# Damage Detection Using d15 Piezoelectric Sensors in a Laminate Beam Undergoing Three-Point Bending

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## Abstract

**:**

## 1. Introduction

## 2. Theoretical Background

#### 2.1. Shear-Mode (d15) PZTs

#### 2.2. Damage Index

## 3. Experiment

#### 3.1. Specimen Design and Fabrication

#### 3.2. Quasi-Static Three-Point Bending

_{fn}is the combined flexural rigidity of the laminate specimen at nth loading cycle, L is the length between loading supports, F is the mid-span load at nth loading cycle, and δ is the mid-span deflection at nth loading cycle. The stress induced in the laminate specimen can be calculated as [34]:

#### 3.3. Experimental Method

- Apply an increasing quasi-static load on the specimen until mid-span deflection reaches δ
_{n}, then remove the applied mid-span load. - At no-load condition state, actuate d15 PZTs with a voltage frequency sweep (V
_{i}) from 200 kHz to 1600 kHz by measuring the voltage (V_{o}) across a sensing resistor (R_{s}= 100 Ω) and the PZT element, then calculate the impedance, $Z={R}_{s}\left({V}_{i}/{V}_{o}\right)$. - Apply fast Fourier transform method and band-pass filter to the harmonic signals and identify the first resonance frequency, ${f}_{1}^{EM}$, for each d15 PZT.
- Continue the test if the difference between the baseline resonant peak and the measured resonant is less than α, which is set as 1% of the baseline resonant peak.
- Perform ultrasonic inspection by actuating bondline-embedded d15 PZTs. The excitation signal shown in Figure 6 is a five-peak sine signal centered at 30 kHz and modulated by a Hann window, $w(n)=0.5\left[1-\mathrm{cos}(2\pi n/N)\right],0\le \mathrm{n}\le \mathrm{N}$, where $N+1$ is the length of the window.
- Denoise senor signals using discrete wavelet transform with Coiflet wavelet performed at level six wavelet decomposition and applying the universal threshold $\sqrt{2\mathrm{ln}(.)}$, to the wavelet coefficients.
- Determine the maximum voltage, V
_{max}of the first arrival in sensor signals and the phase shift, ϕ_{max}with respect to baseline signals. - Calculate damage index values based on PCC and NSE methods using Equations (6) and (7), respectively.
- Repeat loading the specimen at a higher mid-span deflection by β increment, 0.1 mm herein.
- Stop the test when mid-span deflection reaches δ
_{m}that is calculated based on flexural rigidity of the laminate specimen.

## 4. Results and Discussion

#### 4.1. Wave Propagation Analysis

#### 4.2. Joint Degradation

^{2}at which a mixed-mode (flexural) crack developed and was located 21 mm from the applied load. The mixed-mode crack was formed at about 45 degrees plane as result of the adhesive layer between loading supports being subjected to both normal and transverse shear stresses. Residual stresses that accompany plastic deformation in localized areas such as at the applied load or at the loading supports can modulate the propagating waves in the laminate, therefore distortions in received signals prior to the flexural cracking are expected to reflect the effects of plastic deformation and joint defects.

^{6}N/mm

^{2}for the deflection range between 0–0.9 mm using Equation (8). This was followed by a significant drop in the flexural strength by more than 65%. By increasing mid-span deflection from 1 mm to 3.3 mm, its flexural rigidity significantly reduced and continuously decreased beyond 1 mm mid-deflection. Furthermore, flexural rigidity provides an indication of damage severity, particularly disbonding among the laminate layers. The three-point bending test was stopped when flexural rigidity reached almost zero.

#### 4.3. Electromechanical Impedance

#### 4.4. Ultrasonic Inspection

#### 4.5. Influence of Preload Condition

^{2}. The applied load at mid-span produces normal stresses across the thickness between loading supports, thus the propagating waves are anticipated to be modulated and be reflected on the received signals. However, this resulting distortion from a small applied load is expected to have negligible effect as compared to the effect of damage on the propagating waves. The results strongly suggest that the applied load on the specimen caused a geometric change to the bondline damage resulting in significant distortion to the propagating waves. As previously discussed in Section 4.4, the mixed-mode crack was observed and fully developed in the bondline at 0.9 mm mid-span deflection, and that was followed by plastic deformation causing the crack to remain open resulting in low distortion in received signals over the range 1–2.3 mm mid-span deflection as shown in Figure 11. Therefore, in the preload condition at 1.3 mm mid-span deflection, the applied load is anticipated to open the mixed-mode crack and disbonds while the antisymmetric waves transmitted through the bondline cause higher scattering of the propagating waves.

## 5. Conclusions

## 6. Future Work

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Structural Integrity and Durability of Advanced Composites: Innovative Modelling Methods and Intelligent Design; Beaumont, P.W.R.; Soutis, C.; Hodzic, A. (Eds.) Woodhead Publishing: Sawston, UK; Cambridge, UK, 2015; ISBN 978-0-08-100137-0. [Google Scholar]
- Dugnani, R.; Zhuang, Y.; Kopsaftopoulos, F.; Chang, F.-K. Adhesive bond-line degradation detection via a cross-correlation electromechanical impedance–based approach. Struct. Health Monit.
**2016**, 15, 650–667. [Google Scholar] [CrossRef] - Zhuang, Y.; Li, Y.-H.; Kopsaftopoulos, F.; Chang, F.-K. A self-diagnostic adhesive for monitoring bonded joints in aerospace structures. In Proceedings of the Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, Las Vegas, NV, USA, 20 April 2016. [Google Scholar]
- Nagy, P.B. Ultrasonic detection of kissing bonds at adhesive interfaces. J. Adhes. Sci. Technol.
**1991**, 5, 619–630. [Google Scholar] [CrossRef] - Kundu, T.; Maji, A.; Ghosh, T.; Maslov, K. Detection of kissing bonds by Lamb waves. Ultrasonics
**1998**, 35, 573–580. [Google Scholar] [CrossRef] - Ramadas, C.; Balasubramaniam, K.; Joshi, M.; Krishnamurthy, C.V. Numerical and experimental studies on propagation of A0mode in a composite plate containing semi-infinite delamination: Observation of turning modes. Compos. Struct.
**2011**, 93, 1929–1938. [Google Scholar] [CrossRef] - Masserey, B.; Raemy, C.; Fromme, P. High-frequency guided ultrasonic waves for hidden defect detection in multi-layered aircraft structures. Ultrasonics
**2014**, 54, 1720–1728. [Google Scholar] [CrossRef] [PubMed][Green Version] - Zhang, K.; Zhou, Z. Quantitative characterization of disbonds in multilayered bonded composites using laser ultrasonic guided waves. NDT E Int.
**2018**, 97, 42–50. [Google Scholar] [CrossRef] - Guo, N.; Cawley, P. Lamb wave propagation in composite laminates and its relationship with acousto-ultrasonics. NDT E Int.
**1993**, 26, 75–84. [Google Scholar] [CrossRef] - Ramadas, C.; Balasubramaniam, K.; Joshi, M.; Krishnamurthy, C.V. Characterisation of rectangular type delaminations in composite laminates through B- and D-scan images generated using Lamb waves. NDT E Int.
**2011**, 44, 281–289. [Google Scholar] [CrossRef] - Altammar, H.; Kaul, S.; Dhingra, A.K. Use of wavelets for damage diagnostics in truss structures. Int. J. Struct. Integr.
**2017**, 8, 373–391. [Google Scholar] [CrossRef] - Mix, P.E. Introduction to Nondestructive Testing: A Training Guide; John Wiley & Sons: Hoboken, NJ, USA, 2005; ISBN 13 978-0-471-42029-3. [Google Scholar]
- Hellier, C.J. Handbook of Nondestructive Evaluation; McGraw-Hill Education: New York, NY, USA, 2012; Volume 69, ISBN 007139947X. [Google Scholar]
- Gulizzi, V.; Rizzo, P.; Milazzo, A. Electromechanical impedance method for the health monitoring of bonded joints: Numerical modelling and experimental validation. SDHM Struct. Durab. Health Monit.
**2014**, 10, 19–54. [Google Scholar] - Malinowski, P.; Wandowski, T.; Ostachowicz, W. The use of electromechanical impedance conductance signatures for detection of weak adhesive bonds of carbon fibre–reinforced polymer. Struct. Health Monit.
**2015**, 14, 332–344. [Google Scholar] [CrossRef] - Altammar, H.; Dhingra, A.; Salowitz, N. Initial study of internally embedded shear-mode piezoelectric transducers for the detection of joint defects in laminate structures. J. Intell. Mater. Syst. Struct.
**2019**, 30, 2314–2330. [Google Scholar] [CrossRef] - Dı́az Valdés, S.H.; Soutis, C.; Dı́az Valdés, S.H.; Soutis, C.; Diaz Vald, S.H.; Soutis, C. Real-time nondestructive evaluation of fiber composite laminates using low-frequency Lamb waves. J. Acoust. Soc. Am.
**2002**, 111, 2026–2033. [Google Scholar] [CrossRef] [PubMed] - Osmont, D.; Devillers, D.; Taillade, F. Health Monitoring of Sandwich Plates Based on the Analysis of the Interaction of Lamb Waves with Damages. Smart Struct. Integr. Syst.
**2001**, 4327, 290–301. [Google Scholar] - Wilcox, P.D.; Lee, C.K.; Scholey, J.J.; Friswell, M.I.; Wisnom, M.R.; Drinkwater, B.W. Quantitative structural health monitoring using acoustic emission. SPIE Conf. Proc.
**2006**, 6173, 61731K. [Google Scholar] - Pau, A.; Achillopoulou, D.V.; Vestroni, F. Scattering of guided shear waves in plates with discontinuities. NDT E Int.
**2016**, 84, 67–75. [Google Scholar] [CrossRef] - Kamal, A.; Giurgiutiu, V. Shear horizontal wave excitation and reception with shear horizontal piezoelectric wafer active sensor (SH-PWAS). Smart Mater. Struct.
**2014**, 23, 085019. [Google Scholar] [CrossRef] - Zhou, W.; Li, H.; Yuan, F.G. Guided wave generation, sensing and damage detection using in-plane shear piezoelectric wafers. Smart Mater. Struct.
**2013**, 23, 015014. [Google Scholar] [CrossRef] - Hou, S.; Zhang, H.B.; Ou, J.P. A PZT-based smart aggregate for seismic shear stress monitoring. Smart Mater. Struct.
**2013**, 22, 065012. [Google Scholar] [CrossRef] - Zhou, W.; Li, H.; Yuan, F.G. Fundamental understanding of wave generation and reception using d36 type piezoelectric transducers. Ultrasonics
**2015**, 57, 135–143. [Google Scholar] [CrossRef] [PubMed] - Altammar, H.; Dhingra, A.; Salowitz, N. Ultrasonic Sensing and Actuation in Laminate Structures Using Bondline-Embedded d35 Piezoelectric Sensors. Sensors
**2018**, 18, 21. [Google Scholar] [CrossRef] [PubMed] - Köhler, B.; Gaul, T.; Lieske, U.; Schubert, F. Shear horizontal piezoelectric fiber patch transducers (SH-PFP) for guided elastic wave applications. NDT E Int.
**2016**, 82, 1–12. [Google Scholar] [CrossRef] - APC International, Ltd. Piezoelectric Ceramics: Principles and Applications, 1st ed.; APC International: Mackeyville, PA, USA, 2002; ISBN 0615565034. [Google Scholar]
- IEEE Standard on Piezoelectricity “ANSI/IEEE Std 176-1987”; The Institute of Electrical and Electronics Engineers Inc.: Piscataway, NJ, USA, 1988; Volume 74.
- Giurgiutiu, V. Structural Health Monitoring With Piezoelectric Wafer Active Sensors, 2nd ed.; Elsevier Inc.: London, UK, 2014; ISBN 9780124186910. [Google Scholar]
- Wu, Z.; Qing, X.P.; Ghosh, K.; Karbhari, V.M.; Chang, F.-K. Health monitoring of bonded composite repair in bridge rehabilitation. Smart Mater. Struct.
**2008**, 17, 045014. [Google Scholar] [CrossRef] - Torkamani, S.; Roy, S.; Barkey, M.E.; Sazonov, E.; Burkett, S.; Kotru, S. A novel damage index for damage identification using guided waves with application in laminated composites. Smart Mater. Struct.
**2014**, 23, 095015. [Google Scholar] [CrossRef] - Tseng, K.K.-H.; Naidu, A.S.K. Non-parametric damage detection and characterization using smart piezoceramic material. Smart Mater. Struct.
**2002**, 11, 317–329. [Google Scholar] [CrossRef] - Methods, S.T. ASTM E 290—Standard Test Methods for Bend Testing of Material for Ductility. Current
**1998**, 3, 1–10. [Google Scholar] - Dowling, N.E. Mechanical Behavior of Materials, 4th ed.; Pearson Education, Inc.: Hoboken, NJ, USA, 2013; ISBN 9780131395060. [Google Scholar]
- Broda, D.; Staszewski, W.J.; Martowicz, A.; Uhl, T.; Silberschmidt, V.V. Modelling of nonlinear crack–wave interactions for damage detection based on ultrasound—A review. J. Sound Vib.
**2014**, 333, 1097–1118. [Google Scholar] [CrossRef] - Alleyne, D.N.; Cawley, P. The Interaction of Lamb Waves with Defects. IEEE Trans. Ultrason. Ferroelectr. Freq. Control
**1992**, 39, 381–397. [Google Scholar] [CrossRef] [PubMed] - Greve, D.W.; Tyson, N.; Oppenheim, I.J. Interaction of defects with Lamb waves in complex geometries. Proc. IEEE Ultrason. Symp.
**2005**, 1, 297–300. [Google Scholar] - Altammar, H.; Dhingra, A.; Salowitz, N. Investigating the Feasibility of Ultrasonic Shear Actuation for Evaluation of Adhesive Joints in Multilayered Structures: FE Simulation. In Proceedings of the ASNT Annual Conference, Nashville, Tennessee, 30 October–2 November 2017; pp. 25–34. [Google Scholar]
- Salowitz, N.P.; Guo, Z.; Kim, S.J.; Li, Y.H.; Lanzara, G.; Chang, F.K. Microfabricated expandable sensor networks for intelligent sensing materials. IEEE Sens. J.
**2014**, 14, 2138–2144. [Google Scholar] [CrossRef] - Salowitz, N.; Guo, Z.; Li, Y.H.; Kim, K.; Lanzara, G.; Chang, F.K. Bio-inspired stretchable network-based intelligent composites. J. Compos. Mater.
**2013**, 47, 97–105. [Google Scholar] [CrossRef] - Chalioris, C.E.; Papadopoulos, N.A.; Angeli, G.M.; Karayannis, C.G.; Liolios, A.A.; Providakis, C.P. Damage Evaluation in Shear-Critical Reinforced Concrete Beam using Piezoelectric Transducers as Smart Aggregates. Open Eng.
**2015**, 5, 373–384. [Google Scholar] [CrossRef]

**Figure 1.**Schematic of a d15 piezoelectric transducer with fundamental wave modes depicted in the direction of wave propagation.

**Figure 2.**Schematic diagram of laminate specimen with two d15 lead zirconate titanate (PZT) transducers (15 mm × 15 mm × 1 mm) embedded in the bondline and d31 PZT sensor (6 mm × 0.25 mm) mounted on the surface of the bottom aluminum sheet.

**Figure 3.**Experimental setup of health monitoring experiment and magnified view of laminate specimen under three-point bending test.

**Figure 4.**Laminate specimen under a quasi-static three-point bending force applied cyclically at mid-span.

**Figure 5.**Flowchart of ultrasonic health monitoring experiment for a laminate specimen with surface-mounted and bondline-embedded PZT transducers.

**Figure 6.**Waveform signals obtained from laminate specimen with d31 PZT and d15 PZT transducers for wave propagation paths: (

**a**) PZT-1 → PZT-2 and (

**b**) PZT-1 → PZT-3.

**Figure 7.**(

**a**) Load–deflection response of laminate specimen under three-point bending test at: (

**b**) pristine state; (

**c**) flexural cracking at 0.9 mm mid-span deflection; and (

**d**) disbonding at 3.3 mm mid-span deflection.

**Figure 8.**Electromechanical impedance (EMI) response of bondline-embedded d15 PZTs at the pristine state with a frequency range containing the first EM resonance for: (

**a**) d15 PZT-1 and (

**b**) d15 PZT-2.

**Figure 9.**Comparison of waveform signals collected from bondline-embedded d15 PZT and surface mounted d31 PZT sensors at 1 mm deflection (left column) and 3.3 mm deflection (right column) for wave propagation paths: (

**a**,

**b**) PZT-1 → PZT-2 and (

**c**,

**d**) PZT-1 → PZT-3.

**Figure 10.**Maximum voltage amplitude (left column) and phase shift (right column) from waveform signals collected from bondline-embedded d15 PZT and surface mounted d31 PZT sensors for wave propagation paths: (

**a**,

**b**) PZT-1 → PZT-2; (

**c**,

**d**) PZT-1 → PZT-3; and (

**e**,

**f**) PZT-2 → PZT-1.

**Figure 11.**Damage index values based on Pearson correlation coefficient (PCC) and normalized signal energy (NSE) methods calculated for the first arrival of sensor signals received by: (

**a**) d15 PZT-2; (

**b**) d31 PZT-3; and (

**c**) d15 PZT-1.

**Figure 13.**Comparison of voltage signals from laminate specimen at no-preload condition (left column) and 50 N mid-span preload (right column) at 1.3 mm three-point loading cycle: (

**a**,

**b**) d15 PZT-2 sensor and (

**c**,

**d**) d31 PZT-3 sensor.

**Figure 14.**Scattered signals from laminate specimen at no-preload condition (left column) and 50 N mid-span preload (right column) at 1.3 mm three-point loading cycle: (

**a**,

**b**) d15 PZT-2 sensor and (

**c**,

**d**) d31 PZT-3 sensor.

**Table 1.**Material properties of the shear-mode piezoelectric transducer, Hysol EA9394, and Aluminum 6061 [16].

Property | Unit | Symbol | PZT-5A | Adhesive | Aluminum |
---|---|---|---|---|---|

Young’s Modulus | 10^{9} N/m^{2} | Y_{11} | 61.0 | 4.24 | 68.9 |

10^{9} N/m^{2} | Y_{33} | 53.2 | 4.24 | 68.9 | |

Shear’s Modulus | 10^{9} N/m^{2} | G_{12} | 22.6 | 1.46 | 25.9 |

10^{9} N/m^{2} | G_{13} | 10.5 | 1.46 | 25.9 | |

Poisson’s ratio | 1 | v_{12} | 0.35 | 0.45 | 0.33 |

1 | v_{13} | 0.44 | 0.45 | 0.33 | |

Density | kg/m^{3} | ρ | 7600 | 1360 | 2700 |

Dielectric permittivity | 8.854 µF/m | ε_{11} | 1851 | ------ | ------ |

8.854 µF/m | ε_{13} | 1581 | ------ | ------ | |

Piezoelectric coefficient | 10^{−12} m/V | d_{15} | 584 | ------ | ------ |

10^{−12} m/V | d_{31} | −171 | ------ | ------ | |

10^{−12} m/V | d_{33} | 374 | ------ | ------ |

**Table 2.**Summary of wave propagation results including time of flight (ToF) and group velocity for waveform signals from bondline-embedded d15 and surface-mounted d31 PZT sensors at no-load condition.

Wave Propagation Path | Time of Flight (μs) | Group Velocity (m/s) |
---|---|---|

PZT-1 → PZT-2 | 116.6 | 1157.8 |

PZT-1 → PZT-3 | 118.1 | 1143.1 |

PZT-2 → PZT-1 | 116.4 | 1159.8 |

**Table 3.**Damage indices of PCC and NSE for signals obtained from d15 PZT-2 and d31 PZT-3 at 0 N (no-preload condition) and at 50 N preload applied on the specimen at 1.3 mm three-point loading cycle.

Wave Propagation Path | 0 N | 50 N | ||
---|---|---|---|---|

PCC | NSE | PCC | NSE | |

PZT-1 → PZT-2 | 0.5644 | 0.1790 | 1.2886 | 0.6947 |

PZT-1 → PZT-3 | 0.5398 | 0.1657 | 1.1829 | 0.6724 |

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**MDPI and ACS Style**

Altammar, H.; Dhingra, A.; Salowitz, N. Damage Detection Using d15 Piezoelectric Sensors in a Laminate Beam Undergoing Three-Point Bending. *Actuators* **2019**, *8*, 70.
https://doi.org/10.3390/act8040070

**AMA Style**

Altammar H, Dhingra A, Salowitz N. Damage Detection Using d15 Piezoelectric Sensors in a Laminate Beam Undergoing Three-Point Bending. *Actuators*. 2019; 8(4):70.
https://doi.org/10.3390/act8040070

**Chicago/Turabian Style**

Altammar, Hussain, Anoop Dhingra, and Nathan Salowitz. 2019. "Damage Detection Using d15 Piezoelectric Sensors in a Laminate Beam Undergoing Three-Point Bending" *Actuators* 8, no. 4: 70.
https://doi.org/10.3390/act8040070