PSI - Issue 42

Theodoros Marinopoulos et al. / Procedia Structural Integrity 42 (2022) 903–910 T. Marinopoulos et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Recent studies proved that the interlayer bond can have the same properties as the bulk material and that the naturally occurring grooves between the printed layers are the cause of failure due to high stress concentrations (Moetazedian et al., 2021). Direct control of the printing path and its parameters can be achieved using custom gcode software FullControl (Gleadall, 2021). It can enable the users to minimize the effect of these notches and take advantage of a larger/wider bonding surface to improve the mechanical performance of the prints. A more in-depth study on the benefits of wider layer bonding is also conducted and prepared for a different publication. Another important parameter was found to be the material used. The design was established to be less effective compared to the material. Even though PLA was used in both cases, and printing parameters were within the manufacturer’s suggested range, a significant difference in the results was observed. The effect of the color and the various additives in the manufacturing of the filaments was addressed previously, but further investigation are necessary, especially for medical applications that require a high safety factor.

Figure 7. Maximum load-bearing capacity for original, 4.5 mm and 6 mm redesigned sockets printed in bPLA

Figure 8. 3D microscopy of crack surface of failed sockets printed with different infill pattern: (a) 3 walls and zig-zag infill; (b) 3 walls and concentric infill pattern 5. Conclusions In this study FEA models were developed to investigate the stress distribution in the prosthetic socket at the heel strike stance. Stress results were used to re-design the socket for improved mechanical performance.