Optimisation of properties and dimensional stability of composites by controlled fibre placement

• Research unit: COST
• Project number: C01.0090

Key words (English)

Structural optimisation; finite element method; composite materials; integrated processing; fibre placement

Research programs (English)

COST-Action 526 - Automatic Process Optimization in Materials Technology

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise: EPF Lausanne Département des Matériaux Laboratoire de Technologie des Composites et Polymères

Partners and International Organizations (English)

BE, CZ, DK, FI, FR, DE, HU, PL, SI, CH, UK

Abstract (English)

Manufacturing of multi-material composite structures using integrated processing is a novel concept that offers the unique possibility to combine different materials in a rational and cost effective way. The structural advantages of aligned, continuous fibre materials can be combined with the geomet-rical advantages offered by net shape flow based processes, such as injection and compression moulding. Use of the more costly continuous fibre materials is limited and these are efficiently used, thus minimising material cost. The potential of this novel concept is generating considerable inter-est, especially from the automotive industry. The aim of this research project is to develop the techniques and tools necessary so that the prop-erties of such structures could be understood, predicted, and optimized during development of in-dustrial applications. The project includes the following three topics: prediction of warping during processing, prediction of the structural, non-linear load-displacement behaviour and the optimization of the placement and amount of reinforcements. A visco-elastic spring back analysis of a compression moulded fabric part has been performed. The simulation uses a user material subroutine in conjunction with ‘ABAQUS’ to model the orthotropic, visco-elastic material behaviour. Composite material properties are obtained from a dynamical me-chanical thermal analysis of the matrix material and micro-mechanical equations. Results show good agreement between predicted and measured spring back angle. As a starting point for the later optimization step, effective 2D shell element based finite element models were developed and compared to detailed 3D solid element models and experiments to ver-ify the accuracy level. An elastic-plastic material model was applied for the over-moulding polymer whereas a linear elastic orthotropic model was used for the tow material. It is shown that that the results from the 2-D models compare favourably with the ones from the 3-D model as well as ex-periments and that 2D models are well suited for use in the optimization step. The optimization work is based on response surface methods and is divided into two parts; the first is an initial simplified problem study using the “sub-problem” method in the commercial finite ele-ment code ‘Ansys’. The second part is a study of a more realistic beam type structure using the general purpose optimization code ‘iSIGHT’ in conjunction with the finite element code ‘Abaqus’. The accuracy of polynomial approximations with and without term selection, radial basis functions and Kriging approximation are evaluated for the current type of non-linear structures and the best one is used as a surrogate model in the following optimization step. A genetic algorithm is applied due to its ability to handle complex and discontinuous design spaces, discrete variables and make use of parallel processing. It is concluded that the developed optimization methodology seems well suited for application to non-linear, hybrid material structures.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C01.0090