Parameter study and development of a warp knitting yarn compensation unit as basis for the realisation of contour-accurate non-crimp fabrics: a step towards for highly material efficient non-crimp fabrics

Abstract

In response to the increasing demands for high-performance fiber-reinforced composites in structural lightweight construction, this study investigates the limitations of multiaxial non-crimp fabrics (NCF) and their semi-finished products. The current manufacturing constraints of NCF, limited to a constant working width, lead to oversizing in semi-finished textile products and significant material waste throughout the value chain. This study explores the development of NCF with variable area weights and thread densities as a potential solution.The research described in this paper examines the effects of variable area weights and thread densities on textile behavior and warp knitting thread tension in the production of multiaxial NCF. The study focuses on varying key warp knitting parameters (stitch, knitting thread feed value, shape hole geometry), along with the measurement of the tensile force exerted on the warp knitting threads. Findings indicate a consistent increase in warp knitting thread tension in areas of reduced thread densities, unaffected by the fabric’s initial orientation. Higher initial yarn tension and increased yarn demand per stitch correlate with a greater tension increase in areas with lower thread density. This study proposes that refining stitching techniques and integrating adaptive yarn tension control modules could mitigate tension fluctuations and diminish fabric defects. These insights contribute to a better understanding of the material behavior of contour accurate NCF and their production. Coupled with the innovation of a warp knitting compensation unit, these findings mark a pivotal advancement toward producing contour accurate NCF in an inline and higly productive process technology, offering significant implications for the technical textile industry.