Title: ENGINEERING AND INSPECTION OF BARELY VISIBLE IMPACT DAMAGE IN COMPOSITE LAMINATES WITH COATINGS

Authors: Corey R. Kondash, Mike H. Nickell, Charles F. Buynak

DOI: 10.33599/nasampe/s.23.0153

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[1] 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.

References: 1. ASTM Standard D7136-15, 2015, “Standard Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event.” ASTM International, West Conshohocken, PA, 2015, DOI: 10.1520/D7136_D7136M-15, www.astm.org. 2. Forrester, Crystal. “Assessing unseen Damage: F/A-18 Hornet Outer Wing StAtic Testing (HOWSAT) Programme Composite Skin Impact Test Assessment.” Advanced Composites Innovation Conference, Melbourne, Australia, April 2016 3. Williams, J. & Rhodes, D. “Effect of Resin on Impact Damage Tolerance of Graphite/Epoxy Laminates.” in Composite Materials: Testing and Design (Sixth Conference), ed. Daniel, I., (West Conshohocken, PA: ASTM International, 1982), 450–480. 4. Bibo, G. & Hogg, P. “The Role of Reinforcement Architecture on Impact Damage Mechanisms and Post-Impact Compression Behaviour.” Journal of Materials Science (1996); 31:1115–37. 5. Greenhalgh, Emile. Failure Analysis and Fractography of Polymer Composites, Cambridge, UK: Woodhead, 2009. 6. Boll, D., Bascom, W., Widner, J. & Murri W. “A Microscopy Study of Impact Damage of Epoxy-Matrix Carbon-Fibre Composites.” Journal of Materials Science (1986); 21:2667–77. 7. Sjogren, A., Krasnikovs, A. & Varna, J. “Experimental Determination of Elastic Properties of Impact Damage in Carbon Fibre/Epoxy Laminates.” Composites – Part A: Applied Science And Manufacturing (2001); 32:1237–42. 8. Davies, G. & Olsson, R. “Impact on Composite Structures.” The Aeronautical Journal (2004); 108:541-563 9. Shyr, T. & Pan Y. “Impact Resistance and Damage Characteristics of Composite Laminates.” Composite Structures (2003); 62:193–203. 10. James, R., Giurgiutiu, V. & Flores, M. “Challenges of Generating Controlled One-Inch Impact Damage in Thick CFRP Composites.” American Institute of Aeronautics and Astronautics (2020); DOI: 10.2514/6.2020-0723

Conference: SAMPE 2023

Publication Date: 2023/04/17

SKU: TP23-0000000153

Pages: 15

Price: $30.00