Fracture zone Characterization—Micro-Mechanical Study

Authors

  • Svetlana Vasic
  • Ian Smith
  • Eric Landis

Keywords:

Fracture mechanics, fracture zone, <i>in-situ</i> real-time SEM observations, crack profiles, fiber bridging, toughening

Abstract

The experimental and numerical characterization of the fracture process zone in softwoods is presented. In-situ real-time Scanning Electron Microscopy (SEM) was used as a tool to examine the physical mechanism of fracture in softwoods (spruce) using end-tapered Double Cantilever Beam specimens. Fracture process zone has been characterized in terms of failure mechanisms. It was found that bridging behind the crack tip is the main toughening mechanism, which contributes to nonlinear wood behavior in the presence of stress concentrations.

References

ACI 446.1 R-1. 1991. Fracture mechanics of concrete: Concepts, models, determination of material properties. Report by American Concrete Institute Committee, 446, Detroit, MI. 108 pp.nAshby, M. F., F. R. S. Easterling, R. Harryson, and S. K. Maiti. 1984. The fracture and toughness of wood. Report, Cambridge University, Dept. of Engineering, Cambridge, UK. 82 pp.nAtkinson, B. K. 1987. Introduction to fracture mechanics and its geophysical applications. pages 1-27 in B. K. Atkinson, ed. Fracture mechanics of rocks. Academic Press Ltd., London, UK.nAtkinson, B. K., and P. G. Meredith. 1987. The theory of sub-critical crack growth with application to minerals and rocks, pages 58-77 in B. K. Atkinson, ed. Fracture mechanics of rocks, Academic Press Ltd., London, UK.nAttack, D., W. D. May, E. L. Morris, and R. N. Sproule. 1961. The energy of tensile and cleavage fracture of black spruce, Tappi44(8):555-567.nBostrom, L. 1992. Method for determination of the softening behavior of wood and applicability of a non-linear fracture mechanics model, Report TVBM—1012, Lund University, Lund, Sweden.nBroek, D. 1982. Elementary engineering fracture mechanics. Martinus Nijhoff Publishers. The Hague, The Netherlands.nKnott, J. F. 1973. Fundamentals of fracture mechanics. Butterworth & Co., London. UK.nMai, Y. W. 1975. On the velocity-dependent fracture toughness of wood. Wood Science8(1):364-367.nPorter, A. W. 1964. On the mechanics of fracture in wood. Forest Prod. J., 14(8):325-331.nRodel, J., J. F. Kelly, and B. R. Lawn. 1990. In situ measurements of bridged crack interfaces in the scanning electron microscope. J. Am. Ceramic Soc.73(11): 3313-3318.nSih, G. C., P. C. Paris, and G. R. Irwin. 1965. On cracks in rectilinear anisotropic bodies. Int. J. Fracture1:189-203.nSmith, I., and G. Springer. 1993. Consideration of Gustafsson's proposed eurocode 5 failure criterion for notched timber beams. Can. J. Civil Eng.20(6):1030-1036.nSmith, I., and Y. H. Chui. 1994. Factors affecting mode I fracture energy of plantation-grown red pine. Wood Sci. Technol.28:147-157.nSmith, I., and L. J. Hu. 1994. Fracture analysis of bolted connections, American Society of Civil Engineers Structural Congress XII, April 25-28, Atlanta, GA, 2: 912-917.nSmith, I., D. M. Tan, and Y. H. Chui. 1996. Critical reaction forces for notched timber members, International Wood Engineering Conference '96, New Orleans, October 28-31, Louisiana State University, Baton Rouge, LA, 3.460-3.466.nValentin, G. H., L. Bostrom, P. J. Gustafsson, A. Ranta-Maunus, and S. Gowda. 1991. Application of fracture mechanics to timber structures, RILEM State-of-the-art report, Technical Research Centre of Finland, Research Notes, 1262. Espoo, Finland.nVasic, S. 2000. Applications of fracture mechanics to wood. Ph.D. thesis, University of New Brunswick, Fredericton, New Brunswick, Canada.nVasic, S., and I. Smith 1996a. On the influence of ultra-structure and fibres bridging in mode I fracture of wood, Proc. 2nd International Conference on the Development of Wood Science/Technology and Forestry ICWSF'96, April 10-12, University of Sopron, Sopron, Hungary.nVasic, S., and I. Smith 1996b. The brittleness of wood in tension perpendicular to the grain: Micro-mechanical aspects. International COST 508 Wood Mechanics Conference, May 14-16, Stuttgart. Office of Publications of the European Communities, Luxembourg: pp. 555-569.nVasic, S., and I. Smith 1998. Bridged crack model of wood fracture: Experimental analysis and numerical modeling, Proc. World Timber Engineering Conference, August 17-20, Montreux, Swiss Federal Institute of Technology, Lausanne. Switzerland. 1.818-1.819.nVasic, S., and I. Smith 1999. The effect of bridging stresses on fracture toughness of wood, RILEM Symposium on Timber Engineering, Sweden, 13-15 September, Stockholm.nYeh, B., and A. P. Schniewind. 1992. Elasto-plastic fracture mechanics of wood using the J-integral method. Wood Fiber Sci.24(3): 364-376.n

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Published

2007-06-05

Issue

Number 1 / January 2002

Section

Research Contributions

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