A Novel Multiscale Physics-Based Progressive Damage and Failure Modeling Tool for Advanced Composite Structures.

Abstract

A novel, multiscale mechanics model for predicting the evolution of damage and failure in continuous fiber-reinforced laminates was developed. The thermodynamically-based work potential internal state variable (ISV) theory, Schapery theory (ST), is utilized to model matrix microdamage at the lamina level within a finite element method (FEM) setting. Failure due to transverse cracking and fiber breakage is modeled at the microscale within a repeating unit cell (RUC) using the semi-analytical generalized method of cells (GMC). A multiscale procedure is employed to link the microscale GMC calculations to the macroscale at every integration point in the FEM model. Micromechanics calculations are precluded if the macroscale damage is below some nominal value, increasing the overall computational efficiency of the multiscale scheme. Computational results and predicted failure modes are compared to experimental data of two center-notched, carbon fiber/epoxy panels containing different stacking sequences. A novel, single-scale extension of ST, the enhanced Schapery theory (EST), is also presented. Three additional ISVs are introduced to account for failure via matrix transverse cracking (mode I and mode II) and fiber breakage (mode I only). These ISVs incorporate a characteristic finite element length scale, and are directly related to the fracture toughnesses of the material. In doing so, the pathological mesh dependency, resulting from the failure degradation scheme that was used in the previous multiscale model is eliminated; however, the explicit influence of the fiber-matrix architecture is lost. The EST model is evaluated against the same center-notched panel data. Finally, a mesh objective, smeared crack band model is implemented into the high-fidelity generalized method of cells (HFGMC) micromechanics theory. This failure model utilizes local fields to resolve the orientation of the crack band locally within the subcells of the RUC. The capabilities of the model are demonstrated using an RUC containing multiple randomly oriented fibers subjected to transverse tension and compression. The results of the model are compared to experimental data, and it is concluded that the newly developed model is viable for mesh objective, multiscale simulations.