Question A1: A stress-strain curve is recorded for a cylindrical material specimen under a static tensible test. Please answer the questions for each stress-strain curve reported below: (a) Please list all materials that could show such stress-strain behaviour, and the associated testing conditions. Limit your answer to within 100 words. [4 marks] (b) This is the stress-strain curve of a semi-crystaline polymer material. Please discuss how the molecular and crystaline structure would change during the tensile test, following the curve development in different stages, and why this material has large ductility. Limit your answer to within 100 words