Issue 73

V. Tomei et alii, Fracture and Structural Integrity, 73 (2025) 181-199; DOI: 10.3221/IGF-ESIS.73.13

i,TR n F = σ t w  

(5)

  

  

t



 

(6)

F = σ

1-

t w

i,BR b

h

1

Considering an average value of maximum normal stress σ n,max equal to 44 MPa and an average value of maximum bending stress σ b,max equal to 51 MPa, both F i,TR and F i,BR are equal to 3.5 kN. These findings confirm the consistency and reliability of the experimental results obtained from different testing setups, demonstrating good agreement in terms of stress strength and highlighting the repeatability of the results. Furthermore, the results obtained from the dog-bone samples are useful for characterizing the material in terms of stiffness, strength, and post-peak behavior, providing fundamental information for developing numerical models aimed at predicting the response of structural elements designed with this material. Additionally, the tests performed on the structural samples are crucial for validating any proposed numerical model. In this context, it is important to consider that the information of the material behavior is valid for samples printed with the same parameters described in the previous sections. For this exploratory study, the focus has been placed on the idea of creating panels with continuous outer edges, while featuring an internal structural pattern that reduces the material usage, resulting in a significantly lower weight compared to solid panels. The evaluation of the stresses is also useful for better understanding the advantage of using panels with an internal truss structure within the thickness rather than solid panels. In fact, considering a solid panel with a thickness equal to the sum of the thickness of the two flanges of the truss scheme (as if the two flanges are merged to form a solid panel), the same external force applied in a three-point bending test like described in Fig. 11d would result in a much higher stress. For example, considering an applied force F of 3 kN, the corresponding maximum bending stress σ b,max in the reticular structure is about 34 MPa, calculated with Eqn. 4, with d* equal to 1 2 h - t 3       . Conversely, in the solid panel, the internal lever arm distance between internal forces d* is significantly smaller, equal to 4 3 t, leading to a stress of approximately 176 MPa, calculated with Eqn. 4. This simple calculation demonstrates that, given the same flange thickness in the reticular structure and the same solid wall thickness, the reticular configuration is significantly more efficient, as the stress generated under the same applied force F is considerably lower.

0 10 20 30 40 50 60 0 0.5 1 1.5 2 2.5 3 3.5 σ n (MPa) Δ (mm) Tension Test

TR_60 TR_72 σ lim (DG)

(a)

195