复合材料管-铝接头胶接结构抗拉性能试验研究

采用膨胀芯模法,通过压机压制工艺研制了直径50 mm,壁厚3 mm的复合材料圆管,为研究复合材料管与铝接头的胶接性能,对胶接结构开展了静态拉伸试验,比较了不同胶结长度与加固方式对于管件-铝接头胶接结构抗拉性能的影响。结果表明,加大胶接段长度和加装记忆合金环均能有效提高胶接结构的抗拉性能。     

复合材料胶接接头温度-湿度-载荷老化机理研究概述

概述了单一影响因素(温度、湿度、载荷)分别对胶粘剂、复合材料和复合材料胶接接头的影响机理,总结了多因素耦合作用下的老化机理。研究结果表明:复合材料胶接接头中的胶粘剂、复合材料以及胶接界面在温度、湿度、载荷的作用下都会发生变化,对接头的性能都有影响。在未来研究复合材料胶接结构老化机理中,在定性分析的基础上进行定量分析,并且需要考虑复合材料老化对胶接接头性能的影响。     

水对液相氧化处理聚乙烯木塑复合材胶接性能的影响

采用液相氧化方法对木粉/聚乙烯木塑复合材料进行表面处理以改善其胶接性能。研究了氧化处理后木塑复合材料胶接接头的耐水性,并利用接触角测试、SEM、FT-IR等分析手段,探讨了木塑复合材料胶接接头在水环境下的老化失效原因。结果表明,未处理的聚乙烯木塑复合材料难以胶接,经过液相氧化处理后,不但可以提高聚乙烯木塑复合材料的胶接强度,还可改善木塑复合材料胶接接头的耐水性。在水的作用下,液相氧化处理聚乙烯木塑复合材的表面结构会发生改变,复合材料中木质纤维的吸水膨胀也会导致材料表面出现裂纹,致使胶接接头失效。     

树脂基复合材料粘接工艺设计

介绍了复合材料粘接的几种方式,说明了粘接连接方式在复合材料构件中的优点及应用,并主要从树脂基复合材料胶接工艺中的接头形式、前处理工艺、表层纤维铺层方向、粘接长度、胶层厚度、材料性质等几个方面阐述对粘接性能的影响,并对粘接工艺进行优化设计,提高胶接质量.     

SY-D15表面处理剂的性能研究

SY-D15表面处理剂具有良好的综合性能,对于不同的复合材料胶接体系都能够显著提高粘接强度,SY-14A胶粘剂-5405/HT3复合材料胶接体系和SY-24C胶粘剂-3218/SW-280A复合材料胶接体系的粘接强度能够提高30%以上,胶接接头具有优异的耐介质、耐热和耐湿热老化等耐久性能。     

飞机复合材料阶梯式胶接结构的疲劳损伤与寿命

随着复合材料胶接技术在飞机主承力结构上的广泛应用,阶梯式胶接形式由于在实际工程过程中易于实现而成为复合材料结构修理和连接的主要形式。目前文献多集中于研究金属、复合材料以及两种材料混合的单搭接结构的疲劳性能,但对于具有高效载荷传递的阶梯式结构的疲劳耐久性研究较少,其疲劳失效机制尚需厘清。本文对多级阶梯复合材料胶接结构进行了拉伸疲劳试验研究,应力比为0. 1。在疲劳试验过程中观测了宏观裂纹的起始与扩展。根据试验数据拟合的S-N曲线,发现疲劳寿命随应力水平的增加而线性降低。在发现目视可见裂纹后至完全断裂,复合材料胶接结构仍具有10%的剩余寿命,说明当出现目视可见裂纹时,应及时维修或更换部件。从试样受力及破坏形式可知,复合材料胶接结构的剪切破坏是引起疲劳损伤的主要原因。通过阶梯状断口形貌分析,发现了内聚破坏、粘附破坏、基体开裂和分层四种典型破坏形式。     

复合材料/金属胶接结构研究进展及发展趋势

胶接连接应用日渐广泛,特别是在汽车和航空航天等结构领域。首先分析了复合材料/金属胶接连接方式的特点,重点介绍了接头中的次弯曲效应、异质材料间刚度与热膨胀系数的不匹配特性以及载荷传递特性。然后总结了提高胶接接头强度的研究进展,主要包括增大胶接长度和宽度、选择胶黏剂、表面处理、增加胶瘤和被粘合物形状的设计等方面。最后对胶接接头的发展趋势进行了展望。     

热-力载荷下复合材料/金属双面胶接接头界面力学模型

在温度和静拉伸载荷共同作用下,考虑胶层的材料非线性,建立了复合材料/金属双面胶接接头界面的力学分析模型,推导出弹性响应和塑性响应下胶层剪应力的分段表达式,使用胶层最大剪应变失效准则计算出胶层主导破坏的结构极限载荷,并与有限元数值结果进行对比和验证。分析表明,双面胶接接头应力分析理论模型与相关简化假设正确、合理。在此基础上,研究了复合材料/金属双面胶接接头在热-力载荷下的胶层剪应力分布特点、破坏模式和失效机理,为胶接结构的承载能力分析及结构改进设计提供理论依据。     

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…     

多异氰酸酯涂覆处理对聚乙烯木塑复合材胶接接头耐水性能的影响

采用多异氰酸酯对聚乙烯木塑复合材料进行表面涂覆处理以改善其胶接性能。利用接触角测试、表面形貌观测以及胶接强度和吸水量测试研究了涂覆表面处理对聚乙烯木塑复合材料胶接接头耐水性能的影响。结果表明,涂覆处理后复合材料的胶接强度和接头耐水性明显提高。水浸后聚乙烯木塑复合材料的表面性质发生了改变,随着水浸时间的延长,表面粗糙度增加,表面接触角下降。长时间水浸下胶接接头的吸水量增加,胶接强度下降。水环境下聚乙烯木塑复合材料中木质纤维的吸水膨胀是造成胶接性能下降的主要原因。     

Experimental study of the influence of adhesive reinforcement in lap joints for composite structures subjected to mechanical loads

The paper deals with experimental investigations on reinforcing the adhesive in single lap joints subjected to mechanical loads such as tensile, bending, impact and fatigue. The adhesive used for bonding was an epoxy reinforced with unidirectional and chopped glass fibres as well as micro-glass powder. The adherends were glass reinforced composite laminates. The bonding surfaces were prepared before joining. In the case of unidirectional fibres in the adhesive region, the fibre orientations considered were 0°, 45° and 90°. The volume fraction of fibres in the adhesive layer in all the cases was 30%. The volume fractions of micro-glass powder were 20%, 30% and 40%. The tensile, bending, impact and fatigue tests on the prepared specimens were conducted according to ASTM standards. The results show that except the 90° unidirectional orientation, reinforcing the adhesive with glass fibres or powder increases the joint strength. The use of volume fraction of 30% of micro-glass powder gave the best performance in the above loading conditions. The fatigue life increased by 125%, the ultimate joint strength in tension increased by 72%, the bending ultimate joint strength increased by 112% and the impact joint strength increased by 63%. The microstructure of the debonded area was examined and three modes of failure could be observed namely cohesive failure, light fibre-tear failure and thin layer cohesive failure.     

Glass/epoxy composites and aluminium alloy joint using Kevlar® intermediate layer and nanoclay-reinforced epoxy adhesive

Adhesive lap joint between glass fibre/epoxy composites and aluminium alloy (2014 T4) was prepared by an in situ moulding process using a matched die mould. The surface of aluminium alloy was treated with chromic acid before adhesive bonding. Lap shear strength and fatigue life were evaluated in tensile mode and tension–compression mode (at 40% of lap shear load of adhesive joint), respectively. Knurling on the surface of aluminium alloy improved the lap shear strength of the adhesive joint but did not influence the fatigue life of the same. Lap shear strength and fatigue life of adhesive joint made with neat epoxy adhesive and reinforcement of an intermediate layer of Kevlar^® between glass/epoxy composite and aluminium alloy were observed to be 0.44?kg/mm² and 3.6?×?10⁵ cycles, respectively. In another case, lap shear strength and fatigue life of similar type of adhesive joint made from nanoclay (Cloisite 30B)-reinforced epoxy adhesive and without reinforcement of an intermediate layer of Kevlar^® were observed to be 0.38?kg/mm² and 2.3?×?10⁵ cycles, respectively. Whereas, lap shear strength and fatigue life of adhesive joint made from nanoclay-reinforced epoxy adhesive along with the reinforcement of an intermediate layer of Kevlar^® were 0.48?kg/mm² and 3.9?×?10⁵ cycles, respectively. Therefore, adhesive joint made from nanoclay-reinforced epoxy adhesive along with the reinforcement of an intermediate layer of Kevlar^® was the best.     

Stress Distribution and Strength of T-type Adhesive Joint with Reinforcement for Bending Moment

The stress distribution in the adhesive layer of T-type adhesive-bonded butt joint between rigid adherends has been measured experimentally, and the equation relating the maximum stress in the adhesive layer to the bending moment applied to the joint and to the joint dimensions was derived. The equation is used to calculate the adhesive strength of a T-type joint from the measured breaking load. These strengths show reasonable agreement with experimental values.

The distribution in the adhesive layer of a T-type adhesive joint with the reinforcement having the section of a right-angled isosceles triangle has been measured experimentally. The strength efficiency of the reinforcement η and the strengthening magnification of the reinforcement μ are discussed geometrically comparing with the equation. The values of η and μ measured by the experiments showed good agreement with the values obtained geometrically.     

Bonded joints with through-thickness adhesive stresses – reinforcing the F/A-18 Y470.5 bulkhead

A bonded composite reinforcement is being developed for the Royal Australian Air Force F/A-18 Y470.5 bulkhead crotch region. Due to the curvature of the surface in this area any bonded reinforcement was predicted to have high through-thickness stresses present in the adhesive under load. A representative specimen, the “curved beam specimen” (CBS) was designed using finite element analysis to identify the stress state in the joint and determine the through-thickness stresses in the adhesive. The specimen was then mechanically tested to failure under static loads and also under spectrum fatigue loading to determine the viability of the repair. The data from the above program was used to determine an estimate for the through-thickness stress design allowable for the structural film adhesive Cytec FM73. It is suggested that the CBS will prove to be a suitable specimen for providing generic data on the through-thickness static and fatigue strength of adhesives.     

Effect of Temperature on the Quasi-static Strength and Fatigue Resistance of Bonded Composite Double Lap Joints

Fibre reinforced polymer composites (FRP's) are often used to reduce the weight of a structure. Traditionally the composite parts are bolted together; however, increased weight savings can often be achieved by adhesive bonding or co-curing the parts. The reason that these methods are often not used for structural applications is due to the lack of trusted design methods and concerns about long-term performance. The authors have attempted to address these issues by studying the effects of fatigue loading, test environment and pre-conditioning on bonded composite joints. Previous work centered on the lap-strap joint which was representative of the long-overlap joints common in aerospace structures. However, it was recognised that in some applications short-overlap joints will be used and these joints might behave quite differently. In this work, double-lap joints were tested both quasi-statically and in fatigue across the temperature range experienced by a jet aircraft. Two variants on the double-lap joint sample were used for the testing, one with multidirectional (MD) CFRP adherends and the other with unidirectional (UD) CFRP adherends. Finite element analysis was used to analyse stresses in the joints. It was seen that as temperature increased both the quasi-static strength and fatigue resistance decreased. The MD joints were stronger at low temperatures and the UD joints stronger at high temperatures. It was proposed that this was because at low temperature the strength was determined by the peak stresses in the joints, whereas, at high temperatures, strength is controlled by creep of the joints which is determined by the minimum stresses in the joint. This argument was supported by the stress analysis.     

Effect of Temperature on the Quasi-static Strength and Fatigue Resistance of Bonded Composite Double Lap Joints

Fibre reinforced polymer composites (FRP's) are often used to reduce the weight of a structure. Traditionally the composite parts are bolted together; however, increased weight savings can often be achieved by adhesive bonding or co-curing the parts. The reason that these methods are often not used for structural applications is due to the lack of trusted design methods and concerns about long-term performance. The authors have attempted to address these issues by studying the effects of fatigue loading, test environment and pre-conditioning on bonded composite joints. Previous work centered on the lap-strap joint which was representative of the long-overlap joints common in aerospace structures. However, it was recognised that in some applications short-overlap joints will be used and these joints might behave quite differently. In this work, double-lap joints were tested both quasi-statically and in fatigue across the temperature range experienced by a jet aircraft. Two variants on the double-lap joint sample were used for the testing, one with multidirectional (MD) CFRP adherends and the other with unidirectional (UD) CFRP adherends. Finite element analysis was used to analyse stresses in the joints. It was seen that as temperature increased both the quasi-static strength and fatigue resistance decreased. The MD joints were stronger at low temperatures and the UD joints stronger at high temperatures. It was proposed that this was because at low temperature the strength was determined by the peak stresses in the joints, whereas, at high temperatures, strength is controlled by creep of the joints which is determined by the minimum stresses in the joint. This argument was supported by the stress analysis.     

高强全聚丙烯复合板材的制备与性能研究

采用复合挤出与口模拉伸技术制备了共聚聚丙烯(coPP)/等规聚丙烯(iPP)自增强线材,以此为增强体、coPP为基体,经热压成型制备高强全聚丙烯复合板材,并考察其力学性能、动态力学性能、可回收性.结果表明,复合板材的拉伸强度和弯曲强度分别可达160 MPa和63 MPa;增强体的加入使板材的储能模量大幅度提高、损耗因子...     

Effect of adhesive thickness and surface roughness on the shear strength of aluminium one-component polyurethane adhesive single-lap joints for automotive applications

Adhesively bonded technology is now widely accepted as a valuable tool in mechanical design, allowing the production of connections with a very good strength‐to‐weight ratio. The bonding may be made between metal–metal, metal–composite or composite–composite. In the automotive industry, elastomeric adhesives such as polyurethanes are used in structural applications such as windshield bonding because they present important advantages in terms of damping, impact, fatigue and safety, which are critical factors. For efficient designs of adhesively bonded structures, the knowledge of the relationship between substrates and the adhesive layer is essential. The aim of this work, via an experimental study, is to carry out and quantify the various variables affecting the strength of single-lap joints (SLJs), especially the effect of the surface preparation and adhesive thickness. Aluminium SLJs were fabricated and tested to assess the adhesive performance in a joint. The effect of the bondline thickness on the lap-shear strength of the adhesives was studied. A decrease in surface roughness was found to increase the shear strength of the SLJs. Experimental results showed that rougher surfaces have less wettability which is coherent with shear strength tests. However, increasing the adhesive thickness decreased the shear strength of SLJs. Indeed, a numerical model was developed to search the impact of increasing adhesive thickness on the interface of the adherend.     

不同增强方式下泡沫夹芯复合材料三点弯曲性能研究

研究了缝合及加强筋增强方式下泡沫夹芯复合材料的三点弯曲性能.采用万能试验机分别进行了缝合与未缝合碳纤维、玻璃纤维、玻碳混杂纤维泡沫夹芯复合材料的三点弯曲实验,分别得出各自的载荷-挠度曲线,再引入加强筋的方式进一步研究缝合碳纤维泡沫夹芯复合材料的弯曲性能.结果表明,玻碳混杂纤维泡沫夹芯复合材料较玻璃纤维泡沫夹心复合材料性...     

Experimental evaluation of reinforcing the single lap joint in both longitudinal and transverse direction under tensile and bending condition

The effect of pins and wires as reinforcing elements in the single adhesive joints under tension and bending has been investigated in this study. Four types of joint specimens were made for this reason. Type one specimen, having no reinforcements and type two having 20 metallic wires of 0.2 mm diameter in longitudinal direction. Type three consist of 6 steel pins having 1 mm diameter in transverse direction. In type four, both the pins in transverse and wires in longitudinal direction have been used to reinforce the joint. After manufacturing of the samples, their tensile and bending properties were investigated. The results show that, pins increase bending strength and toughness during both tensile and bending while metallic wires increase tensile strength and modulus of joint. Overall, the sample with combined reinforcements has the highest tensile and bending properties apart from modulus. Since the weight of the reinforcements used are negligible, the specific properties of the joint has been improved significantly. The tensile specific strength and toughness of combined reinforced joint as compared to simple joint with no reinforcement has been improved by 33.48% and 82.52% respectively. Also in that case, the specific bending strength and toughness are improved by 64.4% and 231.91% respectively.