Hierarchical material models with microstructure for nonlinear analysis of progressive damage in laminated composite structures

This study presents new comprehensive nonlinear structural modeling approaches using hierarchical 3D micromechanical models for the analysis of progressive damage in laminated structures. Each approach is generally a synthesis of three components: a nonlinear material model for the matrix behavior; a micromodel for the unidirectional lamina; and a sublaminate model for a repeating ply stacking sequence. Newly developed orthotropic elastic-degrading (ED) material models are formulated in order to represent the nonlinear brittle behavior of the matrix constituent. As a result, progressive damage behavior of a lamina is effectively modeled. A unified development of a new class of constant deformation cell (CDC) micromodels is presented to synthesize the nonlinear response of a unidirectional lamina from the response of the micromodel subcells. Two structural modeling approaches for nonlinear analysis of laminated composites are utilized in this study. The first, for the analysis of multi-layered thick-section composites, uses the 3D sublaminate model; it represents the nonlinear effective continuum response of a through-thickness repeating stacking sequence. The ED material models and the CDC micromodels are employed within the sublaminate model. The second, for the analysis of thin-section laminated composites, uses ply-by-ply modeling; the ED material model and a CDC micromodel are used to represent the effective response of each layer.;New stress update solution algorithms are developed in this study for the CDC micromodels and the sublaminate model; they are well suited for nonlinear displacement-based finite element analysis. Several different applications are presented and comparisons are made with reported experimental results. The proposed micromodels are shown to be flexible in their ability to model the response of different composite material systems; and the stress update algorithms are shown to be well behaved and robust. Applications presented using the proposed models indicate their suitability as practical, general structural analysis and design tools.