Analysis of Compressibility and Permeability of Selected 3D Woven Reinforcements

For three 3D woven carbon fiber reinforcements with different architectures, the compressibility, geometrical structure, and permeability were studied. At low levels of compression, the thickness of an angle-interlock weave is reduced mainly by local reduction of the height of inter-bundle voids and permanent reordering of the fiber bundles. At higher compression levels, bundle compaction is dominant. For an orthogonal weave fabric, the main compression mechanism is compaction of the fiber bundles. The in-plane permeability is modeled by superimposing a disturbance, caused by the binder yarns, to the permeability of a regular layered fiber structure. It is characterized mainly by the dimensions of the inter-bundle voids in each layer, and the pattern and dimensions of the binder yarns. Because of the dependence on the inter-bundle void dimensions, the fabric compression behavior is reflected. The through-thickness permeability is determined by flow-enhancing channels in the structure of the reinforcement, formed around the binder yarns. It is modeled as a function of the number of binder yarns per unit surface area, and the dimensions and orientation of the binder yarns.