Page 94 - MSAM-2-4

Materials Science in Additive Manufacturing 3D-printed composite auxetic structures

A B C

D E F

Figure 3. (A-F) Design of fiber paths.

A digital camera was used to record the deformation displays the deformations of the test specimens under
during the tensile test. The axial and lateral strains tension. All the specimens depicted in Figure 8 were
(ε and ε , respectively) can be derived from the images fabricated using only Smooth PA, allowing for the
y
x
(Figure 7B). The Poisson’s ratio v was calculated using characterization of mechanical properties in the absence
yx
Equation II: of reinforcing fibers.
ε Due to the difference in topology, the deformation
v =− ε x (II) mechanism varies between structures, thus leading
yx
y
to different values of Poisson’s ratio. The observed
3. Results and discussion deformations of the three types of specimens are shown in
Figure 8A. The rotating rigid structure consists of a group
3.1. Deformation behaviors of structures
of squares with different angles, which are connected with
The test specimens were evaluated in uniaxial tensile each other by the intersection of vertices. When the tensile
tests. The deformation behaviors were captured by loads were applied, the movements of individual vertices
the digital camera. It was shown that the topology of drove the rotation of all squares. Afterward, the rotation
the structure had a great impact on the deformation enlarged the space between the squares, and the whole
behaviors and the mechanical properties. Figure 8 structure started to exhibit auxetic behavior. The re-entrant

Volume 2 Issue 4 (2023) 4 https://doi.org/10.36922/msam.2159