Modeling Progressive Damage Using Local Displacement Discontinuities Within the FEAMAC Multiscale Modeling Framework

A method for performing progressive damage modeling in composite materials and structures based on continuum level interfacial displacement discontinuities is presented. The proposed method enables the exponential evolution of the interfacial compliance, resulting in unloading of the tractions at the interface after delamination or failure occurs. In this paper, the proposed continuum displacement discontinuity model has been used to simulate failure within both isotropic and orthotropic materials efficiently and to explore the possibility of predicting the crack path, therein. Simulation results obtained from Mode-I and Mode-II fracture compare the proposed approach with the cohesive element approach and Virtual Crack Closure Techniques (VCCT) available within the ABAQUS ® finite element software. Furthermore, an eccentrically loaded 3-point bend test has been simulated with the displacement discontinuity model, and the resulting crack path prediction has been compared with a prediction based on the extended finite element model (XFEM) approach. Carbon fiber reinforced polymers (CFRPs) are used widely for many applications including aircraft, automotive, and civil structures. Some of the appealing properties of CFRPs include high specific strength and stiffness, corrosion resistance, fatigue resistance, and suitability for stealth applications. Increased usage of CFRPs in the future depends on the development of damage-tolerant composite structures while lowering the cost of manufacturing. One of the issues with CFRPs for structural applications is the joining of sections made with fiberreinforced composites. Among other joining methods in current practice, two of the most popular methods are adhesive bonding and mechanical fastening where the mechanical fastening is preferred for thicker sections while adhesive bonding is used for thinner sections. Delamination is a major type of failure associated with adhesively bonded composite joints. In the past, failure of composites has been investigated extensively from the micromechanical and macromechanical points of view. On the micromechanical scale, failure mechanisms are related to the properties of the constituent phases, i. e., matrix, reinforcement, and the interface. This paper will investigate the advantages and disadvantages of modeling damage propagation in materials utilizing a displacement discontinuity approach. The displacement discontinuity approach known as ECI (evolving compliant interface) [1, 2] enables exponential evolution of the interfacial compliance, resulting in unloading of the tractions at the interface after failure/delaminations occurs. The current study utilizes the implementation of this approach available within NASA’s FEAMAC [3] multiscale micromechanics analysis framework. Given the fact that the commercially available techniques such as VCCT [4] and cohesive element [5] approaches require a priori knowledge of the crack path, and as discussed elsewhere [6], the current implementation of these approaches present difficulties with numerical convergence, forcing one to deal with a number of parameters to overcome these convergence issues. Therefore, in this paper, a computationally efficient multiscale modeling framework is presented, and the