Page 41 - MSAM-4-1

Materials Science in Additive Manufacturing TPMS for perfect sound absorption

3.6. Sound absorption of graded TPMS structures

To enhance the sound absorption of the primitive structure,
a graded design method was applied to the primitive
acoustic metamaterials. The sound absorption coefficient
curves of GP-Ⅰ and GP-Ⅱ are displayed in Figure 16, and
the sound absorption characteristics are listed in Table 10.
As the thickness of GP-Ⅰ and GP-Ⅱ increases, the frequency
at the first peak f shifts to a lower frequency. GP-30 mm-Ⅰ
1
has the lowest resonance frequency (1660 Hz) compared
to the graded and uniform structures. Notably, the sound
absorption coefficients at the first peak of GP-Ⅰ are all
higher than those of GP-Ⅱ with the same thickness, and
the frequency at the first peak f of GP-Ⅰ are all lower
1
than that of GP-Ⅱ with the same thickness. The λ peak /T of
GP-24 mm-Ⅱ and GP-30 mm-Ⅱ is lower than 4, indicating
Figure 14. Sound absorption curves of diamond and multicavity- that the type Ⅱ primitive structure has poorer absorption
diamond structures capability than the theoretical periodic porous structures.
On the contrary, the λ peak /T of GP-18 mm-Ⅰ, GP-24 mm-Ⅰ,
and GP-30 mm-Ⅰ are higher than 6, suggesting the presence
λ peak /T of the diamond structure also increases from 4.93 of a subwavelength absorption peak.
to 5.82. The α of the diamond structure with different There are two peaks in GP-18 mm-Ⅰ, GP-24 mm-Ⅰ, and
1
thicknesses is the highest among the four kinds of uniform GP-30 mm-Ⅰ. After a combination of four cavities with 12,
TPMS structures, including gyroid, primitive, IWP, and 18, 24, and 30 mm thickness, five peaks are found in the
diamond. It is demonstrated that the diamond structure curves of multicavity-GP-Ⅰ; the resonance peaks include
has the best sound absorption performance at high 1980, 2420, 3060, 3970, and 5940 Hz. The sound absorption
frequency among these four TPMS structures.
coefficient at the second peak of multicavity-GP-Ⅰ is 0.998,
There are five peaks on the sound absorption curve reaching the perfect absorption. Six peaks are found in the
of the multicavity-diamond structure at frequencies of curves of multicavity-GP-Ⅱ; the resonance peaks include
2070, 2530, 3320, 4660, and 5940 Hz. The first four peaks 1200, 2280, 2850, 3630, 5090, and 5940 Hz. Notably,
of the multicavity-diamond structure correspond to the the α of the first resonance peak of multicavity-GP-Ⅱ
1
resonance peaks of Diamond-12 mm, Diamond-18 mm, is 0.618, and this absorption value is lower than that of
Diamond-24 mm, and Diamond-30 mm; the fifth peak of multicavity-GP-Ⅰ, but the frequency of multicavity-GP-Ⅱ is
multicavity-diamond corresponds to the second resonance lower than that of multicavity-GP-Ⅰ. The sound absorption
peak of Diamond-30 mm. The appearance of five peaks is coefficient at the third peak of multicavity-GP-Ⅱ is 0.988,
related to the interaction between the sound absorption which is close to perfect sound absorption. The λ peak /T of
peaks of the porous structure of four cavities with different multicavity-GP-Ⅱ is 9.65, which is the highest among all
heights in the multicavity-diamond structure, with all five the TPMS structures assessed in this study.
resonance peaks above 0.83. Additionally, the second peak The acoustic band structures of GP-Ⅰ and GP-Ⅱ with
achieves perfect sound absorption (α = 1).
different thicknesses are displayed in Figure 15. The
The acoustic band structures of the diamond structure upper limit frequencies of the bandgap of GP-18 mm-Ⅰ,
with different thicknesses are displayed in Figure 17. The GP-24 mm-Ⅰ, and GP-30 mm-Ⅰ are 4310, 3350, and 2890 Hz,
acoustic bandwidth of the diamond structure decreases respectively; the lower limit frequency of the bandgap of
as the thickness increases from 18 to 30 mm. The upper GP-18 mm-Ⅰ, GP-24 mm-Ⅰ, and GP-30 mm-Ⅰ are 3580, 2800,
limit frequencies of the bandgap of Diamond-18 mm, and 2350 Hz, respectively. The first bandgap of GP-18 mm-Ⅰ,
Diamond-24 mm, and Diamond-30 mm are 3830, 2900, GP-24 mm-Ⅰ, and GP-30 mm-Ⅰ are 730, 500, and 540 Hz,
and 1860 Hz, respectively, and the lower limit frequency respectively. A second bandgap was identified in GP-24
of bandgap of Diamond-18 mm, Diamond-24 mm, mm-Ⅰ and GP-30 mm-Ⅰ at a higher frequency, suggesting
and Diamond-30 mm are 2890, 2070, and 1500 Hz, that the lower limit frequency of GP-Ⅰ shifts to the lower
respectively. The resonance frequency of the first peaks frequency as the thickness increases. The width of the
of Diamond-18 mm and Diamond-24 mm are within the bandgap of GP-18 mm-Ⅱ is 21.9% wider than that of GP-18
above range. mm-Ⅰ; the width of the bandgap of GP-24 mm-Ⅱ is 32%

Volume 4 Issue 1 (2025) 14 doi: 10.36922/msam.5737