Page 22 - Fiber Fracture

FIBER FRACTURE: AN OVERVIEW 7

Fig. 2. An example of kinking under compression in a high-performance polymeric fiber derived from
rigid-rod liquid crystal (courtesy of Kozey and Kumar). High-strength organic fibers fail in compression at
strains < 1%. Microbuckling or shear banding is responsible for easy failure in compression.

Band of buckled
chaindfibnls

misorientation

(2) (b)
Fig. 3. Two compressive failure models: (a) elastic microbuckling of polymeric chains; this model involves
cooperative in-phase buckling of closely spaced chains in a small region of fiber; (b) misorientation; this
model is based on structural imperfections or misorientations that are invariably present in a fiber.

misorientation in a unidirectional composite lead to kink formation under compressive
loading (Argon, 1972). The model shown in Fig. 3b is based upon the presence of
such a local misorientation in the fiber leading to kink formation under compression.
Failure in compression is commonly associated with the formation and propagation of
kinks. These kink bands generally start near the fiber surface and then grow to the
center of the fiber. It has also been attributed to the ease of microbuckling in such