Variable Forming Tool and Process for Thermoset Prepregs with Simulation Verified Part Quality

Abstract

In this paper a new variable forming tool concept and associated numerical methods for calculating optimal actuator layout and estimating CFRP part quality are presented. The concept of the tool features a modular design and active control of the forming process to achieve the desired geometry. Initially the laminate is placed on the flat top layer of the forming tool. There it is fixed and compacted using vacuum bagging. After compacting, it is heated up to increase the performance of the forming process using water based tempering of the forming tools top layer. The heated laminate is then formed, pulling the tools top layer into the desired geometry using the actuators. Finally, the formed laminate is cooled and transferred into a mold for curing. The position of the forming tools actuators on the base plates is variable. Numerical optimization in combination with finite element (FE) technologies is utilized, to approximate the tool surface within given error margins, with as few actuators as possible. In addition, results of a numerical method for part quality estimation are shown. The influence of the forming process on mechanical properties due to fiber waviness is taking into account using a self-developed method that includes manufacturing characteristics in FE modeling of the part. The method is based on mathematical descriptions of fiber waviness, which are implemented into a FE model. Therefore a structure discretization assuming perfect fiber orientations is realized and the expected fiber waviness induced by the forming process is applied element-wise.