Polymers – long individual strands that can be stretched. They have cross-linking bonds that initially make it difficult to stretch. Once there are broken/overcome the substance becomes easy to stretch then gradually harder. Some energy is lost in breaking cross-links so a hysteresis loop is observed in unloading.
Strong Material – has a larger Ultimate Tensile Strength
Stiff Material – has a larger Young’s Modulus
Tough Material – larger area under stress-strain graph
Brittle Material – sudden breaking point
Ductile Material – large breaking point