Co-authors​ :

 Javane KARAMI (BELGIUM), Kalliopi-Artemi KALTEREMIDOU (BELGIUM), Dimitrios AGGELIS , Danny VAN HEMELRIJCK  

Composite materials are widely used in various industries due to their great properties like high strength to weight ratio. This class of materials experience different damage mechanisms during their service life like matrix micro-cracking, fiber/matrix debonding, fiber pull-out, fiber breakage as well as delamination [1]. Among the mentioned mechanisms, delamination is one of the most detrimental ones since the crack cannot be easily observed while it causes severe decrease in the overall stiffness of composite components. In practice, delamination occurs under mixed mode loading and accordingly, it is primarily required to understand the delamination behavior under simpler loading scenarios (like pure mode I and II) to consequently comprehend the mixed mode delamination behavior. The pure mode I delamination of the considered material (thermoplastic reinforced with unidirectional carbon fibers) has already been experimentally studied in a previous work of the same authors [2]. It is worth mentioning that thermoplastics are becoming more and more of interest because of their advantages like recyclability, damage tolerance and weldability to name a few. As a continuation of the work [2], the pure mode II delamination using an End Notched Flexure (ENF) configuration is considered in this study and based on ASTM D7905. During the tests, non-destructive techniques like Acoustic Emission (AE) and 3D Digital Image Correlation (DIC) were applied. Regarding the first method, two piezoelectric sensors (in this case, Pico sensors) were mounted on the test specimens to capture the elastic waves generated during loading and due to the initiation and propagation of different damage mechanisms. In other words, AE was used to monitor the intrigued damage mechanisms by looking at the variations in the acoustic wave parameters. As for the DIC method, it is an optical technique which enables the monitoring of the crack length, as well as the developed strain and displacement fields on the specimen side as loading takes place. It is worth mentioning that the number of AE studies related to mode II delamination in composite materials is very limited. More importantly, to the best of the authors’ knowledge, there has been no AE study on delamination using the concerned material. Therefore, AE can provide new insights to the fracture behavior of the material and in turn, can enable more reliable applications of the material in aircraft structures and other structural engineering components.