Investigation of the friction behavior of uni- and bidirectional non-crimp fabrics

The friction behavior of engineering textiles directly affects the forming quality during composite molding processes. In forming tests of dry engineering textiles large relative slip between plies and the tools is observed. The resulting tangential contact stresses influence the material’s membrane stresses, which in turn impact the fabric’s deformation and potentially lead to forming defects such as gapping or ruptures of the textile. The characterization of friction is commonly conducted via relative motion between a fabric ply and either another fabric ply (ply-ply) or a tool (tool-ply) under controlled transverse pressure. The resulting behavior of a textile reinforcement depends on the mesoscopic structure of its unit cell and the material of its constituents. In this work, the tangential friction behavior at interfaces between ply and tooling and between plies of a unidirectional and a bidirectional non-crimp fabric are investigated in sled pull-over-tests. The behavior is analyzed with respect to the applied normal forces, the relative velocity and the relative fiber orientation. A generally rate-independent behavior is observed. ... mehrTool-ply friction is only slightly affected by the applied pressure, while ply-ply friction is strongly influenced by the stitching pattern at the contact interface.