Isogeometric Analysis of Damage and Residual-Strength in Aerospace Composite Structures Subjected to Low-Velocity Impact

Abstract

A multi-layered shell modelling approach is developed in the framework of the Isogeometric Analysis (IGA), based on a higher-order accurate and higher-order continuous Non-Uniform Rational B-Splines (NURBS), which allows us to adopt a computationally efficient rotation-free shell formulation. The proposed model is capable of predicting the interlaminar damage modes such as delamination, and the intralaminar damage modes such as matrix cracking due to transverse shear stress and fiber breaking. The IGA shell layers, which represent a single lamina or a groups of lamina, are connected through cohesive interfaces governed by local traction-separation laws. The intralaminar elasto-plastic damage response and the in-plane damage modes related to tension, compression and shear, are evaluated layer by layer at the level of each ply. Two numerical examples are shown. The End-Notched Flexure (ENF) test is first presented as a benchmark case to validate the cohesive-interface formulation. Then, a simple low-velocity impact scenario is considered. The smoothness of the NURBS shell discretization is shown to be beneficial for the penalty formulations adopted for both the cohesive interface and contact with the impactor. Also, due to the higheraccuracy geometry and solution representation enabled via NURBS basis functions, it is found that with the proposed IGA approach, issues that typically affect impact problems, such as through-thickness element distortion/inversion which may cause accuracy loss, shortening of time steps, and numerical instability/crashing of the code, are often circumvented.