Tenacity at break

ASTM D 2256- 95 provides a method for the determination of the tensile properties of monofilament, multifilament, and spun yarns, wither single, plied, or cabled, providing that the yarns do not extend more than 5% when the tensile force is increa.scd from 5 mN tex to 10 mN tex. The method covers the measurement of breaking force and elongation at break, tenacity (at break), initial modulus, and breaking toughness. Options arc included for knotted and looped forms (for which sec also ISO 2062). 

Point II is the maximum of the force/deformation curve and is called the yield stress The drawing stress is at point III. Finally, the tenacity at break or the tensile strength and the elongation at break occur at the point IV. The region between the points la, II, and III is what is known as the ductile region. The decrease in tensile stress with increasing strain between... 

Tenacity-at-break, FB the tension at which the fiber breaks. Often given relative to linear density. 

The most important characteristics are, similar to fiber and yarn testing, maximum strain, elongation at maximum strain, tenacity at break, and elongation at break. The standards DIN 53 858 and DIN 53 859 cover the most important testing procedures. 

Figure 14.15 Prediction of tenacity-at-break from the machine settings...

Figure 1.2 Typical values for tenacity-at-break and elongation-at-break for fibers...

The elasticity of a fiber describes its abiUty to return to original dimensions upon release of a deforming stress, and is quantitatively described by the stress or tenacity at the yield point. The final fiber quaUty factor is its toughness, which describes its abiUty to absorb work. Toughness may be quantitatively designated by the work required to mpture the fiber, which may be evaluated from the area under the total stress-strain curve. The usual textile unit for this property is mass pet unit linear density. The toughness index, defined as one-half the product of the stress and strain at break also in units of mass pet unit linear density, is frequentiy used as an approximation of the work required to mpture a fiber. The stress-strain curves of some typical textile fibers ate shown in Figure 5. 

Fiber Tenacity, N /tex Initial modulus, N/tex Elongation at break, %... 

Definitions of the commonly measured tensile properties are as follows Unear density (tex) is the weight in grams of 1000 m of yam. Tenacity is the tensile stress at break and is expressed in force-per-unit linear density of unstrained specimen, N /tex. Knot tenacity is the tensile stress required to mpture a single strand of yam with an overhand knot tied in the segment of sample between the testing clamps. It is expressed as force-per-unit linear density and is an approximate measure of the britdeness of the yam. Toop tenacity is the tensile stress required to mpture yam when one strand of yam is looped through... 

Standard Test Methods for Tire Yarns, Cords, and Woven Fabrics. ASTM standard D885M-94 includes test methods for characterizing tire cord twist, break strength, elongation at break, modulus, tenacity, work-to-break, toughness, stiffness, growth, and dip pickup for industrial filament yams made from organic base fibers, cords twisted from such yams, and fabrics woven from these cords that are produced specifically for use in the manufacture of pneumatic tires. These test methods apply to nylon, polyester, rayon, and aramid yams, tire cords, and woven fabrics. 

Ref. Polymer structure Molar ratio Tenacity g dtex 1 Initial modulus g dtex Extension at break %... 

Stiffness or tensile modulus at break was determined from the value of tenacity and elongation at break using the following relation ... 

Sample Grafting % Elongation at break (B.L.) (%) Tenacity (gms/denier) Tensile modulas at break (Stiffness)... 

A very important diagram for fibres and yams is the stress—strain diagram, where the specific stress is plotted as a function of the elongation (extensional strain) in %. The curve starts at an elongation of zero and ends in the breaking point at the ultimate specific stress (=tensile strength or tenacity) and the ultimate elongation (=strain at break). 

FIG. 13.87 Diagram of the specific tenacity (specific dynamic tensile modulus (Ea/p), for modern high-performance filaments. The diagonal lines have the indicated ratio, which is the theoretical elongation at break (fractional) high-performance yarns have refractory materials have values between 0.025 and 0.005. (ty = tire yarn). 

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