Chapter 11 Real-Time Visualization of Damage Progression Inside GFRCs via High-Speed X-Ray PCI Technique Jinling Gao, Nesredin Kedir, Cody Kirk, Julio Hernandez, Xuedong Zhai, Junyu Wang, Tyler Tallman, Kamel Fezzaa, and Weinong Chen Abstract Insight into damage progression within glass fiber reinforced composites (GFRCs) contributes to understanding failure of composites by interaction of various damage modes, developing physics-based canonical theoretical models, and finally manufacturing desired compositions. In this work, dynamic singe-edge notched bending (DSENB) experiments were performed on a modified Kolsky compression bar, impacting the notched composite beam onto an indenter mounted in front of a load cell. The high-speed X-ray phase-contrast imaging (PCI) technique was used to penetrate the opaque composite and capture in real time the detailed damage initiation and evolution inside the GFRC. Experimental results were compared with those obtained by optical imaging technique, revealing high-speed X-ray PCI technique was able to characterize the inner layers of composite and capture the damage progression among multiple composite layers. Keywords GFRC · Dynamic loading · Damage evolution · High-speed X-ray PCI technique 11.1 Introduction GFRC has wide applications as structural materials in helmets, vehicle armor, truck box, and military vehicle hulls. This material possesses excellent impact resistance compared with the composites reinforced by other engineering fibers, such as Kevlar®,Dyneema®, and Zylon. Simultaneously, it has higher toughness than carbon fiber reinforced composites [1–2]. One major drawback of such composite is its susceptibility to damage caused by foreign object impact, which induces debonding of individual plies, stiffness degradation, and finally catastrophic failure of the complete composite structure [2]. Current damage assessment techniques for fiber reinforced composites (FRCs) are mainly through insertion of a sensor inside the composite specimen [3] or non-destructive techniques [4–7]. When a small-diameter sensor is embedded into the composite, additional defects might be introduced which will easily alter the original attributes of cracks or damage the composite being investigated. Acoustic emission [5] is an effective method for inspection analysis on the composites, using an array of highly sensitive piezoelectrics to detect the stress waves spreading from the defects inside the materials, such as matrix microcracking, fiber-matrix debonding, localized delamination, or fiber pullout and breakage. However, such technique has difficulty in providing quantitative crack size information. On the other hand, radiographic inspection techniques [6–7] such as X-rays are able to visualize the internal features within solid objects and obtain digital information for damage tracking. J. Gao ( ) · C. Kirk · J. Hernandez · X. Zhai · J. Wang · T. Tallman School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN, USA N. Kedir School of Materials Engineering, Purdue University, West Lafayette, IN, USA e-mail: nkedir@purdue.edu; wchen@purdue.edu K. Fezzaa Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA W. Chen School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN, USA School of Materials Engineering, Purdue University, West Lafayette, IN, USA © The Society for Experimental Mechanics, Inc. 2021 S. Xia et al. (eds.), Fracture, Fatigue, Failure and Damage Evolution, Volume 3, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-60959-7_11 69
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