘…     

Dismantlement studies of dismantlable polyurethane adhesive by controlling thermal property

This paper investigated the design of dismantlable polyurethane adhesives and dismantling method. To study the dismantlement property of dismantlable polyurethane adhesive by controlling thermal property, we synthesized polyurethane adhesive with various hard segment contents and used thermally expansive microcapsules. The dismantlement of bonded adherend was caused by the expansion of the adhesive layer with the expansion of the thermally expansive microcapsule and softening of the adhesive. For the dismantlement of bonded adherend, the adhesive is needed to have low storage modulus at the expansion temperature of thermally expansive microcapsule. High storage modulus of the adhesive was good for the bonding strength but not for dismantlability. In our study, the dismantlability became better as the hard segment content of adhesive decreased and the bonding strength and heat-resistance were excellent when the hard segment content was more than 25% because of high storage modulus and physical property. Consequently, optimum hard segment content was 25%, which showed excellent adhesion strength and dismantlement of bonded adherend was possible with microwave treatment for 4 min. Using zinc oxide with high dielectric constant could shorten microwave treatment time needed for the dismantlement of the bonded adherend to 3?min by enhancing the heating efficiency of the adhesive.     

Experimental study of adhesively bonded CFRP joints subjected to tensile loads

The tensile performance of adhesively bonded CFRP joints has been investigated experimentally. In this study, overlap length, adherend thickness, adherend width and scarf angle were chosen as design parameters. All load–displacement curves are linear, except that the thicker single-lap joints behave slightly nonlinearity due to the bending effect caused by eccentric loading. The lap shear strength is not directly proportional to overlap length, adherend thickness, adherend width and scarf angle for the brittle adhesive studied in the paper. The major failure mode includes adhesive shear failure and adherend delamination failure, sometimes accompanying with some fiber pull-out. Finally, the lap shear strength of three different lap types with similar bonding area (W=25 mm, L=10 mm, θ=5.71°) and adherend thickness (0.96 mm) was analyzed. It is found that the double-lap joint has the highest ultimate failure load. However, when considering the lap region weight, the scarf-lap joint is the most efficient.     

The effect of adhesive thickness on tensile and shear strength of polyimide adhesive

The effect of adhesive thickness on tensile and shear strength of a polyimide adhesive has been investigated. Tensile and shear tests were carried out using butt and single lap joints. Commercially available polyimide (Skybond 703) was used as adhesive and aluminum alloy (5052-H34) was used as adherends. The tensile strength of the butt joints decreased with increasing adhesive thickness. In contrast, adhesive thickness did not seem to affect the shear strength of single lap joints. The fabricated joints using the polyimide adhesive failed in an interfacial manner regardless of adhesive thickness. The linear elastic stress analysis using a finite element method (FEM) indicates that the normal stress concentrated at the interface between the adherend and the adhesive. The FEM analysis considering the interfacial stress well explains the effect of adhesive thickness on the joint strength.     

Preparation of block copolyetheramides and their properties as hot melt adhesives

Block copolyetheramides were prepared by incorporating polyether into polyamide through melt polycondensation of polyetherdiamine, piperazine, dimer acid, and ε-caprolactam. Bulk properties of block copolyetheramide, such as tensile strength, tensile modulus, elongation at break, hardness, and impact strength, were evaluated with respect to composition. Investigation on the lap shear strength and T-peel strength of block copolyetheramide hot melt adhesive showed that the lap shear strength was more composition-dependent. Moisture and elevating test temperature also reduced the lap shear strength significantly.     

水下环氧树脂胶粘剂用水下固化剂的性能研究

目前可用于水下粘接的EP(环氧树脂)胶粘剂用水下固化剂种类不多,主要是一些憎水类改性胺固化剂(如810和301P等)。以不同种类的水下固化剂作为试验对象,着重探讨了水下固化剂的本体黏度、相应水下EP胶粘剂的某些性能(如水下凝胶时间、水下拉伸剪切强度及水下压缩强度等)。研究结果表明:水下EP胶粘剂的适宜凝胶时间为1h左右;水膜隔离胶粘剂/被粘物的界面问题只影响拉伸剪切强度,而不影响压缩剪切强度,故水下固化剂的憎水性良好时,相应EP胶粘剂的压缩强度相对较高,但其钢/钢拉伸剪切强度会受到一定的影响;810和301P具有一定的憎水性,并且相应EP胶粘剂的水下凝胶时间均为1h左右,故不同黏度的810和301P复配可制得综合性能更好的水下EP胶粘剂。     

Stress Distribution in Single Lap Joints with a Cracked Composite Adherend—Part I: Single Lamina Adherends

The effect of a crack in the overlap region of a single step lap joint is studied on the shear distribution in the adhesive layer. Each adherend is considered to be a lamina with unidirectional fibers aligned in the direction of the applied load. Crack location is selected to be in the top adherend, in the form of cut fibers and matrix bays. The shear-lag model is used to derive the equilibrium equations which are then solved using eigenvector expansion. Additionally, a finite element model of the lap joint was prepared and solved using ANSYS. The results of the two methods perfectly match each other. The effects of crack location along the length of the overlap, crack size, edge cracks, adhesive thickness, and type of fibers were investigated on the shear distribution in the adhesive layer and its corresponding peak values. The effect of dissimilar adherends was also investigated on the adhesive shear stress distribution. According to the results, in the presence of a crack, the peak adhesive shear stress is very susceptible to adhesive thickness and type of fibers used in each adherend. Other factors also influence the peak shear stress to some degree.     

Experimental and Numerical Study of Adhesively Bonded CFRP Scarf-Lap Joints Subjected to Tensile Loads

The tensile performance of adhesively bonded CFRP scarf-lap joints was investigated experimentally and numerically. In this study, scarf angle and adherend thickness were chosen as design parameters. The lap shear strength is not directly proportional to scarf angle and adherend thickness for the brittle adhesive studied in the paper. The major failure mode includes cohesive shear failure and adherend delamination failure. The results present a stepped failure morphology along the bondline in the adhesive layer. A finite element model based on cohesive zone model was established to further investigate the stress distribution of scarf-lap joints with different lap parameters. The numerical results were compared with the experiment results, showing a good agreement, thus verifying the validity of the established numerical model.     

Stress Distribution in Single Lap Joints with a Cracked Composite Adherend—Part II: Laminated Adherends

The effect of a crack in the overlap region of an adhesive single lap joint is studied on the shear stress distribution in adhesive layer. Each adherend is considered to be a laminated composite material with unidirectional fibers aligned in the direction of the applied load. Crack location is selected to be in the top adherend laminate, in the form of cut fibers and matrix bays. The crack can occur in any layer. The shear-lag model is used to derive the equilibrium equations which are then solved by means of eigenvector expansion. The effects of adhesive thickness, crack size, and location in the adherend, total number of layers in each adherends, volume fraction of fibers, and type of fibers are investigated on the shear distribution in the adhesive as well as load distribution in the intact fiber at the crack tip located in the top adherend. The effect of dissimilar laminated adherends is also investigated on the adhesive shear stress distribution. According to the results, in the presence of a crack, the peak shear stress in the adhesive layer and load concentration in the fibers are very susceptible to the adhesive thickness and number of layers in laminated adherends.     

Metal-adhesive bonded systems: Adhesion measurement using a three point flexure test

Single metallic adherend-adhesive bonded specimens are subjected to a three point flexure test in order to investigate the effects of adherend surface conditioning and adhesive curing conditions on the mechanical properties of the substrate-adhesive interfacial region. The main advantage of this test over more conventional ones (i.e. peel, tensile, shear tests) is to induce stress concentration which is responsible for a failure locus within the interfacial region and consequently its ability to provide data representative of practical adhesion in an adhering system. The results obtained are shown to be independent of adherend thickness, adhesive layer thickness, width of the bonded area and displacement speed used during testing. Data presented here are relative to Ti-6Al-4V titanium alloy/epoxy systems. They demonstrate the high sensitivity of the flexure test to the effects of prebonding treatments (chemical etching, anodization) and of adhesive curing conditions on practical adhesion.     

冷热水用氯化聚氯乙烯(PVC-C)管道的性能及安装使用

本文通过与其它聚烯烃冷热水管的性能对比，介绍了PVC—C冷热水管道的优越性能及安装和使用方法。