Description and Application of an Acoustic Pulse Detector to Nylon 6 and Polypropylene Single Fiber Fracture

Abstract

We have developed a microcomputer-based instrument for detecting and analyzing the acoustic frequency pulse generated upon fracture of single filaments. The current generation of instruments can determine the pulse height and width; work is underway on the next generation of equipment, which will allow further analysis of the acoustic signal and testing of a bundle of fibers. The nylon 6 (PA6) and polypropylene (PP) fibers, produced in-house with selected draw ratios and denier, are broken using stan dard tensile testing techniques; hence, the filament tensile properties of the specimens are easily compared with the characteristics of the associated acoustic pulse. The general shape of the acoustic pulse energy data distribution is skewed, such as that of a Poisson distribution; hence, we have calculated the median of the data for use in our analyses. Increasing the test gauge length increases the width of the acoustic pulse. We have found that fiber linear density has no significant direct effect on the acoustic pulse parameters. The acoustic pulse energy density (energy/unit area) correlates closely with the tensile work-to break of the fibers. There is a steeper slope to this relationship for the PP than for the PA6 fibers. From these observations, we can conclude that analyzing the acoustic pulse generated by breaking fibers provides information about the test length and, for fibers of the same polymer type, the average tensile rupture energy.