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Seminar Series - 1996-1997
Static and Fatigue Crack Growth in Epoxy Adhesives and Fractal Dimension
Professor Toru Fujii
Department of Mechanical Engineering and Systems
Doshisha University
Kyoto, Japan
Sponsored by the Department of Engineering Mechanics and the Center for Materials Research and Analysis
Date: Monday, May 19, 1997
Time: 3:00 p.m.
Place: 306 Bancroft Hall
Fractured surfaces of epoxy adhesives under Mode I static and fatigue (cyclic) loadings have fractal characteristics. The effects of rubber modification, adhesive thickness and cross-head speed on static and fatigue fracture surfaces of epoxy adhesives were examined using fractal analysis.
Under static loading, the fractal dimension becomes high due to rubber modification. It is related to the static crack growth properties for both unmodified and rubber-modified adhesives. The following equation gives the relationship
between the observed crack extension resistance, GI and the
fractal dimension, D:
logGI = a1 X D + b1
where a1
and b1 are experimental constants.
Regardless of whether adhesives contain rubber particles or not, the fractal
dimension is not affected by adhesive thickness and cross-head speed.
Under fatigue loading, the fractal dimension of
fractured surfaces becomes high due to rubber modification in the same
energy release rate range, DGI when
DGI
is higher than 100 J/m2. The fractal dimension decreases
with an increase in fatigue crack growth rate. da/dN. The
relationship is given by the following equation:
log S = log (da/dN X DGI)
= a5 X D + b5
where a5
and b5 are experimental constants.
Whether the adhesives contain rubber particles or not, the fractal dimension
as well as the da/dN - DGI
relation is little affected by adhesive thickness.
Back to 1996-1997 Seminars List
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