Crimp extension

Both fit easily between ceiling joists and include 4 of tubing -2 and 4 (bead crimp) extensions available. 13" kit can extend to 20 for two story applications ... 

Crimp extension refers to the extent to which the graft or biotextile stmcture stretches under longitudinal tension. A spedmen of known relaxed length is extended on a mechanical tester, such as an Instron Universal Tester, so as to remove most of the crimps by applying a standard constant load of 1.2 N. The amount of crimp extension is calculated from the difference between... 

Conventional, low-speed spun fibers must be further finished by drawing, although POY yarns are typically draw texturized. The drawing process adds strength by orientation of the molecular structures. Normal extensibility and proper tenacity are added by drawing the spun fibers to several times their as-spun length. The texturing process produces permanent crimp, loops, coils, or crinkles in the yarn that result in properties of stretch, bulk, absorbency, and improved hand (32). There are three basic types of... 

Adhesive tapes are also extensively employed for protection of pipes with curvilinear and corrugated surfaces used in chemical industry, gas and oil held developments. The problem of lining convoluted pipes is solved [116] by rolling the tube over a roller base wrapped in a poljuner tape (Fig. 3.45a). Roller axes are arranged at a pitch equal to the distance between crimps of the pipe. For this purpose, pinch mechanisms can also be used [117] made as a sprocket and having a roller on each beam (Fig. 3.45 ). 

The tensile strain recovery and the work recovery % are also calculated. The procedure for crimped specimens is much the same, except that the test specimen is first pretensioned to take out the crimp and the extension shown on the recording chart eliminated by rezeroing the recorder. The location of the cross-head is locked in the memory at this point, so that on recovery the cross-head does not reenter the crimp range. 

When a wool fiber is extended in water, the load-extension curve (Figure 5.12) shows the following features For a small extension, up to about 1%, the gradient of the curve increases as the crimp of the fiber is straightened. The gradient is then constant up to about 3% extension. Thus the extension of the fiber is approximately proportional to the load. Hooke s law is approximated this is the so-called Hookean region of the load-extension curve. 

The crimp statistics have been studied in detail at the Institute for Fibers and Forest Products Research in Jerusalem, and much information has been brought together by, for example, Lewin et al. [56]. Two parameters are measured to define the crimp, namely the RMS value of the width (Z>) and the number of crimps per unit length of the stretched fiber (n). As the crimp is three dimensional, the fiber is rotated during the measurements. Typical values for jute fibers immersed in 12.5% NaOH, for 1 h at a temperature of 2°C are reported to be about 1.6 mm for D, with a standard deviation of 0.55 mm, and about 0.098 mm for n, with a standard deviation of 0.035 mm The extension of the fibers at break was 15% relative to the initial length of the crimped fiber under a load of 10 mg, and the crimp disappeared for loads of about 2000 mg. The energy required to uncrimp the fiber was equivalent to about 3.9 g per 1% of extension. 

Textile materials can be produced by a whole series of processes, for example, by weaving, knitting, or by fleece formation. Knitted fabrics have stronger elasticity than weaves and this was first used in the manufacture of wool jerseys and later found extensive application in what are known as double knits from polyester yarns. Fibers and filaments can also be made more elastic by a whole series of mechanical procedures such as, for example, crimping or giving a false twist to the yarn. 

When a tensile load is applied to a fabric seam, it has to overcome two types of frictional forces. One is the inter-yam frictional forces within a fabric, and the other is the frictional force of the stitch assembly. The former is dependent upon the crimp, yam diameter, fiber content, and number of cross-over points. The latter, however, is dependent upon the fabric properties like fiber content, type of yam (spun or filament), thickness, lateral compression, cover factor (threads per cm), bending, shear, tensile and surface roughness, and coefficient of friction. It is also dependent upon the properties of the sewing thread like fiber content, diameter, coefficiait of Mction, initial modulus, and extensibility. All of these properties, together with the machine variables like needle and bobbin thread tension and the stitch length, make up the frictional force of the stitch assembly. Thus different combinations of these would be expected to provide different frictional resistance and hence different loads at which seam slippage may take place. 

Though woven fabric was the lifeblood of almost all aerospace structures until the 1930s, since then its use has fallen dramatically, replaced by sheet metal. Now that has been replaced by straight fiber (tow) lay-up into load-bearing patterns. The only woven carbon fiber fabric used extensively today is in the impact or penetration protection system applied to the outside of virtually all laid-up panels and by virtue of its crimped woven form, nonload bearing. This fabric sometimes contains metal threads to assist in lightning conduction as well as other electrical shielding functions. 

This is an extension of the open width processing principles in combination with causticisation. The fabric construction should be devised so that there is space to allow yam crimp to develop. Causticisation will cause the crimp development and impart a memory which together with the fibre s high modulus and resilience will allow stretch with high degrees of recovery, equal to that achievable with elastane containing fabrics. It should be borne in mind though, that this is a comfort stretch rather than the power stretch associated with elastomerics. 

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