Airflow resistance measurement of fibrous materials at high temperatures for acoustical applications

The acoustic performance of fibrous materials is mainly determined by its airflow resistance, and it is a parameter of the resistance that the airflow meets through the materials. This paper has summarized the recent advances on the measurements, calculations and applications of airflow resistance. Firstly, different methods for airflow resistance measurements are presented, mainly including the direct airflow method, alternating airflow method and acoustical method. We have summarized the development history, current status and industrial applications of these methods. Secondly, this paper has summarized the models of calculating airflow resistance. Most of these empirical models are based on the characteristic parameters of fibrous materials, for instance bulk density, fiber diameter, porosity and thickness. Thirdly, this review has gathered the applications of airflow resistance in sound absorption and noise control. It is a crucial parameter in the prediction of both normal incidence sound absorption and reverberation chamber sound absorption. In conclusion, this review has concluded with some perspectives for the measurements, calculations and applications of airflow resistance.

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Experimental Studies of Fiber-Reinforced Concrete Prisms Exposed to High Temperatures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.864.3 ◽

2020 ◽

Vol 864 ◽

pp. 3-8

Author(s):

Svitlana Berestianskaya ◽

Evgeniy Galagurya ◽

Olena Opanasenko ◽

Anastasiia Berestianskaya ◽

Ihor Bychenok

Keyword(s):

Reinforced Concrete ◽

High Temperatures ◽

Experimental Studies ◽

Basalt Fiber ◽

Fiber Reinforced Concrete ◽

Building Structures ◽

Fibrous Materials ◽

Fiber Reinforced ◽

Safety Requirements ◽

Reinforcement Fiber

Fiber-reinforced concretes are varieties of composite materials. Such materials are commonly used nowadays. Concrete is fiber-reinforced using various fibrous materials, or fibers, which are evenly distributed over the volume of the concrete matrix and simultaneously provide its 3D reinforcement. Fiber-reinforced concrete has better stress-related strength characteristics than ordinary concrete. Since building structures must meet both the strength, rigidity and stability requirements, and the fire safety requirements, then for the extensive use of fiber-reinforced concrete structures, not only the external load design, but also temperature effect design should be conducted in the design phase. The strength and strain characteristics of fiber concrete exposed to high temperatures must be known for this purpose. In view of this, three series of prisms were manufactured and tested: the first series contained no fiber at all (control prisms), the second series contained basalt fiber, and the third series contained steel fiber. The test results showed that adding fibers improves the mechanical characteristics of fiber-reinforced concrete samples under specified conditions.

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Measurement of the bulk acoustic properties of fibrous materials at high temperatures

Applied Acoustics ◽

10.1016/j.apacoust.2013.09.016 ◽

2014 ◽

Vol 77 ◽

pp. 29-36 ◽

Cited By ~ 9

Author(s):

Paul T. Williams ◽

Ray Kirby ◽

Colin Malecki ◽

James Hill

Keyword(s):

High Temperatures ◽

Acoustic Properties ◽

Fibrous Materials

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Dynamic mechanical behaviour of three-dimensional random fibrous materials at high temperatures

Composite Structures ◽

10.1016/j.compstruct.2021.114593 ◽

2021 ◽

pp. 114593

Author(s):

Datao Li ◽

Jinsong Jiang ◽

Chao Zhang ◽

Wenshan Yu ◽

Pengmin Lu ◽

...

Keyword(s):

High Temperatures ◽

Mechanical Behaviour ◽

Three Dimensional ◽

Fibrous Materials ◽

Dynamic Mechanical

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In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087616 ◽

1991 ◽

Vol 49 ◽

pp. 660-661

Author(s):

Z. L. Wang ◽

J. Bentley

Keyword(s):

High Temperatures ◽

Image Resolution ◽

Atomic Processes ◽

Crystal Surfaces ◽

Beam Radiation ◽

Surface Areas ◽

Transmission Electron ◽

Reflection Electron Microscopy ◽

Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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