The included experimental data for the biaxial deformation of vulcanized rubber was measured in 1944 by L.R.G. Treloar and in 1975 by Treloar and D.F. Jones.
The datasets are provided as tab-separated ASCII-files. Obvious minor typographical errors were corrected.

Each file contains the measurements for a single experiment of bi- or uniaxial deformation. For the specific setup, please refer to the original publication of the data:
L.R.G. Treloar: Stress-strain data for vulcanised rubber under various types of deformation, Trans. Faraday Soc., 40, 59, 1944;
D.F. Jones and L.R.G. Treloar: The properties of rubber in pure homogeneous strain, J. Phys. D: Appl. Phys. 8 1285, 1975.

The following notation is employed:
lambda (lambda1,...) denotes the stretch ratio,
t(t1,...) denotes force per undeformed area (nominal stress),
sigma (sigma1,...) denotes force per deformed area (Cauchy stress),
sigmaDifference := sigma1 - sigma2.

The unit of measurement for the stress is kg/cm^2 for the 1944 data and N/mm^2 in the 1975 dataset.

Thanks to L.R.G. Treloar and D.F. Jones for conducting the experiments as well as to R. Ogden for providing the data.
