Digital image correlation strain measurement of thick adherend shear test specimen joined with an epoxy film adhesive

Structural bonding and bonded repairs of composite materials become more and more important. Understanding the strain within the bondline leads to suitable bonding design. For new design approaches the strain distribution within the bondline has to be analyzed. Thus, often finite element analysis (FE) are used. However, a huge challenge is the availability of reliable material properties for the adhesives and their validation. Previous work has shown that it is possible to measure the small displacements resulting within thin epoxy film adhesives using high resolution digital image correlation (DIC). In this work a 2D DIC setup with a high resolution consumer camera is used to visualize the strain distribution within the bondline over the length of the joint as well as over the adhesive thickness. Therefore, single lap joints with thick aluminum adherends according to ASTM D 5656 are manufactured and tested. Local 2D DIC strain measurements are performed and analyzed. Two different camera setups are used and compared. The evaluation provides reliable material data and enables a look insight the bondline. The results of the full field strain data measured with DIC are compared with numerical simulations. Thus, material models as well as chosen parameters for the adhesive are validated. Compared to extensometers, giving only point-wise information for fixed measuring points, the DIC allows a virtual point-wise inspection along the complete bondline. Furthermore, it allows measuring close to the bondline to reduce the influence of adherend deformation.     

Assessment of local strain field in adhesive layer of an unsymmetrically repaired CFRP panel using digital image correlation

The present study focuses on experimental investigation of through the thickness displacement and strain field in thin adhesive layer in single sided (unsymmetrical) patch repaired CFRP (carbon fiber reinforced polymer) panel under tensile load. Digital image correlation (DIC) technique is employed to acquire the displacement and strain (longitudinal, peel and shear) field. Experimental determination of shear transfer length based on shear strain field obtained from DIC is introduced to estimate the optimum overlap length which is an essential parameter in patch design for the repair of CFRP structures. Further, DIC experiment with magnified optics is performed to get an insight into complex and localized strain field over thin adhesive layer especially at critical zones leading to damage initiation. The failure mechanism, load displacement behavior, damage initiation and propagation are closely monitored using DIC. The influence of patch edge tapering on strain distribution in adhesive layer is also investigated. The DIC successfully captures the global and localized strain field at critical zones over thin adhesive layer and further helps in monitoring the damage based on strain anomalies. Strains are found to have maximum magnitude at the patch overlap edge and the shear strain level in adhesive layer is higher than the peel strain. Normal tapering increases the peel strain and has negligible influence on shear strain level in adhesive layer. The recommended overlap length is found to be consistent with the recommendation in the literature. Whole field strain pattern and the overlap length obtained from experiment are further compared with the finite element analysis results and they appear to be in good coherence.     

高性能大尺寸永磁体粘合强度的测定

介绍了一种用三点弯曲试验法测定高性能大尺寸粘接永磁体粘合强度的方法，及利用布氏硬度计的加载系统，实现100％检验粘接质量的方法。     

快干性瓦楞纸箱粘合剂的研制

本文叙述了快干性瓦楞纸箱粘合剂的配制及工艺过程。实验结果表明，该粘合剂具有快的干燥速度和良好的性能     

LED生产过程中的质量控制

对LED封装过程可能出现的问题逐一指出，并提出解决的办法，着重介绍封装位置对LED发光亮度的影响。以期引起LED封装管理人员及工作人员的注意。     

固定电子分立元器件用胶粘剂E—4X的研制

介绍了一种不同于灌封材料，具有触变性，粘接性能优良，使用方便的固定电子分立元器件用胶粘剂Ｅ－４Ｘ。与国外同类产品Ｅｐ－４３３ｘ胶粘剂对比，其综合性能优于Ｅｐ－４３３胶粘剂。     

INTERFACE/INTERPHASE ENGINEERING OF POLYMERS FOR ADHESION ENHANCEMENT: PART II. THEORETICAL AND TECHNOLOGICAL ASPECTS OF SURFACE-ENGINEERED INTERPHASE-INTERFACE SYSTEMS FOR ADHESION ENHANCEMENT

Part I of this paper reviewed the theoretical principles of the macromolecular design of polymer interface/interphase systems for obtaining maximum adhesion and fracture performance of adhesively bonded assemblies. In Part II a novel, relatively simple and industry-feasible technology for surface-grafting connector molecules is demonstrated and discussed in detail and supported by a range of experimental examples. It is shown, in agreement with contemporary theory, that the use of chemically attached graft chemicals of controlled spatial geometry and chemical functionality enables a significant increase in the strength and fracture energy of the interphase, to the point of cohesive fracture of the substrate, or that of an adjacent medium such as adhesive, elastomer, or other material. This occurs even after prolonged exposure of investigated systems to adverse environments such as hot water.     

基于画圆算法的简单弧形贴图算法

本文提出了一种基于画圆算法的简单弧形贴图算法，并分析了该算法的可行性。     

RETARDATION AND REPAIR OF FATIGUE CRACKS BY ADHESIVE INFILTRATION

Abstract— This paper presents results which demonstrate that polymeric filler materials, such as low-viscosity epoxies, can be vacuum-infiltrated into fatigue cracks in 7050 aluminium alloy to produce significant levels of fatigue crack retardation. It was found that the main test variable affecting the degree of retardation was the stress level at which the adhesive was introduced and cured. Two infiltrated adhesives were tested.
Infiltration at 0% (of the original) peak fatigue stress level produced negligible retardation, while infiltration at the 80% stress level produced about 300% increase in fatigue life for one adhesive and 3000% for the other adhesive. For the highest infiltration stress level both crack-face wedging and adhesion contributed initially to the retardation, but the adhesive component ceased after a crack grew through the adhesive to the original crack tip position. The results are discussed in terms of the applicability of the technique to highly-stressed aircraft components.     

自粘聚合物改性沥青防水卷材胶粘剂

在SBS改性沥青防水卷材表面涂敷一层自粘性胶粘剂并以隔离纸覆盖，使用时撕掉隔离纸直接粘贴于屋面即可粘接密封牢，不但施工方便而且消除了熔融法施工造成的污染。该胶粘剂由沥青40％～65％，SBS 5％～30％，增粘剂2％～25％和助剂5％～25％构成。胶层具有可塑性、延展性，可自行填补屋面出现的裂缝，保证防水卷材的防水密封效果。