Infrared thermography, ultrasound C-scan and microscope for non-destructive and destructive evaluation of 3D carbon fiber materials: a comparative study

Abstract

3D Carbon fiber polymer matrix composites (3D CF PMCs) are increasingly used for aircraft construction due to their exceptional stiffness and strength-to-mass ratios. However, defects are common in the 3D combining areas and are challenging to inspect. In this paper, Stitching is used to decrease these defects, but causes some new types of defects. Infrared NDT (non-destructive testing) and ultrasound NDT are used. In particular, a micro-laser line thermography technique (micro-LLT) and a micro-laser spot thermography (micro-LST) with locked-in technique are used to detect the micro-defects. In addition, a comparative study is conducted by using pulsed thermography (PT), vibrothermography (VT). In order to confirm the types of the defects, microscopic inspection is carried out before NDT work, after sectioning and polishing a small part of the sample.

Pulsed micro-laser line thermography on submillimeter porosity in carbon fiber reinforced polymer composites: experimental and numerical analyses for the capability of detection

“…However, these techniques cannot detect submillimeter porosity because the distance between the specimen and the camera is usually small (approximately 4.5 cm) when using a microlens, which is difficult for the experimental configurations. Flying spot laser thermography used to detect the subsurface submillimeter flaws in previous composites work was reported [1,2]. However, the results revealed that the technique cannot work on micro-sized flaws.…”

“…The authors proposed micro-laser line thermography (pulsed micro-LLT) [1], which was verified to work for subsurface submillimeter flaws in composites [2]. In this article, pulsed micro-LLT was used to detect the subsurface submillimeter porosities in a 3D preformed CFRP specimen for the evaluation of detection capabilities.…”

“…Large-sized porosities in composites can be detected using classical IRT techniques including pulsed thermography and lock-in thermography [1,2]. However, these techniques cannot detect submillimeter porosity because the distance between the specimen and the camera is usually small (approximately 4.5 cm) when using a microlens, which is difficult for the experimental configurations.…”

“…However, the results revealed that the technique cannot work on micro-sized flaws. The authors proposed a new micro-laser line thermography (micro-LLT) technique [1], which was verified to be suitable for subface submillimeter flaws in composites [2].…”

Comparative study of microlaser excitation thermography and microultrasonic excitation thermography on submillimeter porosity in carbon fiber reinforced polymer composites

“…1 However, it may cause new types of flaws, especially submillimeter flaws. 2,3 Microscopic inspection is the most often used technique for identifying the submillimeter flaws, but it is timeconsuming and destructive. 2,3 Therefore, nondestructive testing (NDT) of materials is significant and increasingly used nowadays.…”