Analysis and finite element simulation of the draping process of multilayer knit structures and the effects of a localized fixation

Abstract

Fiber reinforced composites (FRC) are an interesting alternative for numerous applications due to their lightweight character. However, there are currently several challenges for a serial production. The manufacturing process still requires a high percentage of manual labor which greatly restricts the reproducibility. Additionally, high-quality standards necessary for many applications cannot be met due to the low displacement resistance of the textiles. Structural fixation could greatly improve the displacement resistance and therefore the handling of the material layers. This paper reports on a model used for draping simulations of nonfixed and fixed multilayer knits using the commercial finite element software LS-DYNA®. The aim of this model is to improve the development process of FRCs. With a standardized specification, the basic macromechanical properties can be modeled with finite shell elements. A material model is introduced that accounts to the characteristic mechanisms of the deformation of biaxial fibrous structures. A fixation of the fabrics is achieved by melting the thermoplastic hybrid yarns embedded in the textile structure with infrared radiation. This process improves the handling of the textiles. It is of great benefit when such a structural fixation is applied locally. The process of choosing local fixation zones is described in this paper and the applicability of this process is illustrated.