硅烷偶联剂处理木塑复合材胶接接头的耐水性

利用硅烷偶联剂KH560对木粉/聚乙烯复合材料进行表面处理以改善其胶接性能。利用接触角、吸水量、表面形貌以及胶接强度测试等分析方法,研究了硅烷偶联剂处理聚乙烯木塑复合材料胶接接头在水环境中的胶接耐久性能。试验结果表明,机械打磨并偶联剂处理后,聚乙烯木塑复合材表面接触角增加,表面粗糙度增大,胶接强度和耐水性明显提高。偶联剂分子链上环氧基团的"架桥"作用以及甲氧基的憎水作用,是粘接强度和耐水性能提高的主要原因。浸水环境下,聚乙烯木塑复合材料表面粗糙度略有降低;随着浸水时间的延长,表面接触角下降,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成分的吸水膨胀,是造成胶接强度下降的主要原因。     

几种机械表面处理方法对6013铝合金接头胶接性能的影响

采用砂纸打磨、湿喷砂、纳米化等3种机械处理方法对6013铝合金表面进行处理,测试其粘接剪切强度,并与P2化学表面处理方法的结果进行对比。利用SEM、AFM、接触角测量仪等技术对铝合金表面处理前后的表面微观结构、微观粗糙度、润湿性等特性进行了研究。结果表明,不同的表面处理方法对铝合金接头的胶接性能影响不同。湿喷砂和砂纸打磨方法处理后铝合金接头的胶接性能与P2化学法表处的效果接近。纳米化方法不利于铝合金胶接性能的提高。微观粗糙度对铝合金的粘接性能具有重要影响,粗糙度越大,铝板胶接性能越好。润湿性不是影响胶接性能的关键因素。     

打磨对木粉/聚乙烯复合材料射流等离子体表面处理时效性的影响

采用空气气氛的射流等离子体对木粉/聚乙烯复合材料进行表面处理,以改善胶接性能。利用接触角和胶接强度测试以及红外光谱和X-射线光电子能谱分析等方法,研究了表面打磨对复合材料等离子体表面处理时效性的影响。研究结果表明,直接等离子体处理以及打磨后再等离子体处理都可以明显提高复合材料的胶接强度,相比之下,打磨后再等离子体处理可以在复合材料表面形成更多的含氧极性基团,有利于胶接性能的改善。木粉/聚乙烯复合材料的等离子体表面处理存在一定的时效性,与直接等离子体处理的复合材料相比,随着处理试样放置时间的延长,先打磨再等离子体处理的复合材料表面接触角、含氧极性基团以及胶接强度的变化幅度更小,表现出更小的处理时效性。尽管存在处理时效性,但等离子体处理后的胶接强度仍远好于未处理的试样。     

不同表面处理对铝合金-CFRP粘结性能的影响

胶接是铝合金和碳纤维增强复合材料(CFRP)的最有效连接方式之一。胶接接头的性能很大程度取决于基体表面,选择合适的表面处理方式能够提升胶接强度。针对目前铝合金—CFRP胶接强度弱的问题,研究了砂纸打磨和阳极氧化两种常用的胶接铝合金表面处理工艺,在此基础上提出了一种新型的喷砂和阳极氧化混合表面处理方式,有效且稳定地提升了铝合金-CFRP胶接接头性能,并通过表征分析进一步揭示了胶接性能提高的机理,发现新型的处理方式结合了机械处理和化学处理的优势,不仅仅能提升表面粗糙度,并且能提升表面氧化层厚度、降低表面污染层厚度,提升表面极性,提升表面能,最终提升接头的性能。     

不同表面处理方式对PEEK粘接强度的影响

采用砂纸打磨、喷砂和等离子处理等方式对PEEK进行表面处理,并使用环氧胶进行粘接。通过粗糙度仪、接触角测试仪和万能材料拉伸试验机对PEEK的粗糙度、润湿性和粘接强度等特性进行表征分析。结果表明,不同的表面处理方法对PEEK粘接的性能影响不同。砂纸打磨和喷砂能够有效增加PEEK表面的粗糙度,增大PEEK与粘结剂的粘接面积,从而提高PEEK的粘结强度。而等离子处理能够有效降低PEEK表面的接触角,改善PEEK表面的润湿性,提高PEEK的粘接强度,并且等离子处理后PEEK的粘接强度比未处理、砂纸打磨和喷砂分别提高了600%、260%和110%。     

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。     

CO2连续激光烧蚀CFRP树脂层工艺优化

碳纤维树脂基复合材料(CFRP)的激光表面处理是一项重要工艺，主要用于CFRP的胶接或修复。CFRP表面粗糙度和树脂清除程度是衡量加工效果的主要标准。为探索内在机理和优化连续激光表面处理的参数，开展CO₂连续激光烧蚀CFRP树脂层试验。通过点射试验确定最小离焦量激光半径为1 477.47μm，进行矩形表面处理试验发现，激光功率在30～60 W范围内的粗糙度先减小后增大并在60 W得到最大值，扫描速度为70 mm/s时得到最佳效果。同时对加工后CFRP表面起伏值计算发现，CFRP表面起伏值随功率和扫描速度变化的规律基本和粗糙度结果一致，功率和扫描速度两组参数是相互关联的。构造连续激光烧蚀树脂层的能量密度单元体，然后把参数转化为能量密度发现，能量密度为0.285～0.571 J/mm²范围内进行处理得到质量效果较好的表面，而且在0.571 J/mm²时粗糙度得到最大值7.816μm，清洗后仍保持可以用于胶接的较高粗糙度。此外，通过不规则图形扫描试验发现，能量密度为0.794 J/mm²得到最佳表面效果。...     

激光处理对民机复合材料胶接维修母体表面自由能的影响研究

胶接维修是民机碳纤维增强树脂基复合材料(CFRP)结构的重要维修方式。基于界面结合理论角度,复合材料维修母体表面的微观结构、物理、化学特征将直接影响胶接界面结合强度及维修效果。论文采用激光技术对母体表面进行预处理,主要探讨激光处理前后母体表面接触角与表面自由能的变化规律,并基于静电吸附理论分析表面自由能变化对界面结合强度及胶接维修效果的影响。结果表明,激光处理后母体表面质量更为稳定可靠,表面接触角明显下降,而表面自由能增加,有效改善了维修母体的表面活性,以利于胶接维修界面强度及维修效果。     

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。     

直升机桨叶包片胶接前激光毛化处理的有效性研究

为提升直升机桨叶包片胶接质量,开展激光毛化技术在不同材料包片胶接前表面处理工艺中的有效性研究.分别对经酸洗、喷砂、激光毛化工艺处理后的钛合金、不锈钢、纯镍金属材料试件,进行外观、粗糙度、微观形貌检测,并在胶接后进行浮辊剥离试验、剪切强度试验,结果表明:激光毛化处理可在金属表面获得规则的微观形貌,且试件无变形现象,与喷砂表面同等级粗糙度下,浮辊剥离值及剪切强度明显高于喷砂或酸洗处理的表面,可有效提升胶接结合强度.     

Effect of surface cold ablation on shear strength of CFRP adhesively bonded joint after UV laser treatment

Ultraviolet(UV) laser treatment on the surface of the carbon fiber reinforced polymer (CFRP) laminate becomes an effective method to benefit the bonding strength of adhesively bonded joint in aerospace industries. In the present research, homomorphic CFRP laminates with different resin distribution on the surface are bonded into single-lap joints. Their shear strengths are tested to evaluate the effect of surface resin distribution on bonding mechanical performance. The different resin distributions on the surface of CFRP laminate are obtained by UV pulse laser with different laser scanning speeds. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are conducted to analyze the laser treated surfaces and fracture surfaces of tested joints. The experimental results indicate that the residual resin of CFRP surface increases with the increase of scanning speed. Compared with both the reference surface without laser pre-treatment and that with no-residual resin for bonding, the surface with partial residual resin results in an enhancement of the shear strength of bonded joint. Moreover, the shear strength of the reference sample is higher than that bonded by the surface with no-residual resin. The research lays foundation for understanding the relationship between surface resin distribution and bonding strength.     

Investigation of accumulated laser fluence and bondline thickness effects on adhesive joint performance of CFRP composites

In the present study, both the effects of accumulated laser fluence as surface treatment and bondline thickness on adhesive bonding of carbon fiber reinforced polymer (CFRP) composite materials were investigated. Proper CFRP composite surfaces for adhesive bonding were obtained by a laser treatment process using pulsed CO₂ laser. Laser treatments were obtained with different accumulated laser fluences and then surfaces were analyzed with roughness and contact angle measurements. Adhesive bonding was performed with various bondline thicknesses ranged between 30–500 µm using two component structural epoxy based paste adhesive (Loctite Hysol ® EA 9396^TM). Adhesive bonding strength of bonded samples was determined with single lap shear tests. It is worthy to note that if the accumulated laser fluence which has significant effect on shear strength does not optimize, it causes ineffective adhesion.     

单向碳纤维增强塑料磨削加工性能

碳纤维增强塑料因具有优异的力学性能,在航空航天等领域有重要应用。通过单向碳纤维增强塑料(CFRP)的平面磨削实验,研究了塑料增强方向对CFRP磨削加工性能的影响。研究发现,单向塑料基复合材料磨削时,由于纤维增强塑料的各向异性,磨削力与加工表面粗糙度均呈现明显的规律性。其中,在加工参数砂轮转速为1500 r/min,进给速度为5 m/min和切削深度50μm的条件下,最大和最小磨削力分别为42和10 N,而且,磨削力符合规律:法向>纵向>横向。通过对磨削加工表面显微形貌的分析,揭示了塑料基复合材料磨削微观多向材料的去除机理。研究结果不仅对拓展CFRP的应用具有重要的经济意义,同时,能够为复合材料精密加工提供一定的理论和实验支撑。     

C型炭纤维阳极氧化处理及其增强ABS复合材料的研究

以NH4NO3为电解质,对C型通用级沥青基炭纤维在不同条件下进行阳极氧化表面处理,并通过SEM、力学性能测试等方法考察了纤维及其复合材料的性能,发现经氧化处理后,炭纤维表面粗糙度和含氧官能团如C-O、C=O、COOH等数目明显增大,CF/ABS复合材料的界面粘结性得到有效地改善;复合材料的拉伸强度、弯曲强度及模量有所提高,断裂形式由纤维拔出转变为纤维断裂。     

Adhesive bonding of CFRP: a comparison of different surface pre-treatment strategies and their effect on the bonding shear strength

A promising joining technology for thermoset CFRP is adhesive bonding. However, the mechanical performance is influenced negatively by contaminants, like release agents, as well as an excess of matrix in the top layer. In order to generate most suitable surface qualities prior to the bonding process, carbon fibre reinforced plastics are treated with different – UV (355 nm) and IR (1064 nm) – lasers. The results are compared to commonly applied grinding surface preparation. The preliminary results on surface properties, e.g. energy and topography point towards high levels of free surface energy, as well as new originated surface structures. After the bonding process mechanical tests are subsequently carried out in Mode II, to characterize the final joint by its tensile shear strength. Finally, the individual fracture behaviour is examined in post mortem analysis. The results indicate that it is possible to increase the tensile shear strength of the joints to a maximum, which equals the interlaminar shear strength of the CFRP-laminate. Therefore, ultrashort pulsed IR-laser techniques show the best reproducibility and the highest tensile shear strength. In addition, IR-laser treatment is expected to have the highest potential for later applications.     

Study on ultrasonic vibration-assisted adhesive bonding of CFRP joints

As adhesive bonding does not disrupt the continuity of the fiber integral, it has become an important bonding method of CFRP (carbon fiber-reinforced plastics) joints. Regarding the quality problems in the traditional adhesive bonding process, i.e. the low and unstable adhesion strength, a novel ultrasonic vibration-assisted adhesive bonding method for CFRP joints is proposed. In this method, extra force caused by ultrasonic vibration is introduced into the bonding process to reinforce it. The strengthening mechanism is then analyzed. According to our study, it is found that: (1) ultrasonic vibration can improve the adhesion strength and stability by 52 and 66% in the test. (2) The strengthening mechanism is summarized as: high-frequency vibration contact between adhesive and wall is produced under ultrasonic vibration, which forms better contact; adhesive is driven to penetrate into the surface roughness of the bonding area under ultrasonic vibration, which increases the effective bonding area.     

Laser ablation surface preparation for adhesive bonding of carbon fiber reinforced epoxy composites

Adhesive bonding of carbon fiber reinforced plastic (CFRP) epoxy composites provides many advantages over mechanical fastening for assembling aerospace structures including weight savings, reduced manufacturing flow, and added structural efficiency. To ensure the reliability of bonded joints in primary airframe structures, the surface preparation method and execution are critical. Surface preparation is widely recognized as a key step in the bonding process and is one element of a bonding method that must be controlled to produce robust and predictable bonds in a precise and repeatable manner. Laser ablation of composite surface resin can provide an efficient, precise, and reproducible means of preparing composite surfaces for adhesive bonding. Advantages include elimination of physical waste (i.e., grit media and sacrificial peel ply layers that ultimately require disposal), reduction in process variability due to increased precision (e.g. monitoring laser parameters), and automation of surface preparation. This paper describes a surface preparation technique using a nanosecond, frequency-tripled Nd:YAG laser source. Lap shear specimens were laser treated and tested and apparent shear strength and failure modes of lap shear specimens were used to assess mechanical performance over a three-year accelerated aging study by exposing bonded specimens to 71 °C (160 °F) and 85% relative humidity.     

Comparative behavior under compression of concrete columns repaired by fiber reinforced polymer (FRP) jacketing and ultra high-performance fiber reinforced concrete (UHPFRC)

This paper summarizes the experimental results from a comprehensive research program to study the fundamental stress–strain behavior of damaged concrete repaired by two techniques: increased concrete section and bonding fiber reinforced polymer (FRP). In this work, two types of FRP composite jackets were used, carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer, and two types of concretes were used to repair the damaged concrete by increased concrete section: ordinary concrete and ultra high-performance fiber reinforced concrete (UHPFRC). Fifteen circular columns of concrete (110 × 220) cm³ were initially pre-damaged up to intense cracking, repaired by increased concrete section and by bonding FRP, and tested under uni-axial compression by loading up the damage. The impact of different design parameters, including plain concrete strength, types of composites, and type of concrete used for increasing section, was considered in this study. The strength enhancement and ductility improvement of specimens are discussed. A simple model is presented to predict the compressive strength of repaired damaged concrete columns. A significant strength and an increase in ductility were achieved, particularly when the columns were repaired by increasing section with UHPFRC and by bonding CFRP. These preliminary tests indicate that the use of UHPFRC is an effective technique for rehabilitating damaged concrete columns, highly competitive with the repaired concrete by wrapping specimens with FRP composite jackets.     

Evaluation of the CFRP grafting and its influence on the laser joining CFRP to aluminum alloy

In the case of laser direct joining carbon fiber reinforced plastic (CFRP) to A6061 aluminum alloy, the strength of the dissimilar joint is low. The UV grafting of acrylic acid was proposed to modify the CFRP surface before the laser joining process. The result showed that the shear strength of the joint could be enhanced from 5.3 to 30.1 MPa when optimized parameters (irradiation distance: 10 mm; irradiation time: 30 s) of UV grafting were applied. X-ray photoelectron spectroscopy and scanning electron microscope were applied to study the surface characteristic of grafted CFRP and the strengthening mechanism of the grafting modification. The C=O bond and O–C=O bond on the CFRP increased after the modification with UV grafting. It could be figured out that new chemical bonds, including Al–C and Al–O–C, were produced between Al and the matrix resin of the CFRP and it played a key role in improving the strength of grafted CFRP/A6061 dissimilar joint. Thus, as a high-efficient and effective technique, UV grafting is a promising method to improve the laser joining CFRP to aluminum.     

聚乙二醇/氯化锌条件下回收CFRP方法研究

以真空辅助成型工艺(VARI)制作的碳纤维增强复合材料(CFRP)平板件为降解试件,使用乙酸对其进行分层预处理,然后以聚乙二醇为溶剂,氯化锌为催化剂,采用控制变量法在不同的反应温度、反应时间,氯化锌浓度等工艺参数下对CFRP进行降解回收。利用扫描电子显微镜、X射线光电子能谱仪、动态接触角测量仪、纤维强度仪对回收碳纤维的表面形貌和元素、浸润性以及力学性能进行表征分析。结果表明,CFRP降解的理想工艺条件为:用乙酸于120℃下分层预处理30 min,然后在190℃下,使用浓度为0.6 mol/L氯化锌/聚乙二醇环境反应60 min。使用该方法回收的CFRP,树脂降解率能达到98%以上,碳纤维表面干净光滑无树脂残留,表面元素与原丝相比变化较小,碳纤维和水与乙二醇的浸润性相比原丝得到改善,碳纤维的弹性模量达到原丝的98%以上,拉伸强度达到原丝的97%以上。