X-ray computed tomography characterization of 3d-printed acrylonitrile butadiene styrene and polyetheretherketone composites subjected to laser shock peening

The paper deals with X-ray computed tomography results of a polyetheretherketone (PEEK) and a short carbon fibre reinforced by acrylonitrile butadiene styrene (ABS+CF). Individual carbon fibres and 3D printing defects (consolidated structures of interconnected fibres and densified resin clumps) are detected on an initial microstructure of the ABS+CF composite. The carbon fibres and the consolidated structures are densely packed with uniform sub-horizontal locations throughout in a sample volume. In the PEEK samples, the process-induced defects during the composite manufacturing process are visualised as tubular structures of a densified resin with internal voids. Significant changes in the structure of both composites are observed after five times pulsed laser shock peening. In case of a single pulse exposure and a surface treatment, no microstructural changes occur. In a test mode without a protective layer, a material evaporation to a depth of 0.3 mm and a structural degradation of the PEEK samples takes place, while the process-induced interlayer voids do not close. A single consolidated area with a porous spongy structure occurs due to melting of the carbon fibres in the ABS+CF composite. The results show that the laser shock peening has a significant effect on the surface microstructure. It is therefore necessary to carry out further experiments to select the optimum laser shock peening parameters and a protective layer material to eliminate the process-induced defects and improve the strength properties of the composites.