TWI Core Research Project 1123/2020
For the purpose of this project, continuous fibre carbon reinforced PEEK (Polyetheretherketone) thermoplastic composite (CFRTPC) was joined using linear friction welding (LFW). Thanks to a PEEK sacrificial interlayer, the strength of the joints produced matched, without any surface pre-treatment, the typical strength of an adhesively bonded joint.
The rising production rates of the aerospace industry are most likely to be met using thermoplastic composites which, unlike thermoset composites, do not suffer from long cure schedules. Thermoplastic composites can also be joined by thermal welding processes.
LFW is a rapidly developing, solid-phase metals joining process. It is a key technology for critical aero-engine components and is now being qualified for use on aero structures. LFW would typically degrade continuous fibres at the weld interface during welding (Taylor and Jones, 1989) and its application to continuous CFRTPCs has not been achieved.
Adhesively bonded carbon/PEEK laminates have demonstrated joint strengths of up to 28MPa but only after the application of appropriate surface treatment.