Effect of in situ and furnace thermal annealing on the mechanical properties and sustainability of 3D printed carbon-peek composites

The present work aims at investigating the impact of heat treatments on the mechanical, environmental and economic performances of components in carbon fibre polyetheretherketone (PEEK) composite produced using the Fused Deposition Modelling technique. The mechanical properties of PEEK can be strongly improved by performing heat treatments to maximize the degree of crystallinity in PEEK. To this purpose, the typical annealing heat treatment in a furnace, that is energy and time intensive, was compared to an innovative in situ annealing process named Direct Annealing System (DAS), which is performed during the 3D printing process. In order to evaluate the effect of heat treatment on mechanical properties of 3D printed parts, tensile tests were carried out on samples treated both using the annealing in a furnace and DAS processes. Similarly, the environmental and economic impacts of the different heat treatments were analysed by means of Life Cycle Assessment and Life Cycle Costing methodologies. The results demonstrated that the DAS system allows the improvement of the mechanical properties of carbon fibre PEEK composite, even though the highest performances can be obtained using a heat treatment in furnace. On the other hand, the DAS system is characterized by lower environmental and economic impacts than the annealing in furnace, denoting its more sustainability.