Contents lists available at ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct Impact model of WC/Co composite Eligiusz Postek a , Tomasz Sadowski b, ⁎ a Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, ul. Pawińskiego 5B, Poland b Lublin University of Technology, Department of Solid Mechanics, 20-865 Lublin, Nadbystrzycka 40 Str., Poland ARTICLE INFO Keywords: Cermet Impact load Microcracking Cohesive elements Numerical modelling ABSTRACT WC/Co composite is a standard hard material used for the production of cutting tools. It has both very good thermo-mechanical and wear properties. During the cutting, process tools are subjected to impact loading and gradual degradation due to high-stress concentrations. This loading induced deterioration is complex process still not well investigated and explained. Up till now the dynamic response of the WC/Co composite was analysed under dynamic impulse compressive loading [1]. However, the behaviour of the above two-phase composite under impacts conditions was not in- vestigated in details. In the presented micromechanical approach the real material structure geometry of the internal structure can be performed including spatial distribution of: (1) WC grains and their dimensions, (2) volume content of plastic Co binder with their thickness, (3) system of grain/binder interfaces and (4) cracks initiated and developed during impulse loading, (5) possible brittle grains rotation. The results reveal the dependence of the microcracking processes and the stress distribution on impact ve- locity and presence of discontinuities in the Co binder and the interface zone between the binders and the grains. The microcracks system was evaluated by the damage parameter according to Kachanov, 1986 [62]. 1. Scientific motivation Modern composite materials with ceramic (CMC) or metal matrix (MMC) have complex internal structures having a regular or stochas- tically disordered distribution of the second phase. The special in- dustrial applications require manufacturing of so-called functionally graded, where internal structure of the composite exhibit gradation of physical and mechanical properties. Other types of modern composites are materials with layered structures, which can form regular or irre- gular different phases systems. Various kinds of ceramic matrix composites (CMC) and single-phase ceramics where included in, e.g. [2–4]. Different methods of their modelling, including multi-scale approach, are presented in, e.g. [5–15]. However, nanoceramic materials built of nanoparticles have much more complex internal structures, e.g. [16]. Other kinds of modern composites are: (1) “so-called” functionally graded materials, e.g. [17–21] and (2) cermets (CMs) where tungsten carbide/cobalt (WC/Co) or titanium/molybdenum carbides are the most popular, e.g. [22–27]. Different methods can be applied to modelling of the overall prop- erties of heterogeneous materials, e.g. [28–32]. In the micromechanical approach a Representative Volume Elements (RVE) containing different phases and impurities is created and due to material thermo-mechan- ical loading types of structural defects (dislocations, pores, cracks) in- itiate and growth inside the material. Description of a new composite behaviour at different scales are widely discussed in many contributions, e.g. [33–38]. For example in [33–35] authors propose a decomposition of the problem of the com- posites modelling into a coarse scale and fine scale which coupling can be done by various discretisation methods, e.g. finite: (1) element, (2) difference or (3) volume methods. Authors [37] proposed a variational version of the multiscale method, which coupling both physical and mechanical features. Modelling of the mechanical behaviour of the WC/Co composite under impact loading, presented in this contribution, is much more complicated because it consists of brittle grains and plastic binder (Co). The first experimental investigations concerning estimation of WC/Co properties and microstructure geometry was reported in [22]. In gen- eral, the CM structure has discontinue plastic interfaces in 2-D, how- ever, the real 3-D microstructure of interfaces can be treated as con- tinuous, but of very thin thickness, e.g. [1]. In our model of impact WC/Co mechanical response, we use meso- mechanical approach for creation the RVE, which contains extremely brittle elastic grains with very narrow thin continuous interfaces, https://doi.org/10.1016/j.compstruct.2019.01.084 Received 20 October 2018; Received in revised form 5 January 2019; Accepted 25 January 2019 ⁎ Corresponding author. E-mail address: t.sadowski@pollub.pl (T. Sadowski). Composite Structures 213 (2019) 231–242 Available online 29 January 2019 0263-8223/ © 2019 Elsevier Ltd. All rights reserved. T