Characterization and Design of Lightweight Energy Absorbing Cargo Restraints
Open Access
- Author:
- Hagon, Matthew J.
- Graduate Program:
- Engineering Mechanics
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- December 18, 2008
- Committee Members:
- Charles E Bakis, Thesis Advisor/Co-Advisor
Michael Andrew Yukish, Thesis Advisor/Co-Advisor - Keywords:
- textiles
SEA
load limiters
energy absorption
VEA
stitch ripping device
cargo restraints - Abstract:
- This thesis describes an analytical and experimental investigation into the energy absorption performance of textile-based load limiting devices. The primary technology considered is the stitch ripping device (SRD). Development of analytical models for predicting SRD behavior is presented. The models account for energy absorption due to webbing stretch, thread rupture and stitch slippage. The models predict the force-displacement behavior of the device, the total amount of energy absorption, and the amount of absorption due to frictional losses from stitch slip. Experimental testing conducted to validate model results exhibits close agreement for the applied load and displacement required to induce thread rupture. Over multiple stitch breaks, the models slightly over estimate the amount of absorbed energy. It is predicted that a lower amount of stitch slip decreases activation force as well as fluctuation of force in the plateau region of the force-displacement curve. Decreasing slip increases the amount of energy that can be absorbed for a given peak force and stroke distance. In addition, the effectiveness of adhesive treatments in preventing stitch slippage and pull-out, and the role of stitch pattern and stitch density on energy absorption are examined. Results indicate that certain adhesive treatments increase total energy absorption and reduce stitch pull-out. However, decreases in specific energy absorption result due to increases in total mass from the addition of adhesive. Hand-stitched thread tests show that altering stitch pattern and reducing pull-out increase rip force and energy absorption by 23% and 16%, respectively. Finally, to assess the performance of SRDs under simulated crash conditions, an instrumented dynamic drop rig was constructed. Tests were conducted with a drop sled moving at free-fall velocity, and a higher, elastic-cord-assisted velocity. For velocities from quasi-static to 6 m/s, no significant trends or changes in SRD average activation force and energy absorption were observed in the experiments.