Cohesive micromechanics: A new approach for progressive damage modeling in laminated composites

A new cohesive micromechanical modeling framework is presented for the progressive damage analysis of laminated composite materials and structures. The cohesive micromechanics (CM) modeling approach is based on simplified 3D unit cell with incremental and damage formulations. The unidirectional CM model formulated in this paper is implemented in a local-global nonlinear damage modeling framework that recognizes the fiber and matrix constituents along with the cohesive interface/ interphase subcells at the lower level. The cohesive elements are embedded between the fiber-fiber, fiber-matrix, and matrix-matrix subcells. Separate tension and compression traction-separation constitutive relations are used for the cohesive subcells in order to degrade the traction and internal resisting force across the plane between the two adjacent constituents. As a result, progressive damage modeling in the structural level can be achieved at the micromechanical level while maintaining the full advantage of using concurrent nonlinear micromechanical modeling prior and during damage progression spanning the entire structure. The proposed CM damage framework allows nonlinear anisotropic response, including strain softening, and damaged elastic loading/unloading behavior. Robust and efficient numerical stress correction algorithms have been also developed in order to satisfy the local traction continuity and strain compatibility of the micromechanical model. The effectiveness of the proposed modeling approach is demonstrated by predicting the response of composite plates with an open hole under tension and compression loading using available test results from the literature.