Manufacturing of pre-impregnated discontinuous CF/PAEK composite

Abstract

High temperature engineering thermoplastics such as the PAEK family of polymers, are now finding increased application in advanced composites structures. Polymers and polymer processing are at the heart of the manufacturing sector, with a huge number of uses. However, in many advanced applications, metals are chosen because conventional polymers either cannot deliver the required mechanical performance or are thermally vulnerable. PAEK can overcome these obstacles and are now transforming the landscape of materials usage, offering far more than just lightweight replacements for metals. Some PAEK’s can operate continuously at 260°C and many are resistant to ionising radiation, corrosion, abrasion and stress-fatigue, have low toxicity, and very importantly – because of their linear molecular structures – they are mechanically tough. Indeed when reinforced with carbon fibre, as part of a thermoplastic composite (TPC), their properties far outshine traditional thermoset matrix composites in terms of toughness, without loss of strength or stiffness, while significantly reducing production costs. Due to the above characteristics; unique to TPC only, these composites have found applications in most industry sectors, e.g. in aerospace: ducting, cable housings, bracketry, elevator tail sections and rudders, shear webs for localised reinforcement, seat frames and floor panels. PAEK carbon fibre moulding compounds are the latest TPC format, where material consists of short lengths of pre-impregnated discontinuous 25mm aligned carbon fibre tapes. These tapes or chips, present a major advantage over conventional prepreg sheets, in that they can flow and form to a mould, and potentially are far less labour intensive, making mass production of PAEK/ CF parts possible. The possibilities of PAEK/ CF tapes are only just starting to be explored, where the relationship between processing conditions and resulting composite properties is not yet defined. A major factor is the exposure of these compounds to extended thermal cycles during processing – which can be extremely detrimental to mechanical properties This work seeks to closely define the processing-properties relationship for these advanced materials and provide manufacturers and industry with the processing information required to control the key parameters during manufacture and thereby optimise resulting properties of moulded PAEK/ CF composites.