Limiting role of crystalline domain orientation on the modulus and strength of aramid fibers

Korhan Şahin, Jan Kenneth Clawson, James Singletary, Suzanne Horner, James Zheng, Assimina Pelegri, Ioannis Chasiotis

Research output: Contribution to journalArticlepeer-review

Abstract

The evolution of crystalline domain orientation vs. mechanical properties of aramid fibers under mechanical loading was investigated for initial crystalline domain orientations between 16.7° and 9.7°. The latter resulted in a broad range of longitudinal moduli between 66 GPa and 119 GPa but tensile strengths in the narrow range of 3.5–4.0 GPa. Mechanical conditioning up to 90% of the fiber tensile strength increased the initial modulus converging to 100 GPa which corresponds to a stable crystalline domain orientation of 11.6°, while the unloading modulus at stresses near the tensile strength converged to ∼165 GPa which approaches the theoretical modulus of 220 GPa. On the contrary, the tensile strength remained unchanged with increasing crystalline domain orientation, and was shown to be independent of the fiber gauge length, thus implying that failure is not due to flaws obeying weakest link statistics. Instead, short gauge length tests (200 μm) showed failure initiation at the fiber skin followed by crack propagation at the skin-core interface, resulting in extrusion of the fiber core, which points to the skin-core interface as an important factor limiting the tensile strength of this class of fibers.

Original languageEnglish (US)
Pages (from-to)96-106
Number of pages11
JournalPolymer
Volume140
DOIs
StatePublished - Mar 28 2018

Keywords

  • Fiber skin and core
  • High performance fibers
  • Size effects

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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