FormPATCH - Forming of Complex Composite Structures using Patching Technologies

Abstract

Fiber-reinforced plastics parts produced in medium or large quantities can be manufactured by forming flat textile fabrics to a component contour. Due to the stiffness of fibrous semi-finished products, forming of complex geometries with an uncut fabric is not always possible. Various effects in the fabric structure can occur, that affect the function or design of the final component. Therefore, patch placement of cut fabrics is a common way to build complex geometries. Usually, fewer and larger patches lead to a more economical process as handling steps can be reduced.This paper presents an optimization algorithm for large patch geometries. A possibility to simulate fabric forming and resulting shear deformations is the fast, but approximate, kinematic method. We use state of the art kinematic simulation approaches and enhance them for our purposes with integration in an optimization process. The optimization objective is to generate as few patches as possible to cover the entire geometry. For the simulation, different positioned and randomly distributed starting points are generated that lead to different patches. The algorithm uses Open Cascade’s Computer Aided Design (CAD) libraries and a Qt user interface (library for cross-platform graphical user interfaces). After importing CAD parts, users can run the patch optimization algorithm, or alternatively a classic kinematic simulation by selecting a start point, a direction and fabric properties. Each calculated patch is stored locally in a Scalable Vector Graphics (SVG) file. The SVGs contain shear angles at cross-over points of the textile and, furthermore, the surrounding border of a patch. Saving this border in Drawing Interchange Format (DXF) makes it available for CNC cutters. Finally, we demonstrate the proof of concept by the experimental patching of a generic free-form part with three calculated patch geometries.