Failure analysis of advanced composites under impact by cohesive zone method

Doğan, Oğuz
The main objective of this study is to investigate the delamination damage of laminated composites subjected to low velocity impact. Three-dimensional finite element analyses are conducted to determine delamination area, shape and location. The impact analysis is performed by using the explicit finite element method which uses the central difference rule to integrate the equations of motion through the time. The composite structures are modeled using eight-node solid elements. The critical interfaces between layers is represented by special interface elements based on Cohesive Zone Method (CZM). A combined approach considering damage initiation and damage growth phases in a single model is utilized in this method. The linear elastic and linear softening behavior is applied for these interface elements. A stress based failure criterion and damage mechanics approach are used to simulate initiation and propagation of delamination, respectively. The analyses are divided into two main sections involving the validation of computational model and parametric studies. The eight-node brick element is verified without delamination damage. Then, the model with delamination damage is validated by experimental results from literature. The verified model is adapted for the curved laminates and a parametric study is conducted in order to determine the effect of curvature on the delamination damage. Additionally, the effect of element size on delamination damage is discussed.