Page 18 - Fiber Fracture

Fiber Fracture
M. Elices and J. Llorca (Editors)
D 2002 Elsevier Science Ltd. All rights reserved

FIBER FRACTURE: AN OVERVIEW

K.K. Chawla

Department of Materials and Mechanical Engineering, Universiry of Alabama at Birmingham, BEC 254.
I530 3ni Avenue S., Birmingham, AL 35294-4461, USA

Introduction.. ................................... 5
Polymeric Fibers .................................. 5
Environmental Effects on Polymeric Fibers .................. 8
Carbon Fibers .................................... 9
Metallic Fibers ................................... I3
Glass and Ceramic Fibers .............................. 17
Conclusions ..................................... 24
References. ..................................... 24

Abstract

Fracture of fibers during processing or in service is generally an undesirable feature.
Fracture in fibers, as in bulk materials, initiates at some flaw(s), internal or on the
surface. In general, because of the high surface to volume ratio of fibers, the incidence
of a surface flaw leading to fracture is greater in fibers than in bulk materials. Very
frequently, a near-surface flaw such as a microvoid or an inclusion is responsible for
the initiation of fracture of fiber. In polymeric fibers, the fundamental processes leading
to failure are chain scission and/or chain sliding or a combination thereof. Service
environment can be a major determining factor in the failure process of fibers. A
striking example of this was in the failure of aramid fiber used in the tether rope in
space. Metallic fibers represent a relatively mature technology. The surface condition
and segregation of inclusions are the two factors that limit the strength of metallic
filaments. Ceramic and silica-based fibers (including optical glass fiber) also have the
same crack-initiating flaws as in polymeric and metallic fibers. One major problem in
glass fibers is that of failure due to static fatigue. In this paper, examples of fracture in
different types of fibers are provided. Some of the possible ways to prevent catastrophic