A method for investigating blending quality of commingled yarns

A prospective technology for manufacturing thermoplastic composites is based on hybrid commingled yarns. The hybrid yarns are further processed into semi-impregnated thermoplastic preforms in the form of woven or non-crimped fabrics, which are consolidated and molded in a single processing step. The quality of the component distribution in yarn is known to affect the mechanical properties of the manufactured composites. As part of a quality management system for the manufacturing process of thermoplastic composites based on commingling yarns, a new method for analyzing the blending quality along the length of commingled structures is presented in this work. By using this method, a new blending index ( k b,yarn ) is introduced as a measure of the quality of commingled yarns. The blending index combines the existing coefficients of the lateral and radial distribution of fibers in the cross-section of hybrid yarns. Within this paper, the new analysis method is explained in detail using the example of glass fiber/polyamide 6 (GF/PA) commingled yarns. Due to the combination of the yarn analysis along the yarn axis and in its cross section, the new method allows for the first time a reliable comparison of the blending quality in commingled yarns used for the manufacturing of thermoplastic composites.