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The effect of compressive biaxial orientation on the low-temperature toughness and pre-fracture damage of polypropylene

Snyder, Joseph Timothy, II
http://rave.ohiolink.edu/etdc/view?acc_num=case1056558280

Abstract Details

1992, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
In Chapter 1, the irreversible deformation behavior of polypropylene during edge notch tension testing was studied as a function of temperature. Below Tg, a narrow wedge shaped damage zone grew from the notch tip with increased stress. The macroscopic shape of this damage zone was successfully analyzed using the Dugdale model and Goodier and Field equation to predict the damage zone length and notch tip opening displacement. Near the notch tip microscopic crazing was found to follow a path perpendicular to the maximum local stress which is the minor principal stress trajectory. In Chapter 2, biaxial orientation was found to produce major improvements in the mechanical properties of polypropylene below the glass transition temperature. The irreversible deformation of oriented polypropylene ahead of a sharp notch was studied. The 50% oriented material developed a large stress-whitened damage zone that dominated the failure process. The 80% oriented material had a circular damage zone that consisted of many delamination crazes which grew by splitting in the thickness direction, producing a triangular pattern. In Chapter 3, the damage zone in 80% biaxially orient ed polypropylene was analyzed using the elastic stress distribution for a sharp notch specimen. The size and shape of the large central craze was found to follow a critical mean stress criterion, independent of applied stress and specimen thickness. It was also found that the damage zone only grew while σ3 was greater than zero. The development of the triangular profile as well as the smaller crazes was explained using a stress redistribution argument. The growth path of the delamination crazes in the x-z plane appeared be in a direction perpendicular to the direction of σ3. Chapter 4 reports the improvements of biaxial orientation on the low temperature crack growth behavior of polypropylene. Stable crack growth occurred only in the oriented materials with the 80% material having a slower initial crack growth rate than the 50% material, but a higher final steady state growth rate. Fracture surfaces revealed considerable voiding in the 50% case and delamination in the 80% case.
John Wallace (Advisor)
172 p.
effect compressive biaxial orientation low-temperature toughness pre-fracture damage polypropylene

Recommended Citations

Citations

  • Snyder, II, J. T. (1992). The effect of compressive biaxial orientation on the low-temperature toughness and pre-fracture damage of polypropylene [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1056558280

    APA Style (7th edition)

  • Snyder, II, Joseph. The effect of compressive biaxial orientation on the low-temperature toughness and pre-fracture damage of polypropylene. 1992. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1056558280.

    MLA Style (8th edition)

  • Snyder, II, Joseph. "The effect of compressive biaxial orientation on the low-temperature toughness and pre-fracture damage of polypropylene." Doctoral dissertation, Case Western Reserve University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056558280

    Chicago Manual of Style (17th edition)

case1056558280
690
© 1992, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.