Application of Evolutionary Algorithms on the Draping Process
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The production of fibre reinforced plastics with resin infusion processes requires the usage of textile preforms. The production of the aforementioned is lavish and expensive. Especially the draping steps in the course of the preforming process chain offer significant potential for improvement and are therefore the main focus of two projects at RWTH Aachen University.
Design of the Draping Process
The project Optidrape addresses the geometry specific design of the draping process for fibre reinforced plastics (FRP) components.
In order to be able to produce FRP in large scales, it is necessary to reduce the costs per component by a significant amount. Based upon this, draping is a key process within the preforming process. Draping results influence subsequent production steps as well as the overall quality and strength of the final component. Taking this into account it is problematic that small and medium-sized companies often perform the draping process manually and renounce any simulating software because of high licensing costs. The aftermath is unsteady and deficient draping results as well as high costs for fixing the consequent errors and component scrap.
The algorithm determines an optimal component geometry that guarantees the best possible drapeability.
Determinants of Draping Quality
In this context the pivotal factors for draping quality are material, process and component geometry. The influence of material and process on the draping result has already been examined and discussed extensively in scientific literature. But a systematic analysis of the component geometry is lacking, so that there is still a large room for improvement within this specific area.
Originating from the component geometry, FRP components cause in general higher development expenses than classic construction materials like aluminium and steel. The causes for this circumstance are the complex material properties as well as the state of the art production processes. Up to 33 % of the overall component costs are being caused by the product development while the remaining 67 % are due to the production of the component itself. Additionally the design of lightweight components is often determined by substituting the metallic material with FRP. In the aftermath the great potential of FRP remains unused because of an inappropriate conception regarding the material. There have been first attempts to realize FRP appropriate concepts, but these still neglected the resulting drapeability as well as the overall fit for the preforming process.
Aim of the Optidrape Project
Based upon these circumstances it is desirable to be able to illustrate the drapeability of textiles with appropriate simulation software. Thus it is possible to predict draping-effects depending on the technology. Subsequently a reproducible and standardized draping process is feasible. Yet small and medium-sized companies are either lacking experience in Finite Element(FE) simulation or the occurring costs are not economically justifiable for them.
By applying the systematic approach a selection of fitting textiles can be elaborated for a predefined geometry.
Therefore it is the aim of the Optidrape project to improve the draping process in order to be able to pave the way for a material appropriate conception of FRP components. This consequently leads to an increased quality of FRP preforms as well as a reduction of the resulting development costs and time.
Optimisation of Geometry and Drape Result
Yet the selection of the best textile does not warrant an error free draping result. Hence the component geometry is being optimised within the Optidrape approach. For this purpose the Institut für Unternehmenskybernetik (IfU) at the RWTH Aachen University develops an evolutionary algorithm that calculates an optimal component geometry within multiple iteration steps. The necessary data is being determined by an evaluation function through machine learning. Causalities between the input data and the preforming result are being deduced in this context on the basis of preliminary studies as well as the previously created drape catalogue. Due to these causalities, the evolutionary algorithm is consequently able to determine an optimal component geometry that fits the required mechanical properties as well as guarantee the best possible drapeability.
An early implementation of the Optidrape approach enables to reduce the product development time in comparison to conventional approaches. Furthermore the necessity of a costly FE simulation software can be omitted.
Drapefix project aims to reduce the forming forces by 50 %.
Local Binder Application
Aim of the Drapefix Project
Origination from these problems, the Drapefix project aims to reduce the forming forces by 50 % as well as to realise a textile and load appropriate forming of the 2-D-layer packages. Therefore draping errors can be reduced and the usage of smaller presses is being encouraged. Subsequently smaller competitors might be able to diversify further into the FRP segment as well as tap into new markets.
Optimal Binder Paths
Subsequently the concept of machine learning is applied analogous to the Optidrape approach in order to deduce causalities between input (component geometry, pattern of binder application, pressure) and output (overall quality of the textile preform). These relations are being used for the development of an evolutionary algorithm at the IfU. By using the algorithm it is thereupon possible to determine an optimal local binder path for the predefined component geometry.
By using the algorithm it is possible to determine an optimal local binder path.
Draping — A Key Process of Preforming
Both projects are being funded via the AiF by the Federal Ministry of Economic Affairs and Energy (BMWi) according to a decision of the German Federal Parliament. We would like to thank all project partners and companies for their support and financial aid. The duration of Optidrape is March 2017 to February 2019, the duration of Drapefix is June 2017 to May 2019.