Relaxation of Kevlar Braided Cords
Abstract
NASA uses Kevlar Aramid Fiber in constant strain applications in the form of braided cord. Questions about its behavior in load relaxation with variables including time, temperature, humidity, initial and re-tensioning loads are probed by this report, beginning with a literature review. Testing was performed at NASA Goddard SFC to attempt to resolve unanswered questions. The results are demonstrative of three important findings: 1) The first is that the initial relaxation phase is generally log-linear. 2) The second finding of this phase of testing is an average relaxation rate (Beta) of- 0.0151%/log(t) with a standard deviation of +/-0.0021. 3) The third finding is that the primary relaxation phase represents a 41% higher relaxation rate than the secondary phase. Kevlar exhibits load relaxation at a rate (Beta) of approximately 0.0110 +/- .0027%/log(t) after preconditioning or primary relaxation. Kevlar's secondary relaxation generally fits a log-linear relaxation model as expected from the literature. The data experienced a short recovery period after reloading and transferring the load to the load cell, which may be traced to material, and/or environmental effects. In general, the data exhibited a wide scatter and several highly erratic responses, which indicate that precisely modeling this material may be impossible.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 28, 2004
- Accession Number
- ADA427417
Entities
People
- Russell B. Fete
Organizations
- George Washington University