Impact Tension Damage Mechanism Analyses of Co-Woven-Knitted Composite from Hilbert–Huang Transform

Abstract

The impact tensile behaviors of co-woven-knitted (CWK) composites were tested with split Hopkinson tension bar apparatus along 0°, 45°, and 90° directions under the strain rates from 1589 to 2586 s⁻¹ and compared with that in quasi-static strain rate of 0.001 s⁻¹. The impact tension damage mechanisms were analyzed in frequency domain with the Hibert–Huang transform (HHT) method. Specifically, the stress time histories curves of the CWK composite were transformed to find the frequency distributions for the different tension failure modes. It was found that thefailure mode of fiber breakages, fiber pull-out, resin cracks, and resin shear failurewere located at a specific frequency band. And also, the different failure modes under high strain rate loading are all located at the high frequency range. With such kind of HHT analyses, the damage mechanisms could be explored more precisely when combined with the observation results of the fractographs of the CWK composite under various strain rates.