The adoption of composite materials in aircraft manufacturing for use in structural applications continues to increase but is still relatively new to the industry. Composite components have large development and certification costs in comparison to metallic structures. Traditional methods of nondestructive evaluation (NDE) used for isotropic materials such as metals may not be adequate for composite applications and therefore is a contributing factor to the cost and complexity of developing new structural composites. Additionally, the defects of interest in composite materials are significantly different from metals. Thus, good quality composite reference standards are essential to obtaining reliable and quantifiable NDE results. Ideally, reference standards contain flaws or damage whose NDE indications most closely represent those created by actual flaws/damage. They should also be easy to duplicate and inexpensive to manufacture. NASA’s Advanced Composites Project, working with industry partners, developed a set of composite standards that contain a range of validated defects representing those typically found in aerospace composite materials. This paper will provide an overview of the standards fabricated, the manufacturing plans used to fabricate them, the types of defects included, and validation testing that has performed. Also discussed is an inter-laboratory “round-robin” test that is being performed on these standards. The paper will describe a guidance document being compiled to outline relevant inspection procedures for challenging and critical defects unique to composites where conventional techniques may not be appropriate.
(1) DiMondi, V., 1980, Interlaminar Flaw Propagation Mode II (No. CCM-80-18), DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS.
(2) Waddell, M.C., 2013, Comparison of Artificial Delamination Methods for use with Nondestructive Testing, Summary Report 2013, UNSW@ADFA.
(3) Skartsis, L., Khomami, B. and Kardos, J.L., 1992, Resin flow through fiber beds during composite manufacturing processes. Part II: numerical and experimental studies of Newtonian flow through ideal and actual fiber bed, Polymer Engineering & Science, 32(4), pp.231-239.
(4) Lenoe, E. M., 1970, Effects of voids on mechanical properties of graphite fiber composites, AVCO Corp, Systems Division, Lowell, MA, Prepared for U.S. Air Systems Command, Rpt. AD727236.
(5) Stone, D.E., Clark, B., 1975, Ultrasonic attenuation as a measure of void content in carbon-fibre Reinforced Plastics, Non Destructive Testing, July, pp. 137-145.
(6) Jeong, H., 1997, Effects of Voids on the Mechanical Strength Ultrasonic attenuation of laminated composites, J. Comp Mater., 31 (3), pp. 276-292.
(7) Costa, M.L., 1998, Establishing Structural Composites Processing Parameters from Thermal and Viscosimetric Analyses, MSc thesis, ITA (in Portuguese).
(8) Dodwell, T.J., Butler, R. and Hunt, G.W., 204, Out-of-plane ply wrinkling defects during consolidation over an external radius, Composites Science and Technology, 105, pp.151-159.
(9) Bloom, L.D., Wang, J. and Potter, K.D., 2013, Damage progression and defect sensitivity: An experimental study of representative wrinkles in tension, Composites Part B: Engineering, 45(1), pp.449-458.
(10) Austin, S., 2017, “Advanced Composite Consortium (ACC),” from http://www.nianet.org/advanced-composite-consortium-acc/
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