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The appearance of fretting fatigue cracks in bolted sheets limits their lifetime. Furthermore, repairing these failures requires much effort due to needing to replace the components instead of replacing just the bolt. To prevent such failures, the purpose of this study is to understand the failure mechanism and to identify the major influencing parameters. Therefore, a representative joint of a bolt of size M22 and sheet material were investigated by experiments and a finite element analysis. The experiments were conducted over a wide range of preloads from zero to maximum preload. It turned out that the failure mode changes at 50 kN. For this preload, the influence of the surface and the use of a lubricant was observed. A grinded surface as well as the use of lubricant showed a change in the failure mode. The accompanying simulation showed that an analysis of the stresses delivers no proper explanation for the observed effects in the experiment. Therefore, the contact status was analyzed for various preloads and friction coefficients. The results correlate with the change in the failure mode. The conclusion is that both the stress state and the tribological behavior influence the failure mode and have to be considered in a numerical analysis.

The functionality of products increases when more sensors are used. This trend also affects future automobiles and becomes even more relevant in connected and autonomous applications. Concerning automotive lightweight design, carbon fibre-reinforced polymers (CFRP) are suitable materials. However, their drawbacks include the relatively high manufacturing costs of CFRP components in addition to the difficulty of recycling. To compensate for the increased expenditure, the integration of automotive sensors in CFRP vehicle structures provides added value. As a new approach, established sensors are integrated into fibre-reinforced polymer (FRP) structures. The sensors are usually mounted to the vehicle. The integration of sensors into the structure saves weight and space. Many other approaches specifically develop new sensors for integration into FRP structures. With the new approach, there is no need for elaborate development of new sensors since established sensors are used. The present research also showed that the range of applications of the sensors can be extended by the integration. The present paper outlines the functional behaviour of the integrated sensor utilized for crashing sensing. First of all, the integration quality of the sensor is relevant. Different requirements apply to the usual mounting of the sensor. The self-sensing structure must fulfil those requirements. Moreover, unfamiliar characteristics of the new surrounding structure might affect the sensing behaviour. Thus, the sensing behaviour of the self-sensing composite was analyzed in detail. The overarching objective is the general integration of sensors in products with reasonable effort.