Continuous debonding monitoring of a patch repaired helicopter stabilizer: Damage assessment and analysis

Abstract

The present work focuses on the structural health monitoring of an aluminium vertical helicopter stabiliser with a pre-introduced crack which was repaired with an adhesively bonded composite patch. The structure was monitored under bending fatigue and its performance was evaluated with Lamb waves, lock-in thermography and ultrasonic testing. Outlier analysis of Lamb waves captured the onset and progress of the damage in the form of patch debonding, enabling the identification of five damage-severity regions. Principal component analysis showed distinctive clusters that corresponded to different damage levels while the application of principal curves on the selected features proved to be an additional damage detection index. Amplitude and phase lock-in images accurately captured the onset and evolution of the damage in the form of patch debonding and honeycomb/skin debonding in agreement with the damage indices obtained from Lamb waves. C-scan further validated the damage mechanisms that were captured by the other methods.

Tensile and flexural damage response of symmetric angle‐ply carbon fiber‐reinforced epoxy laminates: Non‐linear response and effects of thickness and ply‐stacking sequence

“…The demand for advanced composite structures in the modern industry is constantly growing as these materials offer many advantages compared to more conventional ones, especially in applications where high strength and stiffness to weight ratios are required. Thus, high performance composites are used widely in the fabrication of aircraft, automotive and marine structures . For example, new commercial aircrafts such as Boeing 787 and Airbus 350 XWB are the first commercial aircrafts to feature composites in fuselage primary structures .…”

Location of delaminations in curved laminated panels

“…One of the most effective statistical measure is correlation coefficient [16]. It is one of the most often used both in laboratory experiments [17,18,19] and real structures applications [20,21,22]. Delaminations in composite materials are one of the most danger failure mode results typically from impact damage or manufacturing imperfections.…”

On the fatigue response of a bonded repaired aerospace composite using thermography

“…In a later study of the team, Grammatikos et al [15], the thermomechanical coupling observed in bonded repaired composites was studied in comparison with both acoustic emission signals and electrical measurements. More recently, the same principle was used in combination with Lamb waves technique, to study the bonded repair integrity of a patch repaired real helicopter wing by AgustaWestland (SW-4) [25].…”

“…body (paint in this work ε = 0.97-1), ensures for optimum recording data and hence facilitates thermographic analysis [14,15,25,51].…”

“…1) has been widely employed in the past in various modes to characterize and analyse the response of materials during cyclic mechanical loading. Thermomechanical coupling by LT or the so called Thermoelastic Stress Analysis (TSA) [3,8,15,16,[22][23][24][25], has been used to construct stress maps for both composite and metal materials under cyclic mechanical loading. Stress maps allow for the determination of the location of damage initiation and its subsequent evolution.…”