14—the Dynamic Bulk Modulus of Fibre Masses

The viscoelastic properties of nylon 6 fibers are studied in terms of stress relaxation and dynamic mechanical analysis. Single fibers are subjected to tensile stress relaxation tests at room temperature in air and water after rapid straining to between 5 and 40%; the duration of these tests is between 0.1 to 105 seconds. Dynamic mechanical tests are done on a Rheometrics dynamic tester at frequencies between 0.1 to 10 Hz and at various static prestrains. Results are compared with those from similar tests in compression on waddings made of corresponding fibers. In general, correlations are good between fiber properties and wadding properties.

mentioning

confidence: 70%

Viscoelastic Properties of Nylon 6 Fibers and Corresponding Fiber Assemblies

Seldén

Dartman

1998

“…In the intervening 40 years from its derivation to the present, this relationship has been examined both experimentally and theoretically in detail [4,7,8]. Despite deficiencies, Van Wyk's original model has not been superceded.…”

Section: Theorymentioning

confidence: 96%

“…He considered that compression of a mass of fibers increases the number of points of contact between fibers and bends individual fibers between the points of contact. He showed theoretically that the constant a in Equation 1 is independent of fiber diameter, but is dependent on the Young's modulus Y of the fibers, the mass W of fibers in the sample, and the density p of the fibers: K is a dimensionless constant with a typical value of 0.01 [8,22]. The value of K changes with fiber orientation and crimp [22].…”

Section: Theorymentioning

confidence: 97%

“…The value of the parameter a for a fabric may be used in Equation 2 to calculate the mass of fibers in its surface layers. Since Young's modulus for wool at 65% RH is 4 X 101 gf/CM2 and the density of wool is 1.3 g/CM3, and if the value of K in Equation 2 is taken as 0.01 [8,20,22] and using the average value of a in table I, then the mass W of fibers per unit area in the two surface layers is 13000 (2.6 X 10-5/4 X 105)1/3 = 5.2 g/M2 or 5.2/244 = 0.02 of the total fabric mass per unit area. These calculations correspond roughly to what is observed by measuring the However, the energy E contains the fiber orientation factor K, which is altered by pressing.…”

Section: Analysis Of Loading-compression Curvesmentioning

confidence: 99%

See 1 more Smart Citation

A Mechanical Model for the Lateral Compression of Woven Fabrics

Jong

Snaith

Michie

1986

A mechanical model for the lateral compression of woven fabrics is derived from Van Wyk's compression law for fiber assemblies. The pressure ( P ) and thickness (v) relationship is P = a/ ( v -v')3. The parameter v' refers to the core of the fabric, which is incompressible over the pressure range 2-5000 gf/cm 2 . The parameter a refers to the compressible surface layers and is dependent on the mass of fibers in the surface layers and their orientation.A comparison is made of the results obtained with the KES-F fabric compression tester and the standard fabric thickness tester. The energy of compression is proportional to the cube root of the parameter a. The compressibility of the fabric is proportional to the energy of compression per unit volume of fabric. The changes that occur in the fabric surface layers during a typical fabric finishing process are investigated.The measurement of the lateral or thickness compression properties of fabrics forms an integral part of objective measurements currently being considered internationally for wool fabrics [ 12,17]. These objective measurements are intended to help maintain consistent quality in finished wool fabrics and to aid in product engineering of wool fabrics. An early paper [2] described the thickness-compression curve of fabrics. The effects of finishing treatments on the lateral compression curves of fabrics have been described [3,9,13], but the thickness-compression curves of fabrics have not been analyzed mechanically. An analysis of the mechanics of fabric compression may help in developing compression test methods and interpreting results. In this paper, we present a mechanical model that describes the compression curves measured on a large number of woven fabrics over the pressure range of 2-5000 gf/cm2. The model reduces the fabric to three layers -a relatively incompressible core layer in contact with a much more compressible surface layer on either side. The model is reconciled with both electron microscope evidence and optical measurements made on the fabrics.The model indicates that the DIN standard [6] for measuring fabric compression is very simply related to the compression test performed on the Kawabata evaluation system for fabrics . The change in the compression properties of wool fabrics in some commercial worsted fabric finishing processes is presented and interpreted in terms of the model.

“…Although the inverse-cube curve of pressure versus volume is roughly followed curing the compression of a fiber mass, it is also true that most compression curves show substantial deviations from that relationship. In this respect, Dunlop [5,6,7,8] states, &dquo;Of more serious concern is the magnitude of the constant K, which was introduced by Van Wyk to account for variations in fiber characteristics, spacing and orientation of fiber contacts, and other factors. Van Wyk found K to be some two orders of magnitude less than the expected value of unity, and this has been a recurring feature of fiber-mass compression work&dquo; [5].…”

mentioning

confidence: 99%

Physical Analysis of the Compression of Filament Assemblies

Virto

Carbonell

Naik

2002

This paper presents experimental results on filament assembly compression showing the influence of porosity on the compacting pressure necessary for attaining the desired packing density. At the same time, a physical description of the compacting phenomenon is given. On the basis of these observations, a theoretical approach is developed to explain the volume decrease of a mass of filaments under compression.