The crack growth rate in HMN 5202 and HXM 50100 polyethylcne has bcen studied as a function of
stress intensity using deeply notched three-point bend specimens. l'he load-line displacen~entin
response to a static applied load has been measured, with tlie material compliance as a function of time
determined from the specimen compliance prior to the initiation of crack growth. Measured specimen
compliance as a function of time after crack growth begins is used to determine crack g r o w ~ hrate as a
function of stress intensity. The crack growth rate has been shown to be a fi~nctionof stress intensity.
giving the same crack growth rate h r very different combinations of load and crack length. tvith
The experimentally determined crack growth rate as a Cunction of stress intensity has beell compared
to theoretical predictions by Willia~nsand Scliapery. This comparison implies that both critical crack
tip opening displacement, 6,,, and critical energy rclease rate, G , , increasc with increasing crack
q r o ~ t l rate.
The results also show that the crack growth rate is significantly reduced by plane stress
conditions at the surface of tlie specimen.
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