补片形状对复合材料胶接贴补修补影响的预测与试验研究

为研究复合材料胶接贴补方法的修补性能,对胶接结构开展了准静态拉伸试验,研究了室温下T9001复合材料胶接修补结构的静拉伸载荷-位移行为。以三维逐渐损伤理论为基础,创建了复合材料胶接修补模型,利用APDL语言实现对不同补片形状的胶接修补结构在静拉伸载荷作用下的最终失效载荷的预测分析。同时,进行相关试验,测得的胶接修补结构的失效载荷与预测结果吻合较好。结果表明,正放的方形补片的修补效果最佳。最后利用X光机对胶接修补结构的最终损伤模式及损伤范围进行了检测,试验结果与计算预测结果较吻合。     

某型中翼前梁修补结构的剩余强度研究

为确定某型复合材料中翼结构在胶接修补后的剩余强度,以层合板渐进损伤理论为基础,建立了复合材料胶接修补有限元模型,研究了搭接长度与补片厚度对中翼修补结构压缩强度的影响.对前梁胶接修补结构进行限制载荷试验,并比较中翼前梁裂纹周围结构在修补前后的应力应变,结果显示,选择阶梯型搭接修补方式,在补片铺层层数为22层,搭接长度为3...     

胶层Ⅰ/Ⅱ型断裂破坏内聚单元参数的确定和应用

建立了铝合金板单搭接胶接接头的三维弹性有限元模型,通过与G-R解析模型的胶层剪应力和剥离应力分布对比分析,验证了有限元模型的有效性。经有限元仿真拟合铝合金板单搭接胶接接头静拉伸试验的载荷-位移曲线,获得了胶层Ⅰ/Ⅱ型混合失效模式下内聚力单元的断裂参数值和胶层渐进破坏的过程,将胶层内聚力单元断裂参数值应用于含双裂纹复合材料胶接修补结构中,预测了修补结构的静拉伸强度。结果表明,有限元模型预测的剩余强度与实验值的相对误差为3.8%,因此运用内聚力单元仿真胶层的方法是有效的,并为复合材料胶接修补结构的承载能力分析提供了有力的依据。     

金属损伤结构的复合材料修补技术研究

概述了金属损伤结构的三种主要修补技术,重点介绍了复合材料胶接修补技术的影响因素,包括金属结构的表面处理、复合材料补片材料、胶粘剂和修复工艺,并分析了复合材料修补金属结构的应用现状.     

复合材料胶接修补结构疲劳性能的数值和试验研究

为研究室温下复合材料胶接修补结构的疲劳性能,以三维渐进损伤理论为基础,创建了复合材料胶接修补模型,利用材料损伤判断子程序实现对修补结构的静拉伸失效载荷及剩余强度的预测分析,并进行了相关试验的对比分析。采用5种不同尺寸的圆形补片来评价修补效果,并利用超景深仪对修补试件的疲劳损伤扩展模式进行微观测量。结果表明:静载拉伸中,尺寸为3.5r的修补结构承载能力最好;疲劳循环中,尺寸为2.5r的修补结构剩余强度提升效果最好;疲劳载荷下,当循环次数较低时,修补结构的主要损伤为基体开裂,而随着循环次数的增大,主要损伤为纤维断裂。     

碳纳米管薄膜电加热固化复合材料胶接修补金属结构研究

近年来,复合材料胶接修补技术被广泛应用于金属损伤结构,但传统补片固化工艺有着成本高、能耗大及成型时间长等问题。针对该问题,本文提出将碳纳米管薄膜作为加热元件与复合材料预浸料补片进行集成,通过电加热固化达到修补损伤结构的目的。进行了试验研究,分别采用碳纳米管薄膜电加热和传统烘箱加热的方法固化复合材料补片修补含裂纹铝合金板,对比不同固化方法下所需能耗和成型时间,并进行力学性能测试,评估胶接修补的效果。结果表明:碳纳米管薄膜电加热固化技术是一种节能高效的方法,可以显著降低能耗和材料成型时间;同时碳纳米管薄膜电加热固化修补的试件承载力与烘箱固化修补的试件基本一致,可以达到预期的修补效果,为金属结构低能耗、低成本胶接修补技术提供了一种新的思路。     

复合材料胶接修补界面损伤演化声发射监测

利用声发射技术实时监测四点弯曲载荷作用下含纤维断裂玻璃纤维增强复合材料胶接修补后试件的损伤演化过程,结合声发射信号统计分析方法,研究贴补片尺寸对修复效果的影响。结果表明,弯曲载荷作用下,两类贴补修补试件破坏模式均以贴补界面开裂为主,随着胶接修补贴补面积的增加,试件失效载荷呈增大趋势。贴补修补片长度为90mm时,其破坏载荷约为未修补试件破坏载荷的2倍。修补试件损伤破坏过程与对应声发射特征表现出良好的相关性,声发射信号统计性描述方法能够有效用于评估胶接修补复合材料试件的微损伤演化行为。     

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。     

复合材料风扇叶片钛合金加强边胶接技术研究

本文以航空发动机复合材料风扇叶片钛合金加强边胶接为研究背景,开展钛合金/复合材料胶接技术研究,着重研究了基于AF191胶膜的钛合金/复合材料胶接工艺参数、不同结构复合材料与钛合金以及不同表面处理方式钛合金与复合材料胶接强度。结果显示:采用热压罐固化,并且在加压0.1 MPa后卸掉真空更有助于胶接;不同结构复合材料对胶接强度影响较大,刚度更高的复合材料表现为更好的胶接强度;采用酸洗和阳极化处理钛合金表面均能大幅提高胶接强度,并且配合表面预处理剂使用更佳。     

多异氰酸酯表面处理对木塑复合材胶接耐水性的影响

采用多异氰酸酯对聚乙烯木塑复合材料进行表面处理以改善其胶接性能。利用胶接强度和接触角测试以及SEM、FTIR、XPS等分析方法研究了表面处理对木塑复合材料胶接接头耐水性能的影响。试验结果表明,经打磨并采用多异氰酸酯表面处理后,复合材料的胶接强度和耐水性明显提高。水浸环境下,短期内异氰酸酯处理的木塑复合材料表面变化不大;长期水浸下复合材料的表面逐渐出现微裂纹,表面性质发生改变,胶接强度下降。聚乙烯木塑复合材料中木质纤维的吸水膨胀,是造成水环境下胶接强度下降的主要原因。     

Adhesively Bonded Patch Repair of Composite Laminates

Damaged composite laminates repaired using adhesively bonded patches have been studied. A special adhesive element is developed to examine the stress distribution in the bonded region. Utilizing the adhesive element, one is able to incorporate the regular elements in the laminate and patch. It has the advantage of reducing the adhesive bonding problem to a two-dimensional in-plane problem, and avoiding the need for refined meshes in the adhesive. The special adhesive element is derived based on the assumption of constant shear stress through the thickness of the adhesive. The damaged area of the composite laminate is simulated as a hole. The repair efficiency is evaluated by comparing the stress concentration factor in the damaged hole before and after repair. The effects of the thickness, size and material properties of both patch and adhesive on the stress distribution are presented through a parametric study. Numerical results indicate that a stiffer and thicker patch is able to carry higher loads, and, consequently, reduce the load across the damaged area yielding less stress concentration in the damaged hole. For a high shear modulus and thin thickness of the adhesive layer, less loads are transferred to the patch resulting in a high stress concentration in the damaged hole.     

改性环氧树脂光固化速粘胶的粘接应用研究

采用玻璃纤维布/光固化胶粘剂复合材料补片,实现对铝合金片的快速粘接与固化。考察了国产UV胶粘剂预聚物和进口UV胶的粘接性能、耐温性能以及粘接强度随胶粘剂相对分子质量及其分布的变化规律。结果表明:进口光固化胶/玻璃纤维布复合材料补片与铝合金片的剪切强度在14.5～23.1MPa之间,国产光固化胶体系剪切强度在11.3～16.6MPa之间,两者均高于铆接强度(10.3MPa);作为胶粘剂基体树脂,相对分子质量分布越宽越有利于粘接强度的提高;此外,-40℃低温与100℃高温对体系粘接强度的影响很小(不超过10%)。     

The role of patch hybridization on tensile response of cracked panel repaired with hybrid composite patch: experimental and numerical investigation

ABSTRACT

This article presents a distinct perspective of structural repair by bonding the hybrid composite patch. A novel hybrid composite patch is prepared from the carbon and glass fibers to repair the cracked panel. Different volume fractions of constituents are maintained to prepare the composite patch with varying stiffness. The elastic constant of the composite patch is derived by applying the rule of hybrid mixture and modified Halpin Tsai equation. The stress intensity factor in the panel and interfacial stresses in the adhesive layer are evaluated to assess repair efficiency and repair durability. Effects of the elastic modulus of the adhesive on the performance of composite patch repair are demonstrated. The load carrying capacity and failure strength are examined for variation in patch stiffness. The disbonded surface morphology is investigated through scanning electron microscopy after failure. The results reveal that the hybrid composite patch provided sufficient reinforcement to reduce the stress intensity and interfacial stresses. Patch hybridization has offered a pragmatic solution and proposed as an alternative patch material to repair the cracked structure.     

战伤抢修用复合材料补片胶粘剂的改性

以战时武器装备铝合金构件的快速抢修为背景,探讨了复合材料补片胶接修补用胶粘剂基本性能,并提出改性措施。结果表明,在SY-23B胶粘剂体系中加入4％的偶联剂KH-550时,粘接剂的剪切强度提高10％左右,达到36．6MPa,草酸能缩短固化时间,并提高粘接性能。     

Advances in the proof test for certification of bonded repairs – Increasing the Technology Readiness Level

The availability of an efficient, cost-effective repair technology is an important maintenance requirement to restore structural integrity to metallic and composite airframe structures damaged in service. Generally repair involves attachment of a reinforcing structural element or patch to replace the damaged load path. Traditionally, the reinforcements are attached to the structure with rivets or bolts; however, attachment by adhesive bonding offers many structural and cosmetic advantages.However, bonded repairs of primary structure are very difficult to certify this is because available non-destructive procedures, such as ultrasonics or thermography are unable to detect weak adhesive bonds. In view of the limitation of non-destructive inspection an alternative approach is to directly apply stress to the actual repair bond region or to a very close simulation of the region.In this paper, further work is documented on a proof test of bonded repair coupons (BRCs) that are bonded to the parent structure at the same time as bonding of the repair patch. Therefore, the BRCs are close representation of the actual repair bond strength. To assess the bond strength, immediately after patch application and also possibly through the life of the repair, the BRCs are subject to a previously determined proof load in torsion.The aim of the study is to improve the Technical Readiness Level of the test when applied to various parent-structure/patch-repair systems, including carbon-epoxy/carbon-epoxy; aluminium/boron-epoxy and aluminium/aluminium. Improved BRC application methods were developed to increase the reliability and consistency of the results, and sensitivity to cure condition, surface treatment, contamination, and fatigue damage were evaluated.A detailed finite element (FE) study was undertaken to: a) simulate stresses in the BRC, adhesive and parent structure during the proof test, b) compare the stresses in the patch and BRC when the parent material is under stress and c) investigate the influence of BRC proximity to the patch tip when the parent material is under stress.A conclusion from the FE analysis and fatigue study was that a BRC with the appropriate ply configuration could represent the bondline stresses experienced at the patch tip, and hence could also be used to monitor fatigue damage.     

Effect of temperature on the probability and cost analysis of mixed-mode fatigue crack propagation in patched aluminium plate

By the present paper, a numerical model for cost and probability analysis of mixed mode fatigue crack propagation in a patched 2024-T3Aluminium plate is developed. The finite element method is used to analyse the temperature effect on the bonded composite repair performance of the Aluminium plate. Using a fine mesh, mid-plane finite element results are in good experimental results given by literature. Different patch shapes are proposed like; circle, rectangle, square, ellipse, regular octagon, and prolonged octagon. The stress intensity factors at the crack tip are chosen as fracture criteria in order to estimate the repair performance. According to the temperature variation, the lifespan of the repaired fatigue crack growth is estimated using Paris law. The repair done on a central inclined crack with a single-side composite patch show that, best results are given by prolonged octagon and patch is damaged under at elevated temperature. The life-cycle of the patched Aluminium plate is obtained by Monte Carlo simulation, and the probability of failure is quantified according to various geometrical and mechanical parameters. At elevated temperature, the most dominant input parameters are thicknesses of adhesive and patch. In sensitivity analysis effect of thickness of the adhesive layer reaches 35%.Finally, a code source has been developed and implanted in ANSYS software, to consider the manufacturing process and optimal maintenance costs to prove the performance of patch operation from both safety and economical point of view.     

Stress distribution in a 2024-T3 aluminum plate with a circular notch,repaired by a graphite/epoxy composite patch

The aim of this study is to analyze by finite element method the single- and double-sided composite patch repairs designed to reduce the concentration of the stresses at circular notches and cracks. The results show that there is a considerable reduction in the asymptotic value of the stress-intensity factors and the normal stresses at the crack tip. The use of a double-sided patch suppresses the bending effect due to the eccentricity of the patch on one side only and reduces the shear stresses in adhesive.     

复合材料补片尺寸和形状对铝板修补结构lamb波传播影响

借助于ANSYS软件建立包含铝板、复合材料层合板补片、胶层和压电陶瓷片(PZT)的压电和逆压电效应的模型,实现在结构中激励和接收lamb波信号,并以试验验证模型的正确性。利用损伤对结构中lamb波传播特性的影响,对复合材料补片修补后的金属损伤结构的损伤检测进行数值模拟研究,研究不同补片尺寸及形状修补8 mm孔对lamb波损伤检测的影响。结果表明,圆形、方形、菱形补片的仿真模拟结果显示不同的形状对A0和S0波包的影响差异较大,不同尺寸的菱形补片也对A0和S0波包有较大差异。     

Study of tensile failure mechanisms in scarf repaired CFRP laminates

Bonded scarf repairs are used in composite structures when high strength recovery is desired or when there is a requirement for a smooth surface to satisfy aerodynamic requirements. Experimental and finite element study is carried out to understand the damage propagation and ultimate strength of scarf patch repaired CFRP laminates under uni-axial tensile load here. The ultimate strength and damage propagation in scarf repaired laminates has been investigated with respect to change in scarf angle and patch diameter. It is revealed from the results that damage is initiated in adhesive film at the bonded interface of 0° plies of parent laminate and patch in and then propagates in circumferential direction around scarf patch. It is found that some damage occurs in the parent laminate before the damage initiation in the adhesive film. After the adhesive film failure, the damage in parent laminate quickly propagates transversely to the free edge sides of the laminate and failure occurs. The results of this investigation provide further insight into the damage mechanisms in scarf repairs of composite structures under tensile load. This study may be helpful in improving the design and analysis techniques for scarf patch repair of composite structures.