Experimental Characterization of Textile Energy Absorbers Exposed to Environmental Conditionings

Open Access
Author:
Miller, Simon W
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 21, 2011
Committee Members:
  • Christopher Rahn, Thesis Advisor
  • Michael Andrew Yukish, Thesis Advisor
  • Charles E Bakis, Thesis Advisor
Keywords:
  • textile
  • energy absorber
  • load limiter
  • tear webbing
  • stitch ripping device
  • environmental conditioning
  • quasi static
  • high rate
  • crashworthy
  • restraint
Abstract:
This thesis describes an experimental investigation of sub-scale textile energy absorbers for use in rotorcraft cargo restraint systems. The energy absorbers tested are textile based devices that use sacrificial elements to dissipate the kinetic energy of a moving object. The two types of devices characterized are nylon stitch-ripping devices and polyester tear webbing. A series of environmental conditioning protocols were imposed onto the textile load limiters to determine their fitness-for-purpose. The test specimens were exposed to laboratory ambient, salt-fog spray, isopropyl alcohol, hydraulic fluid, hot-water immersion, kerosene, and high and low temperatures at quasi-static rates. The devices were also tested dynamically over a range of speeds between 0 and 15 m/sec at ambient conditions. Devices were quantified using performance metrics of specific energy absorption, volumetric energy absorption, linear energy absorption, and coefficient of variation of force. The energy absorbers load profiles and energy absorbing capabilities were found to be mostly invariant to the selected conditions for quasi-static testing. However, exposure of the devices to extreme temperatures did result in the most variance in energy absorbing metrics as compared to ambient conditions. Two unique failures occurred in tear webbings that were exposed to hydraulic fluid or kerosene, one failure in each condition; the devices experienced warp fiber breakage prematurely. The energy dissipation performance metrics were found to be invariant to rate effects across tested speeds. Stitch-ripping devices showed a slight increase in force variations with rate whereas tear webbings demonstrated a significant decrease. At these high rates, it is hypothesized that the tear webbing's sacrificial elements break at the interface between the webbings instead of slipping and pulling through the webbings.