Statistical Aspects of Tensile Fracture of Isotactic Polypropylene

Abstract

The fracture behavior of isotactic polypropylene (iPP) specimen with double-notched shape under a fixed elongation speed at room temperature is described. Over 100 tensile tests were performed, and the statistic fracture data were obtained for the tensile condition. The statistical data of fracture were obtained by examining the time to fracture, the ultimate stress, and the tensile toughness (determined from the area under the nominal stress–strain curve from the origin to the fracture point). The probability density distributions for time to fracture, the ultimate stress, and the tensile toughness approximately followed the normal Gaussian statistics. Using a linear relationship between stress and elongation time near the fracture point, we can apply a static Kalman filter system to the present fracture data to determine a conditional probability density function. As a consequence, this application makes it possible to predict the probability of fracture of iPP under any static condition.

Keywords:

• isotactic polypropylene
• strain hardening
• tensile fracture
• tensile strength
• tensile toughness

Acknowledgment

The authors would like to express their gratitude to Emeritus Professor C. G. Sell of Nancy, France, for his thoughtful comments and encouragement to accomplish this work.