Thermal stress in a polymer-coated optical glass fiber with a low-modulus coating at the ends
- PDF / 152,184 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 128 Views
A polymer-coated glass fiber with a low-modulus coating at the ends is considered. The objective of the analysis is to find out if there is sufficient incentive to use such a dual coating system for lower interfacial thermally induced stresses. These are due to the different coefficients of thermal expansion (contraction) of the dissimilar materials in the trimaterial structure. The study is restricted to the evaluation of the shearing stresses only and is based on a simplified strength-of-materials model, rather than on a rigorous theory-of-elasticity method. Such a approach seems to be justified, since the most accurate predictions of the magnitude and the distribution of the induced stresses are beyond the scope of this analysis. On the basis of the calculated data, we conclude that there is a definite incentive for employing a bimaterial coating system, in which “conventional” (high modulus) polymeric material is used in the midportion of the fiber, while a low-modulus material (typically, with a higher coefficient of expansion) is applied at its ends. Such a system could be recommended, when there is a need to bring down the interfacial stresses, and the possible increase in the manufacturing cost is not viewed as an obstacle.
I. INTRODUCTION 1–16
Polymer coatings are widely used in fiber optics for better short- and long-term reliability of the silica material, which is both brittle and moisture sensitive. Numerous structural analyses (stress–strain) related problems have been encountered and addressed during design, manufacturing, and testing of coated fibers. Examples of such problems are: evaluation of the effect of the coating on the bending stress in fibers; understanding the delamination mechanisms, and improving both the interfacial strength and strippability9,10; prediction of the stresses and curvatures occurring during the lowtemperature microbending or proof (pull-out) testing of coated fibers11–16; etc. In the analysis that follows, a polymer-coated fiber with a low modulus coating at the ends (Fig. 1) is considered. The objective of the analysis is to find out if there is sufficient incentive to use such a dual coating system for lower interfacial thermally induced stresses. These are due to the different coefficients of thermal expansion (contraction) of the dissimilar materials in the trimaterial structure in question. The study is restricted to
a)
Present address: Iolon, Inc., 1870 Lundy Ave., San Jose, CA 95131. email: [email protected]
2996
http://journals.cambridge.org
J. Mater. Res., Vol. 16, No. 10, Oct 2001 Downloaded: 16 Mar 2015
the evaluation of the shearing stresses only. In an approximate analysis, the shearing stress can be evaluated without considering its coupling with the peeling stress.17 The peeling stress, however, is strongly affected by the shearing stress and could be evaluated, if necessary, on the basis of the computed shearing stress. Therefore, if one is interested in understanding the effect of a certain structural or materials changing movement on the stress l
Data Loading...
