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RDCB testing to measure the baseline fatigue resistance of an adhesive system, under ambient conditions, is typically performed in a two-step process. To determine the effects of elevated temperature and/or climate cycling, a third step is introduced.
Part 1 Determine the relationship between test piece compliance C and crack length a
Part 2 Perform cyclic fatigue testing and measure the changes in test piece compliance and peak cyclic force at known intervals
Part 3 Repeat Part 2 under non-ambient conditions
From the relationship measured in Part 1, the crack length of the test piece can be calculated at any given cycle, without the use of expensive and often inconvenient video extensometry techniques.
Nomenclature
A crack length (mm)
a0 initial crack length before fatigue testing (mm)
b test piece width (mm)
C compliance (mm/N)
m measured slope of compliance calibration plots (all modes)
Δ crack length offset from Mode I compliance calibration plot
C0 compliance offset from Mode II and Mixed-Mode I + II compliance calibration plot
GI( max) maximum strain energy release rate in Mode I (J/m2)
GII( max) maximum strain energy release rate in Mode II (J/m2)
GI+II(max) maximum strain energy release rate in Mixed-Mode I + II (J/m2)
N number of fatigue cycles
Ny load per unit width
Pmax maximum force (Newtons)
Pmin minimum force (Newtons)
dmax maximum RDCB opening deflection (mm)
R ratio of Pmax:Pmin
A slope constant for Paris Law relationship: da/dN = AGB
B power constant for Paris Law relationship: da/dN = AGB
Gth measured value of GI( max) at which the fatigue crack growth tends to become negligible - for crack growth rates between 10-6 and 10-7 mm/c (J/m2),
G|10-6 projected value of GI( max) at a crack growth rate of 10-6 mm/c (J/m2)
G|10-7 projected value of GI( max) at a crack growth rate of 10-7 mm/c (J/m2)
Next: Part 1 Compliance Calibration Testing