Journal of Mechanical Science and Technology 32 (1) (2018) 121~127 www.springerlink.com/content/1738-494x(Print)/1976-3824(Online) DOI 10.1007/s12206-017-1213-y Elasto-plastic damage model considering cohesive matrix interface layers for composite laminates † Bibekananda Mandal * and Anupam Chakrabarti Department of Civil Engineering, Indian Institute of Technology, Roorkee, India (Manuscript Received February 21, 2017; Revised August 23, 2017; Accepted August 26, 2017) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract A three-dimensional (3D) Finite element (FE)-based progressive damage model, which considers the interface matrix layer between two neighboring laminae as a layer of cohesive elements, is proposed to analyze laminated composite plates. An elasto-plastic damage model is integrated with the FE-based program ABAQUS that uses user-defined material subroutine. The present damage model includes fiber failure, matrix failure, and delamination effects. A cohesive zone model, which is available in ABAQUS and uses cohesive ele- ments, is combined with the proposed model to address the delamination damage in the interface layers. 3D solid brick elements are used to model composite layers, and cohesive zone elements are used in between two composite layers to model the adhesive layers. The pro- posed model has been applied for the progressive damage simulation of AS4/PEEK composite laminates under in-plane and uniaxial tensile loading. Keywords: ABAQUS user-defined material subroutine; Laminated composite; Cohesive zone model; Damage; Finite element method ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction The use of Fiber reinforced plastic (FRP) composite materi- als is popular in numerous engineering applications, such as aerospace structures, military vehicles, bridge, and shipbuild- ing, due to their superior material properties. These properties include immense weight saving without compromising strength and good fatigue and corrosion resistance. However, analysis of the laminated composite structures is more com- plicated compared to that of structures made of conventional materials due to their layered form and inhomogeneous prop- erties. In addition, a few extra modes of failure, which require advance analysis procedures to predict the actual behavior of the structure, exist. Composite laminates containing blunt notches are common in several structures, especially in the aerospace industry. The accurate analysis of a structural com- ponent with a blunt notch is vital for proper design and suc- cessful performance of the entire structure. Progressive dam- age analysis is found to be essential to predict the performance of composite laminates under various loadings and boundary conditions. Various failure criteria and damage models for laminated composites include average stress criterion proposed by Nuismer and Whitney [1] and damage zone model presented by Backlund and Aronsson [2]. Afaghi-Khatibi et al. [3] de- veloped an effective crack growth model to calculate the ulti- mate load of composite laminates. A Progressive damage model (PDM) was first developed by Chang and Chang [4] for a laminated plate subjected to tensile load. Shahid and Chang [5] further extended PDM to analyze a laminate sub- jected to compression loading. Lessard and Shokrieh [6] fur- ther extended this model to investigate a pinned joint failure using a two-dimensional model. PDM is found to be an ex- tremely powerful model for the failure analysis of laminated composite plates. However, only a small number of literature can accurately predict the strength and failure pattern. Continuum damage mechanics (CDM) offers a suitable framework to model damage initiation and accumulation. Several CDM-based material models are available in the Refs. [7-11]. Many models are based on the elastic damage model. However, the experimental studies reported in the Refs. [11- 14] reveal that a few laminated composite materials, such as AS4/PEEK, exhibit elastic-plastic behavior prior to failure. Thus, an elastic-plastic damage model is essential for such type of composites. Notably, for AS4/PEEK laminates, elastic damage can be considered in the fiber and the transverse di- rections, while isotropic hardening can be considered in the shear direction [11]. However, CDM-based failure models available in the litera- ture are mainly based on shell elements [9, 11]. In this paper, an elasto-plastic continuum damage mechanics model consid- * Corresponding author. Tel.: +91 1332 285844 E-mail address: bibekdce@iitr.ac.in † Recommended by Associate Editor Jin Weon Kim © KSME & Springer 2018