Simulation of the mode of failure and application of micro capsules in adhesives for premature damage detection

通过施加粘合剂的接合具有优于其它接合技术的许多优点。因此，在汽车工程和机械工程等关键行业中，粘接已成为一个重要的组成部分。处理粘接结构时的一个重要问题是验证安全相关因素，如接头强度和老化行为。然而，由于许多测试程序属于破坏性检查方法，而且在制造过程中最常进行的非破坏性检查不能提供有关应力部件预期寿命的任何信息，因此这种检测受到很大的限制。使用含有填充有染料的微胶囊作为视觉标记的粘合剂可以很容易地检测粘合剂层的劣化：如果出现裂缝，微胶囊也会被破坏，并释放出可检测的染料.裂纹的扩展受胶层中的不均匀性（微胶囊）的强烈影响。因此，本研究计划的主要目标是对胶粘剂三维网络中的初始裂纹起源和裂纹扩展进行力学劣化模拟。此外，模拟参数的评估将是至关重要的。为了观察透明基板材料（如环烯烃共聚物和聚碳酸酯）和透明粘合剂聚合物（如环氧树脂、硅、丙烯酸酯和聚氨酯）的裂纹扩展系统，将分别应用。所需的微胶囊通过界面聚合制备，并在形态、壁厚和粒度分布方面进行表征。通过改变反应条件和原料，可以获得不同的胶囊参数。这些胶囊将构成随后审查模拟结果的基础。

The joining by the application of adhesives has many advantages over other joining techniques. Thereforeadhesive bonding has become a significant part in key industries like automotive engineering and mechanicalengineering. An important issue when dealing with bonded structures is the verification of safety relevantfactors like the strength of the joint and the ageing behavior. This detection is nonetheless strongly limitedsince many test procedures belong to destructive inspection methods, and also non-destructive inspectionswhich are most often conducted during the fabrication process do not deliver any information about the lifeexpectancy of stressed components.The application of adhesives which contain microcapsules filled with dyes as visual markers can readily enablethe detection of deterioration in the adhesive layer: If a crack occurs the micro capsule is also damaged andthe incorporated detectable dye is released. The crack propagation is strongly influenced by theinhomogeneities (micro capsules) in the bond line. Therefore, a main target of this research project is themechanical deterioration simulation of the origin of incipient cracks and the crack propagation in thethree-dimensional network of the adhesive. In addition, the evalution of simulation parameters will be crucial.For the observation of the crack growth systems of transparent substrate materials (e.g. cycloolefine copolymer and polycarbonate) and transparent adhesives polymers like epoxy resins, silicons, acrylates, andpolyurethanes, respectively, will be applied. The required micro capsules are prepared by means of interfacial polymerisation and are characterized in terms of morphology, wall thickness, and particle size distribution. Byvariation of reaction conditions and starting material different capsule parameters can bhe achieved. These capsules will form the basis for the subsequent review of simulation results.