Multi-scale modeling of the anisotropic, nonlinear damage behavior of carbon fiber reinforced plastics

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In recent years, the demand for structural components made from carbon fiber reinforced plastics (CFRP) has severely risen in several branches of industry. There are two important categories of reinforcements: the unidirectional ones, where all fibers are aligned parallel, and the textile ones, in which the reinforcing fibers are woven. The latter are advantageous because the mechanical properties can be optimized in several directions. On the other hand, compared to their unidirectional counterparts, textile composites introduce additional geometric complexities, which cause significant local stress and strain concentrations, being primary drivers of nonlinearity, damage, and failure within textile composites.In order to account for these effects in the design of laminated structures, whose layers are composed of CFRP with textile reinforcement, a hierarchical multi-scale approach is applied in the current project. At first, a micromechanical model will be developed for the tows, in which the fibers and the matrix are modeled separately. Next, a mesomechanical model on the textile scale is formulated which inludes the effects of the micro-scale in a homogenized manner and which accounts for geometrical effects due to the curvature of the tows. Finally, a macromechanical model is set up, which is suitable for application to real structures and structural components.The main goal of this project is the development of a material model, which allows predicting the damage evolution within single layers. For this, a continuum description of progressive damage is used. This model shall consider the anisotropy of the entire composite, the plasticity of the matrix material, and the interaction between damage components in different directions. Moreover, delamination, which is the interfacial unbonding of layers, is to be considered since it constitutes one of the major failure mechanisms in laminated structures. Both, the intralaminar as well as the interlaminar (delamination) damage progression will be reflected by using the unified model to be developed.