Title page for ETD etd-03202001-172207


Type of Document Master's Thesis
Author Gagliano, Jerone Matthew
Author's Email Address jerone@vt.edu
URN etd-03202001-172207
Title An Improved Method for the Fracture Cleavage Testing of Adhesively-Bonded Wood
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Frazier, Charles E. Committee Chair
Dillard, David A. Committee Member
Kander, Ronald G. Committee Member
Love, Brian J. Committee Member
Keywords
  • Adhesive Testing
  • Wood Adhesion
  • Double Cantilever Beam
  • Fracture Mechanics
Date of Defense 2001-01-30
Availability unrestricted
Abstract
This work describes the development of an improved mode I fracture testing procedure for adhesively-bonded wood, and demonstrates the sensitivity of this approach. The two significant improvements were: 1) the use of the flat double cantilever beam (DCB) geometry, which has been uncommon for wood and 2) the application of an established and powerful data analysis using a corrected compliance method from beam theory. Three studies were conducted using various wood adhesives and DCB specimens were fabricated from yellow﷓poplar (Liriodendron tulipifera) sapwood.

The sensitivity of this methodology showed significant differences in fracture performance as the degree of cure increased for a phenol formaldehyde adhesive, and yielded maximum strain energy release rate (SERR) values of 370 - 560 J/m2. A second study showed performance differences between two polymeric diphenylmethane diisocyanate (pMDI) adhesives and one polyurethane adhesive. Typical maximum SERR values were 160 and 130 J/m2 for the pMDI adhesives and 160 J/m2 for the polyurethane adhesive. A third study investigated the effect of loading rates on a cross-linked polyvinyl acetate adhesive and maximum SERR values of 370 - 560 J/m2 were achieved.

Adhesive penetration and cure were determined by image analysis with fluorescence microscopy, and by micro-dielectric analysis, respectively. Since the geometry of the fracture procedure dictates the absence of wood failure, the resulting fractured surfaces were readily analyzable. The surface analysis techniques of laser ionization mass analysis, solid-state nuclear magnetic resonance and field emission scanning electron microscopy were used to investigate the locus of failure for the smooth fractured surfaces.

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