A progressive fatigue damage analysis method was developed to predict damage
propagation and residual strength of the adhesively bonded repairs in composites subjected to
constant amplitude cyclic loading. The fatigue damage models of adhesively bonded repairs are
respectively established with different shapes of the patches. Based on the theory of the residual
strength and residual stiffness in composites, the material property degradation technique for
modifying element stiffness and strength and materials ultimate failure criteria were proposed.
This program is able to simulate progressive fatigue damage and predict residual strength of
the adhesively bonded repairs in composites subjected to constant amplitude cyclic loading with
different shapes of the patches. The calculation results of damage model show that the patch
shape and size are important fatigue design parameters of adhesively bonded repairs. The effect
of repair with tilted square patch is the best than others and the residual strength improves by
27.6 % than the unrepaired composite laminates.
Keywords: composite material; 3-D progressive fatigue damage model; patch shape; residual strength.
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