Surface Defects Sensitivity during the Unfolding of Corrugated Struts Made by Powder‐Bed Additive Manufacturing

Corrugated struts as part of lattice structures can lead to novel mechanical behavior by a combination of material and geometrical hardening. The unfolding behavior of such struts offers a potential of large macroscopic straining. However, their ability to be unfolded is impacted by the surface characteristics inherited from the additive manufacturing process. Herein, the unfolding sensitivity to these surface characteristics is evaluated. Corrugated struts with varying surface roughness are produced using a combination of electron beam powder‐bed fusion to produce corrugated samples with different nominal diameters and chemical etching assisted by micro‐computed tomography (CT) to achieve a given final diameter. In situ micro‐CT tensile tests are conducted to track the evolution of the struts morphology under loading. Surface defects play a significant role in the unfolding ability of such struts. They are characterized either by a global roughness or by a local notch depth. A quite broad unfolding dispersion remains for samples with the same level of roughness. A finer description of notch depth and location within the gauge length allows a more accurate prediction of the unfolding ability. A model for predicting the probability of failure during unfolding is presented.