scholarly journals Impact Damage Detection in Patch-Repaired CFRP Laminates Using Nonlinear Lamb Waves

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 219
Author(s):  
Zhenhua Yin ◽  
Cheng Li ◽  
Ying Tie ◽  
Yuechen Duan
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Detection System ◽  
Impact Damage ◽  
Impact Resistance ◽  
Numerical Procedure ◽  
Low Velocity Impact ◽  
Patch Repair ◽  
Low Velocity ◽  
Cfrp Laminates

Carbon fiber-reinforced polymer (CFRP) laminates, a key composite material, are widely used in aircraft structures and are susceptible to low-velocity impact (LVI) damage from bird strikes, lightning strikes, hail impacts and other situations. Therefore, finding a method that repairs the damaged structure and detects the effect of these repairs under LVI is a very important goal. In this work, the repair effect of LVI damage in CFRP laminates repaired with patches of various sizes is investigated via experimental and numerical nonlinear Lamb wave analyses. An integrated numerical procedure that combines LVI with nonlinear Lamb wave detection is developed to predict the nonlinear Lamb wave behavior in LVI-damaged patch-repaired CFRP laminates. The CFRP laminate damage in the nonlinear Lamb wave simulation is evaluated based on relative acoustic nonlinearity parameters (RANPs). As a result, the integrated numerical procedure is validated with drop-weight impact tests and RAM-5000 SNAP nonlinear ultrasonic detection system. An optimal patch design is established via interpolation to optimize the absorbed energy, delamination surface area, second RANP and third RANP with different patch repair sizes. These parameters exhibit consistent curve fitting trends, indicating that they can be used as important indicators of impact damage. The optimal circular patch design with a radius of 2.5 r has better impact resistance behavior and repair performance.

A Compensation Method for Environmental Influences on Passive Lamb Wave Based Impact Evaluation for CFRP

2013 ◽  
Vol 569-570 ◽  
pp. 1265-1272 ◽  
Author(s):  
Konstantin Jonas Schubert ◽  
Axel Siegfried Herrmann
Keyword(s):  
Lamb Wave ◽  
Composite Structures ◽  
Lamb Waves ◽  
Detection System ◽  
Main Idea ◽  
Impact Event ◽  
Active System ◽  
Low Velocity ◽  
Temperature Changes ◽  
The Impact

One of the largest issues remaining on the way to in situ Structural Health Monitoring of composite structures using Lamb waves is the impact that non-damaging factors like temperature changes and humidity absorption have on most measurement strategies. While some of these tasks have been successfully conquered, others, especially related to slowly developing influences like humidity absorption or mechanical ageing, remain challenging. In this paper, a method to approach this problem for a Lamb-wave based passive impact detection system is presented. Passive approaches use the waves generated by the impact event itself to both localize said event and evaluate whether it was large enough to damage the structure. For this, the impacts energy has to be estimated from sensors detecting the Lamb waves. The problem provided by changing conditions within the material is that the locally measurable wave amplitude due to an impact event of a certain energy is altered if the material properties change. This might happen due to temperature changes, mechanical loads, humidity absorption, fluid loads and other factors. The main idea of the presented approach is to mix a passive and an active system. Piezoelectric elements are used to generate Lamb waves to obtain the attenuation coefficients of the material before and after hot/wet-conditioning. These coefficients are then used to estimate the impact energy from passive sensor responses. Both the approach and experimental validation performed with low velocity impacts from an impact hammer are presented to show the ability to correctly calculate impact forces after conditioning.

Structural Health Monitoring of Composite Structures Using Guided Lamb Waves

2006 ◽  
Vol 321-323 ◽  
pp. 759-764 ◽  
Author(s):  
Krishnan Balasubramaniam ◽  
B.V. Soma Sekhar ◽  
J. Vishnu Vardan ◽  
C.V. Krishnamurthy
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Composite Structures ◽  
Lamb Waves ◽  
Impact Damage ◽  
Composite Plates ◽  
Structural Features ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Structural Health

Structural Health Monitoring (SHM) of aircrafts is of great relevance in the present age aircraft industry. The present study demonstrates three techniques that have the potential for the SHM of multi-layered composite structures. The first technique is based on multi-transmitter-multireceiver (MTMR) technique with tomographic methods used for data reconstruction. In the MTMR, the possibility of SHM using algebraic reconstruction techniques (ART) for tomographic imaging with Lamb wave data measured in realistic materials is examined. Defects (through holes and low velocity impact delaminations) were synthetic and have been chosen to simulate impact damage in composite plates. The second technique is a single-transmitter-multi-receiver (STMR) technique that is more compact and uses reconstruction techniques that are analogous to synthetic aperture techniques. The reconstruction algorithm uses summation of the phase shifted signals to image the location of defects, portions of the plate edges, and any reflectors from inherent structural features of the component. The third technique involves a linear array of sensors across a stiffener for the detection of disbanded regions.

Damage Index Comparison for a Composite Stiffened Panel Using Lamb Wave

2007 ◽  
Vol 26-28 ◽  
pp. 1265-1268 ◽  
Author(s):  
Chan Yik Park
Keyword(s):  
Lead Zirconate Titanate ◽  
Lamb Waves ◽  
Impact Damage ◽  
Damage Index ◽  
Lead Zirconate ◽  
Low Velocity Impact ◽  
Stiffened Panel ◽  
Low Velocity ◽  
Composite Stiffened Panel ◽  
Index Comparison

Various damage index (DI) algorithms of detecting changes such as a loosen bolt and a delamination development in a composite structure were examined using ultrasonic Lamb waves generated by embedded piezoelectric active sensors. The DI is a single value that is a function of response signal’s attenuation due to any damage or changes in a structure. Various DI algorithms such as active damage interrogation (ADI), time domain root men square (RMS), short time Fourier Transform (STFT) and time reversal (TR) were discussed. For experimental validation, a composite stiffened panel was used, and loosen bolt damage and low-velocity- impact damage were tested. In order to pitch and catch Lamb waves, surface mounted PZTs (lead zirconate titanate) were used. According to the DI algorithms, appropriate ultrasonic guided Lamb waves were selected for actuators. Each set of DI algorithm and drive signal showed different characteristics to detect the damage.

scholarly journals Non-Contact Ultrasonic Inspection of Impact Damage in Composite Laminates by Visualization of Lamb wave Propagation

2018 ◽  
Vol 9 (1) ◽  
pp. 46 ◽  
Author(s):  
Nobuyuki Toyama ◽  
Jiaxing Ye ◽  
Wataru Kokuyama ◽  
Shigeki Yashiro
Keyword(s):  
Wave Propagation ◽  
Lamb Wave ◽  
Impact Damage ◽  
Ultrasonic Transducer ◽  
Ultrasonic Inspection ◽  
Laser Doppler Vibrometer ◽  
Low Velocity Impact ◽  
Signal Averaging ◽  
Cfrp Laminates ◽  
Lamb Wave Propagation

This study demonstrates a rapid non-contact ultrasonic inspection technique by visualization of Lamb wave propagation for detecting impact damage in carbon fiber reinforced polymer (CFRP) laminates. We have developed an optimized laser ultrasonic imaging system, which consists of a rapid pulsed laser scanning unit for ultrasonic generation and a laser Doppler vibrometer (LDV) unit for ultrasonic reception. CFRP laminates were subjected to low-velocity impact to introduce barely visible impact damage. In order to improve the signal-to-noise ratio of the detected ultrasonic signal, retroreflective tape and a signal averaging process were used. We thus successfully visualized the propagation of the pulsed Lamb A0 mode in the CFRP laminates without contact. Interactions between the Lamb waves and impact damage were clearly observed and the damage was easily detected through the change in wave propagation. Furthermore, we demonstrated that the damage could be rapidly detected without signal averaging. This method has significant advantages in detecting damage compared to the conventional method using a contact resonant ultrasonic transducer due to the absence of the ringing phenomenon when using the LDV.

scholarly journals Analysis of Low-Velocity Impact Resistance of Carbon Fiber Reinforced Polymer Composites Based on the Content of Incorporated Graphite Fluoride

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 187 ◽  
Author(s):  
Jing Leng ◽  
Tianzi Guo ◽  
Meng Yang ◽  
Zeshi Guo ◽  
Zhengqin Fang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Impact Resistance ◽  
Fiber Reinforced Polymer ◽  
Low Velocity Impact ◽  
Absorbed Energy ◽  
Low Velocity ◽  
Velocity Impact ◽  
Cfrp Laminates ◽  
Graphite Fluoride ◽  
Reinforced Polymer

As a graphite derivative, graphite fluoride (GrF) has a remarkable fracture toughness improvement effect on epoxy materials. The fracture toughness variation of the epoxy could exert an influence on the low velocity impact resistance of the corresponding carbon fiber reinforced polymer (CFRP) composite. Therefore, the dependence of the low velocity impact resistance of the incorporated CFRP on the GrF content is worth analyzing. Here, different contents of GrF were applied to incorporate CFRP laminates and planned to find the optimal GrF content, in turn leading to the best impact resistance. Using a drop-weight impact test, the load vs. time curves and load vs. displacement curves were obtained. The incipient damage loads and maximum loads of various GrF contents of the samples were compared carefully. The absorbed energies during the impact process were calculated. The trend of absorbed energy decreased up to the 1 wt% sample, then increased significantly with the rise of GrF content. This deflection behavior can be explained by the combination of crack pinning, crack deflection and crack propagation, due to the rise in GrF content. Through the ultrasonic C-scan evaluation, the delamination areas of different GrF content of samples were measured. The trend of delamination area variation was accordant with the trend of absorbed energy variation. This presents a demonstration of the correlation between the absorbed energy and the damage level. The SEM images of the fracture surfaces were analyzed for the deflection behavior of the fracture toughness with various GrF contents. The plot of residual compression strength versus GrF content further indicated the 1 wt% was the optimal content at which the incorporated GrF endowed the most impact-resistant property to the CFRP laminates.

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