Page 68 - MSAM-2-1

Materials Science in Additive Manufacturing Energy absorption of Moore’s thin-walled structures

A B

C D

Figure 8. Effective stress- strain curves obtained from cyclic compression tests for structures with a relative density of 20%: (A) 2 order from loading
nd
direction 1 (LD1), (B) 2 order from loading direction 2 (LD2), (C) 3 order from LD1, and (D) 3 order from LD2. The pictures of the specimens are the
nd
rd
rd
configurations before and after the cyclic tests.
A B

Figure 9. Comparisons of effective stress-strain curves obtained from quasi-static compression experiments and FE simulations for 2 order fractal
nd
structure with a relative density of 20% from (A) loading direction 1 and (B) loading direction 2.
As displayed in Figure 9B, the effective stress (Equation When comparing the response from LD1 to LD2, the
II) within the 1 order structure in the experiment dropped difference between the experiment and the simulation was
st
drastically at a strain of 22%. However, there was no obvious slightly smaller. This phenomenon is a result of the design
reduction in stress, but rather a long phase of plateau from of structures. As shown in Figure 4A and B, the total contact
the numerical simulation. In other words, no snap-in surface between the compression plates and specimens was
was observed in the FE modeling. This is ascribed to the larger in LD1 (Figure 4A). All the specimens deformed
perfectly symmetric parts and ideal boundary conditions symmetrically in the FE models considering the symmetric
in the numerical model. Meanwhile, the experimental design. During the experiment, structures with less contact
condition and 3D-printed specimens differed from what surface were more prone to deform asymmetrically due to
was established in the modeling. It is widely known misaligned loading conditions or manufacturing defects.
that defects commonly exist in FFF technology using
[49]
carbon fiber-reinforced polymer . Any misalignment of 3.3. Stress distributions
compressive loading or imperfections within the fabricated Failure of engineering components is mostly due to stress
structures could give the structures opportunity to behave within the structure. The stress distribution reflects the
in an asymmetric way, leading to the snap-in phenomenon. level of structural design and affects the structural safety

Volume 2 Issue 1 (2023) 9 https://doi.org/10.36922/msam.53