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Damage sensing using a mechanophore crosslinked epoxy resin in single-fiber composites

Published

Author(s)

Jeremiah W. Woodcock, Richard J. Sheridan, Ryan Beams, Stephan J. Stranick, William F. Mitchell, Jeffrey W. Gilman, Gale A. Holmes, Catherine L. Brinson, Vamshi Gudapati, hartman David, Amol Vaidya

Abstract

Natural and man-made composite materials must be tough, durable and damage tolerant1,2. For man-made composites to rival, or exceed, the dynamic, multifunctional performance of natural materials new information about the fundamental mechanisms responsible for damage must be revealed3,4. Here, we report a new method to directly visualize damage in composites. This is demonstrated in a model composite, comprised of a mechanophore functionalized epoxy resin with an single embedded glass fiber. Fluorescence lifetime imaging microscopy (FLIM) of single fiber fragmentation test (SFFT) samples reveals extensive damage zones in the epoxy in three dimensions at optical resolution about two fiber-diameters away from the fiber-matrix interface and remote from the fracture site. Evidence of damage comes from both the onset of fluorescence, via mechanical activation of the probe, and the reduced fluorescence lifetime of the activated spirolactam-based mechanophore. Previous theoretical treatments proposed that this damage should occur due to shock waves from the fiber fracture events, but until now no direct evidence of the damage has been reported. This information provides valuable new insights into the fatigue and failure mechanisms of glass fiber reinforced composites. Furthermore, although the SFFT is considered the premier method for determining the interfacial shear strength (IFSS) between a fiber and matrix polymer, these results suggest that this test may be better viewed as an IFSS measure of a damaged interface instead of an intact interface. These results give new insights into the damage mechanisms of glass fiber reinforced composites (GFRCs) and promise to do the same for many other composite materials.
Citation
Composites Science and Technology

Keywords

composites, mechanophore, fiber, fragmentation, interface, interphase

Citation

Woodcock, J. , Sheridan, R. , Beams, R. , Stranick, S. , Mitchell, W. , Gilman, J. , Holmes, G. , Brinson, C. , Gudapati, V. , David, H. and Vaidya, A. (2020), Damage sensing using a mechanophore crosslinked epoxy resin in single-fiber composites, Composites Science and Technology, [online], https://doi.org/10.1016/j.compscitech.2020.108074 (Accessed April 18, 2024)
Created May 25, 2020, Updated September 29, 2020