The draping and consolidation of commingled fabrics

Abstract

Commingled fabric composed of yarns containing both the reinforcement and the matrix in fibre form is an innovative preform material used in the manufacture of fibre reinforced thermoplastic composites. A quality of commingled fabric is its drapability allowing it to conform to mould shapes before being consolidated into a rigid structure. This paper describes a simulation of the draping process and a mathematical model of the subsequent consolidation process which predict, for a given mould surface and processing parameters, the material characteristics necessary for determining the mechanical properties of the finished product. The draping simulation graphically depicts an arbitrary surface with a bidirectional fabric conforming to the surface. The results of the simulation determine fibre orientation at any point on the draped surface. Fibre orientations are affected by in-plane shear deformation in the fabric when it conforms to surfaces of compound curvature. Wrinkling and bridging are predicted given the deformation limits of the fabric. The simulation may be used as a design tool for selecting suitable draped configurations for specific surfaces. The consolidation model predicts, for a commingled or cowoven fabric, the laminate thickness, reinforcing fibre volume fraction and void content as functions of time during the process and the time required to reach full consolidation. The model may be used to examine the influence of various material and processing parameters on consolidation behaviour. Combining the results of the draping simulation and consolidation analysis with a laminate analysis allows the prediction, for a given set of draping constraints and processing parameters, of the mechanical properties at any point in a composite structure formed from commingled or co-woven fabric.