My group did an experiment on rubber bands. The rubber bands were stretched multiple times from 50, 100 and 150 times and then a weight was attached to the rubber band to record its extension. On average the rubber band's extension increased by 10 cm after each increment of 50 stretches. I thought the rubber band was getting worn out and was slowly reaching its elastic limit, hence, the rubber band extension got longer. However, i couldn't find any theory as to why this had occurred or supporting my observation. Thanks for the help.