Joining of high performance carbon fibre/PEEK composites

Polyetheretherketone (PEEK) is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. For these reasons, it is classified as a high performance thermoplastic. The first reinforced PEEK product was an impregnated continuous carbon fibre pre-preg tape called APC-2, but since then there have been many others. Most of the applications using PEEK involve joining it to itself or to another material; for instance, in the automotive or aerospace industries, lightweight structures need to be joined to metallic surfaces. However, the challenging processability of PEEK due to its high melting point (343°C) and high melt viscosity remains a limitation for its extensive use. This characteristic makes the processing of it time and energy consuming. Even so, interest in this thermoplastic is currently growing, driven by the constant search for lightweight and recyclable materials. Solutions to overcome these process limitations are investigated in this paper through joining of PEEK to similar and dissimilar materials. The common concept behind these solutions is the use of an accelerating agent at the joining interface aiming to produce good welds faster. The main solution investigated is the use of a plasticiser, which is usually used to reduce the viscosity of PEEK and increase its chains mobility.