Experimental quality assessment of thermoplastic composite corner regions manufactured using laser-assisted tape placement

Over the past 25 years, interest in thermoplastic composites in aircraft has steadily increased. Combining winding and laser-assisted tape placement is a promising method to manufacture thermoplastic structures using in-situ consolidation, as shown recently by manufacturing a variable stiffness, unitized, integrated -stiffener thermoplastic wingbox at the University of Limerick. The corner regions are a critical point of the structure and require in-depth characterization studies, for example by unfolding L-shaped samples in a 4-point bend test. In this work, samples with radii varying from 2 to 10 mm were manufactured and tested. Two manufacturing parameters were varied: the rotational speed and acceleration of the tool. Test data show that decreasing the radius increases the corner strength, but an optimum radius exists to withstand a maximum unfolding force/moment. In addition, the slowest deposition rate with least acceleration of the head used during manufacturing lead to the highest corner strength for the same radius.

Automated summary

Interest in thermoplastic composites in aircraft has been increasing over the past 25 years. Combining winding and laser-assisted tape placement is a promising method to manufacture thermoplastic structures. In this study, a variable stiffness, unitized, integrated-stiffener thermoplastic wingbox was manufactured and tested. The corner regions were found to be critical and testing showed that decreasing the radius increases the corner strength, with an optimum radius existing to withstand maximum unfolding force/moment. The slowest deposition rate with least acceleration during manufacturing resulted in the highest corner strength for the same radius.