Processing of Composites: Simulations of the Draping of Fabrics with Updated Material Behaviour Law

In the processing of composites, fiber reinforcement is draped over complex 3-D geometries, yielding local variations in the fiber volume fraction and fiber orientation with subsequent effects on the permeability of the reinforcement during resin infiltration and on the properties of the composite product. This study presents computer simulations of the draping of fabrics by following a mechanical, finite element approach. The fabric is considered as a solid continuum with mechanical properties and friction properties at interfaces. Applying an explicit dynamic FEM analysis solves the problem. In order to incorporate the large shear deformation of fabric during draping, an updated material behavior law was formulated on the basis of changing fiber directions. The model was implemented in a user computer subroutine and tested first in case studies of simple in-plane shear where the predictions were also compared with experimental data from a picture frame type of shear test. Thereafter, numerical simulations focused on the draping of a fabric in a hat-shaped mold comprising a hemispherical cup with a wide flat rim. (Author)