Linear Damage Accumulation for Predicting Fatigue in Fiber Metal Laminates

Abstract

DOI: 10.2514/1.42486 This paper presents the experimental and analytical research on the applicability of the linear damage accumulation approach for fatigue crack growth in fiber metal laminates under variable amplitude loading. A recently developed constant amplitude analytical prediction model for fiber metal laminates has been extended to predict fatigue crack growth under variable amplitude loading using a linear damage accumulation rule. The modified model has been compared with crack growth tests on fiber metal laminates center-cracked tension specimen. In the end, it is discussed to what extent or under which conditions the linear damage accumulation predictions are sufficiently accurate for fiber metal laminates structures. Nomenclature a = total crack length aD = delay distance ai = current crack growth increment a0 = initial/total crack length of previous loading cycle Ccg, ncg = crack growth relation constants Kbridging = bridging stress intensity factor Kfar-field = far-field stress intensity factor Ktip = crack-tip stress intensity factor N = number of loading cycles ND = number of delay cycles NOL = number of overload cycles Smax = maximum stress magnitude SOL = overload stress magnitude R = stress ratio RKtip = crack-tip stress ratio ROL = overload stress ratio � Keff = effective stress intensity factor range