Fibers surface roughness

Figure 8.9 (a) Scanning electron micrograph of AS4 carbon fibers. The fiber diameter is Tixm (b) atom-force microscope picture showing the fiber surface roughness at an extremely fine scale (courtesy of R.K. Eby). 

The values of the surface free energy for the polymer matrix can be obtained from classical contact angle measurements. In the case of fibers, surface roughness and the presence of surface... 

Fractured surfaces exhibit a significant amount of fiber pull-out at room temperature and 1200°C, as shown in Figs. 4 and 5, respectively. This pull-out is indicative of a weak fiber-matrix interface. Debonding typically occurs at the BN/fiber interface (Fig. 4b). Hence, fiber surface roughness can play a significant role in determining the debonding characteristics of these composites. 

Natural fibers also act as nucleating agents and enhance the crystallization rate of polymer as reported for PP. The fiber surface roughness of the fiber and thermal stresses were found to facilitate the growth of transcrystallinity on cotton fibers, whereas bamboo fibers induced significant amount of beta form crystals and transcrystalline growth of maleated PP. 

Steel, copper, and brass fiber may have a variety of aspect ratios, shape, ie, straight versus curved fibers and cross-sectional geometry, surface roughness, and chemical compositions. Fibers having tight specifications in terms of cleanliness, chemical composition, and aspect ratio ate necessary. The fibers are usually machined from larger metallic forms. 

Mechanical adhesion. Mechanical interlocking between the two substrates can also contribute to adhesion. This mechanism would function most effectively with fibers with rough surfaces and irregular or non-circular cross-sectional shapes. 

Fig. 4.20. Schematic presentation of rough fiber surface in a fiber push-out test. After Maekin et al.

Ismail, l.M.K. Pfeifer, P. (1994) Fractal analysis and surface roughness of nonporous carbon fibers and carbon blacks. Langmuir 10 1532-1538... 

A hollow optical fiber (HOF) is a totally different type of optical fiber [42 16]. Figure 2.3A shows the structure of an HOF. An HOF is made of a glass tube with an inner coating of silver and a dielectric film, which enhances reflectivity. Matsuura et al. reported that the root mean square surface roughness of the silver film was 12 nm in their fabricated HOF [44]. 

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