Mesoscopic damage analysis of braided composites using mesh-superposition techniques for static failure and impact loading

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Braiding is an economical and fast manufacturing method to produce continuous textile preforms. Via variations in the braiding angle and braiding pattern it is possible to obtain architectures that can be optimally suited for applied loadings. In addition, braided composites have excellent damage tolerance in which damage propagation is influenced by the yarn architecture. For an accurate analysis of these damage processes it is essential to account for geometric complexity of the architecture and the various fibre or yarn, matrix and yarn-matrix interface failure mechanisms that can occur. To date this has not been possible, and most damage models use a homogenised approach that approximates damage. In particular, impact modelling of dynamic problems is challenging since detailed modelling of the architecture and the necessary computing capacities has so far made this type of simulation impractical.To overcome these limitations, this proposal will investigate mesh superposition techniques to discretely model the yarn and matrix phases, with kinematic coupling to combine the two constituents. This approach greatly reduces the model sizes and the degrees of freedom necessary for a practical solution. One drawback of the method is superposition of yarn and matrix volumes causing duplication of stiffness. This must be accounted for to obtain an equivalent stress distribution compared to a conventional model. For damage modelling and damage propagation this is necessary throughout the runtime of the numerical simulation. Furthermore, previous modelling techniques cannot be used without adaption for the mesh superposition technique to model damage or delamination for static failure or impact loading.This research proposal investigates new methods to predict damage modelling at the mesoscopic scale of braided composites for both static failure and impact loading. Furthermore, existing finite element-based modelling methods and well validated composites damage models will be applied, with new research focussed on combining these models with the new mesh superposition technique. As a result, the occurring damage mechanisms are no longer homogenised, but can be captured separately and holistically, which leads to a higher forecast quality and better material understanding than with previous modelling approaches. In the proposed study, a load case optimized braided architecture will be derived, which is validated for different load cases from static non-symmetrical shear and open-hole tension to impact and compression-after-impact tests. This method is not only limited to braided structures and will be applicable to other woven textile composites and advance current capabilities to model geometrically complex components under static failure and impact loading.