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Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

ABSTRACT

The transverse and longitudinal mechanical properties of aramid fibers like Kevlar™ 29 (K29) fibers are strongly linked to their highly oriented structure. Mechanical characterization at the single fiber scale is challenging especially when the diameter is as small as 15 µm. Longitudinal tensile tests on single K29 fibers and single fiber transverse compression test (SFTCT) have been developed. Our approach consists of coupling morphological observations and mechanical experiments with SFTCT analysis by comparing analytical solutions and finite element modeling. New insights on the analysis of the transverse direction response are highlighted. Systematic loading/unloading compression tests enable to experimentally determine a transverse elastic limit. Taking account of the strong anisotropy of the fiber, the transverse mechanical response sheds light on a skin/core architecture. More importantly, results suggest that the skin of the fiber, typically representing a shell of one micrometer in thickness, has a transverse apparent modulus of 0.2 GPa. That is around more than fifteen times lower than the transverse modulus of 3.0 GPa in the core. By comparison, the measured longitudinal modulus is about 84 GPa. The stress distribution in the fiber is explored and the critical areas for damage initiation are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015

Aramid fibers possess remarkable mechanical properties suitable for many demanding applications. Mechanical characterization at the single fiber scale is challenging especially when the fiber diameter is as small as 15 µm. Longitudinal tensile tests on single aramid fibers and single fiber transverse compression test (SFTCT) have been developed and coupled with morphological observations and numerical analysis. Results suggest a skin/core structure with an apparent transverse modulus within the skin regions around 0.2 GPa, more than 15 times lower than the transverse modulus in the core.

Authors:   Judith Wollbrett‐Blitz, Sébastien Joannès, Rémi Bruant, Christophe Le Clerc, Marc Romero De La Osa, Anthony Bunsell, Alba Marcellan
Journal:   Journal of Polymer Science Part B: Polymer Physics
Year:   2015
Pages:   n/a
DOI:   10.1002/polb.23763
Publication date:   12-Jun-2015
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