Effect of preheat temperature on the formability of carbon fibre/PEEK composites

Thermoplastic composites are currently utilised in applications where high specific stiffness and strength is required. However, current manufacturing processes are time consuming and costly. For these materials to be utilised in a wide range of applications, rapid forming mechanisms must be developed. In this study, the formability of carbon fibre reinforced PEEK was examined in stamp forming processes. Composite blanks created from plain weave carbon fabric in a PEEK matrix were formed until failure at various temperatures in an open-die system using a hemispherical punch. Monolithic aluminium samples were formed for the sake of comparison. During forming, real-time strain measurements were taken from the lower surface of the blanks and strain distributions were plotted. Results showed that CF/PEEK experiences a much lower maximum strain than aluminium at any given depth, allowing it to form without inducing failure in the carbon fibres. High temperatures were found to cause large shear strains. This caused a slight reduction in maximum strain in the fibre direction of the composite, slightly increasing the forming depth. A complete understanding of the forming behaviour of CF/PEEK could enable rapid forming processes to be implemented, thereby allowing this material to be utilised in a wide variety of applications.