Issue 42

O. Krepl et alii, Frattura ed Integrità Strutturale, 42 (2017) 66-73; DOI: 10.3221/IGF-ESIS.42.08 66 Focused on Mechanical Fatigue of Metals Crack onset assessment near the sharp material inclusion tip by means of modified maximum tangential stress criterion Ondřej Krepl, Jan Klusák CEITEC IPM, Institute of Physics of Materials AS CR, Žižkova 22, Brno 616 62, Czech Republic krepl@ipm.cz A BSTRACT . In the case of particle reinforced composites, where the particles are in a form of sharp material inclusions, singular stress concentration exists on each tip of each inclusion. This is due to the geometric and material discontinuities between matrix and particle. These points of stress concentration are susceptible of crack initiation and thus often responsible for failure of the whole structure. The modified maximum tangential stress criterion is employed in order to predict crack onset conditions. K EYWORDS . Sharp Material Inclusion; Singular and Non-singular Stress Terms; Generalized Fracture Mechanics. Citation: Krepl, O., Klusák, J., Crack onset assessment near the sharp material inclusion tip by means of modified maximum tangential stress criterion, Frattura ed Integrità Strutturale, 42 (2017) 66-73. Received: 31.05.2017 Accepted: 08.06.2017 Published: 01.10.2017 Copyright: © 2017 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 omposites find application in a variety of engineering structures. Overall excellent properties, which can only be achieved by combination of two or more homogenous materials, bring solution for high demands given by contemporary advanced technologies. However, the very nature of composites also causes a difficulty in their assessment in terms of fracture mechanics. Common composite types, i.e. fibre reinforced composites or particle reinforced composites give rise to points of singular stress concentration. These points are found in loci where fibre ends are embedded in matrix or at each tip of each sharp particle and are referred as General Singular Stress Concentrators (GSSCs). This paper deals with the case of particle embedded in matrix which is in a form of Sharp Material Inclusion (SMI). The strength of singularity in this case is different and lower than in the case of a crack. However, the GSSCs are points often susceptible for crack initiation and thus they can be responsible for failure of the whole structure. A thorough understanding of crack initiation conditions in GSSC leads to improved estimation of the critical failure load. Stress, energy or coupled criteria are commonly used in fracture mechanics analyses of many GSSC types such as sharp notches. These criteria can be employed in order to predict crack onset conditions to the case of SMI. The GSSC characterized by weak singularity often require consideration of higher order non-singular terms of the asymptotic stress series to describe the stress state and thus to receive consistent critical load predictions. Suggestion of modified maximum tangential stress stability criterion for the SMI with consideration of non-singular terms is the main objective of this paper. C