Natural frequency changes due to damage in composite beams

Negru, Ionica; Gillich, Gilbert-Rainer; Praisach, Zeno-Iosif; Tufoi, Marius; Gillich, Nicoleta

doi:10.1088/1742-6596/628/1/012091

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…The values of the normalized frequency shift [23] for sample 1 in each group, with respect to the rest of the samples of the same group, are presented in Figure 14. Due to the geometrical variations and high amplitude of vibrations, there is up to 33% frequency change in Group 1 for mode 1, while the other modes show a small frequency shift between the first and the rest of the samples.…”

Section: Normalized Frequency Shift Calculationsmentioning

confidence: 99%

Experimental and Numerical Simulation Study of the Vibration Properties of Thin Copper Films Bonded to FR4 Composite

Azam

Fragoso

2020

Applied Sciences

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Printed circuit boards constitute the basis of most electronic devices and are mainly fabricated of thin copper films bounded to fiber epoxy laminates, such as FR4. Vibrational stress can induce device failure, and hence, studies addressing their modal properties have important applications. In this paper, cantilever samples made of bare copper bounded to FR4 have been studied to analyze, for the first time, the vibration behavior of specimens with different aspect ratios, with and without central holes of different diameters. Natural frequencies and damping ratios were determined experimentally and analytically using a finite element method for four groups of samples with a very good correspondence between both methods. The fundamental resonance frequency of all the specimens was found to be less than 40 Hz and the influence of a central hole was not significant to affect the modal properties.

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Section: Normalized Frequency Shift Calculationsmentioning

confidence: 99%

Experimental and Numerical Simulation Study of the Vibration Properties of Thin Copper Films Bonded to FR4 Composite

Azam

Fragoso

2020

Applied Sciences

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“…However, due to the simple instrumentation and development of new powerful system identification techniques, SHM systems based on the global changes in the vibration characteristics of the structure have gained an increasing worldwide attention in the last years. 6,9–17…”

Section: Introductionmentioning

confidence: 99%

Structural health monitoring for impact damaged composite: a new methodology based on a combination of techniques

Medeiros

Vandepitte

Tita

2017

Structural Health Monitoring

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Advanced aerospace materials, including fibre-reinforced polymer and ceramic matrix composites, are increasingly being used in critical and demanding applications, challenging not only the current damage prediction, detection and quantification methodologies, but also the residual life of the structure. The main objective of this work consists of developing a new methodology based on different techniques to be applied on structural health monitoring system for impacted composite aeronautic structures. For this, it is necessary to identify, and to localise damage, as well as to calculate the severity of the damage and to predict the residual strength of the composite structure. To achieve these goals, the research methodology should consider three methods: (1) vibration-based method, (2) shearography speckle and (3) flexural after impact. Composite plates, made of epoxy resin reinforced by carbon fibre, are evaluated. First, vibration-based method provides frequency response functions to be analysed by a new metric, which is compared in terms of their capability for damage identification and global location. Afterwards, the extension of impact damage is determined using shearography speckle. This technique has demonstrated great potential for damage detection in composite-laminated structures. A flexure after impact test is used to evaluate its limitations and potentialities as a damage-tolerance technique. The residual flexural strength of damaged specimens is evaluated by quasi-static four-point bending test. A new criterion based on a relationship between damage metric from vibration-based method and flexure after impact analysis is presented and discussed. Finally, it discussed the advantages and limitations of this combination of techniques into the context of structural health monitoring systems.

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“…Also, as stated by Negru et al [2015], transversal cracks in composite structures affect their stiffness as well as the natural frequency values. For a given crack, irrespective of its depth, the frequency drop ratio of any two transverse modes is similar (de Assis and ).…”

Section: Natural Frequency-based Methodsmentioning

confidence: 97%

On the use of Modal Test Data in Inverse Problems: Fundamentals and Applications

Gomes¹,

Carneiro²,

S.³

et al. 2022

Fundamental Concepts and Models for the Direct Problem

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In the past few decades, modal testing has become a major technology for determining, improving and optimizing dynamic characteristics of engineering structures in different fields, with emphasys (but not limited to) mechanical, civil, and aeronautical/aerospace engineering. One of the great advantages of using modal tests is related to their experimental practicality. This practical advantage leads to its strong use in inverse methods, or commonly known as inverse modal-based problems. An inverse problem based on modal parameters can be formulated basically using i) natural frequency, ii) damping factor or loss factor and iii) mode shapes. Other metrics can also be used from the composition of these 3 main responses, such as modal strain energy, inverse FRF and many others. Inverse modal-based identification through optimization algorithms are particularly emphasized. The methods discussed here are mainly elaborated by the evaluation of modal data due to the great potential of application. This chapter discusses the use of computational and intelligent techniques for parameter identification using modal responses. The content in this paper aims to help engineers and researchers find a starting point in developing a better solution to their specific structural problems, either by inverse methods, pattern recognition, or intelligent signal processing.

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Natural frequency changes due to damage in composite beams

Cited by 7 publications

References 11 publications

Experimental and Numerical Simulation Study of the Vibration Properties of Thin Copper Films Bonded to FR4 Composite

Experimental and Numerical Simulation Study of the Vibration Properties of Thin Copper Films Bonded to FR4 Composite

Structural health monitoring for impact damaged composite: a new methodology based on a combination of techniques

On the use of Modal Test Data in Inverse Problems: Fundamentals and Applications

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