Finite element analysis of the formability of carbon fibre/PEEK composite sheets

CF/PEEK composites are currently employed in specialty applications such as medical implants. Despite their excellent mechanical properties, prohibitive material and fabrication costs prevent this composite from becoming broadly utilised in manufacturing. The development of rapid forming processes for CF/PEEK composites could substantially reduce the cost of this material and allow it to replace traditional materials in many high-performance applications. In this study, a finiteelement model for simulating CF/PEEK forming was validated using stamp forming experiments. Circular composite blanks were formed to 15mm using a hemispherical punch, with various blankholder forces partially restraining the edge of the blank. Strains on the lower surface of the blank were measured during forming and compared to those obtained in the numerical simulations. At small forming depths, the finite-element model was found to accurately predict the strain behaviour of the composite. At larger depths the strain at an angle of 45° to the carbon fibres was under-predicted. This was presumably caused by non-linear stress-strain behaviour developing in the later stages of forming. The validation of this model is an important step in developing rapid forming processes for CF/PEEK composites. If the materials forming behaviour can be accurately predicted, then its forming capabilities can be fully characterised. As a result, rapidly formed CF/PEEK could be deemed a suitable material in many engineering applications.