|By Dave Santos on Aug. 8, 2019
28027Local Melting Failure Mode of Kite Lines
Branching topic from line-twist to the curious thermodynamics of line failure. We knew that when line breaks it must be a melting effect right at the break, but we had not connected with supporting academic science until now. We knew working line rings and throbs with energy that can concentrate into shockwaves at knots or nicks, causing failure.
Here again we find the DNA model of polymer dynamics applicable
"...Remarkably, the propensity to kink correlated with the thermodynamic destabilization of the mismatched DNA relative the perfectly complementary strand, suggesting that the kinked state is locally melted. The molecular vise is exquisitely sensitive to the sequence-dependent linear and nonlinear elastic properties of dsDNA."
The "molecular vise" applies compression force, and we can see that kite line failure modes based on bending and twisting contain local compression forces. Perhaps compression transients in tensile media are a key failure dynamic. Sudden compression causes temperature to easily spike to UHMWPE melting temp not much higher than 100C.
This is a critical failure mode; that a fast massive kiteplane may slack its line and then snub up hard, and a bit of twist force can create a hockle that jams and melts either partially, as damage, or melts apart (breakaway), in conditions that standard tether engineering calculations are not yet accounting for.
Multi-line topologies continue to look more and more essential to prevent AWES single-line single-point catastrophic failure modes.
"The more ingenious our apparatus, the coarser and more unskillful are our senses."
Jean Jacques Rousseau