Narrow Results

We studied the morphology of yarns obtained from Manila hemp (also known as Abacá) fiber bundles to find a possible correlation with the enhancement in mechanical properties of yarns relative to the original natural fiber bundle. Long Manila hemp fiber bundles had lignin and hemicelluloses removed, twisted and dried to form yarns. Scanning electron micrography revealed that the collapse of lumens inside the fibers leads to densification and consequent increase of tensile properties of the yarns. The densification occurs after the chemical removal of noncellulosic substances from the interstices of cellulose fibrils. These cellulosic elements are then bridged by hydrogen bonds during the drying step of yarn fabrication.

Carbon nanotube (CNT) yarns were drawn from the web found on the CVD furnace wall. The yarns were twisted and their tensile behavior was investigated through in-situ SEM and regular tensile tests. The mechanisms involved in the CNT yarn deformation were identified. The twisted CNT yarns were found to have a good ability to stretch and deform and featured a diameter-dependent strength.

In the process of spinning, the state of machine or inconsequence of corresponding technical parameter will bring various periodic unevenness based on stochastic unevenness of yarn. Spectrum and variance-length curve of yarn signal is not only a primary method to analyze this periodic unevenness of yarn, but also a primary method to check quality of yarn and to diagnose mechanical failure. This paper provided the method to spectrum and variance-length curve of yarn based on wavelet analysis, and established the relation of them. High precision and high calculation speed is demonstrated by this method through experimental comparison and analysis.