Non-Destructive Testing of Composites by Ultrasound, Local Defect Resonance and Thermography

Abstract

E.V.); Joost.Segers@UGent.be (J.S.); Saeid.Hedayatrasa@UGent.be (S.H.); Wim.VanPaepegem@UGent.be (W.V.P.) 2 SIM Program M3 DETECT-IV, Technologiepark-Zwijnaarde 935, B-9052 Zwijnaarde, BelgiumAbstract: Different non-destructive testing techniques have been evaluated for detecting and assessing damage in carbon fiber reinforced plastics: (i) ultrasonic C-scan, (ii) local defect resonance of front/back surface and (iii) lock-in infrared thermography in reflection. Both artificial defects (flat bottom holes and inserts) and impact damage (barely visible impact damage) have been considered. The ultrasonic C-scans in reflection shows good performance in detecting the defects and in assessing actual defect parameters (e.g., size and depth), but it requires long scanning procedures and water coupling. The local defect resonance technique shows acceptable defect detectability, but has difficulty in extracting actual defect parameters without a priori knowledge. The thermographic inspection is by far the fastest technique, and shows good detectability of shallow defects (depth < 2 mm). Lateral sizing of shallow damage is also possible. The inspection of deeper defects (depth > 3-4 mm) in reflection is problematic and requires advanced post-processing approaches in order to improve the defect contrast to detectable limits.

A Defect Image Enhancement Approach for Detection of Defective Area in CFRPs Through Local Defect Resonance

“…Figs. 8, 9, 10 and 11 show the results of FBD [15], PSD [13] and proposed methods M#1 and M#2 respectively. In these Figs., for better visualization of deeper defects, the effects of the first defect, the first two defects, and the first three defects are masked respectively.…”

“…Frequency band data (FBD) is one of the most common FFT-based LDR data processing methods [15], which is known and used as a data reduction technique but can also be useful for defect detection purpose through averaging of frequency response functions (FRF)s. For each scan point in the location ( , ) of the specimen, this method computes the mean of total vibration amplitude as below, where ∆ is the frequency resolution of the LDR data, and also 1 , 2 are the lower and upper frequency bands which is within the frequency band under investigation. ( , , ) is the out-of-plane velocity amplitude and ( ) is the voltage amplitude of excitation signal produced by piezoelectric.…”

Nondestructive health monitoring techniques for composite materials: A review

“…65 Ultrasonic C-scan estimated the depth of the flat bottom hole as 1.95 mm for a measured hole depth of 2.06 mm in carbon fiber-reinforced composites. 66 The advantages of ultrasonic testing are that it is sensitive to both surface and subsurface damage. The thickness of the composite can be measured using this technique.…”

“…It can detect shallow defects of less than 2 mm and also lateral size estimation is also possible in CFRP composites. 66 A neural approach was used for the automatic analysis of the thermal image sequence for the detection of internal defects in composite materials. A neural network was trained to extract the information related to internal defects (holes, impact damage, and knife cuts) in the composites.…”

A Novel Infrared Thermography Sensing Approach for Rapid, Quantitative Assessment of Damage in Aircraft Composites

“…Impact damage produced at different impact energies has been successfully detected using eddy current pulsed thermography (ECPT) [26]. There are several studies dealing with detection of impact damage with lock-in thermography (LT) and also the reconstruction of the evolution of impact damage in-depth [27][28][29][30]. Benchmarking of thermographic results is commonly based on ultrasonic C-scan techniques [31].…”