Page 12 - Fiber Fracture

PREFACE ix

The last section is devoted to fracture of nanotubes. Carbon nanotubes have been
theoretically predicted to be among the strongest fibers. Their strength, which has
already been verified experimentally, may enable unique applications in many critical
areas of technology. J. Bernholc and collaborators review the mechanical behaviour of
carbon nanotubes and the role of bending in changing the electrical properties.

DEFECTS AND MICROSTRUCTURE

Two topics appear in most of the chapters of this book: The role of defects in fiber
fracture and the large difference of length scales in fiber-microstructure. Both features
are interwoven and deserve some comments.
Fracture is defect sensitive - contrary to elastic modulus or density - and models
of fiber fracture should take into account - and model - such imperfections. Most
of our understanding of fiber failure that appears in the chapters is borrowed from bulk
concepts - such as the models based on solid state physics - and when Fracture
Mechanics is used only idealized defects are considered. Information of the type and
shape of actual fiber defects is essential for understanding and modelling fiber fracture,
and such information is still scarce.

DIFFERENT LENGTH SCALES
__--
_- --------__ ..

0 50 100 km