Process characteristics, damage mechanisms and challenges in machining of fibre reinforced thermoplastic polymer (FRTP) composites: A review

Fibre reinforced thermoplastic polymer (FRTP) composites have been used for a wide range of engineering applications (e.g. in transport, construction, energy, etc) due to their excellent mechanical properties and ease of repair and recycling. In recent years, FRTP is increasingly deployed as an alternative to conventional thermoset carbon fibre reinforced epoxy (CF/epoxy) composites, for the purpose of reducing the carbon footprint and contributing to a sustainable manufacturing agenda. Machining of FRTP remains an indispensable process to achieve rapid parts assembly whilst meeting stringent geometric tolerances. However, due to the heterogeneous structure and high thermal sensitivity of FRTP, a range of machining-induced damages (such as matrix smearing, thermal degradation, delamination, burr and surface cavity) often occur, leading to concerns on machined parts quality and reliability. To date, composite machining studies have been mostly focused on conventional thermoset CF/epoxy and there is a lack of an up-to-date, in-depth review of the latest advancement concerning the machining of thermoplastic FRTP. This paper provides a state-of-the-art overview on the recent developments in FRTP machining over the past decade, with a particular emphasis on machining characteristics, damage mechanisms as well as the challenges facing such manufacturing process. The purpose is to present the composite manufacturing community with a timely update, which may guide and inspire further research and development for future FRTP manufacturing.