Title: ENGINEERING AND INSPECTION OF BARELY VISIBLE IMPACT DAMAGE IN COMPOSITE LAMINATES WITH COATINGS
Authors: Corey R. Kondash, Mike H. Nickell, Charles F. Buynak
Abstract: The ability to nondestructively assess damage in composite aircraft structure is critical for maintaining airworthiness and is often accomplished by ultrasonic techniques. Currently, certain thick coatings must be removed before the underlying structure can be evaluated for damage in this way. These removal, nondestructive inspection (NDI), and coating restoration processes are extremely costly and time intensive, affecting aircraft operational costs and availability. The aim of this work was to fabricate graphite/epoxy composite laminates with barely visible impact damage (BVID) ranging from approximately 0.635 cm - 3.175 cm (0.25 in - 1.25 in) diameter, to support an Air Force Research Laboratory effort to identify improved NDI techniques. BVID was successfully induced into pristine laminates using a drop-weight impactor per ASTM D7136 with some modifications, including fiberglass/epoxy material placed behind the laminates during impacting. Laminates were evaluated via ultrasonic inspection before and after impacting, and the measured damage sizes were correlated to impact energy and laminate thickness at the impact site. These data were used to develop an equation to predict impact energy required to achieve desired BVID in future tests. The impacted laminates then had various coatings applied and were evaluated via multiple emerging NDI techniques to determine feasibility of inspecting BVID through coatings.
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Conference: SAMPE 2023
Publication Date: 2023/04/17
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