Modeling of facesheet crack growth in titanium–graphite hybrid laminates, Part I

Experimental observations have indicated that in titanium–graphite hybrid laminates, fatigue cracks in the titanium facesheets initiate at free edges as well as in areas of high stress concentration, such as holes and notches. In addition, a delaminated region between the facesheet and the intact plies develops and propagates in the wake of the facesheet crack. This paper investigates different modeling techniques for predicting the coupled damage growth. Two modeling approaches were applied; a two-dimensional bridged-crack (BC) model and the virtual crack closure technique (VCCT). The VCCT was applied in two and three-dimensional finite element models and the trends were shown to be the same for both cases. However, the trends predicted using the VCCT are significantly different than the BC model. The reasons for the discrepancies are discussed. The model predictions are compared to experimental results in the second part of this paper.