A First Step Towards the Numerical Simulation of the Forming of flat TFP Preforms

Abstract

The mechanical efficiency of fiber-reinforced composite materials mainly depends on the alignment of fibers along the load paths arising from the boundary conditions applied to the part. On this basis, the Tailored Fiber Placement (TFP) consists in building a fibrous reinforcement by continuously laying down a tow on a plane backing material which can be a polymer film or a fibrous reinforcement such as woven fabrics or NCF. The tows are maintained in place with the desired orientation with a stitch. To fully take advantage of the design freedom offered by TFP in composite stamping, the designer who can compute the optimized fiber orientations in the final 3D part, has still to determine the tow’s path on the plane backing material since tow’s motions will inevitably occur during the forming process. The present study which falls within the simulation of material forming attempts to model the behavior of TFP preforms using the finite elements method. The backing material is represented by a mesh of 2D elements with embedded linear beam element modeling explicitly the tow’s layout analogously to the modeling of reinforced concrete in civil engineering applications. Consequently the degrees of freedom of the beams are interpolated from the host element. However the displacement constraint at the beam nodes is relaxed in the tow’s path direction. To demonstrate the accuracy of this finite element formulation, standard tests for fiber-reinforced composites such as bias extension test as well as a simple 3D test case will be presented.