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Combined experimental-numerical fracture analysis of fiber reinforced composites

Thursday (27.09.2018)
15:30 - 15:45 S1/01 - A2
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Continuous fiber reinforced thermoplastic tapes offer promising mechanical characteristics, such as high stiffness and tensile strength relative to the weight density, and can be used to build customized structural parts. For this reason, such tapes have recently been used for lightweight structural parts as well as lightweight patching material to locally reinforce a specific part area. The manufacturing process of such parts, however, requires the pre-consolidation of the raw tape material, which consists of three steps: tape laying, heating, and compression of the tape layers. It is important to understand how this manufacturing method affects interface microstructures and their mechanical properties, in particular, delamination fracture toughness between the tape layers. As fracture toughness experiments rely on the measurement accuracy of a propagating crack, conducting these experiments can be challenging due to stepwise and abrupt crack propagation, crack branching, or fiber bridging. Hence, the experiment evaluation regarding the material's critical energy release rates can become imprecise and can result in highly scattering data. By means of a reverse simulation approach considering the macromechanical material behavior as well as its micromechanical crack initiation and propagation schemes, the experiment evaluation can be refined in order to obtain a better understanding of the material's failure behavior. Therefore, a virtual microstructure statistically representing the real microstructure is generated using a Voronoi tessellation scheme and implemented as a sub-model within a FEM model of a macroscopic fracture toughness specimen. The virtual microstructure consists of several cells, each representing fiber rich or fiber poor areas of the actual material, with homogenized material properties as a function of the corresponding fiber volume fraction. With this model, the inverse simulation approach shall help evaluating the fracture toughness experiments in order to obtain reliable material model parameters necessary for the further part development process.

Michael Schober
Fraunhofer Institute for Mechanics of Materials IWM
Additional Authors:
  • Dr. Jörg Hohe
    Fraunhofer Institute for Mechanics of Materials IWM
  • Dr. Takashi Kuboki
    University of Western Ontario