Issue 46

V. Rizov, Frattura ed Integrità Strutturale, 46 (2018) 158-177; DOI: 10.3221/IGF-ESIS.46.16 158 Developments in the fracture and fatigue assessment of materials and structures Analysis of cylindrical delamination cracks in multilayered functionally graded non-linear elastic circular shafts under combined loads Victor Rizov Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky blvd., 1046 – Sofia, Bulgaria v_rizov_fhe@uacg.bg A BSTRACT . This paper is focused on delamination fracture analyses of a multilayered functionally graded circular shaft under two loading combinations (centric tension and torsion, and bending and torsion) assuming non-linear elastic mechanical behavior of the material. The loading combinations under consideration generate mixed-mode II/III delamination crack loading conditions (the centric tension and bending generate mode II crack loading, while the torsion is responsible for mode III crack loading). The shaft is made by concentric longitudinal layers. The number of layers is arbitrary. Besides, each layer has individual thickness and material properties. The material in each layer is functionally graded in radial direction. Hyperbolic laws are used to describe the continuous variation of material properties in radial direction. A cylindrical delamination crack (the crack front is a circle) is located arbitrary between layers. The delamination fracture is studied in terms of the strain energy release rate by analyzing the energy balance. In order to verify the solution obtained, the strain energy release rate is derived also by differentiating the complementary strain energy with respect to the delamination crack area. Parametric investigations of the behavior of the cylindrical delamination crack are carried-out. The present paper is a contribution in the fracture mechanics of multilayered functionally graded non-linear elastic circular shafts under combined loads. K EYWORDS . Multilayered circular shaft; Functionally graded material; Cylindrical delamination crack; Material non-linearity; Combined loads. Citation: Rizov, V., Analysis of cylindrical delamination cracks in multilayered functionally graded non-linear elastic circular shafts under combined loads, Frattura ed Integrità Strutturale, 46 (2018) 158-177. Received: 04.05.2018 Accepted: 03.06.2018 Published: 01.10.2018 Copyright: © 2018 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION ne of the main advantages of the functionally graded materials over the traditional structural materials is the material property graded distribution [1 - 6]. Very often, fracture is the critical failure mode for the functionally graded structures to lose their structural capacity [7 - 10]. Therefore, the study of fracture mechanics of O