Session: 01-06-01: Impact, Fatigue, Damage and Fracture of Composite Structures

Paper Number: 106793

106793 - High Resolution Experimental Study of Damage Initiation in Cross-Ply Laminates Using Digital Volume Correlation 

High resolution experimental data that provide insight about the damage mechanisms of carbon fiber reinforced polymer matrix composites (CFRP) is invaluable for the evaluation of progressive failure analysis (PFA) models. A cross ply [90/0/90] single-edge notched specimen loaded in tension is used for this purpose. The initiation of the damage mechanisms was observed using Digital Volume Correlation (DVC) analysis obtained from Computerized Tomography (CT) scans of the specimen at different load levels. This imaging technique allows to visualize any component of the strain field of a specimen at any plane of interest including internal plies. By tracking changes in the strain field distribution of the specimen as the load is increased, the activation of damage modes such as delamination, transverse cracking, and splitting can be inferred.  DVC results are currently being supported by Finite Element simulations and dye-penetrant-enhanced CT scans. A previously developed mechanics model will be discussed to illustrate how the experimental data collected in this study can be used. Nguyen and Waas [1] recently proposed a mesoscale PFA model, referred to as Semi-Discrete Damage Model (SD2M), that uses a cohesive zone method, a smart meshing algorithm, and a separation of failure modes to introduce features that allow to explicitly capture macroscopic matrix cracking and delamination. SD2M offers 2 key advantages, the first one being that it brings in the important phenomena that drive final failure at the microscale, mesoscale, and macroscale together into a single model without resorting to computationally expensive multiscale methods. The other advantage is that using the same meshing algorithm parameters and material properties, it can generate models that will be accurate for different loading scenarios as opposed to other models in the literature where a-priori knowledge of the main cracks that develop in each case is necessary. With a high resolution set of experimental data the internal and external cracking in a specimen for a given loading scenario can be tracked and compared against model predictions to evaluate whether the fidelity of the model as well as scale dependent aspects that are important for computational efficiency are sufficient. Results in support of these issues will be presented.

Ref: [1] M. H. Nguyen and A. M. Waas, "A novel mode-dependent and probabilistic semi-discrete damage model for progressive failure analysis of composite laminates - Part I: Meshing strategy and mixed-mode law," Composites Part C: Open Access 3, 2020.

Presenting Author: J. Fernando Rojas Sanchez University of Michigan

Presenting Author Biography: J. Fernando Rojas Sanchez is a PhD candidate at the University of Michigan in the department of aerospace engineering. His research focuses on progressive failure modeling of composite structures under fatigue loading scenarios. He uses high resolution experimental observations to inspire the development of Finite Element models that accurately capture the initiation and progression of the damage mechanisms that lead to ultimate failure of a composite structure. The experimental inspection techniques he uses in his work include Digital Image Correlation, thermography, Scanning Electron Microscopy, and Computed Tomography imaging. For development of his models, he uses ABAQUS user subroutines and High Performance Computing. Prior to his PhD thesis work, he also investigated the strain rate dependency of composites under impact loading, and the effect of contamination in composite adhesive bonds.

Authors:

J. Fernando Rojas Sanchez University of Michigan
Anthony Waas University of Michigan