Three-dimensional (3D) printed continuous fiber composites are increasingly considered for unmanned aerial vehicle (UAV) secondary structures because of their geometric flexibility and manufacturing efficiency. However, process-induced features such as inter-bead gaps and disbonding between the Onyx wall/infill and continuous carbon fiber (CF) reinforcement can occur during printing. This paper presents a comparative laser ultrasonic testing (LUT) case study of baseline and fiber-misaligned 3D-printed composite UAV propeller pusher caps. Inspection paths were generated using a previously developed computer-aided design (CAD) model-based scan path generation method and implemented in a robotic pulse-echo ultrasonic propagation imaging (PUPI) system for LUT. Two pusher caps fabricated from the same geometry, material system, and nominal fiber pattern were inspected using identical scan paths and inspection parameters. Variable time window amplitude mapping (VTWAM) and averaged 1D ultrasonic signals of the two specimens were interpreted with respect to the printing path, fiber loop arrangement, and expected void and disbonding locations. The nominally printed baseline specimen showed responses associated with inherent printing features, whereas the fiber-misaligned specimen showed additional localized VTWAM and waveform variations consistent with the expected shallow Onyx wall/CF and medium-depth CF/Onyx infill disbonding conditions. Signal-to-noise ratio (SNR) analysis indicated that sufficient measurement quality was maintained over the curved inspection surface. A correlation-based waveform dissimilarity analysis further quantified the matched-location waveform differences between the two specimens. These results demonstrate the importance of combining robotic PUPI results with CAD geometry and slicer-defined fiber arrangement for interpreting manufacturing process related ultrasonic responses in complex continuous fiber 3D-printed structures.

Keywords: Non-destructive testing (NDT), 3D-printed composites, Laser ultrasonic testing (LUT), Robotics