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Isogeometric Analysis for the Prediction of Damage and Residual-Strength in Laminated Composite Structures



The concept of the Isogeometric Analysis (IGA) is adopted in the framework of structural analysis, where the Kirchhoff-Love theory is used for the development of efficient shell elements for the simulation of full scale components. The proposed multi-layer modeling approach consists of the representation of composite laminates at the level of individual plies, or group of similar plies, connected through cohesive interfaces. The novel cohesive interface formulation, which is specifically developed to be used in combination with thin shell elements, is equipped with a Mixed-Mode Cohesive Model (MMCM) in order to predict the onset and the propagation of the delamination. The interlaminar damage, such as matrix cracking, fiber breaking and pullout, are modeled at the lamina level by degrading the pristine elastic properties of the material. This methodology introduces mesh-dependency and damage localization. A nonlocal damage model is therefore investigated in order to alleviate the dependency of the solution with respect to the adopted discretization. The formulation is validated through the correlation with an experimental test from the literature. The model aims to simulate the damage caused by a low-velocity impact on a flat composite coupon. The richness of the isogeometric design-toanalysis concept is then illustrated. A commercial NURBS-based CAD software is used to create the multi-layer model of a reinforced composite panel typical of aerospace structures. The IGA analysis framework is then used to predict the damage caused by a mid-energy impact. It is found that the higher-order continuity of the NURBS shape functions translates into a better representation of the strains, which drive the intralaminar damage model, and of the displacement jumps in the area of the delamination front, which drive the MMCM. Therefore, IGA simulations remain stable and accurate at low number of DOFs even when severe intralaminar damage and delamination occurs.

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