Fibre Distribution inside Yarns of Textile Composite: Geometrical and Fe Modelling

This article addresses the experimental investigation and modelling of the uneven fibre distribution inside yarns of a textile composite. The test data is given for the tri-axial carbon-fibre braid; a considerable irregularity is revealed for the fibre distribution along and across the yarns. The importance of this effect for the damage resistance is illustrated with a simple finite-element (FE) model. The geometrical modelling of the internal geometry is also discussed. INTRODUCTION Optimised design methods facilitate an extensive use of textile composites in load-bearing components for different applications. However, being a quite modern design concept, it is relatively unexplored and employed with caution. Due to a natural complex structure and manufacture methods, a textile composite contains resin-rich zones, uneven fibre content, etc. These features raise concerns about the damage resistance, which is closely connected with the reinforcement internal geometry and reveals features not observed in the classical laminates (1–4). Hence, whilst the design for the stiffness of a textile composite part can be based on validated calculation techniques, related to the meso-structure of textile reinforcements, the reliable strength design has to be based on empirical information (5) and should account for the micro-structure. This paper focuses on the uneven fibre distribution inside the textile yarns. The object to study is one of basic types of the textile reinforcement — multi-layer preform made of 2D braided carbon-fibre yarns. The braid is considered as a complex hierarchical structure. Its meso-level includes the variable fibre content along the yarn; this scale naturally corresponds to the unit cell size. The micro-level embraces the uneven fibre distribution over the yarn cross-section.