体育器械用复合材料的界面粘结性能研究

采用线性T1胶粘剂和非线性T2胶粘剂对体育器械用碳纤维增强复合材料/钢进行了粘结,考察了温度交变次数对拉伸性能和剪切性能的影响。结果表明,温度交变次数对碳纤维增强复合材料的拉伸性能影响较小,即温度交变处理不会显著恶化碳纤维增强复合材料的拉伸性能;温度交变次数对碳纤维增强复合材料的短梁剪切强度的影响较小,且不同温度交变次数下碳纤维增强复合材料的破坏模式都表现为碳纤维复合材料与钢板界面的层间剪切破坏。随着温度交变次数从0增加至500次时,温度交变次数不会对T1粘结件的拉伸强度产生明显影响,T1胶粘剂的弹性模量呈现逐渐减小趋势;随着温度交变次数从0增加至500次时,T2胶粘剂的拉伸强度呈现逐渐降低的趋势,温度交变次数不会对T2胶粘剂的弹性模量造成明显影响。T1胶粘剂的界面破坏形式主要为碳纤维增强复合材料的层间剪切破坏,而T2胶粘剂的界面破坏形式为层间剪切破坏和非粘结区断裂。     

风电叶片用胶粘剂剪切疲劳性能和蠕变性能分析

简述了胶粘剂在风电叶片中的重要性,风电叶片大多采用环氧胶粘剂。从叶片的设计需求角度,对比测试了国产胶粘剂和进口胶粘剂的玻璃化转变温度、剪切疲劳和蠕变性能,并对两种胶粘剂的粘接断面进行形貌扫描,简单分析得出:进口胶粘剂的粘接断面是比较典型的韧性断裂,国产胶粘剂的粘接断面呈现韧性和脆性结合体;提高胶粘剂的韧性,并不断改良增韧体系和环氧树脂基体的相容性是国产胶粘剂亟待解决的问题。     

表面内嵌FRP筋混凝土粘结-滑移本构关系试验研究

通过对一组表面内嵌FRP筋混凝土试件进行拉拔试验,分析表面内嵌FRP筋混凝土的受力过程和破坏模式;研究FRP筋直径、粘结长度和FRP筋类型等因素对粘结滑移性能的影响。结果表明,试件的破坏模式表现为FRP筋与结构胶界面破坏、结构胶与混凝土界面剥离、FRP筋被拉断和结构胶劈裂四种破坏模式;内嵌BFRP筋试件的粘结应力随粘结长度的增长而增大,而内嵌GFRP筋试件的粘结应力随粘结长度的增长而减小。因FRP筋泊松比的降低和剪切滞后效应,试件的粘结应力随着FRP筋直径的增大而减小。同时,对试验结果进行处理分析,建立了一种适用于表面内嵌FRP筋混凝土粘结-滑移本构关系模型,并给出模型特征点的数学表达式,将拟合曲线与试验曲线进行对比分析。结果表明,该本构关系能够较为准确地模拟表面内嵌FRP筋混凝土的粘结滑移性能。     

振动注塑PP/CaCO3的拉伸蠕变研究

采用自制的机械振动注塑机,在不同振动频率和振动压力下成型PP/CaCO3试样.考察了试样的拉伸蠕变.结果表明,当振动压力一定时,PP/CaCO3的拉伸应变随着振动频率的增加先增大后减小,当振动频率为15 Hz时达最大;而当振动频率一定时,材料的拉伸应变随着振动压力的增大而减小.通过对不同成型条件下注塑的PP/CaCO3材料进行了短时拉伸实验和动态力学性能测试,从材料柔性和刚性分析其蠕变原因.     

PE100管及其热熔接头的蠕变裂纹扩展行为

聚乙烯(PE)管性能优异,广泛应用于城市水及燃气供应系统。PE管的主要破坏形式是长期静压载荷下的慢速裂纹扩展失效。在蠕变条件下,采用光滑试样和裂纹圆棒试样对PE100管及其热熔接头进行了测试,得到了基于蠕变断裂参数C*的蠕变裂纹扩展动力学关系式。利用扫描电子显微镜(SEM)分析了裂纹圆棒试样的断面形貌,对比分析结果发现,蠕变裂纹扩展失效模式对应的最大应力为15.05 MPa,热熔接头熔合面分布有约11个/mm^2、直径范围为1~5μm的微气孔,热熔接头断裂微纤平均长度比母材约小20%~45%。当热熔对接时,熔合面存在的微气孔以及系带分子的浅渗透是导致PE100热熔接头蠕变裂纹扩展抗力降低的主要原因。     

均苯四甲酸酐固化聚丁二烯环氧树脂胶粘剂的研究

采用均苯四甲酸酐(PMDA)固化聚丁二烯环氧树脂(ELPB),制备了ELPB/PMDA耐高温胶粘剂,并使用傅里叶红外光谱仪(FT-IR)、热重分析仪(TGA)、拉力机和数码显微镜对固化产物的性能进行了表征。实验结果表明,在200℃固化2h的条件下,PMDA可以对ELPB成功地固化;固化后的胶粘剂具有良好的耐热性能,其失重3%时的分解温度为300℃;该胶粘剂对铝/铝合金的粘接强度达到15MPa;剪切破坏是以内聚破坏为主的混合破坏,表明该胶粘剂对金属有较好的粘接性能。     

高性能桥梁混凝土裂缝修复胶的制备及性能研究

以高流动性的芳香胺(H-113)为主固化剂,聚酰胺树脂(PA)为辅助固化剂及增韧组分,经硅烷偶联剂(KH-792)表面改性的高活性石墨烯(MGE)为触变组分,以硅微粉、纳米碳酸钙及短切碳纤维为增稠及增强组分,制备了一种在高温环境下仍保持较长的施工适用期,并兼具触变性、高强度、刚性及一定韧性的高性能环氧树脂(EP)结构胶。研究结果表明:该结构胶的适用期为80 min,1 d压缩强度为65 MPa,14 d压缩强度为84 MPa,14 d拉伸强度为32 MPa,14 d剪切强度为17 MPa,且其与混凝土界面的14 d正拉粘接强度为5.6 MPa(界面破坏形式为混凝土内聚破坏),可完全满足GB 50728—2011标准中的指标要求。     

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。     

缓凝型环氧树脂建筑结构胶的制备与性能研究

以高活性酚醛胺(T-31)为主固化剂、聚酰胺树脂(PA)为辅助固化剂及增韧改性组分、气相白炭黑为触变改性组分,以水泥、超细石英砂及石棉纤维为增稠及增强改性组分,制备了高温施工适用期较长、触变性较好、强度较高及韧性较佳的EP(环氧树脂)建筑结构胶。研究结果表明:该结构胶的适用期为75min,并且垂直施工无流淌现象;该结构胶的1d压缩强度为60MPa、14d压缩强度为80MPa、14d拉伸强度为35MPa、14d剪切强度为17MPa且其与混凝土界面的正拉粘接强度为6.0MPa(界面破坏形式为混凝土内聚破坏),完全满足GB50728—2011标准中的指标要求。     

将动态应力和静态应力相结合研究环氧胶粘剂的热─力学性能

本文研究了动态应力和静态应力在加对环氧胶粘剂力学和热学性能的影响．在玻璃化温度范围内把剪切蠕变和扭力摆动同时作用于胶接接头，会使接头的剪切强度增大，胶粘剂的玻璃化转变温度升高．在接近胶粘剂的玻璃化转变温度Ｔｇ时施加相同的负载应力．对上面提到的胶接接头性能会产生相反的作用．本文研究中所选用的整个温度范围内，对各种环氧组成物，胶粘剂从玻璃态到高弹态转变宽度的增加均是由动态度力在加作用产生的．我们认为进行应力实验时，聚合物网络变硬而使玻璃化转变加宽．发现在温度低于Ｔｇ，试验前空动态应力和静态应力且加支配作用的试样的第一次ＤＳＣ扫描吸热线的面积和接头强度是线性关系，观测的结果与文献数据相一致，树脂的玻璃化转变温度（由ＤＳＣ扫描图上第一峰测得）和接头的剪切强度呈线性关系．由实验观测的结果和一些有关文献可知，要想提高胶接强度又改变胶粘剂的耐热性，主要采取使用状链小范围内取向以及增子内网络强极性点间的相互作用等物理方法．文中讨论了应力叠加会有改变化学交联的可能性，但未见有这种变化发生．     

Numerical study of the effect of carbon fiber/epoxy resin adhesive thickness on the creep behaviour of carbon steel plate joints

Nowadays, the use of adhesive and adhesively bonded joints have been considerably appreciated in the industry due to the dramatic reduction in bonding strength, reduced stress concentration, rust prevention, uniform bonding of the bonding surface and a significant reduction in costs compared to other types of permanent joints such as welding. In this study, the effect of adhesive thickness on creep behaviour of a single lap adhesive joint with the aid of Abaqus FEM software is investigated. It should be noted that the two-layer and two-dimensional models are considered, in which their adhesive layer is made of a reinforced epoxy resin with 0.5% carbon fiber and the adherend layers are made of carbon steel plates, which is affected by tensile forces. Since the main purpose of this paper is to study the effect of adhesive thickness on the adhesive joints behaviour, the effects of the distribution of shear stress, effective stress and creep strain were studied in different thicknesses of the adhesive layer. The results show that by increasing the thickness, the stress and the creep strain decrease, and over time, the stress decreases and the creep behaviour of adhesives increases.     

Rheological modeling and finite element simulation of epoxy adhesive creep in FRP-strengthened RC beams

We have shown that a significant creep occurs at the concrete–fiber reinforced polymer (FRP) interface based on double shear long-term test. The primary test parameters were the shear stress to ultimate shear strength ratio, the epoxy curing time before loading as well as the epoxy thickness. The test results showed that when the epoxy curing time before loading was earlier than seven days the shear stress level significantly affected the long-term behavior of epoxy at the interfaces, and in particular the combined effect of high shear stress and thick epoxy adhesive can result in interfacial failure if subjected to high-sustained stresses. In this paper, based on the previous experimental observations, an improved rheological model was developed to simulate the long-term behavior of epoxy adhesive at the concrete–FRP interfaces. Furthermore, the newly developed rheological creep model was incorporated in finite element (FE) modeling of a reinforced concrete (RC) beam strengthened with FRP sheets. The use of rheological model in FE setting provides the opportunity to conduct a parametric investigation on the behavior of RC beams strengthened with FRP. It is demonstrated that creep of epoxy at the concrete–FRP interfaces increases the beam deflection. It is also shown that consideration of creep of epoxy is essential if part or the entire load supported by FRP is to be sustained.     

Photoelastic Stress Analysis of Bonded Lap Shear Joints Having Thermoplastic Adherends

The effects of substrate stiffness and modulus on joint strength and stress distribution were investigated for a series of nylon substrates bonded with an epoxy adhesive. Substrate stiffness and modulus were controlled by the level of glass filler in the resin. Single lap shear samples having both identical (“self-bonded”) and dissimilar (“cross-bonded”) substrates were investigated. For the self-bonded samples, lap shear strength was found to increase with increasing substrate modulus and stiffness. The strengths of the cross-bonded samples were intermediate to the strengths of the corresponding self-bonded samples. Photoelastic techniques were used to observe stress patterns in the lap joints during testing. One type of stress pattern was observed for all self-bonded samples regardless of substrate stiffness. Two patterns, one for the stiff substrate and one for the more flexible substrate, were observed for cross-bonded samples. The photoelastic analysis agreed qualitatively with predictions of stress distributions based on linear elastic and linear elastic/perfectly plastic theoretical models.     

Effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy

The effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy were investigated. Primer coating improved the shear strength between anodized Ti alloy and epoxy by up to 81.3% using concurrent curing compared with that of control specimens. After annealing of anodized Ti alloy and applying primer, the shear strength of the specimen was further increased by 6.4% due to the formation of stable TiO₂ transferred from TiO in the anodization process. SEM analysis revealed the specimen without primer and annealing treatments showed adhesive failure between epoxy–alloy interface and discontinuous cohesive failure of epoxy. Primer coating initiated a new interfacial failure mode between the oxide layer and alloy due to the improved bonding strength between epoxy and oxide layer. In addition, annealing and primer treatments generated large tracts of epoxy continuous cohesive failure, showing good agreement with its higher shear strength and work of fracture.     

低模量硫化硅橡胶粘接研究

采用sol—gel工艺自制的SiO2补强增韧环氧树脂作为胶粘剂，对低模量硫化硅橡胶与金属或复合材料进行粘接试验，分析胶粘剂中SiO2理论含量及粘接工艺对粘接性能的影响，并把硫化硅橡胶放在改性环氧树脂中进行溶张试验，探索胶粘剂对硅橡胶的粘接机理、结果表明，随着SiO2先驱体-有机硅烷含量的增加，硅橡胶的溶胀程度提高改性环氧树脂胶粘刺能浸入硅橡胶的表层，对硅橡胶具有良好的亲和力。用该胶粘剂对硅橡胶与金属或复合材料进行粘接时，取得了良好的粘接效果。     

Analysis of the nonlinear creep behavior of concrete/FRP-bonded assemblies

This paper investigates the creep behavior of adhesively bonded concrete/fiber-reinforced polymer (FRP) joints, through experimental and modeling approaches. The first part proposes a methodology for predicting the long-term creep response of the bulk epoxy adhesive; such a procedure consists of (1) performing short-term tensile creep experiments at various temperatures and stress levels, (2) building the creep compliance master curves according to the time–temperature superposition principle in order to assess the long-term evolution for each stress level, and (3) developing a rheological model whose parameters are identified by fitting the previous master curves. In our case, it was found that master curves (and, consequently, parameters of the rheological model) are dependent on the applied stress level, highlighting the nonlinear creep behavior of the bulk epoxy adhesive. Therefore, evolution laws of the model parameters were established to account for this stress dependence. The second part focuses on the creep response of the concrete/FRP assembly in the framework of a double lap joint shear test configuration. Experiments showed that creep of the adhesive layer leads to a progressive evolution of the strain profile along the lap joint, after only one month of sustained load at 30% of the ultimate strength. Besides, a finite element approach involving the abovementioned rheological model was used to predict the nonlinear creep behavior of the bonded assembly. It confirmed that creep modifies the stress distribution along the lap joint, especially the stress value at the loaded end, and leads to a slight increase in the effective load transfer length. This result is of paramount interest since the transfer length is a key parameter in the design of FRP-bonded strengthening systems. Moreover, instantaneous and long-term calculated strain profiles were found in fair agreement with experimental data, validating the modeling approach.     

一种低蠕变单组分应变胶的研制

为便于在应变计贴片量少的场合下使用,根据对应变计贴片胶（以下简称应变胶）的性能要求,研制了一种单组分应变胶,其蠕变小,粘接强度高,粘贴工艺简单,贮存期长,完全达到粘贴应变计的使用要求。介绍了应变胶的制备原理、配方和制备工艺。讨论了双酚A型环氧树脂相对分子质量、F-44酚醛环氧树脂用量、聚乙烯醇缩醛用量、固化剂用量、固化条件等因素对粘贴后应变计蠕变和剪切强度等性能的影响。将该单组分应变胶与国内某种双组分应变胶进行了性能对比测试,结果表明,该单组分应变胶具有良好的低蠕变特性。     

Photoelastic Stress Analysis of Bonded Lap Shear Joints Having Thermoplastic Adherends

The effects of substrate stiffness and modulus on joint strength and stress distribution were investigated for a series of nylon substrates bonded with an epoxy adhesive. Substrate stiffness and modulus were controlled by the level of glass filler in the resin. Single lap shear samples having both identical (“self-bonded”) and dissimilar (“cross-bonded”) substrates were investigated. For the self-bonded samples, lap shear strength was found to increase with increasing substrate modulus and stiffness. The strengths of the cross-bonded samples were intermediate to the strengths of the corresponding self-bonded samples. Photoelastic techniques were used to observe stress patterns in the lap joints during testing. One type of stress pattern was observed for all self-bonded samples regardless of substrate stiffness. Two patterns, one for the stiff substrate and one for the more flexible substrate, were observed for cross-bonded samples. The photoelastic analysis agreed qualitatively with predictions of stress distributions based on linear elastic and linear elastic/perfectly plastic theoretical models.     

Shear creep behaviour of elastomeric adhesives

The shear creep behaviour of elastomeric adhesives has been investigated at various temperatures, loading stresses and adhesive thicknesses. Three adhesive types were included in the study: two polysulphides, one silicone and one polyurethane elastomer. The creep compliance of the two polysulphide adhesives could be described by an Arrhenius-type relationship incorporating time, temperature and stress. The silicone and polyurethane adhesives, on the other hand, showed an initial creep response followed by a long period of zero creep over the ranges of temperature and load studied.     

Investigation of the creep behavior of graphene oxide nanoplatelet-reinforced adhesively bonded joints

In this paper, the effect of adding graphene oxide nano-platelets (GONPs) into the adhesive layer was investigated on the creep behavior of adhesively bonded joints. The neat and GONP-reinforced adhesive joints were manufactured and tested under creep loading with different stress and temperature levels. 0.1?wt% GONPs revealed the highest improvement on the adhesive joint creep behavior amongst the studied weight percentages. Furthermore, the effect of GONPs on the creep behavior of adhesive joints was more significant at higher temperatures. It was found that adding 0.1?wt% of GONPs into the adhesive layer imposed reductions of 21%, 31% and 34% in the elastic shear strains and reductions of 24%, 31% and 37% in the creep shear strains of SLJs under testing temperatures of 30, 40 and 50?°C, respectively. The Burgers rheological model was employed for simulating the creep behavior of the neat and GONP-reinforced adhesive joints. The Burgers model parameters were obtained as functions of testing temperature, creep shear stress and GONP weight percentage using a response surface methodology. Reasonable agreement was obtained between the modeled and experimental creep behaviors of the adhesive joints.