The fracture toughness of tough polyethylenes by a novel high pressure technique
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The failure of two grades of polyethylene has been studied using the technique of torsion under superposed hydrostatic pressure. The behaviour of unnotched samples of both grades was ductile at all pressures and strain-rates. However, at sufficiently high pressures both grades of polyethylene (including a tough copolymer) failed in a brittle manner when a surface notch was exposed to a suitable pressure fluid. Measurement of fracture stresses for various notch depths lead to a value for a critical stress intensity factor at each of several pressures. A linear extrapolation was then used to estimate the critical stress intensity factor at atmospheric pressure to be 1.11±0.05 MN m−3/2 and 1.68±0.08 MN m−3/2 for the homopolymer and copolymer, respectively. An independent measurement at atmospheric pressure for the homopolymer using compact tension geometry yielded a value of 1.28±0.02 MN m−3/2 confirming the accuracy of the extrapolation procedure and that the effect of the environment on the behaviour was not substantial.
KeywordsPolyethylene Fracture Toughness Stress Intensity Factor Hydrostatic Pressure Fracture Stress
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- 1.J. B. Howard, in “Engineering Design for Plastics”, edited by E. Baer (Van Nostrand, New York, 1964) Ch. 11.Google Scholar
- 2.R. W. Truss.R. A. Duckett andI. M. Ward,J. Mater. Sci. 16 (1981) 1689.Google Scholar
- 3.G. R. Irwin,J. Appl. Mech. 29 (1962) 651.Google Scholar
- 5.R. W. Truss, P. D. Clarke, R. A. Duckett andI. M. Ward,J. Polym. Sci.: Polym. Phys. Ed. in press.Google Scholar
- 6.ASTM D2522, Annual Book of ASTM Standards, Part 36 (1980).Google Scholar
- 8.J. E. Srawley andB. Gross, NASA Report TN D-3820 (1967).Google Scholar
- 9.D. R. Roberts, J. F. Mandell andF. J. McGarry, Research Report R81-3 Massachusetts Institute of Technology, April (1981).Google Scholar
- 10.F. A. McClintock andG. R. Irwin, in ASTM STP381 (1965) p. 85.Google Scholar
- 11.ASTM Designation E399 (1981) Part 10 Annual Standards.Google Scholar