Page 282 - Fiber Fracture

Fiber Fracture
M. Elices and J. Llorca (Editors)
0 2002 Published by Elsevier Science Ltd. All rights reserved

FRACTURE OF HIGHLY ORIENTED,

CHAIN-EXTENDED POLYMER FIBRES

J.W.S. Hearle

The Old vicamge, Mellol; Stockport SK6 5LX, UK

Introduction ..................................... 267
Fibre types ................................... 267
Structure, Modulus and Strength ........................ 269
Experimental Observations ............................. 272
Tensile Failures ................................. 272
Creep Rupture ................................. 273
Tensile Fatigue ................................. 275
Surface Abrasion ................................ 276
Axial Compression, Bending and Flex Fatigue ................ 276
Theoretical Approaches ............................... 277
Failure in Shear ................................. 277
Time and Temperature ............................. 279
Axial Compression Fatigue .......................... 28 1
References. ..................................... 285

Abstract
Polymeric high-modulus, high-tenacity fibres have a structure consisting of highly
oriented, chain-extended, linear macromolecules. Para-aramid, aromatic copolyester,
PBO and PIPD fibres are made by liquid-crystal routes, but HMPE is gel-spun.
Deviations from an ideal structure reduce stresses below the ideal values. Tensile failure
is due to axial splitting. HMPE fails by creep rupture under moderate loads. These
fibres suffer from surface abrasion, flex fatigue and axial compression fatigue. Failure
in shear is described qualitatively. Time and temperature dependence has been modelled
by statistical mechanics. In fibre assemblies, axial compression fatigue is modelled in
terms of axial and transverse compressive forces on yarns and axial slip. The same