Laser-induced combustion joining of C_(f)/Al composites and TC4 alloy

The C_(f)/Al composites were joined to the TC4 alloy via the laser-induced combustion joining method.The exothermic reaction of the interlayer provided the required energy for the joining process.By combining the theoretical calculation and experiment,the chemical composition of the Ni−Al−Zr interlayer was designed.The microstructure and mechanical properties of the joint were investigated.The results show that the addition of Zr slightly weakened the combustion reaction of exothermic interlayer but played a key role in the successful joining.Ni−Al−Zr interlayer reacted with substrates,forming a TiAl_(3)layer adjacent to TC4 alloy and NiAl_(3),Ni_(2)Al_(3)layers adjacent to the C_(f)/Al composites.Zr content dominated the microstructure and shear strength of the joint.When the Zr content was 5 wt.%under the joining pressure of 2 MPa,the joint had a maximum shear strength of 19.8 MPa.

Characteristics of deformation joining of aluminum-stainless steel composite sheet

In order to study the characteristics of deformation joining of aluminum-stainless steel composite sheet, an applied example of this composite sheet was given. The conditions of the composite sheet were discussed, the optical micrographs and scanning electron micrographs were examined by contrast ways of deformation joining and braze joining. Simultaneously the analysis of energy spectrum was also conducted. The results indicate that the deformation joining composite sheet possesses high bonding strength, good corrosion resistance, less inclusions and less microcracks.

TiC Particle Reinforced Silicon Nitride Composite Joined With Y_2O_3-Al_2O_3-SiO_2 Mixture

Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .

Dimensioning of Punctiform Metal-Composite Joints: A Section-Force Related Failure Criterion

Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and fault-tolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.

Structural considerations in friction welding of hybrid Al_2O_3-reinforced aluminum composites

Comparative studies on the relationship between the welding parameters and joining efficiency in the friction welding of hybrid Al203-reinforced aluminum composites were conducted. Metal matrix composites （MMCs） with 37% （volume fraction） aluminum particle were joined by friction welding. The results show that the effects of the rotation speed on the reduction rate of particle size are greater than those of the upset pressure, and the area of the MMC weld zone decreases as the joining efficiency increases, while it is considered that the joining efficiency does not increase as the reduction rate of particle size decreases. During the macro-examination of the bonding interlace, a gray discolored region was observed on the bonding interface, and the center of the region was dark gray. After the micro-examination of the bonding interface, base metal made some second particulate formed by condensed alumina particulate but discoloration part distributed minute alumina particulate without second particulate. Consequently, it was also observed that rotational speed of 3 000 r/min and upset pressure of 63.6 MPa showed a very good.joint.

Damage Monitoring in Composite Stiffened Skin Using Fiber Bragg Grating under Tensile and Three-Point Loading

One of the problems associated with loading a fully composite structure with joints is that the loads are not linear through the neutral axis of the structure but are collinear; this induces additional moment and creates a load in the normal direction, which is typically a critical load because it can create delamination and can only be withstood if it is small. Another problem is that the structure is difficult to inspect using conventional methods because of limited accessibility. With fiber Bragg grating （FBG）, the problem can potentially be solved in structures with a stiffness mismatch. The model used to represent the problem above is a composite stiffened skin with two loading cases： tensile and three-point bending. Additionally, FBG is used to monitor and characterize the delamination caused by both loading cases. Finite element modeling （FEM） with traction versus separation theory is performed to determine the critical area on the specimen for placement of the FBG before manufacturing and testing. In this research, FBG can successfully monitor and characterize delamination caused by both loading cases in structures that have mismatched stiffnesses. Also, FBG can predict the delamination growth quantitatively. A spectrum graph of the FBG results can be used to replace a conventional mechanical graph for use in structural health monitoring.

Effect of Annealing on Fly-Line Microstructure and Properties of Explosively Composited Stainless Steel-Stainless Steel Plates

Effect of annealing on "fly-line"(adiabatic sheer line) microstructure and properties of explosively composited stainless steel-stainless steel plates was studied.Results show that the flyline microstructure will diminish through certain annealing process,while the cracks formed from fly-line microstructure will remain.Therefore,fly-line microstructure can be considered as a plastic deformation microstructure and crack source s meanwhile its formation is considered as a special plastic deformation mechanism of metal under explosive load.

JOINING OF Ni_3Al BY PRESSURIZED COMBUSTION SYNTHESIS USING GLEEBLE 1500 TEST SIMULATOR

In this investigation, the Gleeble 1500 test simulator was used for carrying out experiments of joining by the pressurized combustion synthesis (PCS). The intermetallic compound Ni3Al was bonded by us- ing the exothermic synthesis reaction of a mixture of element Ni and Al poweders pre - compacted as the interlayer material.Effects of the key process parameters, such as the heating rate and joining tem- perature as well as the hold time, on the joint formation and microstructural homogeneity were studied. The feasibility of the addition of Al2O3 particles in the joint interlayer for producing intermetallic -ma- trix composite joints are also explored. Results show that the microstructrual homogeneity in the synthe- sized joint interlayer was significantly influenced by the joining process paramenters.The fully synthesized Ni2Al joints exhibited an average tensile strength of 486MPa at R. T. With the addition of Al2O3 ce- ramic particles in the reactants, joints with reighrced Ni3Al - matrix composite interlayer were ob- tained.

船舶复合材料连接技术应用现状

由于纤维增强复合材料具有轻质高强等特性,因而在船舶领域得到了广泛应用。尽管整体化成型工艺日趋成熟,复合材料零部件之间依旧面临装配连接的问题,提高连接部位的力学性能是复合材料应用的关键。本文介绍了常用的连接技术,包括机械连接、胶接、混合连接,简述了这几种连接技术设计应用的关键。最后,对船舶复合材料连接技术进行了总结展望。

Recent advances in joining of SiC-based materials(monolithic SiC and SiC_f/SiC composites):Joining processes,joint strength, and interfacial behavior

Silicon carbide(SiC) has been widely concerned for its excellent overall mechanical and physical properties, such as low density, good thermal-shock behavior, high temperature oxidation resistance, and radiation resistance; as a result, the SiC-based materials have been or are being widely used in most advanced fields involving aerospace, aviation, military, and nuclear power. Joining of SiC-based materials(monolithic SiC and SiCf/SiC composites) can resolve the problems on poor processing performance and difficulty of fabrication of large-sized and complex-shaped components to a certain extent, which are originated from their high inherent brittleness and low impact toughness.Starting from the introduction to SiC-based materials, joining of ceramics, and joint strength characterization, the joining of SiC-based materials is reviewed by classifying the as-received interlayer materials, involving no interlayer, metallic, glass-ceramic, and organic interlayers. In particular, joining processes(involving joining techniques and parameter conditions), joint strength,interfacial microstructures, and/or reaction products are highlighted for understanding interfacial behavior and for supporting development of application-oriented joining techniques.

High-efficiency Joining of C_f/Al Composites and TiAl Alloys under the Heat Effect of Laser-ignited Self-propagating High-temperature Synthesis

The aim of this study was to develop a high-efficiency joining method of Cf/Al composites and TiA l alloys under the heat effect of laser-ignited self-propagating high-temperature synthesis（SHS）. The SHS reaction of Ni–Al–Zr interlayer was induced by laser beam and acted as local high-temperature heat source during the joining. Sound joint was obtained and verified the feasibility of this joining method. Effect of filler metals on the joint microstructure and shear strength was evaluated. When the joining pressure was 2 MPa with additive filler metals, joint shear strength reached the maximum of 41.01 MPa.

A review of friction stir joining of SiCp/Al composites

SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace,automotive industry and other fields.Due to the huge difference in performance between SiC particles and matrix alloys,traditional fusion welding methods are difficult to meet the join requirements of SiCp/Al composites.Friction stir joining(friction stir welding),as a solid phase joining process,has been proved to be a new technology with fine prospect in joining SiCp/Al composites compared with fusion welding process.Although some progress has been made in recent years,there are still full of challenges.In this paper,the research status of friction stir joining of SiCp/Al composites in recent years is expatiated,including the weldability of SiCp/Al composites,the macrostructure and the microstructure of joints,mechanical properties of joints,and tool wear and monitoring.Furthermore,the existing challenges of friction stir joining of SiCp/Al composites are summarized and the future development directions are prospected.

Joining of SiO2f/SiO2 composite to Nb using Ag-Cu-In-Ti brazing alloys

Three compositions of Ag-Cu-In-Ti system brazing alloys were designed for joining SiO2 f/SiO2 ceramic composite to Nb metal.The wettability of the three alloys on the composite was studied with the sessile drop method.The results showed that after heating at 1073 K for 30 min,they exhibited contact angles of 74°,83° and 86°,respectively.The brazing alloys were fabricated into foils by rapid solidification technique.Among the three brazing filler alloys the joints brazed with AgCu-10 In-5 Ti at 1073 K for 10 min presented the maximum average shear strength of 30.9 MPa.During the brazing process the active element Ti diffused strongly from the filler alloy to the composite surface and a reaction layer with a thickness of 2-3 μm was formed.Sound metallurgical bonding was also achieved at the Nb side.The interface structure of the joint brazed with the AgCu-10 In-5 Ti alloy can be described as the following sequence:SiO2 f/SiO2→SiO2+Cu3 Ti3 O→SiO2+TiO+Ti5 Si4→Ag(s,s)+(Cu-Ti)→Nb.However,for the filler alloy with 4.0 wt% Ti content the joint strength was only 15.8 MPa.

Self-propagating synthesis joining of C_(f)/Al composites and TC4 alloy using AgCu filler with Ni-Al-Zr interlayer

The successful joining of carbon fiber-reinforced aluminum matrix(C_(f)/Al)composites and TC4 alloy can produce composite structure and meet the demands of lightweight in aerospace field.Up to now,few experimental researches have been reported on the joining of C_(f)/Al composites and TC4 alloy.In this study,the AgCu foils and Ni-Al-Zr compact were designed for the self-propagating high-temperature synthesis joining of these two materials.C_(f)/Al composites were joined with a reactive Ti plated on its joining surface.The typical microstructure of TC4/(AgCu/Ni-Al-Zr/AgCu)/Ti/C_(f)/Al joint was analyzed,and the effects of joining condition on microstructural evolution of the SHS joint were investigated.A thin reaction layer of Ni-Al-Ti intermetallic compounds was formed adjacent to the TC4 alloy.As a result,AgCu foils could reduce the effect of reaction heat on the substrates and improve the joint shear strength.When the thickness of AgCu foils reaches 150 lm,the Ni-Al-Zr interlayer mainly acts as auxiliary heat source.High joining pressure caused the active elements to diffuse into C_(f)/Al composites and weakened the shear strength of the joint.Finally,the joint shear strength could reach 36.4 MPa when the AgCu foils were 50 lm and the joining pressure was 2 MPa.

Bending moment resistance of corner joints constructed with spline under diagonal tension and compression

We determined the effects of the penetration depth and spline material and composite material type as well as joining method on bending moment resistance under diagonal compression and tension in common wood panel structures. Composite materials were laminated medium density fiberboard （MDF） and particleboard. Joining methods were butt and miter types. Spline materials were high density fiberboard （HDF）. The penetration depths of plywood, wood （Carpinus betolus） and spline were 8, 11 and 14 mm. The results showed that in both diagonal com- pression and tension, MDF joints are stronger than particleboard joints, and the bending moment resistance under compression is higher compared with that in tension. The highest bending moment resistance under tension was shown in MDF, butt joined using plywood spline with 8 mm penetration depth, whereas under compression bending moment resistance was seen in MDF, miter joined with the HDF spline of 14 mm penetration depth.

碳化硅纤维增韧碳化硅陶瓷基复合材料研究进展综述

碳化硅纤维增韧碳化硅(SiC_(f)/SiC)复合材料具有优异的力学性能,以及耐高温、耐氧化、耐腐蚀、抗辐照和抗蠕变等一系列优点,在核能、航空航天、深海探测、轨道交通等诸多领域有着广阔的应用前景。从结构组成来看,SiC_(f)/SiC复合材料主要由三大结构单元组成:纤维、基体、界面相。高强度、近化学计量比、低氧含量碳化硅纤维的研制,是获得耐高温、耐氧化、抗辐照的碳化硅纤维增韧碳化硅陶瓷基复合材料的关键。裂解碳/碳化硅多层复合界面相在航空航天领域具有较好的应用前景,新型的RE_(3)Si_(2)C_(2)涂层在耐高温氧化方面具有潜在的优势,而三元层状过渡金属碳化物界面层则可能是未来制备核用SiC_(f)/SiC复合材料的候选方案之一。而SiC_(f)/SiC复合材料的制备工艺各具优劣,针对不同的应用环境,可选择不同的制备工艺,多种制备工艺联用在制备高致密高热导力学性能优异的复合材料方面具有显著优势。此外,由于SiC_(f)/SiC复合材料难以一次成型制备出复杂形状的大尺寸构件,因此,SiC_(f)/SiC复合材料的可靠连接技术也是其走向应用必须解决的关键问题之一。针对SiC_(f)/SiC复合材料的研究热点问题,概述了目前国内外关于SiC_(f)、界面相、复合材料的制备方法以及连接技术等研究进展,以期为同行研究者与工程技术人员提供参考。

聚合物基复合材料凸头螺栓连接研究进展

机械连接是聚合物基复合材料最典型的连接方式,因其在连接工艺性和可靠性方面的优势,使其在航空航天制造领域得到了广泛应用。对凸头螺栓连接聚合物基复合材料接头的研究进展进行综述。回顾了复合材料接头的机械连接形式,讨论了在拉伸加载下的失效过程,详细论述了复合材料接头的损伤模式;重点讨论了复合材料接头力学性能影响因素的研究进展,包括复合材料性能(纤维类型、增强体结构形式、纤维与金属混杂层板、铺层角度及比例、固化工艺、初始材料缺陷)、紧固件性能(紧固件刚度、钉头型式、螺栓直径、螺纹密封、间隙配合、干涉配合、紧固件缺失)、连接板性能、侧向约束(拧紧力矩、预紧面积、补偿垫片、接触面摩擦因素)、几何效应(复合材料板尺寸、板厚与孔直径比、层合板宽度与孔直径比、孔端距与孔直径比、螺孔形状、螺孔质量、螺孔位置误差)、载荷(静载荷、动态载荷、疲劳载荷、蠕变、松弛、温湿载荷)等;对聚合物基复合材料凸头螺栓连接的未来研究方向进行了展望。

铝/镁合金轴叉磁脉冲压接/胶接复合连接工艺与接头性能

面向汽车传动轴中轻量化材料的使用与连接需求,提出了一种6061-T6铝合金和AZ31B镁合金轴叉的磁脉冲压接/胶接复合连接工艺。通过改变放电次数、槽倾角和放电能量等工艺参数,对比分析了不同工艺下胶接接头、磁脉冲压接接头和磁脉冲压接/胶接复合连接接头力学性能的变化规律,并通过显微观测探究了不同试验参数对铝/镁合金接头性能的影响和机理。通过中性盐雾腐蚀试验观察了接头在不同周期下的腐蚀产物和形貌变化。结果表明,磁脉冲压接/胶接复合连接工艺能够实现镁合金和铝合金的高质量连接,放电能量25 kJ、槽倾角90°、放电3次时,接头最大扭矩达到1479.30 N·m;铝合金外管和镁合金槽底面的贴合区域长度随放电次数和槽倾角的增大而增加;胶粘剂的加入有利于降低接头的腐蚀速度。

核用SiC陶瓷基复合材料制备与连接研究现状

SiC陶瓷基复合材料因其优异的高温性能和核性能,极可能成为第四代反应堆包壳材料的候选材料之一。在核反应堆恶劣的服役环境下,制造出满足工业应用的SiC管较为困难,因此需要对其制备与连接进行研究。本文简述了目前用于核用SiC陶瓷基复合材料的制备工艺(化学气相渗透、先驱体浸渍裂解、和纳米渗透瞬态共晶工艺)以及对其连接工艺(钎焊、陶瓷先驱体连接、纳米浸渍瞬时液相连接与玻璃陶瓷连接)的研究现状,并对未来SiC陶瓷基复合材料在核应用中的前景进行了展望。

TC4/CFRTP叠层结构摩擦搭接焊接过程温度场研究

为了研究TC4钛合金与碳纤维增强热塑性复合材料(CFRTP)叠层结构摩擦搭接焊(friction lap joining,FLJ)过程中的温度变化及其影响,建立了摩擦热源以及热传导的三维几何模型。利用ABAQUS软件进行模拟,得到了FLJ过程的温度场及热循环曲线,分析了旋转速率和焊接速率等参量对温度场的影响规律。并进行了TC4/CFRTP摩擦搭接焊试验,通过连接区域的显微形貌观察分析了温度变化对焊接缺陷的影响。结果表明,模型能够快速、准确模拟TC4/CFRTP叠层结构FLJ过程的温度变化;旋转速率越大、焊接速率越小,则连接区域温度越高;过高的温度导致CFRTP的热塑性基体发生热降解,未能及时排出的热解气体在连接区域形成气泡,气泡数量及大小随温度升高而增多、增大。