Fracture Strain Of Polymers Thermoplastics
In tensile testing, engineering thermoplastic materials can sustain large deformation after necking. This behavior causes difficulties in strain measurement and in the determination of true stress and true strain, particularly at higher strain rates. This paper discussed the measurement of true fracture strain. Three methods were investigated: the area reduction, elongation over the necked zone, and elongation over the gage length. With strain localization, strain measured by an extensometer becomes gage length dependent. To address the issue, an algorithm was formulated that estimate the average fracture strain over an arbitrary gage length from the fracture strain measured over the necked zone. This paper also presented an analysis based two-step correction scheme for the crosshead extension to be used to supplement the strain measurement from the extensometer.
Keywords: Polymer; Fracture; Plastic; Damage