Effects of material and treatment parameters on noise‐control performance of compressed three‐layered multifiber needle‐punched nonwovens

Abstract

The effects of material and treatment parameters on airflow resistivity and normal-incidence sound absorption coefficient (NAC) of compressed threelayer nonwoven composites have been studied. Material parameters included fiber size and porosity, and treatment factors included applied pressure and duration of compression. Fibers used included poly(lactic acid) (PLA), polypropylene (PP), glassfiber, and hemp. Three-layered nonwoven composites were classified based on material content and fiber blend. LHL and PGP were sandwiched structures consisting of PLA/Hemp/PLA and PP/glassfiber/PP layers, respectively. PGI consisted of three layers of an intimate blend of PP and glassfiber. Statistical models were developed to predict air flow resistivity from material parameters and the change in air flow resistivity from compression parameters. Independent variables in the first model were porosity and fiber size and, in the latter model, were compressibility, pressure, and initial mate-rial parameters. An increase in air flow resistivity was found with increased compression. No significant effect of compression duration was detected. Two additional statistical models were developed for the prediction of sound absorption coefficient based on material and treatment parameters. The independent variables of the first model were air flow resistivity, thickness, and frequency, and those of the second model were compressibility, initial thickness, and initial density of the composite, diameter and density of the fiber, compression pressure, and frequency. A decrease in sound absorption coefficient was detected with increasing compression, while no effect of duration was detected.

Acoustic evaluation of Struto nonwovens and their relationship with thermal properties

“…For hollow fibers, as only the pores that carry airflow in connection with the ambient air are of interest in terms of sound absorption, the voids in hollow fibers are not included in the porosity. [27][28][29]…”

Sound absorption and compression properties of perpendicular-laid nonwovens

“…The voids in hollow fibers are not included in the porosity, since open pores that carry airflow with the ambient air are of interest in terms of sound absorption and the closed pores are less efficient than open pores in sound absorption. [12][13][14][15] The airflow resistivity of porous materials indicates some of their structural properties. It was used to establish correlations between the structure of porous materials and their sound absorption properties.…”

Study on Sound Absorption Performance and Transmission Behavior of Perpendicular-laid Nonwovens

“…For hollow fibers, as only the pores that carry air flow in connection with the ambient air are of interest in terms of sound absorption, the voids in hollow fibers are not included in the porosity [17,18,19]. …”