Open Hole Multilayer Fatigue Crack Growth in Glare Under Combined Tension Bending

摘要

This paper involves the development of an analytical/numerical crack growth model to predict surface and subsurface fatigue crack growth in the fibre metal laminate (FML) Glare subjected to combined tension and bending. The stress intensity factor for Glare can be divided into two parts: the stress intensity due to the crack opening stresses, and the stress intensity due to the fibre bridging stresses. The first component is derived from a stress intensity formulation for specimen geometry of monolithic aluminum. The second component is dependent upon the shape of the delamination surrounding the crack and the stresses in the fibres. Delamination shapes were taken from experimental observations, and fibre-bridging stresses were extracted from FEM. Using this approach, predictions are made on crack growth in the Glare surface layer and sub-surface layers. A new milled open-hole tension bending (MOHTB) fatigue specimen was developed to induce combined tension and bending in Glare specimens. This configuration avoids plastic deformations and spurious fatigue cracking observed in standard open-hole tension bending specimens. Fatigue tests were carried out on Glare 2A-5/4-0.4 and Glare 2A-6/5-0.4 specimens. Data on the crack initiation periods in each of the layers are also presented. The comparison between the predicted fatigue crack growth in the aluminum layers and the experimental observations indicated a good agreement both for shape and scale of the crack growth curves.