Effect of Griffith precracks on measurement of composite fracture toughness.
The objective of this study was to produce true Griffith-type cracks in composite specimens for measuring fracture toughness. A compact test specimen geometry, conforming to the ASTM standard (E-399-84) was chosen for the evaluation. Five methods of precracking were evaluated: 1) placing no precrack (notch in specimen left blunt); 2) placing a sharp notch with a Bard Parker blade under hand pressure; 3) placing a sharp notch with a Bard Parker blade under hand pressure, followed by stressing the sample at 60% of the failure load for 25 cycles; 4) forming a sharp notch by placing a razor blade in the sample during polymerization; and 5) placing a Griffith-type crack. Results indicate that the method of precracking a sample does have a significant effect on the measured value of the fracture toughness.
Kovarik
R E
RE
Department of Oral Health Practice, University of Kentucky College of Dentistry, Lexington.
Fairhurst
C W
CW
D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D006244:Hardness; D008422:Materials Testing / Q000379:methods / Q000592:standards; D014520:Urethane / Q000737:chemistry*
D003188:Composite Resins; C056413:Occlusin; D014520:Urethane