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Notch tip damage zone in biaxially oriented polypropylene at low temperature
Author(s) -
Snyder J.,
Hiltner A.,
Baer E.
Publication year - 1994
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1994.070520209
Subject(s) - materials science , composite material , polypropylene , brittleness , wedge (geometry) , toughness , perpendicular , fracture toughness , delamination (geology) , fracture mechanics , drop (telecommunication) , deformation (meteorology) , tension (geology) , ultimate tensile strength , optics , geometry , geology , paleontology , telecommunications , physics , mathematics , subduction , computer science , tectonics
It is well established that biaxial orientation produces large improvements in the mechanical properties of polypropylene; this study further shows that the large improvements in mechanical behavior are magnified especially below the glass transition temperature. In this study, the irreversible deformation behavior of polypropylene during sharp single‐edge notch tension testing has been studied at two levels of biadial orientation at −40°C. Unoriented polypropylene formed a narrow wedge‐shaped damage zone that grows with increasing stress until catastrophic fracture occurs in a brittle manor. The damage zone consisted of many crazes that mainly grew perpendicular to the loading direction. The 50% oriented material initially developed a wedge‐shaped damage zone that grew wider as loading increased. This resulted in a drop of the length‐to‐width ratio at high sample extensions. The specimen fractured with stable crack growth in a ductile manner, showing a large resistance to crack growth. The 80% oriented material had a circular damage zone that consisted of many delamination crases. These crases grew by splitting the specimen in the thickness direction. Stable crack growth dominated the final failure process with the 80% oriented material showing nearly three times the toughness of the unoriented material. © 1994 John Wiley & Sons, Inc.