Monitoring multiple damage mechanisms in crack‐patched structures using optical infrared thermography

Abstract

The ability to understand the overall long‐term damage behaviour of crack patched components is essential to improve methods for the performance prediction. The method of passive infrared thermography comprises great opportunities to support the comprehension of the subsurface damage progress of crack‐patched structures. Quasi‐static and cyclic coupon tests are performed with patched metallic specimens and monitored with qualitative and comparative passive infrared thermography. Different test set‐ups help to differentiate between pure metallic crack growth and adhesive damage on thermal images. Results show that metallic crack growth can be monitored from the patched side, also in combination with local delamination at the patch/metal interface overlaying the crack. Thus, it is possible to evaluate position and size of the different damage types at the same time with a rather simple test set‐up. The information on the degradation progress of the crack patched component under loading conditions can help identify the driving damage mechanism of the particular repair configuration. This knowledge can in return be used in the patch design process.

Integration of eddy current sensors into repair patches for fatigue reinforcement at rivet holes

“…Reference measurements of the crack length are carried out by infrared thermography [41,42] . The thermographic camera ImageIR 8380 S from InfraTec GmbH, Dresden, Germany is used.…”

Curing monitoring of bonded composite patch at constant temperature with electromechanical impedance and system parameters evaluation approach

“…Supposing that a peak magnitude x eq = x 0 appears at the frequency ω = ω 0 and a value x eq = x 1 (somewhat less than the peak magnitude) is at frequency ω = ω 1 (ω 1 < ω 0 ). Then the three system parameters k eq , m eq , c eq can be determined by equations ( 8) and (9):…”

“…Generally, there are two kinds of methods that can be used for assessing the curing condition of the composite repair patch, which are non-destructive testing (NDT) and structural health monitoring (SHM). The NDT techniques, such as acoustic emission [8], infrared thermal imaging [9], and ultrasonic testing [10], are often used for inspecting initial damage inside structures to eliminate the safety hazards. However, these NDT approaches are usually performed off-line, which are difficult to obtain the curing condition of epoxy resin in real-time.…”

Real-Time Life-Cycle Monitoring of Composite Structures Using Piezoelectric-Fiber Hybrid Sensor Network

“…With the increasing demand for the performance of composite structures, many structural health monitoring (SHM) methods are required to be incorporated into life-cycle monitoring plans to obtain higher optimal quality [9]. Accordingly, a number of sensing and measurement technologies have emerged such as optical fiber sensing [10][11][12][13], ultrasonic sensing [14][15][16][17], electromechanical impedance [18][19][20], thermometers [21,22], and pressure transducers [23,24]. According to these sensing technologies, they enable one to follow manufacturing parameters such as the progress of the reaction, the residual stress, the development of the resin complex modulus, and the events during the curing cycle such as gelation and vitrification.…”