Structure–property relationships of aramid fibers via X-ray scattering and atomic force microscopy

Real-space methods of characterizing high-performance fibers’ inherent morphologies will greatly enhance our understanding of the key structural features within fibers and their impacts on mechanical performance. Here, we report on structure–property correlations of two new classes of commercial DuPont Kevlar fibers, termed “K29 sample test” and “K49 sample test,” as well as conventional K29 and K49 fibers.^* Through multifrequency atomic force microscope scans of internal fiber surfaces prepared by a focused ion beam notch technique, we directly capture nano- and microstructural features that define the inherent structures of these fibers. Integrating these findings with X-ray scattering experiments, we relate crystallographic and real-space measurements to each other, highlighting how multiscale structural motifs manifest within fibers. By carrying out tensile tests on single fibers drawn from the same tows, we also glean new insights into the structure–property relationships that dictate the mechanical behavior of these fibers.