Analysis of the blank holder force effect on the preforming process using a simple discrete approach

Abstract

Simulation of the dry reinforcement preforming, first step of the Resin Transfer Moulding process, become necessary to determine the feasibility of the forming process, compute the fiber directions in the final composite component, and optimize process parameters during this step. Contrary to geometrical approaches, based on fishnet algorithms [1, 2], finite element methods can take into account the actual physical parameters, the real boundary conditions and the mechanical behaviour of the textile reinforcement [3, 4]. The fabric can be modelled either as continuum media with specific material behaviour [5, 6], or using discrete structural elements to describe the textile structure at the mesoscopic scale [7, 8]. A semi-discrete approach, which is a compromise between the above continuous and discrete approaches [9, 10], is also used for simulation. A discrete approach for the simulation of the preforming of dry woven reinforcement has been proposed and presented in a previous paper [11]. This model is based on a “unit cell” formulated with elastic isotropic shells coupled to axial connectors. The connectors, which replace bars or beams largely studied in other discrete approaches [12], reinforce the structure in the yarn directions and naturally capture the specific anisotropic behaviour of fabric. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomena with the punch and die. The linear characteristic of the connectors [11], has been extended to a non linear behaviour in the present paper to better account for fabric undulation. Using this numerical model, we propose, in this work to study the effect of process parameters on the woven fabric deformation during the performing step. The emphasis will be placed on the analysis of the influence of the blank holder pressure on the shear angle distribution.