Virtual prototyping is a cornerstone in modern product development cycles: It accelerates the design process, reduces costs and improves product performance and quality. Highly flexible slender structures like yarns, cables, hoses or ropes are essential parts of high-performance engineering systems. The complex response of such structures in real operational conditions is far beyond the capabilities of current virtual prototyping tools. There is a pressing need for a new generation of young scientists capable of solving fundamental problems related to slender structures and transferring results to applications. THREAD addresses the mechanical modelling, mathematical formulations and numerical methods for highly flexible slender structures. It brings mechanical engineers and mathematicians together around major challenges in industrial applications and open-source simulation software development. It establishes an innovative modelling chain starting from detailed 3D modelling and experimental work to build validated 1D nonlinear rod models, which are then brought to a system-level simulation thanks to the outstanding numerical properties of the developed algorithms. This holistic approach combines advanced concepts in experimental and theoretical structural mechanics, non-smooth dynamics, computational geometry, discretisation methods and geometric numerical integration and will enable the next generation of virtual prototyping. The ESRs will receive comprehensive local and network-wide training covering state-of-the-art research topics as well as valuable transferable skills. They will benefit from close cooperation with twelve industrial partner organisations implementing a comprehensive programme of research secondments and contributing their experience. As a main objective of THREAD, interdisciplinary and inter-sectoral training boosts the career development of young researchers and supports them to solve future challenges.