From the PEEK microstructure at welded interfaces to the mechanical properties of thermoplastic composites manufactured by a Laser-Assisted Tape Placement process

The Laser-Assisted Tape Placement (LATP) process of thermoplastic composites enables the rapid production of laminates. However, it generates cooling rates gradients between the surface and the bulk of the plies, probably causing a crystallinity gradient through the thickness of the laminates, although this has not been demonstrated. In this study, different characterizations techniques have been used to highlight this gradient in a carbon-black filled PEEK (CB/PEEK). It was shown that for a 600 μm-thickness ply, only a depth of 100 μm is affected by the laser, resulting in a microstructure less resistant to chemical etching, and low hardness and reduced Young’s modulus related to low crack propagation speed. In the carbon-fibre reinforced PEEK (CF/PEEK) composite, the use of certain characterization techniques requires tough post-processing of the data because of the presence of carbon fibre. As this work is ongoing, this paper focuses on the link between the crystalline and GIC mechanical properties related to the processing parameters. It has been shown that the crystallinity evolves inversely to GIC and layup speed (LS) and in the same way to the tool temperature (TT). Also, for most of the manufacturing conditions studied, laminates have an intralaminar crack propagation.