Advanced Algorithms to Enhance Signal to Noise Ratio of Peel Ply at the Bondline of Out-of-Autoclave Composite Assemblies

Advanced algorithms were developed to improve the signal to noise ratio between constituents of similar acoustic impedance in bonded out-of-autoclave carbon fiber reinforced polymer assemblies. The assemblies consist of a precured resin infused out-of-autoclave 3D woven fabric preform bonded to a pre-cured out-of-autoclave prepreg fabric substrate. Conventional ultrasonic nondestructive testing techniques and analysis software cannot consistently achieve signal to noise ratios that meet quantifiable rejection thresholds of accurately sized peel ply inserts at the bonded interface To demonstrate the approach, ultrasonic pulse echo with full waveform capture was used to inspect a reference standard with peel ply inserts placed between the film adhesive and the 3D woven fabric preform. The ultrasonic signal was produced by a multi-element array transducer, utilizing a customary shoe and water bubbler. Waveform post-acquisition analysis with post processing software was used to analyze and enhance the signal response between the peel ply and the bondline resulting in the final algorithm. To verify the results, the signal to noise ratio of each insert was calculated for both the raw and processed data. As the measure of detectability, the method relies on principles of statistical measurement to provide an industry standard signal to noise response of3:1.

References
  • Askari, Davood, Ghasemi-Nejhad, & Mehrdad N. (2012). Effects of Vertically Aligned Carbon Nanotubes on Shear Performance of Laminated Nanocomposite Bonded Joints. Science and Technology of Advanced Materials, 1-10. doi:10.1088/1468-6996/13/4/045002
  • Gardiner, G. (2011, January 1). Out-of-Autoclave Prepregs: Hype or Revolution. Retrieved July 20, 2016, from compositesworld.com: http://www.compositesworld.com/articles/out-of-autoclave-prepregs-hype-orrevolution
  • M.D. Banea, L. d. (2009). Adhesively Bonded Joints in Composite Materials: an Overview. Proc. I Mech Eng L-J Mater, 223(1), 1-18. doi:10.1243/14644207JMDA219
  • Sloan, J. (2015, June 1). Out of Autoclave Processing: <1% void content. Retrieved July 21, 2016, from CompositesWorld: http://www.compositesworld.com/articles/out-of-autoclave-processing-1-void-content
  • Material Sound Velocities. (2016). Retrieved November 15, 2016, from Olympus-ims: http://www.olympus-ims.com/en/ndt-tutorials/thickness-gage/appendices-velocities/
  • Metals and Alloys — Densities. (2016). Retrieved November 15, 2016, from engineeringtoolbox.com: http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html
  • Air Density and Specific Weight. (2016). Retrieved November 15, 2016, from engineeringtoolbox.com: http://www.engineeringtoolbox.com/air-density-specific-weight-d_600.html
  • Performance Composite Mechanical Properties. (2016). Retrieved November 17, 2016, from Performance Composites Ltd: http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.asp
  • Nylons (Polyamide) Properties. (2016). Retrieved November 17, 2016, from British Plastics Federation: http://www.bpf.co.uk/plastipedia/polymers/polyamides.aspx
  • ASTM Standard E1495M. (2012). Standard Guide for Acousto-Ultrasonic Assessment of Composites, Laminates, and Bonded Joints. West Conshohocken, PA: ASTM International. doi:10.1520/E1495-12, www.astm.org
  • ASTM Standard D4762. (2011). Standard Guide for Testing Polymer Matrix Composite Materials. West Conshohocken, PA: ASTM International. doi: 10.1520/D4762-11A, www.astm.org
  • MIL-HDBK-787, Military Standardization Handbook: Nondestructive Test Methods of Composite Materials – Ultrasonics. Department of Defense. Washington, DC: US Department of the Army, April 1, 1988.
  • Signal to Noise Ratio. (2001-2016). Retrieved July 21, 2016, from NDT-ed: https://www.ndeed. org/EducationResources/CommunityCollege/Ultrasonics/Physics/signaltonoise.php
  • I.S. Floros, Tserpes, K. T., & Lobel, T. (2015, April 1). Mode-I, Mode-II and Mixed Mode I+II Fracture Behavior of Composite Bonded Joints: Experimental Characterization and Numerical Simulation. Elsevier, 459-468. doi:10.1016/j.compositesb.2015.04.006
  • Thompson, Bruce R. T. G. (1983, July 5). A Model Relating Ultrasonic Scattering Measurements Through Liquid-Solid Surfaces to Unbound Medium Scattering Amplitudes. Ames Laboratory Publications, pp. 1279-1290. doi:0001-4966/83/101279-125
  • ASTM Standard E2580. (2012). Standard Practice for Ultrasonic Testing of Flat Panel Composites and Sandwich Core Materials Used in Aerospace Applications. West Conshohocken, PA: ASTM International. doi:10.1520/E2580-12, www.astm.org
  • Workman, Gary L. Nondestructive Testing Handbook, third edition: Vol. 10, Ultrasonic Testing. Patrick O. Moore, ed. Chap. 10. Columbus, OH: American Society for Nondestructive Testing (2012).
Metrics
Usage Shares
Total Views
35 Page Views
Total Shares
0 Tweets
35
0 PDF Downloads
0
0 Facebook Shares
Total Usage
35