Paper number 253

STIFFNESS OF THE SKINS OF 3D-KNITTED COMPOSITES

Dirk Philips, Ignaas Verpoest

Department of Metallurgy and Materials Science,
Katholieke Universiteit Leuven, de Croylaan 2, B-3001 Leuven, Belgium

Summary

Open 3D-knitted composites have been around for several years now. So far, most of this time was used to adapt the 3D-knitted textiles for composite applications. Some preliminary work was presented earlier on the bending properties of these materials [1]. In this paper, one takes a closer look at the skin stiffness which depends on the material properties but also to a large extent on the geometry of the unit cells. One of the most important parameters will be the degree of expansion of these cells. The properties of the skins are studied by 3point bending tests on the full sandwich structure. These results are then compared with the stiffness obtained from tensile tests on the skins. The relation between the results of these two methods seems to be linear but the bending tests always underestimate the real skin stiffness. A third method to determine the skin stiffness uses Finite Element Modelling. Here, the influence of all kinds of parameters was examined and these results were then compared with those from experiments.

Keywords

Knitted fabrics, textiles, sandwich structures, stiffness, modeling, skin.