Fibers elastic properties

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

Nonoxide fibers, such as carbides, nitrides, and carbons, are produced by high temperature chemical processes that often result in fiber lengths shorter than those of oxide fibers. Mechanical properties such as high elastic modulus and tensile strength of these materials make them excellent as reinforcements for plastics, glass, metals, and ceramics. Because these products oxidize at high temperatures, they are primarily suited for use in vacuum or inert atmospheres, but may also be used for relatively short exposures in oxidizing atmospheres above 1000°C. 

Elastic Properties. The abiUty of a fiber to deform under below-mpture loads and to return to its original configuration or dimension upon load removal is an important performance criterion. Permanent deformation may be as detrimental as actual breakage, rendering a product inadequate for further use. Thus, the repeated stress or strain characteristics are of significance in predicting or evaluating functional properties. 

J. M. Whitney and M. B. Riley, Elastic Properties of Fiber Reinforced Composite Materials, AIAA Journal, September 1966, pp. 1537-1542. 

J. J. Hermans, The Elastic Properties of Fiber Reinforced Materials when the Fibers are Aligned, Proceedings of the Koninklijke Nedertandse Akademie van Weten-schappen, Amsterdam, Series B, Volume 70, Number 1, 1967, pp. 1-9. 

P-plastomers provide a unique combination of ease of processing, such that conventional thermoplastic-processing routines and arid equipment can be adapted to this polymer as weU as for a final fabricated product that is elastic. This combination of properties leads to the easy fabrication of elastic materials such as fibers and films, which traditionally have only been made inelastic by the use of thermoplastics. This advance opens the pathway to the introduction of desirable elastic properties to a host of fabrication processes very different from either the conventional rubber-processing equipment or the conventional rubber products, such as tires. P-plastomers and their fabricated products are not only soft, but also elastic. 

Beyond pure geometry, the two-angle model is also useful to predict some of the physical properties of the 30-nm fiber, for instance, its response to elastic stress [17]. In an independent study on the two-angle model by Ben-Haim et al. [76] this question has been the major focus, and as demonstrated by Schiessel [72], the elastic properties of the two-angle model as a function of 6 and are analytically solved completely by combining the results from both papers. 

The coefficients Aj and. 44 are complex functions of the elastic properties and geometric factors of the constituents and are given in Appendix D. The solution for Eq. (4.118) is subjected to the following boundary conditions assuming an unbonded cross-section of the embedded fiber end... 

Bianchi et al. (19) spun fibers from isotropic and anisotropic solutions of cellulose (D.P. 290) in LiCl (7.8%)-DMAC solutions. The fiber mechanical properties increased throimh the isotropic-anisotropic transition with elastic moduli as high as 22 GPa (161 g/d) being obtained. 

The Halpin-Tsai equations represent a semiempirical approach to the problem of the significant separation between the upper and lower bounds of elastic properties observed when the fiber and matrix elastic constants differ significantly. The equations employ the rule-of-mixture approximations for axial elastic modulus and Poisson s ratio [Equations. (5.119) and (5.120), respectively]. The expressions for the transverse elastic modulus, Et, and the axial and transverse shear moduli, Ga and Gf, are assumed to be of the general form... 

The crystallization tendency of polycarbonates in the pure state is limited. Kampf (JO) found that the first spherulites appear only after heating at 180°C. for eight days more pronounced crystallization occurs only after heating at 190°C. for the same period of time. Orientation of films or fibers does not cause any crystallization, and relatively small improvement of elastic properties is noted. 

---