A STUDY OF THE LIFETIME OF ARAMID FIBERS UNDER CONSTANT STRESS

In this study, we investigate the lifetime of aramid fibers, specifically Kevlar 49, under constant stress conditions. The objective is to understand the performance and reliability of single filaments subjected to varying stress levels at room temperature. We employed a series of experiments utilizing two spools of Kevlar 49 from the same production lot, which allowed us to analyze the data within the framework of the power law breakdown model. Our results indicate that the lifetime data follow a standard two-parameter Weibull distribution, showing significant variability in lifetime related to mean strength differences. Notably, filaments drawn from the spool exhibiting greater mean strength demonstrated median lifetimes about an order of magnitude longer than those from the other spool; however, no differences were observed when filament strength populations were considered. Furthermore, the lifetime behavior of single filaments parallels that of Kevlar/epoxy strands, showing three distinct time domains characterized by different power law exponents. These exponents align closely with those found in epoxy impregnated strands, confirming the applicability of our findings across different materials.