In doing a simple tensile test on a metal-polymer sandwich material, the stress-strain curve appears to have 2 elastic regions. i.e. the curve goes like this: i) a very steep straight line (elastic region) ii) a sharp change to a very gentle slope iii) a second steep elastic region iv) gentle yield and slope to failure
It basically looks like one small stress-strain curve then another big one, then failure.
Has anyone noticed the following phenomena, or has any ideas about the reasons for it.
Cheers
anjali