Models of fibre fracture

Abstract

This chapter presents two different approaches to modeling fiber fracture: the atomistic approach, for those who use the tools of quantum mechanics, and the continuum approach, which relies on continuum mechanics. In the continuum approach, the simplest models are based on linear elastic fracture mechanics (LEFM)—a well-developed discipline that requires a linear elastic behavior and brittle fracture—not always exhibited by fibers. High-performance fibers usually have diameters ranging from 10 μm to 150 μm and are amenable to be modeled using a continuum approach. Modeling fiber ductile fracture is an involved problem, even for homogeneous and macro-defect-free fibers. Under tensile loading, fibers eventually reach an instability point, where strain hardening cannot keep pace with the loss in cross-sectional area, and a necked region forms beyond the maximum load. Fracture of highly oriented polymer fibers during tensile loading may exhibit different forms: brittle fracture, usually due to transverse crack propagation; ductile fracture, as a consequence of plastic flow after necking; or fibrous axial splitting, where cracking or splitting occurs along planes close to the fiber axis.