- Agrawal, C.M. and Pearsall, G.W., The application of fractography to the interpretation of fracture toughness values for polycarbonate,
ISTFA 1988: International Symposium for Testing and Failure Analysis. The Failure Analysis Forum for Microelectronics and Advanced Materials. Conference Proceedings
pp. 403 - 9 .
(last updated on 2007/04/10)
Fracture toughness tests were conducted on LEXAN (TM) polycarbonate specimens machined from extruded sheet into the compact tension specimen geometry specified for metals by ASTM Standard E399-83. The effects of different geometric parameters, including the initial crack length and ligament length, were investigated. The principal test variable, in addition to specimen geometry, was the crosshead speed of the testing machine. Various features of the fracture surface were interpreted with aid of both optical and scanning electron microscopy and yielded insights into the effects of both geometric and test variables. The fracture toughness was influenced by the patterns of crazing at the initiation of unstable crack propagation. The principal reasons for these trends are the importance of the initiation phase of the fracture (associated with craze formation and propagation) and of maintaining plane stain conditions in order to develop reproducible unstable fracture propagation with minimum energy absorption. The applicability of ASTM E399-83, which was developed for metals, is discussed in the light of the present results
crazing;fractography;fracture toughness testing;plastics;scanning electron microscope examination of materials;