scholarly journals Influence and Compensation of Temperature Effects for Damage Detection and Localization in Aerospace Composites

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4153
Author(s):  
Guillermo Azuara ◽  
Eduardo Barrera
Keyword(s):  
Guided Waves ◽  
Lamb Waves ◽  
Impact Damage ◽  
Reconstruction Algorithm ◽  
Fiber Reinforced Polymers ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Operational Conditions ◽  
Detection And Localization ◽  
Non Destructive

Structural Health Monitoring (SHM) of Carbon Fiber Reinforced Polymers (CFRP) has become, recently, in a promising methodology for the field of Non-Destructive Inspection (NDI), specially based on Ultrasonic Guided Waves (UGW), particularly Lamb waves using Piezoelectric Transducers (PZT). However, the Environmental and Operational Conditions (EOC) perform an important role on the physical characteristics of the waves, mainly the temperature. Some of these effects are phase shifting, amplitude changes and time of flight (ToF) variations. In this paper, a compensation method for evaluating and compensating the effects of the temperature is carried out, performing a data-driven methodology to calculate the features from a dataset of typical temperature values obtained from a thermoset matrix pristine plate, with a transducer network attached. In addition, the methodology is tested on the same sample after an impact damage is carried out on it, using RAPID (Reconstruction Algorithm for Probabilistic Inspection of Damage) and its geometrical variant (RAPID-G) to calculate the location of the damage.

Ultrasonic C-scan techniques for the evaluation of impact damage in CFRP

2021 ◽  
Vol 63 (2) ◽  
pp. 131-137
Author(s):  
Mário Santos ◽  
Jaime Santos ◽  
Paulo Reis ◽  
Ana Amaro
Keyword(s):  
Composite Structures ◽  
Impact Damage ◽  
Image Resolution ◽  
Fiber Reinforced Polymers ◽  
Carbon Fiber Reinforced Polymers ◽  
Low Frequencies ◽  
Reinforced Polymers ◽  
Contour Defects ◽  
Service Application ◽  
Pulse Echo

Abstract In the present work, different ultrasonic C-scan approaches were used to evaluate Carbon Fiber Reinforced Polymers (CFRP) submitted to impacts of low energy, in order to evaluate their effectiveness for the detection and characterization of small defects. In particular, as to the question how useful could be the air-coupled C-scan approach, using low frequencies, for in-service application. For that goal, several samples with different stacking sequences and thicknesses were impacted with 1.5 and 3 J. Then, ultrasonic C-scan images were produced by immersion pulse-echo (in amplitude and time-of-flight (TOF)) and immersion through-transmission, and also by air-coupling through-transmission. The immersion C-scan images were produced using 5, 10 and 20 MHz probes and the air-coupled C-scan was made using two 400 kHz probes. The obtained images for the considered samples show that all used methods are able to detect the defects and give acceptable information about their size and shape. However, if the way of delamination evolving over thickness is of interest, the images by TOF should be used. As expected, good image resolution with sharp contour defects require high frequencies. Nevertheless, the air-coupled C-scan demonstrated similar capabilities to detect defects, with the advantage that the coupling medium is air, thus widening the range of applications, such as real-time damage monitoring of composite structures. As a disadvantage, the air C-scan system requires high power emission signals, and also great amplification of the received signals, to face the considerable attenuation in the air.

Laser Induced Lamb Wave Generation for Structural Health Monitoring of Carbon Fiber Reinforced Polymers

2015 ◽  
Author(s):  
Ron Sebastian ◽  
Benjamin Kelkel ◽  
Martin Gurka ◽  
Tobias Traub ◽  
Johannes L’huillier
Keyword(s):  
Carbon Fiber ◽  
Health Monitoring ◽  
Lamb Wave ◽  
Acoustic Waves ◽  
Lamb Waves ◽  
Piezoelectric Transducers ◽  
Signal Generation ◽  
Fiber Reinforced Polymers ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers

In this paper we present an innovative concept for the excitation of guided acoustic waves (lamb waves) in carbon fiber reinforced polymers (CFRP). The idea is to add this external signal generation to a passive structural health monitoring system (SHM), using the now active system for nondestructive testing (NDT). The whole system consists of piezoelectric sensors, embedded in the polymer matrix of the monitored component, the external laser in combination with a scanning device for spatial resolved generation of acoustic waves and a signal processing unit for data analysis. Using laser excitation for lamb wave generation helps to overcome several dis-advantages compared to the use of piezoelectric transducers only: The flexibility in repositioning of the excitation area allows for easy compensation of the strong signal attenuation of CFRP with a minimum number of piezoelectric transducers. The variation of laser wavelength in the range of 1024 to 3500 nm in combination with variation in intensity allows for a selective coupling of the acoustic waves either into the matrix or in the C fibers. Using piezoelectric transducers for detection only, omits the need for a large number of high-voltage amplifiers for signal generation. In this contribution we present first results of a systematic investigation of the effective generation of lamb waves in CFRP. In addition to the variation of the wavelength of the laser, the intensity was varied too. A potentially damaging influence of the laser radiation on the CFRP material was investigated.

scholarly journals A Comparison among Different Ways to Investigate Composite Materials with Lock-In Thermography: The Multi-Frequency Approach

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2525
Author(s):  
Ester D’Accardi ◽  
Davide Palumbo ◽  
Umberto Galietti
Keyword(s):  
Low Cost ◽  
Fiber Reinforced Polymers ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Carbon Fiber Reinforced Polymers ◽  
Reinforced Polymers ◽  
Advantages And Disadvantages ◽  
Set Up ◽  
Lock In ◽  
Non Destructive

The main goal of non-destructive testing is the detection of defects early enough to avoid catastrophic failure with particular interest for the inspection of aerospace structures; under this aspect, all methods for fast and reliable inspection deserve special attention. In this sense, active thermography for non-destructive testing enables contactless, fast, remote, and not expensive control of materials and structures. Furthermore, different works have confirmed the potentials of lock-in thermography as a flexible technique for its peculiarity to be performed by means of a low-cost set-up. In this work, a new approach called the multi-frequency via software approach (MFS), based on the superimposition via software of two square waves with two different main excitation frequencies, has been used to inspect a sample in carbon fiber reinforced polymers (CFRP) material with imposed defects of different materials, sizes and depths, by means of lock-in thermography. The advantages and disadvantages of the multi-frequency approach have been highlighted by comparing quantitatively the MFS with the traditional excitation methods (sine and square waves).

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