The Wrinkles Characterization in GFRP Composites by Infrared Active Thermography

Abstract

An experimental study has been carried out to assess the effectiveness of infrared thermography in wrinkle detection in composite GFRP (Glass Fiber Reinforced Plastic) structures by infrared active thermography. Wrinkles in composite GFRP plates with different weave patterns (twill and satin) have been manufactured with the use of the vacuum bagging method. The different localization of defects in laminates has been taken into account. Transmission and reflection measurement techniques of active thermography have been verified and compared. The section of a turbine blade with a vertical axis of rotation containing post-manufacturing wrinkles has been prepared to verify active thermography measurement techniques in the real structure. In the turbine blade section, the influence of a gelcoat surface on the effectiveness of thermography damage detection has also been taken into account. Straightforward thermal parameters applied in structural health monitoring systems allow an effective damage detection method to be built. The transmission IRT setup allows not only for damage detection and localization in composite structures but also for accurate damage identification. The reflection IRT setup is convenient for damage detection systems coupled with nondestructive testing software. In considered cases, the type of fabric weave has negligible influence on the quality of damage detection results.

Evaluation and Defect Detection in L-Shaped GFRP Laminates by Infrared Thermography

“…This is particularly important for curved samples. Our previous studies [7] demonstrated the effectiveness of thermography in detecting wrinkles in flat glass laminate structures and curved thin-walled structures, such as wind turbine blades. The results of thermography studies for reflection and transmission techniques were the subject of much discussion in those studies.…”

“…in the form of fiber waviness and wrinkles in laminates, ultrasonic inspection [5,38], eddy current method [39], and infrared thermography [7] are used.…”

“…The reflection position of the halogen lamps was used to generate the heat flux IR camera and halogen lamps are installed on the same side in the reflection techn The IRT setup was installed in the reflection mode to approximate real-operated mon ing system conditions where an operator cannot place an analyzed structure betwee heat source and the IR camera-Figure 5. If there is easy access to both sides of the o the transmission technique is also used in thermographic analysis [7]. In the present work, a non-destructive technique such as active infrared thermography (IRT) is used to investigate the possibility of detecting wrinkles in curved GFRP composite samples.…”

“…The 3D scanning of the sample and the triangular facet mapping of the laminate shape are shown in Figure 4a In the present work, a non-destructive technique such as active infrared thermography (IRT) is used to investigate the possibility of detecting wrinkles in curved GFRP composite samples. The work by Stawiarski et al [7], which focused on the detection of wrinkles in plates and in the turbine blade, demonstrated the effectiveness of IRT in such analyses. Active thermography is a real-time, full-field detection method that generally involves the generation and propagation of heat flow into the test object and the detection of thermal responses.…”

“…The IRT setup was installed in the reflection mode to approximate real-operated monitoring system conditions where an operator cannot place an analyzed structure between the heat source and the IR camera-Figure 5. If there is easy access to both sides of the object, the transmission technique is also used in thermographic analysis [7]. The thermographic analyses were conducted in two variants of the L-shaped structure configurations in the experimental setup, i.e., the sample was heated from its convex and concave sides-Figure 5a,b.…”