PSI - Issue 42

6

Marouene Zouaoui et al. / Procedia Structural Integrity 42 (2022) 680–686 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

685

Fig. 6. Bending tests results.

3.2. Failure energy calculation The energy to failure is calculated as the area under the load-displacement curve from the start of the test until the maximum supported load (load at failure). It represents the amount of energy absorbed by the sample to undergo fracture. The energy calculated for the solid specimen is equal to 3.56 J. Adding a cell pattern on the specimen surface improves the capability of the structure to absorb the energy. The honeycomb and the auxetic pattern at 90° have a similar energy to failure equal to 4.43 J and 4.31 J respectively. The auxetic pattern at 0° is displaying the highest absorbed energy 6.71 J. For only a loss in the maximum supported load by 33%, the specimen with the auxetic pattern at 0° can absorb up to 88 % more energy than the solid specimen. 3.3. Specific toughness index To compare the performance of various cell patterns a dimensionless performance index is defined as follow:

w E

i

solid i

= 

(1)

w E

solid

With: : material toughness : Specimen weight

This means that the specimen with the highest energy to fracture and the lowest weight is the most performant. Both honeycomb and auxetic at 90° cells have the same index pattern = 2.28 . This is due to a slight energy increase