Testing machine: Instron ElectroPuls E10,000 (Instron, Bucks, UK)
Samples shaped to dumbell shapes (working cross-sectional area ~3.5x5 mm, gauge length 30 mm). Accurate measurements taken immediately prior to testing.
Samples mounted in bespoke cryogrips
10 kN load cell
Preconditioning: 10 cycles (0 to 50 N, 0.5 Hz, load control)
Testing: Ramp to failure at 1%/s, 10%/s or 100%/s
Data recording: 10 Hz
Stress-strain data was then fitted to a bi-linear model using non-linear least squares regression using a custom Matlab script. This was used to determine the elastic moduli in the toe and linear regions, as well as the transition strain and transition stress.