Iterative Un-Forming of Highly Aligned Discontinuous Preform/Material

Inherent limitations restrict the application of automated fibre placement (AFP) for manufacturing small components with complex geometries. As an alternative, flat, tailored preforms composed of fibre tows are first created and then formed into desired 3D geometries. However, the fibre orientation deviations between the as-manufactured and as-designed parts are inevitably introduced during forming. To address this issue, this study presents an iterative numerical forming/un-forming framework for the manufacture of highly aligned discontinuous preforms. At first, the as-designed preforms are “un-formed,” i.e., a reverse forming simulation, to achieve the corresponding flat preforms using the finite element modelling (FEM) method. To mitigate the deviations during forming, a pre-compensation strategy is then introduced by adjusting the initial fibre orientations derived from the un-forming analysis based on the calculated deviations through iterative re-forming simulations. A hypo-viscoelastic constitutive model implemented through a user-defined material subroutine captures the rate-dependent and orthotropic behaviour of the preforms during un-forming and re-forming. The FEM simulation results demonstrate significant reductions in fibre orientation deviation of formed 3D preforms through the iterative forming/un-forming framework, validating its applicability to a discontinuous fibre material on complex geometries.