AbstractFibre steering is a novel concept in composites engineering, which promotes the use of curvilinear fibre paths. It can significantly expand the design and manufacturing space for composite materials, by enabling optimised designs and shapes that are not possible with conventional straight fibre designs. The automated material placement process is the most advanced manufacturing technology that enables fibre steering. Nonetheless, the steering capabilities of modern placement machines are limited, as they bend the tapes to steer the fibre paths, causing significant defects, such as fibre buckling and gaps and overlaps.
To address this manufacturing issue, a novel fibre steering concept, named Continuous Tow Shearing (CTS), was developed at the University of Bristol. The CTS can align fibres along a curved path without causing fibre buckling, by shearing continuously-fed tapes. Unlike conventional placement machines, as CTS relies on shear deformation, there is no coupling between the material width and the minimum steering radius that can be achieved. The aim of this research was to exploit this feature and develop a wide tape placement system that can produce high quality fibre steered laminates. Furthermore, the original concept of CTS, where only dry carbon tapes were used, was expanded for use with both unidirectional dry fabric and prepreg tapes.
In this research, a wide tape CTS prototype was developed and the effect of process and material parameters on the steering quality, while using dry and prepreg tapes was assessed. In the case of dry unidirectional fabric tapes, the steering quality was primarily affected by material parameters, such as the weft yarn pattern, rather than process conditions. On the other hand, during steering of unidirectional prepreg tapes, the quality was significantly affected by both material parameters, such as the viscoelastic properties of the resin system, as well as process parameters such as layup temperature and tape tension.
The wide tape CTS prototype achieved a minimum steering radius as low as 50 mm while using 100 mm wide prepreg and dry fabric tapes. This steering radius is several orders of magnitude smaller compared to that of the current state-of-the-art commercial placement machines. The CTS is the world’s first technology that enables fibre steering with wide tapes and can thus be employed in niche application fields in which the current material placement machines cannot operate.
|Date of Award||23 Jan 2019|
|Supervisor||Byung Chul (Eric) Kim (Supervisor), Paul M Weaver (Supervisor) & Kevin D Potter (Supervisor)|