Professor Vassilis KOSTOPOULOS is the director of Applied Mechanics & Vibrations Lab., in the Dept. of Mechanical Engineering & Aeronautics, University of Patras AML/UPAT). He has a 30 year of experience in the field of composite and aerospace structures, more than 195 journal publications, more than 250 conference presentations, 4 books in the field of composites, 7 patents (3 EPO, 3 National and 1 US). Prof. Kostopoulos has extensive experience in research projects, having been the Principal Investigator for more than 40 European and more than 10 large national projects. For the last 5 years he holds the position of national delegate of Greece in the Advisory Council for Aerospace Research in Europe (ACARE) and he is vice chairman of the SRG in EU-JU-Clean Sky 2.

His research interests lie in the fields of Design, Analysis and Optimization of Composite Structures, Multi-scale analysis of nano modified structural composites, Non-Destructive Inspection & Evaluation of Engineering Structures, Structural Health Monitoring, Nano-augmentation, Nano-engineering and Nano-design of structural composite materials, Fracture and Fatigue of Composites Materials and Structures, high strain rate behavior of composites, Blast behavior of Structures, Eco-design of composite structures, Natural fibers/green resin composites, Life cycle analysis of composite structures, Reuse and recycling of composites.

He has been the main Supervisor of 29 completed PhD theses. His work has received more than 3780 citations and has an H-index 34.

Title

An Innovative Material Model Calibration Procedure for Enhancing the Fidelity of Numerical Solution in the Case of Impact Loading of Composites

Abstract

The numerical prediction of impact induced damage to composite materials and the subsequent residual strength under compression loading continues to be a challenging task. The current study proposes an innovative material model calibration procedure to approximate the optimal combination of material model parameters that represent the experimental response of Cycom 977-2 material.

The optimization algorithm is based on the comparison of the numerical force-strain or force-displacement curves with the corresponding experimental ones and includes the most common quasi-static material characterization tests. For minimizing the parameters combinations, the calibration process was divided into two stages. The first stage includes the in-plane characterization tests (Tension 0o & 90o, Compression 0o & 90o, Shear and Open-Hole Tension test) for calibration of orthotropic damage material model.

Whereas the second one consists of the mode I and mode II interlaminar fracture tests as well as the short beam shear test and targets to cohesive model calibration.

For validation of proposed methodology, low and high velocity impact tests at the energy level of 30 J were carried-out and simulated. Afterwards, the damaged specimens were tested to compression loading according to AITM 1-0010 standard.

The numerical contact force-time curve, the time history of projectile kinetic energy as well as the compression after impact maximum force are correlated with the experimentally derived results. Finally, proposals are provided for further enhancement of numerical results.