A. Willems, Forming simulation of textile reinforced composite shell structures, 2008

Abstract

Composites are potential candidates to replace metal, aluminium or titanium for weight reduction or other design reasons in various applications like transportation, sports equipment, consumer goods. Composites are heterogeneous materials composed of a reinforcement and a matrix. The reinforcement usually consists of fibres, and provides the composite stiffness and strength. The matrix is usually a plastic or resin and assures load transfer by binding the fibres together. Textile composites have a textile reinforcement and manifest good impact and fatigue resistance.

The production of textile composite shell products requires the drape of dry or matrix-impregnated textile sheets over molds. During the drape forming, the textile undergoes large deformations. These deformations affect the subsequent production steps and final product quality, and may result into drape-related faults. The nonlinear finite element method supports the process optimization by predicting the fibre orientations and other deformations on the product. This requires the development of suitable material models that incorporate the anisotropic drape behaviour of these textiles and that track the fibre orientations.

The first objective of the dissertation is to critically evaluate and improve two test methods that characterize the in-plane shear and biaxial tensile behaviour of these textiles. These tests generate necessary input data for the material models, but unfortunately lack standardization. A second objective is the development of an elastic macro-scale material model that accurately incorporates the in-plane drape behaviour. First, state-of-the-art models are theoretically investigated and tested in-plane. Furthermore a new material model is proposed, differing by the fact that it incorporates in a pragmatic manner both typical tensile and shear behaviour, and handles arbitrarily large deformations. Finally, the predicted fibre orientations are compared to experimental data in three forming case studies. Additionally the sensitivity of the fibre orientations to variations in the material data and process conditions are investigated. The blankholder configuration and the mold geometry were the most influential parameters for the studied reference material.

Order Code

Code: 08D12