Method and process development for the infiltration of truss structures made of fiber-reinforced plastics with multilayer variable-axial fiber architecture (MerVa-2)

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The MerVa-2 research project deals experimentally and numerically with the infiltration behavior of structural fiber-reinforced plastic (FRP) structures with multilayer variable-axial fiber architecture produced by the Tailored Fiber Placement (TFP) process. In the first project phase MerVa-1, the infiltration behavior of single-layer TFP structures was investigated experimentally and numerically using resin transfer molding. Comprehensive knowledge was gained about the infiltration behavior on micro, meso and macro scales as well as about the influence of the variable-axial fiber architecture on mold filling. In order to be able to develop reliable gating strategies for TFP structures, an understanding of the infiltration behavior of multilayer fiber architectures is furthermore of importance. The challenge in considering multilayer TFP preforms lies in the increased complexity of the textile structure. The stitching of multiple layers results in a multidimensional flow front that cannot be represented by a simple superposition of single layers. The reason for this is the development of flow channels through all layers as well as an additional compacting of the rovings, which results in a strongly heterogeneous filling behavior. In the second project phase, these more complex infiltration processes of multilayer TFP structures are to be understood and numerically modeled. For this purpose, the meso-structure as well as the meso-structure dependent infiltration behavior of multilayer variable-axial TFP preforms with different stitch patterns and ply orientations will be investigated experimentally. Based on the experimental results and measurements of the infiltrated structures, meso and macro models of typical multilayer TFP preforms are generated and evaluated with respect to existing infiltration faults. In addition, the scalability of the occurring effects will be analyzed and an approach will be developed to pass meso-model information beyond the homogenized permeability tensor to the macro-simulation where necessary. The overall objective of the project is to reliably model the infiltration of complex, multi-layer variable-axial TFP structures as well as possible faults in order to be able to safely plan, execute and evaluate infiltration processes virtually in the future.