In this research, the through-transmission ultrasonic (TTU) Acoustography non-destructive evaluation (NDE) method was employed to detect foreign object inclusion (FOI) defects embedded in carbon fiber epoxy composite laminates.
The study employed three different test specimen with varied size FOI defects embedded at varying depth within the composite laminates. For validation, Acoustography results were compared with conventional immersion TTU and infrared thermography (IRT) methods. Also, quantitative measurements based on Signal-to-Noise Ratio (SNR), defect
sizing, and inspection times were carried out to compare and correlate between different NDE methods that were
applied. The Acoustography method, operating at 5MHz, was easily able to detect all FOIs defect and was also able to resolve
two Teflon defects placed side by side (separation = 1.5 mm) at different layers within the composite test panels. SNR measurements for Acoustography were more than 6:1 and were in good correlation with TTU UT and IRT results.
The defect sizing ability of TTU Acoustography for FOIs defect in graphite epoxy composite laminates were also in strong correlation with the TTU UT and IRT techniques. Finally, TTU Acoustography inspection time was about 1 minute to scan 300 x 300 mm2 (11.81 x 11.81 inch2) area which was faster compared to conventional TTU C-Scan, and IRT techniques. This is a very significant finding because Acoustography is being developed as a faster, more
efficient, and affordable alternative to traditional ultrasonic inspection systems for composites.
 Chu, T. P., Poudel, A., and Filip, P., 2012, "C/C Composite Brake Disk Non-Destructive Evaluation by IR Thermography," Proc. SPIE: Thermosense - Thermal Infrared Applications XXXIV, Vol. 8354, Baltimore, MD.
 Chu, T. P., Don, J., Pan , Y., and Poudel, A., 2012, "Defect characterization in commercial Carbon-Carbon
composites " World Journal of Engineering, Vol. 9(6), pp. 481-486.
 Poudel, A., and Chu, T. P., 2012, "Intelligent Nondestructive Testing Expert System for Aircraft
Carbon/Carbon Composite Brakes Using Infrared Thermography and Air-coupled Ultrasound," Materials Evaluation, Vol. 70(10), pp. 1219-1229.
 Poudel, A., Strycek, J., and Chu, T. P., 2013, "Air-Coupled Ultrasonic Testing of Carbon/Carbon Composite Aircraft Brake Disks," Materials Evaluation, Vol. 71(8), pp. 987-994.
 Poudel, A., Sandhu, J. S., Chu, T. P., and Pergantis, C., 2014 "Porosity Measurement in Carbon Fiber Epoxy Laminates by Using Acoustography," Proc. 23rd Annual Research Symposium and Spring Conference,
 Matzkanin, G. A., and Yolken, H. T., 2008, "Techniques for the Nondestructive Evaluation of Polymer Matrix Composites," The AMMTIAC Quarterly, 2(4), pp. 3-7.
 Sandhu, J. S., Wang, H. H., and Popek, W. J., 1996, "Acoustography for Rapid Ultrasonic Inspection of Composites," Proc. SPIE: Nondestructive Evaluation of Materials and Composites, Vol. 2944, pp. 117-124.
 Sandhu, J. S., Wang, H. H., Popek, W. J., and Sincebaugh, P., 1999, "Acoustography: A Side-by-Side
Comparison With Conventional Ultrasonic Scanning," Proc. SPIE: Nondestructive Evaluation of Aging Materials and Composites III, Vol. 3585, pp. 163-172.
 Sandhu, J. S., Wang, H. H., Popek, W., and Sincebaugh, P. J., 2001, "Acoustography: It Could Be A Practical
Ultrasonic NDE Tool For Composites," Proc. SPIE: Nondestructive Evaluation of Materials and Composites V, Vol. 4336, pp. 129-134.
 Sandhu, J. S., Wang, H. H., Sonpatki, M. M., and Popek, W. J., 2003, "Real-time full-field ultrasonic inspection of composites using acoustography," Proc. SPIE: Nondestructive Evaluation and Health Monitoring of Aerospace Materials and Composites II, Vol. 5046, pp. 99-104.
 Sandhu, J. S., 1987, "Non-Coherent frequency source and sector scanning apparatus for ultrasonic imaging system using a liquid crystal detector cell," U. S. P. Office, ed.U.S.A.
 Sandhu, J. S. and Thomas, R. E., 1988, "Acoustographic Nondestructive Evaluation," Proc. IEEE Ultrasonics
Symposium, Vol.1052, pp. 1053-1056.
 Sandhu, J. S., 1988, "Acoustography: A New Imaging Technique and its Applications to Nondestructive Evaluation," Materials Evaluation, Vol. 46(5), pp. 608-613.
 Sandhu, J. S., 1995, Acoustograhy: Special nondestructive testing methods, Nondestructive Testing Handbook, 2nd Edition, Vol. 9, ASNT, Columbus, OH.
 Poudel, A., Kanneganti, R., Gupta, L., and Chu, T. P., 2013, "Nearest Mean Classifier for Defect Classification in CFRP Panels," Proc. ASNT 22nd Research Symposium and Spring Conference, Memphis, TN.