Characteristics of stress-strain behavior: ü Modulus of elasticity (stiffness, elastic modulus, Young’s modulus) is the slope of the stress-strain curve in the elastic region ü Yield strength (σ y )is the stress applied to a material that just causes permanent deformation ü Tensile strength (TS) is defined at the fracture point and can be lower than the yield strength ü Ultimate tensile strength is the stress that corresponds to the maximum load ü Elongation at break (%ε) –the increase in length of a specimen under tension before it breaks (Strain). Stress –Strain Behavior P= Applied load A = Original cross-sectional area Strain, ε Stress, σ σ y ε y ε F σ F 2% 0 • E = δ/l . CASE Deformation of Amorphous Polymers Stress-strain curves Deformation of Semicrystallineand crosslinkedPolymers Flexural test Scope: üMeasures the force required to bend a beam under 3 point loading conditions σ σ y ε y ε F σ F 2% 0 • E = δ/l