飞机胶接修理中的补板厚度优化

为了提高飞机机体损伤应急快速胶接修理的质量和效率，利用弹塑性有限元分析及试验方法探讨了胶接修补飞机蒙皮时补板厚度对胶接补强水平的影响。发现合理选取补板厚度可明显提高胶接修补的补强水平，进而提高修复结构的强度，一般情况下，取补板厚度小于蒙皮板厚度。这一新的胶接修补技术在不改变原有的修补工艺、材料、设备的前提下，可提高胶接修理的水平、机体结构的强度．减轻飞机结构质量，简化操作，降低成本。     

非穿透性结构损伤修理研究

研究了非穿透性结构损伤的修理,讨论了树脂填充、增强树脂填充和复合材料粘接3种修理方法对结构承载能力恢复的影响。研究结果表明,前2种方法对结构承载能力的恢复影响较小,复合材料粘接修理可以很好地恢复结构的承载能力,其中采用碳纤维复合材料比玻璃纤维复合材料补片可以获得更好的修理效果。随着补片厚度和刚度的增加,粘接修理结构的破坏形式以剥离破坏为主。     

补片形状对复合材料结构胶接修理效果的影响

以圆孔型损伤为例,采用三维有限元模型分析了复合材料胶接修理时补片形状对其承载能力的影响。结果表明,在胶层面积、补片材料和修理工艺等参数不变的前提下,圆形补片比矩形补片能显著提高复合材料结构胶接修理的承载能力;对于相同的矩形补片,当其长边平行于外力方向时更有利提高复合材料结构胶接修理的承载能力。     

胶补飞机蒙皮补片形状优化研究

以圆形孔洞损伤为例,采用三维弹塑性有限元法探讨了应急粘接修补飞机蒙皮时补片形状对补强水平的影响。发现采用圆角矩形补片,在不改变原有补片材料、修补工艺和设备的前提下,可提高被修复蒙皮的强度,进而提高被修复损伤飞机的安全性,对飞机战伤抢修具有一定的指导意义。     

薄层合板单面贴补修理拉伸性能研究

贴补修理是工艺简单、应用较广的复合材料结构修补技术。对含有孔穿透损伤的复合材料层合板单面贴补修理试验件进行拉伸试验,保持补片的铺层顺序、厚度不变,改变补片的直径,考察补片直径对单面贴补修理效果的影响,并根据试验过程中采集的试验件相应位置的应变数据以及载荷位移曲线分析其失效机理。结果表明,单面贴补修理试验件的强度恢复率约为34%～50%,且贴补修理对于含穿透孔损伤层合板的刚度具有一定的恢复作用,而且随着补片直径的增大,强度恢复率增高。当补片直径较小时,胶层先于母板发生破坏,此时的修理效果不明显;当补片直径增大到一定程度后,胶层承载能力较高,此时贴补修理对损伤件的拉伸强度有一定的提高作用。在试验基础上建立了有限元模型,能有效预测贴补修理件的破坏模式、拉伸强度,并可分析得到试验件的应力分布;改变有限元模型参数,研究最佳效果的补片尺寸与损伤孔径之间的关系。结果表明,当补片直径比损伤孔径大30 mm～40 mm时可获得较高的修理效率。为复合材料层合板设计贴补修理方案提供了参考。     

复合材料层合板贴补修理稳定性研究

论文针对胶接修理的贴补修理方式,基于MSC.PATRAN(有限元分析)软件建立层合板和双筋及格栅加筋板的有限元模型,对于常见的一边固定一边受平面压力的情况,进行屈曲分析,研究补片的尺寸和厚度对于修理稳定性的影响,然后找出屈曲特征值随补片参数变化的规律。研究结果表明,补片直径和修补后模型的屈曲特征值之间的变化关系并不是简单的线性关系;补片的直径和厚度取某特定区间的时候整个模型最稳定;对于加筋层合板来说,筋条可以分担部分载荷,所以加筋板筋条间的母板损伤修补效率比层合板有所提高。     

补片尺寸对胶层应力分布的影响

粘接修理结构中,胶层起着传递载荷的作用。其应力状态对于粘接修理结构有着重要的影响。为此,本文用有限元法分析了复合材料粘接修理结构中胶层应力分布随补片尺寸的变化。研究表明,增加补片长度和厚度可以提供补片分担载荷的作用,但是,对胶层的性能要求提高。胶层中大部分区域的应力较低,大部分载荷靠较小面积的胶层传递。修理试样的破坏形式的变化反映了胶层应力分布的变化。     

金属钉孔边裂纹复合材料修理方式研究

对飞机铝合金薄蒙皮结构常发性裂纹的修理方式进行研究，仿真分析了去除原结构钉、保留原结构钉、混合加强三种胶接修理后结构的承载能力变化，并与力学性能测试结果进行验证，结合破坏模式提出了修理建议。结果表明，经三种方式修理后结构的承载能力均得到有效恢复，保留原结构钉的修理方式破坏载荷恢复可达90%，疲劳寿命可达89 277次循环，但会有产生多余物的风险，适用于紧急抢修。混合加强修理后破坏载荷可达38 491 N，疲劳寿命可达67 884次，在兼顾安全性的同时拥有较高的强度，适用于基地级维修。去除原钉的修理强度最低,为37 150 N，疲劳寿命仅为35 250次。     

光固化碳纤维布/CEP-ES复合材料粘接修理金属损伤结构

设计了具有紫外光辐照引发自蔓延固化特性的脂环族环氧树脂(CEP)与有机硅树脂(ES)的混合树脂体系(CEPES),并以它们为基体实现了碳纤维增强复合材料的快速光固化。研究了以光固化碳纤维复合材料为补片粘接修理金属损伤结构的影响因素。结果表明,有机硅树脂的引入不仅可以有效提高粘接修理的效果,而且可以改善粘接修理结构的耐湿热性能,当ES的质量比为20%~30%时,粘接修理结构具有最好的承载能力;适当增加复合材料补片的长度和层数可以有效提高粘接修理的效果;双面贴补修理比单面贴补修理具有更好的粘接修理效率。     

蒙皮穿透裂纹损伤胶接修理的强度评估

基于有限元计算方法,对某飞机机翼蒙皮裂纹损伤胶接修理方法进行了强度评估。研究了60mm长度穿透型裂纹损伤对胶接修理搭接宽度的影响,得到了较有利的搭接宽度,对蒙皮裂纹损伤修理具有参考价值。     

Experimental investigation of repair of impact-damaged aircraft winglet under static bending moments

Bending behaviours of the repaired aircraft winglet were investigated in this paper. Impact damage was firstly inflicted at the center of three pristine winglets by using a drop-weight impact device. The damaged core was restored by filling in the same foam and the damaged skin was repaired by bonding to a three-dimensional scarf patch accompanied with an additional external layer (Doubler). Then, the ultimate load-bearing capacity and failure mechanism of the repaired winglets under static bending moments were studied and compared with the pristine ones. Furthermore, the influence of the stress state of the patch (tension or compression) was discussed by attaching the patch on the top and bottom respectively during testing. The experimental results show that the repaired winglets retain approximately 82% of the load capacity of pristine winglets. Damage occurs along the bolt holes on the composite skin of pristine winglets, while the repaired winglets fail due to the shear crack of the foam and debonding between the foam core and the composite skins. Finally, finite element method were used to explore the failure mechanism for repaired and pristine winglets by comparing the stress distributions. In addition, parametric studies were conducted.     

Strength and interface failure mechanism of adhesive joints

Adhesive joints have a wide range of applications in the civil engineering, automotive and aircraft industries. In the present research, we use the finite element method to systematically study the overall strength and interface failure mechanism of single lap joints, which are subjected to tensile loading, focusing on the effects of various system parameters including fracture energy of the adhesive layer, overlap length and adhesive layer thickness on the load-bearing capability of the joints. The results show that the overlap length and the adhesive fracture energy have combined influences on the load-bearing capability. On the other hand, a preliminary damage analysis of the adhesive layer is carried out, considering the situations when the loads arrive to the peak values. Furthermore, the interface behavior is investigated, including the interface stress analysis and interface slip. The rotation of the joint during loading and its influence factors are studied as well. Obtained results suggest that the interface stress distributions are related to the slip and the rotation angle.     

The role of yield stress on cracked thin panels of aluminum alloys repaired with a fRP patch

The aim of this study was to explore the effect of the yield stress of the cracked thin panels of aluminum alloys panel, repaired with one sided fiber reinforced polymer (FRP) patch, on the performance of the repair. Various different grades of aluminum alloys with thickness in the range of 1–1.3 mm were used as the skin material. The numerical simulation of the experimental results was done through ANSYS 15.0, using a cohesive zone material model (CZM model) at the interface of the skin and the patch. The effect of the far field applied stress was analyzed to simulate the initiation and the separation of the patch. In all the six cases, undertaken in this study, the patch separation occurred when the applied stress exceeded the yield stress of the skin by a small percentage. Even in the thinnest patch with its stiffness ratio of 0.28, the patch separated when the applied stress exceeded the yield strength of the skin material. In all the cases, the shear stress at the interface caused the slippage between the patch and the skin at the leading edge of the patch.     

航空用球形金属内衬复合材料气瓶研制

本文简要介绍了航空用球形复合材料气瓶的结构形式、受力状态和设计方法,对所研制产品的设计、制造与鉴定检验进行了总结。研究表明,该球形气瓶能够满足航空系统的技术要求。     

Implementing optical fibres for the structural health monitoring of composite patch repaired structures

Abstract

Structural health monitoring is increasingly being implemented to improve the level of safety of structures and to reduce inspection and repair costs by allowing for correct planning of these actions, if needed. Composite patch repairing presents an appealing alternative to traditional repair methods as it enables the reduction of closedown time and the mitigation of complications associated with traditional repair methods. As reinforcement with the use of composite patches is predominantly performed at defected structures, the urge to monitor the performance of the repair becomes even greater. This work deals with the use of Fabry Perot optical fibres and strain gages at suitable positions in such a repair. To this end a patch repaired notched steel plate has been tested in tension, opting to gain insight on the mechanisms which govern the failure. In order to investigate how these mechanisms are reflected to the recorded strain measurements, finite element models have been generated. Results indicate that composite patch repairing drastically increased the load bearing capacity of the plates and that optical fibres constitute an appealing health monitoring system for such applications, being able to capture the initiation and evolution of damage.     

残余热应力对复合材料修理金属裂纹板影响分析

本文建立了复合材料胶接修理金属裂纹板的三板有限元模型;采用分析金属裂纹板裂纹尖端应力强度因子的方法,分析了残余热应力对复合材料修理金属裂纹板修理效果的影响。结果表明,残余热应力对单面修理结构的影响小于双面修理结构。残余热应力对单面修理结构的影响由于裂纹板宽度比值不同而不同。补片与母板的热膨胀系数相差越大,残余热应力对修补效果影响越大。     

高强度钢刷镀镉工艺研究

本文研究了刷镀镉技术在飞机高强度钢结构件表面损伤修复中的应用。试验结果表明，该工艺操作简便，质量稳定，适用于飞机零件现场维修。     

Damage mechanism and residual strength at different impact locations for composite bonding scarf repairs

Composite scarf repair has been widely applied as a high efficiency choice for force transferring in aircraft structure repair. The damage tolerance and resistance to low velocity impact are significant for structure design especially for primary load-bearing structures. Some literature studied impact damage and resistance for scarf topology repairs or joints. However, it is not clear that which location in bonded area is the most sensitive to the impact load. The impact location effect on impact damage mechanisms and capacity of tension after impact (TAI) are studied in this paper. Central point in bonded zone has the strongest influence on impact damage. The scarf adhesive film fractured from the feather tip of the back side and oriented to the weakest material. The load capacities of tension after impact at different locations coincide with the adhesive damage area ratio. The finite element model based on CZM (Cohesive Zone Model) is built. And the simulation results validate that central location has the most sensitive characteristic to impact damage and TAI capacity.