Modal Strain Energy-Based Debonding Assessment of Sandwich Panels Using a Linear Approximation with Maximum Entropy

Viviana Meruane,Alejandro Ortiz-Bernardin,Matias Lasen

doi:10.3390/e19110619

Viviana Meruane, Alejandro Ortiz-Bernardin + Show 1 more

Open Access

https://doi.org/10.3390/e19110619

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Journal: Entropy	Publication Date: Nov 17, 2017
Citations: 7	License type: CC BY 4.0

Affiliation: University of Chile

Abstract

Sandwich structures are very attractive due to their high strength at a minimum weight, and, therefore, there has been a rapid increase in their applications. Nevertheless, these structures may present imperfect bonding or debonding between the skins and core as a result of manufacturing defects or impact loads, degrading their mechanical properties. To improve both the safety and functionality of these systems, structural damage assessment methodologies can be implemented. This article presents a damage assessment algorithm to localize and quantify debonds in sandwich panels. The proposed algorithm uses damage indices derived from the modal strain energy method and a linear approximation with a maximum entropy algorithm. Full-field vibration measurements of the panels were acquired using a high-speed 3D digital image correlation (DIC) system. Since the number of damage indices per panel is too large to be used directly in a regression algorithm, reprocessing of the data using principal component analysis (PCA) and kernel PCA has been performed. The results demonstrate that the proposed methodology accurately identifies debonding in composite panels.

Highlights

Sandwich structures typically consist of thin face sheets or skins and a lightweight thicker core, which is sandwiched between the skins to obtain a structure of superior bending stiffness
Damage, debonding is restricted to the skin skin that that is is measured measured during duringexperiments
A damage assessment algorithm that uses damage indices derived from the modal strain energy method andassessment a linear approximation withuses maximum has been implemented to

Summary

Introduction

Sandwich structures typically consist of thin face sheets or skins and a lightweight thicker core, which is sandwiched between the skins to obtain a structure of superior bending stiffness. The branches of trees or the bones in skeletons are examples of sandwich structures with foam-like core materials. The high stiffness and low weight of sandwich structures make them attractive in applications where weight reduction is critical. The applications of sandwich structures have grown rapidly in recent years, for example in satellites, spacecraft, aircraft, ships, automobiles, rail cars, wind energy systems, and bridge construction [1]. Notwithstanding, these structures may present imperfect bonding or debonding between the skins and core as a result of manufacturing defects or impact loads. In aircraft design it is fundamental to make a structure as light as possible without sacrificing strength, sandwich structures remain limited to secondary (non-critical) components [2]

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