Page 42 - MSAM-1-4

Materials Science in Additive Manufacturing Acoustic performances of SC lattices fabricated by DLP

accurately characterize the acoustic properties of the lattices The cylindrical lattice samples were manufactured
by first choosing the correct model by a design criterion, and using vat photopolymerization using the Voxelab Proxima
then calculating the most appropriate geometrical parameters 6.0 printer. The choice of the process was derived from the
or correction factors for the model based on the lattice comparison of the various AM processes as discussed in
geometry. This work will be of significant utility to materials section 1. The solid-based and powder-based technologies,
researchers who are studying the acoustic properties of such as material extrusion and powder bed fusion, are not
novel porous materials, as well as manufacturers of acoustic suited for our fabrication due to the poor surface quality
materials interested in the AM of lattice structures for sound of the printed samples. Moreover, compared among
absorption and insulation applications. the market-available technologies and machines, vat
photopolymerization is the most suitable AM process to
2. Experimental and numerical methods be used in this work due to its reasonable material costs, a
2.1. Fabrication of simple cubic lattices small quantity of resin during the build as well as minimal
shrinkage. The resin used was the standard 405 nm UV
The unit cell design of the SC-Truss lattices in this work is resin from NOVA3D, chosen due to its high toughness and
shown in Figure 1. The unit cell is in the form of a cube strength. A layer thickness of 0.05 mm and an exposure
with a side length D , and the struts of the unit cell is made time of 2 s were used during printing. These printing
of cylindrical rods of radius R . The unit cell was then parameters were determined based on the experimental
repeated to form a lattice structure of diameter 30 mm and determination of the optimal parameters for the printing
height 30 mm, with truncations done to model the of samples using the chosen printer and resin. As-printed
structure as a cylindrical structure. The cylindrical shape parts were cleaned by immersing in isopropyl alcohol and
of the lattice structures was chosen for sound absorption post-cured in a UV curing chamber.
measurements using an impedance tube of cylindrical
cross-section, as detailed in section 2.2. The ranges of strut 2.2. Acoustic performance characterization
lengths used in this work were D Î {3.0, 5.0, 6.0, 7,5}, The sound absorption coefficient (α) and sound transition
which gave a total of 10, 6, 5, and 4 layers of unit cells in the loss were tested by the BSWA SW477 impedance tube
structure, respectively. The base case in this work is one
that had unit cell dimensions of D = 5.0 mm and Table 1. Design parameters of samples
r = 1.03 mm, which gave a relative density of 0.3 for the
lattice structure. This choice of dimensions allows for Sample Strut length D (mm) Strut radius R (mm)
comparisons with other related lattice sound absorption 1 3.0 0.43
works done by our research team in the past . The strut 2 3.0 0.63
[23]
radii r were varied in steps of 0.2 mm such that the 3 3.0 0.83
porosities of the lattice structures fall between 0.4 and 0.9. 4 5.0 0.63
The list of strut lengths and radii for the lattice structures 5 5.0 0.83
in this work is tabulated in Table 1.
6 5.0 1.03
7 5.0 1.23
8 5.0 1.43
9 6.0 0.83
10 6.0 1.03
11 6.0 1.23
12 6.0 1.43
13 6.0 1.63
14 6.0 1.83
15 7.5 1.03
16 7.5 1.23
17 7.5 1.43
18 7.5 1.63
19 7.5 1.83
20 7.5 2.03
Figure 1. Schematic diagram for SC RUC with dimensions strut length
D and strut radius R. 21 7.5 2.23

Volume 1 Issue 4 (2022) 3 https://doi.org/10.18063/msam.v1i4.22