Length of fibres

Linear oligonucleotide probes have been immobilized along the length of fibres as well as on the distal end of fibres. Healey et al. [88] described the immobilization of three different oligonucleotide probes in acrylamide polymer matrices at the distal ends of optical fibres. Base pair mismatches could be distinguished on the same sensor after a 20-min hybridization with a detection limit of 0.2 nM [88]. More recently, zeptomole ( 600 molecule) detection limits have been obtained by using etched distal ends of optical fi-... 

An interesting modification of this technique is the fibre-optic dynamic anemometer (FODA)143. A length of fibre-optic cable carries the laser beam to the interior of the dispersion. Back-scattered light, with its Doppler frequency shift, is returned to the detector along with reflected light and, again, the resulting beat frequency pattern is analysed. Since only a very small volume around... 

Origin of cotton Length of fibre (in.) Diameter ( .) Limit for spinning... 

The intrinsic absorption properties of the fibre material at the wavelength, X, of the radiation. This is usually expressed in optical power loss, a, in dB/m, per unit length of fibre, L, which is related to the spectrophotometric absorbance of the material, A (Equation (3.21)), by the relation... 

The structure and properties of the fibre-matrix interface play a mayor role in the mechanical properties of composite materials too. The fibre can be used as reinforcement in composite materials since it is indicate that the length of fibre more length than critical length of the fibre. 

Figure 13.5 The variation of the length of fibre fracture with impulse for 2.2-, 4.2- and 6.2-mm-thick CF/PEI plates (laminates A to C, respectively) and a 4.5-mm-thick GF/PEI plate (laminate F) [24]. CF, carhon fibre GF, glass fibre PEI, polyether imide.

The unit frequently employed in the literature, g denier", is based on a 9000 m length of fibre in the same way. 

Length of fibre after mixing (mm) Percentage available in the mix after mixing ... 

Filament winding The application of a pre-impregnated continuous length of fibre around the outside of a mandrel to produce pipes, pressure vessels and similar articles, is also a form of contact moulding. As with pultrusion, continuous reinforcement is passed through a bath of activated thermosetting resin that is cross-linked by heat, in this case on the mandrel. 

When considering external attenuation affecting the transmission of light through optical fibres, one finds that, for short lengths of fibres, external attenuation normally is substantially larger than internal attenuation. At the entrance and exit face, both Fresnel reflection Lr and Fraunhofer diffraction Ld losses occur. 

Although continuous filament composites are of considerable commercial importance, their fabrication is a rather eomplex process and a cheaper though mechanically inferior product is obtained by mixing short lengths of fibre with a thermoplastic pol3aner. 

Consider a short length of fibre aligned with the tensile stress direction. The stiff fibre will tend to restrain the deformation of the matrix, and so a shear stress will be set up in the matrix at its interface with the fibre, which will be a maximum at the ends of the fibre and a minimum in the middle (Figure 8.3(a)). This shear stress then transmits a tensile stress to the fibre, but as the fibre-matrix bond ceases at the fibre ends there can be no load transmitted from the matrix at each fibre extremity. The tensile stress is thus zero at each end of the fibre and rises to an intermediate maximum or plateau over a critical length /q/2 (Figure 8.3(b)). For effective reinforcement the fibre length must be greater than the critical value /q, otherwise the stress will be less than the maximum possible. 

Serial connection The total length is the sum of the lengths of fibre and matrix I = It + Im- Since this condition holds even after deformation, we can also write Al = Alt + Aim- Using the definition of strain e = Al/l or Al = si separately for the three length changes, we find... 

Among jute, ramie, flax, hemp and cotton, jute has the shortest fibre length (0.5-6.0 mm) and ramie has the longest fibre length (125-126 mm). In the case of jute the average length of fibres from outer parts of the wedge is 0.3-2 mm and from the inner parts about 1-5 mm only (Table 2.13). 

The strength of the fibres must be, of course, effectively utilised by the spun yam. A yam can never have the same strength as its constituent fibres because of the fact that to withstand an applied load, the yam depends on the frictional contact between the overlapping lengths of fibres to transfer the load to all the fibres. The higher the twist the better the frictional contact and the stronger the yam, but for each fibre type there will be an optimum twist to obtain maximum yam strength [8]. 

---