A new look at lightweight energy absorbing devices for heavy cargo restraints

This investigation explores new concepts for lightweight energy-absorbing devices for heavy cargo restraints for rotorcraft. The technologies considered are stitch ripping devices (SRD) and tear webbing. Both offer excellent performance in terms of specific energy absorption (SEA) and stroke-to-length ratio. This study examines the effectiveness of various adhesive treatments to prevent premature stitch slippage and pull-out, and investigates the role of stitch pattern and stitch density on energy absorption. Development of a simple analytical model for predicting SRD behavior is also presented. Results indicate that certain adhesive treatments increase total energy absorption and reduce stitch pull-out. However, decreases in SEA 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, analytical modeling predicts that an 88% increase in energy absorption over current SRD technology can be realized with further optimization.