Acoustic properties test methods

This article covers the use of acoustics as a molecular probe of polymer structure and describes various acoustic applications of polymers. Enough theory and experimental details are given to make the presentation understandable, but the emphasis is on the experimental results for polymers. Most of the presentation is for small-amplitude waves in solid polymers. References to some speciaUzed topics are given (see also Mechanical properties Test Methods). 

There are no test methods specific to rubber for acoustic properties and procedures for materials in general would be applied. A section on optical... 

Fatliquor affects mostly the mechanical properties, measured also by a collection of ASTM methods given in (25). In addition, the sounds emitted by leather when it is deformed are greatly suppressed by the presence of fat, supporting a method of assay by means of the acoustic emission test (27). 

This chapter first provides an introduction to the acoustic properties of textiles, which include propagation, absorption, and scattering of sound. The properties can be characterized by various parameters such as flow resistance, transmission loss, absorption coefficient, and scattering coefficient. Test and evaluation methods for obtaining these parameters are discussed. Based on the acoustic properties of the textiles, acoustics designers can make use of textiles in buildings and office environments to optimize sound quaUty depending on particular requirements. 

Sometimes, it is necessary to characterize the sound insulation characteristics of materials using a less expensive and less time consuming approach than the reverberant room method, or to have small samples tested when larger samples are impossible to construct or to transport to a laboratory. In these cases, the transfer matrix method can be used to measure the normal incidence sound transmission of the materials or samples. The transfer matrix can be used to determine additional acoustic properties of the material and to allow calculation of acoustic properties of built-up or composite materials by the combination of their individual transfer matrices (ASTM E2611-09,2009). 

The sound-absorbing properties of acoustical materials also are influenced by the manner in which the materials are mounted. Standard mounting methods for use in laboratory testing are specified in ASTM E795-92 (2). Unless noted otherwise, pubflshed data for acoustic ceiling materials are for Mounting Type E-400, for which the material being tested is suspended 400 mm below a hard surface. 

Equation (20) was also used to compute the acoustic response of fluid cylinders immersed in water and insonified normal to their axis with a sinusoidal wavepacket. The examples shown here can be considered by other techniques ( 5 ) but serve as appropriate tests for the accuracy of the model which can then be used to compute the acoustic responses of systems which cannot be readily treated by other methods. The material properties of the cylinder are shown in Table 1 and were chosen to enable the calculated echo structure of the cylinders to be compared with previously published analytical work ( 5 ). ... 

The uncertainty related to the thermal expansion coefficient makes latex systems the most complicated systems for acoustics. This is important to keep in mind for testing a particular model of an acoustic instrument. Latex dispersions that are used as standards for light-based methods should be used with caution as in many cases the thermal-expansion properties of these standards are not well known. 

Very recently, in our group, enhanced self-reinforced PP composites based on commercial PP fabrics were obtained by the film stacking method followed by compression molding introducing different contents of micron-sized quartz particles in the matrix films (unpublished results). Simultaneous improvements of composite tensile strength, ductility and fracture toughness were observed from the addition of quartz to the polymer matrix (Table 14.1). Enhanced degree of consohdation was obtained for the composites with quartz as evidenced from the improved mechanical properties and by SEM observations. This was also confirmed by acoustic emission analysis in situ in tensile tests. 

Treny and Duperray [32] have pointed out that issues of human comfort relating to noise and vibration are one of the major priorities for materials structural research and development in the field of transportation. Dynamic mechanical analysis (DMA) testing provides a way to characterise in an accurate manner the viscoelastic properties of all the material used in vehicle interiors. Using a unique database software allowed easy material selection according to their viscoelastic properties. An approach for the optimisation of materials through the combination of selective database software and specific numerical calculation methods, to predict the final acoustic behaviour during the materials selection and systems development period are presented. 

However, it appears that none of the non-destructive tests currently employed directly correlate with any critical failure property. Most industrial test techniques such as through-transmission and pulse-echo ultrasonics, sonic vibration techniques. X-ray radiography, thermal inspection methods, holography, liquid penetrants, etc. basically attempt to find defects in the joint. Such defects may arise from several sources. Some defects arise from porosity, cracks or voids in the adhesive layer or at the interface and are typically filled with air they will simply be referred to as voids in the present discussions. However, during the service life of the joint such voids may fill with water which makes them far more difficult to detect since, for example, water has a much higher acoustic, impedance than air. Also, zero-volume voids, or debonds, may occur when the adhesive and substrate are in contact but no... 

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