Advanced Continuous Tow Shearing for manufacturing defect-free complex composite parts

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Current state of the art material deposition technology used to manufacture large composite parts has a limited capability in laying up on double curved surfaces. Fibre steering processes, such as automated tape laying (ATL) or automated fibre placement (AFP) are not capable of producing composite parts with complex geometry without inducing defects like tow gaps or overlaps. The minimum steering radius is dependent on the tape/tow width; Therefore, the steering radius requires to be kept as large as possible in the design phase, which significantly constrains the design flexibility and manufacturability.The novel continuous tow shearing (CTS) technology, developed at the University of Bristol, allows to eliminate defects by steering fibres utilising in-plane shear deformation of the tape or tow. Its greatest advantage is that there is no coupling between the tape width and the minimum steering radius. Hence, even wide ATL grade tapes may be used allowing high material deposition rates.However, this process requires to be improved for complex 3D layup, as it still does not eliminate defects when laying up on double curved surfaces. To date, triangular shaped resin pockets are induced by cutting individual tows during a 3-dimensional complex layup, which have a highly negative impact on the mechanical properties of the composite.The aim of this PhD project is to advance the current CTS technology to enable manufacturing of defect-free 3D complex composite parts. In order to eliminate the tow gaps and overlaps that are inevitably produced in the current AFP process, a novel mechanism that can control the geometry of the tow/tape will be developed, which will eliminate geometry induced defects in production of 3D complex shapes. The Advanced CTS process with this novel mechanism will become an innovative solution to the quality problems of the current AFP process and significantly expand the design space of composite structures, allowing for ultra-high structural efficiency.