Strukturmechanische Auswirkung fertigungsbedingter Imperfektionen aus Faserverbundablegeprozesses

Abstract

Currently, the manual quality control and reworking of fiber composite structures requires a significant amount of time. These quality-assuring process steps do not include any structural mechanical based verification regarding the effects of occurring process deviations on the part properties. As a result, the parts containing manufacturing-induced imperfections are subjected to conservative reduction factors. These factors are determined by extensive test programs. Therefore, the production process still requires too much effort to meet the required quality and tolerances. This thesis evaluates if the structural-mechanical effects of gaps and overlaps, which occur locally during the manufacturing process by means of automated fiber deposition, can be evaluated with state-of-the-art algorithms. This dissertation demonstrates the use of detailed finite element models to assess laminate sections with imperfections. The selected methodology is broadly based on multiscale analysis. With micro-mechanical models, this analysis provides the adequate homogenized properties of a heterogeneous material. The finite element models used here are subjected to special boundary conditions. Out of this analysis, the influence of manufacturing imperfections on the actual material properties of each individual layer within the laminate can be derived. The methodology developed in this thesis will enable an assessment of the quality and performance of a fiber composite structure with imperfections during the manufacturing process without the need for time-consuming analyses of highly detailed finite element models.