Yarn-scale analysis of novel textile composites lacking an elementary representative element

Composites architectures evolve and become increasingly complex due to the growing capabilities of manufacturing technologies and sophisticated material designs aimed at optimising load flow, mitigating against damage development, functionalization, etc. Tow steering methods, textile technologies, and advanced draping techniques result in highly-curved fibre paths and complex interlacing of yarns/tows at sub-component level requiring efficient computational approaches to the analysis of stress distribution at the yarn scale. This study demonstrates an example of such novel manufacturing technique.
The method presents 3D printing of a reactive liquid resin into a dry textile reinforcement, followed by consolidation and subsequent resin infusion. The purpose of the print is to stabilise preforms prior to impregnation and functionalise the material. Printing results in a number of interesting structural features: thickness variation in a predefined pattern, local patches with distinctly different properties, fibre-bridged interfaces between printed and infused resin. These features significantly extend the tool box available to manipulate composite properties and, at the same time, reveal a need in a new design philosophy.
The paper discusses mechanical response of these materials and a new numerical approach to assess stress at the yarn scale. Tensile tests, accompanied by optical surface strain measurements, are carried out to explore the material. A pragmatic modelling approach is proposed to overcome the lack of representative volume and understand the influence of complex structural features on composite performance.