ACOUSTIC EMISSION FOR IDENTIFICATION OF THE DOMINANT STRESS - - PowerPoint PPT Presentation

▶
acoustic emission for identification of the dominant
SMART_READER_LITE
LIVE PREVIEW

ACOUSTIC EMISSION FOR IDENTIFICATION OF THE DOMINANT STRESS - - PowerPoint PPT Presentation

Jun 07, 2023 27 likes •312 views

ACOUSTIC EMISSION FOR IDENTIFICATION OF THE DOMINANT STRESS COMPONENT IN POLYMER COMPOSITES AT EARLY LOADS 1 ST INTERNATIONAL ELECTRONIC CONFERENCE ON APPLIED SCIENCES Kalliopi-Artemi Kalteremidou, Dimitrios G. Aggelis, Danny Van Hemelrijck and

slide-1
SLIDE 1

1ST INTERNATIONAL ELECTRONIC CONFERENCE ON APPLIED SCIENCES

ACOUSTIC EMISSION FOR IDENTIFICATION OF THE DOMINANT STRESS COMPONENT IN POLYMER COMPOSITES AT EARLY LOADS

Kalliopi-Artemi Kalteremidou, Dimitrios G. Aggelis, Danny Van Hemelrijck and Lincy Pyl

slide-2
SLIDE 2

ASEC 2020 11-2020 | 2

PRESENTATION OUTLINE

  • Introduction
  • Theoretical background
  • Aim of the study
  • Material and testing equipment
  • Experimental results: quasi-static tests
  • Experimental results: incremental loading tests
  • Conclusions
slide-3
SLIDE 3

ASEC 2020 11-2020 | 3

INTRODUCTION

  • Reduction of weight → primary target in

many engineering fields

  • Fibre reinforced polymer composite

materials → promising for reducing weight and CO2 emissions

  • Main advantage: lightweight

materials

  • Carbon Fibre Reinforced Polymer

(CFRP): extra advantages like exceptional durability, application flexibility, corrosion resistance

slide-4
SLIDE 4

ASEC 2020 11-2020 | 4

THEORETICAL BACKGROUND

  • Composites: anisotropic materials
  • Multiaxial stresses occur in the composite laminas even under uniaxial loading

due to different fibre orientations (internal multiaxiality)

slide-5
SLIDE 5

ASEC 2020 11-2020 | 5

THEORETICAL BACKGROUND

  • Damage sequence in composites is complicated (interfacial debondings, matrix

cracks, delaminations, fibre breaks)

  • Even more complicated when multiaxial stresses occur → can lead to different

mechanical response, influencing the structural integrity of the laminate

slide-6
SLIDE 6

ASEC 2020 11-2020 | 6

THEORETICAL BACKGROUND

  • Multiaxiality not extensively studied in literature
  • Monitoring of damage with respect to different multiaxial stresses in lab

conditions necessary → predictive tool for real applications

  • Prediction of stress states and identification of dominant stresses essential

even from early loading stages

  • Acoustic Emission (AE) CAN be used to give solutions to these problems!
slide-7
SLIDE 7

ASEC 2020 11-2020 | 7

THEORETICAL BACKGROUND

  • Acoustic Emission: characterisation of

damage of materials by interpreting the generated elastic waves

  • Commonly applied in composite materials for

investigations in the time domain and frequency domain

  • Clustering approaches have been proposed
  • No link to multiaxial stress states
slide-8
SLIDE 8

ASEC 2020 11-2020 | 8

THEORETICAL BACKGROUND

  • Feature analysis: selection of the most

appropriate signal features

  • It has been used so far for damage mode

classification

  • Rise Time (RT) and Average Frequency (AF)

among the most popular

slide-9
SLIDE 9

ASEC 2020 11-2020 | 9

THEORETICAL BACKGROUND

  • Kaiser effect: the absence of detectable AE

until the previously maximum applied stress is exceeded

  • Felicity effect: the presence of detectable AE at

stress levels below those previously applied → described by the Felicity Ratio (FR)

  • 𝐺𝑆=

stress level at which AE resumes during a loading step maximum stress applied at the previous loading step

  • The Calm Ratio (CR) can be another damage

parameter

  • 𝐷𝑆=

AE activity during the unloading part of the cycle AE activity over the total cycle

slide-10
SLIDE 10

ASEC 2020 11-2020 | 10

AIM OF THE STUDY

  • To verify that AE can distinguish the different damage modes under

multiaxial stress states

  • Can AE indicate the dominant stress/strain component within the composite

laminate from early loading stages?

  • Which AE parameters are the most effective for such stress indications?
slide-11
SLIDE 11

ASEC 2020 11-2020 | 11

MATERIAL AND TESTING EQUIPMENT

  • To introduce different multiaxial stress

states → two angle-ply carbon/epoxy laminates were tested

  • Based on the multiaxiality ratio

λ12=σ6/σ2

Loading direction

[0o/30o]2s: λ12=2.02 [0o/60o]2s: λ12=0.64 [0o/30o]2s: dominant shear stresses [0o/60o]2s: dominant transverse stresses

slide-12
SLIDE 12

ASEC 2020 11-2020 | 12

MATERIAL AND TESTING EQUIPMENT

  • Continuous static tests and interrupted tests

displacement controlled at 1 mm/min rate

  • Two Pico sensors for the AE acquisition → 35 dB

threshold

  • Digital Image Correlation (DIC) for strain

measurements

  • Through-the-thickness free-edge damage

monitoring at regular steps with optical microscopy

slide-13
SLIDE 13

ASEC 2020 11-2020 | 13

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

[0o/90o]2s laminates Tensile failure Shear failure

slide-14
SLIDE 14

ASEC 2020 11-2020 | 14

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

[0o/30o]2s laminates [0o/60o]2s laminates

slide-15
SLIDE 15

ASEC 2020 11-2020 | 15

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

AE onset

slide-16
SLIDE 16

ASEC 2020 11-2020 | 16

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

Appearance of delaminations

slide-17
SLIDE 17

ASEC 2020 11-2020 | 17

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

Appearance of matrix cracking Appearance of delaminations

slide-18
SLIDE 18

ASEC 2020 11-2020 | 18

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

Dominant shear stresses Dominant transverse stresses

slide-19
SLIDE 19

ASEC 2020 11-2020 | 19

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

slide-20
SLIDE 20

ASEC 2020 11-2020 | 20

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

slide-21
SLIDE 21

ASEC 2020 11-2020 | 21

EXPERIMENTAL RESULTS: QUASI-STATIC TESTS

slide-22
SLIDE 22

ASEC 2020 11-2020 | 22

EXPERIMENTAL RESULTS: INCREMENTAL LOADING TESTS

slide-23
SLIDE 23

ASEC 2020 11-2020 | 23

EXPERIMENTAL RESULTS: INCREMENTAL LOADING TESTS

slide-24
SLIDE 24

ASEC 2020 11-2020 | 24

EXPERIMENTAL RESULTS: INCREMENTAL LOADING TESTS

slide-25
SLIDE 25

ASEC 2020 11-2020 | 25

EXPERIMENTAL RESULTS: INCREMENTAL LOADING TESTS

Dominant shear stresses Dominant transverse stresses

slide-26
SLIDE 26

ASEC 2020 11-2020 | 26

EXPERIMENTAL RESULTS: INCREMENTAL LOADING TESTS

slide-27
SLIDE 27

ASEC 2020 11-2020 | 27

CONCLUSIONS

  • AE can be effectively used for the identification of damage in polymer composites
  • Significant differences from early loading stages allowing indications of the dominant stress

component

  • RT good indicator for the identification of damage modes and the transition between modes
  • Low RT linked to tensile related phenomena and high RT to shear related phenomena
  • Continuous increase of RT when shear is dominant
  • FR is characterised by reduction when delaminations occur → can be used as damage mode

transition indicator

  • FR appears lower values when shear is dominant → FR is not only material dependent, but also

stress state dependent → can be used as stress state indicator

  • Higher CR values for shear dominated laminates even from early loads → can indicate the

dominant stress component and the consequent deterioration

slide-28
SLIDE 28

THANK YOU

The work leading to this publication has been partially funded by the SBO project “M3Strength”, which fits in the MacroModelMat (M3) research program, coordinated by Siemens (Siemens Digital Industries Software, Belgium) and funded by SIM (Strategic Initiative Materials in Flanders) and VLAIO (Flanders Innovation & Entrepreneurship Agency). The authors gratefully acknowledge the material suppliers Mitsubishi Chemical Corporation and Honda R&D Co., Ltd. and would like to thank the financial support of the Fonds Wetenschappelijk Onderzoek (FWO) research program “Multi-scale modelling and characterisation of fatigue damage in unidirectionally reinforced polymer composites under multiaxial and variable-amplitude loading” (G.0090.15).