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Details of Grant 

EPSRC Reference: EP/P027288/1
Title: Novel Tow Termination Technology for High-Quality AFP Production of Composite Structures with Blended Ply Drop-offs
Principal Investigator: Kim, Dr B
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Airbus Operations Limited BAE Systems National Composites Centre
Rolls-Royce Plc (UK)
Department: Aerospace Engineering
Organisation: University of Bristol
Scheme: First Grant - Revised 2009
Starts: 01 July 2017 Ends: 31 December 2019 Value (£): 101,114
EPSRC Research Topic Classifications:
Manufact. Enterprise Ops& Mgmt Manufacturing Machine & Plant
EPSRC Industrial Sector Classifications:
Aerospace, Defence and Marine Manufacturing
Related Grants:
Panel History:
Panel DatePanel NameOutcome
03 Mar 2017 EPSRC Manufacturing Prioritisation Panel March 2017 Announced
Summary on Grant Application Form
The automated fibre placement (AFP) process is a cutting-edge technology to manufacture complex composite aerospace structures, which was first developed in the early 1980s. This process lays down a set of pre-impregnated carbon fibre tapes called 'slit tape' or 'tow' following designed paths on a 3D surface. Despite increasing demands for the fibre placement technologies, the process-induced defects in fibre placement process are critical problems that need to be solved so as to guarantee the quality and structural reliability of composite aircraft components. Those defects mainly result from the limitations of the modern AFP machines.

One of the major limitations is that they always generate resin pocket defects when producing composite components with thickness variation by terminating the tows inside the laminates. The conventional guillotine tow cutting mechanism, which almost all modern AFP machines are adopting, creates stepped tow ends when cutting the tows. Although the tow thickness is quite small (~0.12 mm), empty gaps are produced when the next ply covers the ends due to the high bending stiffness of the carbon fibres. The gaps are filled with resin matrix after a curing process, and act as crack initiation points under loading. This is an example how a manufacturing limitation can increase the design complexity and manufacturing cost. This provokes complex design problems to optimise the tow termination locations considering their detrimental effects on the structural performance, which significantly delays the design process and increases the design cost.

The conventional approaches dealing with these defects have been mainly about how to quickly and accurately predict their detrimental effects on the structural performance and take them into account in the design stage. However, this project aims to provide an inventive solution to eliminate those defects by tackling the fundamental weaknesses of the concept of modern AFP machines, which is a tow scarfing mechanism that can taper the tow ends when the machine terminates the tows during the automated lay-up process. This novel mechanism, which has never existed before, will allow for eliminating the resin pocket defects in automated manufacturing of composite aircraft components, ensuring high quality and reliability of the end products. At the same time, the design process as well as the post-performance evaluation process can be shortened and simplified by removing the effort to take into account the process-induced defects. The objectives of this project are not only for developing a new mechanism but also for providing fundamental understanding of the mechanics in tow cutting process and how the geometry of the terminated tow end affects the internal load transfer and failure mechanism. This project is ultimately for establishing a design guideline supported by experimentally validated data to effectively use the advantages of the new tow termination method.
Key Findings
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Organisation Website: http://www.bris.ac.uk