Contents lists available at ScienceDirect Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech Investigation of cord-rubber composite durability by the material force method C.M. Popa a , C. Gebhardt a , N. Raje b , B. Steenwyk b , M. Kaliske a,⁎ a Institute for Structural Analysis, Technische Universität Dresden, 01062 Dresden, Germany b Bridgestone Americas, Americas Technical Center, 10 E. Firestone Blvd, Akron, OH 44317, USA ARTICLEINFO Keywords: Cord-reinforced materials Twisted cord reinforcement Fracture mechanics Extended finite element analysis ABSTRACT The research at hand deals with durability analysis of cord-reinforced elastomers using the materialforceconcept.Differenttypesofsteelcordreinforcementareused,inordertodetermine the influence of the cord construction on the fracture sensitivity of the composite product. The composite is analysed using the Extended Finite Element Method to reduce the effort of the meshing process for the complex geometry of twisted reinforcing cords. Material forces are computed at the crack tip area and a qualitative ranking of the different reinforcement types is obtained. The results are successfully compared to experimental investigations. 1. Introduction Cord-reinforced elastomers are composite structures widely used in the production of industrial rubber products, from conveyor and power transmission belts used in industrial plants and factories, to multilayer high-pressure hoses and coated fabrics, as well as tyres,see [5].Cord-reinforcedelastomersaremadeofalow-modulusrubbermatrix–characterisedbyahighdeformationbehaviour, twisted reinforcement – with a much higher strength and the adhesive film (dip), that creates a strong bond between the re- inforcement and the elastomer matrix, see [6]. The combined properties of the composite’s constituents characterise a structure that requires high stiffness in the direction of the reinforcement and high flexibility in the plane perpendicular to the twisted cords. The elastomer matrix has a highly nonlinear stress–strain response to mechanical loading, displaying an upturn of the stress–- strain diagram at large strains. This behaviour is justified by strain-induced crystallisation of filled elastomers, as well as stiffening of polymer chains of elastomers at larger elongation. No yield point before failure is observed and the volume changes are negligible, Poisson’s ratio being close to = 0.5 defining an almost incompressible behaviour. The role of reinforcement in most industrial rubber products is to ensure a high tensile strength-to-weight ratio, the required flexibility as well as low elongation and high mechanical impact resistance. A significant number of scientific papers have been directed towards analysing the behaviour, advantages and improvement strategies for cord-rubber composites, see for example [13,22,23]. Different types of reinforcement have been developed along the years, with the most important ones being, chronologically, cotton,rayon,polyamides(PA6.6,PA6,nylon),polyester(PET),aramidsandpolyethylenenaphtalate(PEN).Steelcordsareanother category of reinforcement for industrial rubber products, that are stronger than the above mentioned fibre materials, have excellent heat and fatigue resistance and are rapidly growing in the reinforcement material development, see [5]. In tyres, the reinforcement definessignificantlytheshape,supportsloadsandprovidestheneededrigidityofthestructureforacceleration,brakingorcornering. https://doi.org/10.1016/j.engfracmech.2020.106909 Received 24 September 2019; Received in revised form 22 January 2020; Accepted 27 January 2020 ⁎ Corresponding author. E-mail address: michael.kaliske@tu-dresden.de (M. Kaliske). Engineering Fracture Mechanics 229 (2020) 106909 Available online 06 March 2020 0013-7944/ © 2020 Elsevier Ltd. All rights reserved. T