Numerical characterisation of the mechanical behaviour of a vertical spacer yarn in thick warp knitted spacer fabrics

Warp knitted spacer fabrics (WKSF) are technical textile structures that present special compression-elastic, air permeability, heat resistance and acoustic damping properties and because of that they are winning more application fields every day. In many of these fields, like the application for cushion structures in car seats and mattresses, the thick WKSF are of special interest and the mechanical behaviour of these structures needs to be known in detail but, although direct relationships exist between the textile technical and technological parameters and the mechanical behaviour of the mentioned structures, this characterisation is still being carried out experimentally. Analytical and numerical models have already been developed to study WKSF structures offering interesting contributions to a better knowledge of their behaviour and providing further research directions but there are some phenomena causing the particular and characteristic mechanical behaviour of these structures that have not been described yet. The aim of this paper is to give a better understanding of the mechanical behaviour of a single vertical spacer yarn of a thick WKSF under compression load by studying, with help of the finite elements method, the variations of the bending moment acting on the yarn during the compression process. In this article it has been found that these variations of the mentioned bending moment are the phenomena responsible for the characteristic mechanical behaviour of the WKSF structures.