Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Nanostructural Evidence of Mechanical Aging and Performance Loss in Ballistic Fibers



John Howarter, Ming Liu, Walter G. McDonough, Christopher Soles, Gale A. Holmes


It is understood that the ballistic resistance of aromatic polyamide fibers is related to the fiber's ultimate tensile strength, strain-to-failure, and Young's modulus. Ideal high-performance ballistic materials maximize these properties while minimizing material density. Equally important is long-term mechanical and chemical stability: the fibers should not exhibit performance loss over their lifetime. However, less is known quantitatively about their modes of degradation and experimental methods to quantify the aging and degradation in these fibers are critical. Multiple variations of next generation high-performance fibers have been investigated under chemical and mechanical accelerated aging conditions. Performance losses have been empirically correlated to chemical degradation of the polymer chain and nanostructural changes in the fiber morphology through X-ray photoelectron spectroscopy (XPS). Here we introduce positron annihilation lifetime spectroscopy (PALS) measurements as a sensitive method to quantify the early onset of damage in the flexed fibers as quantified through changes in the nanoscale void structure in the material.
Journal of Polymer Science Part B-Polymer Physics


positron annihilation lifetime spectroscopy, ballistic fibers, polymers


Howarter, J. , Liu, M. , McDonough, W. , Soles, C. and Holmes, G. (2017), Nanostructural Evidence of Mechanical Aging and Performance Loss in Ballistic Fibers, Journal of Polymer Science Part B-Polymer Physics, [online],, (Accessed June 24, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created September 29, 2017, Updated December 16, 2021