Fatigue damage of APC-2 composite assessed from material degradation and non-destructive evaluation data

Quasi-isotropic 45 degrees APC-2 specimens are fatigued under constant amplitude stress reversal load condition. Fatigue induced degradation of the mechanical properties is correlated to data obtained from non-destructive evaluation. C-scan readings were used to define a generic damage severity factor D. It refers to the current fatigue damage state and accounts for the varying severity of damage at the different specimen locations. Analytical expressions are developed to relate D to the axial stiffness, residual strength and interlaminar shear strength. An indication of damage tolerance can thus be made for evaluating the integrity of structural components. (C) 1999 Elsevier Science Ltd. All rights reserved.