Following the formula, the Young’s modulus for this object is calculated as: E = (2000N/(18.09mm*4.56mm))/((1.2mm-0.3mm)/20.61mm) = 555.22[N/mm^2] = 555.22[MPa] = 0.56 [GPa].
It is almost one-third of the Young’s Modulus of ordinary ABS plastics.
There observed some stress and deformation left on the material.
Plastic buckle
I cut this buckle piece out from a neck strap.
The object consists of the strap parts (textile) and the buckle part (plastic) between them.
Here is the result. Blue indicates the relationship between load and extension; Red is the trend line of the linear part.
383.44 N (39.13 Kg) was the maximum load before it broke.
Red circle indicates some slack was resolved then. I observed enough tension on the straps and the buckle parts after 10mm and onwards till it was broken.
The connection between the strap and the buckle was broken.