Towards an advanced modeling of failure mechanisms’ interaction in fiber-reinforced polyester: A mixed-mode loading concept Slah Mzali a , Ali Mkaddem b,c,⇑ , Fatma Elwasli a , Salah Mezlini a a Laboratoire Génie Mécanique, École Nationale d’Ingénieurs de Monastir, Université de Monastir, Tunisia b Engineering College, Faculty of Engineering, University of Jeddah, PO. Box 80327, 21589 Jeddah, Saudi Arabia c MSMP-EA7350, Arts et Métiers ParisTech, Rue Saint Dominique, BP. 508, 51006 Châlons-en-Champagne, France article info Article history: Received 14 May 2016 Revised 10 October 2016 Accepted 18 October 2016 Available online 19 October 2016 Keywords: Glass fiber MST Failure Mixed-mode loading FEA abstract This attempt proposes a Finite Element Approach (FEA) to investigate the tribological behavior of glass fiber reinforced polyester composite. The 3D finite element model was developed upon ABAQUS/ Explicit. The Johnson-Cook criteria were considered for describing the material behavior and damage of both fiber and matrix phases. The fiber/matrix interface behavior was, however, modeled using a thin cohesive zone (CZ). A mixed-mode loading concept was specially adopted to predict delamination prop- agation within the interface. The prevailing wear mechanisms owing to Multi-Scratch Test (MST) were inspected at variable load and attack angle, using scanning electron microscope (SEM). Wear maps were built to highlight the correlation between friction coefficient and wear mechanisms. Predictions of both elementary and interacting mechanisms showed excellent correlation with observations. It was revealed that material removal process varies sensitively with the dominating failure mode. The proposed approach exhibits good ability not only in predicting active mechanisms but also in detecting damage sequences governing the surface integrity during scratching. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction The composite materials have become increasingly popular in several industrial sectors such as astronautics, aeronautics, and transports. In addition to their outstanding mechanical properties, the composite materials possess low densities. In several applica- tions, the identification of their tribological behavior i.e. elemen- tary wear mechanisms, friction, lubricant absorption rate, etc. still remain, however, challenging. The anisotropic nature of such materials makes it difficult both the experimental testing and the numerical modeling due to the interaction of elementary mecha- nisms and difficulty of controlling the interface behavior. The local analysis is mostly used to study the wear mechanisms evolution. In some attempts, the local approach analysis was used to investigate the tribological properties of each composite constituent sepa- rately. Scratch test is among the most known techniques used for characterizing tribological behavior of metals [1–3], polymers [4,5], and composites [6,7]. Kim et al. [8] studied the effect of fibers’ rate and direction on friction, and wear of short glass fibers reinforced polyamide (PA12) by using a block-on-ring tribotester. They demonstrated that the composite wear rate decreases with the increase of the fibers’ amount. A better wear resistance was detected with a com- posite containing 30 wt% of glass fiber. They also proved the sensi- tivity of tribological behavior of the composite to temperature and fiber amount. Using pin-on-disk test, Quintelier et al. [9] investigated the wear mechanisms in glass fiber reinforced polyester (GFRP) com- posites at dry sliding conditions. They proved that the initial fibers’ breakage is always occurring in a cross section regardless of the fiber orientation. In the case of sliding perpendicular to fiber orien- tation, the initial fiber fracture was attributed to bending causing longitudinal strains. When the fiber orientation is parallel to the sliding direction, high stresses are found to be responsible of the shearing forces. According to the SEM observations, typical com- posite wear mechanisms, i.e. fiber breaking, fiber/matrix interface debonding, matrix fracture, and fiber pullout, were highlighted. Wear maps were commonly used in open literature to achieve a better correlation between the tribological parameters and the wear mechanisms [10–12]. Using this analysis technique, Briscoe et al. [13] demonstrated the sensitivity of wear mechanisms to the conical indenter angle and the cure temperature owing to GFRP scratch test. For low angles, it was shown that ductile or http://dx.doi.org/10.1016/j.compstruct.2016.10.074 0263-8223/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: MSMP-EA7350, Arts et Métiers ParisTech, Rue Saint Dominique, BP. 508, 51006 Châlons-en-Champagne, France. E-mail address: ali.mkaddem@ensam.fr (A. Mkaddem). Composite Structures 160 (2017) 70–80 Contents lists available at ScienceDirect Composite Structures journal homepage: www.elsevier.com/locate/compstruct